Yeah that was a face palm moment for a rookie.
The price jumps up sharply for low quantities but for 100 boards 25mm x 200mm it was not much more expensive and it totally beats the cost of the time it takes to apply capton tape.
The board only handles inputs so there is not concern for heat dissipation. If I go 4 layer I will add several RGB LEDâs but they are surface mount and their traces can go on the top and stay away from mechanical stress.
I had considered abusing silkscreen as protection but worried about it eventually failing. Last thing I want is dealing with warranty issues.
I looked into conformal coating but that is applied after assembly.
Over-all I am blown away by the many constructive suggestions from everyone. So much more than I hoped for.
So many constructive replies! Thanks everyone. This has to be one of the best Forum experiences I ever had.
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I just want to add this note:
Spacing the push buttons off of the board is a very bad idea. The body of the button is what transmits the force of the button press to the board. If you space the body away from the board, it will eventually lead to solder joint cracking. Either use a mechanical spacer, or go to a multi-layer board, or re-route the traces.
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I agree with @3Dogs.
Even a sticker may not be solid enough to pick up the mechanical stress.
But if you take a sticker into account, than here is a hint:
Thinner stickers made of PVC will probably take more stress off the solderpads than thicker paper stickers.
Aligning is easy when you apply the sticker using water with a drop of dishwashing detergent, or even better a liquid that is made for that purpose. Find more on gooogle.
Yes, it takes a day or two to dry.
In some applications, the flammability of this sticker becomes important.
I think many people are overlooking this fact, extra operations in a production environment add cost . . . time is money and it also adds risk if not done correctly or the solution is not thoroughly tested.
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I have read that there are silkscreens that can be assumed being the single isolation (from safety point of view). As I remember the test with sharp tool was defined that such silkscreen had to pass. PCB manufacturer have to confirm that such silkscreen is used. I have never asked them about it so know nothing more.
Earlier, I did a test and for 1000 pieces, the difference between 2 and 4 layer PCB was 25ct each.
Now you can spend half (or a whole) day to put tape on all those PCBâs, and itâs probably cost effective, but itâs no fun to do so, and your (skilled) workers may revolt and go looking for another job after a few months of doing such tasks.
With a 4 layer PCB you also get more flexibility in the design and a process that is âinherently goodâ. You cant forget the tape if there is no need to put the tape there.
What does it cost if you get warranty claims because of failed or forgotten tape?
Or hidden lost revenue? A customer that does not come back because of your âkludgyâ previous solution?
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Recently I started to use 4 layer PCBs. The reason are ICs in QFN with thermal pad packages that I was not able to route all (except GND) at top what I was able with TQFP by going with VCC under ic and propagate through corners and all VCC pins.
What I donât like in 4 layer PCB is that now I have at bottom not only GND zone with only GND vias. Assuming that:
- solder mask is not isolator,
- ferryte is not isolator,
I canât put ferryte plate (I use Ď 36mm) directly touching my bottom what was my standard practice for RFID antenna.
No, she died with the Tupperware
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