I got my first batch PCBs from JLCPCB in less than two weeks choosing low-priority shipping. I ordered five 2-layer PCBs with a laser cut stencil.
The service of JLCPCB was surprisingly good. I never thought these orders for 5U$ would be checked by a human being but during manufacturing I was contacted by a person called Tony Lee inquiring about the backside stencil. I haven’t included back side solder mask since there are no components except for some THTs and solder jumpers that require soldering.
Unfortunately even the best PCB manufacturer cant fix my layout errors - reading the datasheets and thinking for 5ct would have spared me some issues with the layout:
- Double check you schematics! Then check it again and let someone else look at it! It turns out I connected I2C SCL to SDA on the RTC.
- You should not run signals, especially clock lines, below the wires of a crystal for the Real Time Clock. These crystals work at µW level and are sensitive to cross-talk.
- You should read the datasheet of your RTC, if it says 6pF Load capacitance, buy a 6pF Crystal and not a 12pF Crystal. …and there are probably some more issues I haven’t found yet…..
All in all I payed 12US$ to learn the hard way to pay more attention. Actually I learned a lot more with this failure. For instance it it not easy to solder SMD with solder paste and solder iron. Soldering with solder iron works better with wire. Also applying paste with a manual syringe and a stencil doesn’t give the best solder paste print.
I made some experiments with my messed up half-way hand soldered board in the baking oven to calibrate the temperature and time and it works amazingly well!
Preheat the oven to 205°C (or at least that what I can adjust with the turning knob). Put the PCB for 3:20 minutes and you get a reasonable result. It didn’t even kill the ICs, or at least not all of them. The I2C port expander MAX7315 survived the procedure. I don’t know if it was the heat, solder errors or layout mistakes but sound didn’t work.
The result doesn’t look so bad, does it?