PCB DFM (design for manufacturing) expert - DFM design review services

We perform DFM reviews for other companies.
•  DFM starts with the guidelines in the company’s DFM Manual. These best practices and guidelines should be applied to the CAD libraries.  Footprints correctly designed result in higher yields and better reliability.
•  It is important to have DFM guidance and a useful DFM review of the gerbers.
•  Having a DFM engineer assisting during the design cycle will pay dividends at the end  
• Let AS Design engineering perform a DFM review of your design before gebers go out to Fab.

How it works: Share your design with us or send us the gerbers early in the design cycle. We will send a DFM review back to you with pictures that point out not only the design flaw but the suggested DFM guideline to follow.

For example:
Not enough space for solder pallet between TH and SMT part. Process Wave soldering Small SMT too close- tall inductor will steal heat.


Figure 1

Figure 2

AS Design Engineering has many years of experience with overseas factories.
Why is DFM Important?
•  A bridge between the design teams and the factory is extremely important. Reliability issues may arise and product returns can cost a company money and brand damage.
Why CAD program based DFM checkers are only basic
•  They use spacing rules and are not able to make decisions.
•  For example, DFM rule that radial caps should be placed in only 2 orientations: 0 or 90° Auto insertion machines ( if your factory uses them) can only place 2.5 and 5mm pitch caps and only rotate 0 or 90°.
•  Even hand assembly best practice requires only 2 orientations of polarized TH components.
Why DFM reviews save costs:
•  Less board spins to correct design defects from factory corrective action reports
•  Minimize defective product returns
•  Faster time to manufacturing without delays
•  Stop making the same mistakes over and over again
Some examples:
•  Placing tall components too close to low components during SMT reflow can steal heat in the IR oven and prevent the smaller part from soldering properly. (see figure2)
•  On a double sided reflow PCBA (SMT parts on both sides) heavy SMT parts should be soldered on the second reflow cycle because heavy parts can fall off the PCBA. Design should be checked for heavy parts only on one side.
•  How to get the most heat transfer out of an IC thermal pad dissipated to the PCB copper ? Many designers blow as many vias as possible under the pad but here is a better way: (Paste layer is yellow) Paste bonds to copper –vias transfer heat

Figure 3 shows multiple vias will steal paste
x-rays show spotted solder joints		 Figure 4 shows a better way. Paste pads bond to copper and vias transfer heat. Best of both worlds
VIAS WILL STEAL PASTE AND PREVENT GOOD SOLDER BONDING TO COPPER BETTER SOLUTION--  SOLDER BOND + HEAT TRANSFER



Figure 3

Figure 4

Preventing Cracking Ceramic Caps:

Caps are orientated wrong way and may crack during depanelization or assembly
Caps are in correct orientation



 


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