IPC-TM-650 EN 2022 试验方法.pdf - 第715页

5.2 Evaluation 5.2.1 During testing, examine the test specimens at 28th, 56th and 84th days. Prior to examining the test specimens, they shall be returned to 25°C [77°F] and 50% relative humid- ity for two hours. Evaluat…

Scope

This

test method is to determine the resistance of

the applied conformal coating to reverting to liquid when

exposed to high humidity at a specific temperature and time

condition for each class. This test method is to evaluate the

quality of the coated printed boards under storage conditions

(nonoperating).

Applicable Documents

IPC-CC-830

Qualification

and Performance of Electrical Insu-

lating Compound for Printed Board Assemblies

FED-STD-141

Method

4061 (Dry-Through For Varnish, Lac-

quers And Enamels)

Test Specimens

Five

coated ‘‘Y’’ shape patterns (see

Figure 1) containing two resistors, one with marking ink and

one with color code bars, coated with conformal coating per

the coating supplier’s recommendations.

Equipment

4.1 Desiccator

least 25 cm [9.84 in] in diameter

4.2

Potassium Sulfate

Reagent

grade potassium sulfate

4.3

Cotton Swabs

4.4 Oven

Capable

of maintaining temperature up to 100°C

[212°F].

4.5

Test Chamber

Capable

of maintaining a constant tem-

perature of 85° ± 2°C [185° ± 3.6°F] with 95 ± 4% relative

humidity

4.6

Soldering Iron

applicable

4.7

High Temperature Silicone Grease

5.0 Procedures

5.1 Desiccator Method

5.1.1

Prepare

a saturated solution of distilled or deionized

water and potassium sulfate (35 grams per 100 cm

temperature of 85° ± 2°C [185° ± 3.6°F]. Pour the solution

into the desiccator just below the ceramic plate. Crystals of

potassium sulfate should remain visible in the saturated solu-

tion during testing.

Note: Relative humidity is not to exceed 98%.

5.1.2 Place

four of the five test specimens on the ceramic

plate in the desiccator so that they are not touching each

other. The fifth specimen is used as a control.

5.1.3

Seal

the desiccator with high temperature silicone

grease and close the desiccator.

5.1.4

Place

the desiccator in the oven maintained at 85° ±

2°C [185° ± 3.6°F].

5.1.5 Allow

the desiccator, containing the test specimens,

to remain in the oven for 120 days.

75 mm

[2.95 in]

4.7 mm

[0.185 in]

38 mm

[1.50 in]

19 mm

[0.748 in]

6.30 mm [0.248 in]

2.3 ± 0.13 mm DIA

[0.091 ± 0.005 in DIA]

Hole 0.75 ± 0.08 mm DIA

[0.029 ± 0.003 in DIA]

0.75 mm [0.029 in MIN]

0.75 mm ± 008 mm [0.029 in ± 0.003 in MIN]

0.75 mm [0.029 in MIN]

3.2 mm

[0.126 in]

25 ± 1.5 mm

[0.984 ± 0.059 in MIN]

3.8 ± 0.13 mm DIA

[0.150 ± 0.005 in DIA]

HOLE 1.3 ± 0.08 mm DIA

[0.051 ± 0.0031 in DIA]

IPC-26111-1

Figure

1 ‘‘Y’’ Shape Pattern

2215

Sanders Road

Northbrook, IL 60062-6135

IPC-TM-650

TEST

METHODS MANUAL

Number

2.6.11.1

(Supersedes

2.6.11B for Conformal Coating Test)

Subject

Hydrolytic Stability - Conformal Coating

Date

07/00

Revision

Originating Task Group

Conformal Coating Task Group (5-33a)

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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ASSOCIA

TION CONNECTING

ELECTRONICS INDUSTRIES

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5.2

Evaluation

5.2.1

During

testing, examine the test specimens at 28th,

56th and 84th days. Prior to examining the test specimens,

they shall be returned to 25°C [77°F] and 50% relative humid-

ity for two hours. Evaluate the specimens for evidence of

reversion as indicated by softening, chalking, blistering, crack-

ing, tackiness, loss of adhesion or liquefaction. Evaluate also

legibility of the markings on the board and/or the resistors.

5.2.2 After

the 120-day aging period, the panels shall be

returned to 25°C [77°F] and 50% relative humidity and held for

seven days. The specimens shall be evaluated and compared

with the control specimen as per 5.2.1. The specimens shall

also be tested for tackiness in accordance with Method 4061

(Dry-Through For Varnish, Lacquers And Enamels) of FED-

STD-141.

5.3

Chamber Method

5.3.1

Place

four of the five test specimens into the test

chamber, by placing them in a rack or hanging, so that they

do not touch each other. The fifth specimen is held as a con-

trol. Close the chamber door.

5.3.2

Set

the chamber’s parameters at 85° ± 2°C [185° ±

3.6°F] and 95 ± 4% relative humidity. Activate the test cham-

ber and begin testing.

5.3.3

Allow

the specimens to remain in the test chamber for

120 days.

5.4

Evaluation

5.4.1

During

testing, examine the test specimens at 28th,

56th and 84th days. Prior to examining the test specimens,

they shall be returned to 25°C [77°F] and 50% relative humid-

ity for two hours. Evaluate the specimens for evidence of

reversion as indicated by softening, chalking, blistering, crack-

ing, tackiness, loss of adhesion or liquefaction. Evaluate also

legibility of the markings on the board and/or the resistors.

5.4.2

After

the 120-day aging period, the panels shall be

returned to 25°C [77°F] and 50% relative humidity and held for

seven days. The specimens shall be evaluated and compared

with the control specimen as per 5.2.1. The specimens shall

also be tested for tackiness in accordance with Method 4061

(Dry-Through For Varnish, Lacquers And Enamels) of FED-

STD-141.

IPC-TM-650

Number

2.6.11.1

Subject

Hydrolytic

Stability - Conformal Coating

Date

07/00

Revision

age2of2

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1.0

Scope

This

test method will demonstrate a relative

degree to which uncoated printed wiring boards are suscep-

tible to dendritic growth due to the presence of ionic residues

and condensed moisture. This test method is particularly suit-

able for printed wiring board manufacturing process control.

2.0

Applicable Documents

IPC-TR-476

How

to Avoid Metallic Growth Problems on

Electronic Hardware

MIL-P-551

Printed

Wiring Boards

3.0

Test Specimens

Test

pattern is chosen from, but not

restricted to e.g., MIL-P-55110 type ‘‘Y’’ pattern with a pair of

conductors having typically 15-30 mils separation (See Figure

1). A pair of parallel conductors on an uncoated production

printed wiring board, with spacing between conductors of

approximately 15-30 mils is suitable as well.

4.0

Equipment/Apparatus

4.1 Power Supply

dc power supply capable of providing

a metered 0-20 V dc, and 100 milliamps current.

4.2

Microscope

50-100

power microscope and means of

providing direct and/or indirect lighting on specimen.

4.3

Miscellaneous Items

water sample (2 oz.) kept in a

plastic bottle, eye dropper, a 1/2 watt-10K ohm current limit-

ing resistor and a stop watch.

5.0

Procedure

5.1 Preparation

5.1.1

Attach

a wire to each of the conductors on the ‘‘Y’’

pattern test board, or to corresponding, parallel conductors

on a production PWB.

5.1.2

Connect

a 10K resistor in series to the power supply

as shown in Figure 1. The resistor will limit the current to 1.5

milliamp maximum.

5.1.3 Place

the board for viewing on the microscope, so

that the parallel conductors are in view. Provide lighting that

will illuminate the test board on top and/or underneath.

5.1.4

Using

the eye dropper, place a drop of DI water

across the conductors that are in view under the microscope,

at least 0.5 inch away from the place where external wires are

attached to parallel conductors. Adjust power supply to 15 V

and turn the power supply on. Simultaneously start the stop-

watch.

5.1.5

Carefully

observe the action using the microscope.

Adjust the power of the microscope so the entire water area

is in view.

5.1.6 Bubbles

may appear within about 5 seconds. This is

hydrogen evolution-electrolysis of water.

5.1.7 Depending

on PWB ionic cleanliness level and the

characteristics of the PWB surface, there may be a dendritic

(tree-like) growth from the negative to positive conductor,

appearing within a typical (for a given board) but generally very

broad time span of a few seconds to several minutes.

5.1.8

The

condition of dendritic growth is much easier to

observe with an artificial light source placed under the test

board. A clear demonstration of the dendritic growth can be

performed if tap water containing ionic contamination is used

in place of DI water (see paragraph 5.1.4).

5.1.9

Once

the dendritic growth has reached the positively

charged conductor, most action will cease; turn off the stop-

watch. The elapsed time is a relative measure of susceptibility

of the PWB in question to undergo dendritic growth under

high humidity (condensed moisture) environment. At least ten

IPC-2613-1

Figure

The

Institute for Interconnecting and Packaging Electronic Circuits

2215 Sanders Road • Northbrook, IL 60062-6135

IPC-TM-650

TEST

METHODS MANUAL

Number

2.6.13

Subject

Assessment

of Susceptibility to Metallic Dendritic

Growth: Uncoated Printed Wiring

Date

10/85

Revision

Originating Task Group

N/A

Material

in this Test Methods Manual was voluntarily established by Technical Committees of the 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 the IPC.

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