Defective PCB – (actualy not)

[Big O]

Was starting to work on a Photon Phuzz (interestingly started on this when Pink Jimi visited the forum for help).  Assembled the parts and started soldering when I discovered that one of the solder pads/eyelets for the Bias Pot is solid, no center hole.  I did not solder over the eyelet and only discovered the defective pad when inspecting the solder joints of the adjacent R3 resistor with magnification and a bright LED light.  Fortunately I had only soldered 3 components to the board – 2 resistors and a diode. Below is a picture showing that light does not penetrate the left most solder pad for the bias pot.

Below is the back of the board.  Note that there are no solder bridge bridges or spillover from the adjacent soldered resistor.  The marks on the solid pad are from attempting to use a metal pick to penetrate the defective solder pad.

Below is the metal pick I used to try and make a hole through the defective pad.

Anyone have any ideas to fix this?  The drill bits that I have with my high speed rotary tool are too large for the eyelet.  Or do I need a new PCB?

[Chuck]

I’ve never seen that on any of Barry’s boards.

Unless you are really steady and absolutely always on target I’d advise against a high speed rotary tool (although you can find small bit sets on Amazon).  I use this for clearing solder errors:

I’ve had it for years.  Probably came from a hobby shop.  The blue is painters tape wrapped around the bare aluminum shaft for better grip as well as preventing discoloring of the fingers.

Chuck

[Barry]

That looks like a spilled blob of solder to me. In other words that is not a manufacturing defect if it is solder.

If it is solder try a soldapult, solder wick or toothpick on it while heating the pad.

I mean I have done this myself but saw it actually happen when a tiny drop fell off my iron and splatted on the board.

If it does not melt then that is the only thing like that I have ever seen before. I could send another board either way.

By the way I checked my other boards and they do not look like that.

[Big O]

Well duh!  It was solder.  A couple of minutes with solder wick and the tip of my solder iron, I extracted the tiny amount of solder that had been in the eyelet.

In 15 years of soldering components on boards, I have never come across this before.  Yes, I have had solder spilled over from an adjacent pad that looked like a small blob in the hole.  But nothing like this where there was such a tiny amount of solder in the hole, that there was a meniscus on each side so it appeared like an incomplete punch out with metal bridging the entire eyelet.  Even very close up with a strong magnifier there was no evidence of any marks surrounding the soldered over pad to suggest that solder had bled over from the adjacent pad.  Probably a tiny drop that dripped off the tip of the iron falling perfectly into the center of the pad.

Before I read your reply Barry, I turned on my iron and then got out my solder braid and removed the solder and was absolutely surprised.  Just the way it appeared close up I didn’t think it was wayward solder, but decided to try a removal just in case before I attempted any other more invasive measures.

Ta da!  Now I can complete the pedal.

[Barry]

Think of it as a Hole in One. Just about as rare but happens.

[Big O]

The old saying is:  if you hear hoof beats behind you, think of horses, not zebras.  Its a common saying in medicine that basically means – one should focus on the most likely possibilities, not the unusual ones.  Unfortunately in this case I first thought this was a zebra until coming to my senses.

[Author]

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