Semiconductor Joining Layer Copper Content Control
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Solution Overview
Problem
Semiconductor devices using high Cu content Sn—Cu solder face challenges with increased melting point, requiring improved heat resistance without forming a Cu6Sn5 compound on the joined member surface.
Innovation Solution
A semiconductor device with a joining layer containing 2.0 wt % or higher copper, where the base metal includes elemental copper dispersed in the solder material, forming a Cu6Sn5 portion in contact with a nickel film, allowing Cu6Sn5 formation even with low Cu content in the base metal, reducing the melting point and preventing solder flow and reaction with the nickel film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the proportion of Cu in Sn-Cu solder is increased to form Cu6Sn5 compound on the joined member surface, then diffusion between solder and joined member is prevented, but the melting point of the solder increases requiring improved heat resistance of the semiconductor element
Solution Approach 1:
Elemental copper particles are introduced into the solder material before joining, so that Cu6Sn5 compound is formed during the joining process itself rather than requiring high Cu content in the base metal. This preliminary preparation of copper particles allows the compound formation to occur in-situ during soldering, preventing the need to increase base metal Cu content and thereby avoiding the melting point increase
Solution Approach 2:
Elemental copper particles act as an intermediary substance that facilitates the formation of Cu6Sn5 compound between the solder and nickel film. These particles serve as a copper source that mediates the compound formation process, allowing the reaction to proceed with lower Cu content in the base solder material, thus resolving the contradiction between compound formation and melting point control
2Reliability
If the proportion of Cu in Sn-Cu solder is increased to form Cu6Sn5 compound, then a barrier layer is formed to prevent solder flow and reaction with nickel film, but the melting point increases
Solution Approach 1:
Copper particles are pre-introduced into the solder material to enable Cu6Sn5 compound formation during the joining process. This preliminary action ensures the barrier layer forms in-situ without requiring high Cu content in the base metal, thereby preventing the melting point increase while still achieving the desired barrier layer formation
Solution Approach 2:
The invention changes the parameter of copper distribution by introducing elemental copper particles separately from the base metal composition. This parameter change allows the total copper content to be sufficient for compound formation while keeping the base metal Cu content low, thus maintaining a lower melting point while still forming the protective Cu6Sn5 barrier layer
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
The solution effectively reduces the melting point of the solder and prevents peeling and shape change during joining, ensuring reliable joint formation and high heat resistance without requiring additional heat resistance in the semiconductor element.
Implementation Method 1
forming a Cu6Sn5 portion in contact with a nickel film
Implementation Method 2
Due to the formation of the Cu6Sn5 compound, diffusion between the solder and the joined member is prevented
Implementation Method 3
When a solder having a high melting point (liquidus temperature) is used, it is necessary that the heat resistance of a semiconductor element is improved
Implementation Method 4
the semiconductor element is joined to the joined member through a Sn—Cu solder
Data Source
AI summary
A semiconductor device includes: a semiconductor element; a joined member that is joined to the semiconductor element and includes a nickel film; and a joining layer that is joined to the joined member and contains 2.0 wt % or higher of copper, in which the joining layer includes a solder portion and a Cu6Sn5 portion, base metal of the solder portion contains at least tin as a constituent element and contains elemental copper, and the Cu6Sn5 portion is in contact with the nickel film.