Browse Prior Art Database

Shouldered Leads for Surface-Mounted Components

IP.com Disclosure Number: IPCOM000101606D
Original Publication Date: 1990-Aug-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 2 page(s) / 57K

Publishing Venue

IBM

Related People

Burton, SG: AUTHOR

Abstract

Disclosed is a new cross-section geometry for surface-mounted leaded components to better their second-level packaging strength/reliability.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 78% of the total text.

Shouldered Leads for Surface-Mounted Components

       Disclosed is a new cross-section geometry for
surface-mounted leaded components to better their second-level
packaging strength/reliability.

      One problem associated with using surface mount technology is
the reduced strength of surface mount solder joints compared with
pin-in-hole solder joints.  Stress testing has shown that surface
mount joints develop cracks under smaller test loads than pin-in-hole
joints.  A common area for cracks to occur in surface mount joints is
the interface between the component lead and the solder. Strength at
this interface is usually the weakest part of the joint.

      This article presents a means for strengthening the
solder/component lead interface.  The geometry of the present
interface has a flat component lead sitting on a flat solder surface
(see Figure 1).  During reflow, the solder wets to the component lead
and forms a solder joint. When the lead/solder interface is the
weakest part of a solder joint, the wetting/bonding strength is the
strength of the joint.  This article changes the component lead
cross-section to create mechanical retention strength to supplement
the bonding strength of the solder/lead interface.

      The cross-section of surface mount components leads would have
shoulders that solder would flow around during the reflow operation.
When the solder solidifies there would be an interlocking action
between the component lead and the...