Semiconductor Lead Terminal Protrusion for Solder Fillet Stability
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Solution Overview
Problem
In substrate inserted lead-type semiconductor devices, forming stable solder fillets is challenging due to gravitational stress and variations in solder shape, temperature, and solder amount, making it difficult to achieve consistent bonding between lead terminals and substrates.
Innovation Solution
The semiconductor device features lead terminals with protrusions on one end that protrude from the sealing resin, allowing for improved thermal capacity and surface tension-assisted solder wetting, enabling stable solder fillet formation on the substrate by increasing the local volume of the lead terminals and utilizing surface tension to direct solder flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lead terminals are inserted into substrate through holes with intermediate portions joined to substrate, then substrate inserted lead-type semiconductor device is formed, but solder fillets cannot be stably formed due to gravitational stress causing solder to flow downward
Solution Approach 1:
The patent applies local quality by forming protrusions at specific locations on the lead terminals (at the intermediate portions that will be joined to the substrate). These protrusions locally increase the volume and thermal capacity at critical bonding points, enabling stable solder fillet formation despite gravitational stress. The protrusions are strategically positioned to counteract the downward flow of solder caused by gravity, creating localized zones of improved solder wetting and fillet stability.
Solution Approach 2:
The patent changes the physical parameters of the lead terminals by adding protrusions that increase the local volume and thermal capacity. This parameter change allows the lead terminals to maintain higher temperatures at the bonding interface, improving solder wetting and fillet formation. The protrusions effectively modify the thermal and geometric parameters at critical locations to overcome the adverse effects of gravity on solder flow.
2Strength
If surfaces of lead terminals are processed to improve bonding to sealing resin and solder, then bonding is improved, but solder fillet formation remains unstable due to gravitational stress
Solution Approach 1:
The patent applies local quality by forming protrusions at specific locations on the lead terminals (at the intermediate portions that will be joined to the substrate). These protrusions locally increase the volume and thermal capacity at critical bonding points, enabling stable solder fillet formation despite gravitational stress. The protrusions are strategically positioned to counteract the downward flow of solder caused by gravity, creating localized zones of improved solder wetting and fillet stability.
Solution Approach 2:
The protrusions create an asymmetric geometry on the lead terminals, with increased volume at specific bonding locations. This asymmetry allows the lead terminals to maintain higher temperatures at the bonding interface, improving solder wetting and fillet formation. The asymmetric shape with protrusions enables better control over solder flow and fillet formation compared to uniform lead terminal designs.
3Ease of manufacture
If solder fillets are formed with variations in amount of solder, temperature, and lead terminal conditions, then bonding is achieved, but solder fillet shapes vary and stable formation cannot be achieved
Solution Approach 1:
The patent changes the physical parameters of the lead terminals by adding protrusions that increase the local volume and thermal capacity. This parameter change allows the lead terminals to maintain higher temperatures at the bonding interface, improving solder wetting and fillet formation. The protrusions effectively modify the thermal and geometric parameters at critical locations to overcome the adverse effects of gravity on solder flow.
Solution Approach 2:
The protrusions are formed on the lead terminals before the soldering process, preparing the surface geometry and thermal characteristics in advance. This preliminary action ensures that when solder is applied, the protrusions are already in position to guide solder flow and maintain temperature, leading to consistent fillet formation despite variations in soldering conditions.
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 design ensures stable and consistent formation of solder fillets on the substrate, enhancing bonding reliability and reducing the amount of solder required, while maintaining manufacturing cost efficiency through the use of press molds to form the protrusions.
Implementation Method 1
the solder fillets can stably be formed at mounting on the substrate in the substrate inserted lead-type semiconductor device
Implementation Method 2
utilizing surface tension to direct solder flow
Data Source
AI summary
A semiconductor device is a substrate inserted lead-type semiconductor device to be mounted through insertion of a plurality of lead terminals into a plurality of respective through holes of a substrate. The semiconductor device includes: an energization controller including a semiconductor element and wiring; a sealing resin to cover the energization controller; and the lead terminals each having one end side connected to the energization controller and the other end side protruding from the sealing resin. The lead terminals each have a protrusion formed on a part of the other end side protruding from the sealing resin.