Semiconductor Solder Blocking Metal Layer Bubble Management
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Solution Overview
Problem
Existing methods for removing air bubbles from AuSn solder in semiconductor devices are inefficient, leading to increased thermal resistance and reduced operational lifespan due to variations in manufacturing and potential bubble entrapment under heat-generating elements.
Innovation Solution
A semiconductor device and manufacturing method involving a solder blocking metal layer of nickel-chrome (NiCr), nickel (Ni), or titanium (Ti) on the rear surface of the semiconductor chip, which extends to the edge and has poor wettability with AuSn solder, collects and discharges air bubbles to the periphery, reducing their occurrence and enhancing heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If air bubbles are removed by scrubbing the semiconductor chip during mounting, then air bubbles in the AuSn solder are reduced, but it is difficult to completely remove air bubbles due to manufacturing variations
Solution Approach 1:
A solder blocking metal layer (NiCr, Ni, or Ti) is introduced as an intermediary structure between the AuSn solder and the semiconductor chip. This layer acts as a barrier that prevents solder from penetrating into regions where air bubbles would be trapped, while still allowing the scrubbing action to occur. The solder blocking layer thus mediates between the mechanical scrubbing process and the solder filling process to achieve complete air bubble removal.
Solution Approach 2:
The rear surface metal layer is segmented into different functional regions: a heating region that contacts the AuSn solder for thermal bonding, and a non-heating region covered by the solder blocking metal layer that prevents solder penetration. This segmentation allows different areas to perform different functions - one for bonding and one for bubble prevention - thereby achieving complete air bubble removal while maintaining reliable electrical and thermal connections.
2Temperature
If the AuSn solder layer is made thin to improve thermal conductivity, then heat dissipation is improved, but air bubbles entering the solder significantly increase thermal resistance
Solution Approach 1:
The solder blocking metal layer is formed in advance on the rear surface of the semiconductor chip before the AuSn solder is applied. This preliminary structure prevents air bubbles from being trapped during the subsequent mounting and scrubbing processes. By preventing bubble formation beforehand rather than trying to remove them afterward, the thin AuSn solder layer maintains its low thermal resistance and high thermal conductivity throughout the device lifecycle.
3Reliability
If a solder blocking metal layer is formed on the entire rear surface, then air bubbles are completely prevented, but the heating region cannot effectively contact the AuSn solder for bonding
Solution Approach 1:
The rear surface metal layer is divided into distinct functional zones: a heating region without solder blocking metal that allows direct contact between AuSn solder and the semiconductor substrate for strong thermal and electrical bonding, and a non-heating region covered by solder blocking metal (NiCr, Ni, or Ti) that prevents solder penetration and air bubble formation. This spatial segmentation resolves the contradiction between preventing bubbles and enabling effective bonding.
Solution Approach 2:
Different regions of the rear surface are given different properties: the heating region has direct metal-to-solder contact for optimal thermal conduction and bonding strength, while the non-heating region has a solder blocking layer with poor wettability to prevent solder adhesion and bubble entrapment. This local differentiation of material properties allows each region to optimize its function without compromising the other.
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 reduces air bubbles in the AuSn solder layer, improving heat dissipation and extending the operational lifespan of semiconductor devices by efficiently dissipating heat from heat-generating elements.
Implementation Method 1
The solder blocking metal layer includes at least one of nickel-chrome (NiCr), nickel (Ni) and titanium (Ti) and extends to a first edge of the semiconductor chip. A void is provided between the solder blocking metal layer and the AuSn solder layer.
Data Source
AI summary
A semiconductor device including a mounting substrate, a semiconductor chip, a rear-surface metal layer, an AuSn solder layer, and a solder blocking metal layer, is disclosed. The semiconductor chip is mounted on the mounting substrate, and includes front and rear surfaces, and a heat generating element. The rear-surface metal layer includes gold (Au). The AuSn solder layer is located between the mounting substrate and the rear surface to fix the semiconductor chip to the mounting substrate. The solder blocking metal layer is located between the rear surface and the mounting substrate, and in a non-heating region excluding a heating region in which the heat generating element is formed. The solder blocking metal layer includes at least one of NiCr, Ni and Ti and extends to an edge of the semiconductor chip. A void is provided between the solder blocking metal layer and the AuSn solder layer.