Interconnect Assemblies With Wiping Contact Pads

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Solution Overview

Problem

Existing bumped flex circuit interconnect devices suffer from reliability issues due to lack of wiping action and low contact stress between conductive bumps and contact pads, leading to open circuits and high resistance.

Innovation Solution

The design incorporates conductive contact bumps with lateral portions that wipe against abutment zones on conductive contact pads, preventing contact at the distal end to enhance wiping action and contact stress, thereby improving reliability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the distal end of the conductive contact bump contacts the contact pad, then electrical connection is established, but wiping action is insufficient and contact stress is low leading to reliability problems

Engineering Contradiction:

Improvecontact reliabilityVSAvoidwiping action

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The contact interface is segmented into two distinct contact zones: the lateral portion of the bump contacts the abutment zone for wiping action, while the distal end is prevented from contacting the contact pad. This segmentation separates the wiping function from the electrical connection function, allowing each to be optimized independently.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of allowing the distal end (tip) of the bump to contact the pad as in conventional designs, the invention inverts the contact mechanism by using the lateral portion for contact. The abutment zone is positioned to engage the lateral surface of the bump, reversing the typical point-contact approach to achieve line-contact wiping action.

Inventive Principle:

Principle #13The other way round (Inversion)

2Reliability

If contact stress between bump and pad is increased, then electrical connection reliability improves, but risk of damage to conductive materials increases

Engineering Contradiction:

Improvecontact stressVSAvoidmaterial damage resistance

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The abutment zone is designed with specific local properties - it provides a controlled contact surface that distributes stress along the lateral portion of the bump rather than concentrating it at the distal end. This local quality enhancement allows high contact stress for reliability while preventing material damage through stress distribution.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The abutment zone acts as a cushioning element that prevents excessive stress concentration. By engaging the lateral portion of the bump, it distributes the contact force over a larger area and prevents the distal end from experiencing damaging point loads, thus cushioning against potential material damage before it occurs.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This configuration enhances contact reliability and robustness against contaminants and oxides, providing improved electrical connections with higher contact stress and reduced risk of damage to the conductive materials.

Implementation Method 1

wiping lateral portions of a plurality of conductive contact bumps of at least one bumped flex circuit assembly against of a plurality of conductive contact pads

Methodology Applied

Scientific EffectFriction: Friction

Implementation Method 2

the abutment zone is sized to allow contact of the lateral periphery, and prevent contact of the distal end, of the conductive contact bump disposed within the hole therewith

Methodology Applied

Scientific EffectNormal force: Force

Data Source

PatentUS7452214B2Interconnect assemblies, and methods of forming interconnects, between conductive contact bumps and conductive contact pads

Publication Date: 2008.11.18 ADVANTEST CORP

AI summary

In one embodiment, an interconnect assembly includes conductive contact bumps extending from a bumped flex circuit assembly, and conductive contact pads attached to a rigid printed circuit assembly. Each conductive contact pad has a contact surface having a hole and an abutment zone adjacent to the hole, wherein the contact surface is sized to allow contact, prior to disposition within the hole, by the distal end of one of the bumps, and wherein the abutment zone is sized to allow contact of the lateral periphery, and prevent contact of the distal end, of the bump disposed within the hole. A method of forming an interconnect is also disclosed. In one embodiment the method includes wiping lateral portions of conductive contact bumps against conductive contact pads, and abutting lateral portions of the bumps against the pads without contacting distal ends of the bumps.