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A New Method of Compensating for BGA Package Warpage

IP.com Disclosure Number: IPCOM000209379D
Publication Date: 2011-Aug-02
Document File: 3 page(s) / 83K

Publishing Venue

The IP.com Prior Art Database

Abstract

The article proposes a new method for compensating BGA package warpage. The method is characterized of adding a solder paste deposition step on component side before component placement. The paste volumes deposited on component side are different depending on the thermal bending configuration of component body.

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A New Method of Compensating for BGA Package Warpage

There are usually two kinds of warpage, concavely-warped and convexly-warped for BGA packages or LGA/BGA socket when they are soldering to a board through reflow. They usually exhibit a thermal bending of smile face (concavely-warped) or cry face (convexly-warped) configuration during SMT reflow due to different CTE of substrate, die, plastic body.

The article proposes a new method of compensating BGA package or LGA/BGA socket warpage. The characterization of the method is adding a solder paste deposition step on component side before component placement, and the solder paste volume on selected solder balls are predetermined in accordance with premeasured warpage of BGA package or LGA/BGA socket. A profiled solder paste thickness is formed by combining deposited paste on component side and screened paste on PCB side, which just exactly compensate for the warpage of BGA package or LGA/BGA socket after thermal bending. Thus a full array contact of component solder-balls with PCB pads are achieved during SMT reflow, see Fig.1 and Fig.2 for details.

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The method can be achieved by using the following fixture design, see Fig.3 and Fig.4. The amount of solder paste deposited on selected solder balls can be controlled by the thickness and aperture of Upper Stencil 1 & 2.

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