Saturday, February 24, 2018

Surface Mount repair - Lead Cut Method

The subject this morning is a USB to CAT CI-V interface cable.  Someone (not me) plugged it into the wrong 3.5mm port and blew the chip up so badly that the case was deformed due to the heat.  The chip was obviously bad, there are very few other chips on the board, so I just ordered a new chip.


Some folks don't have a hot-air desoldering tool for surface mount components.  So how does your average Plugger of ham get a multi-pin surface mount chip off the board without damaging the board?  When you know you have a ready replacement chip there's an easy way to remove it from the board.  Don't try to unsolder every lead and try to preserve the chip.  You will get frustrated.  Just clip the leads off with your best fine clipping tool or EXACTO knife.  Tip the chip up and clip the remaining leads.


I have a simple general use soldering iron as well, it gets a LOT of use.  I don't file my tip down.  I take it out anneal it in a and hammer it down to a fine point on the anvil.  The act of hammering it to a point makes the tip hard again.  I find it lasts a lot longer this way.  You will need a sharp tip on your iron to do this properly.

This is what makes it easy, just take the hot soldering tip and wipe it across the lands of the board.  The clipped off leads will stick to the iron and they will just be left behind when you dip the iron's tip in the cleaning sponge.  Easy!


Once the chip is off then using a set of helping hands and magnifying glass, putting the new chip in place is simple (provided your hands are steady and your eyesight is good).  The lands should be clean and only a tiny amount of solder is required to make the connection.


None of us are getting any younger, so using a eye loop and a magnifying glass in conjunction can be helpful too.  Hope you find these tech tips helpful.  de N3FIX at the Cly Institute for Radio Repair.







No comments:

Post a Comment