meas pr cntr rewash

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.


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.


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


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.


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.


The flow can be directly read from the flow meter.


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.


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.


The flow can be directly read from the flow meter.


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.


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.


The pressure can be directly read from the pressure gauge.


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

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