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Photo Defined Lamination for Chip Bonding

IP.com Disclosure Number: IPCOM000050137D
Original Publication Date: 1982-Sep-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 45K

Publishing Venue

IBM

Related People

Edwards, JC: AUTHOR

Abstract

This article involves the use of photo definable polyimide as a thin film solder dam when bonding integrated circuit chips with solder balls at the output pads to beam tape. A thin film of photo definable polyimide is coated or applied over copper beam tape material on which pads and interconnecting leads have been masked and etched. A further masking and material removal process is then applied to the photo definable polyimide layer, creating via holes for access to the copper inner lead pads. These exposed pads may then be gold plated without further masking steps. In assembly, the photo defined holes provide for easy alignment of the chip to the tape, while during reflow soldering the polyimide coating provides an efficient solder dam.

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Photo Defined Lamination for Chip Bonding

This article involves the use of photo definable polyimide as a thin film solder dam when bonding integrated circuit chips with solder balls at the output pads to beam tape. A thin film of photo definable polyimide is coated or applied over copper beam tape material on which pads and interconnecting leads have been masked and etched. A further masking and material removal process is then applied to the photo definable polyimide layer, creating via holes for access to the copper inner lead pads. These exposed pads may then be gold plated without further masking steps. In assembly, the photo defined holes provide for easy alignment of the chip to the tape, while during reflow soldering the polyimide coating provides an efficient solder dam.

Fig. 1 shows the chip 1 with a passivation layer 3 and a solder ball at an output pad brought into initial alignment with the beam tape in which a via 5 has been exposed and etched in the photo defined polyimide layer. Contact is made, as shown in Fig. 2, with via 5 aiding in alignment by physically directing the solder ball. Fig. 3 shows the final connection, after reflow soldering.

Fig. 4 shows a top view with dashed line 7 indicating the edge of one chip and solid lines showing copper leads and pads as seen through the polyimide overcoat. The underlying polyimide substrate is unbroken and may be indefinitely moved past bonding apparatus to connect a series of circuit chips 1. Ultimate...