Semiconductor Hermetic Sealing with Gold-Tin Ball Solder
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Solution Overview
Problem
Conventional semiconductor device sealing methods using ribbon-shaped solder often result in oxide film formation, leading to defects in PIND tests due to solder fragments falling inside the device during the scrubbing process.
Innovation Solution
A semiconductor device and manufacturing method utilizing a package body with a continuous first sealing surface and recesses for ball solders made of gold-tin alloy, where the first solder outflow prevention parts are positioned closer to the chip mounting region and second solder outflow prevention parts surround the recesses, allowing for hermetic sealing without scrubbing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ribbon-shaped solder is used for hermetic sealing, then the sealing function is achieved, but oxide film formation occurs and solder fragments fall inside the device during scrubbing
Solution Approach 1:
The patent changes the physical state parameters of the solder from ribbon-shaped to ball-shaped. The ball shape with controlled diameter (0.3-0.8mm) prevents the solder from forming oxide films during storage and transport, and eliminates the need for scrubbing operations that generate harmful fragments
Solution Approach 2:
The patent utilizes the phase transition of solder from solid ball form to liquid state during reflow soldering, then back to solid form for hermetic sealing. This phase transition enables the solder to flow and fill the sealing gap effectively while maintaining purity without oxide film contamination
2Strength
If scrubbing is performed to remove oxide film, then bonding stability is improved, but solder fragments fall inside the package body
Solution Approach 1:
The patent performs preliminary action by pre-forming spherical solder balls with controlled size and placing them in predetermined positions on the sealing surface before the sealing process. This eliminates the need for subsequent scrubbing operations that would generate harmful fragments
Solution Approach 2:
The patent uses ball solder as a disposable consumable material that is placed in specific positions and consumed during the sealing process. The ball solder is designed to be used once for hermetic sealing, eliminating the need for repeated scrubbing and reapplication
3Reliability
If ball solder is used instead of ribbon solder, then oxide film formation is reduced, but solder may flow out to the side face of the package body
Solution Approach 1:
The patent applies local quality by creating a recess structure at the sealing position with specific depth and diameter ratios. This localized structural modification confines the molten ball solder to the sealing gap area, preventing it from flowing out to the side face while ensuring complete filling of the hermetic seal gap
Solution Approach 2:
The patent transitions from two-dimensional ribbon solder to three-dimensional ball solder, utilizing the vertical dimension for controlled melting and flow. The spherical geometry provides uniform radial expansion during melting, enabling precise control of solder distribution in all directions while confining it within the sealing area
4Reliability
If ball solder is placed on the sealing surface, then hermetic sealing is achieved, but the ball solder may fall down before melting
Solution Approach 1:
The patent performs preliminary action by creating recess structures on the sealing surface before placing the ball solder. The recesses with controlled dimensions provide mechanical retention for the ball solder, preventing it from falling down during handling and assembly operations before the melting and sealing process
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 stabilizes the ball solders on the sealing surface, reducing defects in PIND tests and preventing solder outflow to the package body's side face, thus enhancing hermetic sealability and reducing appearance inspection defects.
Implementation Method 1
melting once and then solidifying the ball solder to bond the first sealing surface and the second sealing surface
Implementation Method 2
melting once and then solidifying the ball solder to bond the first sealing surface and the second sealing surface
Implementation Method 3
first solder outflow prevention part continuously provided on the first sealing surface and positioned closer to the chip mounting region side than the first recess
Data Source
AI summary
A method includes: providing a package body including a mounting part having a chip mounting region for mounting a semiconductor chip, a side wall part having a first sealing surface continuously provided over an entire perimeter of the mounting part, surrounding the chip mounting region and provided on the mounting part, a first recess provided on the first sealing surface, and a first solder outflow prevention part continuously provided on the first sealing surface and positioned closer to the chip mounting region side than the first recess; providing a cap having a second sealing surface facing the first sealing surface; providing a ball solder made of an alloy of gold and tin as principal ingredients; placing the ball solder in the first recess; placing the cap on the ball solder; and melting once and then solidifying the ball solder to bond the first sealing surface and the second sealing surface.