Leadframe Temporary Connection Bars Molding Stability

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Solution Overview

Problem

Conventional pre-molded leadframe technologies face challenges with undesired displacement and deformation during the molding process, leading to electrical insulation issues, reduced pin count, increased package size, and design constraints, especially with complex designs having multiple die pads.

Innovation Solution

The implementation of half-etched temporary connection bars on the leadframe, which are sacrificial and located on the bottom side, helps maintain the leadframe structure during etching and molding, reducing deformation and allowing for stronger stability while enabling the accommodation of multiple pads without design constraints.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If multiple connection bars are used to lock all pads/paddles, then displacement during molding is reduced, but pin count decreases and package size increases

Engineering Contradiction:

Improveleadframe stabilityVSAvoidpin count

Core Design Contradiction:

Stability of the object's compositionVSProductivity

Solution Approach 1:

The connection bars are segmented into two functional types: permanent connection bars that provide structural support and electrical connections, and temporary connection bars that are removed after serving their stabilizing function during molding. This segmentation allows the leadframe to achieve stability during the molding process without permanently sacrificing connection points, thereby maintaining higher pin count in the final product.

Inventive Principle:

Principle #1Segmentation

2Stability of the object's composition

If multiple connection bars are used to lock all pads/paddles, then displacement during molding is reduced, but device complexity increases

Engineering Contradiction:

Improveleadframe stabilityVSAvoiddesign constraints

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

Temporary connection bars are pre-positioned at strategic locations before the molding process to provide necessary structural support during filling. These bars are removed after serving their purpose, leaving no permanent constraints on the design. This preliminary action approach allows complex multi-pad designs to be manufactured without the complexity of permanently configuring multiple connection bars.

Inventive Principle:

Principle #10Preliminary action

3Manufacturing precision

If connection bars are added to stabilize pads, then deformation during molding is reduced, but available leadframe area decreases

Engineering Contradiction:

Improvedeformation controlVSAvoidleadframe area

Core Design Contradiction:

Manufacturing precisionVSArea of stationary object

Solution Approach 1:

Temporary connection bars are designed as disposable, low-cost structural aids that are removed after the molding process. These bars provide necessary deformation control during manufacturing but do not permanently occupy valuable leadframe area. Their temporary nature allows full utilization of the leadframe area for functional pads and leads in the final product.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

4Ease of manufacture

If conventional molding is used without temporary connections, then manufacturing process is simpler, but displacement and deformation occur

Engineering Contradiction:

Improvemolding processVSAvoidposition accuracy

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

Temporary connection bars serve as intermediary structural elements during the molding process, providing mechanical support to pads and preventing displacement. These intermediaries are removed after serving their stabilizing function, leaving the leadframe with accurate pad positions without requiring complex permanent structural modifications. This approach maintains manufacturing simplicity while achieving high position accuracy.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS20220199500A1Method of manufacturing semiconductor devices, component for use therein and corresponding semiconductor device

Publication Date: 2022.06.23 STMICROELECTRONICS SRL

AI summary

A leadframe includes a pattern of electrically-conductive formations with one or more sacrificial connection formations extending bridge-like between a pair of electrically-conductive formations. The sacrificial connection formation or formations are formed at one of the first surface and the second surface of the leadframe and have a thickness less than the leadframe thickness between the first surface and the second surface. A filling of electrically-insulating material is molded between the electrically-conductive formations of the leadframe, with electrically-insulating material molded between the connection formation(s) and the other surface of the leadframe. The sacrificial connection formation(s) counter deformation and displacement of parts during formation and pre-molding of the leadframe.