Semiconductor Assembly Intermetallic Bonding for Diode Lasers
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Solution Overview
Problem
Conventional diode laser production methods face limitations in current-carrying capacity and thermal stress due to the use of indium layers, which can lead to material migration and failure during pulsed operation.
Innovation Solution
A method involving the formation of intermetallic phases such as AuPb2, AuCd3, AuIn2, AuIn, AuSn4, and AuSn by binding soft metals like indium and tin with gold, using a first metallic layer of soft metals and a second metallic layer of gold, to create a durable connection between the semiconductor chip and the heat-conducting body through solid-state diffusion, thereby enhancing the mechanical properties of the connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a thick indium layer is used to compensate thermal expansion differences, then thermal stress is reduced, but material migration occurs during pulsed operation leading to failure
Solution Approach 1:
The patent changes the physical and chemical parameters of the connection layer by forming intermetallic phases (AuIn2, AuIn, AuSn2, AuSn) through controlled diffusion between gold and soft metal layers. This transforms the soft, migratable indium or tin into stable intermetallic compounds that maintain thermal expansion compensation without material migration during pulsed operation.
Solution Approach 2:
The patent creates a composite connection structure consisting of multiple layers: a first metallic layer of soft metal (indium or tin), a second metallic layer of gold, and an intermetallic layer formed by their diffusion. This composite structure combines the thermal expansion compensation capability of soft metals with the stability and migration resistance of intermetallic phases.
2Reliability
If conventional soldering is used to connect the laser bar, then electrical connection is established, but tensions are introduced that adversely affect electrooptical properties
Solution Approach 1:
The patent replaces the mechanical soldering process with a solid-state diffusion process. Instead of melting and solidifying solder material, the connection is formed by atomic diffusion between the soft metal layer and gold layer at controlled temperatures, eliminating mechanical stresses that would affect the laser bar's electrooptical properties.
Solution Approach 2:
The patent changes the connection process parameters by using low-temperature solid-state diffusion instead of high-temperature soldering. The diffusion process occurs at temperatures below the melting point of the soft metal, preventing thermal damage and mechanical stress to the laser bar while still achieving reliable electrical and thermal connection.
3Device complexity
If bond wires are used for current connection, then the structure is simple, but the current-carrying capacity is limited
Solution Approach 1:
The patent merges the functions of thermal management and electrical connection by integrating the soft metal layer and gold layer into a unified connection structure that serves both as a heat sink interface and a high-current electrical contact. This eliminates the need for separate bond wires while providing superior current-carrying capacity through the low-resistance metallic layers.
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 approach results in a diode laser with improved durability and current-carrying capacity, specifically designed for high operating currents and pulsed operation, by eliminating the need for thick indium layers and reducing thermal stresses.
Implementation Method 1
forming an intermetallic layer by solid-state diffusion of the first metallic layer into the second metal layer and/or vice versa
Data Source
AI summary
The invention relates to a method for producing a semiconductor assembly, in particular connecting a semiconductor chip to a heat sink. A first metal layer consisting of Pb, Cd, In or Sn is made so thin that it is bonded by means of an opposing second metal layer consisting of another metal, for example gold, in a layer consisting of intermetallic phases. This can prevent migration of the soft metals. The brittle intermetallic layer is prevented from fracturing by a continuous pressing force.