Archive for the ‘FR4 PCB’ Category

How to Test for an Open Short Circuit on a PCB?

Tuesday, May 18th, 2021

Every printed circuit board need to do full test before ship to our customer. but you may have doubt, the PCB was made according to the original Gerber file, why finish the PCB production process, why the short Circuit will occur on a FR4 circuit board?

A short circuit may also occur during reflow soldering. the solder paste may accidentally connect two pins that are very close to each other. In some cases, errors can occur during the PCB design process because the wiring between different networks accidentally connects.

We believe every PCB manufacture have their own test method to do short circuit, but today I would like share how Best Technology to Check for Short Circuits in a Printed circuit board.

Here are some important steps:

Step 1 Visual inspection

The first step for locating short circuits on PCB is to carefully look at the entire surface of the PCB. Best Technology QC guys use a magnifying glass or low magnification microscope during the circuit board examination. We check the whole board surface to see if there are some traces break off. Any cracks or blobs of solder should get careful attention. Check all your vias. If you specified unplated vias, make sure that’s the case on the board. Poorly plated vias can create a short circuit between layers and leave you with everything tied to ground, VCC, or both.

visual inspection

All the testing work will carry out according to IPC 6012 class 2.

Step 2 Use a Digital Multimeter to find out where is the problem

To test a circuit board for a short circuit, you need to check the resistance between different points in the circuit. If visual inspection doesn’t reveal any clues as to the location or cause of the short circuit, grab a multimeter and try to track down the physical location on the printed circuit board. The multimeter approach gets mixed reviews in most electronics forums, but tracing your test points can help you figure out what isn’t the problem.

Step 3 use Probe flying Tester &E-tester

As long as you are in Printed Circuit board field, you are definitely known Probe flying test and E-Teter.

Flying probe test systems require no test fixture, it can serve both prototype and small production, providing maximum flexibility for PCB manufacturers and this job can complete in a short time.

probe flying test
probe flying test-1

But when your circuit board become to volume, you will need to open a test tooling/test fixture to test the Printed Circuit board to test the open short circuit.

E-tester

In my next blog in June, I will introduce Probe flying test to you in more detail.

If you have any question about printed circuit board, you are welcome to contact Best Technology.

It is our great pleasure to communicate with you for any issue for printed circuit boards.

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What’s fiducial marks on the PCB?

Saturday, April 24th, 2021

You may ever be recommended by some PCB manufacturers to add the fiducial holes on the board edge. Do you know what is fiducial marks and what’s the purpose for this kind of holes in a PCB?

Now, let me to show you something for what is the fiducial holes.

Fiducial holes, we also call it fiducials mark, while we assemble a PCB, it will need to locate the positions for each component, and it is positioned based on the fiducial mark as the reference point.

There are 3 types fiducial marks, first type is fiducial marks on a single board, second type is the fiducial marks on a PCB panel, third one is the fiducial marks for some single component on the board.

Here are the pictures for you to understand the types of the fiducials.

Fiducial holes types
Fiducial holes

Fiducial mark on a single board is designed for positioned all circuits features on a single board. It is necessary to have a fiducial mark on a single board.

And fiducial marks on a PCB panel is used to assist positioning the circuits. 

For the fiducial mark of a single component, it is designed to position the fiducial mark of a single component, which can improve the placement progress (For QFP, CSP, BGA and other important components must have the fiducial marks).

So, it is important to add the fiducial holes on a PCB board.

Also, while we make the panel for the PCB board, on the diagonal of the four corners, it is required to have 2 fiducial points at least on 2 diagonal corners.  you can also place 4 marks on the four corners, but generally, assembly plant will only need 2 marks for recognize.

See below a PCB panel for reference:

PCB panel drawing Best Technology
Fiducial holes on a panel

In the other hand, while you design the PCB, please try not to put the silk screens, pads, traces etc. within 2mm of the optical fiducial marks. Otherwise, the SMT machine will not be able to recognize the optical fiducial on the PCB boards.

And if you add the fiducial holes on the area which without any circuits, to avoid the holes being etching while the process, so generally we suggest to add a metal circles around the fiducial holes, to make it more obviously on the boards.

If you have any new PCB design which you also want to add the fiducial marks.

You are welcome to contact Best Technology for a help and we will show our best help for you.  

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What is Blind Via and Buried Via for Printed Circuit Board?

Thursday, April 15th, 2021

In the Printed Circuit Board industry, believe that you are familiar with blind via and buried via. What is blind via and buried via for PCB? And do you know is the Blind via or Buried Via have special application in your Printed Circuit Board?

In order to know more, we would like to share more information with you today.

Best Technology is an experienced FR4 PCB manufacturer in China since year 2006, with more than 15 years design and fabricate experience for PCB, Best Technology accumulated more than 1000 customers from all over the world.

Before start, we need to know what kinds of hole for FR4 Circuit Board, Via, Blind Via and Buried Via.

What is a Via?

Vias are the copper-plated holes in the PCB that allows the layers to layer connection. The standard via is called a through-hole via, but there are several disadvantages to using through-hole vias in Surface Mount Technology (SMT). For this reason, we often use a blind via or buried via instead. A blind or buried via can be processed in a wide range of different measures, including plugged copper mask via, a plugged solder mask via, plated via or staggered via.

Via
staggered via

What is Blind Via?

The via connects the external layer to one or more inner layers of the PCB and is responsible for the interconnection between that top layer and the inner layers.

Blind Via

What is Buried Via?

For a buried via, is the inner HOLE, between both sides in the board up and down inside the layer after pressing is cannot see. So, it doesn’t have to take up the outer area.

Buried Via

Blind and buried vias are particularly advantageous in HDI board because they optimize the density of the boards without increasing board size or the number of board layers you require. They are most commonly used in high-density PCB designs like, or in FPGA and custom chip packaging.Here is the photo which Best Technology took from our production line to make HDI Printed Circuit Board for our USA customer.

HDI board under production
HDI process

Best Technology is a very professional manufacturer in printed circuit board and HDI Board. If you are interesting to know more information of us, come to contact us and we are looking forward to discuss with you more for Printed Circuit Board.

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High-TG FR4 Printed Circuit Board

Thursday, December 31st, 2020

If you work in Printed Circuit Board industry, you may know a normal PCB FR4-Tg is 130-140 degrees, the medium Tg is greater than 150-160 degrees, and High-TG FR4 Printed Circuit Board is greater than 170 degrees.
And what is a High-TG FR4 Printed Circuit Board? High-TG PCB is another name for a high-temperature FR4 PCB, it means the printed wiring boards designed to endure for extremely high-temperature. A Printed Circuit Board is defined as high-TG FR4 PCB if its glass transition temperature (TG) is higher than 170 degrees Celsius. High-TG FR4 will have better mechanical and chemical resistance to heat and moisture than standard FR4. The higher the TG value, the better the temperature resistance of the material, so High-TG FR4 is more and more popular particularly working in high power industry.
Best Technology can provide many different High-TG FR4 material for Rigid Circuit board, Typical High-TG FR4 PCB material including: ITEQ-IT-180A, ISOLA 370HR, ShengYi S1000-2 and etc.

Part of the inventory of raw material-1
Part of the inventory of raw material-2
Part of the inventory of raw material-3

From the following PCB picture, you can see the normal TG130 FR4 PCB substrate is not only softening, deformation, melting, as well as other phenomenon working under high temperatures, but also there is a sharp decline in electrical properties, which will effect on product life.

Solder mask blistering-1
、Solder mask blistering-2

If your FR4 Printed Circuit Board or PCBA board appear to above problems, then you should consider to use a High-TG FR4 Rigid Circuit Board. it may be catching your interest willing to understand a little bit more about High-TG FR4 printed circuit boards. Because High Tg Rigid Circuit board have a better stability at high temperatures, the substrate provides better heat resistance, mechanical and chemical stability for the circuit board.

BPM20396)

Properties/ Applications of high Tg PCB
With the rapid development of electronics industry, High-TG FR4 PCB is widely used in Uninterrupted Power Supply, precise instrument as well as industry. High-TG FR4 PCB material probably designed for the high functionality, high multi-layer development high-density circuit; higher heat resistance and high-density surface mounting technology (SMT). So, the demand on High-TG FR4 PCB material become more widely used PCB manufacturing.
What’s more, High TG material is also popular in LED lighting industry, because heat dissipation of LED is higher than normal electronic components, but same structure of FR-4 board is much cheaper than metal core PCB, such as aluminum PCB.
High-TG FR4 PCB materials have the following properties:
 Resistance to high temperatures
 Long delamination durability (aging of materials to consider for safety reasons)
 Low thermal expansion
Excellent PTH reliability
Good mechanical properties
High temperature durability
High value of thermal stress resistance
high temperature durability
long delamination durability
Low Z axis expansion (CTE)

BPM19308

Advantages of High-TG FR4 PCB
Higher stability: it will automatically improve the heat resistance, chemical resistance, moisture resistance, as well as stability of the device if increasing the TG of a printed circuit board substrate.
Bear high power density designs: high TG PCB will be a good solution for heat management if the device has high power density with quite high heat generation rate.
It can achieve with using a larger printed circuit board to change the design and power requirements of a device when reducing the heat generation of ordinary board, what’s more, it also can use the high TG PCB.
Ideal for multilayer & HDI PCBs: there will lead to high levels of heat dissipation because multilayer & HDI PCBs are more compact and have dense circuits. So high TG PCBs are often used for the multilayer & HDI PCBs so that it can make sure reliability in Printed circuit board fabrication.

BPM20005 TOP
BPM20005 BOT

 If your applications are in any danger of subjecting your PCBs to extreme temperatures or the PCB is required to be RoHS Compliant, it will be in your best interest to look into high-TG FR4 PCBs.
Come to contact Best Technology Co., Limited. for High-TG PCB assistance. we can help you determine if you need high-temperature printed circuit boards and direct you to which specific boards are likely to be useful for your design and application. If you are transitioning to RoHS or just need more information about the High TG laminates, just give us a call and we’ll be happy to accommodate you. contact us online right now.

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ENIG surface finish of FR4 Printed wiring board

Wednesday, November 4th, 2020

Continued to my last blog, do you know why we want to talk more for Gold surface finish of rigid Boards? I would like to take this chance to share more information for the capability from Best Technology.

Electroless nickel immersion gold (ENIG) is a type of surface plating used for printed circuit boards. It consists of an electroless nickel plating covered with a thin layer of immersion gold, which it can protects the nickel from oxidation. It is also used for welding and applied to contacts (such as keys, gold fingers on memory strips, etc
See attached complexity design for ENIG FR4 printed circuit board.

ENIG has several advantages over more conventional (and cheaper) surface plating such as HASL (solder), including excellent surface planarity (particularly helpful for PCBs with large BGA packages), good oxidation resistance, and usability for untreated contact surfaces such as membrane switches and other contact points. See the complex circuit boards design photo.

ENIG also does not wet as evenly or easily as HASL. In addition, ENIG is a costlier finish, but offers the best characteristics for printed circuit boards. The process requires the most steps compared to other common finishing types.
The thickness of Gold Best Technology conforms to IPC Standard IPC-6013.
Let us see the different for gold finish.

Gold-ENIG
The most important factor the gold serves as barrier and protectant to the nickel.
Advantages of ENIG

Immersion finish = excellent flatness
Good for fine pitch / BGA / smaller components from Samtec/Hirose/Molex
Wire bondable
Good heat dissipation
Long shelf Life (12 months in vacuum pack)

Disadvantages of ENIG
Expensive finish
Black Pad/Black Nickel concerns on BGA
Damage from ET (electronics test)
Signal Loss (RF)
Complicated Process

Gold-Hard Gold

Advantages of ENIG
Hard, Durable Surface
No Pb
Long shelf life

Disadvantages of ENIG
Very Expensive
Extra Processing/ Labor Intensive
Use of more solder Resist/Tape
Plating/ Bus Bars
Demarcation(delamination)
Difficulty with other surface finishes.

As an rich experience PCB manufacturer since 2006, Best Technology always improve its Rigid Circuit boards capability to meet customer requirements, If you have any question about the printed circuit boards (PCBs). Warmly welcome to send mail or call Best Tech.

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Main types surface finish of FR4 Printed wiring board

Wednesday, November 4th, 2020

Printed Circuit Board surface finish is a coating between bare FR4 board and components. The main function for surface finish is to protect the exposed copper circuitry and provide a solderable surface when assemblingsoldering) the components to a copper clad PCB board.

Most of the Rigid Circuit board company can make several different types of surface finish. Best Technology as a leading custom FR4 printed circuit board manufacturer since year 2006, it could provide following different finish.
HASL
Lead-free HASL
Immersion Tin/Immersion Silver
OSP (organic Solderability Preservative)
Gold
ENIG (Electroless Nickel Immersion)
Hard Gold
Wire bonding Gold

As the surface mounts assembly service became more complex and needs to conform to new regulations like RoHS and WEEE. People maybe face the question how to choose a suitable surface finish for your FR4 Copper board?

Before decide to choose suitable surface of copper conductors circuit board, you may need to take the cost, RoHS, your components type, PCB assembly method, factory circuit fabrication capability, and rigid board circuit testability into consideration.
Basis on above information of copper foil PCB, we would like to make a explain PCB finish in detail, wish this may help when you make decision at circuit board design and manufacturing.

HASL/Lead Free HASL
It is a most popular surface finish, and the cost is low and easy to repairable, it is acceptable for simple SMT. But the surface is uneven, it is not suitable for fine pitch components and not good for plated through-hole(PTH). In other way, it is poor wetting.
Material different with same finish
HASL(standard):Typically Tin-Lead
HASL(Lead Free):Typically Tin-copper, Tin-Nickel, without lead
The thickness will conform to IPC 6012 class 2 standard

Advantages of HASL-LF
Excellent solderability
Inexpensive / Low cost
Widely Available and used
Easy reworkable
Allows large processing window
Long industry experience / well known finish

Disadvantages of HASL-LF
Uneven surfaces for printed circuit board
No good for fine pitch components from Samtec/Hirose/Molex
Thermal shock
Solder Bride for circuit board assembly
Plugged or reduced PTH’s
Not suited for < 20mil pitch SMD & BGA
Bridging on fine pitch
Not ideal for HDI products

Immersion Tin

Advantages
Flat surface
No Pb
Good for fine pitch / BGA / smaller components
Mid range cost for lead free finish
Press fit suitable finish
Good solderability after multiple thermal excursions
Easy reworkable

Disadvantages
Very sensitive to handling – gloves must be used
Tin whisker concerns
Aggressive to solder mask – solder mask dam shall be ≄ 5 mil
Not recommended to use peelable masks
Exposed tin on final assembly can corrode
Not good for multiple reflow/assembly process
Difficult to measure thickness

OSP (organic Solderability Preservative)
OSP(organic Solderability Preservative) same with HASL, lower cost but the OSP have flat surface, and it is not good for PTH components, sensitive and short shelf life, it is very easy come to oxidation.

Advantages
Flat surface
No Pb
Good for fine pitch / BGA / smaller components
Inexpensive / Low cost
Easy reworkable
Simple Process
Disadvantages
Not easy to measure thickness
Not good for circuit copper board plated through-hole(PTH)
Short Shelf Life
Maybe cause ICT issue
Exposed Cu on Final assembly
Handling sensitive– gloves must be used and scratches avoided

The above surface finish of Printed Wiring Board compared with Gold finish, the cost is corresponding cheaper, but in my coming blog, I would like mainly to explain Gold finish for printed circuit board fabricator with 13 years rich-experienced in FR4 PCB custom contract manufacturer.

If you have any question about the printed circuit boards (PCBs). Warmly welcome to send mail or call Best Tech.

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What is PP (Prepreg) and CORE in a PCB?

Friday, October 30th, 2020

We all know that both Prepreg (PP) and CORE are important parts for the printed circuits board. And they are also very common on the PCB structure.

But what exactly they are? What’s the difference of a PP and Core for a FR4 PCB?

Prepreg, referred to as PP, it is a sheet material impregnated with resin and cured to an intermediate level (B-stage), known an insulating material for the PCB board.
As a prepreg material while the PCB production process, before lamination, it is mainly used as an adhesive material and insulating material for the inner conductive pattern of a multilayer PCB.

After the Prepreg is laminated, the semi-cured epoxy resin is squeezed away, starts to flow and solidify, bonding the multilayer circuit boards together, and forming a reliable insulator.

PP, it is placed between the two copper layers to isolate and make the two copper layers adhere. Below picture for you to see where the PP is on a PCB stack up.

And CORE, it is totally different as the Prepreg.

Core is with certain hardness and specified thickness, and with copper foil in both sides.
It is the basic material for making printed circuits boards, and the multilayer PCB board is actually made by pressing Core and Prepreg.
Sometimes, when people are talking about the Copper Clad Laminate (CCL), they also refer to the CORE.

And here is the major difference for the PP and Core:

  1. Prepreg is stayed with a semi-solid material in a PCB, similar to cardboard. But core is different, core is hard, similar to copper;
  2. Prepreg is similar to adhesive + insulator; while Core is the basic material of PCB, they have completely different functions;
  3. PCB Prepreg can curl, but PCB Core cannot bend;
  4. Prepreg is non-conductive, and the core has a copper layer on both sides, which is the conductive medium for a PCB board.

As an PCB manufacturer with more than 15 years experiences in China, Best Technology insists on using the best Copper Clad Laminate ( CCL) materials to make the PCB, no matter Prepreg or CORE, we will select the best FR4 materials for the PCB manufacturing, to make sure all the PCB boards we supplied to customers are with qualified materials and to be your best PCB suppliers in China.

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What’s the Countersink and counter bore on a PCB drawing?

Wednesday, September 30th, 2020

Firstly, do you know what’s a countersink and counter bore?

By definition, a countersink is a stepped hole, which can allow the fasten parts head to sink fully to the parts.

With counter sink on your design, the tapered head of a screw can sit flush with the top of the laminate, commonly countersink is used to install bolts or other connecting parts.

Below is the example for the hole drawing and picture for a countersink:

Picture: counterbore holes attributes

To drill your countersunk holes accurately in our PCB fabrication plant, the following information is need to be defined when you supply the PCB drawing for us to make the PCB:

  • Which side of the board is the countersink hole should be drilled, on top or bottom?
  • Is the sink and shaft to be through plated or non-plated?
  • Taper angle or countersink angle. 82°, 90°,120° etc.
  • Countersink diameter of top
  • Countersink diameter of bottom (body)
  • Depth of the countersink is to be drilledthe height of the screw to determine the countersink depth.

By comparison, a counterbore makes a flat-bottomed hole and its sides are drilled straight down. This is usually used when a fastener such as a bolt or cap head screw is required to sit flush with or below the level of a surface.

Below is the drawing and picture for a countersink.

Same as the countersink, the counterbore holes attributes drawing is needed to supply with your PCB drawing when fabricate the counterbored holes. But for counterbore on PCB, because the sides of the hole are always parallel, there is no need to specify the angle.

With below drawing, believe it will be more helpful for you to understand the difference for a counter sink hole and counterbore on the printed circuits board.

If need to have any question regarding the counter sunk or counter board on a PCB drawing, please contact us feel free.

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What is an HDI FR4 PCB?

Wednesday, September 16th, 2020

HDI abbreviation means High Density Interconnect. HDI PCBs have extremely density trace spaces and lines, micro vias under 0.25mm(10mil), smaller pads and higher connection pad density. See the photo of HDI board laser drill& prepreg thickness ratio.

It is very helpful in enhancing electrical performance and HDI PCB use for high-end products and HDI PCB is regularly used in 4G network communications, medical, Military and Aerospace. See the HDI board which Best Tech made for customers.

HDI PCB is the better option for high-layer count and costly laminated boards. Due to the increasing complexity of design structures laminate, the Blind vias and Buried vias are increasingly used in high-density circuit boards (HDI PCB board). Best Tech always improved manufacture capability for HDI, following production capability of the comparison for 2020 and the capability which Best Tech want to achieve at year 2021.

Following is the advantages to use an HDI PCB

The common reason for using HDI technology is a significant increase in packaging density. In addition, overall space requirements are reduced will result in smaller board sizes and fewer layers. 

1.Denser trace

2.More stable performance

3.Reduce interference inductance and capacitance effects

4.Improve signal integrity in high-speed design

5. Reduce frequent relocation of components

What’s mean for a blind via hole?

It is a hole runs from an outer layer, but not through the entire PCB. These holes can be drilled mechanically or using laser technology.

And what’s mean for a buried via hole?

This is a hole that runs between one or more inner layers. They are normally mechanically drilled.

By the way, we would like to make some explain for the through via hole, see attached photo to know the detail.

Do you want to know the different types for HDI PCB boards?

The following photos mainly shows the different laminate structures available from Best Tech for HDI PCB for prototype and mass production.

What is the minimum pad size of hole on the outer and inner layer?

This is different from manufacturer to manufacturer, but in general you can say that the majority of manufacturers can produce them as follows:
A = 0.10 mm
B = 0.15 mm
C = 0.20 mm

Finally, here is an 8L HDI FR4 PCB which we made for our customer at June. See the stack up information.

Surface finish: ENIG(2u”)

Features

1. 3+2+3  HDI FR4 PCB board

2. L1 L2、L2 L3、 L3 L4、 L5 L6、 L6 L7、 L7 L8 laser blind hole, micro via size:0.15mm

3. L3、L6 mechanical blind hole, hole size:0.25mm, through hole:0.3mm

4. minimum trace width and space is 3/3mil

5. Finished board thickness: 1.3±10%

6. following is the stack up information

For more information for HDI PCB, welcome to send any query to Best Tech for advice.

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How to prevent the FR4 PCB bended and warped after reflowing

Wednesday, August 19th, 2020

Everyone may know that PCBs are easy to be bended or warped when get through the reflow process. Do you how to avoid this issue? here are some advices your reference.

  1. Reduce the effect of temperature on PCB board stress

Due to the “temperature” is the main source of stress for board, so as long as the temperature of the reflow oven reduce the temperature or slow the speed of warming up and cooling down in the reflow oven, the board bending and warping issue can be reduced. But it may be occurring other issues, such as short circuit when soldering. See Best Tech make control for the temperature of the reflowing process.

reflow machine

 2. Use high Tg plate

 Tg is the glass transition temperature. The lower of the Tg value, the faster of board starts to soften after finishing reflowing, and deformed of the board become more serious. if use of higher Tg 170 material can increase the ability to withstand stress deformation, but the price of TG170 material is higher. See the stock of high Tg material from Best Tech.

Use high Tg plate

3. Increase the board thickness

If final application allowed, we recommend 1.6mm thickness to prevent the risk of board bending. Best Tech can provide PCB board thickness to 4.5~8.0mm.

PCB board thickness
  • Try to reduce the size of the board and the number of panels during design

 Since most reflow oven use chains to driving the board forward, if larger size of the FR4 PCB, the own weight will be deformed in the reflow oven, so during design try to design the long side of the PCB as a board edge, it can reduce the deformed. And

Same reason, if there are many PCBs in a big panel, PCB will be bigger and heavier, when get through the oven, the speed in the oven will be slowly and it will influence the deformed of the PCB. See following PCB board, we only panel 1 single piece into a panel to keep the size of FR4 PCB panel not bigger.

pcb
pcb

5. Use the reflow carrier/tray

If above methods cannot get a good result for deforming, you maybe can use a reflow carrier/tray to reduce the deformation. The reason reflow tray can fix the circuit board, after the temperature of the printed circuit board is lower than the Tg value, it can maintain the original size.

pcb in tray

6. Use Router instead of V-Cut

Since V-Cut will destroy the structural strength of the panels, try to use Router PCB board or just reduce the depth of the V-Cut will helps the deform issue.

pcb
pcb

If you want to know more about how we control the bended and warped for PCB, you are welcome to contact us.

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