meas pr cntr rewash
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Contents
LG.Philips Displays
PPD
Eindhoven
TVZ-225-04-EK-D028
Final
2004-05-26
Screen processing
Measurements for Process ControlPrecoating
Contents
1Contents
11. Introduction
12. Utilities
13. HP Spraying
13.1 Water pressure
24. Acid spraying
24.1 Total acid concentration
35. Water spraying
36. Internal screen drying
37. Liquid flow meters
48. Air flow meters
49. Pressure gauges
1. Introduction
This document describes the measurment methods for minimum requirements of process control for rewash.
2. Utilities
Demi water, compressed air and vacuum are controlled by pressure gauges. See chapter 9 for more details.
3. HP Spraying
3.1 Water pressure
Purpose
Monitor the spraying pressure for high pressure water spraying.
Functional specification of measuring equipment and materials
The capacity of the pressure gauge is preferably 25 100% higher than the nominal pressure of the process. Accuracy 5 % of maximum pressure.
Sample preparation
Pressure gauges are placed on the high-pressure pumps and usually also on the front side of the process position.
Functional specification of measuring method
The pressure can be directly read from the pressure gauge.
The demi water is supplied from a small storage tank next to the pressure pumps. Check if the water level in the tank is sufficient.
Corrective measures (OCAP)
When the main de-ionized waterpressure is out of specification, contact the facility department that is responsible for these supplies.
When the waterpressure is out of specification, reduce or increase the pressure with the valve on the pump (see picture).
High pressure pumps
4. Acid spraying
The Acid flow rate is controlled by a liquid flow meter. See chapter 7 for more details.
4.1 Total acid concentration
Purpose
Determine the total acid concentration in the etching position.
Safety precautions
HF/HNO3 is a very aggressive chemical and must be handled with utmost precaution.
For taking samples from process positions and/or acid supply carts use protective clothing like face mask, rubber boots, protective skirt and acid resistant gloves.
Handling of HF/HNO3 acid is only allowed by trained and authorized operators.
Functional specification of measuring equipment and materials
Titration equipment (e.g. Titronic 97/50) 100ml polypropylene beaker
Magnetic stirrer
Spraying bowl with de-ionized water
Pipette 2500 (l
Methyl red solution (1g/l 60% ethanol)
De-ionized water
KOH solution 1 N
Sample preparation
Add approx. 50 ml of de-ionized water in a 100 ml polypropylene beaker.
Take with a pipette exactly 2500 (l of HF/HNO3 solution from the acid cart and add to the de-ionized water.
Functional specification of measuring method
Add 2-3 droplets of Methyl red.
Place the solution on the magnetic stirrer.
Add just as much of the KOH solution to the sample until the color changes from red to yellow.
Read the amount of KOH that is used (V ml).
Total H+ concentration is
Concentration = V / 2.5
[mol H+/l]
V = amount of KOH in ml
Corrective measures (OCAP)
If HF/HNO3 concentration is too high, add appropriate amount of de-ionized water to the acid supply cart.
If HF/HNO3 concentration is too low, drain part of the acid cart and top up with higher concentration acid. Often the chemical preparation department supplies HF/HNO3 with higher concentration than required for the rewash process. Final adjustment of the concentration is done in the supply cart.
5. Water spraying
The demi water flow is controlled with flow meters. See chapter 7 for more details.
6. Internal screen drying
The airflow rate is controlled with a flow meter. See chapter 8 for more details.
7. Liquid flow meters
Purpose
Flow meters indicate the liquid flow of chemicals and de-ionized water in circulation systems or supply to process positions.
Functional specification of measuring equipment and materials
The capacity of the flow meter is preferably 25 100% higher than the nominal flow of the process. Accuracy 5 % of maximum flow.
Sample preparation
The flow meters are placed in the liquid circulation system or in the supply system to the process position.
Functional specification of measuring method
The flow can be directly read from the flow meter.
Corrective measures (OCAP)
Flow too high: Close the control valve or reduce supply pressure.
Flow too low: Open the control valve or increase the supply pressure.
If the required flow cannot be reached, check liquid filters, utilities (de-ionized water pressure, compressed air pressure etc.) and /or function of circulation pumps.
8. Air flow meters
Purpose
Air flow meters indicate the air flow of compressed air to process positions.
Functional specification of measuring equipment and materials
The capacity of the flow meter is preferably 25 100% higher than the nominal flow of the process. Accuracy 5 % of maximum flow.
Sample preparation
The flow meters are placed in the supply system to the process position.
Functional specification of measuring method
The flow can be directly read from the flow meter.
Corrective measures (OCAP)
Flow too high: close the control valve or reduce supply pressure.
Flow too low: Open the control valve or increase the supply pressure.
If the required flow cannot be reached, check air filters and utilities (compressed air pressure) 9. Pressure gauges
Purpose
Pressure gauges are used to indicate the pressure of liquids and compressed.
Functional specification of measuring equipment and materials
The capacity of the pressure gauge is preferably 25 100% higher than the nominal pressure of the process. Accuracy 5 % of maximum pressure.
Sample preparation
Pressure gauges are placed in the supply system of utilities (de-ionized water, compressed air and vacuum), on supply racks for chemicals, de-ionized water and compressed air to process positions.
Functional specification of measuring method
The pressure can be directly read from the pressure gauge.
Corrective measures (OCAP)
When the main de-ionized water, compressed air and vacuum supply is out of specification, contact the facility department that is responsible for these supplies.
When the pressure de-ionized water or air supply to process positions is out of specification, reduce or increase the pressure with the accompanying reducing valve.
When the pressure difference over a liquid filter is too high, the filter must be replaced.
AMENDMENT RECORD
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Valves to control pressure
Pressure gauges
LG.Philips Displays
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