Hacking the Xbox

Appendix B - Soldering Techniques 221
moisture trapped inside a chip boils but cannot escape, causing a
pressure buildup that culminates in a destructive release event. Chips and
boards operating in a humid environment or that have been washed in
water should be baked in an oven at around 200 to 250°F for a few hours
before desoldering with a heat gun.
Another option that is particularly appealing for hobbyists is to re-alloy the
solder joint so that it melts at a very low temperature, below 300°F. A
company called Chip Quik (www.chipquikinc.com) holds the patent on
this technique, and removal kits can be purchased from many vendors,
including Jameco (order number 141305). This technique is appealing
because it requires no special equipment, and it is easy and fairly safe, as
shown in Figure B-7.
To do so, first coat the chip pins with soldering flux, then melt the chip
removal alloy onto the pins of the component to be removed. This will
create a large bead of low melting temperature alloy all around the chip.
Next, heat the entire bead by dragging the tip of the soldering iron through
the bead. The stored heat in the chip and the alloy will keep it molten long
enough for the whole chip to be easily slid off its pads. Finally, clean up the
low melting temperature alloy by heating it with a soldering iron and then
wiping it away with a cotton swab. The alloy will wipe off fairly easily from
both the board and the chip.
This re-alloying technique preserves the integrity of the removed chip’s pins
as well as the pads on the circuit board. The downside of this technique is
that cleaning up the alloy can be a bit messy, and tiny particles of alloy can
get caught between the pins of neighboring chips. (Caution while cleaning
up will prevent this problem.) The other downside is that removing chips
consumes the removal alloy, so removing large numbers of chips with this
alloy can become expensive in the long run. Fortunately, chip removal is a
fairly rare occurrence for most hobbyists.
The “ball grid array” (BGA) package is a type of surface mount package
that is becoming increasing popular due to its high electrical performance
and density. These packages are attached to a board through a large array
of solder balls underneath the package. Clearly, this kind of package
cannot be soldered using a conventional soldering iron. In addition, BGA
packages are very difficult to inspect because most of the solder connections
are buried deep below the package. The only viable method for
attaching these components is to use an oven that heats the whole board
and the component to the point where all the solder balls melt. Typically,
the alignment of these BGA packages is accomplished with the aid of a
machine of some kind, and the inspection of these BGA packages is
accomplished with either X-rays or ultrasonic imaging.
The equipment required to install these kinds of packages is very
expensive, so the best way for a hobbyist to install a BGA packaged
device is to pay a professional assembly house to do it. Companies such
as Naprotek (www.naprotek.com) that specialize in quick-turn, low
volume prototyping will install a BGA packaged device for a fairly