Die Paddle Mold Locking Structure for TOL-G Shear Stress Reliability
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Solution Overview
Problem
Transistor outline leaded with gullwing (TOL-G) packages face reliability challenges due to shear stresses from thermal expansion mismatches between the printed circuit board and semiconductor package, affecting performance during temperature cycles.
Innovation Solution
Incorporating a mold locking feature into the semiconductor package, specifically by filling through holes in the die paddle with molding encapsulation and using protrusions with grooves and squeezed extensions that contact the encapsulation, which reduces the exposed die paddle area required for clamping, thereby enhancing reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mold locking feature is introduced to improve reliability, then reliability performance is improved, but package surface area increases
Solution Approach 1:
The patent applies local quality by creating specific localized features (through holes, protrusions, grooves, and swallowtail extensions) on the die paddle surface. These features are concentrated in specific areas rather than uniformly distributed, providing mold locking functionality only where needed. The protrusions with grooves and squeezed extensions with swallowtail shapes create localized interlocking regions that prevent package delamination without requiring additional overall package area.
Solution Approach 2:
The patent transitions from a two-dimensional surface bonding approach to a three-dimensional interlocking approach. By creating through holes that penetrate the die paddle and adding protrusions with grooves and swallowtail extensions that extend vertically, the design utilizes the third dimension (depth/height) to create mechanical interlocking with the molding encapsulation. This vertical dimensionality provides enhanced bonding strength without increasing the horizontal package footprint.
2Strength
If through holes are filled with molding encapsulation to create lock, then shear stress resistance is improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-forming the through holes, protrusions, and swallowtail extensions on the die paddle before the molding encapsulation process. These features are created in advance during lead frame fabrication, so that when the molding encapsulation is subsequently applied, the material naturally fills these pre-prepared cavities and conforms to the pre-formed geometric features. This eliminates the need for complex post-processing steps to create the locking features.
Solution Approach 2:
The molding encapsulation material performs self-service by automatically filling the through holes and conforming to the protrusions and swallowtail extensions during the standard molding process. The material flow and curing process inherently create the locked configuration without requiring additional specialized equipment or complex manufacturing steps. The die paddle features guide the encapsulation material into the desired locked configuration autonomously.
Data Source
AI summary
A semiconductor package comprises a lead frame, a chip, and a molding encapsulation. The lead frame comprises one or more die paddles comprising a first die paddle. The first die paddle comprises one or more through holes, one or more protrusions with grooves on top surfaces of the one or more protrusions, or one or more squeezed extensions. Each of the one or more through holes is filled with a respective portion of the molding encapsulation. Each of the one or more through holes may be of a rectangular shape, a rectangular shape with four filleted corners, a circular shape, or an oval shape. Each of the grooves is filled with a respective portion of the molding encapsulation. A respective side wall of each of the one or more squeezed extensions is of a swallowtail shape. The swallowtail shape directly contacts the molding encapsulation.