15 Nov
2005
15 Nov
'05
5:24 a.m.
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