semi合集-English.pdf - 第417页

SEMI E56-1104 © SEMI 1996, 2004 6 Figure 3 Mass Flow Controller Test Fixture 11 Calibration Standardization 11.1 All m easurement devices m ust have valid calibration certificates. 12 Conditioning 12.1 Place the MFC to b…

SEMI E56-1104 © SEMI 1996, 2004 5

device must be better than or equal to ± 1/2 sccm). The

traceability of all the pertinent measuring instruments

and devices should be realistically established and

quantified.

7.1.1 In addition, take care when using test instruments

with a specified accuracy expressed in percent of full

scale. For example, if an instrument with a specified

accuracy of ± 0.1% of full scale is used to measure the

output of the DUT, but this output signal falls only

within the lower third of the scale of the instrument, the

effective accuracy over the range of the instrument

being used may be ± 0.3%, which is unsuitable for

many applications.

7.2 Use special precautions to ensure that minimum

effects result from pneumatic noise in flow lines.

Monitor pressure both upstream and downstream of the

MFC to ensure that pneumatic noise is minimized.

7.3 The DUT should be installed so that the inlet flow

can be fully developed, pulsation-free, for the specific

conditions. This can be achieved by plumbing a

straight length of tubing 40–50 diameters long upstream

and another straight length 5 diameters long

downstream of the DUT. (For additional information

about inlet effects, refer to ASME MFC-10M.)

7.4 At regular calibration intervals, verify electrical

signals directly at the MFC connector to ensure that

there are no unacceptable line losses in the cables.

8 Apparatus

8.1 heat exchanger

8.2 flow standard

8.3 pressure transducer

8.4 back pressure regulator

8.5 temperature probe

8.6 digital voltmeter

8.7 setpoint generator

8.8 power supply

9 Technical Precautions

9.1 Many analog-to-digital converter cards do not

differentiate between measurements of less than zero

and zero. It may be necessary to use a digital voltmeter

to record measurements below zero volts. Some MFCs

do not differentiate between measurements of less than

zero and zero. This may bias the results.

9.2 The manufacturer’s specifications and instructions

for installation and operation must be applied during all

testing.

9.3 All electrical measurements should be read on

devices with at least 4.5 digits of resolution. These

devices must have valid calibration certifications.

9.4 The mounting position of the device must be in

accordance with the manufacturer's specifications. No

external mechanical constraints beyond the

manufacturer’s recommended mounting position shall

be permitted.

10 Preparation of Apparatus

10.1 Figure 3 is a representation of a recommended

generic testing apparatus. The flow standard is shown

downstream of the device under test (DUT). It may be

placed upstream of the DUT if the flow standard cannot

be exposed to a low pressure environment. In this case,

the user should be aware of possible back pressure

effects on the flow standard.

10.2 The flow standard can be of any type, including

laminar flow elements, volumetric standards, rate of

rise, or mass flow meters.

SEMI E56-1104 © SEMI 1996, 2004 6

Figure 3

Mass Flow Controller Test Fixture

11 Calibration Standardization

11.1 All measurement devices must have valid

calibration certificates.

12 Conditioning

12.1 Place the MFC to be tested in the testing

environment. Apply power to the MFC for the 24

hours prior to initiating warm-up as defined by the

manufacturer. The valve should be in its “off” position

(closed for a NC valve, open for a NO valve).

12.2 Following the conditioning period, install and

warm up the device according to manufacturer's

specifications.

12.3 Purge the MFC with clean, dry nitrogen or argon

following the warm up period.

12.4 Allow the test gas to flow through the DUT for a

minimum of 10 minutes at 100% of flow.

12.5 Apply a 100% full-scale setpoint to the DUT and

wait for the flow to stabilize for 10 seconds. Apply the

lower setpoint limit to the DUT and wait for the flow to

stabilize for 10 seconds. Repeat this cycle two more

times. This process exercises the device before

initiating the test.

12.6 Test Conditions

12.6.1 The reference operating conditions shall be as

follows if the downstream pressure is atmospheric

pressure:

Ambient temperature 23 ± 2°C

Gas temperature Same as actual ambient

Ambient pressure 101.32 kPa. (+ 4.7 or – 15.3 kPa)

Gas pressure P

, Inlet 274 ± 34 kPa

Gas pressure P

, Outlet 101.32 kPa. (+ 4.7 kPa or – 15.3

kPa)

Relative humidity 40% ± 10%, noncondensing

Magnetic field  50 µT

Electromagnetic field < 100 µ V/m

Vibration < 0.5 m/s

Shock  3 g

12.6.2 The reference operating conditions shall be as

follows if the downstream pressure is at vacuum:

Ambient temperature 23 ± 2°C

Gas temperature Same as actual ambient

Ambient pressure 101.32 kPa. (+ 4.7 or – 15.3 kPa)

Gas pressure P1, Inlet 172 ± 34 kPa

Gas pressure P3, Outlet < 0.13 kPa

Relative humidity 40% ± 10%, noncondensing

Magnetic field  50 µT

Electromagnetic field < 100 µ V/m

Vibration < 0.5 m/s

Shock  3 g

12.7 Power Supply Conditions

12.7.1 The reference power supply conditions used

shall be the reference values specified by the

manufacturer. For those instances when a range of

values is specified rather than a reference value, the

midpoint of the range shall be taken to be the reference

value.

12.7.2 The reference power supply must be sufficiently

rated for the DUT. In addition, the following supply

conditions and tolerances shall apply:

DC supply reference voltage ± 0.1% of operating

voltage

Noise and ripple of DC

supply

 0.1% rms

13 Procedure

13.1 Zero Offset — Close the gas shut-off valve

upstream of the DUT and apply a 100% setpoint to the

DUT to equilibrate the pressure across the MFC. Wait

for the flow to stabilize at a value near zero; then close

the downstream shut-off valve. Deactivate the MFC’s

control valve (open for (NO) valves, closed for (NC)

valves), and allow the MFC to auto-zero if the an auto-

zero option is available. After the electrical output

signal has stabilized for at least three minutes, record

the MFC zero offset in Table 1. (Consult the

manufacturer’s specifications for the stabilization time

and report this time on Table 2.)

Table 1 Data Tabulation

Input % Set Point (sccm) Indicated Flow (sccm) Actual Flow (sccm)

40 Wait 5 minutes. Record no data.

100

Minimum