Author Topic: opinion needed - soldermask and potential shorts  (Read 1046 times)

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Offline AstromechJapanTopic starter

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opinion needed - soldermask and potential shorts
« on: October 26, 2018, 12:18:30 am »
I made a bonehead move on my PCB design.   If you look at the image below, you can see that I put a GND via (tented) underneath a VDD pin.  The VDD pin that is above the GND via is not used (ie: no solder on the pin at all and no corresponding pad underneath of it).  only the corner VDD/GND pins are actually used/soldered.

What I SHOULD have done is swapped the GND/VDD planes and made the via for the VDD rather than the GND... but such is life and I now have 40 PCBs with this design.
The PCBs are a simple LED matrix board.  Each LED is capable of max of 60mA at 5V.

So, my question is, can I still use these PCB boards?  Will the solder mask provide an adequate/workable insulation between the VDD pad and the via? 
I know this isn't a good solution, nor is soldermask rated as an insulator as it can have air-pockets/pin-holes, etc.  This I know. 

My question is, do I need to scrap these boards, or will it (while not recommended) be ok for the application?

 

Online ataradov

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Re: opinion needed - soldermask and potential shorts
« Reply #1 on: October 26, 2018, 01:11:29 am »
Solder mask will mechanically isolate the pad just fine. But your problem would be solder getting there. Tentet vias mat not be fully covered and may have small regions of copper still exposed. There is no way those regions will make a mechanical contact, but if solder gets there, it may form a bridge.

Putting vias like this under tiny devices is not ideal anyway, since vias are slightly raised over the plane of the PCB. 
« Last Edit: October 26, 2018, 01:16:09 am by ataradov »
Alex
 
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Offline t1d

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Re: opinion needed - soldermask and potential shorts
« Reply #2 on: October 26, 2018, 07:00:21 am »
Maybe add a small piece of Kapton, or electrical tape, over the via? Kapton can take the heat, better, but electrical tape might be the better insulator. What about liquid electrical tape?
 

Offline t1d

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Re: opinion needed - soldermask and potential shorts
« Reply #3 on: October 26, 2018, 07:03:14 am »
Remove the pin, from the chip?
 

Online ataradov

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Re: opinion needed - soldermask and potential shorts
« Reply #4 on: October 26, 2018, 03:36:21 pm »
Remove the pin, from the chip?
It is a 2x2 mm chip. Removing pins will probably damage half of them and will cost more in labor than reordering the PCBs.
Alex
 


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