Laser Bonding Temperature Feedback for Stable Solder Joints

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Solution Overview

Problem

Existing bonding technologies using laser irradiation face challenges in achieving stable bonds due to variations in thermal contact resistance and potential damage to heat-sensitive components from excessive temperature rises.

Innovation Solution

A bonding method that involves disposing a bonding material on a first component, a second component on the bonding material, and using a temperature measurement unit to control the output of a laser beam based on measured temperatures of both components, ensuring that the second component reaches a first threshold temperature and the first component reaches a second threshold temperature before terminating the laser beam.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If the irradiation output of the laser beam is increased to heat the wire sufficiently, then the bonding temperature is achieved, but the temperature of the material rises excessively causing damage to heat sensitive components

Engineering Contradiction:

Improvebonding temperatureVSAvoiddamage to heat sensitive components

Core Design Contradiction:

TemperatureVSObject-affected harmful factors

Solution Approach 1:

The patent employs a feedback control mechanism where an infrared thermal detector continuously monitors the temperature of the wire being bonded. The detected temperature is fed back to control the laser beam irradiation output, automatically adjusting the heating power to maintain the wire temperature at the preset bonding temperature without excessive rise that would damage surrounding heat-sensitive components

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent replaces manual or open-loop mechanical heating control with an automated optical detection and control system. The infrared thermal detector optically measures the wire temperature without contact, and this measurement automatically controls the laser output, substituting mechanical trial-and-error heating with precision optical feedback control

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Temperature

If the irradiation output of the laser beam is increased to ensure sufficient heating, then the bonding temperature is achieved, but spatters are scattered to the surroundings causing damage or shorts

Engineering Contradiction:

Improvebonding temperatureVSAvoidspatters

Core Design Contradiction:

TemperatureVSObject-generated harmful factors

Solution Approach 1:

The feedback control system monitors wire temperature in real-time and adjusts laser output accordingly, preventing sudden and local temperature rises that would cause metal melting and spatter generation. By maintaining controlled heating rates, the system achieves bonding temperature without excessive energy input that would create harmful spatters

Inventive Principle:

Principle #23Feedback

3Temperature

If thermal contact resistance varies between the wire surface and solder bonding surface, then heat conduction varies, but this causes variations in soldering quality

Engineering Contradiction:

Improvesoldering temperatureVSAvoidsoldering quality

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

The infrared thermal detector provides real-time feedback on the actual wire temperature, allowing the control system to compensate for variations in thermal contact resistance. When contact resistance causes insufficient heat transfer, the system automatically increases laser output to maintain the required bonding temperature, ensuring consistent soldering quality despite interface resistance variations

Inventive Principle:

Principle #23Feedback

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 method enables the achievement of stable bonds while preventing damage to peripheral components with low heat resistance and avoiding excessive energy input, thereby ensuring reliable bonding processes.

Implementation Method 1

the second component being irradiated with a laser beam

Methodology Applied

Scientific EffectLaser heating: Laser

Implementation Method 2

irradiation of a laser beam heats wire

Methodology Applied

Scientific EffectIrradiation heating: Heating

Implementation Method 3

an infrared thermal detector detects the temperature of the wire heated by the irradiation of the laser beam

Methodology Applied

Scientific EffectInfrared thermal detection: Infrared Radiation

Implementation Method 4

a thermal contact resistance between a surface of the wire that is irradiated with the laser beam and a bonding surface of solder disposed to face the irradiated surface causes heat conduction between these surfaces to vary

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentUS20250178123A1Bonding method

Publication Date: 2025.06.05 MITSUBISHI ELECTRIC CORP

AI summary

A highly stable bond is obtained with variations in the bond being suppressed. A bonding method includes: disposing a temperature measurement unit such that temperatures of a first component and a second component can be measured; measuring the temperatures of the first component and the second component using the temperature measurement unit, with the second component being irradiated with a laser beam; reducing output of the laser beam when the measured temperature of the second component is higher than or equal to a first threshold value; and terminating the output of the laser beam when the measured temperature of the first component is higher than or equal to a second threshold value after the temperature of the second component is higher than or equal to the first threshold value.