Wafer Joining Protrusion for Interval Control
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Solution Overview
Problem
Conventional methods for transitioning from two-dimensional to three-dimensional mounting of wafers or circuit boards face challenges in uniformly filling adhesives between layers, controlling heating and pressing conditions, and maintaining the integrity of low melting point materials during the joining process, especially for larger wafers or circuit boards.
Innovation Solution
Incorporating a protrusion made of low melting point metal that defines the interval between joined wafers or circuit boards without deforming when melted, ensuring electrical connection and maintaining structural integrity, while using thermosetting adhesives that can be cured simultaneously with the connection process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If adhesive is applied between wafers and pressed together to force out adhesive for electrical connection, then electrical connection between metals is achieved, but large pressing force is required which is unsuitable for minute bumps
Solution Approach 1:
The invention changes the physical state of the low melting point metal from solid to liquid by heating it above its melting point, allowing the wafers to be joined without requiring large pressing forces. The metal remains liquid during the joining process and solidifies afterward to establish electrical connection, eliminating the need for high force that would damage minute bumps.
Solution Approach 2:
The invention utilizes the phase transition of the low melting point metal from solid to liquid state during the joining process. By heating the metal above its melting point, it becomes liquid and can flow to fill gaps between wafers, enabling joining without large pressing forces. After cooling, the metal solidifies to provide both mechanical bonding and electrical connection.
2Temperature
If low melting point metal is used for joining wafers, then joining temperature can be reduced, but the metal may deform during the joining process
Solution Approach 1:
The invention applies a protrusion structure to the low melting point metal before the joining process. This protrusion prevents the metal from deforming during heating and joining by providing a structural framework that maintains shape stability even when the metal is in liquid state, allowing low temperature joining without deformation.
Solution Approach 2:
The invention creates a composite structure combining the low melting point metal with a protrusion element that has higher structural stability. This composite approach allows the metal to provide low-temperature joining capability while the protrusion structure maintains shape stability and prevents deformation during the joining process.
3Length of moving object
If protrusion is made small for minute bumps, then miniaturization is achieved, but the protrusion may break during the joining process
Solution Approach 1:
The invention changes the temperature parameter of the low melting point metal to above its melting point during the joining process. This allows the metal to become liquid and flow to fill gaps, providing mechanical support and preventing breakage of small protrusions while maintaining miniaturization. The liquid state compensates for the reduced mechanical strength of small protrusions.
4Reliability
If adhesive is forced out from between metals by pressing, then electrical connection is achieved, but uniform adhesive distribution is difficult to achieve
Solution Approach 1:
The invention changes the temperature parameter of the low melting point metal to above its melting point, allowing it to become liquid and flow uniformly to fill gaps between wafers. This eliminates the need to force out adhesive by pressing, achieving both uniform distribution and reliable electrical connection without requiring precise control of pressing force.
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 enables effective three-dimensional mounting with uniform adhesive distribution, maintaining the interval between layers, and allowing for strong electrical connections without deforming the low melting point metal, thus overcoming the limitations of conventional methods.
Implementation Method 1
a low melting point metal which melts at a temperature equal to or higher than the melting temperature of the protrusion
Implementation Method 2
which defines an interval between the mutually joined wafers or between the mutually joined circuit boards without being deformed at the time when the low melting point metal is melted
Data Source
AI summary
A wafer (or a circuit board), which is used to perform three-dimensional mounting, has protrusion 20 which is provided in low melting point metal 15 for electrically connecting mutually joined wafers 61 and 62, and which defines an interval between mutually joined wafers 61 and 62 without being deformed at the time when low melting point metal 15 is melted. A joining structure of wafers 61 and 62 is manufactured by using wafers 61 and 62, at least one of which has protrusion 20. In the manufactured joining structure of wafers 61 and 62, wafers 61 and 62 are electrically connected to each other by low melting point metal 15, and protrusion 20, which defines the interval between wafers 61 and 62 without being deformed at the time when low melting point metal 15 is melted, is provided in low melting point metal 15.