Semiconductor Chip 45-Degree Tilt for BGA Stress Relief
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Solution Overview
Problem
Existing BGA semiconductor devices face reliability issues due to stress from differences in linear expansion coefficients between the wiring board and semiconductor chip, leading to connection bump breakage, especially when corner bumps are large or arranged in specific patterns, and tilting the chip increases board size and warping risks.
Innovation Solution
A semiconductor device design where the semiconductor chip is mounted at a 45-degree tilt on the wiring board, with chip corners positioned near the board's outer edges, avoiding direct stress concentration on corner bumps and allowing for compact packaging without modifying bump arrangements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If connection bumps at corners are made larger to increase connection strength, then connection bump breakage is prevented, but device complexity and manufacturing difficulty increase due to non-uniform bump sizes
Solution Approach 1:
The patent applies local quality by positioning the semiconductor chip at a 45-degree rotation such that chip corners are located away from wiring board corners, specifically placing chip corners over regions with existing connection bumps. This creates a local stress distribution where corner bumps receive support from the chip structure rather than bearing concentrated thermal stress, thereby improving reliability without requiring non-uniform bump sizes
Solution Approach 2:
The patent introduces asymmetry by rotating the semiconductor chip 45 degrees relative to the wiring board, breaking the conventional aligned configuration. This asymmetric positioning redistributes thermal stress across multiple connection bumps rather than concentrating it at corner bumps, allowing all bumps to maintain uniform size while improving connection reliability
2Reliability
If the semiconductor chip is tilted on the wiring board to avoid stress concentration, then connection bump breakage is reduced, but the wiring board size must be increased to prevent chip extrusion
Solution Approach 1:
The patent applies asymmetry by rotating the chip 45 degrees, which optimizes the use of wiring board space. The diagonal orientation allows the chip to be positioned such that its corners extend toward the board edges without requiring excessive board area, achieving stress distribution while maintaining compact dimensions
Solution Approach 2:
The patent utilizes the angular dimension by introducing a 45-degree rotation, transforming the conventional orthogonal alignment into a diagonal configuration. This dimensional change allows the chip to be positioned optimally on the board, distributing stress effectively while fitting within the same or reduced board footprint
3Reliability
If the wiring board size is increased to accommodate tilted chip mounting, then stress distribution improves, but manufacturing cost increases due to reduced yield from mother material
Solution Approach 1:
The 45-degree rotation creates an asymmetric layout that optimizes space utilization. By positioning chip corners over existing connection bump regions rather than requiring additional board perimeter, the design achieves improved stress distribution without increasing the overall board dimensions, thereby maintaining manufacturing yield
Solution Approach 2:
The patent makes the connection bumps serve multiple functions: they provide both electrical connection and mechanical support for the tilted chip. The existing bump array configuration is utilized effectively to support the rotated chip, eliminating the need for additional structural elements or increased board size
4Reliability
If connection bumps are arranged concentrically to prevent stress concentration, then reliability improves, but adaptability decreases due to specialized design requirements
Solution Approach 1:
The patent applies asymmetry at the chip orientation level rather than requiring symmetric concentric bump arrangements. The standard matrix bump pattern is maintained, but the chip is rotated 45 degrees to achieve stress distribution, allowing compatibility with conventional bump designs from multiple manufacturers
Solution Approach 2:
Instead of modifying the bump arrangement to achieve stress distribution, the patent inverts the approach by modifying the chip orientation while maintaining the standard bump pattern. This allows the use of conventional bump designs and wiring board layouts, preserving adaptability and standardization
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 design enhances the reliability of secondary packaging, reduces warping, and minimizes the size of the semiconductor device while maintaining bump integrity, allowing for higher-density wire arrangements and cost-effective production.
Implementation Method 1
stress generated by the difference in the linear expansion coefficients (α) of the wiring board 102 and the semiconductor chip 106
Data Source
AI summary
A semiconductor device includes at least a wiring board, a semiconductor chip that is mounted on one face side of the wiring board, connection pads that are formed on the one face side of the wiring board, and connect through bonding wires to electrode pads on the semiconductor chip, and bumps disposed on another face side of the wiring board; the semiconductor chip is disposed such that four chip sides face corners of the wiring board, and each chip corner is near one of the outer peripheral sides of the wiring board; and, on one face of the wiring board are provided corner regions which are enclosed by the chip sides of the semiconductor chip and the corners of the wiring board, and the connection pads are disposed in these corner regions.