Surface Mounted Leadframe for LED Heat Dissipation
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Solution Overview
Problem
Conventional surface mounted type LED products face issues with high void ratios in solder paste due to pad design and reflow soldering profiles, leading to poor heat dissipation and increased risk of delamination, especially in larger sizes and low voltage designs.
Innovation Solution
A surface mounted type leadframe with a conductive base and insulating material layer, featuring multiple connecting pads with die bonding and soldering regions, and intermediate sections that fill gaps between pads to reduce void ratios and enhance adhesion, allowing for improved heat dissipation and bonding under low voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solder paste is used for reflow soldering in conventional SMD type LED products, then electrical connection and heat dissipation are achieved, but the void ratio becomes overlarge leading to poor heat dissipation effects
Solution Approach 1:
The connecting pads are divided into multiple smaller pads arranged in an array, with each pad having dedicated die bonding regions and soldering regions. This segmentation allows for better control of solder paste distribution and reduces void formation during reflow soldering, improving both manufacturing precision and heat dissipation reliability.
Solution Approach 2:
The insulating material layer is selectively applied to cover specific regions between connecting pads while leaving soldering regions exposed. This local quality approach ensures proper adhesion in critical areas while maintaining good thermal and electrical properties in soldering areas, reducing void ratio without compromising heat dissipation.
2Power
If sizes of the SMD type product are larger, then higher power is achieved, but each die bonding region becomes larger and the amount of chips in series connection increases making it difficult to achieve low voltage design
Solution Approach 1:
The connecting pads are segmented into multiple pads with alternating anode and cathode polarity. This allows LED chips to be connected in parallel across adjacent anode and cathode pads, reducing the total series connection count and enabling low voltage design while maintaining high power output through increased parallel channels.
Solution Approach 2:
The leadframe structure uses asymmetric arrangement of anode and cathode connecting pads, with different numbers and positions of each polarity. This asymmetric design optimizes the parallel connection configuration for low voltage operation while accommodating high power requirements, simplifying the overall chip configuration complexity.
3Ease of manufacture
If adhesion strengths of silicone glue, metal and insulating materials are relatively weak, then assembly is easier, but delamination can easily occur
Solution Approach 1:
The insulating material layer is pre-applied to the conductive base before mounting LED chips and applying silicone glue. This preliminary action creates a stable foundation with proper adhesion properties, preventing delamination during subsequent assembly steps while maintaining ease of manufacture through a straightforward sequential process.
Data Source
AI summary
A surface mounted type leadframe includes a conductive base and an insulating material layer. The conductive base includes at least three connecting pads spaced apart from each other. First surface of the connecting pads are configured to form die bonding regions, and second surfaces of the connecting pads opposite to the first surfaces are configured to form soldering regions. The insulating material layer at least partially covers the first surfaces, surrounds the die bonding regions, and is filled in a gap between each two adjacent connecting pads. A photoelectric device with multi-chips adopting the surface mounted type leadframe is also provided.