IPC-TM-650 EN 2022 试验方法.pdf - 第683页

of one, even though there are four distinct comb patterns and measurements. 7.1.2 Sample Sizes The number of samples should not be stipulated in the test method. The number should be in the specifications referring to th…

5.1.1 Hardwired samples need to be soldered without

adverse effect to test vehicles. Common good soldering

practice should be followed. Sample should be covered. See

IPC-9201 for reference. Heat should not be allowed to dam-

age sample. Flux is of great concern. Often samples can be

soldered without the use of flux, so users of this method

should have solid wire solder on hand. If flux is deemed nec-

essary by qualitative observation, use rosin nonactivated flux.

Wire all samples and retain relationship of interconnection

between test vehicle and testing system (nets, channels, etc.).

5.1.2 Connector interfacing inside the chamber has been

shown to be a capable implementation for SIR; however, as

the connectors are exposed to high heat and humidity they

obviously require a good deal of maintenance and verification.

5.2 Fixture samples in the chamber uniformly, vertically, and

parallel to airflow. The minimum spacing between samples

shall be 12.5 mm [0.5 in]. If hardwiring is used, dress wires

down from samples. Make appropriate connections to switch-

ing system.

5.3 Measurement and stress bias voltage are the same.

5.3.1 Apply direct current electrical bias to produce a field

strength of 25 ± 1 V/mm between adjacent parallel traces.

Assuming that SIR is much greater than current limiting resis-

tance this field corresponds to an applied voltage of 5 ± 0.2 V

for 200 µm [0.0079 in] spacing (example is technically equiva-

lent to IEC 61189-5). This bias shall be in place during an

aggregate 90% (minimum) of temperature/humidity condition-

ing (remaining percentage is related to measurement) in order

to facilitate electrochemical reactions.

5.3.2 Seal the chamber and ramp from laboratory ambient

conditions to 25 °C and 50% R.H. Dwell for one hour. Verify

the electrical system setup by taking a series of all measure-

ments at these specified ambient conditions. Because classi-

fication or ranking of sample performance by SIR at ambient

is not appropriate for these test vehicles, clarity suggests that

measurements need not be reported unless ‘‘shorts’’ are

observed and therefore the corresponding samples are

deemed inappropriate for test.

5.4 Increase the temperature to 40 °C while maintaining the

humidity at 50% R.H. ± 3% R.H. and dwell at this tempera-

ture for 15 minutes. After this period, gradually increase, within

0.5 hour, the relative humidity to 90±3%R.H.Donotallow

the temperature of the samples to drop below the dew point.

5.5 Allow chamber to stabilize at set point for one hour.

5.6 Duration of test shall be not less than 72 hours.

5.7 Take and record all SIR measurements (every unique net

or channel) at least once every 20 minutes.

5.8 After conditioning, remove samples from chamber and

examine at 30 to 40X in light field and dark field (back light).

Record the following:

a) Presence of dendrites: Yes/No

b) Maximum percent reduction of spacing: 0% for no den-

drites 1% to 100% for worst-case dendrite. Capture and

record image of worst case dendrite.

c) Presence of discoloration between conductors: Yes/No; if

yes, capture and record image.

d) Presence of water spots. Yes/No; if yes, capture and

record image.

e) Presence of subsurface metal migration. Yes/No; if yes,

capture and record image.

6 Reporting

6.1

Deviations from test method or specification shall be

recorded. All standard reporting shall be incorporated, includ-

ing enough information to exactly reproduce the test (equip-

ment, personnel, deviations or options within the method

etc.).

6.2 All items listed in 5.8.

6.3 All SIR measurements are to be reported in the form of

Log

), where R

is the measured SIR of the i

measure-

ment.

7 Notes

7.1 Sampling

When using this test method for materials

characterization the sample selection, preparation and

requirements should follow IPC-J-STD-004.

When using this test method for process characterization the

sample selection, preparation and requirements should follow

IPC-J-STD-001.

This methodology may also be used with other specifications.

7.1.1 A test vehicle should be considered a sample count of

one. For example, an IPC-B-24 test vehicle is a sample count

IPC-TM-650

Number

2.6.3.7

Subject

Surface Insulation Resistance

Date

03/07

Revision

Page3of4

of one, even though there are four distinct comb patterns and

measurements.

7.1.2 Sample Sizes The number of samples should not be

stipulated in the test method. The number should be in the

specifications referring to this test method. However, it is rec-

ognized that there will be users who are attempting process

or material characterization and may be uncertain about how

many samples to specify.

With respect to the second bulleted item in the scope, (Pro-

vide metric(s) that can appropriately be used for binary classi-

fication (e.g., go/no go, pass/fail), a minimum sample size of

10 is suggested.

With respect to the third bulleted item in the scope, (Compare,

rank or characterize materials and processes) a minimum

sample size of three is suggested.

7.1.3 When characterizing material, samples can be pro-

cessed on the same panel.

7.1.4 When characterizing process(es), samples should at a

minimum be processed on different panels, preferably in dif-

ferent production runs.

7.2 The derived unit of surface resistivity and its expression

as ohm/square cannot be defined for this method or similar

methodologies due to the nonlinear response of the test

vehicles and the assumed nonhomogeneous concentration of

ionic contaminates.

7.3 Careful considerations must be used when developing

an implementation of this method. Seemingly adequate set-

ups can (and historically have) caused unacceptable uncer-

tainty of results. If the user of this method is not intimately

familiar with the technologies involved, ASTM D 257 and IPC-

9201 are highly recommended.

IPC-TM-650

Number

2.6.3.7

Subject

Surface Insulation Resistance

Date

03/07

Revision

Page4of4

Scope

This

test method is used to determine the total

mass loss (TML) and collected volatile condensable material

(CVCM) of materials when exposed to a heated vacuum envi-

ronment. Mass loss may be due to outgassing of low molecu-

lar weight materials present in printed boards such as trapped

plating solutions, improper lamination, and uncured adhesives

which are known to cause contamination or corrosion of

spacecraft equipment.

Applicable Documents

NASA General Speciﬁcation No. SP-R-0022

Vacuum

Sta-

bility Requirements of Polymeric Material for Spacecraft Appli-

cation.

ASTM

E 595

Standard

Test Method for Total Mass Loss and

Collected Volatile Condensable Materials from Outgassing in a

Vacuum Environment.

Test Specimens

The

test specimen shall be cut into

small pieces that can fit into the specimen boats and whose

total mass shall be about 200 mg. If smaller masses are used

the accuracy of the TML and CVCM determinations may be

impaired. It is imperative that the specimens not be contami-

nated during the preparation process. Specimens are not to

be handled with bare hands since human skin oils are volatile

and condensable by this method thereby creating misleading

TML and CVCM results. If there is any doubt about specimen

contamination the specimens should be cleaned using sol-

vents known to be nonreactive and that leave no residue. An

average of at least three (3) samples shall be made for each

test.

Apparatus or Material

4.1

Multiple

specimen vacuum chamber capable of main-

taining a vacuum of at least7X10

-3

(5 X 10

-5

Torr)

with

resistance heated copper bars capable of maintaining 125 °C

± 1 °C [257 °C ± 1.8 °F] during the 24 hour test run and typi-

cally containing 24 specimen chambers. Typically, three (3) of

the specimen chambers are maintained as controls. The open

end of each specimen chamber allows vapors from the speci-

men to pass through a hole into a collector chamber where

the vapors are condensed on a collector plate that is main-

tained at 25 °C ± 1 °C [77 °F ± 2 °F) throughout the test. See

ASTM E 595 for further details and requirements for the con-

struction and cleaning of the test apparatus.

4.2

analytical balance capable of measuring the speci-

mens, boats, and collector plate mass to the nearest micro-

gram (0.000001 gram).

4.3 Glass

desiccator using active silica gel desiccant. Low

vapor pressure grease shall be used for the ground glass

joints.

4.4

Conditioning

chamber capable of maintaining 50% ± 5%

relative humidity and 23 °C ± 2 °C [73 °F ± 4 °F).

4.5

Prepared

aluminum foil specimen boats.

4.6

Suitable cleaning solvents

Mixtures

of 1:1:1 by vol-

ume chloroform:acetone:ethanol and 1:1 by volume

acetone:ethanol solvent blends have been successfully used

for cleaning and degreasing the apparatus, aluminum boats,

and collector plates. All solvents shall be spectrophotometer

grade purity or equivalent. See Annex A1 of ASTM E 595 for

details regarding cleaning and storage procedures for the

equipment used in this test.

4.7

Nitrogen

gas, 99.9% pure, or better, with a dew point of

-60 °C [-76 °F] or less. The nitrogen gas shall be filtered using

a Molecular Sieve 5A or equivalent.

4.8

Wiping

materials and swabs for cleaning. These material

shall be preextracted using solvents with which they will be

used.

4.9

Suitable

gloves or finger cots to be used during sample

preparation.

Procedure

5.1

Weigh

a prepared aluminum foil boat to the nearest

microgram and return it to the glass storage desiccator.

5.2

Weigh

a prepared collector plate to the nearest micro-

gram and mount it into its cooling plate receptacle.

5.3

Add

the test specimen to the boat and condition the

specimen at 50% ± 5% relative humidity at 23 °C ± 2 °C

[73 °F ± 4 °F] for a minimum of 24 hours. Weigh the condi-

tioned specimen and boat to the nearest microgram.

2215

Sanders Road

Northbrook, IL 60062-6135

IPC-TM-650

TEST

METHODS MANUAL

Number

2.6.4

Subject

Outgassing,

Printed Boards

Date

05/04

Revision

Originating Task Group

Rigid Printed Board Performance Task Group

(D-33a)

Material

in this Test Methods Manual was voluntarily established by Technical Committees of IPC. This material is advisory only

and its use or adaptation is entirely voluntary. IPC disclaims all liability of any kind as to the use, application, or adaptation of this

material. Users are also wholly responsible for protecting themselves against all claims or liabilities for patent infringement.

Equipment referenced is for the convenience of the user and does not imply endorsement by IPC.

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