Prepreg Warpage Reduction via High Tg Resin and Rubber

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Printed wiring boards face challenges with warpage due to temperature changes and inadequate desmear resistance, leading to reliability issues in semiconductor packages, especially when thin and subjected to drilling and laser processing.

Innovation Solution

A prepreg with a glass transition temperature between 150° C. and 220° C., containing a thermosetting resin and a rubber component with a weight average molecular weight of 100,000 or more, is used to reduce warpage and improve desmear resistance by maintaining a high elastic modulus at 260° C. and controlling thermal expansion coefficients.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If the printed wiring board is made thinner to achieve smaller size, then the size reduction is achieved, but warpage occurs in the semiconductor package due to temperature changes

Engineering Contradiction:

Improvesize of printed wiring boardVSAvoidwarpage of semiconductor package

Core Design Contradiction:

Volume of moving objectVSStability of the object's composition

Solution Approach 1:

The patent applies parameter changes by precisely controlling the glass transition temperature (Tg) of the resin composition between 150-220°C and the elastic modulus at 260°C between 3.0-7.0 GPa. This optimization of material parameters enables the thin printed wiring board to maintain dimensional stability and reduce warpage while keeping the board thickness small.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses composite materials by formulating a resin composition containing thermosetting resin (A) combined with specific rubber components (B) having weight average molecular weight of 100,000 or more. This composite resin system provides both the flexibility needed for thin construction and the mechanical stability required to prevent warpage in semiconductor packages.

Inventive Principle:

Principle #40Composite materials

2Ease of manufacture

If drilling and laser processing are performed to create holes for connecting conductor patterns, then connectivity between layers is achieved, but resin smear is generated on inner walls of the holes

Engineering Contradiction:

Improveconnectivity between conductor layersVSAvoidresin smear on hole inner walls

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent applies parameter changes by optimizing the rubber component content (30-100 parts by mass per 100 parts of thermosetting resin) and molecular weight (≥100,000) to control the resin's viscoelastic properties. This results in reduced resin smear generation during drilling and laser processing, improving hole quality without compromising layer connectivity.

Inventive Principle:

Principle #35Parameter changes

3Manufacturing precision

If a large amount of resin smear is removed by the desmear process to improve hole quality, then hole cleanliness is improved, but deformation of holes and pealing of copper foil occur

Engineering Contradiction:

Improvecleanliness of hole inner wallsVSAvoidconduction reliability of printed wiring board

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The patent converts the potential harm of resin smear into a benefit by formulating the resin composition to inherently minimize smear generation. The specific rubber component with high molecular weight acts as a smear suppressant during processing, reducing the need for aggressive desmear etching and thereby preventing hole deformation and copper foil pealing while maintaining conduction reliability.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 solution effectively reduces warpage of semiconductor packages and enhances desmear resistance, ensuring reliable conduction and stability across temperature changes, while minimizing the need for excessive desmear etching.

Implementation Method 1

maintaining a high elastic modulus at 260° C.

Methodology Applied

Scientific EffectElasticity: Elasticity

Implementation Method 2

controlling thermal expansion coefficients

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 3

at least one compound selected from a group consisting of core shell rubber and a polymer component having a weight average molecular weight of 100000 or more

Methodology Applied

Scientific EffectDamping: Damping

Data Source

PatentUS11647583B2Prepreg, metal-clad laminated board, and printed wiring board

Publication Date: 2023.05.09 PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD

AI summary

A prepreg contains a base material containing a reinforcing fiber and a semi-cured product of a resin composition impregnated into the base material containing a reinforcing fiber. The prepreg after cured has a glass transition temperature (Tg) which is higher than or equal to 150° C. and lower than or equal to 220° C. The resin composition contains (A) a thermosetting resin and (B) at least one compound selected from a group consisting of core shell rubber and a polymer component having a weight average molecular weight of 100000 or more. An amount of the (B) component is higher than or equal to 30 parts by mass and lower than or equal to 100 parts by mass with respect to 100 parts by mass of the (A) component.