Semiconductor Side Emitting Laser Leadframe Package
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Solution Overview
Problem
Current surface mount designs for semiconductor lasers have high inductance and resistance, which are inadequate for applications like LIDAR where rapid discharge and recharge are required, necessitating a more efficient packaging solution.
Innovation Solution
A semiconductor side emitting laser leadframe package with a substantially planar leadframe, thin metal construction, and a molding that encases the laser die and bond wires, reducing inductance and thermal resistance while maintaining low manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thick PCB or ceramic substrate is used to mount the laser array die, then the mechanical strength and stability are improved, but the inductance and resistance increase, which is inadequate for rapid discharge and recharge applications
Solution Approach 1:
The patent extracts the laser die from the traditional thick PCB substrate and mounts it directly onto a thin leadframe. This removes the unnecessary thick substrate that caused high inductance and resistance, while retaining the mechanical support function through the leadframe structure. The laser die is directly attached to the leadframe body, eliminating the intermediate thick substrate layer.
Solution Approach 2:
The patent employs a thin leadframe structure instead of a thick PCB or ceramic substrate. The leadframe provides mechanical support while maintaining thin profile and low inductance. The thin leadframe body serves as both the mounting platform and the electrical connection path, reducing the harmful inductance and resistance associated with thick substrates.
2Reliability
If wire bond pads are connected to surface mount pads through through vias, then electrical connection is established, but the inductance and resistance become too high for LIDAR applications requiring rapid discharge and recharge
Solution Approach 1:
The patent eliminates the through via connection path that caused high inductance and resistance. Instead of routing electricity through the thick substrate via holes, the electrical connections are made directly on the leadframe surface through metallization layers, removing the harmful intermediate connection path.
Solution Approach 2:
The patent transitions from three-dimensional through via connections (going through the substrate thickness) to two-dimensional surface metallization connections. The electrical pathways are established on the surface plane of the leadframe rather than penetrating through the substrate, significantly reducing the connection length and associated inductance.
3Ease of manufacture
If a traditional SMD package with thick substrate is used, then manufacturing is straightforward, but the package size and inductance are reduced, which is necessary for improved laser pulse width
Solution Approach 1:
The patent extracts the laser die mounting function from the thick PCB substrate and transfers it to a thin leadframe. This maintains manufacturing simplicity by using a familiar leadframe structure while eliminating the excessive substrate thickness that contributed to package height and inductance.
Solution Approach 2:
The patent uses a thin leadframe structure that provides sufficient mechanical support and electrical connection functionality without the excessive thickness of traditional PCB substrates. The thin leadframe achieves the desired low inductance and compact package height while remaining manufacturable using standard leadframe processing techniques.
Data Source
Figure 1A~1C
Figure 2
Figure 3A~3C
AI summary
A surface mount laser package for a side-looking semiconductor laser has a substantially planar leadframe with a component side and a board attach side. The component side has a conductive die attach pad and a plurality of wire bond pads. A laser die has an anode surface and a cathode surface, where the cathode surface is mounted to the conductive die attach pad. A plurality of bond wires span between the laser die anode surface and a wire bond pad. A molding encases the laser die and the plurality of bond wired on the component side of the leadframe and also lies between the conductive die attach pad and each of the wire bond pads within a plane of the leadframe. The conductive die attach pad has a metallization layer on the leadframe and each of the bond pads has a metallization layer on the leadframe.