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Formation of a Solder Ball On Pin Grid Array and Subsequent Attachment To Single or Multiple Chip Module on Laminate

IP.com Disclosure Number: IPCOM000116224D
Original Publication Date: 1995-Aug-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Howland, SR: AUTHOR [+4]

Abstract

Disclosed is a method for forming a solder ball on the head of a pin in a Pin Grip Array (PGA) and the subsequent attachment to a

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This is the abbreviated version, containing approximately 85% of the total text.

Formation of a Solder Ball On Pin Grid Array and Subsequent Attachment
To Single or Multiple Chip Module on Laminate

      Disclosed is a method for forming a solder ball on the head of
a pin in a Pin Grip Array (PGA) and the subsequent attachment to a

Single or Multiple Chip Module on Laminate (SCM/MCM-L) through the
traditional C4 ( Flip Chip) process.

      By designing a countersunk recess in the top surface of a PGA,
a cavity is formed around the head of each pin.  Solderpaste is then
screened through a stencil into the cavities to a particular metered
height and volume.  The volume of solderpaste is controlled by the
geometry of the countersunk cavity and the characteristics of the
screening process like screen thickness, stencil geometry, solder
viscosity, and extrusion pressure.  The geometry of the countersunk
cavity may be cubic, conical, spherical, or variations thereof with
the specific shape being based on the application requirements.

      Subsequent reflow of the solderpaste will create the formation
of a ball of solder formed around the pin head.  The actual shape of
this ball is a function of the cavity geometry and the screening
parameters and is of a substantially spherical geometry.  During the
reflow operation, the recessed cavity around the pin head controls
and contains the molten solder.  A solder ball is formed around and
on top of the pin head due to the subsequent wetting and capillary
tension of the constrained molten solder...