Connections between layers

[gastorgrab]

How exactly are the connections made between the layers of a multilayer circuit board.

Looking at the holes of one of the bad boards, through a microscope almost looks like a rivet was used.

Solder at this failed connection refused to bead at the base. At closer inspection i noticed that the metallic ring around the hole was missing. The connection looked strange in another way; what i first assumed was solder formed itself into a perfect tube inside the resin board.

Looked like this:




Is there a brass rivet/tube that connects the outside layers of a multilayer circuit board. Is this what the capacitors are soldered to?


This is a board that i got from ebay for $4.95 that appeared as though it had been factory re-capped before. It was covered with known-bad capacitors that were incorrect (higher than) values from similar boards that i own.

There was no memorable 'event' when the solder ring went missing. I don't know if maybe the tube shape, and the damage, was caused by the fact that a dental probe was used to clear the hole of solder. The solder ring could have also been pulled off by soldering braid but i think i would have felt some kind of momentary resistance when removing the braid.


Does solder alone connect the pads on opposite sides of the circuit board?
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[gastorgrab]

Re: Connections between layers

Something like this wouldn't make any sense:





It would be very difficult to do, and probably an expensive method of electrically connecting the layers.

What about a tube though?
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[Harvey]

Re: Connections between layers

They are plated through holes. The copper layer in the center (making it look like your second picture) is built up in layers in an electro-plating process. Its easy to pull this plating out while desoldering if you overheat the joint.

[gastorgrab]

Re: Connections between layers

That makes a strong argument against the use of a dental pick. (or any other mechanical method for removing solder)
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[kc8adu]

Re: Connections between layers

That makes a strong argument against the use of a dental pick. (or any other mechanical method for removing solder)
.

the pick or pin method is safe as long as the pin is smaller than the hole and you dont force it in before the solder melts.
drilling on the other hand is an extreme risk of killing a thruhole.
i got to fix a board on a rare industrial machine where someone used a pc drill to clear holes.
it was a real mess!
i spent about 8 hours fixing this one.
there are 3 of these in the world and no spare parts!
the owner was so happy to see it fire up that even after i handed him a nice fat bill he threw a pizza party for the whole shop.

[gastorgrab]

Re: Connections between layers

How the hell do you fix something like that?

Where there no connections to 'interior' layers?
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[kc8adu]

Re: Connections between layers

you figure out where those traces go between parts and add jumpers outside.

[i4004]

Re: Connections between layers

do you have a pic that shows how does that look finished?

[Krankshaft]

Re: Connections between layers

Yeah don't you hate that.

I have lifted a few traces in my day it seems like I spend 25% of the time cursing myself out for lifting the trace in the first place.

50% of the time tracing out where to place the jumper wire or wires (if the trace in question splits at any point) and the other 25% actually installing the jumper .

And of course whenever this happens I don't have the service manual for the board in question either because it is unavailable or because I didn't want to shell out to buy it .