Semiconductor Aperture Shape for Thermal Deviation
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Solution Overview
Problem
The existing flip chip technique faces challenges in miniaturization and increased signal terminal density due to limitations in solder bump size and underfill resin injection, leading to potential short circuits and reliability issues caused by positional deviations between solder resist apertures and electrodes, as well as exposure of wirings at narrow pitches.
Innovation Solution
A semiconductor device with a solder resist layer having elongated apertures aligned with the lengthwise direction of the wirings, adjusted according to the thermal expansion coefficient of the packaging substrate, to alleviate positional deviations and prevent short circuits, while ensuring sufficient underfill resin injection and bonding strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the pitch between connection terminals is reduced to increase signal terminal density, then the number of terminals per unit area increases, but positional deviation between solder resist apertures and electrodes causes short circuits and bonding reliability deteriorates
Solution Approach 1:
The solder resist layer is designed with different aperture shapes for different regions: circular apertures in non-wiring areas and elongated apertures aligned with wirings in wiring areas. This local differentiation allows the aperture to accommodate thermal expansion deviations while maintaining precise alignment with electrodes, thereby preventing short circuits between adjacent wirings when pitch is reduced.
Solution Approach 2:
The shape parameter of the aperture is changed from circular to elongated along the wiring direction. This parameter change provides tolerance for positional deviation in the direction perpendicular to the wiring, allowing reliable bonding even at reduced pitches where thermal expansion causes misalignment between apertures and electrodes.
2Ease of manufacture
If circular apertures are used in conventional solder resist, then alignment with electrodes is simple, but short circuits occur between adjacent wirings at narrow pitches due to thermal expansion deviations
Solution Approach 1:
The aperture shape is locally optimized based on its position: circular where wirings are absent and elongated where wirings are present. This local quality approach maintains ease of manufacture through standardized formation processes while eliminating short circuits by preventing solder from bridging adjacent wirings through the elongated shape that confines solder within the aperture boundaries.
3Ease of operation
If solder bump diameter is increased to ensure gap for underfill resin injection, then underfill injection is facilitated, but inter-terminal pitch cannot be miniaturized
Solution Approach 1:
The aperture shape is changed from circular to elongated along the wiring direction, utilizing the dimensional space more efficiently. This allows the aperture to provide sufficient gap for underfill injection in the direction parallel to wirings while maintaining compact dimensions perpendicular to wirings, enabling miniaturization of inter-terminal pitch without compromising underfill injection capability.
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 effectively suppresses short circuits between adjacent wirings, enhances bonding strength, and improves the reliability and yield of the semiconductor device by maintaining the bonding area and reducing thermal stress, even at reduced inter-wiring pitches.
Implementation Method 1
By a batch reflow method, the solder may melt to form connection
Implementation Method 2
there is possibility of the following disadvantage. In heating for solder bonding during the assembly process, there may be deviation between a position of the aperture of the solder resist and a position of the solder, due to a difference in thermal expansion coefficients of the chip and the packaging substrate
Data Source
AI summary
Provided is a semiconductor device that includes a semiconductor chip, and a packaging substrate on which the semiconductor chip is mounted. The semiconductor chip includes a chip body and a plurality of solder-including electrodes that are provided on an element-formation surface of the chip body. The packaging substrate includes a substrate body, and a plurality of wirings and a solder resist layer that are provided on a front surface of the substrate body. The solder resist layer is provided as a continuous layer on the front surface of the substrate body and the plurality of wirings, and has an aperture on each of the plurality of wirings. The aperture has a planar shape elongated in a lengthwise direction of the wiring inside the aperture, with a length of the aperture adjusted in accordance with a thermal expansion coefficient of the packaging substrate.