Parallel Roots Vacuum Pumping for Load-Lock Pressure Control
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Solution Overview
Problem
Current pumping systems for loading and unloading locks in manufacturing processes, particularly for large substrates like flat display screens and photovoltaic substrates, face challenges in quickly and efficiently lowering and raising pressure from atmospheric to low pressure due to the antagonistic characteristics of vacuum pumps, which result in prolonged pumping times and inefficiencies.
Innovation Solution
A pumping system comprising a first primary pumping group with high inertia and a second primary pumping group with low inertia, connected in parallel, where the first group has a maximum pumping speed greater than or equal to 2000 m³/h and the second group less than 2000 m³/h, allowing for distinct pumping characteristics that compensate for each other's weaknesses to achieve rapid pressure changes at controlled costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single vacuum pump is used to lower pressure in the airlock chamber, then the pump must have high pumping capacity to achieve the desired low pressure within the allotted time, but this results in high inertia that causes temporary slowing down at the start of pumping and reduces efficiency at high and medium pressure
Solution Approach 1:
The single vacuum pump is segmented into two separate vacuum pumps with different characteristics. The first vacuum pump has high pumping capacity for achieving low pressure, while the second vacuum pump has low inertia for efficient operation at high and medium pressure. This segmentation allows each pump to specialize in different pressure ranges, resolving the contradiction between pumping speed and pumping time.
Solution Approach 2:
The system changes the parameter of pumping capacity by using two pumps with different pumping capacities instead of one pump. The first pump operates at high pumping capacity for the final low pressure stage, while the second pump operates at lower pumping capacity but with low inertia for the initial high and medium pressure stages. This parameter change allows optimization at different pressure points.
2Manufacturing precision
If a large-sized vacuum pump with high pumping capacity is used, then the desired low pressure can be achieved, but the pump has high inertia making it relatively inefficient at the start of pumping at high and medium pressure
Solution Approach 1:
The vacuum pumping function is segmented between two pumps: one optimized for high pressure efficiency (low inertia) and another optimized for low pressure achievement (high pumping capacity). This segmentation allows each pump to operate in its optimal efficiency range, resolving the contradiction between pressure control precision and operational ease.
Solution Approach 2:
The second vacuum pump with low inertia acts as an intermediary that handles the initial high and medium pressure stages, preparing the system for the first vacuum pump to achieve the final low pressure. This intermediary pump resolves the contradiction by taking on the intermediate pressure control task where high inertia pumps would be inefficient.
3Volume of moving object
If the airlock chamber volume is increased to accommodate large substrates like flat display screens, then the chamber can hold larger substrates, but the pumping time increases because the larger volume requires more time to evacuate
Solution Approach 1:
The pumping task for the large-volume airlock chamber is segmented into two phases handled by two different pumps. The low-inertia pump handles the initial high-flow phase for rapid pressure reduction, while the high-capacity pump handles the final low-pressure phase. This segmentation allows the large chamber to be evacuated efficiently without excessive pumping time.
Solution Approach 2:
The system changes the pumping parameter by using two pumps with different pumping speeds and inertia characteristics. This allows the large-volume chamber to be evacuated by matching pump characteristics to different stages of the evacuation process, reducing total pumping time despite the large volume.
4Productivity
If the pumping speed is increased to reduce pumping time, then the pressure can be lowered faster, but the pump inertia causes temporary slowing down at the start of pumping due to overload absorption
Solution Approach 1:
The pumping function is segmented into two pumps: one with high pumping speed that experiences rotation slowing due to inertia, and another with low inertia that maintains rotation speed. The low-inertia pump handles the initial high-speed phase without significant slowing, while the high-speed pump handles the final phase, resolving the contradiction between overall pumping speed and rotation speed stability.
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 enables the system to efficiently manage pressure changes by allowing low-inertia pumps to quickly re-accelerate and high-inertia pumps to achieve high volumetric flow rates at low pressure, meeting time constraints while minimizing costs.
Implementation Method 1
a pumping system intended to be connected to a chamber (2) of an airlock for loading and unloading a substrate (5), comprising at least a first primary pumping group (9a) having a first maximum pumping speed and a second primary pumping group (10a) having a second maximum pumping speed
Data Source
Figure 1~2
Figure 3~4
AI summary
The invention concerns a pumping system intended to be connected to a load-lock chamber (2) for loading and unloading a substrate (5), comprising at least a first primary pumping unit (9a, 9b) having a first maximum pumping speed (S1) and a second primary pumping unit (10a, 10b) having a second maximum pumping speed (S2), each primary pumping unit (9a, 9b, 10a, 10b) comprising a single-stage Roots vacuum pump (15) and a primary vacuum pump (13), the single-stage Roots vacuum pump (15) being mounted in series with and upstream from the primary vacuum pump (13) in the direction of flow of the gases to be pumped, said first and second primary pumping units (9a, 9b, 10a, 10b) being mounted in parallel and configured to simultaneously pump the load-lock chamber (2) for loading and unloading the substrate, characterised in that said first primary pumping unit (9a, 9b) has different pumping characteristics to said second primary pumping unit (10a, 10b), the difference between the first and second maximum pumping speeds of said first and second primary pumping units (9a, 9b, 10a, 10b) being greater than 500 m3/h. The invention also concerns a method for lowering the pressure in a load-lock chamber (2).