Once in a 1000 pcs PCBA production, we found that there a cap easy to fail off from the board, with our SMD Soldering Strength testing, there will be about 2%~3% boards not pass this test, and even the pads on board GET OFF...
This is really a high rate, checked the PCB design files, we found that there the capacitor package on the board was too small:
Normally, for 0603 capacitors (60 mils by length and 30 mils by width), to ensure the soldering strength, it is better to make the solder paste surround the whole pads, that is, while the capacitor length is 60 mils, it is better to keep the pads distance outline larger, at least 75 mils, such as below:
So in the PCB production, we enlarged the capacitors' pads, to make the outer line distance from 63 mils to 75 mils:
With these DFM updates, the capacitor's soldering strength is much more firm, and the problem of the C1 falling off rate reduces a lot.
The comparison:
Original Design:
With Makerfabs DFM:
Suggestion to Designers:
--> For 0603 resistor/capacitor, the outline distance for pads is at least 75 mils, suggest 90 mils. And suggest 60 mils for 0402.
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