Stacked Semiconductor Package Clip Locking Mechanism

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Solution Overview

Problem

Conventional stacked semiconductor packages experience lateral displacement issues due to insufficient adhesive properties of solder paste, leading to defects such as insufficient electrical contact and short circuits during the reflow process.

Innovation Solution

Incorporating mechanical locking features, such as abutting engagement of half etches between leads and clips, or using UV-curable epoxy to stabilize clips and dies, to prevent lateral displacement before the reflow process.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If solder paste is used to adhere dies and clips to the leadframe, then the assembly process is simple, but lateral displacement occurs during reflow heating

Engineering Contradiction:

Improveassembly process simplicityVSAvoidlateral displacement control

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent applies solder paste to the leadframe and die surfaces before assembly, performing the adhesive bonding action in advance. This preliminary application of solder paste creates initial adhesion that helps prevent lateral displacement during subsequent handling and reflow heating, while maintaining the simplicity of the assembly process.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces solder paste as an intermediary substance between the leadframe, dies, and clips. This intermediary material provides adhesive bonding that secures the components in place during assembly and reflow heating, resolving the contradiction between simple assembly and precise positioning by using the solder paste as a mediating element.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Manufacturing precision

If mechanical locking features are added to prevent lateral displacement, then positioning accuracy improves, but device complexity increases

Engineering Contradiction:

Improvelateral displacement controlVSAvoidstructural complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent merges the mechanical locking function with the existing leadframe and clip structures by integrating locking features into these components. Rather than adding separate, independent locking mechanisms, the locking functionality is combined with the structural elements already present in the package, thereby improving positioning accuracy while minimizing the increase in device complexity.

Inventive Principle:

Principle #5Merging (Combining)

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

The mechanical locking features effectively prevent lateral shifting of components, ensuring reliable electrical connections and preventing defects in the stacked semiconductor packages.

Implementation Method 1

using UV-curable epoxy to stabilize clips and dies

Methodology Applied

Scientific EffectPhotopolymerisation: Photopolymerisation

Data Source

PatentUS8883567B2Process of making a stacked semiconductor package having a clip

Publication Date: 2014.11.11 TEXAS INSTRUMENTS INC

AI summary

A method of making a stacked semiconductor package having at least a leadframe, a first die mounted above and soldered to the lead frame and a first clip mounted above and soldered to the first die. The method includes positioning the leadframe, first die and first clip in a vertically stacked relationship and nonsolderingly locking the first clip in laterally nondisplaceble relationship with the leadframe. A stacked semiconductor package and an intermediate product produced in making a stacked semiconductor package are also disclosed.