4 Jun
2000
4 Jun
'00
3:50 p.m.
The blowtorch has served me well in this context. When a board is not
important to you and the components are, it's possible to do that with a
propane torch of the inexpensive variety. It's important that they put out
considerable heat, however. I've found my Weller butane torch to be not
terribly useful in this regard. You can use a typical butane torch of the
type you normally use to solder copper plumbing to heat the component leads,
and quickly if that's possible. I often char the board but if you make the
traces come off along with the IC, you're probably overdoing it. Normally,
I heat the board from the component side in the case of surface mounted
parts, knocking it against the table. Unless you really want to make
yourself sick, this is best done outdoors. Afterward, in fact, immediately
afterward, it's advisable to toss your clothing worn during this process
into the laundry. A shower will relieve the pungent odor, somewhat
garlic-like that you'll put out for the rest of the time before your next
ablution.
My luck has been remarkably good using this technique, but there have been
occasions when it wasn't so good.
Dick
----- Original Message -----
From: Mark <mark_k(a)iname.com>
To: classiccmp <classiccmp(a)classiccmp.org>
Sent: Sunday, June 04, 2000 6:58 PM
Subject: Removing surface-mounted ICs
Hi,
This isn't strictly on-topic, but I guess it could be applied to
maintaining
classic stuff, so...
Can anyone recommend a way of removing surface-mounted ICs (specifically
SOJ
package DRAM chips) from a board? It's not
critical to keep the board
undamaged, but the chips must be kept intact since I want to solder them
into
another device.
I read of a technique involving turning the board upside-down and heating
the
board area opposite the ICs in question with a
blowtorch. The ICs drop off
when the solder melts. I don't have a blowtorch, but do have a gas stove.
Heating the board over the stove will probably not be a good idea, since
the
ICs would need to be lifted off when the solder melts.
Since I want to
recover several chips, they are likely to get too hot doing it this way.
I do have an electric grill. The element is at the top of the oven. What
about
putting the board component side down in the oven
(near the heating
element),
and heating until the solder melts?
It will be important to get the temperature profile right here, I think.
Putting the board straight into a hot oven might not be a good idea, but
on
the other hand having it in the oven as it warms up
from cold may be too
long.
In a way, doing this would be similar to IR reflow soldering.
What is a typical melting temperature for solder used on surface-mount
components? The oven control goes up to 260 Celsius (from memory), which I
hope is high enough.
Has anyone else attempted something like this? Do you have any advice?
I guess the same technique could also be used for soldering surface-mount
components (with board component side up, and solder paste applied to the
pads).
-- Mark