Hybrid Oscillator Circuits
The final product appears as either a rectangular or a square cavity module on a can capped gold header. Inside the module is a ceramic substrate containing semiconductor chips, transistors and diodes, capacitors, and inductors. The addition of a crystal blank into this combination of active and passive electronic components completes the oscillator circuit.
Processing typically starts with the mounting of the various components into the ceramic substrate. Interconnections between components or between components and substrate are made with gold wire of varying sizes from 0.7 mil to 1.3 mil on either a Kaijo or a K&S automatic gold ball wire bonder. Additional capacitors, inductors and pins which do not require gold wire connections are subsequently mounted to form what can be considered as the semi-final circuit after this step.
The substrate is mounted into the final assembly casing or what is commonly called as headers by means of conductive epoxy material. Several electrical continuity tests are performed after substrate mount to ensure good circuit connection.
The most intricate processes involved in this operation are in the crystal blank (scrub and etch) preparation. Crystals are sorted by the measured frequency levels. Blanks are base plated to a predetermined thickness of silver deposit. Once the crystal is mounted on the oscillator assembly, a final plate operation is performed to get at the correct frequency target. Each of these steps is done with very high precision customized equipment.
Parts are hermetically sealed on resistance welders at super dry sealing conditions to ensure no residual moisture is detectable inside the cavity. Hermeticity is guaranteed to meet leak rates at magnitudes below 1 X 10 -8 atm-cc/sec.
Finished products undergo 100% parametric testing and visual inspection prior to shipment