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Coplanarity compensating features on SMT leads

IP.com Disclosure Number: IPCOM000199597D
Publication Date: 2010-Sep-10
Document File: 3 page(s) / 35K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a system to add compensating features to Mounted Technology (SMT) leads in order to absorb gaps between printed circuit board (PCB) pads and contacts and act as wicking agents.

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Coplanarity compensating features on SMT leads

Lengthy Surface Mounted Technology (SMT) connectors have known issues with lead

coplanarity. These include future designs that are lengthier and have more pins,

compounded by allowable printed circuit board (PCB) warp. Also, an open solder joint

is a common failure.

The disclosed solution adds compensating features to SMT leads in two forms. These

features absorb gaps between PCB pads and contacts and act as wicking agents. Solution form #1 involves adding a blind via to PCB pads and adding a short lead stub

to the SMT lead. It is not necessary to plate or have stringent quality controls, and this

provides a simple solder collection mechanism. In addition, the approach modifies the

SMT lead to include a solder wicking feature, which includes the following:
• Stub contact
• Short as to not affect signal integrity
• Long enough to compensate for 2x normal coplanarity
• No additional cost to contact stamping


Solution form #2 adds a low contact normal force (<10g) spring member to the SMT

lead. The advantages of this solution are:
• Pick and place equipment can easily overcome spring force
• No additional cost to contact stamping
• Spring member acts as wicking agent


In essence, to compensate for non-coplanarity in lengthy card edge connectors such as

DIMM (dual inline memory module) sockets, the solution adds protrusions to the solder

leads that correct for warped thermoplastic housings, contact assembly variatio...