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Browse Prior Art Database

Method of Backsealing a Module Without Encapsulation of Pins

IP.com Disclosure Number: IPCOM000035258D
Original Publication Date: 1989-Jun-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 2 page(s) / 57K

Publishing Venue

IBM

Related People

Ameen, JG: AUTHOR [+5]

Abstract

Whenever a module contains "C"-shaped pins on the sealing surface, any effort to seal that layer, i.e., surface, with the sealing epoxy, particularly SCOTCHCAST*, resulted in the pins becoming embedded in the epoxy, thereby reducing the compliancy of these pins. This encapsulation of the "C"-shaped pins is caused by the capillary action of the Scotchcast on the pins. Anytime the epoxy touches a pin, by capillary action, it moves up and over the pin like a "wick".

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Method of Backsealing a Module Without Encapsulation of Pins

Whenever a module contains "C"-shaped pins on the sealing surface, any effort to seal that layer, i.e., surface, with the sealing epoxy, particularly SCOTCHCAST*, resulted in the pins becoming embedded in the epoxy, thereby reducing the compliancy of these pins. This encapsulation of the "C"-shaped pins is caused by the capillary action of the Scotchcast on the pins. Anytime the epoxy touches a pin, by capillary action, it moves up and over the pin like a "wick".

In accordance with the present method, a polyimide sheet is provided with 30-mil holes in a fully populated pattern in order to accommodate all part numbers for a particular module (see Fig. 1). In addition, a dispense hole is put into this sheet for epoxy dispensing (see Fig. 2). This sheet can be obtained in pre-punched form, to keep the cost to a minimum and can be made of paper, TEFLON** or other material. Once obtained in pre-punched, roll form, the method is as follows:

1)Pin the module as usual.

2)At the reform operation, a roll of the material is set up to index with the parts as they are dropped into the reform tool. When a part drops into position in this tool, the pins of the substrate go through the polyimide. During the reform operation, the polyimide is punched from the roll and is fixed in place below the newly formed "C" pins.

3) The parts now may be sealed by placing the epoxy, e.g., SCOTCHCAST, using the normal process with th...