Package on Package Thermal Interposer for Uniform Temperature Control
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Solution Overview
Problem
Existing package on package (PoP) integrated circuit testing methods are inefficient in controlling the temperature of both the top and bottom packages due to high thermal impedance through the interposer, leading to uneven temperature distribution during extreme environment validation.
Innovation Solution
A thermal interposer system with a test probe guide and insulator top and bottom, linked to a thermal conductor and a thermal control unit, enabling direct thermal and electrical contact between the top and bottom packages for uniform temperature control across a wide range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a standard interposer is used to connect top and bottom packages, then electrical connections are established, but thermal impedance increases causing uneven temperature distribution
Solution Approach 1:
The interposer is segmented into distinct functional zones: an electrical connection region with conductive structures for signal transmission, and a thermal conduction region with high thermal conductivity material for heat transfer. This segmentation allows each region to optimize its specific function without compromising the other, resolving the contradiction between electrical connectivity and thermal uniformity.
Solution Approach 2:
Different regions of the interposer are assigned different material properties: the electrical connection region uses materials optimized for electrical conductivity, while the thermal conduction region uses materials with high thermal conductivity. This local differentiation of material properties enables simultaneous achievement of electrical connectivity and thermal uniformity across the package stack.
2Ease of operation
If thermal control is applied through the top device and interposer, then the logic device can be controlled, but thermal efficiency decreases due to thermal impedance
Solution Approach 1:
A dedicated thermal conduction path is introduced as an intermediary between the temperature control source and the logic device. This thermal conduction region acts as a mediator that efficiently transfers thermal energy, reducing thermal impedance and improving thermal efficiency while maintaining the ability to control temperatures of both packages.
3Reliability
If one package is controlled to a specific temperature, then that package operates correctly, but the other package experiences excessive or insufficient temperature
Solution Approach 1:
The interposer is designed with multi-functionality: it provides electrical connections between packages, establishes thermal conduction paths for heat transfer, and serves as a structural support element. This universal design enables simultaneous temperature control of both packages, ensuring reliable operation of both devices while maintaining uniform temperature distribution across the entire package stack.
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 system ensures both ICs are maintained at a consistent temperature, preventing overstress and enabling seamless testing across a wide temperature range, from -55° C. to +150° C., during Automated Test Equipment (ATE) and System Level Testing (SLT) processes.
Implementation Method 1
a thermal conductor, the test probe guide and insulator top affixed to a top surface of the thermal conductor
Implementation Method 2
the thermal interposer transferring temperature between the thermal device plunger and the bottom package
Data Source
AI summary
Methods and apparatus for a package on package (POP) thermal forcing device. A thermal interposer includes a test probe guide and insulator top, a thermal conductor, the test probe guide and insulator top affixed to a top surface of the thermal conductor, a test probe, and a test probe guide and insulator bottom affixed to a bottom surface of the thermal conductor, the test probe guide and insulator bottom configured in a ring-like shape to enable the thermal conductor to pass through and make contact with a bottom of a package on package (PoP) integrated circuit (IC).