Thursday, May 23, 2013

Circuit Bending Basics 5: On Desoldering SMD Resistors

This post assumes that you have read Circuit Bending Basics 1, 2, 3 and 4.

Circuit bending is about the non-thereoretical exploration of sound making circuits via shorting different points together. Take a toy (that is battery powered - important!) and let's get to work!

SMD Resistors
Sometimes, the clock resistor of a toy is easy to remove.

The resistor may be a through-hole resistor like this, and can be removed manually or by de-soldering easily. 

With other circuits, the clock resistor may be a tiny component - like those shown below - called "surface mount resistors". These are more difficult to remove and can prove to be a nuisance sometimes.

My method for removing these is as follows:
• The surface mount resistor has a body and two terminals.
• The aim of removing the resistor might be so that we can connect something in place of the resistor - in which case we need access to the two terminals
• Carefully heat up the area right next to and underneath the body of the SMD resistor with a soldering iron.
• You should notice that the body of the resistor becomes loose
• With a little force, flick the body with the soldering iron tip, thereby removing the body from the circuit board completely
• Add a little solder to each of the terminals that are left over
• Solder wires directly to the terminals, thereby creating easy access to the resistive points for substitution
• You can then replace the static resistor with a variable resistor (e.g. pot, digi pot, LDR, flex etc).