Removing surface-mounted ICs

From: Clint Wolff <vaxman_at_uswest.net>
Date: Wed Jun 7 01:17:50 2000

Hi Mark,

I would recommend against putting the board in an oven. This will
result in the entire IC getting too hot, and possibly breaking.
Modern plastic package absorb a small amount of water from the air.
Heating the part may result in a small steam explosion. ICs are
shipped from the factory in sealed bags with some desiccant inside.
The label on the outside says to solder them down within a fairly
short time after opening (couple days IIRC).

That being said, you can pick up a small propane torch at most
hardware stores. Any typical propane or MAPP type torch will do. Or you
can use a dremel (or equivalent) to carve enough of the board away
to unsolder one pad at a time (very slow, but the only way to remove
plastic shrouded connectors without destroying them).

Finally, I have access to a hot air desoldering station at work, and
can desolder them for you. Contact me OL for this option.

clint
vaxman_at_uswest.net

On Mon, 5 Jun 2000, Mark wrote:

> 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
>
>
>
Received on Wed Jun 07 2000 - 01:17:50 BST