Commonly used quartz crystals are manufactured in a wide variety of hermetically sealed package types, all containing a quartz plate with electrodes, mounting structure, leads or pads used for attaching the device mechanically and electrically to the circuit.
Holders have evolved over the past three generations from very large vacuum tube, bake-lite, porcelain and finally in the 1940s to hermetically (solder) sealed metal holders. Their large size was a function of the technology and frequency range of the period. As the frequency of electronic designs increased, the size of metal packages decreased in accordance with the available quartz blank geometry. In the 50s and 60s the technology further evolved allowing the development of even smaller metal holders, "HC Types", with improved hermetic sealing methods of resistance- weld and cold-weld packages. High shock and vibration applications let to the development of "TO Type packages shared with the semi-conductor industry. Continued development in the 80s and 90s has driven the size of metal leaded packages even smaller with the introduction of UM-1, UM-4, UM-5, HC-45 and HC-52 packages.
In the 60s glass holders were developed for high-precision resonators, but improvements in metal holders have almost completely eliminated the need for glass packages.
With the introduction of the quartz watch in the 70's, tubular holders were developed, but their use is typically restricted to low frequency timing applications at 32.768 KHz.
In the 80's the industry made its first attempts at surface mount holders. Initially the SMT devices were metal holders with formed leads or pads added to the base. Eventually SMT were developed in plastic and ceramic packages. With new developments in wafer technology and the requirement for machine placement, size is constantly being driven downward and the frequency upward. Popular SMT crystals today are 2.5 mm X 5 mm and 5 mm X 7 mm using strip technology.
METAL HOLDERS- "HC" TYPES:
HIGH-PRECISION COLD-WELD METAL HOLDERS:
AE131 - 5 MM X 7 MM SMD:
AE232 - 3.2 X 6 MM SMD:
AE100 - .320 SQ. SMD:
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