Archive for August, 2016

Why Soldermask Opening or Tented was not the same like the Original Gerber file?

Monday, August 29th, 2016

Recently customer compliant that the soldermask for some holes, esp for PTH (plated through hole, sometimes people named Via) was wrong, because in his original Gerber file, it was opened, but on actual printed circuit board, it was tented (covered), and some cases, some was tented and some was opened at the same time. It made customer confused.

In fact, there’s a default rule in PCB (printed circuit board) manufacturing: If the PTH (Via) was less than 0.60mm, then the soldermask will be made as per factory’s default rules: making them as tented (covered), regardless it was tented or opened in customers’ original Gerber file.

Here you can see pictures showing a board with a 0.30mm PTH, soldermask was opened in original Gerber file, but in real board, it was tented.

0.3mm Via soldermask

0.3mm Via soldermask

And in this board, for 0.508mm PTH (via), some soldermask was opened and some was opened.

0.508mm Via soldermask

0.508mm Via soldermask

Why like that? Here are two major reasons:

1) For PTH(via) less than 0.6mm, normally the function was only to electrically connected trace, not for electronic components assembled; so whatever PTH was opened or tented, it doesn’t matter.
2) In rigid printed circuit board manufacturing, it’s not easy to etch away the soldermask around PTH less than 0.60mm. As soldermask was made by that method: printed whole area with oil (soldermask), then undergo develop & exposure, then pass the etching line. The chemical will etch away the oil accordingly to the drawing, but if the hole was too small (less than 0.60mm), then the oil around will be very difficult to etch away, so you will see some oil was etched away (soldermask opened), some oil still here (soldermask tented)

If diameter of hole was bigger than 0.60mm, then it’ll be easy to etch away and some of them will be used in assembly, so we will make according to Gerber file and you will see the board exactly like the drawing. See bellowing a picture showing a board with 0.889mm (0.035mil) PTH.

0.889mm Via soldermask opening

0.889mm Via soldermask opening

Sometimes, people just use these hole as testing point, not for assembly, then we suggest to add another PAD connected to this hole so that you can test it easy. To tested on hole was not stable as tested on a PAD.

In a conclusion, in future, if the hole was less than 0.60mm and you really want it to be opened, please add special notes when release order, and allow us to enlarge the opening diameter of soldermask (around 0.60mm) so that soldermask of these holes will be opened.

Please contact us if still any question about soldermask opening.

New Automatic Solder paste Printer Adopted in SMT & PCBA

Thursday, August 25th, 2016

Great news! We (Best Technology) had adopted a new Automatic Solder paste printer for SMT /PCBA since Aug 25th, 2016. We use “G5” which is No. 1 brand in domestic market, made by a Chinese company, the repeated position accuracy is +/-0.01mm, and printing accuracy is +/-0.025mm.

Everybody know the most important element which will affect the quality of SMT /PCBA is the solder past printing quality. Excellent solder paste printing is the base for excellent quality of final SMT /PCBA quality, esp. for the small components such as SMD Chips with small size as 0402, 0201, 01005; IC with small pitch package such QFN, LGA, BGA; Connector with 0.25mm, 0.3mm, 0.40mm pitch.

Here are some pictures of new Automatic Solder paste printer.

Auto Solder Paste Printer

Auto Solder Paste Printer

Auto Solder Paste Printer printing the board

Auto Solder Paste Printer printing the board

Auto Solder Paste Printer with PCB printing

Auto Solder Paste Printer with PCB printing

PCB with solder paste

PCB with solder paste

Welcome customers release more SMT /PCBA orders to us. To learn more about Automatic Solder paste printer, or our SMT /PCBA service, please contact us right now!

Which kinds outline process can make PCB less burr?

Friday, August 12th, 2016

Generally there are two methods to do PCB outline, routing and punching.

 

Routing is suit for those simple boards with simple outline. But it is easy to cause burr on the edge. Also, if don’t make the tooling holes well, the boards may be easy moving while routing, which cause to the outline crooked.-

 

So, If you need the outline more precision and nice, the best way is to custom a tool for punching, in such way, the outline shape is very exact and no so much burr on the edge. It is used for those boards in big panel with small boards, special outline as well as high precision boards. Punching also can speed up the production lead time.  But for such way the cost is expensive than routing.

What’s the difference for FR1, FR2, FR3 and FR4 materials?

Friday, August 12th, 2016

FR1 is basically the same as FR2. FR1 has a higher TG of 130oC instead of 105oC for FR2. Some laminate manufacturers who produce FR1 may not produce FR2 since the cost and usage are similar and it is not cost effective for having both.

FR3 is also basically FR2. But instead of phenolic resin it uses an epoxy resin binder.

 

FR4 (FR = Flame Retardent )is a glass fiber epoxy laminate. It is the most commonly used PCB material. 1.60 mm (0.062inch). FR4 uses 8 layers glass fiber material. The maximum ambient temperature is between 120o and 130oC, depending on thickness.

In China FR4 is the most widely used PCB base material, next is FR1 then FR2. But FR1 and FR2 are usually used for 1-layer PCBs because they are not good for passing through holes. FR3 is not recommended to building multi-layer PCBs. FR4 is the best selection. FR4 is widely used because it is good to make from one- layer to multi-layer PCBs. With only FR4, PCB companies can make all kinds of PCBs, which leaves the management and quality control much easier, and eventually it can reduce the cost!

 

Form the analysis above it is obvious that FR4 is the best selection to make PCBs in market. Some materials may be cheaper but it can only be used to make one-layer boards, and the reliability of the boards made by these materials is not good. So they are only used for one-layer and very simple boards.

Can my PCB don’t make solder mask for both side?

Friday, August 12th, 2016

Of course PCB can make no solder mask on both side, just make sure the solder mask layer (GTS& GBS) on your Gerber file is empty, or let us know you don’t want to make solder mask while quoting or before production, then we won’t make solder mask on both side, just print the circuits as you want.

Can make different solder mask thickness on top and bottom side?

Friday, August 12th, 2016

It’s okay to make different solder mask on top or bottom side only. Such as 50um on top side and 20um on bottom side. For 2 OZ board, the area without trace, solder mask thickness can be 40-50um, and after three or four times printing, developing, drying, the thickness of solder mask over copper trace can also reach up to 40-50um.

What is PCB Gerber file?

Friday, August 12th, 2016

The Gerber format is an open 2D binary vector image file format. It is the standard file used by printed circuit board (PCB) industry software to describe the printed circuit board images: copper layers, solder mask, legend, etc.

Gerber files should be inside a .rar or.zip archive with standard file extensions:
Extension                       Layer

  • pcbname.GTL                 Top Copper
  • pcbname.GTS                 Top Soldermask
  • pcbname.GTO                 Top Silkscreen
  • pcbname.GBL                 Bottom copper
  • pcbname.GBS                 Bottom Soldermask:
  • pcbname.GBO                 Bottom Silkscreen:
  • pcbname.TXT                  Drills
  • pcbname.GML/GKO        *Board Outline:
  • 4 layer board also need
  • pcbname.GL2                   Inner Layer2
  • pcbname.GL3                   Inner Layer3

Notes: Gerber file must be RS-274X format.  Drill file(pcbname.TXT) should be Excellon format.
PCB Outline is required.

Gerber file is used for manufacturing process.

Can we make groove on Ceramic PCB?

Friday, August 12th, 2016

Yes, we can make groove on Ceramic PCB. But the technology to make groove is different from FR4 PCB, MCPCB.

As you know, FR4 PCB, MCPCB, the substrate is rigid, so we can rout to get the groove, but ceramic PCB is fragile, so we can not use rout on the Ceramic substrate. Normally, we use laser cutting to make the holes on Ceramic PCB, you may think we should use layer cutting, but it is not available, because if use laser, then it will be cutting through. So to make a tool is necessary, that’s correct, we make a tool to form the groove at the substrate stage.

What is DCB PCB?

Friday, August 12th, 2016

DCB is abbreviation of Direct Bonding Copper. It is an electrical composites with high thermal conductivity and high dielectric strength. Which formed by the copper foil and the ceramic substrate suffering high temperature melting and diffusion process in an inert gas. In power electronics industry, the DCB promoted module package chip interconnect technology development and stimulate power electronics products towards on high power density, multi-set, high-performance low-cost.

The advantage of DCB PCB:

  • the copper foil and ceramic can be bonded directly, which have good thermal conductivity, usually thermal conductivity of aluminum -DBC is 24 ~ 28 W / (m K), AlN-DBC is 170 ~ 220 W / (m · K).
  • The stability of ceramic substrate makes DCB has a very excellent insulation properties under various conditions.
  • Coefficient of thermal expansion close to the silicon enables semiconductor chip which soldered on board to avoid the stress caused by temperature changes, therefore can greatly extend the life of semiconductor products.
  • Can process all types of graphics and lines like PCB, and strong current conducting capabilities make it easy to achieve board-on-chip interconnection function, the maximum carrying capacity will be up to 100 amps / millimeter.

The application of DCB

  • Energy-saving control of appliances.
  • Energy-saving control of industrial electrical.
  • The transportation of wind, solar and other new energy.
  • New type solar panels.

Parameters of DCB

Name Unit Test Conditions Parameters
Insulation resistance   ≥1
Insulation voltage VAC(.RMS) 1min ≥3000
Tensile strength kN/cm2   ≥5
Peel strength N/mm   ≥6
Thermal conductivity W/m.k Indoor 20℃ 24~28
Thermal expansion coefficient 1×10-6/℃ 50~200℃ ≤7.4
Adaptable of temperature range   -40~+200
Hydrogen embrittlement temperature   400

 

The flatness tolerance value of DCB

DCB diagonal Length L (mm) 200~250 150~200 110~150 80~110 60~80 40~60 20~40 <20
Tolerance value (mm) ≤1.0 ≤0.8 ≤0.6 ≤0.4 ≤0.2 ≤0.1 ≤0.05 ≤0.03

 

 

Parameters of ceramic substrate

 

Name Unit Test Conditions Parameters
Al2O3 content %   ≥96
Insulation voltage kV/mm   ≥12
Permittivity   25℃  1MHz ≥9.2
The dielectric loss tangent   25℃  1MHz ≤3×10-4
Thermal conductivity W/m.k Indoor 20℃ ≥22
Thermal expansion coefficient 1×10-6/℃ 20℃~500℃ ≤6.7
Density g/cm3   ≤3.7

What is the X-out board?

Friday, August 12th, 2016

X-out board means that the boards are not qualified. The trace may damage during the production. Normally we will do some obvious mark to distinguish the X-out board.

When we make the boards in panel, it will be easy to have X-out board, and what’s more, when we panel several pieces board in a panel, there will be more pieces for X-out board.

Some of the SMT manufacture didn’t accept the X-out board, since it will influence the production efficiency.

But this kind of circuit board and can’t absolutely avoid in the process, so even the plate number, the more the number of circuit board factory scrap will be, the more relative costs will increase.

So circuit board manufacturers hope that the less number of plate, the better, because it can avoid the loss of X – board, the sheep wool or out, of course, if the board factory has been unable to overcome the loss of X – board, the final price will respond to the customer.