Dismiss
InnovationQ will be updated on Sunday, Oct. 22, from 10am ET - noon. You may experience brief service interruptions during that time.
Browse Prior Art Database

Technique for Assembly of Ultra Fine Pitch SMT Components to Enhance Placement and Minimize Coplanarity and Alignment Problems

IP.com Disclosure Number: IPCOM000112419D
Original Publication Date: 1994-May-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 83K

Publishing Venue

IBM

Related People

Senger, RC: AUTHOR

Abstract

Disclosed is a technique to allow deposition of solder on Surface Mount Technology (SMT) substrates which will enable the user to minimize coplanarity difficulties and enhance the ability to place and align ultrafine pitch SMT devices during the assembly of these components.

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

Technique for Assembly of Ultra Fine Pitch SMT Components to Enhance
Placement and Minimize Coplanarity and Alignment Problems

      Disclosed is a technique to allow deposition of solder on
Surface Mount Technology (SMT) substrates which will enable the user
to minimize coplanarity difficulties and enhance the ability to place
and align ultrafine pitch SMT devices during the assembly of these
components.

      Referring to Fig. 1, a copper SMT land 1 located on substrate 5
and surrounded by protective coating (procoat) 3 is modified by
depositing, by plating or evaporation techniques, a thin (flash)
coating of copper 2.  This flash copper 2, is then patterned by usual
printed circuit techniques to define a larger, coincident land which
will subsequently be dissolved into solder which will be deposited
for joining or assembly of an SMT device 6 (a typical quad flat pack
will be used in this discussion) to the substrate 5.

      Section A-A and section B-B indicate the crossection of the
land 1 and the flash copper 2.  By passing the substrate through a
wave solder process, solder 4 will be deposited on the land 1 and on
the flash copper 2 in a manner indicated in the sections A-A and B-B
by the phantom line.

      One skilled in the art will recognize that the height of the
deposited solder 4 will be a function of the width of the land 1 and
the flash copper pattern 2 and as such can be tailored to fit the
lead 7 pattern, size and shape.  By so doing, (Fig. 2) the quad flat
pack 6 leads 7 will seat into the "nest" defined by the solder 4
deposited on the patterned flash copper 2.  Because the quad flat
pack has leads on all four sides, the "nest" created by the solder
height at the ends of the lands contains the component a...