Mounting Board Silver-Copper-Tin Structure

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Solution Overview

Problem

Conventional mounting boards face issues with connection reliability due to galvanic corrosion and unstable conductivity when using tin-plated electrode sections, and they struggle to accurately mount small electronic components due to viscosity issues with conductive adhesives.

Innovation Solution

A mounting board design featuring an insulative base with silver-containing first conductive elements, silver-plated copper powder second conductive elements, and tin-containing solder pieces, where no silver is present at their interfaces, along with a method of producing this board that ensures stable electrical connections and precise alignment of small components.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If conductive adhesive is used to mount electronic components on membrane circuit board, then low-temperature mounting is achieved, but connection reliability deteriorates due to galvanic corrosion and unstable conductivity

Engineering Contradiction:

Improvesoldering temperatureVSAvoidconnection reliability

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

The patent introduces a three-layer conductive structure as an intermediary system: silver paste circuit layer, copper powder layer, and tin-plated electrode sections. This multi-layer intermediary structure prevents direct contact between incompatible materials (silver and tin), eliminating galvanic corrosion while maintaining low-temperature mounting capability.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention uses composite conductive materials comprising multiple layers with different properties: silver paste for conductivity, copper powder for structural stability, and tin plating for electrode compatibility. This composite structure resolves the contradiction between low-temperature mounting and connection reliability.

Inventive Principle:

Principle #40Composite materials

2Manufacturing precision

If conductive adhesive pieces are placed close together for small electronic components, then mounting precision is improved, but viscosity loss causes adhesive pieces to flow together

Engineering Contradiction:

Improvemounting precisionVSAvoidadhesive viscosity stability

Core Design Contradiction:

Manufacturing precisionVSStability of the object's composition

Solution Approach 1:

The patent replaces the adhesive-based mechanical bonding system with a soldering-based metallurgical bonding system. Solder pieces maintain their shape and position without viscosity loss, enabling precise placement of small electronic components while eliminating the flow problem inherent in adhesive-based systems.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If silver paste is used for conductive elements, then conductivity is improved, but galvanic corrosion occurs at interfaces with tin-plated electrodes

Engineering Contradiction:

ImproveconductivityVSAvoidgalvanic corrosion

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent segments the conductive path into three distinct layers: silver paste circuit layer, copper powder layer, and tin-plated electrode sections. This segmentation prevents direct contact between silver and tin, eliminating galvanic corrosion while maintaining conductivity through the copper intermediary layer.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The copper powder layer serves as an intermediary between the silver paste circuit and tin-plated electrodes, preventing direct galvanic interaction while maintaining electrical conductivity. This intermediary layer resolves the contradiction between conductivity and corrosion resistance.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 configuration prevents galvanic corrosion, enhances connection reliability, and allows for the precise mounting of small electronic components by maintaining solder piece viscosity and reducing the distance between them, thereby improving yield and stability.

Implementation Method 1

The silver component in the conductive adhesive pieces 260 is incompatible with the tin component and they may cause galvanic corrosion

Methodology Applied

Scientific EffectGalvanic corrosion:

Implementation Method 2

the conductive adhesive pieces 260a may be deformed and extended during mounting of the electronic component 240. In a subsequent heating process, the conductive adhesive pieces 260a may lose viscosity and then flow out of the applied place

Methodology Applied

Scientific EffectViscosity:

Data Source

PatentEP2234466B1Mounting board and method of producing the same

Publication Date: 2019.04.10 FUJIKURA LTD

Figure 1
Figure 2A~2D
Figure 3A~3C

AI summary

A mounting board of the invention includes: an insulative base; a plurality of first conductive elements provided on the insulative base and having lands; a plurality of second conductive elements disposed on the lands; a plurality of solder pieces each disposed on each of the second conductive elements; and an electronic component which includes electrode sections each contacting each of the solder pieces, wherein the first conductive elements are made from a first element that contains at least silver; the second conductive elements are made from a second element that contains at least copper; and the solder pieces are made from a third element that contains at least tin.