Sensor Head Lubricant Layer for Crystal Oscillator Phase Shift
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Solution Overview
Problem
The existing sensor heads for crystal oscillator type film thickness monitors face issues with phase shifts due to stepping motor misalignment and increasing magnetizing current, leading to inaccurate film thickness measurements, primarily caused by the roughening of gold electrodes during rotation.
Innovation Solution
Incorporating a lubricant supply means with a solid lubricant, such as fluororesin or graphite, between the first and second electrodes to reduce friction and prevent surface roughening, along with an insulating body to detect phase alignment, ensuring accurate electrical contact and maintaining the stepping motor's alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gold electrodes are used for electrical contact between first and second electrodes, then electrical conductivity and corrosion resistance are improved, but surface roughening occurs during rotation causing phase shifts and increased magnetizing current
Solution Approach 1:
A lubricant layer is introduced as an intermediary substance between the gold first electrode and the gold second electrode. This lubricant layer prevents direct metal-to-metal contact, thereby preventing surface roughening while maintaining electrical conductivity. The lubricant acts as a mediator that resolves the contradiction between maintaining reliable electrical contact and preventing phase shifts caused by surface degradation.
2Productivity
If the holder is rotated multiple times to monitor film thickness, then measurement capability is improved, but magnetizing current increases due to accumulated friction heat
Solution Approach 1:
The lubricant layer serves as a mediator that reduces friction between the electrodes during repeated holder rotation. By preventing direct metal-to-metal contact, the lubricant minimizes friction heat generation, thereby reducing the magnetizing current required to drive the stepping motor over extended operation periods while maintaining continuous film thickness monitoring capability.
Solution Approach 2:
The introduction of lubricant changes the physical parameters of the contact interface, specifically reducing the coefficient of friction and heat generation. This parameter change allows the system to operate continuously for multiple measurement cycles without the magnetizing current increasing significantly, thus resolving the contradiction between productivity and energy consumption.
3Ease of operation
If stepping motor drives holder rotation to align crystal oscillators, then positioning capability is improved, but phase shift occurs due to increased sliding resistance
Solution Approach 1:
The lubricant layer is introduced as an intermediary that reduces sliding resistance between the first and second electrodes during holder rotation. By minimizing friction, the lubricant ensures that the stepping motor maintains accurate positioning control without inducing phase shifts, thereby resolving the contradiction between ease of operation and measurement precision.
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 solution prevents phase shifts and reduces magnetizing current, allowing for consistent and accurate film thickness monitoring by minimizing sliding resistance and maintaining electrode contact integrity.
Implementation Method 1
a lubricant supply means is disposed for supplying, before the first electrode comes into contact with the second electrode, a surface of at least one of the first electrode and the second electrode with a solid lubricant
Data Source
AI summary
A sensor head has: a sensor head main body which has disposed therein the stepping motor; a holder which has disposed on an upper surface thereof a plurality of crystal oscillators and which is driven for rotation by the stepping motor; and a mask body which is mounted on the sensor head main body so as to cover an upper surface of the holder and which has opened therein a film-forming window faced by one of the crystal oscillators. The sensor head also has: a first electrode fixed to that portion of the sensor head main body which is located right under the film-forming window; and second electrodes which are in electrical conduction with each of the crystal oscillators and which are disposed to protrude under a lower surface of the holder.