Compliant Elastomeric Probe for Fine-Pitch Wafer Testing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional probe systems are inadequate for testing fine-pitch, three-dimensional interconnect semiconductor wafers due to manufacturing variations, high deflection forces, and mechanical 'cross-talk' issues, which can damage fragile silicon wafers and provide false readings.
Innovation Solution
A probe head with a compliant and resilient elastomeric body and microfabricated metal contactor tips, integrated with a space transformer substrate and thin-film redistribution layer, allowing precise planarity and reduced deflection forces for efficient contact with fine-pitch microelectronic arrays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional Vertical MEMS probes with metal alloy construction are used, then manufacturing is simplified, but the probes require relatively large deflection forces that can damage thin TSV semiconductor wafers
Solution Approach 1:
The probe employs a composite structure combining a metal alloy cantilever body with a polymer coating layer. The metal alloy provides structural strength and electrical conductivity, while the polymer coating reduces friction and allows for lower deflection forces. This composite approach enables the probe to contact fine-pitch solder bumps effectively without requiring excessive force that would damage thin TSV wafers.
2Manufacturing precision
If the number of probes is increased to provide the density of contacts required in fine-pitch applications, then testing coverage is improved, but the total deflection forces become quite large which is contraindicated for thin TSV semiconductor wafers
Solution Approach 1:
The invention changes the physical parameters of the probe by reducing the cantilever dimensions (length, width, thickness) and modifying the material properties through polymer coating. These parameter changes reduce the force required per probe, enabling high contact density (thousands of probes) without generating excessive total force that would damage thin wafers.
3Manufacturing precision
If conventional MEMS-based micro spring probes are miniaturized for fine-pitch application, then contact precision is improved, but the amount of available deflection or compliance becomes too small
Solution Approach 1:
The polymer coating on the metal alloy cantilever creates a composite structure that maintains compliance even at miniaturized dimensions. The polymer layer's viscoelastic properties provide additional deflection capability beyond what a solid metal cantilever of the same size could achieve, preserving compliance while maintaining fine-pitch contact precision.
4Ease of manufacture
If conventional probes are fabricated separately and then individually assembled onto a ceramic guide plate, then manufacturing flexibility is improved, but manufacturing variations in the planarity and positioning of the contact tips become unacceptable in fine-pitch applications
Solution Approach 1:
The invention integrates the cantilever, contact tip, and support structure into a single monolithic component fabricated using standard MEMS processes. This eliminates the separate assembly steps that caused positioning variations, while the contact tips are precisely positioned through photolithographic patterning and electroplating processes inherent to MEMS fabrication.
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
The solution enables precise and reliable contact with fine-pitch microelectronic arrays, minimizing deflection forces and maintaining planarity, thus effectively testing fragile TSV semiconductor wafers without causing damage.
Implementation Method 1
due to their metal alloy construction, such probes can only be deflected or deformed through a distance that is a small percentage of their size
Data Source
AI summary
Provided are microfabricated probe elements, including elastomer elements, and methods of making the same, that can be readily used with fine pitch microelectronic arrays, for instance by providing sufficient compliance in a small package, while minimizing deflection forces, and while precisely maintaining the planarity and positioning of the contact tips across vast grid arrays. Elastomer elements may be generated using photolithography, either directly or through a sacrificial lost-mold process. Elastomer probe elements are provided with rigid tip structures microfabricated thereon to improve contact pressure. A novel space transformation probe card assembly is also provided.