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Method for a CEK hat spring

IP.com Disclosure Number: IPCOM000101570D
Publication Date: 2005-Mar-16
Document File: 2 page(s) / 36K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for a common enabling kit (CEK) hat spring. Benefits include improved performance and improved reliability.

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Method for a CEK hat spring

Disclosed is a method for a common enabling kit (CEK) hat spring. Benefits include improved performance and improved reliability.

Background

      The hat spring included in the conventional CEK provides a 2-point load to the bottom of the motherboard. The hat spring has two load Loaf springs, which apply the load to the bottom of the motherboard and the four mounting bosses (see Figure 1).

      The use of the hat spring results in motherboard warpage and a varying load on the ball-grid array (BGA) balls. Modeling confirms that in some cases board warpage causes the balls in the outer rows of the socket to be in tension. This problem is a severe obstacle to passing validation testing (temperature cycle, shock, and vibration tests) and results in BGA joint and device failure.

      Conventional systems have light heatsinks that are mounted to the motherboard and do not use an under-board hat spring. In larger systems that have very heavy heatsinks, the heatsinks must be attached to the metal chassis or chassis pan to be adequately supported and pass shock and vibration testing.

Description

      The disclosed method applies a uniform heatsink load to the backside of the motherboard under the socket BGA pattern. The method uses a hat spring to provide the thermal interface material (TIM) load from the underside of the motherboard.

      The objective is to provide the same compressive force on each ball of the socket despite variations due to board bending (flexure).

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