LED Module Asymmetric Die Pad for Bonding Reliability
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Solution Overview
Problem
Conventional LED modules face issues with misalignment during the die bonding process, leading to potential peeling or shifting of LED chips due to stress, which necessitates a larger substrate size to accommodate misalignment, resulting in a less compact design.
Innovation Solution
The LED module incorporates a die pad portion with an auxiliary pad that protrudes from the main pad portion towards the electrode pad, allowing for misalignment compensation without increasing the overall size, ensuring the electrode pad does not protrude and enhancing bonding reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the die pad portion is uniformly formed to be large in all directions from the outer periphery of the LED chip, then the bonding reliability is improved, but the size of the LED module increases
Solution Approach 1:
The die pad portion is designed with non-uniform dimensions, extending further in the direction where the electrode pad is located compared to other directions. This local extension provides additional margin specifically where misalignment is most critical, while keeping other dimensions compact, thus resolving the contradiction between bonding reliability and module size.
Solution Approach 2:
The die pad portion employs asymmetric dimensions where the extension distance varies by direction. Specifically, it extends a first distance in the direction of the electrode pad and a second distance in the opposite direction, with the first distance being greater than the second. This asymmetric design optimizes the coverage area to prevent electrode pad protrusion while minimizing overall size increase.
2Reliability
If misalignment compensation is provided in all directions uniformly, then the bonding reliability is improved, but the device complexity increases
Solution Approach 1:
Instead of uniform extension in all directions, the die pad portion provides localized extension primarily in the direction where the electrode pad is positioned. This targeted approach compensates for misalignment where it matters most while avoiding unnecessary structural complexity in other directions.
Data Source
AI summary
An LED module includes: a substrate having a main surface and a back surface which face in opposite directions from each other in a thickness direction; a first LED chip including a first electrode pad bonded to a surface facing the same direction as the main surface; a first wire having one end bonded to the first electrode pad; and a wiring pattern having a main surface electrode formed in the main surface, wherein the main surface electrode includes a first die pad portion which supports the first LED chip, and when viewed from the thickness direction, the first die pad portion includes a main pad portion to which the first LED chip is bonded and an auxiliary pad portion which protrudes from the main pad portion in a direction toward a position of the first electrode pad from the center position in the first LED chip.