Leadframe Blind-Hole Structure for Delamination-Resistant Packaging
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Solution Overview
Problem
Semiconductor device packages face delamination issues between the leadframe and mold compound, as well as between the leadframe and the printed circuit board, particularly under stress conditions, with existing solutions like roughening the leadframe surface or half-etching not fully addressing the problem of solder joint cracking during temperature cycling.
Innovation Solution
Incorporating non-through holes, also known as blind holes, in the die pad and lead terminals of the leadframe, which are drilled to a specified depth without breaking through the workpiece, providing a delamination-resistant feature by enhancing mold locking and reducing stress-induced delamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the leadframe surface is roughened or half-etched to reduce delamination, then adhesion between leadframe and mold compound improves, but manufacturing complexity and cost increase
Solution Approach 1:
The patent introduces non-through holes (blind holes) in the leadframe structure that extend partially through the thickness but not completely. These holes create a porous-like structure that mechanically interlocks the mold compound with the leadframe, providing enhanced adhesion without requiring surface roughening or half-etching processes. The holes allow mold compound to penetrate and lock into the leadframe structure, solving the adhesion problem while maintaining simple manufacturing processes.
2Ease of manufacture
If conventional leadframe structures are used, then manufacturing is simple, but delamination occurs between leadframe and mold compound under stress
Solution Approach 1:
The patent segments the leadframe structure by introducing multiple non-through holes at specific locations and orientations. This segmentation creates distinct zones that mechanically interlock with the mold compound, preventing delamination under stress while maintaining the overall simplicity of the leadframe manufacturing process. The holes are strategically placed to provide structural reinforcement without complicating the stamping or forming processes.
3Temperature
If solder joints are subjected to temperature cycling, then thermal performance is maintained, but solder joints crack and delamination occurs
Solution Approach 1:
The patent implements non-through holes that create mechanical cushioning zones within the leadframe structure. These holes provide stress relief and accommodate thermal expansion/contraction differences between materials during temperature cycling. By pre-positioning these stress-absorbing features, the structure prevents crack propagation in solder joints and maintains integrity under thermal cycling conditions.
Data Source
AI summary
A packaged semiconductor device includes a semiconductor die having a top side including a semiconductor surface layer having circuitry configured for a function coupled to bond pads, and a bottom side. A leadframe includes a die pad and leads or lead terminals on at least two sides of the die pad. At least one non-through hole for delamination prevention is in at least one of the die pad and the lead or the lead terminals. The semiconductor die is mounted by a die attach material with the bottom side down on the die pad. A mold compound provides encapsulation for the package semiconductor device except for at least a bottom side of the lead terminals or sidewalls of the package for the leads. The non-through hole is a filled hole filled with either the die attach material or the mold compound.