Transient Liquid Phase Bonding for Electronic Device Substrates
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Solution Overview
Problem
Conventional methods for manufacturing electronic devices with bulk acoustic wave resonators require high temperature and pressure processes, leading to device damage, reduced yield, and defects due to overetching during the formation of through-holes.
Innovation Solution
The method involves transient liquid phase bonding using a first substrate with a side wall made of gold and a second substrate with a side wall made of copper and tin, where the tin layer has a lower melting point, allowing for bonding at lower temperatures and preventing defects by forming alloy layers without melting all metals together.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high temperature and pressure bonding process is used to bond device substrate and cap substrate, then bonding strength is improved, but device damage and manufacturing yield decrease
Solution Approach 1:
The patent changes the bonding parameters by introducing a transient liquid phase bonding process with intermediate metal layers (such as copper and gold) that have different melting points. This allows bonding to occur at lower temperatures than conventional direct gold-gold or copper-copper bonding, reducing thermal stress and preventing device damage while maintaining adequate bonding strength
Solution Approach 2:
The patent uses composite metal layer structures with intermediate bonding layers (e.g., copper layer and gold layer) between the device substrate and cap substrate. These composite structures enable controlled transient liquid phase formation at specific interfaces during bonding, achieving strong bonds without requiring extreme temperatures that would damage the device
2Manufacturing precision
If repeated cycles between normal and high temperature/pressure steps are used, then bonding quality is improved, but cycle time increases
Solution Approach 1:
The patent performs preliminary preparation by forming the intermediate metal layers (copper and gold layers) on the substrates before bonding. This preliminary action ensures that the transient liquid phase bonding can proceed efficiently in a single controlled heating step, eliminating the need for repeated temperature cycling while maintaining bonding quality
Solution Approach 2:
The patent modifies the bonding process parameters by using a single controlled heating step with transient liquid phase bonding instead of repeated cycles. The intermediate metal layers are designed to melt and form bonds at specific temperatures, allowing quality bonding to be achieved in one optimized process step rather than multiple cycles
3Reliability
If conventional through-hole formation process is used, then device connectivity is achieved, but overetching defects occur
Solution Approach 1:
The patent introduces intermediate metal layers (copper layer and gold layer) as mediators in the bonding process. These intermediate layers control the bonding interface formation and prevent direct contact between device substrate and cap substrate metals, eliminating overetching defects while ensuring proper connectivity through controlled transient liquid phase bonding
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 reduces cycle time, improves manufacturing yield, and prevents defects caused by overetching, resulting in more reliable electronic devices with enhanced performance.
Implementation Method 1
heating the first substrate and the second substrate to bond the first side wall and the second side wall with each other, the first metal layer, the second metal layer, and the third metal layer being heated to form alloy layers by transient liquid phase bonding
Data Source
AI summary
An electronic device includes a first substrate and a second substrate. A side wall joins the first substrate to the second substrate. The side wall includes a first alloy layer of a first metal and a second metal bonded directly to an upper surface of the first substrate and a second alloy layer of the first metal and a third metal disposed on top of the first alloy layer and bonded directly to a lower surface of the second substrate, the second metal and the third metal being different from each other and from the first metal. An electronic circuit is disposed on the lower surface of the second substrate within a cavity defined by the lower surface of the first substrate, the upper surface of the second substrate, and the side wall.