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Dynamically Balanced Spring with Bottom-Mounted E-Spring Registration

IP.com Disclosure Number: IPCOM000012019D
Publication Date: 2003-Apr-02
Document File: 4 page(s) / 85K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method that introduces a new carrier spring geometry that equalizes the spring force from alternate pockets, and a leaf spring mounted under the carrier that registers the substrate in pocket. Benefits include a lower spring force difference between alternate pockets.

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Dynamically Balanced Spring with Bottom-Mounted E-Spring Registration

Disclosed is a method that introduces a new carrier spring geometry that equalizes the spring force from alternate pockets, and a leaf spring mounted under the carrier that registers the substrate in pocket. Benefits include a lower spring force difference between alternate pockets.

Background

Currently, an E-spring mounted on top of the bottom plate holds a substrate in a high temperature environment, during the factory assembly process operations. This E-spring provides force to register the substrate in the pocket created by the top plate.

To retain a substrate within the carrier pocket during processing, the current carrier E-spring uses two arches to supply independent force to substrates in alternate pockets. The spring does not adjust for placement tolerance variation, resulting in a high force in one pocket with the alternate pocket experiencing a low force.

General Description

Currently, metal carriers are used in processing semiconductor packages.� Each carrier contains numerous pockets (e.g. 8,10 or 12 pockets) in which packages are loaded using an Automatic Part Loader (APL) for high volume production, or with a manual part loader (MPL) for low volume production (i.e. design of experiments testing). The parts are restrained in the carrier by the force supplied from the E-spring (see Figure 1). The equipment capability is dependent on the accuracy and precision of the carrier. The equipment utilizes carrier features to precisely locate semiconductor packages for module processing.

The carrier spring legs are compressed to a dimension of 12.5mm. The resulting pocket opening must be sufficiently large for placing the substrate into the pocket. The standard design rule is a minimum pocket opening equal to the nominal substrate size plus .010”.� Insufficient pocket clearance results in a SOOP (Substrate out of pocket) occurrence.

The disclosed method’s new spring simplifies the assembly process by relocating all E-spring spot welds to the underside of the carrier (see Figure 2).� The result is a smoother top plate for CAM paste/p...