Onkyo Unknown Service manual

Techniques for Replacing Surface Mount (SMD) IC’s

Every technician has had to replace a surface mount device (SMD) IC at one time or
another. How do you successfully remove and replace a surface mount IC? By successful
I mean removing the defective IC without damaging the delicate traces on the PC board
and aligning and soldering the replacement IC in place. Here are a few techniques you
can use to remove and replace a surface mount IC.

IC Removal

Desoldering Braid: Desoldering braid is a specially treated fine copper braid which

draws molten solder up into the braid where it solidifies. Desoldering braid is usually
sold on a small dispenser reel. The best way to use desoldering braid is to press the tip of
a hot iron onto a short length of braid that is placed over the joint to be de-soldered.

The iron will subsequently melt the solder, which will be drawn up into the braid. If the
desoldering braid is not drawing the solder but just seems to push it around the board add
a small amount of solder flux to the braid and try it again. After most of the solder has
been wicked use a dental pick or similar object and lift the IC pins while heating them
with a hot soldering iron.

Razor Knife Technique: Using a sharp razor knife, align the blade close to the body of
the IC and on the top of the row of pins. Applying a constant downward force cut the
pins away from the body of the IC. You will hear a distinct clicking sound as you severe
the pins.

Work your way down the row. Repeat this process for each row of pins until the body of
the IC is free from any pins and can be lifted away from the board. By cutting and
removing the body of the IC you are removing the “heat sink” that draws the heat from
the IC pins when you try to remove the IC with desoldering braid alone. Next, use
desoldering braid and a hot soldering iron to remove the remaining IC pins from the
board. This method allows you to remove the IC quickly and without damaging the PC

board’s copper traces. One word of caution, this technique takes some practice. You are
using a sharp razor knife that WILL cut the boards traces if you use too much force while
cutting through the IC’s pins. Check the board before you solder the new IC in place. It
is highly recommended that you practice this method on some scrap boards before trying
it on a customers unit.

Wire removal method: Apply flux to the IC pins. Use desolder braid to remove as
much solder as possible from each pin. Thread fine stainless steel or enamel coated wire
under one row of pins. Secure one end of the wire on a nearby component (i.e. a large
Electrolytic capacitor). Starting at the loose end, heat each pin and pull wire
simultaneously. Pull the wire as close to the PCB as practical.

As the solder between the pin and pad melts, the wire will pop out and leave the pin
standing free of the pad. Repeat these steps for the other sides

Hot air desoldering tool: There are several types of hot air desoldering systems.
Desoldering tools range from the inexpensive portable “pyropen” type that uses butane
fuel and a catalytic burner to produce heat, to the sophisticated temperature controlled,
auto-timed, variable suction, multi-nozzle hot air systems that can cost you hundreds or
thousands of dollars.

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If you are on a tight budget, a handy device to get the job done is the “pyropen” or hot air
torch. These hot air, butane fueled, catalytic burner devices can be purchased for under
$100.00. To use this type of hot air device you have to ignite the torch, and adjust the
temperature. After it warms up place the nozzle tip about ¾ to 1 inch above the legs of
the IC you wish to remove. Move the nozzle tip around the IC to uniformly heat the IC’s
legs until the solder liquefies. Once the solder has liquefied use a dental pick or similar
device to lift the IC away from the board. As with other methods described here, practice
removing IC’s from a scrap board to hone your technique before you work on a
customers unit.