Variable-Width Leadframe Package to Reduce Delamination Stress

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Solution Overview

Problem

Mold compound delamination and wire pull off defects are common issues in leaded electronic device packages, particularly during thermal cycle tests, due to mechanical stress during the lead forming process.

Innovation Solution

The use of leads with a first portion having a first width and a second portion with a greater width, where the first portion is narrower near the package body to reduce mechanical stress during lead forming, thereby minimizing delamination and wire pull off defects.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If leads with uniform width are used throughout, then manufacturing simplicity is maintained, but mechanical stress during lead forming causes delamination and wire pull off defects

Engineering Contradiction:

Improvedelamination defect reductionVSAvoidlead structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The lead structure implements local quality by having different widths at different portions: a first portion with width W1 extending from the mold compound, and a second portion with width W2 (where W2 > W1) extending to the end. This non-uniform width distribution optimizes mechanical stress characteristics at critical locations while maintaining overall structural integrity, directly addressing the delamination and wire pull off defects without requiring complete structural redesign

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The lead is segmented into distinct portions with different widths - the first portion (width W1) near the mold compound and the second portion (width W2) extending to the end. This segmentation allows each portion to serve different functional requirements: the narrower first portion reduces mechanical stress at the critical mold compound interface, while the wider second portion provides sufficient mechanical strength at the distal end

Inventive Principle:

Principle #1Segmentation

2Strength

If lead width is increased to reduce stress, then mechanical strength improves, but stress concentration during forming increases causing wire pull off defects

Engineering Contradiction:

Improvelead mechanical strengthVSAvoidwire pull off defects

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The invention applies parameter changes by varying the lead width parameter along its length. The first portion has width W1 and the second portion has width W2 where W2 > W1. This parameter variation optimizes the balance between mechanical strength and stress distribution, preventing wire pull off defects by reducing stress concentration at the mold compound interface while maintaining adequate strength at the lead end

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS12334417B2Leaded semiconductor device package having leads with different widths

Publication Date: 2025.06.17 TEXAS INSTRUMENTS INC

AI summary

In a described example, an apparatus includes: a package substrate having a die pad configured for receiving a semiconductor die, and having conductive leads spaced from the die pad; a semiconductor die mounted on the die pad, the semiconductor die having bond pads on an active surface configured for making electrical connections; electrical connections coupling the bond pads of the semiconductor die to the conductive leads; mold compound covering a portion of the package substrate, the semiconductor die, and the electrical connections, with the leads extending through the mold compound and having end portions exposed from the mold compound; and the leads having a first portion with a first width and extending with the first width from the mold compound to a second portion having a second width that greater than the first width.