Micro Welding – 7mil Stranded Coated Wire to PCB and 5mil Pt-Ir Cylinder

DCD320 – DC and CD resistance welder (high precision power supply)

MWH3000 – 3000g parallel micro weld head
/>Tungsten thermo-compression electrode (domed tip)
Opposed electrode holder base
1/8″ molybdenum electrode (tip stepped down to 0.025″
8awg weld cables

Coated Wires to PCB:
The parallel micro weld head is configured with a tungsten thermo-compression electrode and 8awg weld cables. The Force on the micro weld head is set to attach the wires to the PCB. The thermo-compression electrodes are ideal for applications with very thin substrate layers because they generate heat at the tip of the electrode and the force applied by the weld head compresses the molten material into contact with the substrate material (less energy passes through the thin PCB layer so damage is minimized). We used a ceramic plate as a backing support for the PCB.

The stranded coated wires are welded to the PCB using the DCD320 set with Pulse 1 at 20ms length, Pulse 2 at 30ms length, and Peak Voltage at 2.2v. This setting is able to attach the wire to the pad; but some of the surrounding board is melted and the pad sinks in slightly. We didn’t have many pads or wires to experiment with for dialing the ideal settings, but as you experiment further with energy, force, and weld length even better results may be achieved.

Coated Wires to Pt-Ir Cylinders:
The MWH3000 is used in a unique manner for this application to avoid the need to pre-strip the wire:

A parallel style upper electrode holder is used in conjunction with an opposed style lower electrode holder. This allows us to use the thermo-compression electrode and have a steady, adjustable base to hold the cylinder in place during the weld. We used a 1/8″ molybdenum electrode that is stepped down at the tip to 0.025″ diameter (to more easily fit the inner diameter of the cylinder and still accommodate the wire) positioned horizontally in the lower holder. The force on the weld head is changed to 2000g for these welds.

The platinum iridium cylinder is placed over the stepped down portion of the lower electrode and the non-stripped wire is inserted through the cylinder such that it lies between the electrode and the inner wall of the cylinder.

The DCD320 is set with Pulse 1 at 20ms, Pulse 2 at 30ms, and Peak Voltage at 2.8v. Resulting welds are strong and a continuity test shows that electrical contact is established between the wire and the cylinder.

The DCD320 and MWH3000 are capable of performing welds quickly and easily. The wire to PCB process may need additional tweaking of settings for best results.

Let us know if you have any questions.
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