Chisel-Tip Probe Assembly for QFP Test Reliability
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Solution Overview
Problem
Test tooling for packaged integrated circuits (IC) devices experiences reliability issues due to wear and tear, leading to inconsistent electrical connections and increased retest rates, especially in high-density Quad Flat Pack devices with edge-mounted pins, where grounding connections are prone to crosstalk and signal distortion from resistive changes.
Innovation Solution
A test probe assembly with a plurality of probes and a termination pad interposer that ensures repeatable alignment and mechanical support, incorporating reactive elements to cancel parasitic reactances, and featuring probes with angled tips for improved contact reliability and reduced wear, such as 'chisel' and rectangular profiles to minimize distortion and oxidation effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional contact probes are used for repetitive IC device testing, then initial electrical contact is established, but contact capability degrades over time due to wear, oxidation, and plated layer peel-off
Solution Approach 1:
The contact probe employs a composite structure combining a resilient body (polymer or elastomer material) with an embedded conductive element (metal wire or foil). This composite design provides both mechanical compliance for maintaining contact force and electrical conductivity for signal/ground paths, while the resilient material resists oxidation and wear better than pure metal contacts.
Solution Approach 2:
The invention changes the physical state and properties of the contact probe by using a resilient, compliant material instead of rigid metal. The material properties are selected to provide appropriate durometer hardness, elastic recovery, and electrical conductivity, allowing the probe to adapt to contact variations and maintain reliable electrical connection over extended service life.
2Quantity of substance
If probe assemblies are designed for high-density QFP devices with edge-mounted pins, then contact density increases, but alignment variability and contact location inconsistency worsen
Solution Approach 1:
The contact probe is designed as a dynamic, compliant element rather than a fixed rigid structure. The resilient body allows the conductive element to move and adapt its position within a range, compensating for variations in pin location and alignment. This dynamic compliance enables consistent electrical contact despite manufacturing tolerances in high-density QFP devices.
Solution Approach 2:
The probe uses a flexible resilient body (thin film or shell structure) that can deform and conform to the actual position of the contact pin. This flexibility allows the conductive element to reach the pin surface even when alignment varies, maintaining contact density while tolerating manufacturing precision variations.
3Reliability
If grounded connections are made with conventional probes, then electrical grounding is established, but crosstalk and signal distortion occur due to resistive changes from wear
Solution Approach 1:
The grounded connection uses a composite structure with a resilient non-oxidizing body and an embedded conductive element. The resilient material protects the conductive element from oxidation and wear, maintaining low and stable resistance in the ground path. This prevents the resistive changes that cause crosstalk and signal distortion in conventional metal-to-metal contacts.
Data Source
AI summary
An automated high speed test solution for Quad Flat Pack device packages that enables connectivity between test equipment and the integrated circuit under test is described. A test probe geometry that provides highly repeatable and reliable connections suitable for use with consumer grade QFP devices coupled with ease of maintenance is provided. In some embodiments, the probe tip ends are chisel-shaped. The probes can be slightly slanted with respect to a vertical axis of the probe retaining block.