Browse Prior Art Database

Solder Preform Technique for Fine Pitch Surface Mount Technology Components

IP.com Disclosure Number: IPCOM000103945D
Original Publication Date: 1993-Feb-01
Included in the Prior Art Database: 2005-Mar-18
Document File: 2 page(s) / 96K

Publishing Venue

IBM

Related People

Nilsen, CO: AUTHOR [+2]

Abstract

A method for producing and using solder preforms for fine pitch Surface Mount Technology (SMT) component attach is disclosed. The discussion includes the production of preforms smaller than possible with conventional techniques and their usage in the attach process.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Solder Preform Technique for Fine Pitch Surface Mount Technology Components

      A method for producing and using solder preforms for fine pitch
Surface Mount Technology (SMT) component attach is disclosed.  The
discussion includes the production of preforms smaller than possible
with conventional techniques and their usage in the attach process.

      This approach to the use of solder preforms for fine pitch SMT
component attach involves the creation of a novel preform.  This
preform would use discrete islands of solder paste contained in a
non-wet carrier medium.  The problem of generating these small
discrete islands of solder would be minimized by using a screening
process to deposit solder paste into the cavities of the carrier
medium.  Due to the fact that this carrier medium would only need to
be the size of one component, all of the non-uniformity problems
associated with screening the paste on the much larger printed
circuit (PC) card would be minimized.

      The preform itself could be constructed in a number of ways,
dependent on the specific usage requirements.

      In the first embodiment (Figs. 1 and 2), the non-wet material
would be constructed of three parts:

      A) a carrier adhesive medium 1 to provide a solid plane for
structural rigidity of the preform barriers between the solder paste
4 islands,

      B) a solder carrier medium 2 to provide the overall structure
of the preform and the barrier between the solder paste 4 islands
when placed on the PC Card,

      C) and the removable solder paste height medium 3 used to
define the screened height of the solder paste 4 and removed before
attachment to the PC Card.

      In this embodiment, the flux used in the solder paste could be
a "no clean" flux and the carrier adhesive medium would be removed
after the preform was placed on the PC Card.  The component would
then be placed on the preform and the site reflowed using a standard
hot air rework tool or equivalent.

      In the second embodiment (Figs. 2 and 3), the non-wet portion
of the preform would again consist of three parts.  In this case,
however, the solder paste 4 would be reflowed with all three non-wet
portions of the...