Office of Scien 4 Public^

Fill COP i

NATIONAL BUREAU OF STANDARDS REPORT

4283

CHARACTERIZATION OF METAL- INSULATOR

LAMINATES

by

D, S. Hoynes

Progress Report

to

Navy Bureau of Ships

Period of January 1955 through December 1955

<NBSp>

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

U. S. DEPARTMENT OF COMMERCE

Sinclair Weeks, Secretary

NATIONAL BUREAU OF STANDARDS

A. V. Astin, Director THE NATIONAL BUREAU OF STANDARDS

The scope of activities of the National Bureau of Standards at its headquarters in Washington,

D. C., and its major field laboratories in Boulder, Colorado, is suggested in the following listing of

the divisions and sections engaged in technical work. In general, each section carries out specialized

research, development, and engineering in the field indicated by its title. A brief description of

the activities, and of the resultant reports and publications, appears on the inside back cover of

this report.

W ASHINGTON, D. C.

Electricity and Electronics. Resistance and • Reactance. Electron Tubes. Electrical Instru- ments. Magnetic Measurements. Process Technology. Engineering Electronics. Electronic

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'
NATIONAL BUREAU OF STANDARDS REPORT

MBS PROJECT MBS REPORT

106 -20-5540 May 1, 1956 4283

CHARACTERIZATION OF METAL- INSULATOR

LAMINATES

by

D. S. Hoynes

Engineering Electronics Section

Electricity and Electronics Division

Progress Report

to

Navy Bureau of Ships

Period of January 1955 through December 1955

NPO Order 10756/54

Ships and Facilities

Navy 1956

Account 46391

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

..Ufaati.., r, Approved for public release by the

Bnien perfflitt'en i director of the National Institute of

25, d. c. Such p« Standards and Technology (NIST)

oiiy prepared if i on October 9, 2015

in par t, is prohibited andards, Washington

port has been specifie po r

t for its own use.

FOREWORD

This report covers work done under a program sponsored

by the Bureau of Ships, Department of the Navy. The program

is under the administration of the Electricity and Electronics

Division and the technical supervision of the Engineering

Electronics Section. The project was established for the

purpose of determining physical and electrical properties

suitable for the evaluation of metal-insulator laminates for

use in printed circuit applications. A series of tests have

been devised which may serve in part as the basis for a

specification on printed circuit laminates.

This report , covering the period of January 1955 through

December 1955, is a continuation of the work described in

National Bureau of Standards Progress ReporiT^NcK 3392^

"Characterization of Metal-Insulator Laminate s , " da

t

e_d—

June 30, 1954.

Gustave Shapiro, Acting Chief

Engineering Electronics Section

Francis B. Silsbee, Chief

Electricity and Electronics

Division

ii

ACKNOWLEDGMENT

The author wishes to express his appreciation to the

following NBS Staff members for their participation in

this project : Irvin Philmon in the preparation of test

samples and over-all assistance in the test program;

Robert B. Reams, Jr. for his assistance in obtaining

measurements and data on the electrical resistivity of

the coated samples; Anthony P. Schmid for his assistance

in the work carried out in determining the current carrying capacity of etched conductors; Jay C. Brown for his

assistance in obtaining the data for the dielectric

properties of the material presented; and Dr. Arnold H.

Scott of the Resistance and Reactance Section of the

Electricity and Electronics Division under whose general

supervision and guidance the dielectric measurements were

made

iii

TABLE OF CONTENTS

Page

FOREWORD i i

ACKNOWLEDGMENT iii

INTRODUCTION 1

1. CURRENT-CARRYING CAPACITY 2

1.1 Resistivity Values 2

1.2 Temperature Rise Measurements 7

1.3 Design Guide and Chart 23

2. ELECTRICAL RE SI STANCE—COATED SAMPLES .... 28

2.1 Surface Resistivity 29

2.2 Volume Resistivity 34

2.3 General Observations 35

3. DIELECTRIC PROPERTIES 99

3.1 Dissipation Factor 101

3.2 Dielectric Constant 103

iv

CHARACTERIZATION OF METAL- INSULATOR LAMINATES

by

D. S. Hoynes

INTRODUCTION

. This report deals with tests conducted on the currentcarrying capacity of etched copper conductors, resistance

measurements on samples having a variety of protective

coatings, and dielectric properties of a number of metalclad laminates at various temperatures. For background

information on the preparation of test samples for

resistance measurements, the reader is referred to National

Bureau of Standards Report No. 3392, "Characterization of

Metal-Insulator Laminates," dated June 30, 1954.

A chart showing the relationship between temperature

rise, conductor width, cross-sectional area, and copper

thickness has been included as a design aid for determining

conductor sizes in printed circuit application utilizing

etched conductors.

1
-
1. CURRENT-CARRYING CAPACITY

t The current-carrying capacity, or the ability of an

etched or printed conductor to carry an adequate current

safely for a particular application, is considered to be

an important property especially now that printed circuit

techniques are gaining widespread acceptance for military

and industrial applications. It is generally recognized

that the average ’’printed” conductor is capable of carrying more current than is usually encountered in an

electronic design application. There are a sufficient

number of applications , however, where it is necessary to

know with some degree of certainty whether a particular

conductor can fulfill its requirements. Because information of this type has not been generally available, it

was deemed sufficiently important to investigate not only

the current-carrying capacity of etched-type conductors

bonded to different base materials, but also their general

behavior patterns under different conditions of use.

1 . 1 Resistivity Values

Initial measurements, made principally with thermocouples, showed a general behavior pattern of temperaturerise for a given current flow with respect to the crosssectional area of the copper. The accuracy of the

thermocouple method, however, is generally limited by the

2

if

accuracy of the conductors’ dimensional measurements, which

are somewhat difficult to ascertain even with precision

instruments

It was found more expedient to derive the crosssectional area from the resistivity of the copper and the

temperature-rise as computed by using the temperature

coefficient of resistivity and values of resistance

obtained by the IR drop method.

In order to arrive at a reasonable value of resistivity

for the copper, oven measurements were made on eight samples

of laminates over a temperature range of 25.6°C to 125. 2°C

and the temperature coefficient of resistivity established

* by :

0tl Rt a

(t2 “ t’l)

and adjusted to a desired temperature by:

a t

1

1

+ (t - ti)

Values of a at 25.6°C for the eight samples varied

from .00380 to .00387, as shown in Table I (p..4), with an

average value of .003844. When adjusted, the average values

* National Bureau of Standards Circular No. 31 • • i

3

TABLE I VALUES OF FOR VARIOUS COPPER-CLAD LAMINATES

BASED ON RESISTANCE MEASUREMENTS

MATERIAL

AND CU.

THICKNESS

TEMP.

“C

I . R.

\pROP

R

(OHMS)

OC

25.6

4-10 Epoxy

.0027”

25.6 /

125.2 ( .100

.100

. q'o4033

t/005573

.04033

.05573 .00383

2-7 XXXP

.0027"

25.6

125.2

>400

.100

.001651

.002288

.01651

.02288 .00387

5-26 N-I

.00135"

25.6

125.2

.100

.100

.005227

.007238

.05227

.07238 .00386

6-16 G-5

.00135”

25.6

125.2

.100

.100

.004346

.006010

.04346

.06010 .00384

2-7 XXXP

.00135"

25.6

125.2

.100

.100

.003370

.004663

.03370

.04663 .00385

5-7 XXXP

.00135"

25.6

125.2

.100

.100

.004057

.005608

.04057

.05608 .00384

4-7 XXXP

.00135"

25.6

125.2

.100

.100

.003465

.004797

.03465

.04797 .00386

5-7 XXXP

.0027”

25.6

125.2

.100

.100

.002175

.002999

.02175

.02999 .00380

for a are .00385 at 25°C, and .00393 at 20°C, which values

correspond to those given in the tables (NBS Circular No. 31)

for 100% conductivity copper which at 20°C has a volume

resistivity equal to 1.7241 ohra-cm. From the value of a

at 20°C, and the established volume resistivity at the same

temperature, the volume resistivity at any temperature may

be calculated by

/°t = /°ti (1 + at]_ [t - ti])

This results in an average resistivity value of

1.76 x 10"® ohm-cm.at 25°C for the eight samples of

copper, a value somewhat higher than that normally

associated with electrolytic copper. Actual comparisons

were made of cross sections of a number of conductors. In

the comparisons, a combination of precise optical and

physical measurements were made, an average being used of

five points of measurement in thickness and width per

conductor sample. The results of this method showed good

agreement with computed cross sections derived from the IR

drop method and may be seen in Table II, (p . 6). The

results of these measurements indicate, however, that the

effective resistivity of this copper is slightly higher

than the value of resistivity obtained from a alone. This

is probably due to a combination of several factors as

follows : a. Slight irregularities in the conductor pattern

5

TABLE II CROSS-SECTIONAL AREAS AND RESISTIVITY

VALUES FOR VARIOUS ETCHED COPPER CONDUCTORS

MATERIAL

AVERAGE

THICKNESS

(inches)

AVERAGE

WIDTH

(inches)

AVERAGE

CROSS-SEC.

(sq. mils.)

RES.

25 °C

(ohms)

P 25*

(xlO"6

)

COMPUTED

CROSS-SEC. ** (sq. mils.)

2-7 A .00221 .2030 448.6 .00456 1.73 466

2-7 B .00232 .1243 288.4 .07330 1.79 290

4-7 A .00120 .2035 244.2 .00848 1.75 251

4-7 B .00125 .1245 155.6 .01368 1.80 155

4-7 C .00123 .0599 73.7 .02936 1.83 72

5-10 A .00135 .1993 269.1 .00795 1.81 267

5-10 B .00132 .1245 164.3 .01385 1.79 165

5-10 D .00135 .0378 37.5 .05778 1.83 37

5-10 E .00137 .0120 16.4 .13230 1.84 16

5-7 C .00045 .0598 26.9 .08151 1,86 26

5-7 D .00042 .0307 12.9 .16330 1.78 13

5-7 E .00042 .0145 6.1 .35680 1.84 6

*Based on dimensional measurements

•Based on resistance measurements and /o = 1.80 x 10"® ohm-cm.

6

caused by the etching procedure.

b. Somewhat lower than normal density of the copper

due to manufacturing procedures for thin foils.

c. Variations in the copper due to depressions,

pinholes, and variable thickness.

shown in Table II (p . 6), is 1 . 80 x 10“® ohm-cm at 25°C, and

for the purpose of this report, this value has been used in

all computations for determining the cross-sectional areas

of conductors under test,

j Temperature rises in the conductors (except for the purpose of checks where thermocouples

were used) were computed using the 025 value of .00385 as

described earlier (pp . 3-4), and may be obtained by:

Ro - Hi AT = —- — a Rl v - where = Resistance of the conductor at the lpw

temperature

R2 = Resistance of the conductor at the

elevated temperature.

1.2 Temperature Rise Measurements

In order to obtain a general behavior pattern for

conductors of the etched type as regards current-carrying

capaci ty, a J^ar^e^number of measurements were made on

different lengths of conductors on a variety of materials

(p . 8). The results of these measurements are shown in the

current vs. cross section curves in Figs. 1-7 (pp . 9-15).

The average resistivity value for the 12 samples, as

and it conditions of use, as shown in Table III

7

TABLE HI

7

MATERIALS, PROCESSING, ANO CONDITIONS USED IN DETERMINING THE TEMPERATURE

RISES OF VARIOUS ETCHED CONDUCTORS (SEE FIGURES 1-7)

CODE

MATERIAL ANl/cORJX

THICKNESS (TN)

'COPPER ) THICKNESS (IN) ADDITIONAL PROCESSING

TEST

TEMP °C

TEST

METHOD**

A 5-7 XXXP 1/16 . 0027KX None /50A IR It TC

B 2-7 XXXP 1/16 . 004K None /

- 50 IR It TC

C 4-7 XXXP 1/16 . 00135K None Iso IR D 4-10 Epoxy 1/16 . 00135K None w IR It TC

E 5-7 XXXP 1/16 . 0027K None /60~"\

IR L TC

F 2-7 XXXP 1/16 . 0027K None / 60 IR G 4-7 XXXP 1/16 . 0013 5KX None V.60 J IR

H 5-7 XXXP 1/16 . 0027KK None /25 \ IR

I 2-7 XXXP 1/16 . 004K None / 25 \ IR k TC

J 5-10 Epoxy 1/8 . 0027K None ! 25 \ IR K 4-7 XXXP 1/16 . 00135KK None 1 25 IR

L 5-10 Epoxy 1/32 . 00135K None 25 i IR . M 4-10 Epoxy 1/16 . 00135K None 25 TC

N 2-7 XXXP 1/16 . 00067K None l 25 IR 0 5-10 Epoxy 1/32 . 00135KK None V 25 / IR

P 4-10 Epoxy 1/16 . 00135K

Coated with .005”

Epoxy Resin 25 IR

Q 2-7 XXXP 1/16 . Q0135K

Coated with .002"

Insulating Varnish 25 . _ IR

R 5-7 XXXP 1/16 . 0027K

Coated with .001"

. Silicone Spray 25 IR

S 4-7 XXXP 1/16 . 001 35K

Coated with .003"

Insulating Varnish 25 IR T 2-7 XXXP 1/16 . 0027K

Coated with .006"

Silicone Resin 25 IR

U 2-7 XXXP 1/16 . 00135K

Dip Soldered

10 sec. 250°C 25 IR

V 2-7 XXXP 1/16 . 0027K

Dip Soldered

10 sec. 250 °C 25 IR w 10-7 XXXP 1/16 . 0013 5K

Dip Soldered

10 sec. 250°C 25 IR

X 5-10 Epoxy 1/8 . 0027K

Dip Sold, and Coated

with .005" Epoxy Res. 25 IR & TC

Y 4-7 XXXP 1/16 . 00135K

Dip Soldered

10 sec. 250 °C 25 IR

z 2-7 XXXP 1/16 .002 7

Dip Soldered

10 sec . 250 °C 25 TC

1 5-7 XXXP 0013 5 Core Removed

Conductor in Free Air 25 IR

2 6-16 G-5 .00135

Core Removed

Conductor in Free Air 25 IR

3 2-7 XXXP .00135

Core Removed

Conductor in Free Air 25 IR

4 5-7 XXXP .0027

Core Removed

Conductor in Free Air 25 IR

5 2-7 XXXP .0027

Core Removed

Conductor in Free Air 25 IR

6 2-7 XXXP .0027

Core Removed

Conductor in Free Air 25 IR

! 7 4-10 Epoxy .00135

Core Removed

Conductor in Free Air 25 IR

*K denotes single-clad, and KK denotes double clad material.

**IR = IR Drop Measurement, TC = Thermocouple Measurement.

8

FIG. I

CURRENT VS. CROSS SECTION

FOR 10* C. TEMP RISE

OF ETCHED COPPER CONDUCTORS

k

'L»

9

CURRENT

IN

AMPERES

CURRENT VS. CROSS SECTION

FOR 20* C. TEMP RISE

OF ETCHED COPPER CONDUCTORS

-f 5

o O

r 1 3

• y/W

< ^ii

y— >

s

* ^ * v"' ^•x

T

•

L

x*'*

.. K

o /»> x ^

‘ .•3' //L s'

i-' ^*1 T

I' y

, YY' '>y

4 It 96 €4 100 144 106 U« 924 400 464 576 67« CROSS SECTION IN SO. MILS

NOTE: SEE TABLE IE, PAGE-8 FOR IDENTIFICATION OF SYMBOLS RELATING

TO TESTING METHOD, TEST CONDITIONS, MATERIALS AND PROCESSING

10

CURRENT

IN

AMPERES

CURRENT VS. CROSS SECTION

FOR 30* C. TEMP RISE

OF ETCHED COPPER CONDUCTORS

vA n 'SW^Sk.

s' s' ~pSJ IT

s' *

*

JV >i\'

T

•

“i

s*

**

*

s'

lf

s'

*

* 6

r

" A ^

s'

V , /1 s'

s x

' /3- ' .S' « s

0V / v' s

Q'

X

*

K S S* S

's'

4 16 96 64 100 144 1 96 EM 924 400 404 376 676 CROSS SECTION IN SQ. MILS

NOTE-’ SEE TABLE HI, PAGE-8 FOR IDENTIFICATION OF SYMBOLS RELATING

TO TESTING METHOD, TEST CONDITIONS, MATERIALS AND PROCESSING

CURRENT

IN

AMPERES

FIG. 4

CURRENT VS. CROSS SECTION

FOR 45 * C. TEMP. RISE

OF ETCHED COPPER CONDUCTORS

sS

r B 15 S

S’

s

s' Jr

1

* a

s' s'

S’ SS

C *

s'

5s'

l jS '

0S .s'

S'

^s I

>*

- 9'

c # , s'*

4

sf Vs ' :>

.s' >

8

"

**

- s'

s'"

. . sS‘‘ S 4

+

**

i

. x

KL s'^

,v . s 77/ * * Ax /

'Ay

w

//

4 16 36 64 IOO 144 l»6 256 324 400 464 576 676 CROSS SECTION IN SO. MILS

NOTE: SEE TABLE HI, PAGE -8 FOR IDENTIFICATION OF SYM80LS RELATING

TO TESTING METHOD, TEST CONDITIONS, MATERIALS AND PROCESSING

12

CURRENT

IN

AMPERES

FIG. 5

CURRENT VS. CROSS SECTION

FOR 60* C. TEMP RISE

OF ETCHED COPPER CONDUCTORS

**

^4

\

B

_ S'

S'

S’ S' •

• J

* S*

V

yz' / s

s

'

,S ’ *

0/ lx

CO Js' SS X

**

’ %<*

IJ

0 y c

o

1 k r“ m x

s’ ' T »

L .y^ * • '> B / 8 / s « >

, /

..S’ s

1 */ '» .si

0 0

* sv;:

# S'

» V 0 / / ‘ 0

"

JL '/s

///.''

_Aw

4 16 36 64 100 144 196 ES6 324 400 464 376 676 CROSS SECTION IN SQ. MILS

NOTE: SEE TABLE HI, PAGE-8 FOR IDENTIFICATION OF SYMBOLS RELATING

TO TESTING METHOD, TEST CONDITIONS, MATERIALS AND PROCESSING

13

CURRENT

IN

AMPERES

FIG. 6

CURRENT VS. CROSS SECTION

FOR 75* C. TEMP RISE

OF ETCHED COPPER CONDUCTORS

S'

D Bi D

S' S

s'

''

G

o •//-" s' .s'

s

Q

C S S /

X

• r

1

e /

s

S' 0

s' ' T W • s'

L T

"

s

.x' «

0

G ^>

c <} IIP"/ /

0

I Vs'.' ;x»t

o/S /

y

-8

/

VS

T '

4 16 56 64 100 144 196 856 524 400 484 576 676 CROSS SECTION IN SQ. MILS

NOTE: SEE TABLE HI, PAGE-8 FOR IDENTIFICATION OF SYMBOLS RELATING

TO TESTING METHOD, TEST CONDITIONS, MATERIALS AND PROCESSING

14

V

CURRENT

IN

AMPERES

FIG . 7

CURRENT VS. CROSS SECTION

FOR IOO* C. TEMP RISE

OF ETCHED COPPER CONDUCTORS

NOTE: SEE TABLE HI, PAGE-8 FOR IDENTIFICATION OF SYMBOLS RELATING

TO TESTING METHOD, TEST CONDITIONS, MATERIALS AND PROCESSING

15

*

The points on the cur ves, which are presented as

symbols, and which from Table III may be identified as to

the conditions of test, show the current required to raise

each conductor a given temperature above ambient/' as

established from individual temperature-current interpolation curves for each conductor . / The individual

interpolation curves were obtained by making IR drop

measurements at several different current levels for each

of the conductors and plotting the calculated temperature

rise for each par^cular current level. These

interpolation curves were then used as a means of finding

the currents required to cause the specific temperature

rises, as shown in Fi gures 1 through 7. / This method was

used because of the obvious difficulties that would have

ensued if an attempt had been made to elevate each

conductor to a predetermined temperature rise by varying

the current. r

All measurements were made with calibrated instruments

accurate to within 1/2 of 1 percent , or better. The

temperature rise measurements were made with sufficie nt time

16

allowed for the samples to reach equilibrium, and current

values for establishing reference r esistances and crosssectional areas were kept at the lowest practicable level

for the particular conductor under t est

As an additional

f check, all samples were measured with current flow in each

direction, and the average of the two measurements for each <

1 current level was used in determining the interpolation

curves on which Figures 1 through 7 are based .

' With —

allowances for variations in resistivity and measurement

procedures, the points as presented in the current vs.

of Figures 1 through 7 are considered

In each of the figures (1-7) the solid line represents

an average for those samples in which there was no processing other than the forming of the conductor pattern by

the usual photo-etching technique. The adjacent line

represents an approximate level for those samples additionally processed with protective coatings, as identified

in Table III (p . 8). The next line shows an approximation

for those samples which were dip-soldered. The lowest line

indicates the average levels for various conductors which

had been completely removed or stripped from their core

materials and tested in free air.

The recurrence of the same identifying symbol at several

points in the figures (1-7) indicates that measurements were

¥

cross section curves

["to be within~~±3 °C

,

17

made on more than one conductor and at the cross section

indicated by the location of the symbol and under the

conditions listed in Table III.

From the curves (Figures 1-7) , it may easily be seen

that the cross-sectional area of a conductor is a dominant

factor in its ability to carry a given current for a

particular temperature rise, especially for the usual

copper thicknesses of- .00135 (1 oz.) and .0027 inch (2 oz.).

Heavier coppers (.004 in.), as might be expected, appear

capable of carrying somewhat less current , and thinner

coppers (,00067 in.) somewhat higher current for a given

ary importance^ is the manufacture f core material . A specimen with thinner core material of about 1/32 inch

thickness (L) showed a

xnot iceable rejducLtl

o

n in currentcarrying capacity as compared with heavier cores. The same

type of material showed a higher current-carrying capacity

when a solid copper backing (0) was used. For the usual

core thickness of 1/16 inch (or higher) , only small difference could be noticed between those panels having a copper

backing (indicated by KK in Table III), and those without,

(indicated by K) , Variations in ambient temperature are

also shown to have little effect on the temperature rise

above ambient due to a given current.

Significant reduction in current-carrying capacity of

cross-sectional area. factor appearing to be of second18

about 15 to 20% was noted for those samples in which coatings

were used, indicating a reduced ability of the samples to

dissipate the heat generated in the copper conductor.

Additional reductions in current-carrying capacity in

varying degrees up to about 30% were noted in most dip-soldered

samples. A comparison of a number of conductor samples showing resistances and temperature rises at various current

levels before and after dip-soldering is given in Table IV

(p . 20). From this table it will be noted that in most

instances the resistance of the particular conductor was

actually lowered by dip-soldering. This should be considered

reasonable since the addition of the solder layer would be

expected to add something to the conductance of the whole, as

well as to the total cross-sectional area of the conductor.

Separate oven measurements were made to determine the

values for a of the dip-soldered conductors, which values are

shown in the last column in Table IV (p. 20). It will be

noted that the temperature coefficient of resistivity has

been lowered from the .00385 value for the average copper

conductor, as determined earlier (page 3), to an average value

of about .00310 for the dip-soldered samples. This indicates

the possibility of an alloying effect between the copper and

the solder coating, or at the least, a higher value of resistivity for the combination conductor. For obvious reasons,

however, no attempt has been made to determine the degree of

• 19

TABLE IV

COMPARISON OF CONDUCTORS BEFORE AND AFTER DIP-SOLDERING

MATERIAL TEMP. BEFORE DIP-SOLDIftING AFTER DIP-SOLDET ING AND CROSSSEC . AREA °C I RESISTANCE I2R I RESISTANCE I 2 R a 25*

4-7 XXXP 25 .5 .009222 .5 .009233

230 98 18 .011814 5.8 15 .011440 2.6 .00327

2-7 XXXP 25 .5 .011332 .5 .010813

188 70 13 .013295 2.2 10 .012345 1.2 .00315

10-7 XXXP 25 .5 .008982 .5 .008808

237 55 13 .010019 1.7 10 .009632 0.9 .00312

2-7 XXXP 25 .5 .007158 .5 .006824

297 92 21 .009004 3.9 15 .008253 1.8 .00312

4-7 XXXP 25 .5 .013112 .5 .011689

182 98 14 .016797 3.2 12 .014283 2.1 .00304

5-10 EPOXY 25 .5 .006920 .5 .006744

307 58 16 .007799 1.9 15 .007400 1.6 .00292

*Based on resistance measurements at 25 s and 104. 5°C

20

9

each of these possibilities, particularly since the primary

cause of the reduced current-carrying capacity of a dipsoldered conductor appears to be the result of a partial loss

of bond or a change in the heat transfer character istics of

the adhesive interface between the copper and the core material.

From the tabulations in Table IV, it will be noted in

each case that for the dip-soldered conductors less power was

actually required to cause a given rise in their temperature

than was required for the unsoldered conductors. In addition,

the variations that occurred were over a considerable range,

as indicated on the curves of Figures 1-7, and were generally

of a greater magnitude than were the coated samples. For

these reasons, it seems evident that the variations were due

to a reduction of heat transfer into the panel, particularly

since it is unlikely that a change in the conductor’s radiating ability due to a metal solder coating could have as much

effect on the sample as that shown or exceed the effect noted

for the coated samples. This supposition is strengthened in

the instance of the epoxy base sample (identified by the

symbol X), in which, it may be noted, deviation from the normal

curve was small as compared with other dip-soldered samples,

thereby indicating that the dip-soldering process had less

effect on the bond of this material than on the XXXP samples.

This is particularly evident inasmuch as the sample in

question had a .005 inch epoxy resin coating, which under

21

normal conditions would have caused an even greater reduction

in current-carrying capacity than that recorded. If the

coating had not been present, the sample would in all likelihood have been capable of carrying more current in the dipsoldered condition since the resistance of the sample was

actually lowered.

The results of measurements on a number of samples of

s conductors which had been physically stripped from the core

material may be noted from the curves (Figures 1-7) . Cross

section measurements are based on measurements made after

stripping, and temperature rises are based on IR measurements and a temperature coefficient of resistivity of .00385.

From the curves it may be seen that none of the other conductors approached the reduced current values for a given

temperature rise regardless of the type of processing. It

would seem safe, therefore, to assume that even with the

poorest bond available, a conductor would never exceed the

temperature rise above that indicated for the stripped conductors, except perhaps under very restricted conditions.

With time permitting, additional measurements will be

made on a greater variety of materials in order to determine

with more certainty whether the effects noted extend to most

laminates or whether they are restricted to just a few materials under certain conditions of processing. The materials

under test, it will be noted, were all dip-soldered under the

22

-v

same time-temperature conditions of 10 seconds at 250°C, which

in some applications might be considered excessive. If further

work on this subject is felt to be warranted, the possibility

of developing a test in which the temperature rise of a given

conductor may be used as a function of the ’’quality” or

effectiveness of a bond should not be overlooked.

1 . 3 Design Guide and Chart

Although the preceding work cannot be considered c omplete,

the information on hand is considered adequate for providing

the telr^t i^TdesTgn^guide and chart presented on pages 25 and

26. ^ThTs^design chart shows the basic relationship of current

vs. temperature rise for various cross sections of copper for

aver age usage

The chart may also be used for the determination of

temperature rises for other than single conductor applications,

such as parall el conductors and coils. Tests on a limited

number of samples show that the temperature rise of closely

spaced parallel conductors (such as filament lines) may be

e s t imaged by us i ng—an-equivaienteross sec t ion and current

condition based on the summation of the cross sections and

currents involved, and interpolating directly from the chart.

The estimated temperature rise thus obtained will be somewhat

on the high side, since it has been obtained by assuming the

least favorable condition possible, i.e„, a condition where the

conductors are so close together that they may be considered

23

as a single conductor carrying the sum total of the currents.

For practical purposes, however, this estimate is considered

adequate for most applications, and the addition of a correction factor to provide adjustments dependent on the spacing

between conductors would be of little value.

In the case of coils, estimates become somewhat more

difficult owing to possible variations in conductor sizes,

configurations, panel areas, and heat transfer from one part

of the coil to another. Thermocouple measurements on a number

of coils ranging in size from 0.350 inch to 1.5 inch diameter

showed that safe estimates in temperature rise of the hottest

portions may be made from the chart (Figure 8, p. 26) by

utilization of equivalent cross sections and currents based on

a factor of 2n, where n is equal to the number of turns in the

coil. Here again, while the temperature rise estimates are

generally on the high side, it is felt that little would be

gained by introduction of correction factors of a complicated

nature. This is considered particularly true in view of the

inherent difficulties in obtaining accurate cross-sectional

estimates from measurements due to variations in copper thickness, undercutting during etching , variations in the pattern, etc.

i An additional chart (Figure 9, p. 27), showing resistance

per linear inch vs. cross-sectional area of etched copper

conductors, has been included for convenience in the estimation

of conductor sizes in applications where the IR drop in a given

conductor would be the limiting factor in the conductor’s use

rather than its temperature rise.

* ^24
.
DESIGN GUIDE

The design chart on the following page (Fig. 8) has been prepared as an aid

in estimating temperature rises (above ambient) vs. current for various cross- sectional areas, of etched copper conductors. It is intended for use primarily

with XXXP and Epoxy-glass materials* of 1/16 to 1/8" thickness and copper

thickness of .00135" (1 oz), and .0027" (2 oz) . It is assumed that normal design

conditions prevail where the conductor surface area is relatively small compared

to the adjacent free panel area. The curves as presented include a nominal 10%

derating (on a current basis) to allow for normal variations in etching techniques,

copper thickness, and-^onductojr^width estimates.

Additional derating** of 15% (current-wise) is suggested under the following

conditions

1. If the panel is to be. coated.,

2. For panel thickness of 1/32 inch.,

3. For conductor thickness of .004" (3 oz) . A derating of 30% is suggested for panels that are to be dip-soldered.

For general use the permissible temperature rise is defined as the difference

between the maximum safe operating temperature of the laminate (assumed to be

105°C for XXXP and Epoxy base materials), and the maximum ambient temperature in

the location where the panel will be used.

For single conductor applications the chart may now be used directly for

determining conductor widths, conductor thickness, cross-sectional area and current

carrying capacity for various temperature rises.

For groups of similar parallel conductors, if closely spaced, the temperature

rise may be found by using an equivalent cross-section and an equivalent current.

The equivalent cross-section is equal to the sum of the cross-sections of the

parallel conductors, and the equivalent current is the sum of the currents in the

conductors

For applications where etched coils are to be used, the maximum temperature

rises may be obtained by using aq equivalent cross-section equal to 2n times the

cross-section of the conductor, and an equivalent current equal to 2n times the

current in the coil, where n is equal to the number of turns.

A conversion chart (Fig. 9), showing resistance (per linear inch) vs. cross- section for etched conductors has been Included for use in those applications

where the IR drop in a conductor may be the primary consideration as opposed to

temperature rise.

*The measurements on which this chart has been based have been made on XXXP and

Epoxy laminates. It may be assumed, however, that other types of laminates will

behave in the same general manner providing they have equivalent bonds.

**The suggested derating of the permissible current is based on the assumption that

maximum usage of the material is desired. For general design purposes, however,

the user may find it more expedient to set the derating figure at a uniform 50%

value in order to take care of all possible considerations, which according to

data would even include complete delamination of the conductor from the panel.

v

25

CONDUCTOR

WIDTH

IN

INCHES

FIG. 8

DESIGN CHART

( TENTATIVE ) FOR USE IN DETERMINING CURRENT CARRYING CAPACITY AND SIZES OF ETCHED

COPPER CONDUCTORS FOR VARIOUS TEMPERATURE RISES ABOVE AMBIENT.

(NOTE: SEE DESIGN GUIDE ON PRECEDING PAGE FOR USE OF THIS CHART ).

26

it

RESISTANCE

PER

INCH

OHMS

CONVERSION CHART

RESISTANCE VS CROSS SECTION

FOR

ETCHED COPPER CONDUCTORS

27

if

2 . ELECTRICAL RESISTANCE - COATED SAMPLES

As a continuation of measurements described earlier in

National Bureau of Standards Report No. 3392, new groups of

test samples were subjected to a temperature of 70°C and

95% R.H. for a period of 2000 hours in order to determine the

effects of various protective coatings on the electrical

resistance characteristics of metal-clad laminates. Seven

groups of XXXP laminates and one of the epoxy glass-mat type

were included in this test. Also, other materials, a nylon

(N-l) laminate and a styrene co-polymer (both without coatings) , were included to determine their basic behavior

patterns

The coatings used and their approximate thicknesses are

listed below.

1. Modified epoxy .005”, Mfr. No. 1 . (Designated as

Epoxy No . 1 .

)

2. Epoxy resin, .005”, Mfr. No. 2. (Designated as

Epoxy No . 2 .

)

3. Microwax, .004”.

4. Insulating varnish, .003”. (Clear, air drying type.)

5. Silicone resin, .006”.

6 . Silicone fluid (125 CS) , 1-1/2% solution CCI 4

. The same procedure as that outlined in the earlier report

was used to prepare the test samples, all of which were of the

three-terminal circular type having gap widths of 1 and 2 mm.

28

2 . 1 Surface Resistivity

Surface resistivity is given in megohms per ’’square”

and is computed on the basis of

/^s = E_ Rs

g

where Rs = surface resistance as measured

g = distance between electrodes

P = effective perimeter of the guarded electrode.

The curves of Figures 13 to 61 (pp . 40 to 88) show the

surface resistivity of the materials tested and have been

arranged to show their relationship to the uncoated samples

included as controls. The curves for the controls for a

particular group have been repeated in each set of curves

for the coated samples (Figures 13-59, pp . 40-86) so that

comparisons may more easily be made.

Bar graphs, Figures 10, 11, and 12 (pp . 37-39), show

the extremes in surface resistivity recorded for the samples

and their various coatings during the 2000 hour test. It

will be easily seen from these graphs that the variation in

resistivity for the coated samples is generally much higher

than for the control samples.

From the corresponding curves (Figures 13 to 61,

pp. 40 to 88), it may be seen that the variation between

dip-soldered samples and nondip-soldered samples is

relatively low. Although no set pattern has been established that could not be ascribed to normal variations in

29

V

the samples, a slight trend toward higher resistivities may

be detected for the dip-soldered samples on an over-all

basis. This agrees substantially with previous results, and

may possibly be due to a slight loss of bond between the

copper and the core material. For purposes of resistivity

measurements, however, it can only be concluded that dipsoldering has no substantial effect on the surface resistivity of these materials.

A review of the present surface resistivity measurements

and those reported previously shows excellent agreement on

an over-all basis, with an average surface resistivity of 1C)3

f

< megohms or higher for most of the XXXP control samples.

Although different lots of materials were used in the present

tests than in the earlier ones, a comparison of the test

results shows substantial agreement for the individual manufacturers.

The results of the test on the epoxy-glass base laminate

(5-10) were somewhat lower than had been expected for

materials of this type (Figures 54 to 59, pp . 81 to 86).

Although the resistivity was relatively high (10^ megohms per

square) at the initial portion of the test, the value dropped

rather rapidly for the first 1000 hours to an average value

of about 3 x 10^ megohms per square , which is somewhat lower

than the average for XXXP materials under the same test conditions. The probable reason for this lower average was the

30

formation of corrosion along the edges of the electrodes of

the test pattern. The formation of corrosion', in all likelihood, was also the reason for the relatively high number of

complete electrical breakdowns in this group. Although these

particular samples are the only ones which have thus far

exhibited the formation of corrosion along the electrode edges

in any of the tests conducted in this laboratory, it cannot

be assumed , on the basis of a single test , that this is

characteristic of the material, particularly since the

material in question is of relatively early vintage. Other

samples have been obtained from several sources and additional tests will be made, time permitting. It was interesting

to note that none of the coatings used on this material

entirely prevented the formation of corrosion. Substantial

reduction of corrosion formation was observed, however, on

the coated samples.

Of the additional samples included in the test, the N-l

type (Figure 60, p. 87) was characterized by exceptional

uniformity throughout the entire test period. The styrene

co-polymer base material (Figure 61, p. 88) was, on the* other

hand, characterized by erratic behavior, which made readings

difficult to obtain.

In a comparison of the curves for the coated samples with

those for the controls, little or no improvement is to be

31

seen in most instances for the six coating materials.

Considerable variation in the resultant surface resistance

over and above that recorded for the control samples was the

rule rather than the exception. Additional variations may

be noted in the behavior of a particular coating material on

different core materials, with the exception of the coating

material described as Epoxy #1 , which had a uniformly adverse

effect on all of the samples on which it was used.

Epoxy #1

From the low values recorded for each group of samples,

it can only be concluded that this particular coating

material has a resistivity as low as, or lower than, that of

the materials under test.

Epoxy #2

The second coating material (Epoxy #2) had, in general,

very little over-all effect on those samples on which it was

used. The exception to this was the 4-7 XXXP group (Figure 25,

p. 52), which exhibited a relatively high resistivity in the

control samples.

Microwax

Samples coated with microwax showed a slight but fairly

consistent trend toward higher resistivity over the non-coated

or control samples. In only one case, again in group 4-7

(Figure 26, p. 53), was the resultant resistivity lower than

*4

32

that of the control samples, and then only after approximately

1000 hours of exposure. Significant improvement may be noted

in the 10-7 group (Figure 50, p.77), indicating that these

particular samples were somewhat sensitive to surface moisture

In the 5-10 epoxy group (Figure 57, p. 84), little or no

improvement can be seen up to the point where failure occurred

This is probably a reflection of the low resistivity of the

group caused by the formation of corrosion on the edges of

the electrodes.

Insulating Varnish

In those samples coated with insulating varnish little

over-all change is noticeable, most of the results running

approximately at par with the control samples. Some improvement is again seen in the 10-7 group (Figure 51, p. 78),

and somewhat lower resistivity is noticeable in the 4-7

group (Figure 27, p. 54).

Silicone Resin

The silicone resin coatings also exhibited no apparent

improvement on an over-all basis. The initial improvement

noticed in most cases can be attributed to the particular

curing procedure (150 hours at 100°C) used before testing.

After reaching a point of equilibrium (at approximately

1000 hours) these coatings behaved in a manner similar to

the Epoxy #2 and the insulating varnish coatings, with

little or no improvement to be seen.

33

Silicone Fluid Coatings

In this group of samples an initial improvement was

noticed, which in all likelihood was also caused by the

curing procedure used before testing. Silicone fluid, of

the type generally used for imparting moisture resistance,

was applied by immersing the samples for five minutes in a

1-1/2% solution of the fluid in CCI 4 , and subsequently

curing them for 150 hours at 100°C. The resultant thinfilm type of coating, after reaching equilibrium at about

1000 hours, also had little effect on the surface resistivity of the samples, with perhaps two exceptions. These

are the 6-7 group, (Figure 35, p. 62), in which the

resistivity was increased by approximately 2 decades, and

the 4-7 group (Figure 29, p. 56), upon which the coating

had the least adverse effect of the various coatings tried.

Although this type of coating could not be expected to give

the samples physical protection against surface contamination, the results are of sufficient interest to merit

further investigation with other fluids of the same type

and perhaps in combination with other coating materials.

2.2 Volume Resistivity

Volume resistivity is given in megohra-cm and is computed

as follows:

34

where A = effective area of the guarded electrode

t = average thickness of the specimen

Rv = volume resistance as measured

The effects of the coating materials on the volume

resistivity of the samples were generally so slight that no

advantage could be gained by presentation of the results

separately for each of the coated materials. Therefore,

curves for only uncoated samples included as controls are

presented, Figures 62 to 71 (pp . 89 to 98).

2 . 3 General Observations

1. None of the coatings tested had a marked uniform

beneficial effect on the surface resistivity of the samples

under test.

2. From the group to group variations observed, it

would appear that some improvement in resistivity might be

obtained if a particular coating is selected for a particular

base material. Although a coating might show an improvement

in one material , it should not be assumed , however , that the

improvement would necessarily extend to other materials,

even of the same type or grade.

3. A coating material may be used with advantage on

printed-circuit panels for the purpose of physically protecting the surfaces against corrosion, contamination during

35

handling, accumulation of dust, etc. In areas where low

leakage is required , however , it would seem advantageous to

rely primarily on a base material with a high basic

resistivity and a compatible coating, at least until such

time as a coating material has been developed that may be

relied upon to offer substantial improvement on a broad

basis, i.e., on a variety of base material types or at

least on a wide selection of materials in a given class.

(Text recommences on p. 99)

36

FIG. 10

SURFACE RESISTIVITY* OF

VARIOUS TYPES OF METAL-CLAD

LAMINATES USING DIFFERENT PROTECTIVE COATINGS

Megohms

per "square"

Control

Epoxy #1

Epoxy #2

Mlcrowax

QD Insulating Varnish

Silicone Resin

I 1 Silicone Fluid

37

FIG. 11

SURFACE RESISTIVITY* OF

VARIOUS TYPES OF METAL-CLAD

LAMINATES USING DIFFERENT PROTECTIVE COATINGS

Megohms

per "square"

^Extremes recorded for 2000 hr. period

Control

Epoxy #1

Epoxy #2

Microwax

fTTl Insulating Varnish

B Silicone Resin

Silicone Fluid

38

FIG. 12

SURFACE RESISTIVITY* OF

VARIOUS TYPES OF METAL-CLAD

LAMINATES USING DIFFERENT PROTECTIVE COATINGS

Megohms

per ’’square”

^Extremes recorded for 2000 hr. period

10-7 XXXP

*

5-10 Epoxy Glas^

1

ton i

I

©

CO

I co

Q) 4) c

Qi E»

U

>* g -P (X

CO o w O

Control

Epoxy #1

Epoxy #2

Microwax

H j Insulating Varnish

B Silicone Resin

Silicone Fluid

39

FIG. 13

SURFACE RESISTIVITY VS TIME

70 °C 95% R.H.

Megohms

per ’’square”

ICG?

1-7-129 Control (Dip soldered)

1-7-137 Control (Dip soldered)

1-7-133 Control (No preconditioning)

1-7-135 Coating: Epoxy #1

1-7-131 Coating: Epoxy #1 (Dip solder-ed)

40

FIG. 14

SURFACE RESISTIVITY VS TIME

70°C 95% R. H.

Megohms

per ’’square”

;0 5 XXXP

1-7-138 Coating: Epoxy #2 (Dip soldered)

1-7-126 Coating: Epoxy #2

41

FIG. 15

SURFACE RESISTIVITY VS TIME

70 °C 95% R.H.

Megohms

per "square"

I XXXP

1-7-130 Coating: Microwax

42

FIG. 16

SURFACE RESISTIVITY VS TIME

70 °C 95% R.H.

Megohms

per "square”

I0 5 XXXP

1-7-136 Coating: Insulating varnish (Dip soldered)

1-7-132 Coating: Insulating varnish

43

FIG. 17

SURFACE RESISTIVITY VS TIME

70 °C 95% R.H.

Megohms

per "square”

I0

5 XXXP

1-7-139 Coating: Silicone resin

1-7-127 Coating: Silicone resin (Dip soldered)

44

FIG. 18

SURFACE RESISTIVITY VS TIME

70°C 95% R.H.

Megohms

per "square”

10 5 XXXP

1-7-128 Coating: Silicone fluid

1-7-140 Coating: Silicone fluid (Dip soldered)

45

FIG. 19

SURFACE RESISTIVITY VS TIME

70°C 95% R.H.

Megohms

per ’’square"

10 6 XXXP

HOURS

2-7-041 Control (No preconditioning)

2-7-037 Control (Dip soldered)

2-7-045 Control (Dip soldered)

2-7-043 Coating: Epoxy #1

2-7-047 Coating: Epoxy #1 (Dip soldered)

FIG. 20

SURFACE RESISTIVITY VS TIME

70 °C 95% R.H.

Megohms

per ’’square”

I06 XXXP

2-7-042 Coating: Microwax (Dip soldered)

2-7-046 Coating: Microwax

47

FIG. 21

SURFACE RESISTIVITY VS TIME

70 °C 95% R.H.

Megohms

per "square”

10 6 XXXP

2-7-044 Coating: Insulating varnish (Dip soldered)

2-7-048 Coating: Insulating varnish (Dip soldered)

48

FIG. 22

SURFACE RESISTIVITY VS TIME

70°C 95% R.H.

Megohms

per "square"

I06 XXXP

8 —

6 —

4 —

2 —

.o5

8 —

6 —

4 —

2 —

104

\ NP D\\

V

D

8 —

6 —

4 —

2 —

I0

3

'Vw

\1 0 O

8 —

6 -

4 —

2 —

.o 2

\ ^

O

§ ff---.fi—-

\—2-7-039

2-7-035

0 500 1000 1500 2000

HOURS

2-7-039 Coating: Silicone resin

2-7-035 Coating: Silicone resin (Dip soldered)

49

FIG. 23

SURFACE RESISTIVITY VS TIME

70 °C 95% R.H.

Megohms

per ’’square”

l0 6 XXXP

2-7-036 Coating: Silicone fluid

2-7-040 Coating: Silicone fluid (Dip soldered)

50

FIG. 24

SURFACE RESISTIVITY VS TIME

70°C ‘95% R.H.

Megohms

per ’’square"

10 XXXP

4-7-112 Control (Dip soldered)

4-7-122 Coating: Epoxy #1

4-7-126 Coating: Epoxy #1 (Dip soldered)

4-7-120 Control (No preconditioning)

4-7-124 Control (Dip soldered)

51

FIG. 25

SURFACE RESISTIVITY VS TIME

70 °C 95% R.H.

Megohms

per "square"

I06 XXXP

4-7-117 Coating: Epoxy #2

4-7-113 Coating: Epoxy #2 (Dip soldered)

52

FIG. 26

SURFACE RESISTIVITY VS TIME

Megohms 95% R.K.

per "square"

I06

4-7-121 Coating:

4-7-125 Coating:

Microwax (Dip soldered) Microwax

53

FIG. 27

SURFACE RESISTIVITY VS TIME

Megohms 70 ° C 95% r.h.

per "square"

4-7-127 Coating:

4—7—123 Coating: lnsu^^

ng Varnish (Dip soldered) insulating varnish

54

FIG. 28

Megohms

per "square"

SURFACE RESISTIVITY VS TIME

70°C 95% R.H.

4-7-114 Coating: Silicone resin

55

FIG. 29

SURFACE RESISTIVITY VS TIME

70 °C 95% R.H.

Megohms

per "square"

l<fi XXXP

4-7-115 Coating: Silicone fluid (Dip soldered)

4-7-119 Coating: Silicone fluid

56

FIG. 30

SURFACE RESISTIVITY VS TIME

70 °C 95% R.H.

Megohms

per ’’square”

I06 XXXP

6-7-056 Coating: Epoxy #1

6-7-052 Coating: Epoxy #1 (Dip soldered)

57

FIG. 31

SURFACE RESISTIVITY VS TIME

Megohms

^ ^ R-H.

per ’’square"

10 6 XXXP

6-7-047 Coating: Epoxy #2

6-7-043 Coating: Epoxy #2 (Dip soldered)

58

FIG. 32

SURFACE RESISTIVITY VS TIME

70 °C 95% R.H.

Megohms

§

er Msquare lf XXXP

6-7-055 Coating: Microwax (Dip soldered)

6-7-051 Coating: Microwax

59

FIG. 33

SURFACE RESISTIVITY VS TIME

70 °C 95% R.H.

Megohms

per "square"

l 0

6 XXXP

6-7-057 Coating: Insulating varnish (Dip soldered)

6-7-053 Coating: Insulating varnish

60

FIG. 34

SURFACE RESISTIVITY VS TIME

70 °C 95% R.H.

Megohms

per "square”

I0 6 XXXP

6-7-048 Coating: Silicone resin <Dip soldered)

6-7-044 Coating: Silicone resin

61

FIG. 35

SURFACE RESISTIVITY VS TIME

Megohms

^ ^ 95% R.H.

per "square”

XXXP

HOURS

6-7-045 Coating: Silicone fluid (Dip soldered)

6-7-049 Coating: Silicone fluid

6-7-050 Control (Dip soldered)

6-7-054 Control (Ho preconditioning)

62

FIG. 36

SURFACE RESISTIVITY VS TIME

70°C ‘ 95% R.H.

Megohms

per ’’square”

10 6 XXXP

HOURS

7-7-041 Coating: Epoxy #1 (Dip soldered)

7-7-043 Coating: Epoxy #1

7-7-037 Control (Dip soldered)

7-7-045 Control (No preconditioning)

63

FIG. 37

SURFACE RESISTIVITY VS TIME

70 °C 95% R.H.

Megohms

per "square"

10 6 XXXP

7-7-038 Epoxy #2

7-7-034 Epoxy #2 (Dip soldered)

64

FIG. 38

SURFACE RESISTIVITY VS TIME

70 °C 95% R.H.

Megohms

per "square"

I06 XXXP

HOURS

7-7-047 Coating: Microwax (Dip soldered)

7-7-046 Coating: Microwax

7-7-042 Coating: Microwax (Dip soldered)

65

FIG. 39

SURFACE RESISTIVITY VS TIME

70°C 95% R.H.

Megohms

per ’’second"

10 6 XXXP

7-7-044 Coating: Insulating varnish (Dip soldered)

7-7-048 Coating: Insulating varnish

66

FIG. 40

SURFACE RESISTIVITY VS TIME

70°C 95% R*H.

Megohms

per "square"

7-7-035 Coating:

7-7-039 Coating:

Silicone resin

Silicone resin (Dip Soldered)

67

FIG. 41

SURFACE RESISTIVITY VS TIME

70 °C 95% R.H.

Me gohms

per ’’square”

10 6 XXXP

7-7-036 Coating: Silicone fluid (Dip soldered)

7-7-040 Coating: Silicone fluid

68

FIG. 42

Megohms

per ’’square”

10 5

SURFACE RESISTIVITY VS TIME

70 °C 95% R.H.

XXXP

HOURS

8-7-065 Control (Dip soldered)

8-7-057 Control (Dip soldered)

8-7-069 Control (No preconditioning)

8-7-071 Coating: Epoxy #1

8-7-067 Coating: Epoxy #1 (Dip soldered)

FIG. 43

SURFACE RESISTIVITY VS TIME

Megohms ^0 ^ 95% R.H.

per "square”

I0 5 XXXP

8-7-062 Coating; Epoxy #2

8-7-058 Coating: Epoxy #2 (Dip soldered)

70

FIG. 44

’ SURFACE RESISTIVITY VS TIME

, 70 °C 95% R.H.

Megohms

per ’’square”

10 5 XXXP

8-7-066 Coating: Microwax

8-7-070 Coating: Microwax (Dip soldered)

71

FIG. 45

SURFACE RESISTIVITY VS TIME

70 °C 95% R.H.

Megohms

per "square"

10 5 XXXP

8-7-072 Coating: Insulating varnish (Dip soldered)

8-7-068 Coating: Insulating varnish

72

FIG. 46

SURFACE RESISTIVITY VS TIME

70 °C 95% R.H.

Megohms

per "square"

10 5 XXXP

8-7-059 Coating: Silicone resin

8-7-063 Coating: Silicone resin (Dip soldered)

73

FIG. 47

Megohms

per ’’square”

SURFACE RESISTIVITY VS TIME

70 °C 95% R.H.

10 5 XXXP

8-7-064 Coating: Silicone fluid

8-7-060 Coating: Silicone fluid (Dip soldered)

74

V

FIG. 48

SURFACE RESISTIVITY VS TIME

70°C 95% R. H.

Megohms

per "square"

10 6 XXXP

10-7-071 (X)

10-7-067 (X)

10-7-069 (X)

10-7-065 (Z)

Coating: Epoxy #1

Coating: Epoxy #1 (Dip soldered)

Control (No preconditioning)

Control (No preconditioning)

75

FIG. 49

SURFACE RESISTIVITY VS TIME

70 °C 95% R. H.

Megohms

per ’’square”

10 6 XXXP

10-7-070 (Z) Coating: Epoxy #2

76

FIG. 50

SURFACE RESISTIVITY VS TIME

70 °C 95% R.H.

Megohms

per ’’square”

, 0 6 XXXP

10-7-070 (X) Coating: Microwax (Dip soldered)

10-7-066 (X) Coating: Microwax (Dip soldered)

77

FIG. 51

SURFACE RESISTIVITY VS TIME

70 °C 95% R.H.

Megohms

per "square”

I06 XXXP

10-7-072 (X) Coating: Insulating varnish (Dip soldered)

10-7-068 (X) Coating: Insulating varnish

78

FIG. 52

SURFACE RESISTIVITY VS TIME

70 °C 95% R.R.

Megohms

per "square”

10 6 XXXP

10-7-071 (Z) Coating: Silicone resin (Dip soldered)

10-7-067 (Z) Coating: Silicone resin

79

FIG. 53

SURFACE RESISTIVITY VS TIME

70 °C 95% R.H.

Megohms

per "square"

I06 XXXP

10-7-072 (Z) Coating: Silicone fluid

10-7-068 (Z) Coating: Silicone fluid

80

PIG. 54

SURFACE RESISTIVITY VS TIME

70 °C 95% R.H.

Megohms

per "square"

10 5 Epoxy -Glass

HOURS

5-10-001 Control

5-10-002 Control

5-10-004 Control

5-10-012 Control

(Dip soldered)

(Dip soldered)

(No preconditioning)

(No preconditioning)

81

FIG. 55

SURFACE RESISTIVITY VS TIME

70 °C 95% R.H.

Megohms

per ’’square”

10 5 Epoxy -Glass

5-10-013 Coating: Epoxy #1 (Dip soldered)

82

FIG. 56

SURFACE RESISTIVITY VS TIME

70 0 C 95% R.H.

Megohm s per "square”

10 5 Epoxy-Glass

5-10-005 Coating: Epoxy #2 (Dip soldered)

5-10-015 Coating: Epoxy #2

83

FIG. 57

SURFACE RESISTIVITY VS TIME

* 70 °C 95% R.H.

Megohms

per ’’square”

5-10-008 Coating: Microwax

84

FIG. 58

SURFACE RESISTIVITY VS TIME

70 °C 95% R. H.

Megohms

per "square"

10 Epoxy-Glass

5-10-006 Coating: Silicone resin (Dip soldered)

5-10-016 Coating: Silicone resin

85

FIG. 59

SURFACE RESISTIVITY VS TTME

70 °C 95% R.H.

Megohms

per "square"

1 0

5 Epoxy -Glass

8 —

6 —

4 —

2 —

I0 4

8 —

6 —

\ \ ov\\

4 — A \ \\ \

2 — \ ' Vv

r

— 5- 10-007

I0 3 \ .£

_

. 8 —

6 —

4 — \\

•i •>

2 —

10

3

o

’ \\

8 —

6 - >

4 — \

2 —

10

\

Shorted \

L

0 500 1000 1500 2000

HOURS

5-10-007 Coating: Silicone fluid

86

PIG. 60

SURFACE RESISTIVITY VS TIME

70 °C 95% R.H.

Megohms

per ’’square”

10 6 N-l

HOURS

5-26-019

5-26-020

5-26-023

5-26-024

Control (No preconditioning)

Control (No preconditioning)

Control (No preconditioning)

Control (No preconditioning)

87

FIG. 61

SURFACE RESISTIVITY VS TIME

70°C 95% R.H.

Megohms

per "squares”

HOURS

13-30-001 Control (Dip soldered)

13-30-002 Control (Dip soldered)

13-30-004 Control

88

FIG. 62

Meg,

cm.

10 5

VOLUME RESISTIVITY. VS TIME

70°C 95% R.H.

XXXP

HOURS

1-7-133 Control (No preconditioning)

1-7-129 Control (Dip soldered)

1-7-137 Control (Dip soldered)

89

FIG. 63

• Meg.

cm

.

VOLUME RESISTIVITY VS TIME

% 70 °C 95% R.H.

I0 6 XXXP

HOURS

2-7-045 Control (Dip soldered)

2-7-037 Control (Dip soldered)

2-7-041 Control (No preconditioning)

90

FIG. 64

VOLUME RESISTIVITY VS TIME

70°C 95% R.H.

Meg.

cm

.

I07 XXXP

HOURS

4-7-120 Control (No preconditioning)

4-7-112 Control (Dip soldered)

4-7-124 Control (Dip soldered)

91

FIG. 65

VOLUME RESISTIVITY VS TIME

70 °C 95% R.H.

Meg.

cm.

I05 XXXP

6-7-054 Control (No preconditioning)

6-7-050 Control (Dip soldered)

92

FIG. 66

VOLUME RESISTIVITY VS TIME

70°C 95% R.H.

Meg.

cm

.

7-7-037 Control (Dip soldered)

7_7_045 Control (No preconditioning;

93

FIG. 67

Me g

.

cm

.

VOLUME RESISTIVITY VS TIME

70 °C 95% R. H.

XXXP

0 500 1000 1500 2000

HOURS

8-7-057 Control

8-7-069 Control

8-7-065 Control

(Dip soldered)

(No preconditioning)

(Dip soldered)

94

FIG. 68

VOLUME RESISTIVITY VS TIME

70 °C 95% R.H.

Meg.

cm

.

Iq6 XXXP

10-7-065(Z) Control (Dip soldered)

10-7-069 (X) Control (No preconditioning)

95

FIG. 69

VOLUME RESISTIVITY VS TIME

70 °C 95% R.H.

Meg.

cm

.

10 5 Epoxy-Glass

HOURS

5-10-001 Control

5-10-002 Control

5-10-004 Control

5-10-012 Control

96

FIG. 70

VOLUME RESISTIVITY VS TIME

Meg. 70 °C 95% R.H.

cm.

10 6 N-l

HOURS

5-26-024 Control

5-26-019 Control

5-26-023 Control

5-26-020 Control

(No preconditioning)

(No preconditioning)

(No preconditioning)

(No preconditioning)

97

FIG. 71

VOLUME RESISTIVITY VS TIME

70 °C 95% R.H.

Meg.

cm.

13-30-001 Control (Dip soldered)

13-30-002 Control (Dip soldered)

13-30-004 Control

98

3. DIELECTRIC PROPERTIES

Measurements have been made on the dielectric properties

of a group of 16 metal-clad laminates. These include core

materials of the following types: XXP, XXX, XXXP , EpoxyGlass, G-5, G-7 , Teflon-Glass, and N-l . Individual families

of curves for each of the materials tested are presented in

Figures 72 through 87 (pp . 106 to 121), and give dissipation

factor and dielectric constant at various temperatures and

frequencies. Measurements were made using a two-terminal

conjugate Shering bridge system 4' with a two inch micrometertype uniform-field electrode holder.

This system allows the use of a disk-shaped sample

which may easily be prepared by machining the metal-clad

laminate to the desired diameter. Because the electrodes

extend to the edge of the sample, a special pattern such as

would be used in a three-terminal system is not required, and

the etching procedure is thereby eliminated as a possible

source of variation in the test results. The measurement

error in utilizing this system is considered to be about 1%

or less for dielectric constant. For dissipation factor the

* A. H. Scott, Paul Ehrlich, and J. F. Richardson, ’’Measurement of Dielectric Properties at Temperatures up to 500C,”

Symposium on Temperature Stability of Electrical Insulating

Materials, Special Technical Bulletin No. 161; (American

Society for Testing Materials, 1954).

99

error is considered to be within .0001 or 5%, whichever is

greater, at the lower frequencies, and .0015 or 5%, whichever is greater, at 10 7 cycles. All of the samples used in

this test were prepared from double-clad laminates having a

nominal 1/16 M core thickness.

Because of difficulties often encountered in making

adequate electrical contact between the copper electrodes

of the samples and the electrode holder, particularly at the

higher temperatures, all samples in the present group were

silver plated. The samples, which measured 2 inches in

diameter, were machined from the central portions of 4 inch

panels after the panels were electro-plated in order to

eliminate the possibility of errors due to the absorption

of the plating solution along the panel edges.

The present group of samples were tested principally at

the three temperatures of -30°C, 23°C, and 100°C. Additional measurements were made at 150° and 200°C on those

materials in which it was felt that higher temperature

operation might be feasible.

Additional processing, such as aging at various

temperatures and temperature shock, has not been included in

the present group of measurements, but will be dealt with at

a future date if exploratory tests indicate sufficient variation. Also, it will be necessary to make additional

100

3 P

measurements on a greater range of samples before sufficient

information is acquired to provide averages for the various

groups or classes of materials. Measurements will be made

on new materials as they are acquired and the frequency

range extended beyond 10? cycles when new equipment becomes

available

.

3 . 1 Dissipation Factor

A review of the curves for the phenolic base laminates,

Figures 72 through 80 (pp . 106 to 114), shows that the

dissipation factor was quite consistent in behavior at the

various temperature levels. At 10^ cycles the average

dissipation factor at -30°C was .044 for the XXP material,

.046 for the XXX, and .037 for the XXXP. At 23 °C (room

temperature) the average dissipation factor was .040, .040,

and .031 respectively for the XXP, XXX, AND XXXP materials.

At the 100°C temperature level the average dissipation

factor was .030 for the XXP material, .021 for the XXX, and

.029 for the XXXP. With the exception of an increase in

the dissipation factor in the 8-7 material (Fig. 79, p. 113),

from a value of .035 at 23°C and 10^ cycles to a value of

.046 at 100°C, all of the phenolic base materials showed a

i general reduction in the dissipation factor with an increase

in temperature.

101

Considerable variation in magnitude may be observed in

dissipation factor for the entire phenolic group at the

lower frequencies, particularly at the 100°C temperature

level. A clear characterization is not evident for each of

the types of material tested, and further data will be

necessary to complete this task.

Two samples of the epoxy-glass mat type were tested and

also showed a variation in characteristics, as may be seen in

Figures 81 and 82 (pp . 115 and 116). The dissipation factor

at 10^ cycles was about .02 or less, at all of the test temperatures, except for the 5-10 material (Fig. 82) in which

there was a sharp rise to .06 at 150°C. At temperatures of

100° or less, however, these samples showed some advantage

over those of the phenolic group.

Considerable differences may also be seen in the curves

for the two G-5 samples tested, Figures 83 and 84 (pp . 117 and

118). In the 8-16 sample (Fig. 83), the dissipation factor

was influenced to an extreme degree by the test temperature.

At 100°C the dissipation factor was so high as to make im-

% practical a determination with the existing equipment, and

consequently it has not been recorded. The 10-16 sample

(Fig. 84) showed characteristics similar to those of the

phenolics with respect to temperature but had a dissipation

factor of less than .02 at 10^ cycles, which compares well

with the Epoxy samples tested.

102

The dielectric properties of one sample of G-7 material

are shown in Figure 85 (p . 119). Dissipation at 10^ cycles

was .02 or less at temperatures up to 100°C but was influenced

to a marked degree at the lower frequencies.

The Teflon sample (4-19) had the lowest dissipation of

any of those tested in the group, as may be seen in Figure 86,

(p. 120). Variations may be noticed at the various temperature

levels but are relatively slight considering the temperature

range. At -30°C very little change is noticeable in the dissipation factor at the various frequencies, indicating a

characteristic somewhat different from that shown at the higher

temperatures

.

The N-l material, as shown in Figure 87 (p . 121)* showed,

good stability at the lower temperatures with a dissipation

factor of less than .02. At the higher temperature of 100°C,

the dissipation factor increased considerably over the entire

frequency range.

3.2 Dielectric Constant

From the curves showing the dielectric constant of the

materials tested, Figures 72 to 87 (pp. 106 to 121), it will

be noted that most of the materials behaved in the same

general manner with respect to temperature, the higher values

being associated with the higher temperatures. The notable

exception to this was for the Teflon material (Fig. 86, p. 120)

in which the opposite trend may be seen.

103

In the phenolic group the dielectric constant tended to

be somewhat lower for the XXXP materials than for the XXP and

XXX materials. At 10^ cycles an over-all average for the XXXP

materials tested would be about 4, while for the XXX and XXP

materials the dielectric constant would have an average of

about 5.

The epoxy-base samples tested, Figures 81 and 82 (pp . 115

and 116), both had dielectric constants at 106 cycles ranging

between 5 and 6 at temperatures below 100°C. Above this

temperature both samples showed increases to a value above 6,

with the sharpest rise recorded for the 5-10 material

(Fig. 82, p. 116).

The G-5 materials showed considerable differences in

dielectric constant, as may be seen in Figures 83 and 84

(pp. 117 and 118), particularly at the lower frequencies where

the 8-16 material rose to above 14 at 10^ cycles and 23 °C. At

10^ cycles both materials showed dielectric constants above 6.

The G-7 material showed good uniformity in dielectric

constant, Figure 85 (p . 119), at a temperature of 100°C and

below, with an average of about 7.5 at 10^ cycles. A sharp

rise may be seen for the 150° level.

The Teflon material, Figure 86 (p . 120), showed excellent

uniformity in dielectric constant for all conditions except

for the -30°C level where a sharp rise may be noted.

104

The N-l material, Figure 87 (p . 121), showed good

uniformity in dielectric constant at the two lower temperatures, but a sharp rise at 100°C.

As outlined previously, additional measurements will

be made and reported on as new materials are acquired.

105

FIG. 72

DIELECTRIC PROPERTIES

106

FIG. 73

DIELECTRIC PROPERTIES

p x 10 -2 DISSIPATION FACTOR XXP

(7-5)

-100 °c

V7 to CO 0

o

-30 °C

r

/ (

N —

J

\ L

(

t )/

I0 2 I0 3

I0 4 10® I06

I0 7 10® CPS

107

FIG. 74

DIELECTRIC PROPERTIES

I0 2 I0 3 10* I05 10® I0 7

10s CPS

108

p

FIG. 75

DIELECTRIC PROPERTIES

109

a.a»>

FIG. 76

DIELECTRIC PROPERTIES

n x 1Q -2 DISSIPATION FACTOR XXX

(7-6)

) 23 ° C

I U-

> -30 °C

(

3 100°C

I0 2 I03I0 4

I05I06

I0 7

IO

0 CPS

DIELECTRIC CONSTANT XXX

1 r\f\ o n

(7-6)

! i>

*—

>

i

] !UU c

) 23 °C

1 Lc

< r

IO

2

IO

3

IO

4

IO5

IO

6

IO 7

IO8 CPS

110

FIG. 77

DIELECTRIC PROPERTIES

ill

»"50t ‘ ’• ZB'

FIG. 78

DIELECTRIC PROPERTIES

DIELECTRIC CONSTANT XXXP

L.

(4-7)

1

1

> —

J

>

i i t

i. i 5

1

, 100°C

1co

to OCO o

o O

O

I0 2 I03 I04

I05

I0 6

I07

K)8 CPS

FIG. 79

DIELECTRIC PROPERTIES

113

FIG. 80

DIELECTRIC PROPERTIES

p x 1q -2 DISSIPATION FACTOR XXXP

(10-7}

—100°C

onOp

> —

c

—J U c —23 “C

)

I0 2

I0 3

I0

4

I05

I06

!0 7 10® CPS

114

FIG. 81

DIELECTRIC PROPERTIES

n x 1Q -2 DISSIPATION FACTOR Epoxy

(4-10)

i

1 148°C

4 Nv l i i88=g

> -30°C

t i « f *

I0 2 I0 3

I0 4

I05I06

I0 7 10® CPS

DIELECTRIC CONSTANT Epoxy

115

FIG. 82

DIELECTRIC PROPERTIES

DIELECTRIC CONSTANT Epoxy

(5-10)

4 Nv

) 150°C

o < >

>

1 100°C

) 23 °C

-30 °C

1

1 i i- A

I0 2

I03 10* I05

I06

I0 7

10® CPS

116

FIG. 83

DIELECTRIC PROPERTIES

117

FIG. 84

DIELECTRIC PROPERTIES

118

FIG. 85

DIELECTRIC PROPERTIES

n t n -2 DISSIPATION FACTOR G-7 10 a

u ' (5-18)

-100°C V4 - 150°C

r 23 °c

[ -30° C ,

i i

> t I" ' 'T A) E

I0 2 I03

I0

4

I05 I06 * I0 7 10® CPS

119

FIG. 86

DIELECTRIC PROPERTIES

DIELECTRIC CONSTANT TEFLON

(4-19)

1 ""*—

k 1 —

-23 °C

^100°C

‘ -30°C

—150 °C

-200 °C

I0 2

I03 I04

I05 10* iO7 10® CPS

120

fi*

FIG. 87

DIELECTRIC PROPERTIES

121

THE NATIONAL BUREAU OF STANDARDS

Functions and Activities

The functions of the National Bureau of Standards are set forth in the Act of Congress, March

3, 1901, as amended by Congress in Public Law 619, 1950. These include the development and

maintenance of the national standards of measurement and the provision of means and methods

for making measurements consistent with these standards; the determination of physical constants

and properties of materials; the development of methods and instruments for testing materials,

devices, and structures; advisory services to Government Agencies on scientific and technical

problems; invention and development of devices to serve special needs of the Government; and the

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research, development, engineering, instrumentation, testing, evaluation, calibration services, and

various consultation and information services. A major portion of the Bureau’s work is performed

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Commission. The scope of activities is suggested by the listing of divisions and sections on the

inside of the front cover.

Reports and Publications

The results of the Bureau’s work take the form of either actual equipment and devices or published papers and reports. Reports are issued to the sponsoring agency of a particular project

or program. Published papers appear either in the Bureau’s own series of publications or in the

journals of professional and scientific societies. The Bureau itself publishes three mdnthly periodicals, available from the Government Printing Office: The Journal of Research, which presents

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Information on the Bureau’s publications can be found in NBS Circular 460, Publications of

the National Bureau of Standards ($1.25) and its Supplement ($0.75), available from the Superintendent of Documents, Government Printing Office. Inquiries regarding the Bureau’s reports apd

publications should be addressed to the Office of Scientific Publications, National Bureau of

Standards, Washington 25, D. C.

l

r

. S. DEPARTMENT OF COMMERCE

Sinciatr Werks, Secretary , NATIONAL i'.UREAU OP STANDARDS

A. \ . Aulin, Director

THE NATIONAL BUREAU OF STANDARDS

The -cope of activities of the National Bur au of Standards is suggested in the following listing of

the divisions and sections engaged in technical work. In general, each section is engaged in specialized research, development, and engineering in the field indicated by its title. A brief description

of ti e activities, and of the resultant reports and publications, appears on the inside of the back

cover or ib : s report.

Electricity. Resistance and Reactance Measurements. Electrical Instruments. Magnetic

Measurements. Electrochemistry.

Optics and Metrology. Photometry and Colorimetry. Optical Instruments. Photographic

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and Lubrication. Engine Fuels. Cryogenic Engineering.

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^Office of Basic Instrumentation ^Office of Weights and Measures.
-

it* a -- «>•{ i sdj \t %x\

.

; S

.