Offset IC Package Interconnects for Thermal Stress Relief
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Solution Overview
Problem
Integrated circuit packaging faces challenges in providing adequate electrical connections and thermal management, particularly due to coefficient of thermal expansion (CTE) mismatch between the die and substrate, leading to solder bump structure failure during thermal cycling.
Innovation Solution
The configuration of solder bump structures is offset at high temperatures when the material is ductile and aligned at low temperatures when it is brittle, shifting the incidence of tensile and shear stresses to reduce the likelihood of failure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the die and substrate are aligned at room temperature, then electrical connections are optimized, but thermal cycling causes misalignment and solder bump failure due to CTE mismatch
Solution Approach 1:
The interconnects are pre-positioned with an offset at room temperature during manufacturing, anticipating the thermal expansion that will occur during operation. This preliminary offset ensures that when the package heats up during solder reflow and operation, the thermal expansion brings the interconnects into proper alignment, preventing stress on the solder bumps during thermal cycling
Solution Approach 2:
The invention changes the positional parameter of the interconnects based on temperature conditions. By designing the interconnects to be offset at room temperature but aligned at operating temperature, the solution accounts for the parameter change (thermal expansion) that occurs during solder reflow and operation, thereby preventing solder bump failure
2Strength
If solder reflow is performed at high temperature, then die attachment is achieved, but CTE mismatch causes shear and tensile stresses on solder bumps
Solution Approach 1:
The interconnects are pre-positioned with an offset at room temperature during manufacturing, anticipating the thermal expansion that will occur during solder reflow. This preliminary offset ensures that when the package heats up during solder reflow, the thermal expansion brings the interconnects into proper alignment, preventing stress on the solder bumps
3Productivity
If the package size is increased to accommodate more electrical connections, then transistor density is supported, but thermal management becomes more difficult
Solution Approach 1:
The invention applies local quality by creating a specific thermal expansion compensation mechanism at the interconnect level. Rather than trying to manage heat across the entire large package, the solution locally addresses thermal expansion at the critical die-to-substrate interface through offset interconnects, allowing each region to handle thermal effects appropriately
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 configuration significantly reduces the likelihood of solder bump structure failure by applying stresses when the material is in a more ductile state, thereby enhancing the reliability of the IC package during thermal cycling.
Implementation Method 1
a CTE mismatch between the die and the substrate may cause shear and/or tensile stresses on the solder bump structures which attach the die to the substrate. Consequently, repeatedly cycling the IC package from an operating temperature to a non-operating temperature
Implementation Method 2
by shifting the incidence of tensile and shear stresses from low temperatures, when the solder bump structures are cold and brittle, to high temperatures, when the solder bump structures are warm and ductile
Data Source
AI summary
One embodiment of the present invention sets forth an integrated circuit package including a substrate, an integrated circuit die, and a plurality of solder bump structures. The substrate includes a first plurality of interconnects disposed on a first surface of the substrate. The integrated circuit die includes a second plurality of interconnects disposed on a first surface of the integrated circuit die. The plurality of solder bump structures couple the first plurality of interconnects to the second plurality of interconnects. The first plurality of interconnects are configured to be substantially aligned with the second plurality of interconnects when the integrated circuit package is at a first temperature within a range of about 0° C. to about −100° C. The first plurality of interconnects are configured to be offset from the second plurality of interconnects when the integrated circuit package is at a temperature above the first temperature.