Electronics > PCB/EDA/CAD

PCBWay issue with QFN solder bridge, what to do?

(1/13) > >>

VEGETA:
Hello,

I have TPS54394 IC with the QFN 16-pin package. PCBWay gave me this email:


--- Quote ---Thank you for your order xxxx to PCBWAY. This is yyyy, your service representative.


After checking your file, we found that IC distance did not reach to 0.22mm, we can not  do the soldermask

bridge, Here are some solutions
1. Change IC distance to 0.22mm
2. With IC distance less than 0.22mm, we do not do soldermask bridge, but it will be easy short for assembly
--- End quote ---

and with a picture attached here.

What I understood is that they offer solder mask between pads up to just 0.2mm or 0.22mm but not less... my design IC have less (about 0.15mm) and they suggest that I either change the pad size or just remove solder mask between these sections.

I read that removing solder mask of tiny components is an ok behavior but wanted to verify.

this product will be manufactured to be soled later on, this time just a test board.

Note: my pads are the accurate size, solder mask on each pad is the same size as the pad. I have no problem with removing the solder mask bridge of that area if it helps.. and this product will never be manually soldered or assembled, all by fab house and assembler service.

best regards,

ataradov:
It is fine, you can just tell them to proceed with manufacturing. They can't make reliable solder mask bridges, but in many cases they would be made. Some of them would likely break, some will stick.

I always keep those bridges in my gerbers. May be one out of 10 ties they would complain, other time they just make the board without asking.

For prototypes it does not matter, for mass production - you need to figure this out with your PCBA house.

Feynman:
Are you sure your footprint is correct? In the picture it appears that the pads in x-direction have more distance to each other than the pads in y-direction.

wraper:
There is something wrong with your footprint if you need 0.15 mm solder resist bridges for footprint with 0.65mm pin pitch. Even JLCPCB makes solder resist bridges for 0.5mm pitch QFN. I personally usually supply gerber files with 1th solder mask clearance and let the fab do their best by adjusting according to their process, instead of making larger on my side. Never received a complain that gap is below minimum allowed. Surprisingly usually they do much tighter gap than their websites claim. Also note that if pads are wider than they need to be, likely you will have solder bridging problems.

ataradov:
On a second look, yes, the footprint looks busted.

TI site just made me hold a button for 10 second to prove that I'm not a bot. What a joke.

Navigation

[0] Message Index

[#] Next page