Optical Semiconductor Package Layout to Prevent Adhesive Short-Circuits
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Solution Overview
Problem
The manufacturing of semiconductor devices with light emitting and receiving elements is hindered by high costs and reliability issues due to complex processing techniques and potential short-circuiting from conductive adhesives, especially as package size increases.
Innovation Solution
A semiconductor device design featuring a die pad with distinct thickness regions and through holes, where the light emitting and receiving elements are positioned with precise alignment using conductive and insulating adhesive layers, ensuring electrical insulation and minimizing the risk of short-circuits, while simplifying the manufacturing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the light emitting element and light receiving element are simply arranged on the lead frame having a constant thickness, then the manufacturing process is simplified, but the conductive adhesive may come into contact with the side or lower surface of the light receiving element, causing short-circuiting and deteriorating reliability
Solution Approach 1:
The die pad is segmented into two regions with different thicknesses: a first region with smaller thickness for mounting the light receiving element, and a second region with larger thickness for mounting the light emitting element. This segmentation creates physical separation that prevents conductive adhesive from causing short-circuits while maintaining manufacturing simplicity.
Solution Approach 2:
Different regions of the die pad are given different local qualities (thickness values) to serve different functions. The first region has optimized thickness for insulation and light receiving element mounting, while the second region has increased thickness for light emitting element mounting, allowing each area to perform its specific function optimally without compromising overall reliability.
2Device complexity
If the light emitting element and light receiving element are mounted without using a die pad, then the device structure is simplified, but it becomes difficult to ensure mounting reliability especially as the size of the package increases
Solution Approach 1:
Instead of using a simple flat die pad or no die pad, the invention segments the die pad into two thickness regions, creating a structured solution that provides both mechanical support and electrical insulation, thereby ensuring mounting reliability while maintaining reasonable structural complexity.
3Measurement precision
If the concave portion is provided in the light receiving element to achieve coplanar mounting, then the light detection sensitivity is improved, but the processing technique becomes highly difficult and the number of manufacturing steps increases, causing increase in manufacturing cost
Solution Approach 1:
Instead of modifying the light receiving element by creating a concave portion (complex processing), the invention inverts the approach by modifying the die pad structure itself with two different thickness regions. This achieves the coplanar mounting effect and improved light detection sensitivity while avoiding complex processing of the light receiving element, thereby reducing manufacturing cost.
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 reduces manufacturing costs, enhances reliability by preventing short-circuits, and maintains detection accuracy with precise alignment of light emitting and receiving surfaces, supporting miniaturization without compromising performance.
Implementation Method 1
a conductive first adhesive layer
Implementation Method 2
an insulating adhesive layer
Data Source
AI summary
The increase in manufacturing cost is suppressed and reliability of a semiconductor device is improved. A semiconductor device 1 includes a light emitting element 2, a light receiving element 3, and a die pad 20 made of a conductive material. The die pad 20 includes a first region 20A and a second region 20B having a thickness greater than that of the first region 20A. The light receiving element 3 is provided on an upper surface of the first region 20A so as to be electrically insulated from the die pad 20. The light emitting element 2 is provided on an upper surface of the second region 20B via a conductive adhesive layer 5 inside a thorough hole 4 of the light receiving element 3. A position of an upper surface of the light emitting element 2 and a position of an upper surface of the light receiving element 3 coincide within a range of 5 □m or less.