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Browse Prior Art Database

Low Cost Card Assembly Process for Fine Lead "SMT" Package

IP.com Disclosure Number: IPCOM000120678D
Original Publication Date: 1991-May-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 1 page(s) / 42K

Publishing Venue

IBM

Related People

Conru, H: AUTHOR [+3]

Abstract

A low-cost card assembly process for fine lead pitch "flat packs" and micro "A wire" modules is shown.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 100% of the total text.

Low Cost Card Assembly Process for Fine Lead "SMT" Package

      A low-cost card assembly process for fine lead pitch "flat
packs" and micro "A wire" modules is shown.

      Conventional vapor phase or infrared solder reflow techniques
utilized to perform module to card assembly become increasingly more
difficult when lead pitch designs fall below 0.025". A labor
intensive "hot bar" is applied to the module leads (gull wing) to
achieve lead planarity over a large area before solder reflow. By
bonding the module in place on the card prior to soldering, a less
expensive vapor phase reflow or equivalent heat cycle method may be
used.

      Referring to Fig. 1, the module is positioned onto the card by
means of a highly viscous flux placed on the soldered leads.  (The
leads are soldered by typical processes, i.e., solder paste, wave
solder, or immersion.) The module lead geometry is designed such that
the module can subsequently be pressed down, causing lead deflection
resulting in lead to pad planarity. Fig. 2 shows the module held in
position after being pressed down and contacting a quick setting
epoxy or tape. Fig. 3 shows the final attachment of module to card
after reflow through a vapor phase or equivalent heat cycle.

      Disclosed anonymously.