Browse Prior Art Database

Method for an anchored IHS BGA package

IP.com Disclosure Number: IPCOM000009287D
Publication Date: 2002-Aug-14
Document File: 7 page(s) / 273K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for an anchored integrated heat spreader (IHS) ball grid array (BGA) package. Benefits include improved thermal & mechanical performance.

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Method for an anchored IHS BGA package

Disclosed is a method for an anchored integrated heat spreader (IHS) ball grid array (BGA) package. Benefits include improved thermal & mechanical performance.

Background

              BGA-package trends are smaller pitches, larger packages, and a die size to enable higher I/O count density. This approach has led to solder joint reliability and package coplanarity issues. As in the development of 1-mm pitch, 42.5-mm package size, package assembly faced a package coplanarity issue with coplanarity exceeding the 8-mil specification. The assembled package on the board revealed a solder joint reliability issue. A brittle fracture (Figure 1) on the solder joint at package corner and fatigue fracture (Figure 2) at the die shadow solder joints. These issues are common within the industry with BGA applications.

              IHSs are conventionally used to solve the package coplanarity issue. Several approached are used in solving the solder joint reliability issue. Wave soldered heatsinks (Figures 3 and 4) improve the solder joint strength at the package corner while die shadow failure was solved by implementing the optimum package solder resist opening (SRO) to board pad size ratio that moves the stress to the middle of the solder joint. Underfill is another option in strengthening the BGA solder joint. Glue at the four corners of the package holds the solder joints at the corner when the board is flexed.

              Preload attached to the BGA packages is conventionally used to distribute the stress evenly across the whole package and requires special characterization.

General description

              The disclose method is an integrated solution for solder joint strength enhancement and package coplanarity elimination. The solution is ready for use in any system without further characterization while guaranteeing a reliable solder joint and providing a plug-and-play feature.

      An anchored IHS attaches to a BGA package (see Figure 5) and can be soldered to the board like a surface-mount (SMT) component. The IHS package helps eliminate package coplanarity and strengthens BGA solder joints by anchoring the IHS to the board at its four package corners.

              The key elements of the method include:

·        BGA package

·        Anchored IHS with an SMT anchor at four corners

·        Copper pad for anchored IHS on a PCB

Advantages

      The disclosed method provides advantages including:

·        Improved performance due to reduced coplanarity

·        Improved solder joint reliability

·        Simplified rework procedure

Detailed description

              The disclosed method includes a package design that integrates two features that solve the package coplanarity and solder joint reliability issues. These two features are an IHS for package coplanarit...