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Method to Shield the Exposed Sites Near a Chip During Encapsulation Of C-4 Chip Joints in a Second Level Packaging Assembly

IP.com Disclosure Number: IPCOM000102716D
Original Publication Date: 1990-Dec-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 2 page(s) / 80K

Publishing Venue

IBM

Related People

Tangirala, US: AUTHOR

Abstract

Disclosed is a method to prevent encapsulant flow onto the nearby sites when injecting the liquid encapsulant into the space between a chip and the carrier in a second level direct chip attachment process. It is sometimes required that these sites remain open for rework and other subsequent operations.

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Method to Shield the Exposed Sites Near a Chip During Encapsulation Of C-4 Chip Joints in a Second Level Packaging Assembly

       Disclosed is a method to prevent encapsulant flow onto
the nearby sites when injecting the liquid encapsulant into the space
between a chip and the carrier in a second level direct chip
attachment process.  It is sometimes required that these sites remain
open for rework and other subsequent operations.

      Encapsulation of C-4 chip joints is well established in the
first level packaging of chips in modules.  However, in a second
level packaging where a chip is directly attached to a printed
circuit board, the encapsulation of C-4 chip joints presents certain
problems unique only to second level packaging.  The method discussed
here addresses one such problem.  The benefits of second level C-4
encapsulation are the same as those for the first level packaging.

      The encapsulant material when dispensed along the edges of a
chip will not only flow under the chip as desired but also will
spread onto to surround areas including via-holes, etc.  The closer
the sites are to the chip the worse the problem.  Presence of cured
encapsulant material on these sites may render them inaccessible for
later steps such as rework.  This is unacceptable.  The method
discussed here proposes the use of a temporary barrier or a shield
these sites from the encapsulant.  After the encapsulation apply and
cure the barrier may be easily removed.

      The four key elements of this method are described below.
1. MASK MATERIAL:  A water-soluble liquid mask such as Techform
564-1* or similar material (see Fig. 1).  This...