Browse Prior Art Database

METHOD OF CRYSTAL MOUNTING IN HIGH SHOCK ENVIRONMENT

IP.com Disclosure Number: IPCOM000005578D
Original Publication Date: 1985-Oct-01
Included in the Prior Art Database: 2001-Oct-17
Document File: 2 page(s) / 83K

Publishing Venue

Motorola

Related People

Richard J. Fedorowicz: AUTHOR

Abstract

Previous methods of mounting crystals in portable radios and pagers permit shock amplification and second- ary impact on the crystal when a radio is dropped, resulting in catastrophic failures. The proposed mounting method rigidly supports the crystal package, preventing the shock level from being amplified.

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MOTOROlA Technical Developments Volume 5 October 1985

METHOD OF CRYSTAL MOUNTING IN HIGH SHOCK ENVIRONMENT

by Richard J. Fedorowicz

   Previous methods of mounting crystals in portable radios and pagers permit shock amplification and second- ary impact on the crystal when a radio is dropped, resulting in catastrophic failures. The proposed mounting method rigidly supports the crystal package, preventing the shock level from being amplified.

   The prior method of mounting tubular AT-strip crystals on radio PC boards is shown in Figure 1. The crystal is inserted into a rubber boot and subsequently soldered to the PC board. This type of mounting allows terminals to break during a radio drop test, sometimes permitting the crystal to hit adjacent components. This crystal package displacement during the radio drop test results in catastrophic crystal failures due to the phenomenon of shock amplification. Shock amplification is a result of velocity addition due to the crystal motion being in the opposite direction of the radio rebound. As shown in Figure 1, the complete radio assembly will attain a final velocity Vi at impact, and it wilf rebound with a velocity V,. The crystal, however, because of its flexible mount, will be sub- jected to the effects of both velocities (Vi and V,) added together. Thus, while the radio is subjected to approx- imately 4,000 g's shock, this "whiplash" effect imparts shock levels above 10,000 g's to the crystal. AT-strip crystals in the 3xamm...