Resistance welding is commonly used in electrical and electronics industry for joining components of various (often good conductive but more difficult to weld) materials and shapes such as electrical connectors, rotors, and printing circuits etc.
The special features of the resistance welding applications in electrical and electronic industry are characterized with miniature sizes and exotic materials which are very difficult to weld.
In order to support the industrial applications in electrical and electronics industry, special materials have been added to the build-in material database including silver, copper alloys and nickel alloys etc. To facilitate simulation of miniaturized components, the allowable dimensions in SORPAS® have been extended 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 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.
To get a successful bonding by parallel gap welding, part geometry is important to localize the current flows. Parts made in electrically resistive materials such as nickel and steel alloys can be easily welded to the same alloys. If the thickness of the top part exceed 0.15 mm, it is necessary to use special geometry design at the top part, since very little weld current flows through the bottom part in this case. Electrically conductive materials such as aluminum or copper is much more difficult for parallel gap 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 control the weld current and make enough weld heat, below two techniques are mostly used:
- Add slots to block the direct weld current path in the tap part.
- Add projections to localize the current through the desired path.
Micro joining of a fork to a wire is commonly used 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 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. First step of force is applied until the deformation of the fork is enough to close the initial gap towards the wire. After setting up a sound contact between the fork and the wire, first current pulse heats up the fork legs and at the end of the first current pulse, the tip of the fork legs are closed. Second pulse with increasing the applied load results sufficient heat to melt the polymer coating and electrical contact between the fork and the wire.