Re: broken circuit board advice

jped.aru@xxxxxxxxx wrote:
On May 29, 11:44 pm, m...@xxxxxxxxx wrote:
On May 29, 9:32 pm, jped....@xxxxxxxxx wrote:

So I have this little circuit board thing(don't ask what it is, I
don't really know myself, that's why I'm trying to fix it) that my
friend stepped on and broke the usb male end off of. He said I could
have it if I could fix it. Ok so anyway, I figured it would be a
simple matter of soldering the piece back on and that the solder
connections were the only things that were broken. But, when i took a
better look at it, I discovered that the metallic area on the board
where the connections from the usb male end thing attached (as in
green part of the board and metallic part of the board) were broken
off. I didn't even know that that could happen. So, is there a way
to fix this? I can't solder the connections back, because it won't
stick without those little metallic pieces. Thanks in advance for the
help.
Have you scraped the solder mask?

I don't know what that means. Sorry, I'm a noob. If you mean, scrape
where the little metallic part used to be, then yes.

Circuit board anatomy:

The part that looks like a little board or card is the "board" or more formally the "substrate". This is usually made out of epoxy-glass, which is usually a material called "FR-4". The "FR" in "FR-4" stands for "fire retardant", it probably refers to the epoxy used, and it's probably not what people really use any more. Cheaper consumer goods use a phenolic paper board -- it's what you'll find in clock radios and the like. It's weaker, it burns at a lower temperature, and it smells funny when it gets hot. It's also extremely cost effective if you don't ask too much of it. Really expensive equipment may use Teflon-glass or ceramic for a substrate, but I doubt you'll see that in any consumer equipment.

The metal part is made of copper, it form the circuitry and each 'wire' is called a 'trace'. AFAIK it's made by plating onto the board.

Boards can be:

- Single-layer, single-sided (cheap clock radios, again): All the traces are all on one side. This is very inexpensive to produce, but the layout of the traces is very constrained.

- Single-layer, double-sided (probably what you have): There are traces on both sides, and most of the holes are plated on the inside so a circuit can be carried from the top side to the bottom. More expensive, but quite versatile.

- Multi-layer: This is built up from a bunch of really thin double-sided boards that are glued together in a special press. I am _not_ up on the whole process, but if you don't mind spending $$$ you can have about as many layers made as you're willing to pay for. The job of laying out a really tight circuit is considerably eased, but each layer costs more $$$. Computer mother boards are often 4 layers, and it's a miracle that they aren't six or eight or more, given what they do. Someone spends a _lot_ of design time on those!

There's a coating over all of the board except the parts that you want to solder to. It's called "solder mask" or sometimes "solder resist". It protects the board from inadvertent solder bridges during manufacture, and from corrosion afterwards.

All the writing on the board (usually in white paint) is called the "silk", because it is silk-screened on (actually all the layers are silk-screened on).

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html
.

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