Electronics > Projects, Designs, and Technical Stuff
What are these black squares for (pcb design question)
max_torque:
On a dual layer pcb from a large UPS, the pcb has a lot of small black squares visible:
They look to be in the centre of the prepreg/fr4 and can be seen as a pattern of 'bulges' under the large copper pours on the top and bottom of the pcb. I have back lit the pcb for that photo so you can see the copper pours / traces on the back, and the squares between the layers
They are not across the whole pcb, so can't just be an artifact of the material used for the stackup?
They are most prevalent under the high voltage / switching portions of the board, so perhaps they are either some form of emc shield / ground or something to increase (or decrease) the pcbs impedance?
Has anyone seen such a thing before?
Ribster:
If it's a multi layer PCB, and those pads are copper, it is for warping.
If not, i guess it's just the marking of the prepreg.
dmills:
Bet that's a multi layer board and they have kept a buried plane out of the high voltage area, which makes those squares copper to help equalise the copper distribution for both warping and etch quality.
It is a thing that PCB houses will sometimes ask to be permitted to do if you have a buried plane on ONE half of the board, especially if the layer is heavy copper.
Regards, Dan.
max_torque:
It's a scrap board, so i'll attack it and see if those squares ARE copper! I can't see any internal traces, just lots of squares!
Doctorandus_P:
Can you post some macro photos?
Preferably from before, and maybe also from after you've "attacked" it, but then you probably know and it is nof of much use anymore to post...
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