Lateral Thyristor Photocoupler for Manufacturing Efficiency
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Solution Overview
Problem
The manufacturing process of photocouplers using thyristors with a vertical structure is lengthy due to impurity diffusion, resulting in low manufacturing efficiency and long lead times, necessitating the development of a photocoupler with a thyristor in a lateral structure for improved efficiency.
Innovation Solution
A semiconductor device incorporating a thyristor-type light-receiving element with a lateral structure, where the light-receiving element is die-bonded onto a lead frame with a thinner insulator, allowing for direct connection using an insulating adhesive and reducing the manufacturing time and complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thyristor with a vertical structure is used, then the peak forward blocking voltage requirement (400V to 600V) is satisfied, but the manufacturing process becomes lengthy due to impurity diffusion, resulting in low manufacturing efficiency
Solution Approach 1:
The patent inverts the conventional vertical structure of the thyristor to a lateral structure. Instead of current flowing vertically from front face to back face, the current now flows laterally within the same substrate plane. This inversion eliminates the need for lengthy impurity diffusion processes while maintaining the required voltage blocking capability, thus resolving the contradiction between reliability and manufacturing efficiency
2Reliability
If a thyristor with a vertical structure is used, then the required voltage blocking capability is achieved, but the manufacturing lead time increases, resulting in long turnaround time
Solution Approach 1:
By inverting the vertical structure to a lateral structure, the manufacturing process is dramatically shortened. The lateral structure allows for simpler fabrication steps that do not require lengthy impurity diffusion, thereby reducing manufacturing lead time while preserving the voltage blocking capability through optimized lateral device geometry and material layers
3Productivity
If a thinner insulator is used in the lead frame, then manufacturing time and complexity are reduced, but the risk of electrical insulation failure may increase
Solution Approach 1:
The patent employs composite material strategies where the thinner insulator is combined with optimized lead frame geometry and additional insulating layers in critical areas. This composite approach maintains adequate electrical insulation while enabling the use of thinner insulators overall, thus reducing manufacturing complexity and time without compromising reliability
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 enhances manufacturing efficiency, suppresses chip face slanting, and facilitates wire bonding, thereby improving the overall production process and optical coupling efficiency between the light-emitting and light-receiving elements.
Implementation Method 1
a light-emitting element electrically connected to the primary side lead
Implementation Method 2
a thyristor-type light-receiving element that is turned on by photocurrent
Data Source
AI summary
According to an embodiment, a semiconductor device includes a primary side lead, a light-emitting element electrically connected to the primary side lead, and a thyristor-type light-receiving element. The light-receiving element includes a first face for detecting light emitted from the light-emitting element, and a second face provided on an opposite side of the first face. The light-receiving element includes an anode electrode, a cathode electrode, and a gate electrode that are provided on the first face. The device further includes a secondary side first lead electrically connected to the anode electrode, a secondary side second lead electrically connected to the cathode electrode, and a secondary side third lead electrically connected to the gate electrode. The secondary side third lead is connected to the second face of the light-receiving element.