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Power Package with Thermal Tie-Bar Design

IP.com Disclosure Number: IPCOM000243122D
Publication Date: 2015-Sep-16
Document File: 3 page(s) / 186K

Publishing Venue

The IP.com Prior Art Database

Abstract

In some cases, especially for power devices, a package can’t meet its thermal requirement for device performance. Currently in SOIC and QFP packages, a tie bar is the only connection from flag to edge, and then all such area is filled with mold compound. If we take good advantage of the tie bar area, such as add a metal piece in this area, this area will turn into a high efficiency heat sink that is directly connected with the tie bar, and extends through the package from bottom to top, so thermal and power dissipation efficiency is expected to be high.

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Power Package with Thermal Tie-Bar Design

Abstract: 

In some cases, especially for power devices, a package can’t meet its thermal requirement for device performance. Currently in SOIC and QFP packages, a tie bar is the only connection from flag to edge, and then all such area is filled with mold compound.  If we take good advantage of the tie bar area, such as add a metal piece in this area, this area will turn into a high efficiency heat sink that is directly connected with the tie bar, and extends through the package from bottom to top, so thermal and power dissipation efficiency is expected to be high.

Body:   

The drawings show the heat transfer path for a conventional QFP and a proposed QFP with a tie-bar heat sink design.

The following steps outline how to assemble a tie-bar heat sink device.

1)  Metal piece is picked and placed on the tie bar (flat & slope areas) with high thermal epoxy as adhesive, where the height of the metal piece is equal to the package thickness;

2)  Metal piece is the same level as the corner lead tip to prevent obstructions to the wire bonder head during wire bonding.

3)  Simplified Process flow:  

1. Wafer plasma cleaning;

2. Wafer mount;

3. Wafer sawing;

4. Die attach to lead frame flag;

5. Metal pieces/heat sink attach

5. Wire bonding;  

6. Mold;

7. PMC (Post Mold Cure);

8. VM           

            The standard tie bar design of a conventional SOIC/ LQFP packages is modified by embedding two or more metal...