Definition:

A weld generated between two metals by passing electrical current through them.

How does it work?

The resonator base and can are aligned and brought together in copper alloy dies in a nitrogen environment. Squeeze pressure is applied with a pneumatic ram and one or more pulses electricity are passed through the assembly.

The applied voltage is low but the current capacity can be hundreds of amps. The resistance of the assembly is slightly higher at the join between the base and can helped by a small weld projection on the base.

The area of highest resistance generates more heat, which in turn increases its resistance and as a result the temperature climbs rapidly melting the joint.

This all happens in a fraction of a second thus limiting collateral degradation of the contents.

Getting the desired result:

Amazingly good results can be obtained with this type of system.
It can be set up to produce very consistent welds but a great deal of care is required in setting up the optimum weld schedules and die alignments.

Sufficient pressure is required to eliminate plasma but not too much which can distort the holder assembly and wear out the dies. A leak free component is not good enough in itself, this must be achieved with the minimum of frequency change in the resonator and physical distortion of the assembly.

Poor weld conditions not only can cause frequency shifts, they are a major contributor to long term aging due to trapped weld gases and weld stresses to the assembly.

Features:

• Low cost hardware
• Consistency
• High temperature resistance
• Mechanically rugged
• High throughput
• Relatively large interior volume