I recently posted this on Reddit, but after feedback I figured it would be useful here also. Over the years, I’ve accumulated some knowledge about assembling Printed Circuit Boards (PCBs) and it never occurred to me that everyone hasn’t gone through the same school of hard knocks that I have. So here are a few tips when assembling boards.
Here are some of the things I learned over time:
- Use a stencil if you aren’t already. OSH Stencils makes good quality Mylar stencils at pretty low cost. The time saving versus dispensing solder paste with a syringe is huge.
- As much as possible, simplify access to the bare components. By this I mean, adjust for how you pick them up. I pick up ICs with a basic vacuum tool, so I keep them in the trays they came in. The resistors/capacitors I pick up with tweezers (my cheapo vacuum pickup doesn’t do so well with small parts), so those are in bulk containers. LEDs are in their tapes, with the polarity clearly marked. The little time-saving details add up.
- Through-hole components: insert/solder them based on height. Place the lowest-height parts first, otherwise it’s too hard to hold them in place upside down. I use a piece of foam to hold them in place while I solder.
- It helps to put down extra flux before you place an IC with very close pin spacing like a TQFP part. The flux will help it self-align during reflow and makes solder bridges less likely.
- If you’re doing multiple boards, it’s faster to place the same part on all boards at once. i.e., making 10 boards: place U1 on all of them, then U2, then R1, R2, then R3, etc. The repetitive motion saves time because muscle memory sets in.
- Make sure you have assembly costs built into your product before farming out the assembly. I know this sounds obvious, but it’s amazing how many people forget about details like this and end up losing money overall. A good rule of thumb is that your product should sell for 3-5x the Cost of Goods Sold (COGS), which includes assembly cost.
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