removing parts from PCBs

[Jeff Walther]

>Date: Fri, 11 Nov 2005 21:03:39 -0800
>From: "Chuck Guzis" <cclist at sydex.com>

>On 11/11/2005 at 8:31 PM compoobah at valleyimplants.com wrote:
>
>Yes,  I hold the board component-side down and flame it from above--a lot
>of components will simply drop out of the board once the solder has
>melted--do this out-of-doors as the fumes from the epoxy or phenolic can be
>pretty noxious.  Keep the flame moving.  Sometimes just tapping the board
>will cause quite a few components to to fall out.  DIPs usually require a
>pair of needle-nosed pliers or small screwdriver to remove.
>
>Some invert the arrangement and do it component side up with the fame from
>below.  I'm not convinced that one method is any better than  the other.
>An old propane barbeque grill might also be another approach.  Another
>might be to use a heat gun.

I use the heat gun approach.  I have a Milwaukee heat gun I bought at 
Home Depot with adjustable temperature from 100 - 1000 degrees F.   I 
use something between 600 and 900 depending on my application.

If I want to remove a component from a board and reuse the board, 
(e.g. remove soldered down PROM for reprogramming) I cover the 
surrounding components in modeling clay.   This may or may not 
provide any protection from heat, but it does keep them from blowing 
away.  The first time I tried desoldering with a heat gun, I found 
that all the surface mount passives (resistors & caps) surrounding 
the target chip were randomized.

For big surface mount chips I like to use Chip Quik desoldering 
alloy, which will lower the melting point of the solder on the board. 
If I preapply Chip Quik, I can usually use the 600F setting for a 
minute or two to loosen a chip.  I've successfully done this on chips 
as large as 208 pin QFPs.

Jeff Walther