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Method for a heat spreader for a FCBGA

IP.com Disclosure Number: IPCOM000011838D
Publication Date: 2003-Mar-19
Document File: 4 page(s) / 161K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for a heat spreader for a flip-chip ball grid array (FCBGA). Benefits include improved thermal performance.

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Method for a heat spreader for a FCBGA

Disclosed is a method for a heat spreader for a flip-chip ball grid array (FCBGA). Benefits include improved thermal performance.

 

Background

              A FCBGA is a very small package with a small die (see Figure 1). Heat is transferred to the environment through tiny thermal vias only. As a result, the junction temperature for the package is extremely high.

              No conventional components exist on the back of the substrate. That space is available for heat spreader attachment.

              Heat is transferred from high temperature to low temperature. Heat is generated by the die and transferred to the surrounding area through conduction and to the surrounding environment through convection.

General description

              The disclosed method is a heat spreader for an FCBGA. It is a die down package configuration. The die and the solder joints are located on the same side of the package. Therefore, the heat spreader attaches on the back of the package for improved thermal performance.

 

              The key elements of the method include:

•             FCBGA (die down package configuration)

•             Heat spreader

Advantages

              The disclosed method provides advantages, including:

•             Improved thermal performance due to the addition of a heat spreader at the back of the package to provide addition surface for heat dissipation, reducing the die junction temperature

Detailed description

              The disclosed method is a heat spreader for an FCBGA. By adding a heat spreader to the back of the substrate, the heat transfer area significantly increases (see Figure 2).

              Basic heat transfer through convection is represented by the following equation where, h = heat transfer coefficient, A = heat transfer area, and dT = temperature differences:

              Heat transfer is directly proportional to the heat transfer area. As the heat transfer area is increased, the heat dissipation increases.

              Resistance is a factor in heat transfer. Resistance occurs in air, thermal vias, and the die for the conventional solution. For the disclosed solution, resistance occurs in the heat spreader, thermal vias, and the die (see Figure 3).

              Assuming heat transfers only in one direction through a copper heat spreader and the environment temperature is maintained at 30°C, one-dimensional calculation can be perfor...