IPC-TM-650 EN 2022 试验方法.pdf - 第722页

1 Scope This test method provides a means to assess the propensity for surface electrochemical migration. This test method can be used to assess soldering materials and/or processes. 2 Applicable Documents 2.1 IPC IPC-B-…

a. Contamination on the insulating surface of the board such

as lint, solder splines, or water droplets from the condition-

ing chamber.

b. Incompletely etched patterns that decrease the insulating

space between conductors by more than the amount

allowed in the appropriate design requirements drawing.

c. Scratched, cracked or obviously damaged insulation

between conductors.

6 Notes

6.1

Protective coatings are helpful in preventing electro-

chemical migration, but there is no assurance that the protec-

tion is complete unless the coating is adequately bonded to a

good clean board.

IPC-TM-650

Number

2.6.14

Subject

Solder Mask - Resistance to Electrochemical Migration

Date

03/07

Revision

Page4of4

Scope

This

test method provides a means to assess the

propensity for surface electrochemical migration. This test

method can be used to assess soldering materials and/or

processes.

Applicable Documents

2.1 IPC

IPC-B-25

Multipurpose

Test Board

IPC-B-25A

Multipurpose

Test Board

IPC-6012A

Qualification

and Performance Specification for

Rigid Printed Boards

IPC-9201

Surface

Insulation Resistance Handbook

2.1

American Society for Testing and Materials (ASTM)

ASTM D-257-93

Standard

Test Methods for DC Resistance

or Conductance of Insulating Materials

Test Specimens

IPC-B-25

(B or E pattern) or IPC-B-25A

(D pattern) test boards shall be used, with conductor line

widths and spacings of 0.318 mm [0.01250 in]. The method

of manufacture should provide optimized conductor edge

definition (refer to the Class 2 and 3 conductor width require-

ments in IPC-6012). The finished test boards should be

untreated, bare copper, unless another surface finish is part of

the evaluation. Figure 1 shows the IPC-B-25A test board; the

D pattern is identical to the IPC-B-25 B or E pattern. For pro-

cess evaluation, the test pattern board should be made using

the same substrate material as will be used in practice to

duplicate actual working conditions.

Equipment/Apparatus

4.1 Test Chamber

temperature/humidity chamber

capable of producing an environment of 40°C ± 2°C [104 ±

3.6°F], 93% ± 2% RH, 65°C ± 2°C [149 ± 3.6°F], 88.5% ±

3.5% RH, or 85°C ± 2°C [185 ± 3.6°F], 88.5% ± 3.5% RH

and allowing test boards to be electrically biased and mea-

sured without being opened under these temperature and

humidity conditions is used.

4.2

Measuring Equipment

High

resistance measuring

equipment, equivalent to that described in ASTM D-257-93,

with a range up to 10

ohm

and capable of yielding an accu-

racy of ± 5% at 10

ohm

with an applied potential of 100 VDC

(10% tolerance); standard resistors should be used for routine

calibration.

4.3

Power Supply

Equipment

capable of providing 10

VDC at 100 µA, with a 10% tolerance, shall be used.

4.4

Current-Limiting Resistors

Use

one 10

ohm

resistor

in each current path. This equates to three current-limiting

resistors for each 5-point comb pattern. Note that some test

equipment has the current limiting resistors built into the test-

ing system.

4.5

Connecting Wire

Use

PTFE-insulated, solid-

conductor, copper wire, or equivalent. (See IPC-9201 Surface

Insulation Resistance Handbook.)

IPC-26141-1

Figure

1 IPC-B-25A Test Board

2215

Sanders Road

Northbrook, IL 60062-6135

IPC-TM-650

TEST

METHODS MANUAL

Number

2.6.14.1

Subject

Electrochemical

Migration Resistance Test

Date

09/00

Revision

Originating Task Group

Electrochemical Migration Task Group

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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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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