Prince of Wales Secondary
Floor Location : M 029 N
This project, Conductive Glue, is an endeavour to find a safer, and possibly cheaper, alternative to solder as well as creating an easy-to-use enclosure that allows for straightforward application of the material. What resulted was a fairly viable alternative that did have some drawbacks, but also advantages compared to traditional solder.
Several different properties were tested for in Conductive Glue; resistance, operating temperature, melting point, adhesiveness, hardness, hazard and price.
Conductive glue has a resistance of at least 7?/cm at room temperature (23?C); substantially more than the 1.53 x 10-8 ?/cm solder exhibits. Its resistance also depends on how strong of a contact it has with wires; loosely attached wires have more resistance. The adhesive has an operating temperature of up to 45?C, higher temperatures will cause the resistance to increase five times (refer to figure 1.3), and between 60-70?C the adhesive will melt. When molten, the conductive glue has a very low viscosity (less than that of honey) and has a resistance of 50?/cm.
Solder, specifically tin/lead solder, is known for its wetting properties, those of Conductive Glue are similar, but do not hold just as well. The adhesive is also quite hard, similar to rubber, but also somewhat brittle. Stressing joints will create cracks. Compared to traditional solders, Conductive Glue is extremely safe. It melts at a lower temperature, and as no flux must be used to prepare the surface, there is no chance of it causing splatters of hot liquid. Due to its high thermal conductivity, the adhesive loses temperature very quickly, returning to a safe temperature in seconds, unlike solder, which must be avoided for a short time. As mentioned before, Conductive Glue does not contain any toxic chemicals nor releases fumes when heated. The materials for Conductive Glue add up to a mere $0.88 per kilogram.
At this point, Conductive Glue may be a good alternative to solder for beginners looking to learn electronics. Due to the brittleness of the glue, problematic joints can be removed easily without the use of special tools allowing for easy repairs. The compact size of the device allows the user to operate it with only one hand unlike standard soldering methods. The biggest drawback of the glue is its high resistance, which makes this solder alternative incompatible with sensitive components and high voltages.
A major advantage Conductive Glue holds over solder is cost and weight. Solder has a density of 8.5g/cm3 whereas Conductive Glue is 4.7 times less dense (1.81g/cm3). When bought in bulk, solder costs $13.50/kg which may seem cheap, until compared to the $0.88 worth of materials needed to produce one kilogram of Conductive glue. Coupling these facts together results in Conductive Glue giving 4.7 times more material at 15.3 times lower price.
Another benefit of Conductive glue is that any leftover scraps removed from a board can be collected and returned to the syringe. The syringe will melt those pieces, allowing them to be used again.