Solder Wetting Structure for Semiconductor Package Short Prevention
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Solution Overview
Problem
Solder shorting occurs during the production of semiconductor packages due to the flow of liquid solder towards the direction of an overhang between the die and the clip, leading to undesired bridging and shorts.
Innovation Solution
A solder wetting structure is metallurgically welded to the substrate outside the perimeter of the semiconductor die, adjacent to its side faces, to metallurgically bond excess solder that squeezes out during production, preventing it from bridging to other regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If flux-free solder is used with high temperature die attach and clip attach processes, then solder joint strength is improved, but solder bridging and shorting occur due to liquid solder flow towards the clip overhang
Solution Approach 1:
A solder wetting structure (solder barrier structure) is introduced as an intermediary element between the die and the clip. This structure acts as a mediator that captures and bonds excess solder, preventing it from bridging to the clip. The barrier structure is metallurgically bonded to the substrate and positioned to intercept solder flow before it reaches the clip overhang area.
Solution Approach 2:
The harmful liquid solder that flows away from the die attach area is extracted and redirected to bond with the solder wetting structure instead of shorting to the clip. By providing a dedicated bonding target for the excess solder, the harmful flow is converted into a useful bonding action that enhances joint strength while preventing shorts.
2Ease of operation
If the clip is positioned with overhang beyond the die perimeter, then electrical connection is improved, but liquid solder flows towards the overhang causing shorts
Solution Approach 1:
The solder wetting structure serves as an intermediary barrier between the die attach area and the clip overhang. It intercepts the liquid solder flow that would otherwise bridge to the clip, while allowing the clip to maintain its functional overhang position for proper electrical connection.
Solution Approach 2:
The excess solder that would cause harm by bridging to the clip is converted into a beneficial element by directing it to bond with the solder wetting structure. This transforms the harmful solder flow into a useful bonding action that strengthens the connection between the barrier structure and the substrate.
3Strength
If multiple pass soldering is performed for die attach and clip attach, then metallurgical bonding is improved, but process complexity and manufacturing time increase
Solution Approach 1:
The solder wetting structure is pre-positioned and metallurgically bonded to the substrate before the die attach process. This preliminary action prepares the structure to automatically capture and bond excess solder during subsequent soldering operations, eliminating the need for additional complex process steps to manage solder flow.
Solution Approach 2:
The solder wetting structure performs self-service by automatically capturing and bonding excess solder that flows during the die attach and clip attach processes. This self-bonding capability eliminates the need for additional manual intervention or complex process controls to prevent solder bridging.
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
Prevents solder bridging and shorts by effectively bonding excess solder to the solder wetting structure, enhancing package reliability and reducing manufacturing defects.
Implementation Method 1
excess solder squeezed out from under the semiconductor die is metallurgically bonded to the solder wetting structure
Implementation Method 2
a solder wetting structure metallurgically welded to the metallic surface of the substrate outside a perimeter of the semiconductor die
Data Source
AI summary
A semiconductor package includes: a substrate having a metallic surface; a semiconductor die metallurgically bonded to the metallic surface of the substrate by a first solder joint; and a solder wetting structure metallurgically welded to the metallic surface of the substrate outside a perimeter of the semiconductor die and adjacent to one or more side faces of the semiconductor die. Excess solder squeezed out from under the semiconductor die is metallurgically bonded to the solder wetting structure. Methods of producing the semiconductor package and solder wetting structure are also described.