hiya guys, wanna ask if someone ever come to this kind of pretty annoying problem. when i need to replace a bad chip , almost the time, i'm facing a hard pins to desolder, they are Vcc and Gnd pins. the hole layer is usually having a square form. what i mean with hard is, even i heat the solder to its limit, and put it in the pin, the blob didnt melt :( so i try to hold it longer, but it dont even move and become blacky. uhh! what da! damn, i'm always felt sick when it comes the time to suck this thing up >:( and always got a really bad and mess up hole after desolder, i.e the layer is pulled up, the pin is broken . what make it worse is if theres no spare part to replace. maybe i would be fired soon because of this fault :( God, why i cant doing something in a good manner? is there anyone know how to do it in a more smooth way?

thanks a bunch
Posted on 2003-04-19 21:19:39 by dion
It's possible that the board has power and ground planes; and the pcb design did not give any thermal reliefs.

I would recommend cutting the Gnd and Vcc pins, then using a 100W iron to remove them.

You can also use the 100W iron to solder those two pins on the replacement, but only if the iron won't cause any ESD damage, and you don't over heat the chip.
Posted on 2003-04-20 03:38:43 by eet_1024
Re Thermal Reliefs

When a board has a plane of copper (great for removing noise problems), a thermal relief makes a via easier to solder.

Plane to Via w/o Relief (the O is the Via):
=========

====O====
=========


Plane to Via w/ Relief (the O is the Via):
=========

=== | ===
===-O-===
=== | ===
=========


Notice in the second diagram that the via is not directly conected to the plane. Instead traces provide the electrical connection, but reduce the thermal conductivity.
Posted on 2003-04-20 03:45:03 by eet_1024
It can also be helpful to cut each lead away from the body first, then you can reheat each lead in turn and pull it out. Small sharp cutters work best.

I have a pair from work that go for near 30 bucks USD, I wouldn't use anything else.

(Of course, I also have a temperature controlled solder station with grounded tip that goes for several hundred... its a permanent loan from a previous employer who forgot to ask me to return the borrowed stuff before laying me off)
Posted on 2003-04-20 12:42:36 by Ernie
One thing you can do is instead of trying to remove the pin, leave it in and solder the pin of the new chip to it. You will probably have to clip the new chips pin a little to make it fit.
Posted on 2003-04-20 13:53:19 by drhowarddrfine
thanks guys, yes, i should prepare myself with a more heavy solder :grin:
Posted on 2003-04-21 19:23:57 by dion