Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.

'Blue solder' residues



'Blue solder' residues | 27 October, 2004

Hi all, been recently wave soldering some pcbs with no problems and have now noticed what looks like blue residues on some solder joints. We have been running this product for around six months and this is the first time we have seen this. It is randomly appearing on the glued 0603 caps and resistors, but also around the conventional components solder joints.

Any ideas on What this residue actually is, it can be removed by dry brushing/contact with swabs, (also heating with soldering iron), Flux application is within vendor specs, and we are running no clean.

Contact time is 2 secs chip wave, 3 in main wave. (Approx)

Thanks in advance.


reply »


'Blue solder' residues | 27 October, 2004

We talked about a similar "Blue Haze ( Not the same as Purple Haze)" awhile ago

The BIG difference is that yours is soluable.

reply »


'Blue solder' residues | 28 October, 2004

Hello Loz,

Blue residues on circuit boards can be caused by copper corrosion, component body deterioration, marking permanently, and adhesive break down. In this case, a more subtle mechanism appears to be possible. This is a no clean application, so cleaning, and the causes listed above are unlikely candidates.

Many ´┐Żlow residue´┐Ż no clean fluxes are deactivated by subliming the activator (adipic acid) in the soldering process. Sublimation is defined as changing from a solid to a gas and vise versa without going thru the liquid state. As the activator sublimes to a gas, it can recondense as a solid on the solder joint as the board exits the wave leaving microscopic crystals of the activator on the newly formed solder joints. Very small crystals can diffract light and give a blue color. This can come and go due to air currents, activator concentration, conveyor speeds, preheat temp, etc.

I hope this helps,

Steve Stach Austin American Technology (+1) 512-335-6400

reply »

FPC* - Fluid Pressure Control - Dispensing Pump

Online IPC Training & Certification