Photodetecting Device Wire Bonding Layout
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Solution Overview
Problem
In photodetecting devices with a back-incident type photodetecting element, the space required for wire bonding outside the photodetecting element increases the size of the wiring board, leading to a larger non-sensitive region when arranging multiple devices in a high-density matrix configuration.
Innovation Solution
The photodetecting device is designed with the wiring board positioned at the front surface of the photodetecting element, featuring a first bonding pad exposed in a predetermined region and a second bonding pad formed further inward, allowing the wire bonding space to be internalized, thus equalizing the size of the wiring board and photodetecting element, and incorporating a slit portion, installation face, and lid portion to protect the wire bonding area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wire bonding is performed outside the photodetecting element, then electrical connection is achieved, but the wiring board size increases leading to larger non-sensitive regions
Solution Approach 1:
The patent moves the wire bonding location from the external perimeter (2D plane outside the element) to the internal depth dimension (inside the element structure). By forming the first bonding pad on the front surface and the second bonding pad on the back surface, the wire bonding occurs within the element's thickness dimension, effectively utilizing the Z-axis to reduce the XY-plane footprint.
Solution Approach 2:
The wire bonding structure is nested within the photodetecting element itself. The first bonding pad is formed on the front surface within the element area, and the second bonding pad is formed on the back surface, creating a nested configuration where the bonding path is contained within the element boundaries rather than extending outward.
2Ease of manufacture
If wiring board is made larger to accommodate wire bonding, then wire bonding is possible, but the photodetecting element occupies smaller relative area
Solution Approach 1:
The patent utilizes the thickness dimension of the photodetecting element to accommodate the wire bonding path. By forming bonding pads on both the front and back surfaces and routing wires through the element's depth, the design eliminates the need for lateral expansion of the wiring board, thereby maintaining a high photodetecting element area ratio.
Solution Approach 2:
The patent merges the wire bonding function with the photodetecting element structure itself. The bonding pads are integrated into the element's front and back surfaces, and the wire bonding process is combined with the element fabrication, eliminating the need for a separate, larger wiring board structure.
3Productivity
If multiple photodetecting devices are arranged in high-density matrix, then detection area is increased, but interval between devices must be reduced
Solution Approach 1:
By moving the wire bonding to the internal depth dimension, the patent eliminates the lateral space requirement for bonding operations. This allows photodetecting devices to be positioned closer together in the XY-plane, reducing the interval between devices and enabling higher density matrix arrangements while maintaining full detection area coverage.
Solution Approach 2:
The patent extracts the wire bonding operation from the external perimeter region and relocates it to the internal structure of each device. This extraction removes the need for lateral clearance zones around each device, allowing tighter packing in high-density arrangements.
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 minimizes the non-sensitive region by ensuring the photodetecting element occupies a secure area, reduces the interval between adjacent devices, and protects the wire bonding area from disconnection, maintaining equal pressure within the device and preventing deformation.
Implementation Method 1
a photodetecting element that detects light made incident from a back surface side by a photodetecting section being on a front side of the surface
Implementation Method 2
a second bonding pad electrically connected with the first bonding pad by a bonding wire
Data Source
Figure 1
Figure 2
Figure 3
AI summary
In a photodetecting device 3, a wiring board 12 is provided at the front surface side of a photodetecting element 11 so that a first bonding pad region 15 formed on the front surface of the photodetecting element 11 is exposed, and second bonding pads 17B are formed, of the wiring board 12, in the region on a further inner side than first bonding pads 17A. Thereby, in the photodetecting device 3, a forming space for wire bonding can be located at the inside of the photodetecting element 11, so that the wiring board 12 and the photodetecting element 11 can be made almost equal in size. As a result, in the photodetecting device 3, the area that the photodetecting element 11 occupies relative to the photodetecting device 3 can be sufficiently secured, and minimization of the non-sensitive region in the case of a buttable arrangement of the photodetecting devices 3 on a cold plate 2 can be realized.