Samples for WE Salesmen
1. Quartz bar (synthetic quartz which is grown in an autoclave).
The quartz bar is cut up at the correct angle depending upon the stability/temperature range required.
The quartz slices are then processed into round or rectangular ‘blanks’.
These blanks are then ground, lapped and polished to the correct thickness for the frequency where
Freq [Hz] = 1680/thickness [m]
HC49 quartz blank: this is a larger older style crystal package that uses round blanks.
HC49/4H or HC49/4HSMX quartz blank: smaller crystals use “strip resonators” which are rectangular.
Metal electrodes are plated onto the quartz crystal blank using a mask to shield the quartz and give the correct electrode size and shape. The electrodes are usually silver.
HC49 crystals with electrode plating.
HC49/4H or HC49/4HSMX crystals with electrode plating.
HC49 Base (ready for mounting quartz)
HC49/4H Base (ready for mounting quartz)
Mounting and bonding, plus final adjustment
The quartz blanks with electrodes are mounted in a holder using silver loaded conductive epoxy glue. The crystals are individually mounted into a “Final Adjustment” machine where the frequency is read while further metal is deposited as a spot on to the electrode; when the frequency is within the tolerance value then the process stops.
HC49 with quartz mounted, bonded and with final adjustment
HC49/4H with quartz mounted, bonded and with final adjustment
The metal lid is placed over the crystal and is resistance welded to the metal base to seal it. This is done in a nitrogen atmosphere so no oxygen is present in the final cavity which helps reduce the ageing of the crystal.
HC49 finished and ready for marking
HC49/4H finished and ready for marking