Test Pad Oxidation Prevention in Miniaturized IC Packages
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Solution Overview
Problem
The miniaturization of semiconductor package structures leads to issues with probe pad exposure and oxidation during the assembly process, preventing effective testing and increasing the risk of probe card damage, especially due to the shrinkage of solder caps under surface tension, which complicates probing on bottom packages.
Innovation Solution
The integration of a substrate with test pads featuring element pads and a conductive layer directly formed on these pads to prevent oxidation, using materials like solder or metallic alloys, which are applied through methods such as stencil printing, to create a protective layer that bridges adjacent element pads and ensures reliable electrical connectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If package configurations are made smaller and thinner to improve miniaturization, then portability and packaging density are improved, but probe pad exposure and oxidation occur during assembly, preventing effective testing
Solution Approach 1:
The patent applies preliminary action by forming a protective conductive layer (solder cap or metallic alloy) on the test pads before the assembly process. This pre-protection prevents oxidation from occurring during subsequent manufacturing steps, ensuring test pads remain functional for probing operations even in miniaturized packages.
Solution Approach 2:
The patent introduces an intermediary protective layer between the test pad and the oxidizing environment. This conductive coating acts as a mediator that prevents direct contact between oxygen/moisture and the test pad metal, eliminating oxidation while maintaining electrical conductivity for testing.
2Volume of moving object
If solder caps shrink under surface tension during assembly, then miniaturization is achieved, but probe card damage risk increases and probing becomes complicated
Solution Approach 1:
The protective conductive layer is applied to test pads before assembly operations. This preliminary protection ensures that even when solder caps shrink under surface tension, the test pads themselves are already protected from oxidation and damage, reducing probe card damage risk.
Solution Approach 2:
The conductive protective layer serves as a cushioning protection layer applied beforehand. It absorbs and distributes mechanical stresses during assembly, preventing direct transmission of damage forces to the underlying test pad structure and probe card contacts.
3Ease of manufacture
If conventional test pad structures are used in miniaturized packages, then manufacturing simplicity is maintained, but oxidation occurs and testing cannot be performed
Solution Approach 1:
The protective conductive layer is integrated into the existing manufacturing flow as a preliminary step before assembly. This approach maintains manufacturing simplicity by adding only one additional process step (forming the protective layer) while effectively preventing oxidation without complicating the overall manufacturing sequence.
Solution Approach 2:
The patent uses composite material structures by combining the base test pad metal with an overlay protective conductive layer (solder cap or metallic alloy). This composite structure maintains the electrical functionality of the test pad while the outer layer provides oxidation resistance, solving both manufacturing simplicity and oxidation prevention requirements.
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 solution enhances the reliability of the integrated circuit system by preventing oxidation and ensuring proper probing, reducing the risk of damage to the test pads and probe cards, while maintaining a reduced horizontal profile without additional silicon area, thus addressing the challenges of miniaturization and oxidation in the assembly process.
Implementation Method 1
forming a conductive layer over the test pad, the conductive layer having element layers directly on the element pads
Data Source
AI summary
A method of manufacture of an integrated circuit system includes: providing a substrate having a test pad with element pads; forming a conductive layer over the test pad, the conductive layer having element layers directly on the element pads; and mounting an integrated circuit over the substrate.