Electronic Element Mounting Substrate Thermal Stress Relief

Solution Overview

Problem

The existing electronic element mounting substrates face issues with thermal stress and cracking due to differences in thermal expansion rates between the insulating wiring substrate and the metal plate, leading to potential peeling-off and breakage, especially when force is applied during component mounting or wire bonding.

Innovation Solution

The substrate design includes a first wiring substrate with a frame forming a through-hole, a metal plate covering the hole's opening, and a second wiring substrate in the peripheral region of the metal plate, which is electrically connected to the external circuit connection electrode, reducing the bonding area and supporting the wiring substrate to alleviate stress.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the metal plate is disposed on the lower surface of the first wiring substrate, then thermal stress occurs due to difference in thermal expansion rates, but reducing the bonding area between the metal plate and the first wiring substrate can reduce thermal stress concentration

Engineering Contradiction:

Improvebonding reliabilityVSAvoidthermal stress

Core Design Contradiction:

ReliabilityVSStress or pressure

Solution Approach 1:

The patent applies local quality by creating a recessed portion in the metal plate at the location where the electronic element is mounted. This local modification allows the metal plate to have different properties in different regions: the recessed area provides thermal expansion accommodation to reduce stress, while the surrounding bonding areas maintain sufficient bonding strength for reliable electrical connection. This resolves the contradiction by making the structure non-uniform where needed rather than reducing the entire bonding area.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The recessed portion in the metal plate acts as a pre-designed stress relief structure that accommodates thermal expansion differences before they cause damage. By anticipating the thermal stress issue and building in a cushioning feature (the recessed area) during manufacturing, the design prevents bonding member failure without compromising overall bonding reliability.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

2Stress or pressure

If the peripheral portion of the metal plate is located inside the peripheral portion of the first wiring substrate, then thermal stress is reduced, but bending stress occurs in the first wiring substrate when force is applied from the upper surface

Engineering Contradiction:

Improvethermal stressVSAvoidsubstrate strength

Core Design Contradiction:

Stress or pressureVSStrength

Solution Approach 1:

The patent applies local quality by creating a recessed portion in the metal plate at the location where the electronic element is mounted. This local modification allows the metal plate to have different properties in different regions: the recessed area provides thermal expansion accommodation to reduce stress, while the surrounding bonding areas maintain sufficient bonding strength for reliable electrical connection. This resolves the contradiction by making the structure non-uniform where needed rather than reducing the entire bonding area.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The recessed portion in the metal plate acts as a pre-designed stress relief structure that accommodates thermal expansion differences before they cause damage. By anticipating the thermal stress issue and building in a cushioning feature (the recessed area) during manufacturing, the design prevents bonding member failure without compromising overall bonding reliability.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Length of moving object

If the thickness of the first wiring substrate is reduced, then the entire thickness of the electronic element mounting substrate decreases, but the first wiring substrate becomes more susceptible to cracking and breakage under applied force

Engineering Contradiction:

Improvesubstrate thicknessVSAvoidsubstrate strength

Core Design Contradiction:

Length of moving objectVSStrength

Solution Approach 1:

The patent applies local quality by creating a recessed portion in the metal plate at the location where the electronic element is mounted. This local modification allows the metal plate to have different properties in different regions: the recessed area provides thermal expansion accommodation to reduce stress, while the surrounding bonding areas maintain sufficient bonding strength for reliable electrical connection. This resolves the contradiction by making the structure non-uniform where needed rather than reducing the entire bonding area.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The recessed portion in the metal plate acts as a pre-designed stress relief structure that accommodates thermal expansion differences before they cause damage. By anticipating the thermal stress issue and building in a cushioning feature (the recessed area) during manufacturing, the design prevents bonding member failure without compromising overall bonding reliability.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

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 effectively reduces thermal stress and bending stress, preventing cracking and breakage of the wiring substrate while allowing for a thinner substrate design and improved air tightness, enhancing the reliability and durability of the electronic device.

Implementation Method 1

there is a difference in thermal expansion rates between the first wiring substrate formed of an insulating layer and the metal plate, and the thermal expansion rate of the metal plate is greater than that of the first wiring substrate

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS9806005B2Electronic element mounting substrate and electronic device

Publication Date: 2017.10.31 KYOCERA CORP

AI summary

An electronic element mounting substrate includes: a first wiring substrate configured to be a frame defining an interior portion as a first through-hole, the first wiring substrate including a lower surface including an external circuit connection electrode; a metal plate disposed on the lower surface of the first wiring substrate so as to cover an opening of the first through-hole, an outer edge thereof being located between an outer edge of the first wiring substrate and an inner edge of the first wiring substrate, an electronic element mounting portion being disposed in a region of an upper surface of the metal plate which region is surrounded by the first wiring substrate; and a second wiring substrate which is disposed in a peripheral region of the metal plate on the lower surface of the first wiring substrate and is electrically connected to the external circuit connection electrode.