Toward A More Rational Silkscreen

Today’s complex PCBs are being packed with a boatload of tiny components and are designed to run at ever-increasing speeds. So it certainly comes as no surprise to hear that silkscreen legends are fairly low on the designer’s priorities for consideration. However, the silkscreen’s function—that of aiding the manufacturer and engineer to locate components on the board—remains important.But just how important is it that all components be labeled individually, especially on boards so densely packed? With automated PCBA processes and the widespread use of electronic documentation, certain tradeoffs can now be made, where individual component identification is sacrificed for other types of identifiers. So in the spirit of endeavoring to design the best silkscreen possible, I will review the three types of silkscreen technologies and then advocate a more rational approach to today’s silkscreened boards.Component densities, along with package miniaturization, have become the main culprits in driving technology forward in both the fabrication and assembly processes. This is nowhere more evident than in the major advances in the fabrication realm in which High Density Interconnects (HDI), e.g., blind and buried vias, are now commonplace on most designs. And while certainly not as impressive as the move toward HDI, advances have also been made in how non-conductive ink is applied to create the silkscreen legend.

The board lettering that we call the “silkscreen” originally derived its name from the process of using a stencil to apply ink to the finished raw PCB, in much the same way that lettering or a graphic design is applied to T-shirts. Although this method is still used, new and improved processes are used today that significantly increase both throughput and legibility. Depending on the specific fabrication vendor and the specific make-up (text height and text-pad clearance) of the silkscreen input, one of three methodologies is used to apply the ink to the board:

Корпуса под проекты!!!

Ребята, есть корпуса под проекты (отдам за шоколадку :)), нахожусь в СПб. фото по запросу. Метро Александра Невского или Комендантский. Фото по запросу. Новый неликвид цифровые приставки для TV. Для ускорения связи пишем на Количество ограничено.

Пятиканальный стабилизатор для ЦАПа

Еще один вариант питания ЦАПов представленных на этом сайте, но на LM317 (LM1085). По умолчанию, на схеме указаны напряжения для +5, +9, +16 Вольт, но вы можете пересчитать их под свои нужды. Сами микросхемы стабилизаторов крепятся к алюминиевой пластине снизу печатной платы. Схема и фото готовой платы прилагается.


Плата стабилизаторов для цапа 5ch

Пустая пятиканальная плата стабилизаторов на LM317. Сами микросхемы монтируются на радиатор снизу, параллельно печатной плате. Список необходимых компонентов приложил. Стоимость 300 рублей без учета стоимости доставки.

Плата сетевого фильтра

Плата сетевого фильтра для ЦАП, CD проигрывателя. Есть вход для подключения сетевой кнопки, так же на плате есть место для установки реле G6D Цена платы 300 рублей, без учета стоимости доставки.


About the PCB Panel Separately Ways

About the PCB Panel Separately Ways


Usually, inorder to improve the PCB assembly speed, usually ,ALLPCB to make in panel, espeically for a small size PCB, with much quantity.

Then what is the best way to cut pcb board? Or what is the correct tool to cut PCB material,finally getting a nice straight line? Many engineers will worry about this issue.





Punch cutting /Routing


When a printed circuit board is designed with other shapes or irregular contours besides rectangles, it is relatively quick and economical to use a punching die. The basic punching and cutting operation can be completed by using a puncher, whose cutting edge is neat and the effect is better than using a saw cutting or shearing machine. Sometimes, even punching and punching can be done at the same time. However, when good edge effect or small tolerance is required, punching and chaining do not meet the requirements. In the PCB industry, punching and cutting is generally used to cut paper substrate, but rarely used to cut epoxy glass substrate. Punching and cutting can make the cutting tolerance of printed circuit board within 0.1-o. 2mm. This is common way that ALLPCB use for small PCB.


V cutting


Sawing is another method of cutting the substrate. Although the size tolerance of this method is similar to that of shear (0.3-0.5 RNRN), this method is preferable because the cutting edge is very smooth and neat. This is the most common used by ALLPCB.


In the PCB manufacturing industry, most of the circular saw cutting machines with movable worktable are used. The adjustable speed range of saw blade is 2000-6000r /rnin. But once the cutting speed is set, it cannot be further changed. It is achieved by a heavy pulley with more than one V band.


The diameter of the high-speed steel blade is about 3000rnrn, and it can cut paper steeling materials at the rate of 2000-3000r /rnin with approximately 1.2-1.5teeth per 1cm circumference. For epoxy glass substrate, use a tungsten carbide blade blade. The diamond wheel cuts better. Although it is expensive at the beginning, it is very useful for future work because of its long life and improved edge cutting.






The basic cutting method is suitable for all kinds of substrate, usually no more than 2mm thick. When the cutting board is more than 2mm, the cutting edge will appear rough and untidy, therefore, this method is generally not adopted.


The shear of laminate can be manual or electromechanical, whichever method has common features in operation. Shears usually have a set of adjustable shear blades, as shown in FIG. 10-1. Edge at the bottom of its blade is a rectangle, about 7 ° of the adjustable Angle, cutting length can be up to 1000 mm, longitudinal Angle between two blades usually had better choose in 1 ° — 1. 5 °, between epoxy glass substrate biggest can reach 4 °, the gaps between the two blades cutting edge to be less than 0.25 mm.


The Angle between the two blades is selected according to the thickness of the cutting material. The thicker the material, the greater the Angle required. If the shear Angle is too large or the gap between the two blades is too wide, the sheet will crack when cutting the paper substrate. However, for the epoxy glass substrate, due to the material's certain bending strength, it will deform even if there is no crack. In order to make the floor in the process of shearing edge tidiness, material can be heated in the range of 30-100 ℃.


In order to obtain a clean cut, the board must be firmly pressed down through a spring device to prevent any other unavoidable displacement of the board during shear. In addition, parallax can also lead to tolerance of 0.0.5 RNRN, which should be reduced to the minimum. The accuracy can be improved by using Angle marks.


The shears are capable of handling a variety of sizes and can provide accurate duplicate sizes. Large machines can cut several hundred kilograms of substrate per hour.





About the PCB assembly by ALLPCB

About the PCB assembly by ALLPCB


Printed circuit board assembly has certainly evolved quite a bit during the last few decades. and now more and more PCBmanufacturer offer PCBA service, Also supplyed by ALLPCB. To fully understand just how far we've come, it's important to look back. In today's post, we'll discuss the evolution of PCB assembly from its humble beginnings to where we're headed today.


The first known PCBs were derived from printed wire technology developed in the 1900s. However, it wasn't until after World War II that the printed circuit board as we know it was really created. Thanks to a patent for printed wiring submitted in 1925, we knew the technology involving an insulated surface and an electrical path held promise, particularly for tube radios and gramophones. In 1943, Dr. Paul Eisler created the first printed wiring board that actually worked, paving the way for future iterations of printed circuit board assembly.




In the 1950s, PCBs were single-sided. These boards held the circuitry on one side and the components on the other. Different kinds of resins were used to make these boards more efficient, making them a viable option for communication equipment, weapons, and other industrial developments. During the 1960s, advancements in the plating process allowed for the creation of double-sided circuit boards. These boards allowed for the connection of circuits on each side using one of two different methods: surface-mount technology or through-hole technology. Double-sided circuit board assembly provided greater circuit density. In addition, the advancements in solder mask during this decade allowed PCB assembly services to manufacture these boards more quickly and easily.


By the 1970s, PCB circuitry and spacing had shrunk. This allowed developers to fit more into a small space, which made PCBs an even more in-demand component for a variety of applications. Assembly methods became more efficient, too. And over the next two decades or so, multi-layer printed circuit boards came on the scene. This development was substantial for sectors like electronics, defense, and communications.



Circa now, printed circuit board assembly continues to grow in order to address growing demand. This technology is now used in the aerospace and healthcare fields, among many others. And because PCBs are becoming even smaller and more precise, the possibilities for technological applications are nearly endless. We now rely on PCBs for virtually everything we do on a daily basis, from answering texts and emails to maintaining our home automation system or playing music we love. PCB design and development shows no signs of slowing down — and considering how reliant we are on technology, PCBs will continue to be in high demand for many years to come.

Модуль индикации для аманеро

модуль индикации для amanero

При создании проекта ЦАП-а хотелось получить законченную конструкцию. Так в дополнение к адаптеру для аманеро v1.4 решено было разработать модуль индикации. 

Модуль выводит на экран информацию о текущей частоте дискретизации, используя пины F0-F3 на аманеро. Но стоит отметить, что их функциональность была добавлена только в свежих прошивках аманеро. На китайских клона со старой прошивкой, опция «Enable F0, F1, F2, F3» (включаемая в oemtools) может оказаться нерабочей. Для работы модуля требуется включение F0-F3.

PCB Assembly Manufacturing Documentation with Draftsman

In my numerous years in the electronics industry, we have come a long way. From using tape on mylars for PCB layouts to advanced CAD systems, the industry has moved what can only be described as light years ahead over the last 30 years or so.Gone are the days (thankfully) of a hand drawn schematic which is then translated by someone into physical parts that are connected by hand (even in early layout programs this was true). Netlist? What was one of those in a schematic?

CAD tools have come along way since then, and using an advanced tool such as Altium Designer can be a significant time saver in many tasks that are rarely (if ever) provided as automation tools in other CAD packagesBut I digress.

This is the first of a series of posts where I show how I tell the story of a PCB assembly (PCBA)services to my contract manufacturers.

So; you have completed the design of your PCB (or perhaps multiple printed circuit board projects), you are happy with the layout and you have generated the files necessary to get your latest work of art actually manufactured; but have you?

I have seen a lot of data packs for manufacturing, from indifferent to great to, well, awful to be honest. With the advent of really fine pitch components in surface mount packages amongst other advances, the rules of manufacturing have changed as the older methods simply are not suitable for newer parts and the manufacturing pack needs to provide arguably more guidance than was sufficient in the past.

What type of solder do you wish them to use? What are the reflow profile limits? These are two (of many) very important issues to make sure that the soldering process yields high quality joints. Solder joints are not the only thing to consider, though. As this series of posts will show, it is possible to convey very detailed information in a way that is clear and concise with no room for interpretation.

When you send out your design, you know what you want to have made, but the contract electronics manufacturer does not. They do not understand the design intent, where it will be used (which implies some steps that are not part of the usual CAD tool outputs) or how to test it unless you actually provide that information.

There are different types of packs depending on just what is being manufactured, so I will confine myself to the simplest for this post; the PCB assembly manufacturing pack encapsulated in the rectangle. This view is the assembly hierarchy and not how the outputs are actually generated.

The hierarchy shown is a typical setup for a PCB Assembly manufacturing pack and using the tools in Altium Designer (from 16.1 onward), it is a breeze to actually make a pack that will reduce or eliminate uncertainty for your manufacturer of choice. Is it completely automated? No; every company and every design is different and there is some up front work to do which will be covered in the second article in this series.

Note that the pack shown is for a single assembly and could easily be a child or parent object to other higher or lower assemblies, making it ideally suited for companies with PDM (Product Data Management) / LCM (Life Cycle Management) systems.

Let’s take a quick look at what is here:

The master assembly print. Not everything the manufacturer needs to know is in the electronic outputs (pick and place, BoM); there may well be special instructions, a test procedure to be used and other information. This is often missing from many packs, but it is not difficult to generate as we will see in a future post. This is the master drawing for assembly; everything else is subordinate. In the industries I have worked in, we call this a single source of truth.

The schematic and BoM are standard outputs which generally already exist and we will leave these for now (but I will take a look at how they can better support both internal teams and external manufacturing in a later post).

The electronic PCB design data; there are nuances here that, once more, I will post about later.

The PCB fabrication master; this is, like the assembly master, usually not generated or sent, but all the information for a PCB fabricator to successfully make the bare circuit boards is not contained within the electronic data such as gerbers and ODB++ files. A much closer look at this will be the subject of another post.

A typical fabrication master front sheet from PJS Electronics Limited; there are 3 sheets in all. The Altium MiniPC example project was used to generate this document using the PJS Electronics template.

Test information. It is unfortunately common that the tests to confirm a PCB assembly is working after being assembled is either incomplete or missing.

There are major advantages to using this approach.

With complete information on the printed circuit board assembly, the contract manufacturer can generate a precise quote as they can properly estimate everything required; that means no surprises when a test is suddenly sent to the contract manufacturer who, apart from charging you for the test to be done, may need to put your assembly process on hold until operator time is available. Many contract manufacturers book their lines weeks and months ahead and organize their manpower and equipment accordingly. An incomplete pack can lead to a great deal of grief. Documentation and a single source of truth are key to a quality printed circuit board assembly process.

The PCB fabricator (often a separate company from the assembler) can generate an accurate quote as all the information they need is written down for them (my company template has 26 pre-defined comments for the PCB fabrication print).

Your data management team will adore you.

There is even a standard for these documents; IPC-D-325. By following this standard everyone understands what information is being conveyed.

I implemented this scheme at a company I worked for and a contract electronics assembler told me it was simply the best manufacturing pack they had ever seen. Wouldn’t you like to be able to show that email to your boss come evaluation time?

The bottom line: A complete fabrication pack can save time, money and schedule when done properly and there will be fewer questions and answers (although there should be some questions on a new assembly – no questions from the assembler and fabricator is a very bad sign).

Using Altium Designer can greatly simplify the generation of the extra drawings. There is a certain amount of time to be spent getting the templates right but that is soon amortized by the speed and ease of generating these files later in the process.

Сетевой фильтр для ЦАП

Внимание! На плате присутствует опасное для жизни напряжение! Все работы вы производите на свой страх и риск!

В виду сильных помех в сети и периодического гудения тороидального трансформатора, мне понадобился сетевой фильтр. Представленная мной схема ничего нового собой не представляет, лишь собрана воедино. Здесь CLC фильтр и фильтр Шушурина. Так же на плате есть реле, оно включает выключает цап с Селектора входов I2S для ЦАПа AH-D5, но его можно не устанавливать, а подключить кнопку к J1, подав 220 Вольт на вход J2.  Схему, партлист приложил.

Высококачественный ЦАП AH-D6 версия 2.0

Как показал опыт эксплуатации AH-D5, большинство тактовых генераторов, в частности используемые NZ2520SD(A), не реализуют полного гашения генерации в неактивном режиме (только Z-state выхода). Поэтому в новом устройстве было решено уделить особое внимание полному гашению генерации неактивного клока и возможности полного отключения обоих генераторов при работе в ведомом режиме.

Устройство совместимо с транспортами Bolero (DSD version) или Charleston от Energy Audio без каких-либо дополнительных переходных устройств.

Селектор входов I2S для ЦАПа AH-D5

Собирая данный цап я понимал, что одной китайской аманеры мне точно не хватит. Мне еще нужен как минимум один оптический вход. Посмотрел в сторону готовых конструкций, и, ни одно устройство не понравилось по некоторым причинам. Было принято решение делать свое.

Для двух оптических входов применена AK4113 в master с оптическими приемниками PLR135/T9. В master она работает потому, что воспроизводит звук лишь с телевизора, и не более. Плата китайской аманеры установлена вверх ногами, для получения низкого профиля при монтаже платы. Она работает в slave. Отдельное спасибо Анатолию Wired за схему для подключения одноплатного компьютера beaglebone black. При его применении и условии, что он питается от отдельного источника появляется возможность включать — выключать цап кнопкой без фиксации. На плате предусмотрен разъем для подключения реле, контактами которого можно коммутировать первичную обмотку трансформатора. Если же отказаться от использования, то Q1 нужно заменить перемычкой.

Программирование микросхем AKM для работы в soft mode на базе ATmega88

Доброго времени суток. Полгода назад, в связи с решением проектировать в качестве ВКРБ схему ЦАП+усь, встал вопрос выбора подходящей микросхемы для того, чтобы использовать её в качестве «сердца» разрабатываемого устройства. Поскольку актуальные версии микросхем ЦАП от Sabre являются труднодоступными, как и даташиты на них, было принято решение проектировать на чипах AKM. Субъективно, в моём личном топе они занимают благодарное второе место (приходилось много слушать 4490). Таким образом было принято решение использовать AK4493EQ. Он заметно опережает 4490 по своим характеристикам и несильно уступает 4497 при вшестеро меньшей цене.

Так и подкрался вопрос о проектировании цифровой части (в первую очередь).

Поскольку интернет пестрит огромным количеством готовых конвертеров USB->I2S, в условиях сильной ограниченности по времени решено разрабатывать устройство с поддержкой стандартов Bolero и не изобретать велосипед. Получилось то, что изображено на рисунке.

An Overview of the PCB Assembly Process Steps

In this essay, we will look at the PCB assembly(PCBA) process steps that lead to a completed product. the pricess is also the standard ones that apply to other manufacturers for reference.

  1. Application of solder paste – In automated assembly, a solder stencil is held in place on the board while an applicator applies solder paste in precise amounts exactly where it is needed. The stencil is a thin sheet of metal with holes in it, making sure solder paste is only applied to the parts of the PCB where components will sit. The solder paste is a mix of solder (tiny balls of metal) and flux (a chemical that helps the metal melt and bond to the surface better).

  2. Pick and Place (SMT) – Once the solder is applied, the board moves to the pick and place (PNP) machine. This machine automatically orients the board and places components onto the solder paste using preprogrammed locations. With surface mount technology (SMT), components are soldered only to the surface of the board. Today, the majority of non-connector components are mounted with SMT because PNP machines are extremely fast and accurate.

  3. Reflow soldering – After the components are placed, the board is moved to the reflow oven. The oven gradually heats the board to melt the solder paste to create a permanent connection between components and boards, then cools the board in an equally controlled manner to prevent damage from shock.
  4. Inspection and Quality Assurance – Errors in the previous process can result in components that are not connected, shorts in the board, or misaligned components. Inspections ensures errors and found and corrected as quickly as possible, preventing costly delays. The are several inspection methods, including hands-on inspection by a person, automatic optical inspection that relies on image recognition, and even x-ray inspection to look through components that may block an inspector’s view.

  5. Insert Through-Hole Components – Depending on the board, it may require through-hole technology (THT) components in addition to SMT components. Certain items, such as headers and larger components, are only available in THT. Since the leads for these components are run through holes in the board, the soldering paste can’t be used as it would simply run through the holes without adhering. Instead, THT uses wave soldering. Here a machine creates a wave of solder in a pan which washes over the bottom of the board and solders all the pins on the bottom of the board at once.

  6. Final Inspection and Functional Testing – Once all soldering is completed, the PCB is put through its paces and tested under the normal conditions in which it will operate. This is the most important PCB assembly process step and ensures only quality boards are delivered to the client.

Immersion Goldand Gold Plating

The immersion gold plate and the gold plate are two processes of the most PCB manufacturers.Like ALLPCB,ALLPCB is a topspeed pcb manufacturer in China, specializing in high quality and cheap pcb prototype & production, pcb assembly and smt stencil services online.For the gold plating process, the effect of tin on it is greatly reduced, and the effect of the gold is better; unless the manufacturer insists on the requirements, most manufacturers will choose the gold process!
Under normal circumstances, PCB surface treatment is as follows: gold plating (electroplating gold, immersion gold), silver plating, OSP, spray tin (lead and lead-free), these are mainly for FR-4 or CEM-3 For sheet metal, the paper base material also has a surface treatment method of rosin coating; if the tin-on-iron defect is excluded, the solder paste and other patch manufacturers are excluded from the production and material processing reasons. There are several reasons for this:
1. When printing on the PCB, whether there is oil film on the PAN position, it can block the effect of tinning; this can be verified by the soldering test.
2. Whether the PAN bit is in compliance with the design requirements, that is, whether the pad design is sufficient to ensure the support of the part.
3. Whether the pad is contaminated, this can be obtained by ion contamination test; the aAbove three points are basically the key aspects considered by ALLPCB.
The advantages and disadvantages of several methods of surface treatment are that each has its own strengths and weaknesses! In terms of gold plating, it can make the PCB storage for a long time, and it is less affected by the external environment temperature and humidity (relative to other surface treatments), generally can be stored for about one year; tinned surface treatment is second, OSP again, this Both surface treatments should pay attention to a lot of storage time in ambient temperature and humidity. Under normal circumstances, the surface treatment of sinking silver is a bit different, the price is high, the storage conditions are more demanding, and it needs to be processed with sulfur-free paper packaging! The storage time is about three months.

Printed Circuit Board Introduction & PCB Types

Printed circuit boards (PCBs) are the boards that are used as the base in most electronics – both as a physical support piece and as the wiring area for the surface-mounted and socketed components. PCBs are most commonly made out of fiberglass, composite epoxy, or another composite material.


Want to get fabricaiton price of specilty PCBs such as Flexible PCBs, Flex-rigid PCBs, Aluminum PCBs, Rogers PCBs, etc.? Simply send your Gerber file and requirement on materials and quantity to ALLPCB.


ALLPCB is a topspeed PCB manufacturer. Their capabilities include HDI PCBs, Rigid PCBs, Flex PCBs and Rigid-Flex PCBs. For very sophisticated PCBs, we can go down to 3 mils trace width / spacing. They will give the price shortly. They also offer PCB prototyping service to help you get the right PCB design before full production. Avoiding costly errors can save you thousands over the scope of the project.


All of ALLPCB designers are compliant with ISO9001:2008 quality management systems and our in-house quality control department will verify that your prototype meets both our and your high standards before we send it off to you. Depending on requirements, most prototype PCBs can be done within 4-5 days when you need quality prototyping done fast. What is Printed Circuit Board Most PCBs for simple electronics are simple and composed of only a single layer.


More sophisticated hardware such as computer graphics cards or motherboards can have multiple layers, sometimes up to twelve. Although PCBs are most often associated with computers, they can be found in many other electronic devices, such as TVs, Radios, Digital cameras and Cell phones. In addition to their use in consumer electronics and computers, different types of PCBs are used in a variety of other fields, including:


• Medical devices. Electronics products are now denser and consume less power than previous generations, making it possible to test new and exciting medical technology. Most medical devices use a high-density PCB, which is used to create the smallest and densest design possible. This helps to alleviate some of the unique constraints involved with developing devices for the medical field due to the necessity of small size and light weight. PCBs have found their way into everything from small devices, such as pacemakers, to much larger devices like X-ray equipment or CAT scan machines.


• Industrial machinery. PCBs are commonly used in high-powered industrial machinery. In places where current one-ounce copper PCBs do not fit the requirements, thick copper PCBs can be utilized instead. Examples of situations where thicker copper PCBs would be beneficial include motor controllers, high-current battery chargers and industrial load testers.


• Lighting. As LED-based lighting solutions catch on in popularity because of their low power consumption and high levels of efficiency, so too do aluminum-backed PCBs which are used to make them. These PCBs serve as heat sinks and allow for higher levels of heat transfer than a standard PCB. These same aluminum-backed PCBs form the basis for both high-lumen LED applications and basic lighting solutions.


• Automotive and aerospace industries. Both the automotive and aerospace industries make use of flexible PCBs, which are designed to withstand the high-vibration environments that are common in both fields. Depending on specifications and design, they can also be very lightweight, which is a necessity when manufacturing parts for transportation industries. They are also able to conform to the tight spaces that might be present in these applications, such as inside instrument panels or behind the instrument gauge on a dashboard.


There are several overall types of PCB boards each with their own particular manufacturing specifications, material types and usages: Single-layer PCBs, Double-layer PCBs, Multi-layer PCBs, Rigid PCBs, Flexible PCBs, Rigid-Flex PCBs, High-frequency PCBs, Aluminum-backed PCBs. Single-layer PCBs A single-layer or single-sided PCB is one that is made out of a single layer of base material or substrate.


One side of the base material is coated with a thin layer of metal. Copper is the most common coating due to how well it functions as an electrical conductor. Once the copper base plating is applied, a protective solder mask is usually applied, followed by the last silk-screen to mark out all of the elements on the board. Single-layer PCB Since single-layer/single-sided PCBs only have their various circuits and components soldered onto one side, they are easy to design and manufacture.


This popularity means that they can be purchased at a low-cost, especially for high-volume orders. The low-cost, high volume model means they are commonly used for a variety of applications, including calculators, cameras, radio and stereo equipment, solid state drives, printers and power supplies.


Double-layer PCBs Double-layer or double-sided PCBs have a base material with a thin layer of conductive metal, like copper, applied to both sides of the board. Holes drilled through the board allow circuits on one side of the board to connect to circuits on the other. Double-layer PCB The circuits and components of a double-layer PCB board are usually connected in one of two ways: either utilizing a through-hole or with the use of a surface-mount.


A through-hole connection means that small wires, known as leads, are fed through the holes, with each end of the leads then soldered to the right component. Surface mount PCBs don't utilize wires as connectors. Instead, many small leads are soldered directly to the board, meaning that the board itself is used as a wiring surface for the different components.


This allows circuits to be completed using less space, freeing up space to allow the board to complete more functions, usually at higher speeds and a lighter weight than a through-hole board would allow. Double-sided PCBs are typically used in applications which require an intermediate level of circuit complexity, such as Industrial controls, Power supplies, Instrumentation, HVAC systems, LED lighting, Automotive dashboards, Amplifiers and Vending machines. Multi-layer PCBs Multi-layer PCBs consist of a series of three or more double-layered PCBs.


These boards are then secured together with a specialized glue and sandwiched between pieces of insulation to ensure that excess heat doesn't melt any of the components. Multi-layer PCBs come in a variety of sizes, going as small as four layers or as large as ten or twelve. The largest multi-layer PCB ever built was 50 layers thick. Multi-layer PCB With many layers of printed circuit boards, designers can make very thick, complex designs which are suitable for a broad range of complicated electrical tasks.


Applications where multi-layer PCBs would be beneficial include File servers, Data storage, GPS technology, Satellite systems, Weather analysis and Medical equipment. Rigid PCBs Rigid PCBs are printed circuit boards that are made out of a solid substrate material that prevents the board from twisting.


Possibly the most common example of a rigid PCB is a computer motherboard. The motherboard is a multilayer PCB designed to allocate electricity from the power supply while simultaneously allowing communication between all of the many parts of the computer, such as CPU, GPU and RAM. Rigid PCBs make up perhaps the largest number of PCBs manufactured. These PCBs are used anywhere that there is a need for the PCB itself to be set up in one shape and remain that way for the remainder of the device's lifespan. Rigid PCBs can be anything from a simple single-layer PCB all the way up to an eight or ten-layer multi-layer PCB. Rigid PCB All Rigid PCBs have single-layer, double-layer or multilayer constructions, so they all share the same applications. Flexible PCBs Unlike rigid PCBs, which use unmoving materials such as fiberglass, flexible PCBs are made of materials that can flex and move, such as plastic. Like rigid PCBs, flexible PCBs come in single, double or multilayer formats. As they need to be printed on a flexible material, they tend to cost more for fabrication. Flexible PCB Still, flexible PCBs offer many advantages over rigid PCBs.


The most prominent of these advantages is the fact that they are flexible. This means they can be folded over edges and wrapped around corners. Their flexibility can lead to cost and weight savings since a single flexible PCB can be used to cover areas that might take multiple rigid PCBs. Flexible PCBs can also be used in areas that might be subject to environmental hazards. To do so, they are simply built using materials that might be waterproof, shockproof, corrosion-resistant or resistant to high-temperature oils — an option that traditional rigid PCBs may not have. Flex-rigid PCBs Flex-rigid PCBs combine the best of both worlds when it comes to the two most important overarching types of PCB boards.


Flex-rigid boards consist of multiple layers of flexible PCBs attached to a number of rigid PCB layers. Flex-rigid PCBs have many advantages over just using rigid or flexible PCBs for certain applications. For one, rigid-flex boards have a lower parts count than traditional rigid or flexible boards because the wiring options for both can be combined into a single board. The combination of rigid and flexible boards into a single rigid-flex board also allows for a more streamlined design, reducing the overall board size and package weight.


Flex-rigid PCB Flex-rigid PCBs are most often found in applications where space or weight are prime concerns, including Cell phones, Digital cameras, Pacemakers and Automobiles. High-frequency PCBs High-frequency PCBs refer to a general PCB design element, rather than a type of PCB construction like the previous models. High-frequency PCBs are circuit boards that are designed to transmit signals over one gigahertz.


High-frequency PCB High-frequency PCB materials often include FR4-grade glass-reinforced epoxy laminate, polyphenylene oxide (PPO) resin and Teflon. Teflon is one of the most expensive options available because of its small and stable dielectric constant, small amounts of dielectric loss and overall low water absorption. Many aspects need to be considered when choosing high-frequency PCB board and its corresponding type of PCB connector, including dielectric constant (DK), dissipation, loss and dielectric thickness. The most important of those is the Dk of the material in question.


Materials with high probability for the change of dielectric constant often have changes in impedance, which can disrupt the harmonics that make up a digital signal and cause an overall loss of digital signal integrity — one of the things that high-frequency PCBs are designed to prevent. Other things to consider when choosing the boards and PC connector types to use when designing a high-frequency PCB are: • Dielectric loss (DF), which affects the quality of signal transmission.


A smaller amount of dielectric loss could make a small amount of signal wastage. • Thermal expansion. If the thermal expansion rates of the materials used to build the PCB, such as copper foil, are not the same, then materials could separate from each other due to changes in temperature. • Water absorption. High amounts of water intake will affect the dielectric constant and dielectric loss of PCB, especially if it is used in wet environments. • Other resistances. The materials utilized in the construction of a high-frequency PCB should be rated highly for heat resistance, impact endurance and resistance to hazardous chemicals, as necessary.

PCB repair method for PCB manufacturer.

The PCBA Manufacture repairs PCB boards,The first step is to observe whether the circuit board has been damaged by humans. This is mainly from the following aspects:
1 See if the board is dropped, causing the board corner to be deformed, or the chip on the board being broken or broken. 2 Observe the socket of the chip to see if it is forced to be damaged because there is no special tool.
3 Observe the chip on the circuit board. If it is with a socket, first observe whether the chip is inserted incorrectly. This is mainly to prevent the operator from inserting the wrong position or direction of the chip when repairing the circuit board. If the error is not corrected in time, when the board is energized, the chip may be burned out, causing unnecessary losses.
4 If there is a shorting terminal on the board, observe if the shorting terminal is inserted incorrectly.

The maintenance of the circuit board requires a solid foundation in theory, careful work, and careful observation by the maintainer, sometimes at this step can determine the cause of the problem. The second step is to observe whether the components on the board are burned out. For example, resistors, capacitors, and diodes are not black or smeared. Under normal circumstances, even if the resistance is burnt, its resistance will not change, the performance will not change, and it will not affect the normal use. In this case, a multimeter is needed to assist the measurement. However, if the capacitors and diodes are burnt, their performance will change, and they will not play their due role in the circuit, which will affect the normal operation of the entire circuit. At this time, new components must be replaced. The third step is to observe the integrated circuit on the circuit board, such as 74 series, CPU, coprocessor, AD and other chips, there are no drums, cracks, burnt, black. If this happens, it is basically OK that the chip has been burned out and must be replaced. The fourth step is to observe whether the traces on the circuit board are peeled or burned. The copper hole is not separated from the pad. Step 5: Observe the fuses on the board (including the fuse and the thermistor) to see if the fuse is blown. Sometimes the fuse is too thin and can’t be seen clearly. You can use the auxiliary tool-multimeter to judge whether the fuse is damaged.
The above four cases are the method for the circuit board factory to repair the PCB board, which is basically due to the consequences of excessive current in the circuit. However, the specific cause of the current is too large, it is necessary to analyze the specific problem. But the general idea of ​​finding the problem is to first carefully analyze the schematic diagram of the board, and then find out its superior circuit according to the circuit where the burnt component is located, and derive it step by step, and then rely on some experience accumulated in the work to analyze the easiest. Where the problem occurred, find out the cause of the failure.

Evaluating SMT Assembler's Capabilities

From the point of technology and quality, SMT assembler's capabilities can be found when you go through key elements in the SMT process. This article shares sufficient knowledge in evaluating PCBA quality of a PCB assembler, which allows you to test whether your circuit boards assembled in that factory conform to your required standard.

Key elements in evaluating SMT quality include solder paste printing quality, reflow quality, how to avoid misplacement of components, how to avoid manual placement, capabilities on stencil thickness calculation and modification, size of aperture, up-to-data equipment or instrument. Among these elements, quality control of solder paste printing is the most important one. If solder paste is badly printed, your circuit boards are incontrovertibly in low quality whether components mounting is accurately completed and reflow temperature is suitably modified. After all, non-standard amount of printed solder paste is closely associated with quality of soldering. In terms of other elements, accuracy of surface mounter has already achieved required level and reflow temperature curves have been determined in advance. Few special modifications are needed now that the harm occurred by tin melting temperature and too much heat brought to material is fully understood.

Then come the methods to evaluate and ensure compatibility of solder paste printing quality. Solder paste printing mainly comes in two aspects of capabilities: solder paste quality administration capability and solder paste printing capability.
Solder paste quality administration

High-quality solder paste relies on its brand and freshness degree. For the freshness degree of solder paste, it has to be tracked starting from the time of warming up, jar opening and stirring. Different manufacturers conform to different regulations stipulating that solder paste has to be used up within a certain period of time otherwise it'll get oxidized, leading to insufficient soldering in the process of reflow. Furthermore, significant administration has to be implemented on solder paste applied in stencil.

Solder paste is recommended to be stored in low-temperature storage to maintain its activity, and warming up (generally takes 4+ hours)is required prior to application to prevent its temperature from being incompatible with room temperature. When temperature varies dramatically, water drop will be generated on the surface of solder paste so that splashing will be caused in the process of high-temperature reflow.

In addition, you should also investigate on issues like how the solder paste applied in stencil will be processed, how solder paste is timed and how to administer and control solder paste that has been applied in original stencil when stencil is modified.

Another item needs to be carefully studied is the time when first batch of solder past is warmed up, especially for PCB Assemblers don't run 24 hours a day. As SMT line starts working only when solder paste is completely warmed up, some manufacturing houses will run the warming up 4 hours earlier or even one day earlier to save time and improve efficiency of SMT lines. It's necessary to know that solder paste's activity will be greatly decreased if the warming up procedure took place one day before application. Actually in practice, professional PCB Assemblers will surely scrap the solder paste if the warming up happened over 12 hours before application.
Solder paste printing capability

In terms of solder paste printing capability inspection, PCBs containing fine pitch (0.4mm or 0.5mm) BGA should be selected for inspection. Repeating solder paste printing should be implemented on the same piece of PCB for five to ten times and each time of printing result should be inspected under microscope to see whether issues like bridging or displacement occur.

For SMT manufacturer owning SPI (Solder Paste Inspector), it can be applied to measure solder paste amount (volume).

Furthermore, stencil cleaning is also one element affecting the quality of solder paste printing. As solder paste leakage tends to be caused by long-term printing, accounting for bridging, stencil should be cleaned with non-dust cloth after intervals of time or with ultrasonic wave to avoid hole blocking issue.

Solder paste quality administration and solder paste printing capability are the main focus of SMT process inspection. Of course, genuine solder paste printing technique contains far more items that'll be summarized into the following aspects:

a. Solder paste

Solder paste is mainly composed by tin powder (metal alloy powder including Sn, Ag, Cu, Bi) and flux whose volume ratios account for 50% respectively. It's necessary to select a type of suitable solder paste compatible with requirement of your products. Furthermore, tin powder can be rated with different numbers. The larger the number is, the smaller the particle is. Generally, No. 3 tin powder is used for SMT while No. 4 tin powder is applied for fine pitch or small soldering pad mounting.

b. Stencil

Steel is usually applied as material for stencil owing to its merits of free from collapse and strong intensity force. Apertures of steel are generated generally based on three leading different methods: etching, laser cutting and electrotyping with different fees. In terms of products with fine pitch IC, laser cut stencil is suggested since aperture wall through laser cutting is more straight and neat. In spite of excellent performance of electrotyping stencils, they have limited effect and the price is relatively high.

Stencil thickness and size of aperture greatly influence solder paste printing quality and reflow quality. According to principles, the key administration point lies in tin volume in that amount of solder paste has to be compatible with final required soldering amount. In theory, the smaller SMD component is, the thicker stencil has to be. However, keep in mind that the thinner the solder paste is, the more difficult tin amount will be controlled. Basically, the thickness of an ordinary stencil is within the range from 0.12mm to 0.15mm. When comes to fine pitch components (0201 or 01005), stencil with thickness of 0.1mm below is needed.
Silkscreen printing parameters setting and modification

a. Scraping blade pressure

A slight modification of scraping blade pressure leads to tremendous influence on solder paste printing. If blade pressure is too small, solder paste will fail to fall at the bottom of stencil aperture and to be effectively transferred to pad. If blade pressure is too high, solder paste will be too thin or stencils will be even damaged. The optimal condition is that solder paste is scrapped from the surface of stencil totally.

b. Printing thickness

Printing thickness largely relies on the thickness of stencil. A slight modification of solder paste printing thickness can be obtained through blade speed modification and blade pressure. Suitable reduction of printing speed of blade also leads to increasing of solder paste amount on PCB.

c. Stencil cleaning

In the process of solder paste printing, stencil should be cleaned the moment every 10 pieces of PCBs have been successfully printed in order to eliminate deposit at the bottom of stencils and pervasive solder paste. Generally alcohol without water is applied as cleaning agent.
To obtain genuinely high SMT quality, investigation and analysis have to be carried out on each manufacturing link and key elements so that effective control methods can be captured. Among the leading links in the SMT assembly process, solder paste printing is the most important. As long as reasonable parameters are set and corresponding laws between them are mastered, high-quality solder paste printing can be achieved at last.

ALLPCB has been providing full turnkey PCB Assembly services for worldwide companies for more than ten years. We have the capabilities to apply SMT technology into circuit board assembly process. Feel free to submit quote request for your PCB assembly project by clicking the following button. The quote will be sent to you within 1-2 working days.

PCB Design Perfection Starts in the CAD Library

Drafting elements in a CAD library part are not “Standardized” for specific values or sizes but there are recommendations that are coming out in the IPC-2610 series that include schematics, PCB assembly(PCBA) and fabrication. Documentation includes component outline and polarity markings for silkscreen and assembly. This article focuses on silkscreen and assembly Reference Designators.

 Every reference designator (Ref Des) originates in the schematic diagram and is transferred to the PCB layout via the netlist. They also appear in the Bill of Material that is exported from the schematic and passed to the assembly shop. The rules for reference designator assignment are established by the IPC-2512 publication. However the Ref Des size, font, CAD layer and placement location are left up to the EE engineer and/or PCB designer.

 Every CAD library part should have 2 distinct reference designators, one for the silkscreen and one for the assembly drawing. Both designators, in every CAD library part, are normally located in the center of the component body. The silkscreen reference designator is relocated outside the component body after the part placement is completed and approved by the design review panel. If via fanout and trace routing cause part placement nudging then it’s best to wait until that process is completed or duplication of effort will come into play. Also, if via hole sizes exceed 0.4 mm and they are not tented then it’s best to avoid placing the silkscreen reference designators over the via hole, as the ink will drop into the hole making the reference designator indistinguishable and eliminate the purpose of having the reference designator to begin with. If you are using large via hole sizes it’s best to wait until the PCB design passes the engineering routing review panel. Via sizes smaller than 0.4mm can be tented (covered) with solder mask and the placement of silkscreen designators can go directly on the via.

 The silkscreen reference designator height sizes are –

  • 1.0 mm – Minimum
  • 1.5 mm – LP Calculator Default
  • 2.0 mm – Nominal
  • 2.5 mm – Maximum

 The reference designator text line width is normally 10% of the height for good clarity and to prevent the characters from bleeding or blobbing together. The 0.15 mm height “Default” is what the LP Calculator uses but users can change the global setting values to any value or measurement system.

 The assembly reference designators are different in the fact that they never get relocated outside the component body outline. Assembly reference designator height sizes are –

  • 1.5 mm – Default
  • 1.2 mm – 0.5 mm for miniature components

 Here are some chip component assembly ref des height sizes that scale down according to the body size  –

  • 4520 (EIA 1808) = 1.5 mm
  • 3216 (EIA 1206) = 1.2 mm
  • 2013 (EIA 0805) = 1.0 mm
  • 1608 (EIA 0603) = 0.7 mm
  • 1005 (EIA 0402) = 0.5 mm
  • 0603 (EIA 0201) – 0.5 mm

 Note: All assembly body outlines are 1:1 scale of the physical component with the exception of all micro-miniature parts smaller than 1.6 mm length. Parts less than 1.6 mm length are EIA 0402 and 0201. These 2 parts assembly outline has to be enlarged so that the 0.5 mm assembly ref des fits cleanly inside it.

Also, most land patterns (CAD library parts) have the Lands (Pads) put on the assembly layer. This is true for all parts that are large enough to accommodate both the component leads and the assembly ref des without interfering with each other. When the component leads interfere with the assembly ref des, the component leads on the assembly layer are removed from the padstack. This includes all chip components, crystals, molded body parts and grid array parts with bottom only leads.

See Figure 1 for a sample of a typical silkscreen with the reference designators relocated outside the part.



 See Figure 2 for a sample of a typical assembly drawing with the reference designators inside the part, exactly where they were put when the CAD library parts were built. While the silkscreen reference designators must be relocated to an optimized location after part placement is completed, the assembly reference designators do not require any movement or cleanup. Also notice in Figure 2 that the large parts have lands (pads) built into the padstack and the small chip components do not have lands (pads) on the assembly layer. The LP Calculator allows the user to turn on/off Land on Assembly because some people do not want any component leads on the assembly drawing; rather they only want closed polygons with reference designators inside.


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