Integral Metal Structure With Conductive Post Portions For Thermal Stress
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing semiconductor packaging technologies face delamination issues due to thermal expansion disparities between copper power bus bars and silicon substrates, leading to unreliable physical connections despite sufficient electrical contact.
Innovation Solution
Integrated metal structures with slideable post portions and fuzz buttons or braided copper cables are used to dissipate stress caused by thermal expansion, maintaining constant low-resistance electrical contact by allowing the metal structures to bend or slide relative to each other.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If soldering is used to connect copper power bus bars to the semiconductor substrate, then sufficient electrical connection is achieved, but the physical connection is subject to delamination during temperature changes due to thermal expansion disparity
Solution Approach 1:
The copper power bus bar is segmented into multiple thin copper foils (approximately 17 foils, each about 6 microns thick) stacked together. This segmentation allows each individual foil to flex and accommodate thermal expansion differences between copper and silicon, preventing delamination while maintaining electrical connection. The segmented structure transforms a rigid monolithic connection into a flexible composite connection.
Solution Approach 2:
The invention creates a composite structure by stacking multiple thin copper foils together to form a power bus bar. This composite copper structure combines the electrical conductivity of copper with the flexibility needed to accommodate thermal expansion. The composite nature of the stacked foils allows the connection to withstand temperature cycling without delamination while maintaining low-resistance electrical contact.
2Reliability
If thick copper power bus bars are used to supply power, then low resistance power connections are achieved, but the disparity in thermal expansion coefficients causes separation from the semiconductor substrate
Solution Approach 1:
The invention changes the physical parameters of the copper power bus bar by reducing individual foil thickness to approximately 6 microns while stacking multiple foils (about 17) to achieve the desired overall thickness and conductivity. This parameter change transforms the rigid thick copper bar into a flexible composite structure that can accommodate thermal stress, maintaining both electrical conductivity and mechanical attachment strength through temperature cycles.
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 effectively prevents delamination and maintains robust electrical connections across temperature changes by accommodating the differing thermal expansion coefficients of copper and silicon, ensuring reliable power supply and signal routing.
Implementation Method 1
the coefficient of thermal linear expansion for power bus bars made of copper is seventeen parts per million per degree Centigrade 'ppm/° C.' The same coefficient for silicon is three ppm/° C. If a semiconductor substrate with copper power bus bars two inches in length experiences a change in temperature of one-hundred degrees Centigrade, the copper power bus bars 81-84 would expand approximately thirty five microns more than the semiconductor substrate 25 at each end of the semiconductor substrate.
Implementation Method 2
If the power bus bars are soldered to conductive metal layer 21 there is sufficient electrical connection but the physical connection to conductive layer 21 and the semiconductor substrate may be subject to delamination during changes in temperature.
Data Source
AI summary
A plurality of FPGA dice is disposed upon a semiconductor substrate. In order to supply the immense power required by the plurality of FPGA dice, power is routed through the semiconductor substrate vertically from thick metal layers and large integral metal structures located on the other side of the semiconductor substrate. Because the semiconductor substrate has a different coefficient of thermal linear expansion than metal layers in contact with the substrate, delamination may occur when the structure is subject to changes in temperature. To prevent delamination of metal layers connected to the semiconductor substrate and in electrical contact with the integral metal structures, the integral metal structures are manufactured with an array of post portions. During changes in temperature, the post portions of the integral metal structures bend and slide relative to metal layers connected to the semiconductor substrate and prevent linear stresses that may otherwise cause delamination.