Bubbly PCB track problem (80-90’s)

[@rt]

Hi Guys,
I have two identical retro boards from the early 90’s where one is uncoated, and the other is green and the tracks are bubbly.
There is air/gas between the copper and the substrate, even though the copper is still continuous and intact, and the board works ok.
Meanwhile, the unprotected board looks great

I’m hoping someone can give me the industry term for this PCB problem to help in describing it to piers in the collector world,
as I’ve also seen it on older arcade boards, and retro computing.
Cheers, Brek.

[wraper]

Those are not bubbles. I guess you have a board without solder mask which was soldered with solder wave. Then it was coated with protective lacquer. What you consider being bubbles is just solder on the tracks.

[@rt]

Ok, thanks. They don’t push down so I can’t say you’re wrong
The green one would probably be the better board of the two in that case.

[@rt]

Ah ha! You’re busted!
Well you’re right about my board, but this original Apple 1 board has the problem,
and described by the seller in the description as bubbling and peeling off.
http://www.ebay.com/itm/282050295252?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

[wraper]

Ah ha! You’re busted!
Well you’re right about my board, but this original Apple 1 board has the problem,

There is air/gas between the copper and the substrate

•  Solder mask is bubbling/peeling on the back of the PCB

Ebay board have different problem, not what you described.

[jahonen]

I think this is due to how solder mask were applied. Non-SMOBC soldermask is applied after the HASL, so when board is wave soldered, part of the solder penetrates under the solder mask and produces the "bubbly track". Nowadays, the common SMOBC (solder mask over bare copper) soldermask is applied before any finishing plating, so solder can't penetrate under it and thus no bubbly tracks.

Regards,
Janne

[knks]

Dave has video about this. Starts at about 6:00