IPC-TM-650 EN 2022 试验方法.pdf - 第724页

dressed from the bottom to prevent flux residues from the wire attachment from flowing onto the test patterns. With mechanical fixtures, fixtures should be to the side. Insert the limiting resistors in terminating leads …

4.6

Other Dedicated Fixtures

Hardwiring

is the default

connection method. Other dedicated fixtures may be used,

provided that the fixture does not change the resistance for

more than 0.1 decade compared to a comparable hardwired

system, when measured at the test conditions.

5 Procedure

5.1 Test Specimen Preparation

5.1.1

performing a material qualification (e.g., flux), all

specimens are to be cleaned and dried using a process

capable of yielding a minimum insulation resistance value of

4x10

ohm

when tested at 35°C, 85% minimum RH after

24 hours. If this test is being performed as a process qualifi-

cation, additional pre-test processing is not allowed.

5.1.2 A

minimum of three test specimens cleaned per 5.1.1

shall be used for controls.

5.1.3

For

liquid flux:

Apply the liquid flux to the entire surface of the test specimen

by brushing liberal quantities of the flux onto the specimen, by

floating the specimen comb side down on the liquid flux, or by

dipping the specimen into the flux. The specimen shall be

drained vertically for one minute with the fingers of the comb

pattern vertical. Alternatively, flux may be applied by produc-

tion application processes - spray, foam, or wave. The edge

connector fingers should be protected from flux.

It is recommended that production wave soldering equipment

be used for soldering the test specimens, with a preheat pro-

file representative of production. A solder fountain may be

used (not a solder pot), with a residence time similar to the

residence time in a solder wave. Solder composition is usually

60% tin ± 5%, remainder is lead; for such alloys, the solder

temperature shall be 250°C ± 6°C [482 ± 10.8°F]. For alloys

other than those with compositions near the tin-lead eutectic,

the solder temperature will be compatible with the usual sol-

dering temperature for the alloy used.

If any solder bridging occurs, that specimen shall be dis-

carded. A minimum of three specimens from the sample

group shall be tested.

5.1.4

For

solder paste:

A squeegee or screen printer shall be used with a stencil

imaged with the test pattern. It should be noted that the Tel-

cordia GR-78 pattern requires a minimum stencil thickness of

0.20 mm [7.9 mil]. Due to the fact that the minimum stencil

thickness is often dependent on the pitch or trace width and

spacing, a smaller stencil thickness may be used for fine fea-

tures and shall be agreed upon between the tester and cus-

tomer for the purpose of this test method.

Reflow the printed specimens using convection, infrared, or

vapor phase reflow equipment using a reflow profile represen-

tative of production. Equivalent methods may be used if such

equipment is not available.

If any solder bridging occurs, that specimen shall be dis-

carded. The edge connector fingers should be protected from

paste.

A minimum of three specimens from the sample group shall

be tested.

5.1.5

For

flux-cored wires:

Using a hand soldering iron and the cored wire under test,

carefully apply solder to the fingers of all comb patterns. The

edge connector fingers should be protected from flux.

If any solder bridging occurs, that specimen shall be dis-

carded.

A minimum of three specimens from the sample group shall

be tested. Each circuit path will be tested for the presence of

solder shorts using a resistance meter (e.g. digital multimeter).

5.1.6

Post

solder cleaning shall be performed only when

such cleaning is part of the production process used in the

final assembly.

5.1.7

When

evaluating incoming board quality and/or final

finishes, test specimens shall be used as received or as speci-

fied by the end user.

5.1.8

Attach

test leads to the land areas of all patterns either

by mechanical pressure (e.g., edge connectors, spring-loaded

pins) or by hand soldering using Rosin (R) cored wire, using a

shield to protect the test patterns from flux contamination dur-

ing soldering; the flux shall not spread into the pattern area.

Do not remove the flux.

5.2

Test Procedure

5.2.1

Place

the terminated test specimens in a suitable rack

that maintains the specimens at least 2.5 cm apart and such

that the air flow is parallel to the direction of the test speci-

mens in the chamber. For hardwiring, wires should be

IPC-TM-650

Number

2.6.14.1

Subject

Electrochemical

Migration Resistance Test

Date

09/00

Revision

age2of3

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dressed

from the bottom to prevent flux residues from the

wire attachment from flowing onto the test patterns. With

mechanical fixtures, fixtures should be to the side. Insert the

limiting resistors in terminating leads 1, 3, and 5 of each pat-

tern.

5.2.2 Place the rack approximately in the center of the test

chamber. Route the wires to the outside of the chamber;

dress the wiring away from the test patterns. Ensure that

drops of condensation cannot fall on the specimens.

5.2.3

the chamber and allow all samples to stabilize

for 96 hours at the specific temperature and humidity. After

the 96-hour stabilization period, the initial insulation resistance

measurements shall be made using voltage in the range of 45

VDC to 100 VDC. Due to polarity, measurements should be

made between terminals 1 and 2, 3 and 2, 3 and 4, and 5 and

4, at the specific temperature and humidity with the current

limiting resistors placed in series with the test circuit. Termi-

nals 2 and 4 shall be at one potential, and terminals 1, 3, and

5 at the opposite potential.

5.2.4

Connect

the samples to the power supply with the

current limiting resistors placed in series with the test circuit,

and apply 10 VDC for the duration of the test. The test polar-

ity shall be the same as the measurement polarity used in

section 5.2.3.

5.2.5

After

500 hours of applied bias (596 hours total), dis-

connect the power supply and repeat the measurements per

5.2.3 with the specimens under test conditions.

5.3

Data Handling

The

average (geometric mean) insula-

tion resistance (IR

avg

)

is calculated from:

avg

=10

[

log

]

where,

= number of test points (10 minimum),

individual insulation resistance measurements

Where an assignable cause of low insulation resistance, which

is properly attributable to the materials of construction or to

the process used to produce the test board, can be found,

then such a value can be excluded from calculating the aver-

age.

Such assignable causes include:

• Contamination on the insulating surface of the board, such

as debris, solder splints, or water droplets from the condi-

tioning chamber

• Incompletely etched patterns that decrease the insulating

space between conductors by an amount greater than that

allowed in the appropriate design requirements drawing

• Scratched, cracked, or obviously damaged insulation

between conductors

A minimum of 10 test measurements is required for the test to

be valid.

5.4

Visual Examination

After

completion of the test, the

test specimens shall be removed from the test chamber and

examined, with back-lighting, at 10x magnification for evi-

dence of electrochemical migration (filament growth), discol-

oration, and corrosion.

Note: Localized electrochemical migration on one comb may

be caused by a testing anomaly.

Notes

6.1 Reference Documents

6.1.1 IPC-TR-476A

Electrochemical

Migration: Electrically

Induced Failures in Printed Wiring Assemblies

6.1.2

IPC-9201

Surface

Insulation Resistance Handbook

6.1.3

Telcordia GR-78-CORE

6.2 Specification of Test Conditions

Users

of this test

method will need to specify one (1) of the three (3)

temperature/humidity conditions called out in section 4.1.

Note that IPC-TR-476A recommends using 65°C, 85% RH.

IPC-TM-650

Number

2.6.14.1

Subject

Electrochemical

Migration Resistance Test

Date

09/00

Revision

age3of3

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Scope

This

test method is designed to determine the

corrosive properties of flux residues under extreme environ-

mental conditions. A pellet of solder is melted in contact with

the test flux on a sheet metal test piece. The solder is then

exposed to prescribed conditions of humidity and the result-

ing corrosion, if any, is assessed visually.

Applicable Documents

IPC J-STD-004

Requirements

for Soldering Fluxes

IPC-TM-650

Test

Methods Manual

2.3.34 Solids Content, Flux for Fluxes for Soft Soldering

IEC

61189-5

Test

Methods for Electrical Materials, Intercon-

nection Structures and Assemblies - Part 5: Test Methods for

Printed Board Assemblies

Test Specimen

least 0.035 g of flux solids, 0.3 g sol-

der paste, 1 g wire, or 1 g preform with an equivalent amount

of solids. Flux solids are defined as the residue described in

IPC-TM-650, Test Method 2.3.34, Solids Content, Fluxes. All

solvent must have been evaporated from the specimen in a

chemical fume hood.

4 Apparatus and Reagents

4.1 Apparatus

4.1.1

Solder

pot.

4.1.2

Humidity

chamber capable of achieving 40 ± 3 °C

[104 ± 5.4 °F] and 93 ± 5% relative humidity.

4.1.3 Air

circulating drying oven.

4.1.4

Microscope

having 20X minimum.

4.1.5

Analytical

balance capable of weighing 0.001 g.

4.1.6

Three

50 mm x 50 mm x 0.5 mm [1.969 in x 1.969 in

x 0.00197 in] 99% pure copper sheets.

4.1.7

mm [0.748 in] steel ball (approximate).

4.1.8 Laboratory

press.

4.1.9

Tongs.

4.2

Reagents

All

chemicals must be reagent grade and

water must be deionized (2 megohm-cm minimum resistivity

recommended).

4,2,1

Ammonium

persulphate.

4.2.2

Sulfuric

acid, relative density 1.84.

4.2.3

Degreasing

agent: acetone, or petroleum ether.

Procedures

5.1 Chemicals

5.1.1

Ammonium

persulphate (25% m/v in 0.5% v/v sulfuric

acid). Dissolve 250 g of ammonium persulphate in water and

add cautiously 5 ml of 5% sulfuric acid (relative density 1.84).

Mix, cool, dilute to 1 liter and mix. This solution should be

freshly prepared.

5.1.2

Sulfuric

acid (5% v/v). To 400 ml of water cautiously

add 50 ml of sulfuric acid (relative density 1.84). Mix, cool,

dilute to 1 liter and mix.

5.2

Test Panel

5.2.1

Form

a 3.0 mm [0.018 in] (approximate) deep circular

depression in the center of the copper test panel by forcing a

19.0 mm [0.018 in] steel ball into a 25 (approximate) mm hole

to form a cup.

5.2.2 Bend

one corner of the test panel up to facilitate sub-

sequent handling with tongs.

5.3

Test Panel Pretreatment

5.3.1

Immediately

before performing test, pretreat as follows

using clean tongs for handling.

5.3.2

Degrease

with a suitable neutral organic solvent such

as acetone, or petroleum ether.

2215

Sanders Road

Northbrook, IL 60062-6135

IPC-TM-650

TEST

METHODS MANUAL

Number

2.6.15

Subject

Corrosion,

Flux

Date

06/04

Revision

Originating Task Group

Flux Specifications Task Group, (5-24a)

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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