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SHOCK ABSORBING SLEEVE FOR CRYSTAL OSCILLATORS

IP.com Disclosure Number: IPCOM000006291D
Original Publication Date: 1991-Dec-01
Included in the Prior Art Database: 2001-Dec-20
Document File: 1 page(s) / 59K

Publishing Venue

Motorola

Related People

Hiroyuki Kanda: AUTHOR

Abstract

Crystal oscillators are often used in portable com- munication electronic equipment such as pagers. Due to the nature of use of pagers, the crystal oscillator must be protected from mechanical shock caused by the pager being dropped, thrown, etc. Previously, the crystal oscil- lators were placed on the unit's Printed Circuit (PC) board and epoxied into place. The problem generated by this method was only the sides were epoxied down. The bottom of the crystal oscillator was touching the PC board. When a pager using this method is dropped, the waves from the shock pass through the pager hous- ing and into the PC board. The PC board begins to vibrate from the shock thus beating against the bottom of the crystal oscillator. The resulting shock waves may have magnitudes of up to twice the magnitude of the shock waves in the pager housing. A natural result is failure of the crystal oscillator.

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MOTOROLA INC. Technical Developments Volume 14 December 1991

SHOCK ABSORBING SLEEVE FOR CRYSTAL OSCILLATORS

by Hiroyuki Kanda

  Crystal oscillators are often used in portable com- munication electronic equipment such as pagers. Due to the nature of use of pagers, the crystal oscillator must

be protected from mechanical shock caused by the pager being dropped, thrown, etc. Previously, the crystal oscil- lators were placed on the unit's Printed Circuit (PC) board and epoxied into place. The problem generated by this method was only the sides were epoxied down. The bottom of the crystal oscillator was touching the PC board. When a pager using this method is dropped, the waves from the shock pass through the pager hous- ing and into the PC board. The PC board begins to vibrate from the shock thus beating against the bottom of the crystal oscillator. The resulting shock waves may have magnitudes of up to twice the magnitude of the shock waves in the pager housing. A natural result is failure of the crystal oscillator.

  To avoid the vibration problems, manufacturers of pagers have begun inserting the crystal oscillator into a silicon sleeve. This sleeve is effective in reducing the shock on the oscillator. However, such sleeves must be

custom fit to each element. There is no flexibility as to how many elements may be included or how big or little the elements may be. For each size of element, or each number of elements, a new sleeve must be made.

  Figure 1 shows a firs...