PDA

View Full Version : Removing ICs



Dms12444
February 12th, 2010, 04:29 PM
Category:How_To
This article covers the removal of socketed ICs. For the removal of soldered-in parts, see desoldering ICs.
It is often necessary to remove ICs for reseating, replacement or simply to salvage parts for later use. Many modern systems use ZIF (zero insertion force) sockets which makes IC removal incredibly simple. Most vintage equipment, however, uses standard DIP (dual in-line package) sockets, although you may also come across the occasional PLCC package.
DIP Sockets
200px|thumb|right|Removing a DIP integrated circuit using a screwdriver.
The preferred way to remove a DIP part is to use an extractor tool designed for the job. Some look like a large pair of tweezers with the ends bent inwards to grasp the chip. Others use a clamp and trigger mechanism to pull the part out of its socket.
One of the blanking plates from the back of a PC makes a handy extraction tool. Simply slide the top of it (where the screw goes) under one end of the chip and gently rock it back and forth. Alternate to each end till the chip is completely freed from the socket.
If you don?t have access to the above equipment, it?s quite possible to remove an IC using just basic tools. A long, thin-bladed screwdriver is good and, failing that, a sturdy knife is a reasonable substitute. Simply work the blade into the gap between the chip and its socket and gentle pry one end out a couple of millimeters. Take care that your chosen implement doesn?t poke through the gap and damage any delicate traces on the circuit board itself. Repeat at the other end; it?s a good idea to put another implement in the gap you just made to prevent the chip from working its way back in whilst you pry out the other end. Don?t just push a big screwdriver and try to pop the chip out in one go ? this is a sure-fire way to bend the pins. Keep working at alternating ends, a little at a time, and the chip will eventually pop out, hopefully in one piece. If you do manage to bend any pins ?sideways? (i.e. such that the pins are no longer evenly spaced) they can be gently pushed back into position using a small pair of pliers. Often the pins end up correctly spaced, but not aligned with each other. This is simply remedied by gently pushing all the pins on the same side of the chip against a hard surface like a workbench.
PLCC Sockets
200px|thumb|right|PLCC integrated circuits in their sockets. Note the recessed corners to facilitate extraction.
As with DIP sockets, the ideal method of extraction is to use the purposed-designed tool. This resembles a pair of tweezers enclosed in a scissor-like assembly which grips the chip, allowing it to be extracted easily.
Lacking the proper tool, it?s possible to lever out a PLCC chip by inserting two narrow objects (such as a pair of jeweler?s screwdrivers) into the recessed corners of the socket. Apply even pressure on both sides and work the part gently from its socket.
ZIF Sockets
If you?ve looked inside a modern PC, you?ll most probably be familiar with this type of socket. Assuming any heat shield which attaches to the socket has been removed, it?s simply a question of lifting the lever, replacing the now completely freed chip, and pushing the lever back down.
See Also
Inserting ICs
Reseating ICs