Functional Backplane Pad Structure for Brittle Solder Joint Control

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Solution Overview

Problem

Existing soldering processes for electronic components on copper connection pads in SMT result in the formation of brittle intermetallic compounds, leading to embrittlement and poor reliability due to rapid diffusion and excessive thickness of intermetallic compounds at the solder joint, which can cause copper deficiency and damage during maintenance.

Innovation Solution

The use of a wiring board with multiple protective layers, including a first reference protective layer capable of forming an intermetallic compound with solder, to control the diffusion of solder and prevent copper deficiency, thereby improving maintainability and reliability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a copper connection pad is used for soldering electronic components, then good electrical conductivity is achieved, but rapid diffusion of solder to the copper pad occurs causing excessive intermetallic compound thickness and embrittlement

Engineering Contradiction:

Improvesolder joint reliabilityVSAvoidintermetallic compound thickness

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The connection pad structure is segmented into multiple distinct layers: a copper-based main material layer, an intermediate layer, and a protective layer. This segmentation prevents direct contact between solder and copper, controlling diffusion by creating staged barriers that manage intermetallic compound formation at each interface separately.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

An intermediate layer is introduced as a mediator between the copper-based main material layer and the protective layer. This intermediate layer acts as a controlled diffusion barrier, regulating the interaction between solder and copper to prevent excessive intermetallic compound formation while maintaining reliable electrical and mechanical connections.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Strength

If solder diffusion is allowed to proceed rapidly for strong bonding, then bonding strength is achieved, but intermetallic compounds become excessively thick and brittle causing joint failure

Engineering Contradiction:

Improvebonding strengthVSAvoidjoint durability

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The diffusion parameters are controlled by changing the material composition and thickness of the protective layer and intermediate layer. By adjusting these parameters, the diffusion rate is optimized to achieve sufficient bonding strength while preventing excessive intermetallic compound growth that would cause brittleness and joint failure.

Inventive Principle:

Principle #35Parameter changes

3Stability of the object's composition

If multiple protective layers are added to control solder diffusion, then intermetallic compound thickness is reduced, but device complexity increases

Engineering Contradiction:

Improveintermetallic compound thicknessVSAvoidconnection pad structure complexity

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The connection pad uses a composite multi-layer structure where each layer has specific material properties optimized for its function. The copper-based main material layer provides conductivity, the intermediate layer controls diffusion, and the protective layer prevents excessive intermetallic compound formation. This composite approach achieves precise control over intermetallic thickness while maintaining manufacturing feasibility.

Inventive Principle:

Principle #40Composite materials

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 slows down the solder diffusion, reduces intermetallic compound thickness, and enhances the mechanical strength of the solder joint, improving maintainability and reliability by preventing copper deficiency and embrittlement.

Implementation Method 1

at least a material of the first reference protective layer is capable of forming a first intermetallic compound with a first solder

Methodology Applied

Scientific EffectDiffusion: Diffusion

Implementation Method 2

the first solder forms the first intermetallic compound with at least the first reference protective layer included in the first electrical connection layer

Methodology Applied

Scientific EffectIntermetallic compound formation: Chemical Bonding

Data Source

PatentUS12581596B2Wiring board, functional backplane and method for manufacturing the same

Publication Date: 2026.03.17 BOE TECHNOLOGY GROUP CO LTD

AI summary

A wiring board includes a base substrate and first connection pads disposed on the base substrate. The first connection pads each include electrical connection layer(s); each electrical connection layer includes a main material layer and protective layer(s) disposed on a side of the main material layer away from the base substrate; the protective layer(s) include a first reference protective layer, which is a protective layer farthest away from the base substrate in the protective layer(s); and a material of the main material layer includes copper. The electrical connection layer(s) include a first electrical connection layer, which is an electrical connection layer farthest away from the base substrate in the electrical connection layer(s); and in protective layer(s) in the first electrical connection layer, at least a material of the first reference protective layer is capable of forming a first intermetallic compound with a first solder.