What is this stuff on this pc board?

Rosin core solder leaves flux if not cleaned. So, yes.

I'm not sure what that is, but it doesn't look like any flux residue that I've ever seen. The little brownish 'blobs' on the tops of Q200's legs do, as does the lttle patch at the upper edge of its centre leg. If it is flux residue, I'm sure that you would agree, as a repairer yourself, that it is very unusual for it to be white like that, which is why you are asking for the opinions of others on here, I would guess ? Perhaps solder guru Smitty could offer an opinion from the production point of view.

Arfa

Looks like dried coffee creamer :)

I've seen it before; It's flux residue that has become damp, then dried out again. Is there also a touch of rust on the end of the transistor's legs (the brownish blobs)? And possibly a bit of corrosion on the edges of the tracks, or just poor resist? Yet I can't see any corrosion on the 0R22-resistor, but the solder is a bit grainy, so it's probably either lead-free or has been damp. I bet the white deposits will turn back to ordinary flux deposit if heated. Martin.

residue

as

like

here,

dried out

(the

poor

a bit

heated.

The "brownish blobs" are not flux or anything else. They are simply the ends of the cropped component leads. The device was soldered with long leads and then the leads were cropped.

The white residue could be water soluble flux which has not been removed after soldering the component.

looks like flux residue. But the boaed has not been washed and dried properly after soldering process. rw

David

Conformal coating. Probably used for moisture protection among other things. Like a varnish. Also some coatings were epoxy types.

Bob AZ

Plenty of solder processes these days do not require washing and cleaning. Most consumer goods in fact.

Graham

It is NOT conformal coating. Besides you'll probably only ever see that on high-end industrial or military gear.

Graham

SNIP

It seems that the brackets around the date in the link act as a terminator to the hyperlink underlining so you will have to copy and paste the full url to get the document.

It works for me.

Graham

Or just about anything marine related.

and

Thanks Graham. When I paste the url link using Agent the underlining stops before the opening bracket so I thought I'd better give a warning.

It is flux residue. All of the VOCs have been removed and the solids are left. Not to worry. Not pretty, but, ehhh...

Al

When I double click the link it is incomplete.

It is not of manufacturing origin.

It looks like a (field? post-inspection?) repair -- the replacement of "Q200". After soldering, the leads of Q200 have been snipped off with a pair of flush wire cutters -- leaving a clean exposure of the copper of the leads.

So, the residue is probably dictated by the brand and the quality of the solder used in the repair.

Jonesy

That is flux residue left after a run through a PC board washer, and oven dry cycle. I saw it all the time in manufacturing. The ladies that worked the cleaning room hand cleaned that with IPA and flux brushes, or with a spray defluxer when they couldn't reach it with a brush.

That isn't conformal coating. It is a poor cleaning after the board was made. The thinnest flux was washed away, the thickest is still there. The powder is where the flux was a little too thick to completely wash away in the automated cleaning process, and there was no attempt to finish the job.

this

I should mention that the photograph of the circuit board came out of a high end Proceed amplifier. These amps costs big bucks and fail frequently. The company offered no support to the independent guy. The authorized service place in my area wanted $150 an hour plus parts to repair it. No surprise that Proceed is out of business now.

The other amp I saw this residue in was an a/v receiver, a Marantz SR-8500.

Thanks for your replies.