Non-Screen Solder Printing for SAC Alloy Alignment

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Current soldering technologies, such as Sn, Ag solder, face limitations in current capacity and reliability due to electromigration, while SAC solder is not suitable for plating applications and suffers from misalignment and manufacturability issues in screen printing processes.

Innovation Solution

A non-screen printing process deposits solder alloys like SAC on lead frames or semiconductor dies using inkjet or electrostatic printing, allowing for precise control and composition without plating, enabling better current capacity and alignment.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If Sn, Ag solder is plated on lead frame, then compact package design is facilitated, but current capacity is limited and connections fail due to electromigration

Engineering Contradiction:

Improvepackage sizeVSAvoidsolder connection reliability

Core Design Contradiction:

Volume of moving objectVSReliability

Solution Approach 1:

The patent changes the solder material composition from Sn, Ag to SAC (Sn, Ag, Cu) solder, which has better current capacity and resistance to electromigration. This parameter change in material composition resolves the reliability issue while maintaining the compact package design benefit

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the traditional plating process with a non-screen printing deposition process for applying SAC solder to the lead frame. This substitution enables the use of SAC solder, which has superior electrical properties, while avoiding the limitations of both plating and screen printing methods

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Quantity of substance

If SAC solder is screen printed, then deposition is achieved, but misalignment and manufacturability issues occur

Engineering Contradiction:

Improvesolder depositionVSAvoidalignment precision

Core Design Contradiction:

Quantity of substanceVSManufacturing precision

Solution Approach 1:

The patent replaces screen printing with a non-screen printing deposition process that uses a deposition head to precisely deposit SAC solder onto the lead frame. This substitution eliminates the misalignment issues inherent in screen printing while maintaining efficient manufacturability through automated deposition

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The non-screen printing process creates a precise copy or replica of the desired solder pattern directly onto the lead frame without requiring physical screens or stencils, thereby achieving high alignment precision while maintaining manufacturing efficiency

Inventive Principle:

Principle #26Copying

3Reliability

If SAC solder is used, then current capacity is improved, but plating applications are not suitable

Engineering Contradiction:

Improvecurrent capacityVSAvoidplating process compatibility

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent replaces the plating process with a non-screen printing deposition process that is compatible with SAC solder. This substitution enables the use of SAC solder's superior current capacity while overcoming the incompatibility with traditional plating methods

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the manufacturing process parameters from plating to non-screen printing deposition, which allows SAC solder to be applied effectively. This parameter change in the deposition method enables SAC solder to be used while maintaining ease of manufacture

Inventive Principle:

Principle #35Parameter changes

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 method enhances the reliability and current capacity of solder connections by using SAC solder in non-screen printing processes, improving manufacturability and alignment, and allowing for the use of unplated copper lead frames, resulting in improved electronic device performance and efficiency.

Implementation Method 1

the non-screen printing process is an inkjet printing process

Methodology Applied

Scientific EffectInkjet printing:

Implementation Method 2

the non-screen printing process is an electrostatic printing process

Methodology Applied

Scientific EffectElectrostatic printing: Electrostatic Deposition

Implementation Method 3

the non-screen printing process deposits the solder as an alloy mixture of melted particles using a heated print head

Methodology Applied

Scientific EffectHeating: Heating

Implementation Method 4

performing a thermal process that reflows the solder

Methodology Applied

Scientific EffectReflow soldering: Heating

Implementation Method 5

the non-screen printing process deposits the solder as particles in a solvent

Methodology Applied

Scientific EffectEvaporation: Evaporation

Data Source

PatentUS20220059439A1Solder printing

Publication Date: 2022.02.24 TEXAS INSTRUMENTS INC

AI summary

A method includes performing a non-screen printing process that deposits solder on a lead frame or on conductive features of a semiconductor die or wafer, or on or in a conductive via of a laminate structure. The method further comprises engaging the semiconductor die to the lead frame, performing a thermal process that reflows the solder, performing a molding process that forms a package structure which encloses the semiconductor die and a portion of the lead frame, and separating a packaged electronic device from a remaining portion of the lead frame.