Pre-molded Leadframe Window for Optical Semiconductor Light Transmission
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Solution Overview
Problem
The manufacturing of optical semiconductor packages is complex due to the need for light to pass through the package while maintaining structural integrity and environmental protection, which is challenging with existing methods that require additional steps and risk blocking the light path.
Innovation Solution
A method involving a semiconductor die with an optically active area and a substrate with a light transmitting region, where an elevated area on the substrate blocks encapsulant material to ensure light transmission, simplifying the manufacturing process and preventing interference with light passage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If additional manufacturing steps are added to ensure light transmission, then light transmission is improved, but manufacturing complexity increases
Solution Approach 1:
The leadframe is pre-molded with a window structure before the semiconductor die is attached. This preliminary formation of the light-transmitting opening eliminates the need for subsequent steps to create openings in the substrate, thereby reducing manufacturing complexity while ensuring proper light transmission to the optically active area.
2Illumination intensity
If opening formation and alignment steps are added, then light passage is ensured, but manufacturing steps and complexity increase
Solution Approach 1:
The window structure is integrated into the leadframe during the initial molding process, combining the functions of structural support and light transmission guidance. This merging of functions eliminates separate steps for opening formation and alignment, reducing the total number of manufacturing steps while ensuring proper light passage.
3Strength
If underfill material and molding compound are applied, then structural integrity and environmental protection are improved, but light passage may be blocked
Solution Approach 1:
The leadframe is divided into distinct regions: a window portion that remains open or is filled with light-transmitting material to allow light passage, and other portions that are filled with underfill material and molding compound for structural integrity and environmental protection. This segmentation allows different materials to be applied in different areas, maintaining both structural strength and light transmission.
4Illumination intensity
If precise alignment is required for light passage, then light transmission is improved, but manufacturing precision requirements increase
Solution Approach 1:
The window is pre-formed in the leadframe with proper alignment features before the semiconductor die is mounted. This preliminary alignment structure guides the placement of the die, reducing the precision requirements during the assembly process while ensuring proper alignment of the optically active area with the light transmission path.
Data Source
AI summary
A semiconductor device is made by providing a semiconductor die having an optically active area, providing a leadframe or pre-molded laminated substrate having a plurality of contact pads and a light transmitting material disposed between the contact pads, attaching the semiconductor die to the leadframe so that the optically active area is aligned with the light transmitting material to provide a light transmission path to the optically active area, and disposing an underfill material between the semiconductor die and leadframe. The light transmitting material includes an elevated area to prevent the underfill material from blocking the light transmission path. The elevated area includes a dam surrounding the light transmission path, an adhesive ring, or the light transmission path itself can be the elevated area. An adhesive ring can be disposed on the dam. A filler material can be disposed between the light transmitting material and contact pads.