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bawj , 11-29-2024, 10:17 AM

I am trying to get my PCB manufacturered and assembled through JLCPCB and had used a 25 pin BGA component. Their team came back mentioning that space between solder mask opening was too small (< 0.3mm) to be produced, and suggested creating 1 large solder mask opening instead with a risk of short circuit. Has anyone faced this before? What did you do?

QDrives , 11-29-2024, 03:04 PM

Which component / package?
Pitch?
What solder mask expansion did you set?
Which solder resist color?
With LDI you can have a solder mask expansion of 30um and a web (sliver) of >= 70um. So a minimum of 130um between pads (copper).

bawj , 11-29-2024, 05:21 PM

The component is the BQ25120a DSBGA 25 pin 4.0mm pitch. This is for a flex PCB.

bawj , 11-29-2024, 05:24 PM

The photo in the OP is the production picture they came back with

bawj , 11-29-2024, 05:24 PM

Here is a photo of the layout. I had left solder mask expansion to 0.

bawj , 11-29-2024, 05:25 PM

Without the slivers of solder mask in between the pins, would the risk of shorting as they mentioned be high?

QDrives , 11-29-2024, 07:50 PM

JLCPCB states that a minimum distance between pads should be 0.2mm. With 0.1mm web (sliver). That mean they set the solder mask expansion to 50um. https://jlcpcb.com/blog/basic-design-of-solder-mask

So you have 2 possible options:
- Accept the JCLPCB proposal and risk shorts below the BGA.
- Choose a different fabricator that can produce it with smaller tolerances, like Eurocircuits https://www.eurocircuits.com/pcb-design-guidelines/soldermask/

bawj , 11-30-2024, 06:21 AM

Thank you, I have also tried searching around on EEVBlog and some have mentioned that this is usually not a big issue. However, I decided to not take the risk and use a bunch of discrete components instead.