Post Electrode Overhang Prevents Solder Adhesion Failure
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Solution Overview
Problem
The existing semiconductor devices face issues with solder adhesion failure due to the flow of tin solder onto the sidewalls of post electrodes, leading to stress concentration and reduced moisture resistance, which is exacerbated by the high hardness of tin compared to copper and the uneven distribution of solder on the sidewalls, causing cracks and disconnection in the semiconductor chip's surface protection film and interlayer insulating film.
Innovation Solution
The semiconductor device incorporates a post electrode with a cylindrical stem portion and an overhanging portion that protrudes beyond the stem, preventing solder from flowing onto the sidewalls and using a ternary alloy solder ball electrode made of Sn-Ag-Cu, which is connected to the terminal via a pre-solder, ensuring the solder ball electrode's height is larger than the post electrode's height, thereby reducing material costs and processing time while enhancing reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the post electrode height is increased to prevent solder adhesion failure, then reliability is improved, but manufacturing cost and processing time increase due to thicker resist films required for plating
Solution Approach 1:
The invention introduces a protruding portion that extends in the radial direction from the post electrode axis, creating a dimensional feature that prevents solder adhesion without increasing electrode height. This radial extension blocks solder from reaching the sidewalls while maintaining a compact overall structure, thus improving reliability without requiring thicker resist films or longer processing times
Solution Approach 2:
The protruding portion acts as an intermediary barrier between the solder and the post electrode sidewalls. By providing this intermediate structure, solder is prevented from directly adhering to the copper sidewalls, eliminating the adhesion failure mechanism without needing to increase the overall electrode dimensions or change the plating process parameters
2Reliability
If tin solder flows onto the sidewalls of the post electrode, then solder adhesion failure occurs due to stress concentration, but increasing post electrode height to prevent this increases material cost
Solution Approach 1:
Instead of increasing height to prevent solder adhesion, the invention uses a radial protrusion that extends outward from the electrode axis. This protruding portion creates a physical barrier that blocks solder flow onto the sidewalls, maintaining reliability while using minimal additional material and avoiding the need for thicker resist films
3Ease of manufacture
If the post electrode height is reduced to lower material cost, then manufacturing cost decreases, but solder adhesion failure risk increases
Solution Approach 1:
The invention maintains a compact post electrode height while introducing a radial protruding portion that prevents solder adhesion failure. This protrusion creates an effective barrier against solder flow onto sidewalls, ensuring reliable solder bonds without requiring increased electrode height or additional material consumption
Solution Approach 2:
The protruding portion is formed during the plating process itself, creating a preventive barrier before solder application. This preliminary structural feature proactively blocks potential solder adhesion pathways, ensuring reliability is built into the structure rather than added as a separate protective measure
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 effectively prevents solder adhesion failure by ensuring the solder does not adhere to the post electrode's sidewalls, maintaining the integrity of the semiconductor device's moisture resistance and electrical connectivity, thereby improving the reliability and performance of the semiconductor device.
Implementation Method 1
a post electrode having a cylindrical shape made of a Cu plating film is formed by a plating method
Implementation Method 2
the solder ball is melted by performing reflow for formation of the bump electrode to form a solder ball electrode
Data Source
AI summary
A semiconductor device includes a semiconductor substrate, a pad electrode formed on the semiconductor substrate, a post electrode formed on the pad electrode and made of a copper film, a solder ball electrode formed on the post electrode and made of ternary alloy containing tin, a terminal connected to the solder ball electrode and formed on a front surface of a wiring board, and a sealing material filling a gap between the semiconductor substrate and the wiring board. The post electrode includes a cylindrical stem portion and an overhanging portion positioned in an upper part of the stem portion and protruding to an outer side of the stem portion, the solder ball electrode is connected to an upper surface of the post electrode over the stem portion and the overhanging portion, and a sidewall of the stem portion contacts with the sealing material over the entire circumference thereof.