IPC-TM-650 EN 2022 试验方法.pdf - 第602页

1 Scope This test method covers the two-wire resistance test for the determination of the volume resistivity of polymer- based conductive pastes and other conductive materials used in HDI. This test is valid for conducti…

5.5

Calculations

5.5.1

The

volume resistivity shall be calculated as follows:

r=RA

Where:

r = Volume resistivity in megohm-centimeters

R = Measured volume resistance in megohms

A = Effective area of the guarded electrode in square centi-

meters

T = Average thickness of specimen in centimeters

T = (t) x 2.54 [see 5.2.1]

t = Average thickness (t) in inches (from 5.4)

Note:

The

value of A may be obtained from the Dimension

Table.

5.5.2

The

surface resistivity shall be calculated as follows:

Where:

Surface resistivity in megohms

Measured surface resistance in megohms

P = Effective perimeter of the guarded electrode in centime-

ters

D4 = Width of the test gap in centimeters

Note:

The

ratio of P/D4 for the electrode configuration being

used may be obtained from the Dimension Table included in

Figure 1.

5.6

Reporting

5.6.1

The

volume resistivity of each specimen and the aver-

age shall be reported. Each condition tested shall be reported

separately.

5.6.2 The surface resistivity of each specimen and the aver-

age shall be reported. Each condition shall be reported sepa-

rately.

5.6.2.1 The

surface resistance is the direct reading of the

megohmeter scale and should be recorded in megohms.

6.0

Notes

6.1

For

additional information see ASTM-D-257, D-C Resis-

tance or Conductance of Insulating Materials.

6.2

The

system of electrical connections to the specimens

may benefit from a coaxial cable set-up designed to shield the

measurement of volume or surface resistances from electrical

interference.

6.3

Performance Specifications

The

following informa-

tion should be reviewed within the applicable performance

specification or product procurement document:

a. Specimen size, quantity, and configuration, if other than

that specified in 3.0.

b. Conditioning parameters, such as temperature for Elevated

Temperatures.

c. Any other changes to the specified procedures in this

method.

IPC-TM-650

Number

2.5.17.1

Subject

Volume

and Surface Resistivity of Dielectric Materials

Date

12/94

Revision

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Scope

This

test method covers the two-wire resistance

test for the determination of the volume resistivity of polymer-

based conductive pastes and other conductive materials used

in HDI. This test is valid for conductive materials with volume

resistivity on the order of 10

-5

Ω-cm

or higher. For measuring

resistivity on highly conductive materials or any material that

cannot be patterned into a circuit pattern, a four-wire (Kelvin

Probe) test method, such as IPC-TM-650, Method 2.5.14, is

recommended.

1.1

Definition

Volume

resistivity is a material property that

can be utilized to calculate the resistance in a circuit design.

For materials with high resistivity, a two-wire resistance test

may be used to measure the volume resistivity.

The resistance in any sample (R in units of Ω) is related to the

dimensions of the test circuit and the volume resistivity (ρ)

inherent in the material (see Figure 1).

R =ρ

(

)

W, and t are the length, width, and thickness respectively

of the test circuit (in cm). The quantity L/W is called a square,

([). The volume resistivity can then be expressed as:

ρ=

(

)

[

with

units of ohms-cm (Ω-cm).

Applicable Documents

IPC-TM-650

Test

Methods Manual

2.5.14 Resistivity of Copper Foil

Test Specimen

The

test specimen is a 0.5 mm wide

serpentine circuit pattern (see Figure 2) with a length of

between 200 [ and 1000

(length

equal to 200 to 1000

times the width) prepared by screen printing or other meth-

ods. Specimens may be prepared by other methods, as long

as they have measurable dimensions. If materials cannot be

prepared in a circuit pattern, see 6.2.

IPC-2-5-17-2-1

Figure

1 Resistivity Diagram

Conductor

Length = L

Current Flo

Width = W

Thickness = t

IPC-25172-2

Figure

2 Serpentine Pattern

The

Institute for Interconnecting and Packaging Electronic Circuits

2215 Sanders Road • Northbrook, IL 60062

IPC-TM-650

TEST

METHODS MANUAL

Number

2.5.17.2

Subject

Volume

Resistivity of Conductive Materials Used in

High Density Interconnection (HDI) and Microvias,

Two-Wire Method

Date

11/98

Revision

Originating Task Group

HDI Test Methods Task Group (D-42a)

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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3.1

Conductor

Any

high resistance conductor used in HDI

applications (polymer thick film, via fill, metal, metal compos-

ites, transient liquid phase sintering, organometallic, conduc-

tive polymer, etc.). Copper foils used in HDI should be tested

according to IPC-TM-650, Method 2.5.14.

3.2

Substrate

Unless

otherwise specified, the substrate

shall be a PCB laminate, etched to remove all copper. Other

acceptable substrates (when specified) may be plate glass,

insulated metals, or flexible circuit base material.

3.3

Screen

For

materials that are screen printed, unless

otherwise specified, the screen shall be as outlined in 3.3.1

through 3.3.3.

3.3.1

Type

200

mesh, stainless steel, 35 µm wire

3.3.2

Emulsion

<15

µm emulsion build up

3.3.3

Wire Angle

22.5°

to 45°

3.4

Typical Patterns

3.4.1 Pattern

Serpentine

with 0.5 mm wide lines and

spaces and 200 [ to 1000 [ long (10 cm to 50 cm). The

larger the number of squares, the higher the resistance and

more accurate the measurement.

3.4.2

1.25

mm snapoff

0.2 Kg to 1.0 Kg squeegee pressure per cm squeegee length

2.5 cm/sec. to 12.5 cm/sec. draw speed

3.5

Cure Conditions

The

conductor shall be cured

according to the manufacturer’s specifications. Parts are

allowed to cool to room temperature, after which they are

measured for resistance.

Equipment/Apparatus

4.1

digital multimeter capable of resolving 0.1 Ω resis-

tance is required. This unit must be accurately calibrated. An

example would be a Fluke 70 series digital multimeter. For

improved accuracy in this measurement, a larger number of [

and/or a more sensitive multimeter can be utilized.

4.2

screen printer capable of making 0.5 mm line/space

circuitry, or any other method for preparing the desired circuit

pattern

4.3

Equipment

to measure the test circuit conductor length,

width, and thickness. If the number of squares is accurately

known (length/width of circuit) from the artwork and standard

process conditions, then only the thickness needs to be mea-

sured on each specimen. Thickness can be determined by

various methods: cross-section/optical microscopy, profilo-

meter measurement, or calculation from deposition weight

and material density. If the circuit thickness is very uniform,

then optical sectioning is the preferred method for obtaining

the thickness. If the circuit thickness is thought to be non-

uniform, thickness may then be determined by averaging pro-

filometer readings or determining average thickness from the

weight of the material deposited (knowing the length, width,

and density that the thickness can be determined).

Procedure

5.1 Samples

Prepare

a minimum of five test specimens

according to 3.1 through 3.5.

5.2

Conditioning

Condition

the specimens at 23°C ± 5°C,

50% RH (± 5%) for 24 hours.

5.3

Measurement

5.3.1

Measure

the circuit length, width, and thickness using

the equipment described in 4.3.

5.3.2

Apply the digital multimeter leads to the pads at each

end of the circuit. Measure and record the resistance in ohms.

For a resistance less than 2 Ω, see 6.1.

5.3.3

Measure

the resistance of a minimum of five speci-

mens and average the values.

5.4

Calculation

Calculate

the volume resistivity for each

specimen from the equation below:

(

)

where:

= average resistance of a single specimen in ohms

t = thickness of the conductive specimen in cm

L = length conductive specimen in cm

W = width conductive specimen in cm

Note: The ratio L/W is the number of squares.

IPC-TM-650

Number

2.5.17.2

Subject

Volume

Resistivity of Conductive Materials Used in High Density

Interconnection (HDI) and Microvias, Two-Wire Method

Date

11/98

Revision

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