Resistance welding is commonly used in the electrical and electronics industry for joining components such as electrical connectors, rotors, etc. The materials of these components often have good conductivity, thus they are more difficult to weld. Together with the exotic materials, the miniature size of the components is a unique characteristic in resistance welding applications.
In order to support the industrial applications in the electrical and electronics industry, SORPAS® has special materials in the build-in material database including silver, copper alloys and nickel alloys, etc. To facilitate the simulation of miniaturized components, SORPAS® allows dimensions down to 0.1 microns (or 4 decimals for mm).
Parallel gap welding is a resistance welding process for bonding two parts together by placing both electrodes against the same surface on just one part. Weld current flows from one electrode through the top part and partially into the bottom part before returning to the power supply via the second electrode. Parallel gap welding is mostly applied in the manufacturing of battery packs, medical or automotive sensor wire to PCB, solar cells, hybrid or microwave circuitry, thin or thick film substrate, and fine line printed circuit trace repair.
Parts made in electrically resistive materials such as nickel and steel alloys are easy to weld to the same alloys. However electrically conductive materials such as aluminum or copper are much more difficult for welding. Because most of the weld current flows through the top parts, not into the bottom part. Also, the high thermal conductivity of these materials transfers the weld heat very quickly. To get a successful bonding by parallel gap welding, the geometry is important to localize the current flows. If the top part is thick, very little current flows through the bottom part. So it is necessary to use a special geometry design at the top part. To control the weld current and make enough weld heat, engineers are using below two techniques mostly:
- Add slots to block the direct weld current path in the top part.
- Add projections to localize the current through the desired path.
Micro joining of a fork to a wire is common application in the electronics industry. The resistance heating caused by the current facilitates the closing of the fork around the wire due to softening of the material. At the same time, the induced temperature melts the polymer coating locally on the wire to create an electrical connection between the wire and the fork, while the polymer keeps the remaining wire isolated.
In the simulation case, two pulses are applied with two-step forces. The first step of force is applied until the fork is enough to close the initial gap towards the wire. After setting up a sound contact between the fork and the wire, the first current pulse heats up the fork legs. At the end of the first current pulse, the tips of the fork legs are closed. The second pulse with the increased force generates enough heat to melt the polymer coating and electrical contact between the fork and the wire.