Heatsink Step Structure for Molded Semiconductor Package Adhesion
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Solution Overview
Problem
In semiconductor devices with a transfer molding structure, detachment between the heatsink and the sealing material occurs during reliability tests, leading to a decrease in insulation and heat radiation properties.
Innovation Solution
A semiconductor device design featuring a heatsink with an extension part and a two-stage level difference on its side part, which provides an anchor effect to prevent detachment between the heatsink and the sealing material, maintaining insulation and heat radiation properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a single level difference is provided to the heatsink side part, then bonding between heatsink and sealing material is improved, but detachment can still reach the interface between insulating sheet and heatsink
Solution Approach 1:
The level difference is divided into two distinct stages: a first level difference extending from the outer peripheral side toward the inner peripheral side, and a second level difference extending further inward. This segmentation creates multiple bonding interfaces and anchor points, preventing detachment from propagating from the sealing material interface to the insulating sheet interface.
Solution Approach 2:
The extension part protrudes outward from the side part of the heatsink in a direction perpendicular to the main body, creating an additional dimensional feature. This extension part works in conjunction with the two-stage level difference to provide enhanced mechanical interlocking and prevent detachment in multiple directions.
2Object-affected harmful factors
If the heatsink and sealing material are firmly bonded, then moisture ingress is prevented, but detachment occurs during reliability tests reaching the insulating sheet interface
Solution Approach 1:
The two-stage level difference structure is pre-formed on the heatsink before assembly with the sealing material. This preliminary structural preparation ensures that when the sealing material is applied, it bonds to multiple levels and creates redundant attachment points, preventing detachment even under thermal and mechanical stress during reliability testing.
Solution Approach 2:
The level differences create stepped surfaces that increase the bonding area and create mechanical interlocking features. The geometric configuration of the stepped surfaces provides curvature and surface variation that enhances adhesion and prevents planar detachment.
Data Source
AI summary
A semiconductor device includes: a heatsink, an insulating sheet, a frame disposed on the insulating sheet, semiconductor elements mounted on the frame; and the sealing material sealing the heatsink, the insulating sheet, the frame, and the semiconductor elements while a surface of the heatsink on a side opposite to a surface to which the insulating sheet is attached and a part of the frame are exposed. An extension part extending to an outer peripheral side is provided to a part of a side part of the heatsink on a side of a surface to which the insulating sheet is attached, and provided to the side part of the heatsink is a level difference including at least two stages of a first level difference concaved from the extension part to an inner peripheral side and a second level difference concaved further to an inner peripheral side.