| Problem |
Observations |
Causes |
Recommendations |
| Voiding (>15%)
Voids are measure as a percentage of the pad area. Even though DirectFET will
be unaffected by voids up to 40% area customers will generally not accept over 20%.
18% voiding
 |
X-ray images show voiding levels between 10and 40% |
Reflow profile, reflow profile is often the cause. |
Check reflow profile, check whether large contact components also show voiding. Adjust profile if required (see appendix) |
| Board finishes, some require more energy than others and can effect voiding. |
See above |
| Poor reflow equipment. Multi-zone ovens with nitrogen will give better results than small ones with just air. |
Generally, with profile work the level of voiding can be bought down to low level voiding.Some of the population may exhibit voiding up to 20%. |
| Solder paste |
Some types of solder paste (even different ones from the same manufacturer) can give very different results. Using the same profile and settings |
| Board or component oxidation or contamination. |
Check that the component and boards are not obviously corroded and that the storage precautions have been adhered to. Look for other components affected |
| Voiding (low level)
Voids are measured as a percentage of the pad area. Even though DirectFET will be unaffected by voids up to 40% area customers will generally not accept over 20%.
low level voiding |
X-ray images show low level voiding |
Insufficient solder to make joint well. Accompanied by some joints that are poorly formed or have feathered edges. |
Check stencil design if reduction exceeds 30% the reduction needs to be considered. |
| Reflow profile still not optimum. |
It gets very difficult to totally remove voiding. All factors referenced in the voiding section need to be considered. Do not get drawn in to trying to fix low level voiding if it is not directly related to an issue of ours. |
| Board finishes, can significantly affect low level voiding. |
There is nothing that can be done by us to remedy this |
| It is unlikely that ovens running air will get near to the performance of ovens using nitrogen. |
Do not expect to obtain the same results on different ovens. |
| Solder paste |
Some types of solder paste (even different ones from the same manufacturer) can give very different results. Using the same profile and settings. |
