Linear Scale Thermal Expansion Correction via Laser Interferometry

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Solution Overview

Problem

In bonding devices, temperature-induced thermal expansion of linear scales leads to errors in movement precision, reducing the accuracy of electronic component mounting due to non-uniform expansion and varying thermal expansion amounts across different sections.

Innovation Solution

A device and method that utilize a rail-guided first and second movable body with a scale having graduations, detection units, and a control unit to maintain a predetermined interval between the detection units, allowing for precise movement correction by calculating position correction coefficients based on the ratio of the interval to the distance between graduations, and using image acquisition and distance detection for accurate positioning.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a linear scale is used for detection of the amount of movement of a base having a bonding head, then the movement amount can be detected, but when the temperature of the bonding device rises, the linear scale expands and an error is generated in the amount of movement of the base

Engineering Contradiction:

Improvemovement detection precisionVSAvoidmeasurement accuracy under temperature variation

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent introduces a laser distance detector as an intermediary measurement device that measures the actual position of the base independently of the linear scale. This intermediary measurement system compensates for the thermal expansion errors of the linear scale by providing reference measurements that are not affected by the scale's thermal deformation.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent implements a feedback mechanism where the laser distance detector continuously monitors the base position and feeds this information back to the control unit. The control unit compares the laser measurement with the linear scale reading and applies correction based on the detected discrepancy, thereby compensating for thermal expansion effects in real-time.

Inventive Principle:

Principle #23Feedback

2Measurement precision

If the temperature rise of the linear scale is not uniform, then the thermal expansion amount of the linear scale often differs depending on sections, but this causes reduction in the position detection precision of the bonding head

Engineering Contradiction:

Improveposition detection precisionVSAvoiduniformity of thermal expansion

Core Design Contradiction:

Measurement precisionVSStability of the object's composition

Solution Approach 1:

The patent divides the measurement system into multiple independent detection points: the linear scale provides one measurement and the laser distance detector provides another independent measurement. This segmentation allows the system to detect and compensate for non-uniform thermal expansion by comparing measurements from different locations and applying appropriate corrections.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent replaces part of the mechanical measurement system (linear scale) with an optical measurement system (laser distance detector). The optical system is less susceptible to thermal expansion effects, and by combining both measurement systems, the patent compensates for the non-uniform thermal expansion of the mechanical scale.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 approach enhances the movement precision of movable bodies, improving the positioning accuracy of bonding tools and reducing errors in electronic component mounting, thereby maintaining high precision despite thermal expansion.

Implementation Method 1

a laser distance detector that detects a distance between the first base and the second base

Methodology Applied

Scientific EffectLaser: Laser

Implementation Method 2

when the temperature of the bonding device rises, the linear scale expands and an error is generated in the amount of movement of the base

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS11469125B2Device and method for linearly moving first and second moving bodies relative to target object

Publication Date: 2022.10.11 YAMAHA ROBOTICS CO LTD

AI summary

A device for linearly moving bases with respect to an object, includes first and second bases, a linear scale provided with graduations at pitches in the moving direction, first and second encoder heads attached to the first and second bases, and a control unit. The control unit maintains an interval between the first and second encoder heads to be constant, and moves the first and second bases while sequentially detects a first and second graduation numbers, and calculates a distance on the scale between the first and second encoder heads by multiplying a difference between the first and second graduation numbers by the pitch, and calculates a position correction coefficient of the scale as a ratio of the interval with respect to the calculated distance, and controls the movement amount of the first movable body and the second movable body based on the position correction coefficient.