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Method for a preloaded buckling beam LGA contact

IP.com Disclosure Number: IPCOM000008977D
Publication Date: 2002-Jul-26
Document File: 3 page(s) / 230K

Publishing Venue

The IP.com Prior Art Database

Abstract

Method for a preloaded buckling beam land grid array (LGA) contact. Benefits include improved performance.

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Method for a preloaded buckling beam LGA contact

Method for a preloaded buckling beam land grid array (LGA) contact. Benefits include improved performance.

Background

              Contacts must be able to achieve relatively constant normal force at all socket contact locations under all the manufacturing conditions and be manufactured in high volume at low cost. Conventionally, the package is overloaded to ensure minimum contact force is achieved at all locations. However, overloading the substrate may cause side effects, such as board bending and die cracking.

General description

              The disclosed method is an LGA-type contact design where the contact is a vertical arch-shaped beam. The beam is preloaded with a predetermined force from another leaf spring at the center section. The top part of the beam mates with an LGA package. As an LGA substrate is loaded on the socket in the downward direction against the tip of the beam, the beam exerts a reaction force against the preloaded spring. Initially, the reaction force is less than the preloaded spring force, and the beam deflects very little. When the reaction force is greater than the preloaded force, the spring begins to deflect and, in turn, allows the beam to buckle. The contact beam becomes softer and enables more displacement.

              The spring preload is set to a value so that a minimum contact mating force is generated. When that force is reached, the beam deflects at a lower spring rate. The net result is a uniform distribution of contact mating force over the entire contact field.

              The key elements of the method include:

·        The preloaded contact deflects very little when initially mated with an LGA package until the designated contact mating force is reached. Then, the contact beam begins to deflect at a much lower spring rate.

·        The arrangement of the vertical arch-shaped beam and the preloaded spring causes the beam to buckle in the middle section under load.

·        The position of the stop and plastic bump controls the amount of preload.

Advantages

              The disclosed method provides advantages, including:

·        Reduced initial displacement due to achieving minimum contact mating force quickly

·        Improv...