Semiconductor Terminal Structure for Stronger Solder Bonding
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Solution Overview
Problem
The reduction in terminal reverse surface area due to increased number of terminals in semiconductor devices leads to decreased bonding strength to the wiring board, primarily because of reduced contact area with solder.
Innovation Solution
The semiconductor device design includes terminals with projection portions and covering layers that increase the contact area with solder, and a sealing resin with a rough bottom surface to enhance bonding strength, while maintaining device size and simplifying manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of terminals is increased to achieve further circuit integration and downsizing, then the device integration density is improved, but the area of each terminal reverse surface is reduced, leading to decreased bonding strength
Solution Approach 1:
The patent extends the terminal structure in the thickness direction (vertical dimension) by adding projection portions that protrude from the sealing resin surface. This dimensional extension increases the solder contact area without increasing the planar footprint, thereby maintaining bonding strength while accommodating higher terminal density for circuit integration.
Solution Approach 2:
The patent modifies the terminal geometry parameters by adding projection portions with specific dimensions (protruding distance d1, width w1, length l1) and forming covering layers with specific thickness (d2). These parameter changes increase the effective solder contact area from the original flat surface to a multi-faceted structure with enhanced surface area, resolving the bonding strength issue while maintaining device downsizing.
2Volume of moving object
If the terminal reverse surface area is reduced to accommodate more terminals, then the device miniaturization is achieved, but the contact area with solder is reduced, resulting in decreased bonding strength
Solution Approach 1:
The patent compensates for the reduced planar terminal surface area by extending the terminal structure vertically through projection portions that protrude from the sealing resin. This transforms the bonding interface from a two-dimensional contact to a three-dimensional multi-faceted contact, increasing the effective solder contact area while maintaining the compact device footprint.
Solution Approach 2:
The patent employs composite material structures by forming covering layers (conductive material) over the projection portions of the terminals. This composite structure enhances the solder wettability and bonding strength through the combination of the base terminal material, projection geometry, and covering layer material, thereby maintaining strong bonding despite reduced terminal surface area.
3Strength
If a terminal conductive layer is added to improve solder wettability, then the bonding strength is enhanced, but the manufacturing process becomes more complex
Solution Approach 1:
The patent merges the terminal conductive layer formation with the existing sealing resin curing process. The covering layers are formed over the projection portions while the sealing resin is being cured, allowing these two operations to be performed simultaneously or in closely integrated sequence, thereby reducing manufacturing steps and simplifying the overall process while still achieving enhanced solder wettability and bonding strength.
Data Source
AI summary
A semiconductor device comprising a terminal, a semiconductor element and a sealing resin. The semiconductor element is disposed on one side of the terminal in a first direction and electrically connected to the terminal. The sealing resin covers the semiconductor element and a part of the terminal. The sealing resin has a bottom surface disposed on an opposite side to the semiconductor element with respect to the terminal in the first direction. The terminal extends beyond the bottom surface.