Electronics > Beginners
PCB Layout AC Question
floobydust:
For heavy or high current parts, I would not use the IPC minimum annular ring.
The appliance fires (dishwashers, clothes dryers), class action lawsuits were the PCB relay pins becoming hot spots due to crappy PCB layout or vibration fatigue and cracked joints.
I don't know your application or PCB specs. Is it base 0.5oz copper plated up to 1oz?
I have to try a simulation but I'm sure there is actual current flow to the backside of the pads and cutting that off can result in localized high current densities on the copper.
The ULN driver can drive all four relay coils, it's just a suggestion for ~20 fewer parts.
The mounting holes look much better.
admiralk:
Thanks
There is a good chance I will make several of the pads bigger, if for no reason other than to make it easier to solder. However, without thermal reliefs would it really make much of a difference in the case of those? I mean are the pads separated from the traces somehow? I could be missing something, but it seems to me that even if I tripled the size of the annular rings, the only difference would be that they would just add a bulge to the end of the traces.
I will look closer at the driver, I was thinking I would need one for each of the relays. Having just the one chip for all of them might be a better idea. The D5_x are connectors for off board LEDs and R1_x are the resistors for them, they would still be there no matter what.
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