IPC-TM-650 EN 2022 试验方法.pdf - 第369页

1 Scope To describe the strain gage method for determin- ing linear thermal expansion of laminated materials within the temperature range of –55 °C to +130 °C and inorganic sub- strates (nonlaminated) with a range of –55…

where:

specimen length

(

∆L

)

t = certified

expansion of the reference material.

(∆L/L

)

the measured expansion of the reference mate-

rial.

(

∆L

)

s = the

expansion of the vitreous silica parts of the dila-

tometer.

5.4

Test Procedure

Following

the conditioning steps per

5.2, two thermal cycles shall be conducted per test. The first

is to normalize the specimen and the second to generate data

for the calculation of CTE.

5.4.1

Measure

the initial length of the specimen, using the

micrometer to ± .001 inch.

5.4.2

Place

the specimen in the dilatometer after making

certain that all contacting surfaces are free of foreign material.

Specimens with thickness 0.125 inch shall be supported with

side plates. Care must be taken to assure good seating of the

specimen against the bottom of the tube bottom and the push

rod.

5.4.3

Place

the thermocouple sensor in intimate contact

with the specimen at midlength.

5:4.4 Mount

the transducer to provide a stable contact with

the probe. The sample loading force shall be the minimum

necessary for proper contact between the rod and specimen,

and the bottom of the tube and specimen. Set the transducer

at a nominal initial reading.

5.4.5

Place

the assembled dilatometer into the chamber

and allow the temperature of the specimen to come to equi-

librium.

5.4.6

Record

the initial readings of the thermocouple and

the transducer.

5.4.7

Heat

and cool at a constant rate of 2°C/min.

5.4.8

Record

length changes as a function of temperature.

5.4.9 Remove

the specimen from the fixture and repeat the

procedure per 5.4.1-5.4.8, following the first cycle. Remea-

surement of the specimen length must not be omitted prior to

start of the second cycle.

5.4.10

Test

a total of four specimens, two prepared with the

length in the machine direction of the laminate reinforcement

and two cut in the transverse direction. This quantity is

intended to represent the expansion characteristics of a 18

inch x 24 inch panel size.

6.0

Calculations

6.1

Linear

thermal expansion (LTE), the change in length per

unit length resulting from a temperature change is represented

by:

∆L

= A

(

∆L

)

(

∆L

)

where:

(

∆L

)

the expansion as indicated by the transducer, ∆Listhe

observed change in length (∆L=L

–L

LTE is often

expressed in µm/m (parts per million).

6.2

Mean

coefficient of linear thermal expansion – the linear

thermal expansion per change in temperature. Represented

by:

∝ m =

∆L/L

∆T

–L

)

–T

)

where

and

are

the lengths of the specimen at the test

temperatures T

and

6.3

Instantaneous

coefficient of linear thermal expansion –

the slope of the linear thermal expansion curve at temperature

T. Represented by:

∝ T =

dT,

6.4

Plots

of the following are commonly used as required:

∆L

vs.

T; ∝ m vs. T

When reporting the mean coefficient of thermal expansion, the

temperature ranges must be specified.

IPC-TM-650

Number

2.4.41.1

Subject

Coefficient

of Thermal Expansion by the Vitreous Silica (Quartz)

Dilatometer Method

Date

8/97

Revision

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Scope

describe the strain gage method for determin-

ing linear thermal expansion of laminated materials within the

temperature range of –55 °C to +130 °C and inorganic sub-

strates (nonlaminated) with a range of –55 °C to +150 °C.

1.1

Care

should be taken if the higher temperatures are

used. The adhesive shown is rated by the manufacturer from

less than –200 °C to greater than +300 °C; however, for

higher temperature pretesting with the Titanium Silicate Stan-

dard or materials of known thermal expansion characteristics

is recommended.

Applicable Documents

None

Test Specimens

3.1

Specimens

are normally flat pieces of laminate or printed

wiring boards/assemblies that are to be tested nondestruc-

tively. Dimensions are to be 50.0 mm x 50.0 mm [2.0 in X

2.0 in] minimum by 1.5 mm [0.060 in] minimum thick.

Plated-through holes in the specimen are not desirable, but

can be tolerated to a certain extent. If possible, the strain

gages are to be located as far from the PTHs as possible and

centered with regard to surrounding PTHs. Mounting strain

gages over PTHs will result in measurements that may not be

representative of the sample material.

For each material or lot tested, a minimum of three determi-

nations shall be made in each of the x and y directions.

Apparatus

4.1

Silicon

carbide paper, 220, 320 and 400 grit

4.2

Cotton

tipped applicator

4.3

Tweezers,

stainless steel, Style 3C

4.4

Scissors,

stainless steel, 2 to 4 inch blades

4.5

Tape,

Mylar, transparent, 1/2 inch wide

4.6 Tape,

Mylar, transparent 1 inch

4.7 Tape,

PFTE, 1 inch wide, no adhesive

4.8 Binder

clips, No. 100, large

4.9

Binder

clips, No. 20, small

4.10

Silicone

gum pad (2.5 mm [0.0984 in] thick) with metal

backup plate

4.11

Test

plate constructed of 1.25 mm [0.050 in] thick

Alloy 42 plated with 0.025 mm [0.001 in] of copper

4.12

M-Prep

Conditioner A or equivalent

4.13

M-Bond

610 Adhesive or equivalent (M-Bond 600 for

lower cure temperatures, if applicable)

4.14

M-Prep

Neutralizer 5 or equivalent

4.15

M-Coat

B, Nitrile rubber coating

4.16

Cleaning

solvent, Isopropan OL or equivalent

4.17

Strain

gages, Type WK-06-250BG, Measurements

Group Inc. (Other strain gages may be selected for customiz-

ing for a specific material or temperature range.)

4.18

Alloy

42 Holding Fixture (∝30-400 °C) = 4.5-5.0

ppm/°C

4.19

Solder

terminals, Type CEG-63S, Measurements

Group Inc. (Terminal may be integral when using WK series

strain gage with option W.)

4.20 Select

a solder that will maintain a connection at test

temperature;

Solder Sn-63/Pb-37 Liquidus = 183 °C [361 °F]

Solder Sn-96.5/Ag-3.5 Liquidus = 221 °C [430 °F]

Solder Pb-97.5/Ag-1.5/Sn-1 Liquidus = 309 °C [588 °F]

4.21

Solder

Flux, Type RMA or equivalent

4.22

Soldering

Iron, 15 to 25 watt

4.23

M-line

Rosin Solvent, Measurements Group Inc.

4.24

Oven

for Curing M-Bond Adhesive with heat rise of

3 °C to 11 °C/min [5 °F to 20 °F/min].

4.25 Gauze

Sponge

2215

Sanders Road

Northbrook, IL 60062-6135

IPC-TM-650

TEST

METHODS MANUAL

Number

2.4.41.2

Subject

Coefficient

of Thermal Expansion—Strain Gage

Method

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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4.26

Thermal

cycling chamber for thermal cycling with a

heat rise capability of 2 °C to 30 °C/min [3 °F to 54 °F/min],

and equipped with a programmable temperature control sys-

tem

4.27

Thermocouple

Type J (Type may be used where appli-

cable)

4.28

Titanium

Silicate Standard

Corning Glass Works Code 7971ULE, or

Measurements Group Inc. #TSB-1

4.29

Wheatstone

Bridge

*See 6.1 for source of materials.

Strain Gage Mounting Procedure

The

procedure for

mounting the strain gages to the PCB material and titanium

silicate or other standards as appropriate, includes the prepa-

ration of the adhesive and specimen bonding surfaces, appli-

cation of the adhesive, attachment of the strain gages, and

the assembly of the Alloy 42 holding fixture. (The Alloy 42 fix-

ture may not be required, depending on specimen type and

application.)

5.1

Adhesive Preparation

The

strain gages are to be

mounted using adhesive M-Bond 610 or equivalent. The

M-bond 610 is a two-component system that is mixed as fol-

lows:

5.1.1

The resin and curing agent bottle are to be at room

temperature before opening.

5.1.2

Using

the disposable plastic funnel, empty contents of

bottle labeled ‘Curing Agent’ into the bottle of resin labeled

‘Adhesive’ (discard funnel).

5.1.3

After

tightening the brush cap (included separately),

thoroughly mix contents of the ‘Adhesive’ bottle by shaking

for 10 seconds.

5.1.4

Identify

the ‘Adhesive’ bottle by writing the date on the

label. Allow the freshly mixed adhesive to stand for a minimum

of one hour before using.

5.2

Sample Preparation

Two

strain gages are applied to

one side of the PCB board test specimen at right angles to

one another and to the titanium silicate reference standard

using the following procedure:

5.2.1

Mark

reference lines perpendicular to each other on

the test specimen and the titanium silicate standard. For most

printed board material this is easily accomplished by making a

burnish mark with the wooden end of a cotton-tipped swab

applicator.

5.2.2

Thoroughly

degrease the gaging areas with cleaning

solution.

5.2.3

Dry

abrade the area to be bonded with 220 or 320 grit

silicon carbide paper, and follow with a final with a final abrad-

ing with 320 or 400 grit paper on the areas thoroughly wetted

with M-prep Conditioner A. Scrub the gaging areas with

repeated applications of Conditioner A using a cotton tipped

swab and until a clean cotton swab or lint free pad is no

longer discolored. Remove all residues and Conditioner A by

wiping thoroughly with a gauze sponge. Do not allow to dry

while cleaning before use of the sponge to prevent the con-

taminating films.

5.2.4

Apply

a liberal amount of M-Prep Neutralizer 5 and

scrub with a cotton-tipped applicator or lint free pad. Using a

single slow wiping motion with gauze sponge, carefully dry the

surface. Do not wipe with a back and forth motion as this may

allow contaminants to be redeposited.

5.3

Strain Gage Installation

Apply

the strain gages to the

previously cleaned areas of the PCB specimen and the tita-

nium silicate standard using the following procedure:

5.3.1

Remove

the gage from the acetate envelope with

tweezers; do not bend the gages. Place the gage bond side

down onto the cleaned area of the specimen. If a solder ter-

minal is to be incorporated, position it next to the gage. Place

a short length of Mylar tape over about half of the gage tabs

and entirely over the terminals.

5.3.2

Peel

back one end of the taped assembly (by lifting at

a small angle) so as to raise both gage and terminal. By curl-

ing the Mylar tape back upon itself, it will remain in position to

be accurately relaid following the application of the adhesive.

5.3.3

Apply

the M-Bond 610 adhesive with a cap brush over

the gage surface to form a thin uniform coating. Repeat the

application technique to the specimen gage area. Do not

allow adhesive to come in contact with the tape adhesive.

5.3.4

Air

dry the assemblies for 30 to 40 minutes at 24 °C ±

2 °C [75 °F ± 4 °F] and 40 to 55% relative humidity.

IPC-TM-650

Number

2.4.41.2

Subject

Coefficient

of Thermal Expansion—Strain Gage Method

Date

05/04

Revision

age2of4

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