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Method for folding and bonding a flexible substrate package

IP.com Disclosure Number: IPCOM000126988D
Publication Date: 2005-Aug-16
Document File: 5 page(s) / 420K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for folding and bonding a flexible substrate chip scale package (aka folded packages). Benefits include improved functionality, improved performance, and improved throughput.

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Method for folding and bonding a flexible substrate package

Disclosed is a method for folding and bonding a flexible substrate chip scale package (aka folded packages). Benefits include improved functionality, improved performance, and improved throughput.

Background

              Conventionally, manufacturing folded packages presents several problems, including the following:

•             Lack of an automated process for bonding and folding the flexible substrate package

•             Low units per hour throughput

•             Limited parallelism and scalability

•             High jig & fixture cost because fold jigs are placed inside a cure oven for 1 hour or more for adhesive bonding•              Poor adhesive bonding control due to the lack of an equal bond force applied to each unit due to a common bonding headpressing onto multiple units, where taller units receive high bond force while shorter units receive less bond force.

              Tight dimensional tolerances and process requirements for the folding process include the following:

•             +/- 0.050-mm package length, width, and solder ball-to-package edge offset

•             +/- 0% to 10% adhesive coverage (adhesive near edge of package, but no adhesive bleedout)

•             Capability to precisely control and adjust the fold shape, such as over-fold, under-fold, and fold radius

              Conventionally, folding is accomplished using a metal fold jig that closes like a book onto the pre-dispensed device. Various designs are available that hold four to six units per jig. A vacuum dispenser is used to apply adhesive. An air cylinder is used to achieve linear motion. After the jig is closed to fold the device, the entire jig is loaded into a curing oven with an electric heater element for 1 hour at 175ºF.

General description                                                                                                                                  

The disclosed method enables the folding and bonding of an flexible substrate package. The key elements of the method include the following:

•                   Apply adhesive to the unfolded device.

·        Place each devices in a holding jig to secure device to the folding operation.

·        Half of each device is held in the jig using mechanical or vacuum restraint, while the remainder to be folded is unrestrained.

•     Single heated fold/bond head that performs both the folding process and the thermal adhesive bonding process

•     Semiconductor package with a center portion that is a flexible substrate

•     Defined sequence of vertical and horizontal motions applied to the device holding jig and/or the heated bonding head

•     Thermal application and curing of adhesive

Advantages

              The disclosed method provides advantages, including:

•             Improved functionality due to providin...