Semiconductor Packaging Using Multiple Reflow Processes

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Solution Overview

Problem

The increasing density of metal pins and reduced pitches in semiconductor packaging lead to signal coupling, noise, and reduced reliability, while complex wire bond arrangements in System in Package (SIP) assemblies are prone to breaks and shorts, necessitating a more reliable connection method.

Innovation Solution

A method involving flip-chip technology with multiple reflow processes to secure solder balls and a center line material layer, ensuring the integrity of semiconductor devices by electrically connecting dies and substrates, and forming conductive elements on the substrate to prevent deformation and ensure reliable connections.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If wire bond structure is used for SIP assembly, then connection between ICs can be established, but the large number of wire bonds are prone to breaks and shorts

Engineering Contradiction:

Improveconnection reliabilityVSAvoidwire bond arrangement complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent extracts the wire bonding process entirely and replaces it with direct die-to-substrate mounting using bump joints. This eliminates the intermediate wire bond connections that were prone to breaks and shorts, directly addressing the reliability issue while simplifying the overall structure.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent replaces the mechanical wire bonding system with a direct mechanical and electrical connection system using bump joints. This substitution eliminates the complex wire manipulation process and provides more robust connections that are less susceptible to mechanical failure.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Manufacturing precision

If lead frame technology is used, then package structure can be formed, but it is not suitable for high density metal pins

Engineering Contradiction:

Improvemetal pin densityVSAvoidpackage technology adaptability

Core Design Contradiction:

Manufacturing precisionVSAdaptability or versatility

Solution Approach 1:

The patent changes the fundamental connection parameter from wire bonds to direct bump joint connections, enabling high-density metal pin arrangements. This parameter change allows for closer spacing of connection points while maintaining manufacturing feasibility and connection reliability.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If solder ball is used for connection, then electrical connection can be established, but solder ball deformation may occur during packaging process

Engineering Contradiction:

Improveelectrical connection reliabilityVSAvoidsolder ball shape stability

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent applies underfill material before final packaging to cushion and support the solder balls or bump joints. This preventive measure stabilizes the solder ball shape during subsequent packaging processes, preventing deformation while maintaining reliable electrical connections.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The patent introduces underfill material as an intermediary substance between the substrate and die. This mediator provides mechanical support and stabilization to the solder balls, preventing their deformation during the packaging process while allowing electrical connections to remain intact.

Inventive Principle:

Principle #24Intermediary (Mediator)

4Volume of moving object

If WLP is used to package wafer, then packaging volume can be reduced, but signal coupling and noise increase due to reduced pitches

Engineering Contradiction:

Improvepackage volumeVSAvoidsignal coupling and noise

Core Design Contradiction:

Volume of moving objectVSObject-generated harmful factors

Solution Approach 1:

The patent applies underfill material locally around the die and solder ball connections to provide targeted mechanical support. This localized intervention stabilizes the connection structures in critical areas without affecting the overall compact WLP design, thereby preventing solder ball deformation while maintaining signal integrity.

Inventive Principle:

Principle #3Local quality

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 approach enhances the yield and reliability of the packaging process by preventing deformation and ensuring robust electrical connections, addressing the limitations of traditional wire bonding and wafer level packaging technologies.

Implementation Method 1

performing more than once reflow processes to fix the plurality of conductive elements on the plurality of second connecting points

Methodology Applied

Scientific EffectReflow process: Heating

Implementation Method 2

more than once reflow process is performed to prevent the deformation of solder ball

Methodology Applied

Scientific EffectMelting and solidification: Melting

Data Source

PatentUS8278145B2Method for packaging semiconductor device

Publication Date: 2012.10.02 GLOBAL UNICHIP CORPORATION

AI summary

The present invention provides a method for packaging semiconductor device which is using more than once reflow processes to heat the solder ball to prevent the deformation of solder ball, so that the yield of the manufacturing process can be increased and the reliability of the semiconductor device can be increased.