Lead Frame Coupling Protrusions for Semiconductor Package Reliability
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Solution Overview
Problem
Conventional semiconductor packages experience reduced coupling strength and electrical reliability due to over-collapsed solders during reflowing, and the use of flux adds complexity to the process.
Innovation Solution
A semiconductor package design featuring a lead frame with integrally formed coupling protrusions that penetrate through solders to connect chip bumps, eliminating the need for flux and maintaining consistent solder height, thereby enhancing electrical reliability and coupling strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solders are used for connection between lead frame and chip during reflowing, then electrical connection is achieved, but coupling strength and electrical reliability decline when solders become over-collapsed
Solution Approach 1:
The lead is divided into distinct functional portions: a first end portion for electrical connection, a half-etched portion for structural support, and coupling protrusions for mechanical interlocking. This segmentation allows each portion to optimize its specific function, preventing the degradation of coupling strength that occurs with conventional solder-only connections.
Solution Approach 2:
The coupling protrusions are pre-formed on the lead before the bonding process. These protrusions are designed to embed into the solders during reflowing, creating a mechanical interlock structure in advance that prevents solder collapse and maintains coupling strength throughout the bonding process.
2Ease of manufacture
If flux is added during reflowing process, then soldering is facilitated, but process complexity increases due to flux removal requirement
Solution Approach 1:
The invention extracts and eliminates the flux component from the soldering process. By designing coupling protrusions that mechanically interlock with solders during reflowing without requiring flux, the patent removes the need for flux application and subsequent removal steps, thereby reducing process complexity while maintaining ease of manufacture.
3Ease of manufacture
If conventional leads are used without coupling protrusions, then manufacturing is simpler, but electrical reliability and coupling strength are reduced
Solution Approach 1:
The lead is designed with local quality variations: the first end portion has specific surface characteristics for solder attachment, the half-etched portion provides structural integrity, and coupling protrusions are strategically positioned to embed into solders. This localized differentiation of properties enhances electrical reliability and coupling strength without significantly complicating the overall manufacturing process.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design improves electrical reliability and coupling strength between the lead frame and chip while simplifying the process by eliminating the need for flux and maintaining consistent solder height through the use of fixed-height coupling protrusions.
Implementation Method 1
A conventional semiconductor package utilizes solders for connection between a lead frame and a chip
Implementation Method 2
In heat lamination process of the present invention, by means of the coupling protrusions integrally formed as one piece with the leads
Data Source
AI summary
A semiconductor package includes a lead frame, at least one chip and a molding compound. The lead frame comprises a plurality of leads, each lead comprises a first end portion and at least one coupling protrusion, wherein the first end portion comprises a first upper surface, the coupling protrusion comprises a ring surface and is integrally formed as one piece with the first upper surface. The chip disposed on top of the leads comprises a plurality of bumps and a plurality of solders, the coupling protrusions embed into the solders to make the ring surfaces of the coupling protrusions cladded with the solders. The solders cover the first upper surfaces. The chip and the leads are cladded with the molding compound.