Blowholes in THT component soldering

DIP soldering blowholes is also called pinholes in China PCBA community. It is a very common defect in DIP producing, if we don’t fix it, there will be a serious risk.

First risk is short soldering. It is small pin hole visible, but under it, maybe a big space inside solder point. This short soldering will increase the contact resist, get weaker electricity function, temperature may increase higher than expected after long time working. Finally it may get open circuit.

Secondly, there is maybe bad soldering inside blowholes. This will get less mechanical strength. It may get worse and wore oxidation in long time working, thus get open circuit too.

IPC quality checking system hasn’t special description for blowholes. Thus it need us to conclude our experience in production.

IPC has only a similar requirement like below, called less wetting present.

Blowholes cause and preventive solution

1. PCBbad hole copper

Incorrect drill may cause non-smooth PTH. PCB factory need maintain drill bit well, or use good material bit. Via plating line need work correctly too.

2. PCB need to be baked enough

The main reason of blowhole is the moisture come out after soldering. If PCB not baked well, water will be kept in the holes. Then it can steam to moisture in high temperature during wave soldering process.

3. Too much flux

Flux will be spayed to PCB before wave soldering. If too much flux sprayed to board, there will be much water kept and steam to moisture in wave soldering oven.

4. Inappropriate heating temperature

There is a preheat zone in peak wave soldering machine, following flux spay device. PCBA can be getting dry enough here. If the temperature is too lower, board can’t be dry enough. Water will be kept into soldering oven.

5. Clean component.

Oxidized component or dirty pin, can get bad soldering or pinholes too. IQC and component insert line need check carefully.

Shenzhen Cirket Electronics Co.,Ltd has produced PCBA (Printed Circuit Board Assembly) for around 20 years, has experienced many kinds of electronics mainboard. Blowhole can be improved by good managing system, but can not avoid completely. Cirket has passed both ISO9001 and IATF16949 quality managing system, there are very few blowholes in our board.