NBSIR 75-720

Effects of Electroless Nickel Process

Variables on Quality Requirements

Fielding Ogburn and Christian E. Johnson

Corrosion and Eiectrodeposition Section

Metallurgy Division

Institute for Materials Research

National Bureau of Standards

Washington, D. C. 20234

December 1974

Final Report

Prepared for Research Directorate

Thomas J. Rodman Laboratory

Rock Island Arsenal

Rock Island, Illinois 60201

1

NBSIR 75-720

EFFECTS OF ELECTROLESS NICKEL PROCESS

VARIABLES ON QUALITY REQUIREMENTS

Fielding Ogburn and Christian E. Johnson

Corrosion and Electrodeposition Section

Metallurgy Division

Institute for Materials Research

National Bureau of Standards

Washington, D. C. 20234

December 1974

Final Report

Prepared for Research Directorate

Thomas J. Rodman Latwratory

Rock Island Arsenal

Rock Island, Illinois 60201

U.S. DEPARTMENT OF COMMERCE, Rogers C.B. Morton, Secretary

John K. Tabor, Under Secretary

Dr. Betsy Ancker-Johnson, Assistartt Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Acting Director

ABSTRACT

The project objective was to determine the effects of production

procedures on the characteristics of electroless nickel coatings. Deposition rate, pix)sphorus content, hardness, appearance, and nietal distribution are reported for deposits from several hypophosphite type electroless nickel baths, both proprietary and non-proprietary. The baths were

operated under a variety of conditions with variations of composition.

Extensive data are given on the relation of deposit hardness to phosphorus

content and to heat treatment at 100, 200, and ^OO^C. Some data are given

relative to electroless Ni-B, Ni-P-Cu, and Ni-P-Mi alloys.

EFFECTS OF EI£CTBDIESS NICKEL PROCESS VARIABLES CN

QUALITY EEWJEEmrrS

Objective

The general objective of the project under which this work was done was

to determine how characteristics of electroless nickel coatings are influenced by the operating variables of the process. The operating

variables were to extend to levels outside the nonnal operating ranges.

In this report we include deposits from non-proprietary baths and three

proprietary baths. Appearance, structure, plating rate, phosphorus

content, hardness, heat treatment, and thickness uniformity of the deposits are discussed. The- hardness data in conjunction with heat treatment is fairly extensive.

Solutions Used

Many of the electroless nickel (Ni-P) deposits were obtained from a

solution similar to those reported by Brenner [1];

As prepared, this solution has a pH of abojut 6,6; but. with use, the_pH

quickly drops to the buffered range of about ^.0-^,5. Normally the process was operated at or close to 96°C.

A modification of this Brenner bath was used to obtain deposits with les

than ^% phosphorus:

NiCl2 • 6H2O

Sodium hypophosphite

Sodium hydroxyacetate

30 g/1

10 g/l

50 g/l

NiCl2 • 6H2O

Sodium hypophosphite

Sodium hydroxyacetate

Temperature

pH

60 g/l

1 g/l

75-100 g/l

95°C

6.0-6.5

A few deposits were obtained from five (5) sulfamate baths:
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Nickel sulfamte g/1 32 32

Sodium hypophosphlte g/1 10 10

Sodium hydroxyacetate g/1 50 50

ArmDnlum citrate g/1

Sodium citrate g/1 - - Boric acid g/1 3 33

Borax g/1

Sodium lauryl sulfate mg/1 - 1.5

Amrronium hydroxide to pH for maintenance (not for

Sodium hydrodlxe to pH

1 2 1

32

10

25

4

50.2

21.2

5

50.2

21.2

100 100

25

3

30 30

1.5

make-up) 9.5

9.5 9.5

Several proprietary baths were used and these are identified with I, II,

and III. Except as otherwise indicated, these were all operated in accordance

with the vendor's instructions.

Solutions used for other than the Ni-P alloys will be identified where they

are discussed.

Plating Cell

Ihe basic plating cell was a glass cylinder of about 1.1 liter capacity

containing 1 liter of solution. This was immersed in a water-ethylene

glycol bath which was heated by a hot plate, a quartz iitmerslon heater,

and/or an infrared lanp. An autcanatic tenqperature control kept the

tenperature constant to within a degree centigrade for most of the experiments. Agitation, vihen used, was provided by air from fritted glass

disks at the bottom of the container, or a rotating magnetic stirrer.

Continuous filtration was used for the proprietary solutions. Ihe ^proximately 1 liter of solution was punped through a 15 um cartridge filter

at the rate of 10 liters/hour. This, of course, provided additioral

agitation.

Schedule of Deposits

Much of the data obtained is sunmarized in I^les 1 to 7. Ihose data

which had questionable validity or did not appear to be significant for

the purposes of this report cu:^ not Included.

Unless otherwise noted, the solution was freshly prepared for each deposit. Additions were made continuously to the Et^nner solution to maintain the nickel and hypophosphlte concentrations within about 10% of the

initial levels and the pH was maintained by the addition of anmonium

hydroxide. Where a pH range is given with 6.6 as the maxluum, the pH was

not adjusted at any time. Ihat is, the pH ms 6.6 as made up and decreased

with use. Ihe pH of the replenishment solution was in the nei^Tborhood

of 6.6 and hence, there was, in effect, a continuous addition of hi^er

pH solution.

Several of the deposits were obtained with other than the standard or

normal solution and operating conditions. Some of the variations are

Indicated in Table 1; others are indicated here.
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Deposits 1 to 7 were obtained successively from the same solution. The

solution was filtered and the pH adjusted to ^.5 between each run. When

deposit 7 was started, the bath had been operated ^5 hours and there was

an accumulation of phosphite equivalent to 12.6 g/1 of sodium phosphite.

Deposit l6 was obtained with no replenishment of the solution.

Ten g/1 of sodium phosphite had been added to the bath from vrtilch deposit

2^ was obtained.

Deposit 29 was withdrawn from the bath after three hours of plating with

continuous filtration when general decomposition of the bath began. A

new bath of the same type was used for deposits 57-61 and it was much

more stable.

Deposits 3^-36 were obtained successively fran the same bath.

During deposition of f^37 , the bath started to decarpose after about 2

hours. Deposit ^1 wa.^ subsequently deposited from the same bath after filtration and adjustment of composition.

Thirty-eight and 39 were obtained successively from the same bath ajid ^2-^5

from another bath.

Forty-six, ^7, and ^8 were operated normally except that no replenisl-ment

with Part C was made. Each bath started with a nickel concentration of 1.2

oz/gal (9 g/1).

Pinal Nickel

Time Concentration

Deposit hr (oz/^1) (g/1)

i46 3-V^ 0.88 6.7

^7 5 0.82 6.1

48 5 0.88 6.7

Deposits 49 and 50 were obtained from the same bath as #48 with the nickel

concentration maintained at 0.88 oz/gal (6.7 g/1) with Part C.

Deposits 52-56 were from the same bath operated with different levels of

hypophosphlte (Part B) coricentration. More details are supplied in the

discussion of the efft^'cts of hypophosphlte concentration on phosphorus

contents of the deposits.

Deposits 57-59 were obtained successively from the same bath and 60 and 61

successively fron another bath.

DeconpoGltlon

After a few hours of operation of the Brenner bath, bubbles of hydrogen begin

to form at Isolated points on the walls and bottc«n of the container especially

along scratches. This occurs at more and more points with time, and nickel

deposits become evident where gassing has occurred. This eventually progresses

to the point where the bath becc«nes virtually useless. This decojipDSition

or Instability is favored by high pH, high temperature, hl^ hypophosphlte,

and accumulated phosphite in the bath.
Stabilizers are usually added to proprietary baths to prevent or retard

this process. With bath I the instability showed up as rapid fonnation

of finely divided particles throu^iout the bath. This occurred after

several hours of operation with filtration but without replenishment of

Part C containing stabilizers and nickel salts. It also started to occur

after two hours of operation of bath I at a hlgheJ* than nomal pH of ^.2.

Plating Rate

It is well known that the plating rate is dependent on the solution con>- position and pH and on the solution torperature. A decrease in nickel

concentration, hypophosphite concentration, pH, or tenperature will decrease the deposition rate. Such decreases are noxrrally expected as a

plating bath is used unless steps are taken to replenish the solution

or to maintain its tenperature.

Rate data is given in Table 1. Ihese were estimated from micrometer

measurements or from weight changes assuming a density of 7.85 g/cm^ [2].

In the literature [3] there is a rule of thunob for the acid type of

electroless nickel solution that a 10°C change of tenperature will change

the plating rate by a factor of 2. This was essentially substantiated by

a series of rate measurements during deposition from the Brenner solution.

Specimen Tenperature Plating Wei^t of Rate of Deposition*

nine Deposit

20 50°C 71 hr 2.051 g 0.71 m/hr 0.028 miVhr

22 60 ^^ 2.593 1.45 0.057

21 70 21 2,^21 2.85 0.11

23 80 10 2.237 5.3 0.22

13 95 ^-V2 2.855 15.7 0.62

For each of these measurements a ft^sh bath was used and continuous

additions of hypophosphite and nickel chloride were made to maintain the

composition within 10^ of the original nickel and hypophosphite concentrations. The initial pH was 6.6 and the final was 4.3-^.5.

Appearance and Surface Roughness

With prolonged operation of a Brenner solution without continuous filtration, the upward facing surfaces of a deposit beccmie rougji. Apparently,

microscopic particles or sediment form in the solution and settle out on

the work surfaces causing rou^iness. Eventually nickel particles are observed on the walls of the container and the nickel deposition slowly

gets out of hand

.

This rou^ening is the only detrimental change in appearance that has been

observed for deposits from the Brenner bath. Rou^iness could probably

be prevented by continous filtration.

*Density assuned to be 7.85 [2].
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In the case of bath I, failure to use the replenisher solution (Part C)

containing stabilizers resulted in violent deconposltion of the bath with

precipitation of finely divided particles even though it was being continuously filtered. This resulted after several hours of operation during

which time the deposit was getting duller but not rougji. The deposit

would probably have gotten rou^ if it were allowed to reirain In the. bath

after deconposition began. It appears that a "bri^t" electroless nickel

will lose its brightness if the bath is not properly maintained.

When the Brenner bath was operated at low temperature, the deposit was

substantially bri^ter than nomHl. The effect was noticeable even at

80°C as compared with 95°C.

All the deposits from the sulfamate baths were full bri^t, conparable

to the proprietary bright baths.

Structure and Composition

Electroless nickel deposits, prior to heat treatment, do not have a grain

structure which can be seen microscopically. If properly etched, however,

a cross section will exhibit a banded or striated appearance. Ihls is

associated with variations in the phosphorus content and has been mentioned

in the literature. This interpretation of the strlatlons was verified

by scanning a cross section for phosphorus with an electron probe. The

dark layers or more heavily etched layers corresponded with layers of low

phosphor-Lis content. Ihis is described more fully In Appendix A which

has been published [^].

Fhosphorois Content

Usually a wei^ied sample of the electroless nickel was analyzed only for

nickel by the conventional dlmethylgloxime method. Ihe r^ralnder was

considered to be phosphorus. Early in the investigation, tl^ phospiiorus

was also determined gravimetrically as anmonlum phosphomolybdate.

Because the nickel and phosphorus determinations added up to lOO.OtO.lJS,

the more difficult phosphorus analysis was usually omitted.

Ihe ptos{±iorus content of a number of deposits was determined because

of its recognized inportance to their mechanical properties. Its

dependence on solution pH is well reco^iized smd the Electroplating

Engineering Handbook [5] indicates that increasing the hypophospdilte

or phosphite concentration in the bath also favors increased phosphorus

in the deposit.

The data in Table 1 are in agreanent with these observations. Ihe effect

of pH is Ulustrated by deposits m and 19. With a pH rarge of ^.2-^.5,

the deposit was 10.1$P. At the higher pH range of ^.5-6.6, the phosphorus was lower at 8.7%.

Comparison of deposits 7 and 1^ show the effect of accumulated phosphite

in the bath. Deposit #7 was from a bath which had been used for about

^5 hours and had accumulated phosphite equivalent to 12.6 g/1 of sodium . phosphite. (Deposits 1 through 6 came from the same bath with filtration

and pH adjustment at the end of each run and continuous addition of nickel

and hypophosphite replenishment solution.) Deposit 7 contained ll.l^P and

deposit 14, 10.1$P.
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The effect of accunmlation of phosphite in bath I Is shown by deposits

^2-^15. The phosphorus in the deposits increased from 7.^ to 9,6%?

during 19 hours of operation of ths bath with replenishment as j?ecc3iTinended.

The effect of hypophosphite content of the bath is illustrated by

deposits ^2,'k3, and 55 (norml hypophosphite content), deposits 53

and 5^ (low hypophosphite content), and deposit 56 (hi^ hypophosphite

content). Deposits 42 and ^3 were successive deposits from a new bath

I and were 7.4 and 8.2%P respectively. Another new bath I was operated

9 hours in the normal manner but without addition of the Part B replenishment solution (deposit 52). At the end of the 9 hours, chemical

analysis indicated a reducer level of 2.1 fl. oi/gal. Deposits 53 and 54 with

7.0% and 7.2%? were obtained from the same solution over a period of 24-1/4

hours during vriiLch time normal replenishment with Part B was made to hold

the low hypophosphite concentration constant. The hypophos^iite concentration

was then restored by addition of Part B to the 9 H.. oz/gal level and

deposit 55 was obtained over 5-1/3 hours. The last deposit, #56, with

10.1%?, was obtained during five hours of operation with nonnal ftirt B

replenishment, but after bringing the reducer level to 13.7 fl. oz/gal.

The association of phosphorus content with reducer level is obvious.

Deposit TlJiie %? Rart B

hr (Reducer) Level

fl oz/gal

New Bath I :

42 4-1/2 7.6 9

43 4 8.2 9

Another New Bath I without continuous

ReplenishHTient with fart B:

52 9 - 9-2.1

Continuous Replenishment of Depleted

Bath with Part B:

53 12-1/4 7.0 2.1

54 12 7.2 2.1

Normal Concentration of Reducer Restored :

55 5-V3 8.7 9.0

Concentration of Reducer Increased :

56 5 10.1 13.7

/
-7-

The relation of phospnorus to tenperature of deposition is also of interest.

Deposit Bath Deposition Rate of Deposition %F

Temperature Tljne mils/hr

_fC hr

20 50 71 0.03 12.5

22 60 0.06 11.9

21 70 21 0.1 . 11.1

23 80 9-1/2 0.2 10.0

19 96 5-1/2 0.5 8.7

Ihe deposition time was selected so that the deposit thickness for each

would be about the same. It is apparent that the phosphorus content is

related to the deposition tenperature. Part of the effect mi^t be due

to build up of phosphite during the longer runs at low tenperature, but

this seems unlikely. The amount of nickel deposited would not. have

differed much fran run to run and the phosphite build-i^ would probably

be about the same each tijne.

For each of these measurements, a fresh bath was used and continuous

addition of a replenishment solution was made to maintain the solution

ccrg:osition within 10% of the original nickel and hypophosphite concentrations. Ihe initial pH was 6.6 and the final was ^.3-4.5.

Low Rx)SFhorus Alloy

Baths II and III were obtained because the vendors advertised a low ptfiosphorus

content for the deposits, 2% or less. Both baths were operated in accordance

with the vendor's instructions, but deposits frcn both were hi^ in phosphorus, 12% and 12.33». Boti^i vendors were contacted and informed of our

experience. One vendor said they had replaced the low phosphorus bath

with a high phosphorus bath without charging the trade name or designation.

Ihey promised to send us more of the old phosphorus bath, but never did.

Ihe other vendor sent us more of their bath which gave us the sazne results.

We sent them a sairple of our deposit frc«n this second lot and they confirmed

our analysis of phosphorus 12. 3?, and sent us still more of their bath, but

we did not use the last lot.

One reason for using the alkaline sulfamate bath was the report that deposits

from it were 2 to 3? phosphorus [6]. Our deposits, nuirbers 80-82 5 were 5.2,

5.5, and 6.5XP. To obtain deposits with low phosphorus content we used

the modified Brenner bath with hl^ nickel and low hypophosphite content

and a pH of 6.0-6.6. This gave deposits with 2.8^ amd 3.7X phosphorus and

they were relatively ductile.

Hardness Measurement

All hardness measurements were made with a Knoop indenter using a Tukon

microhardness tester. Ihe indentations were made on cross sections with

the long axis parallel to tne substrate. Ihe location of the Inctentation

was such that it was not influenced by the proximity of either boundary
-8-

of the deposit or of another indentation. Some indentations led to the

formation of microcracks particularly with loads of 500 g. These were not

measured for hardness values and new indentations were made with a ligjiter

load

.

Ihe specimens for hardness measurement were mounted In an epoxy cement

cured at room temperature so as to avoid any heat effects. Ihe heat involved in nomal mounting in Bakelite or Lucite would have had serious

effects on the subsequent hardness measurements. After grinding and polishing, the specimens were etched Just sufficiently to bring out indications

of the usual striations. Heavier etching leads to low hardness values and

can be seriously misleading. Even such a light etch has significant effects.

Unfortunately this was not realized until after a nLBiber of the raeasurements

reported here had been made. Light polishing aTter the light etch may increase the measured hardness by about 35 units vdien a load of 100 g Is

used. This technique was followed for deposit 3^ and all subsequent deposits.

The hardness values reported for all preceding deposits have been increased

by 35 units.

Each hardness value reported is the average of one measurement of each

six indentations. Ihe cross sectional specimen was about 1/2 inch long

and three indentations were made near either end. All measurements were

made after the operator had checked his technique with a standard hardness block. The precision of the operator's measurements was the subject

of a brief evaluation. The stimdard deviation for a single measurement

was 1.^^ and for an average of six measurements it was 0.57% based on

^30 degrees of freedom. Ihis precision is meaningful only for measurements on a single specimen such as measur«nents before and after various

heat treatments. It is not a measure of the reproducibility of specimens

and is not applicable when coirparing one specimen with another.

Also the measur«nent precision is undoubtedly much poorer at low loads of

25 and 50 g.

Ihe hardress of an electroless nickel deposit is not uniform. It varies

from place to place, presumably as the canposition or phosphorus content

varies. This was evident when the hardness of a li^tly etched specimen

was jneasured on both a dark (etched) band and on a light band. The etched

band measured 526 HKp^Q and the light band measured ^83 ^OQO' ^'^^^^f

but significant differences were also noted between the two ends of

several mounted specin^ns. As noted earlier, three measuranents were made

at either end of each specimen and the indentations were made in the same

position relative to the banded etch pattern.

Initially, hardness measurements were made with a 500 g load_. Later it

was found that some of the specimens which had been heat treated at ^OO^C

cracked when the indentation was made. It was found that with a 100 g

load cracking was not a problem and all subsequent measurements were made

with a 100 g load.

In order to convert our own data from one load to another, a nmtoer of

specimens in several different hardness ranges were measured with 25, 50,

100, 200, and 500 g loads. This data was ccmbined to produce a gr^h

which could be used to convert data for one load to values
-9-

approximting what would have been obtained at another load. Such a

conversion graph has been helpful, but its use, even by the same operator

using the same equipment, introduces some error. The use of this specific

graph by another laboratory would be questionable. Tbo much depends on

the surface preparation of the specimen, on the operator's technique, and

on the hardness measuring equipment, ftost of the hardness values given

in this report as HK,qq were measured with a 100 g load. Some, however,

were measured at other loads and the values convei*ted to those for 100

g loads. "

Heat Treatment

Heat treatments were made sijrply by placing the specimens in an oven

already at the desired teirperature and holding the tenperature for the

desired tiine interval. Each specimen was allowed to cool in room tenpeiv

ature air. For hardness measurements, the specimens were metallographlcally

mounted after heat treatment and cooling to room tenperature exc^t those

specimens treated at 100 and 200°C. Ihese speclinens were mounted before

heat treatment and successively treated for the desired time intervals.

Thus for heat treatments at the same tenperature only one mounted specimen

was usually used for the successive time intervals. Ihe heat treatment

tijnes recorded are the times in the oven and include the tljne required to

bring the specimen to tenperature. Because the specimens were thin,

about 30 mils, they probably reached tenperature in a very short tljie;

insignificant except for periods of less them 15 minutes.

Hardness of Ni-P Alloys

Ihe hardness data for the Ni-P alloys are sunwarlzed in 'Tables 2 to 7 and

Figures 1-6. Ihese data Include hardnesses as-plated and after heat treatments of 1/2 hour to 9 days at tenperatures of 100**C to 800°C. Also these

data are for deposits frcm all the baths mentioned earlier and roost of

these had been operated at more than one conposition and under several

different operating conditions. Ihus these data represent a variety of

electroless Ni-P deposits.

As-plated hardness of deposits are given in I^le 2 and most of that data is

plotted in Figure J . Ihe scatter of that data may be due^ in part, to the nonuniformity of each deposit and to inpreclslon of measurement. Much of the

scatter, however, is real and indicates that the phosptorus content is not

the only feature of electroless nickel that Influences its hardness. Ihe

deposition process (plating bath) must influence the structure of caiposition of the deposit.

For phosphorus concentrations above about 73», there does not appear to be

any significant relation between phosphorus content and as-plated hardness.

Most of the hardnesses are within a range of 500-600 HK,qq- Below 7%, the

deposits tend to greater hardnesses with 732 the hardest we measured.

The Electroplating Engineering Handbook [5] gives a range a 100 DPH Ibr asplated deposits. Since most electroless nickel coatings have more than 7%

phosphorus, that statement is reasonable though not conplete. Qraham et

al [7] reported that for a specific, well-controlled, alkaline bath, the

hardness of the deposits decreased from 560 to 530 KHN with a corresponding
-10-

phosphiorus increase from ^.5 to 9.555. Any such trend in our deposits would

be obscured by other variables . Randin and Hinteman [ 8] using an acid

solution show a pronounced minimum in hardness at about 6.3$ phosphorus.

Ihis miniinum does not appear in our data. Iheir data, when con^jared with

ours, eirphasize that hardness is influenced by more than Just j*iosphorus

content

.

Table 2 and Figure 1 also give data for hardness after heat treatments of

eight hours at 200°C and 1/2 hour at ^00°C. In Figure 1, the points on

any one vertical line are for the same deposit. Fbr the 200**C heat treatment there is a clear trend to lower hardness with increasing phosip^rus

content. Generally the 200°C treatment increases the hardness, but for

some of the deposits with 10% or more of phosphorus, the hardness decreased.

During the ^00®C heat treatment, the hardness increased to 8^0 to 1001_HK,qq.

One exception was the specimen with 2,8% with a hardness of 812 HK, qq^^ less

than after the 200°C heat treatment. No trend of hardness with phoSpoorus

content was evident.

The data of Table 2 and Figure 1 raise the question of what would the data

look like after different heat treatment times. Was the hardening process

conplete? Consequently, data on hardness changes with heat treatment with

time wer-e obtained. Starting with storage at room tenperature, 19-23®C,

for two years, a decrease in hardness was c*)served for one low phosphorus

specimen and no significant change for two others.

%P As-Plated After 2 Years

7.1 602 607

12.5 536 5^2

At 100°C, measurements were made over periods of iq? to nine days. Ihese

data are in Ikble 3 and Figure 2. Significant changes occur at that tenperature, but at greatly varying rates. A specimen with 4.5$P has canpleted

the hardening process in one day. Those with 7,1% and 12.5$ took much

longer and may not have ccaipletely hardened after nine days. One specimen

decreased in hardness and another showed no change. Our data is not

sufficient to establish any pattern or correlation.

Heat treatments at 200°C were also conducted for periods up to nine days.

Most of the hardness changes took places within one day, but it is not clear

that the changes were corplete within the nine days. See 'jfeble ^ and Figure

3. Of interest are the four specimens with 12.2$ or more phosphorus.

Initially these decreased in hardness reaching a minimum between two and

ei^t hours and then recovering to a hardness which was sometimes more and

SOTietlmes less than the initial hardness. Ihis dip in hardness corresponds

to the decrease in hardness recorded in Table 2 and Figure 1.

Figure 3 shows a small dip in hardness between one and nine days of heat

treatment at 200**C. Ihe dip is very shallow; but because the hardness

measurements for each deposit were made on identical specimens, by

the same operator, with the same equipment; we believe the dips to be

real.

Data for hardness vs. time at HOO°C are given in Table 5 and some of them are
-11-

used to construct Figure ^. In Figure ^, where the 0 and 1/H hour points are

connected by straight lines, the hardness rapidly increases and then abruptly

levels off or slowly decreases. We do not know vriiere the break occurs. Higgs [9] observed that this break occurred within five minutes or perhaps

even one minute. IW0 of the deposits with ^.5 and 6.8$P did not show that

abrupt change, but continued to increase in hardness for at least two hours.

Again it is apparent that the properties of electroless nickel do not depend

solely on phosf^rus content.

The data in lable 6 and Figure 5 show hardness changes with duration of heat

treatment at 600°C. IXiring the first 1/^ hour, the hardness increases quite

rapidly and then abruptly levels off or decreases. As with the ^00°C heat

treatment, we do not know Just when this break occurs. Specimens fran

deposit 56 with 10.1$P, heated for two and four minutes, had hardnesses of

9^8 and 89^ respectively. Ihese heating times are not to be taken

too seriously as they include an unknown time for brirging the specimens up

to tenperature. They suggest, however, a very rapid rise and fall of

hardness during the first few minutes of heating.

Subsequent to the period of rapid change, the hardness of most of the

specimens changed slowly and went througji a raaxlmLm alter about one hour.

The low, 2.Q%, phosphorus specimen quickly softened initially and then

showed no further change.

In Figure 6, hardness is plotted against the temperature of a 20 hour

heat treatment for specimens with several different phosphorus contents.

'Table 7 gives the data for these curves and also gives equivalent data for

one hour heat treatments. The two sets of data are sufficiently similar

that preparing a graph for the one hour data is not helpful. With Intermediate percentages of phosphorus, the hardness Increases with tenperature

of heat treatment until a maxlmtBi Is reached near ^00°C. Above 4(X)°C there

is a sharp drop in hardness. Ftar the 12.5JP, the drop is much less for

tenperatures above ^00**C. With 2.8JP, the maxlmnn comes somewhere between

250 and 350®C.

The curves of Figure 6 are reminiscent of, but substantially different

from, those published by Gutzelt and Mapp [10], Baldwin and Such [10],

and Higgs [9] for one hour heat treatments of specimens with 8 to 9?

phosphorus. The differences are attributable to the duration of heat

treatment, phosphorus content, and, more importantly, the conditions of

deposition. Of practical significance Is the tenperature of maximum

hardness and how critical the tenperature is. Gutzelt and Mapp [10]

and Higgs [9] gives the teirperature for naxlmum hardness at ^00°C.

Baldwin and Such [10] found it to be nearer 350°C. Our data shows a maximum

nearer 300°C for 2.8$P, but within ^10 ± 15^C for deposits of the hl^r

phosphorus contents. The sharp drop off of hardness with tenperatures could

change the hardness substantially. With one hour treatments, this hardness

decrease seems to be less severe, but still could be sigiifleant. If the

heat treatment tenperature is to be designated in procurement specifications,

the danger of going to too high a tenperature should be considered. It

would be advisable to determine the minimum tenperature at v^ch a sharp

drop can occur.
-12-

The hardening of the nickel-phosphorus alloy when it is heated to ^00°C

is attributed to a phase change from a solid solution of phosplx>rus in the

nickel to a finely di^d-ded precipitate of a nickel- phosphorus ccwnpound

(usually considered to be Ni3P) in a nickel matrix or to the fonnatlon of

nickel particles within a matrix of the nickel-phosphorus conpound.

Subsequent softening aTter further high tenperatures is attributed to growth

of the nickel grains with segregation of the conpound. It is unlikely that

these processes are responsible for all the hardness maxima and minima that

appear in the plots of hardr^ss vs. heat treatment time and tenperature.

What other processes are involved is not known, but possible ones are

stress relief, expelling of hydrogen, and interaction with other iirpurities.

Adhesion

Ik) systematic investigation of adhesion was made. A nuni>er of test specimens

were prepared according to the schedule in l^le 8. These test specimens

were 1/8 inch steel rod, plated with about 1 mil (25 pm) of electroless nickel.

Ihey were sent to Rock Island Arsenal to be tested by the Beams high-speed

rotor method.

lb find conditions for obtaining adhesion of electroless nickel to Cr-Mo-Va

steel (gun stock), 10 wafers of the steel were prepared according to the

schedule in Table 9 and plated with electroless nickel from solution I

.

One half of each wafer was tested as-plated for adhesion and one half after

one hour at ^00°C. The test consisted of making a rl^t angle bend around a

V8 inch diameter mandrel and visual examination for separation of the coating

Trom the steel. The results are tabulated in Table 9. The best adhesion

was obtained with an A1(N03)3-HC1 pickle at ^2!°C [11] followed by a lactic

acld-peroxlde^desnLitter at room tenperature [11]_. Usually one hour at ^OO^C

Inproved the adhesion and never did it result lri"poorer~adhesion.

If such pretreatments are to be used for gun bores, one should know the

amount of metal removed. Ihls proved to be close to 0.^ mil (10 pm).

When the pickle and desmutter were used at roan tenperature for the same

time periods, the metal removed was 0,005 mil (1.2 um) and subsequent adhesion

of a deposit from bath I was not adversely affected.

Wear Tests

A few wear tests were made to conpare chroinlum (standard bath at 30 A/dm^

and 55°C) with nickel-8.^? phosphorus from bath I. The data from these

tests with a Taber Abraser are summarized in Table 10.

These wear tests were made with CS-17 and CS-10 vdieels with a load of 1000 g.

A track was worn into each specimen prior to the test runs by making several

runs of 2500 cycles each. Several test runs were then made on each specimen

and the average weight loss or thickness loss is reported. CS-17 wheels were

used initially. Subsequently we found that the CS-10 wheels were less prone

to load-up with metal px)wder and gave more consistent data.

The data in Table 10 indicate that the ^00°C heat treatment inproved the

wear resistance of the electroless nickel-phosphorus. Electrodeposlted

chromium, however, was still more wear resistant. Ihls may be indicative

of service perfonnance, but we do not know how this test correlates with

service life.
-13-

Platlng of Gun Bores

Prior to plating 177 caliber gun bores, the bore of a 20 inch length of 3/l6

inch I.D. steel tube was plated with 0.7 mil (l8 m) electroless nickel from

bath I to detemine what metal distribution problems there mi^t be. From

microscopical examination of cross-sections of the deposit, it was determined

that there was' no significant variation of coating thickness from end to end

or circumferentially

.

Ihe set-up used for plating the gun bores is indicated in Figure 7. Once

the barrel was in place, the ccrplete plating cycle was carried out by

appropriate manipulation of stof>-cocks and pumps. Continuous additions

were made to the electroless nickel bath in a 2 liter reservoir where

automatic tenperature control was maintained. The plating solution was

continuously filtered.

Initially the bore was swabbed with benzene soaked gun patches and then it was put in place. Ihe A1(N03)3-HC1 pickle was punped throu^ the barrel for

four minutes, cold tap water for one minute, and lactic acid-peroxide desrautter

for two minutes, all at room tenperature. A cold water rinse for one minute

was then followed by the electroless plating bath.

Four barrels were plated using bath I at 89**C with the pH at ^.8. They were

delivered to Rock Island Arsenal. Attenpts to plate barrels from bath III

were ccnpletely unsuccessful. No deposit at all was obtained. This bath was

operated at a pH of 5.8 at 90°C and two widely different flow rates were

tried. Because barrels could be plated with another proprietary process, no

real attoipt was made to find suitable operating ccaiditions for this bath.

Presumably this is an exanple of the detrimental affects of excess agitation

of electroless nickel-phosphorus baths with catalytic-^ison stabilizers [12].

Electroless Ni-P-Cu Alloy

A deposit was obtained from a bath containing:

We believe the deposit fran this bath contained a small amount of copper,

but we did not verifV this. Deposition was carried out for k 3/^ hour at

95°C with continuous filtration and continuous addition of nickel, copper,

and hypophosphite . Ihe initial pH was 6.2 and the final was ^.8. Ihe

deposition rate averaged 0.5 mil/hr and the final deposit was brittle. The

Ni-P-Cu and the Ni-P deposits frcm the sulfamate bath seemed to be of equal

bri^tness, but the surface texture of the Ni-P-Cu deposit, when viewed

microscopically, appeared to be nuch smoother than the Ni-P deposit. It

appeared that seme leveling had occurred.

Nickel sulfamate

Copper sulfamate

ICQ ml/1 (7.5 g/1 Ni)

0.65 ml/1 (^0 n^l Cu)

Boric acid (present in sulfamate)

Sodium hydroxyacetate

Sodium hypophosphite

Sodium lauryl sulfate

50 g/1

10 g/1

1.5 ©n/l

3 g/1
Hardness was measured after 1 hour heat treatments:

As-plated

400°C

600°C

800°C

Nl-P-Mn Alloy

Because a small amount of manganese codeposited with nickel stabilizes the

hardness of nickel during heat treatments at ^30°C [13], we attejipted to

codeposit manganese with electroless nickel-phosphorus. Two sulfamate baths,

differing only in the concentration of manganese sulfate, were tried.

Nickel (added as nickel sulfanate) 7.5 g/1

Nknganese (added as manganese sulfate) 1.4 and 2.8 g/1

Sodium hypophosphite 10.0 g/1

Boric acid 3.0 g/1

Sodium hydroxyacetate 50.0 g^l

Sodium lauryl sulfate 1.5 mg/l

With 2.8 g/1 of manganese in the bath, the average deposition rate over a

period of 5 hours was 0.2 rail/hr. (5 vm/hr.). The initial pH was 5.7 and

dropped to 3.8. Hie deposit, steel gray in color, was too brittle to use

a load of 50 g or more for hardness measurements and contained about 1%

manganese. The bath with 1.4 g/1 of manganese deposited at a rate of 0.3

mil/hr. (8 um/hr.) and gave full bright deposits containing about 0.05? Mn.

These were also quite brittle.

Portions of these Ni~P-Mn deposits were heated for 1 hour at various

tenperatures, allowed to cool in air, and measured for hardness with a

25 g load.

Low Manganese High Manganese

As-plated

HK25

489

^

485

400°C 649 768

500°C 769

600°C 791 931

700**C 811

800°C 574

The manganese apparently increases the heat treatment tejiperature for maximum

hardness, but without increasing the maximum hardness. No data was obtained

to relate hardness to the duration of heat treatment.

Electroless Nickel-Boron

There is some interest in electroless nickel-boron coatings because they

are harder than the nickel-phosphorus deposits and the changes undergone

during heat treatment are somewhat different. Electroless nickel-boron

baths were not extensively investigated in the course of this project, but

a few deposits were obtained frc»n several different baths including both

borohydride and dimethylamineborane types. The fonnulation of the various

baths are given In T^le 11.
-15-

Bath 1 proved to be rather unstable. At 90° it deconposed spontar^usly

but slowly with the formation of metallic particles. At 80**, vd.th continuous

filtration throu^ a 1-3 pni polypropylene filter, deconposition became

evident after one hour of operation.

Bath 2 was used by Gorbunova et ^ [1^]: It differs from bath 1 by an

increase of thallium nitrate from 7 to 100 mg/1. Deposits were obtained

from this bath at 80, 90 and 95°C. At the lower tenperature they were

dark gray with some roughness and the plating rate was 0.5 mll/hr (13 ym/hr.).

At 95°C the plating rate was 1 mil/hr (25 unvOir.) and the deposits were a

silvery gray and smooth. The hardnesses tabulated belcw were measured asplated and after a single heat treatment at each of several tenperatures

.

Deposited Deposited

at 95^*0 at BO^C

HK^Q HK25 HK23

As-plated 76^ 8^2 85^

i\00°C 979 1272 12^15

600**C 907 983

800°C 976

We found that when this hig^i pH bath was operated at 90° or 95**C, the internal

bushings of our punp would swell and seize. At 80°, this was not a problem.

Bath 3. This bath ceased to function after about five minutes. It Is

possible that it was poisoned by the stop-off used on the steel work piece

or the lead ion concentration was too high.

Bath ^ was given in a technical bulletin of the Gallery Chemical Ccnpany.

Uils bath operated 1 1/2 hours and then stopped plating. Vfe did not

attenpt to determine the reason plating stopped or to make up a new bath.

The plating rate was 0.7 mll/hr (17 ym/hr.) and the deposit was a silvery

gray, stressed, and quite brittle.

Hardness

As-plated 777 HK^j,

1 hr. at U00°C II98

1 hr. at 600°C 1095

Bath 5 is given in U.S. Patent 3,738,8^49 (June 12, 1973), H.E. Bellls

assi©Tor to E.I. Du Pont de Nemours and Co. The plating rate measured 0.^

mil/hr (10 ym/hr.). Surface rou^iness began to appear after 3 1/2 hours of

operation. Hie deposit was dull gray and was analyzed at 95 Ni. Its

hardness was 75^ ^^0* ^~P^^^*

This sampling of electroless nickel-borcn is not conprehensive, but It does

suggest that as-plated the hardness is more than nickel-phosphorus deposits

with the possible exception of some with 2-4 X/2% phosphorus. After one

hour at 400°C, the hardnesses of the two types of electroless nickel do not

differ significantly. After one hour at 600°C, however, the boron alloy

retains a much greater hardness than the phosphorus alloy. Gorbunova et al

show that a plot of hardness vs tenperature of heat treatment has two

naxima, at 300°C and 600°C, with a minimum at 400°C for alloys of 5.7 and

6,^% boron. ^.3% boron has one maximum at 300°C.
-16-

Ihlckness Uniformity

Ihe Electroplating Engineering Handbook [5J states: "Electroless plating Is

of uniform thickness on all areas of the solid part, regardless of its shape

or geometry." In the context of electroplating this may be a reasonable

statement, but it is misleading. Just how misleading was the subject of

some consideration.

The rate of deposition is a function of tenperature and solution composition. A systematic variation in either will usually lead to a corresponding variation in thickness. This means that to achieve a uniforro deposit

thickness, the average solution cojiposition and temperature everywhere

over the surface must be kept the same. Since this can be very difficult

to achieve, it raises the question of how noninlfonn a deposit is likely

to be. Ihe results of a few experiments made duriJTg the course of this

project will give a feel of the sort of nonunlformity to expect.

The exterior of a one inch diameter brass tube plated 2 hours without

agitation, while suspended in a horizontal position well off the bottcm

of the container. The plated tube was sectioned near its center and

examined microscopically around the circumference. At the bottom the

deposit thickness was 0.68 mil. at the sides it was 0.75 mil, and at the

top it varied from 0.52 to 0.88 mil. This variation at the top was

associated with deposit rou^mess presumably caused by settling of

microscopical sediment formed in the bath. The lower value of 0.52 rail

probably represents the thickness that would have prevailed if there had

been no sediment.

Figure 8 is a ptotomicrograph of a section of one of two brass bolts

plated for 2 hours in the EQ?enner bath without agitation and while

suspended by a wire. The plating rate was about 0.6 miVhr. The

electroless nickel deposit is the layer between the brass substrate and

an overplate of electroplated nickel. The deposit thickness was measured

at the top and bottom of the thread at six different "threads" (12

locations). There was a 6% variation between peaks conpared to a 71%

variation between valleys. The average peak to valley thickness ratio

was 2.1. Obviously solution replenishment in the valleys was not as good nor as uniform as at the peaks.

Figure 9 is a section of another bolt plated 2 hours in bath I at a

slower rate, about 1/3 that of the bolt In Figure 8, 0.2 mlVhr. Six

valleys varied fi-om 0.38 to 0.^0 rail. Six peaks varied from 0.^^ to

0.50 mil. The ratio of the two averages was 1.2. The lnproved throwing power may have been influenced by the bath ccirposition, but it may

also be due to the slower rate of deposition v*iich pennitted f&ster

solution replenishment relative to deposition of nickel.

Figure 10 is of a bolt plated near the faster rate in bath I with

agitation frcsn a magnetic stirrer and frc«n solution punped in and out

of the tank. The thickness ratio of peak to valley is 1.013, hardly

sl@Tifleant. This good throwing power is attributable to appropriate

agitation.
-17-

The deposit shown in Figure 11 was on a ^ mil diameter wire plated in

bath I at the same time as the bolt with uniform metal distribution.

It is obvious that the metal distribution is not uniform. The maximum

thickness ratio is 1.25. Apparently the agitation did not even out the

metal distribution on the wire as it did for the bolt. The wire was

suspended in the bath in a manner which pemitted it to move with tl7e

solution within a revolving agitation pattern. The metal distribution

probably reflects a net motion between the wire and solution resulting

in unequal solution replenishment.

SUTTITBjy

Of the coating characteristics which have been considered in this report

are appearance, roughness, hardness, and thickness. Ihese should be

discussed in terns of the process control.

Appearance and roughness can be readily observed and an evaluation is easily

made provided the requirements are adequately stated. Solution agitation

and filtration are inportant here to prevent settling of the sediment on the

work surface. To minimize formation of the sediment, the bath needs to be

properly controlled, primarily by replenishment of the stabilizers and

avoiding the conditions which favor solution instability such as too high a

tenperature, too hi^ a pH, too much hypophosphite, and too much phosphite.

Tine latter is a matter of the working life of the bath. Phosphite continuously accumulates and promotes formation of sediment and bath deterioration.

On the basis of the data given here along with that in the literature,

several generalizations can be made about the hardness of electroless nickel

deposits.

1) Most deposits will have about the same as-plated hardness. Ihose

with less than 7 1/2%? are likely to be harder.

2) Heat treatments at 200*^0 is not likely to be detrimental though a

few coatings with hi0i phosphorus content may become a little

softer. Some deposits may Increase significantly in hardness.

3) Heat treatments at 300°C and ^00°C will harden the deposit.

^) Ihe optimum tenperature for a one hour heat treatment of a sp>ecific

deposit may be anywhere between 250 and ^25°C, but will usually be

between 350 and ^25°C. Heating above ^20°C is likely to give hardnesses significantly less than the maximum unless the pdiosphorus

content is above 12%.

Tensile strength and ductility are inportant to applications of electroless nickel. These properties were measured by Graham et al [7] for

deposits with 4-3/^ to 8-3/^?P after heat treatment at 200, ^00, 600,

and 750°C. In general these two properties increase with increasing

phosphorus in the as-plated condition and after heating at 200°C. After

heating at 400°C, all the deposits are very brittle and quite weak.

To control the properties of electroless nickel, it may be desirable

to control the phosphorus content. This requires chemical analysis

of the deposit and good control of tenperature, pH, and bath conposition. To assure a low or a high phosphorus content should not

be difficult, to assure an average conposition within 1 pjercentage

point requires more than normal attention to detail.
-18-

The control of deposit thickness can offer problems. Usually its

meas'areraent can only be made by microscopical techniques. The thickness can be estimated from the time of plating provided the solution

is kept under close control and the plating rate is determined

Independently. Cne reconmended procedure is to plate a coupon simultaneously with plating of the work piece. Appropriate wei^t and

area measuranents of the deposit on the coupon would provide a

reasonably good thickness estimate.

Uniformity of coating thickness cannot be assumed. A 2 to 1 variation

is possible. Agitation can even out the metal distribution and it

can make matters worse; though, in general, it is probably helpful.

/
Bibliography

[1] A. Brenner and G.E. Rlddell, Proc. Am. Electroplaters' Soc., 23

(19^6).

A. Brenner and G.E. Rlddell, ^c. Am. Electroplaters' Soc., 156

(IW).

[2] "Syirposium on Electroless Nickel Platir«", AS1M Special Technical

Publication, No. 265, I6 (1959).

[3] "Symposium on Electroless Nickel Plating", ASIM Special Technical

Publication, No. 265, 29 (1959).

[4] F. Ogbum and C.E. Johnson, PlaUng 60, 10^3 (1973).

[5] A.K. Graham, Ed., Electroplating Engineering Handbook, Van Nostrand

Reir*iold Co., New York, 3rd ed., ^97 (1971).

[6] L. Cadoma and P. Cavalotti, Electrochemica Metallorum 1, 93 (1966).

[7] A.H. Graham, R.W. Lindsay, and H.J. Read, J. Electrochem. Soc.,

112, ^01 (1965).

[8] J. P. Randin and H.E. Hinterman, Plating, 5i, 529 (1967).

[9] C.E. Higgs, Electrodeposition and Surface Treatment, 2, 315 (1973-7^)

[10] G. Gutzeit and E. Mapp, Corrosion Tech., ^ 331 (1965).

C. Baldwin and T.E. Such, Trans. Inst. Metal Finishing , ^

73 (1968)

[11] U.S. Patent 3,505,095; April 7, 1970 assigned to U.S. Atomic Energy

Corrmission by G.S. Petit and R.R. Wright.

[12] F.A. Lowenheim, Ed. , Modern Electroplating, Wiley-Interscience, New

York, 3rd ed., (197^).

[13] W.B. Stephenson, Jr., Plating 53. I83 (1966).

[1^] K.M. Gorbunova, M.V. Ivanov, and V.P. Moiseev, J. Electrochem. Soc,

120, 613 (1973).

TECHNICAL BRIEF

APPENDIX A

Banded Structure of Electroless Nickel

F. Ogburn and C. E. Johnson*

THE ETCHED CROSS SECTION of an elcctroless nickel

(Ni-P) deposit generally is characterized by narrow

or wide striations formed by variations in the degree of

etching. These are usually attributed to variations in the phosphorus content of the deposit.' The evidence cited,

however, is meager and is based on appearance after treatment at 700°C for 1 hr and on potential variations during attack by red fuming nitric acid. Some of the heattreated deposits show striations caused by variations of

the population of dark particles, which were presumed

to be NijP precipitated during the heat treatment. There

is no reason to doubt this explanation of the striations, but it would be more satisfying to have more direct evidence. Such evidence is given here. Figure 1 is a photomicrograph of the etched cross section of an electroless nickel deposit, as plated, of the Ni-P

type having wide striations. The 150 /im thick deposit was obtained at 96°C from an acid bath containing hydroxyacetic acid, similar to the original formulation of Brenner and Riddell.^ The etching solution was 1 part

nitric acid and 3 parts acetic acid. The Knoop diamond

indentations were used as index marks for the electron probe analyses. Figure 2 is a photomicrograph of the same area with an electron probe trace of the phosphorus

'Metallurgy Division, National Bureau of Standards, Washington, D C.

20234.

Fig. 1. Photomicrograph of cross section of electroless nickel deposit. Knoop indentations were mode for indexing purposes.

OCTOBER, 1973

content superimposed. (Note the Knoop diamond in- dentations visible in Fig. 2.) Each dot in the row across

the center indicates the location of a measurement by

the electron probe. The beam size is actually about 0.5

in diameter and the measured x-rays are emitted from

an area two or three times that diameter. The curve made

up of dots on the upper part of the micrograph is a plot of the phosphorus content. A linear scale for the phosphorus content is on the ordinate with the maximum

concentration on the curve at about 8 wt per cent. Zero

per cent level is indicated by the row of dots in the lower

left corner. Comparison of the two figures indicates a reasonable

inverse correlation between phosphorus content and the degree of etching.

More precise measurements were made on either side of the lower tips of the four indentations. From left to

right, the measurements at each location are as follows:

Wl Per Cent

Location Ni p

1 92.4 6.6 2 92.1 7.1 3 92.8 7.8 4 93.8 7.0 5 93.0 7.6 6 94.1 6.7 7 93.3 7.3 8 93.0 7.5

Fig. 2. Electron probe trace of phosphorus content across cross section of electroless nickel deposit. Zero per cent phosphorus is indicated by white dots in lower left corner. Maximum value is about 8 wt per

cent phosphorus. Row of dots across center indicates position of each

measurement.

1043
Kach o( flicsc values for |)h<)si)horiis had, before rounding,

a standard deviation of 0.7 per cent of the phosphorus

concentration. (>oinparinK these data with F"ig. 1 shows

again the inverse relation of phosphorus content with

de|)th of etching.

Siipi)orting evidence was also obtained from hardness

ineasiirernents within a "white" band and an adjacent

"dark" band on another portion of the same specimen « hich had been given only a light etch. The KH200 values were 4H3 anfl 526 respectively, the softer material being

the more resistant to etching and having the greater

phosphorus content. This is consistent with hardness

measurements made on similar deposits of differing

phosphorus content. Decreasing phosphorus corre- sponded with increasing hardness. The relation between phosphorus content and etching

rate of the a.s-|)lated alloy suggests a possible means of estimating the phosphorus.

This work was carried out as part of a project supported

by the Weapons Laboratory — RIA, Rock Island Arsenal,

Rock Island, Illinois.

REFERENCES

1. A. K. Graham, ed., "Electroplating Engineering Handbook,"

3d'Ed., New York, Van Nostrand Reinhold Co., 1971; p. 498.

2. A. V\'. Coldenstein, W. Nosfoker, F. Schossberger, and G.

Gutzeif, ;. Electrochem. Soc, 104, 104 (1957); G. Giitzeit, This Journal, 46, 1158 (1959).

3. A. Brenner and G. E. Riddell, Proc. Am. Electroplaters Soc,

34,156(1947).

Manuscript received April 25, 1973,

Revised manuscript received June 27, 1973.

Discussions of this technical brief are invited for publication

in a future issue of Plating.
TABLE 1

Operating Conditions for Electroless Nickel Deposits

Deposit lype of pH Tenp. Deposition Deposition Phosphorus Page

No. Solution - °C Time Rate* Content Reference

Hours mil/hr of Deposit

Per Cent

1 Brenner 6.6-4.2 96 0.65 3»5

2

ti 4.5-4.2 96 3i5

3

u 4.5-4.2 96 3,5

4

It 4.5-4.2 96 0.6 M 3»5

5

!l 4.5-4.2 96 0.75-0.51 3,5

6

tl 4.5-4.2 96 3,5

7

tl 4.5-4.2 96 11.1 5

8

tt 6.6-4.3 96 6 0.95-0.63

13 tl 6.6-4.5 95 5 0.5 M 7.1 4

14 It 4.5-4.2 96 6 0.78-0.45 10.1 5

15 tt 6 . 6-5 .

0

96 5 0.8 M 7.1

16 tt 6.6-5.5 98 6 4.5 3

18 tt 6.6-4.2 4-1/2 0.6 M 9.4

19 tt 6.6-4.5 96 5-1/2 0.5 M 8.7 5,7

20 tt 6.6-4.4 50 71 0.03 M 12.

5

4,7

21 tt 6.6-4.3 70 21 0.1 M 11.1 4,7

22 tt 6.6-4.4 60 44 0.06 M 11.9 4,7

23 tl 6.6-4.3 80 9-1/2 0.2 M 10. 0 4,7

24 tt 5.6_4.5 96 7-1/2 0.5 M 9.4 3

27 tt 6.6 96 4 29 Bath II 6.0 90 9.6 3

34 Bath I 4.6 85 7 0.54 6.8 3

tl 4 6 85 6 0.52 3

36 II 4.6 85 g 0.54 7.2 3

37 tt 5.2 87 2 0.78 3

38 Brenner 4.5 95 6 0.36 9.7 3

39 II 4.0 95 9 0.22 11.4 3

40 tt 6.6-3.8 50 136 0.022 12.2

41 tt 4.6 86 5 0.54 3

42 Bath I 4.7' 86 4-1/2 0.57 7.4 3,6

43 tt 4.7 86 4 0.55 8.2 3,6

44 tt 4.6 86 5 0.54 8.0 3,6

45 tt 4.7 86 5-1/2 0.57 9.6 3,6

46 tt 4.8 86 3-1/4 0.65 3

47 tt 4.5 86 . 5 0.50 3

48 It 4.5 85 5 0.47 3

49 It 4.5 86 5 0.39 10.3 .3 50 tt 4.8 86 5 0.43 10.0 3

52 It 4.7 86 9 0.54-0.29 3,6

53 It 4.7 86 12-1/4 0.28 7.0 3,6

54 tt 4.7 86 12 0.27 7.2 3,6

55 It 4.7 86 5-V3 0.56 8.7 3,6

56 It 4.7 86 5 0.60 10.1 3,6
TABLE 1 (Con't.)

lype of

Solution

PH Temp. Deposition

°C Time

Hours

Deposition

Rate*

mll/hr

Phosphorus

Content

of Deposit

Per Cent

Page

Reference

Pi TTJ L QD h 1 ? 8 0

58 II 5.8 90 4 0.37 3

TT 6 1 QO J 0 9fi n 2 1 60 II 5.8 90 0.55 12.6

61 II 5.8 90 0.33

62 Sulfamate 6.7-3.5 95 5 0.48 8.4

63 tt 5-3.5 95 5-1/4 0.45

64 II 6-3.9 95 6 0.48

65 If 4-3.7 95 6 0.32

66 II 6.7-4.2 94 6 0.4

71 Bath III

Alkaline

5.8 ^. 90 0.54 12.1

80 Sulfamate 9.5 • .•- 75 0.5 6.5 7 81 II 9.5 80 0.5 5.5 7 82 II Brenner

9.5 90 0.67 5.2 7

86 Modified

Brenner

6.0-6.6 95 0.25 2.8

88 Modified 6.0 95 5 0.2 3.7

* - Micrometer measurements are Indicated by an M. Other thickness values were determined from weight and area measurements.

\
TABLE 2

Hardnesses of Nl-P Alloys

As-Plated and After Heat Treatment

Deposit Phosphorus - As-Plated 8 hr. 1/2 hr. 1 hr. Type

No. % HK^ 200°C 400°C ^00°C of

HK^QQ HK^OO ^100

60 12.6 524 520 - 855 II

57 12.6 518 523 - .845 II

20 12.5 536 508 961 - Brenner

40 12.2 548 515 936 - Brenner

71 12.1 509 521 840 766 III

22 11.9 561 491 957 - Brenner

21 11.1 525 515 916 - Brenner

7 11.1 554 560 883 - Brenner

49 10.3 539 616 950 - I 14 10.1 566 557 944 - Brenner

56 10.1 544 639 948 - I 23 10.0 512 491 957 - Brenner

50 10.0 532 602 935 - I 29 9.6 541 737 969 - II

45 9.6 547 709 1001 - I

18 9.4 547 - 936 - Brenner

24 9.4 556 608 905 - Brenner

19 8.7 584 628 890 893 Brenner

55 8.7 549 - - - I 62 8.4 480 - - - Sulfamate

43 8.2 540 702 934 - I

44 8.0 546 717 953 I

42 7.4 551 731 969 I

36 7.2 539 767 940 I

54 7.2 576 735 847 I 13 7.1 602 720 921 Brenner

15 7.1 592 Brenner

53 7.0 569 762 858 1

34 6.8 611 736 852 I

80 6.5 679 Alkaline

81

Sulfamate

5.5 660 Alkaline

82

Sulfamate

5.2 624 Alkaline

16

Sulfamate

4.5 732 811 911 923 Brenner

88 3.7 660 8261 829 Modified

86

Brenner

2.8 692 835 , 812 Modified

Brenner

48 hrs. at 200°C.
•

. TABLE 3

Effect of Duration of Heat Treatment at 100°C on Hardness (HK^qq)

Deposit Phosphorus As-Plated 4 hours 12 hours 1 day 2 days 3 days 9 days Type

No. of

Bath

16 4.5 732 732 111 782 783 783 785 Brenner

34

' .... 611 610 602 1

13 7.1 602 623 631 671 Brenner

15 7.1 592 651 667 Brenner

14 10.1 566 563 565 Brenner

7 11.1 554 558 572 566 Brenner

20 12.5 i; 536 542 580 Brenner
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•

.. TABLE 5

Effect of Duration of Heat Treatment at 400°C on HarcSness (HK,„„)

3posit

No,

Phosphorus

%

As-Plated 1/4 hr. 1/2 hr. 1 hr. 2 hrs. 20 hrs. Type

of

Bath

86 2.8 692 821 812 773 Modified

Brenner

16 . 4.5 732 811 ; 911 923 951 977 Brenner

34 6.8 611 . 782' 852 915 957 967 I 13- 7.1 - 602 921 916 Brenner

19 • 8.7 584 863 890 893 913 Brenner

71 '. 12.1 . 509 845 827 890 766 III

20 ..•12.5 536 959 961 953 961 960 Brenner

57 12.6 568 874 837 845 834 II

60 12.6 524 •862 835 855 831 II
TABLE 6

Effect of Duration of Heat Treatment at 600°C on Hardness (HK,„„)

Deposit Phosphorus As-Plated 1/4 hr. 1/2 hr. 1 hr. 2 hrs. 20 hrs. lype

No . ^ of

Bath

86 2.8 "692 - - 288 290 - Modified

Brenner

16 4.5 732 539 550 602 4lO 408 Brenner

34 6.8 611 715 717 788 652 575 Brenner

42 7.4 551 737 742 794 527 512 I 56 10.1 544 793 802 877 740 64l 1

71 12.1 509 - - 691 - III

20 12.5 536 859 846 865 837 731 Brenner
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I'ABLE 8

Specimens Prepared for Bearre High-Speed Rotor Method of Measuring Adhesion

Substrate

l^bterial

1. 1018 Steel

^1^0 "

2. 1018 Steel

^140 "

3. 1018 Steel

4141 "

A1(N03)3-

HCl pickle

Lactic acidperoxide

solution

Preplate I'reatment

pumice scrub, rinse, A1(N0_^)^-HC1 pickle,

rinse.

pumice scrub, rinse, 1 minute in 50% HpSO^

at 65°C, rinse, 2 minutes in lactic acidperoxide solution at room temperature, rinse.

pumice scrub, rinse, 4 minutes in Al(NO--)^-HCl

pickle at 42°C, rinse, 2 minutes in lactic acidperoxide solution at room tenperature , rinse.

4 minutes in solution of 400 g/1 Al(NO^)^ and

Electroless Nickel

Bath

400 ml/1 cone. HCl.

3^3

15% lactic acid and 80 ml/1 of 30% hiydrogen

peroxide

.
TABii:: 9

Adhesion after various pretreatments.

Pretreatment Adhesion

As-plated After 1 hr. at 400°C

1. As received. VP p

2. Pumice scrub, rinse. P F

3. Pumice scrub, rinse, ^ minutes In A1(N03)3-HC1

pickle, rinse. VP F

4. Pumice scrub, rinse, ^ minutes In A1(N03)3-HC1

pickle at ^2°C, rinse, lactic acid-peroxide

solution rinse. F G

5. Pumice scrub, rinse, H minutes in A1(^D3)3-HC1

pickle at room temperature, rinse, lactic acidperoxide solution, rinse. F G

6. A1(N03)3-HC1 pickle, rinse, lactic acid-peroxide

solution, rinse. F G

7. 1 minute in 50% Hz^i^ at 65°C, rinse, lactic

acid-peroxide solution, rinse. P G

8. 5 minutes in 100 g/1 sodium J-iypxDphosphite at

90°C, rinse. VP F

9. 3 minutes in A1(N03)3-HC1 pickle, rinse, 5

minutes in 100 g/1 sodium Iiypophosphite at

90°C, rinse. P F

10. 1 minute in 40^ H29di, at 65°C, rinse, 30 seconds

in 1% HzSOi^ + 0.1^ HCl at room tenperature, rinse. F P

11. 1 minute in W H2SO4 at 65°C, rinse, 1 minute

in 50% HNO3 at room temperature, rinse, 30 seconds

in 1% H2S04 + 0.1^ Hd at room tenperature, rinse. P G

' A1(N03)3-HC1 pickle: 4 minutes In solution of 400 g/1 A1(N03)3 and 400 m/1

con. HCl at 42°C.
TABLE 10

Wear Tests

Specimen Number of runs

Cycles Per mmType

of

Wheel

Weight loss

mg/1000 cycles

Thickness loss

ym/lOOO cycles

Electroless

nickel

as-plated

5000

2500

5000

CS-10

CS-17

CS-17

9.1

20.6

14.6

0.42

0.95

0.67

Electroless

nickel after

1 hr. at 400°C

5000

2500

5000

CS-10

CS-17

CS-17

7.6

17.0

13.5

0.35

0.78

0.62

Chromium

5000

2500

CS-10

CS-17

2.0

8.4

0.10

0.43

Chromium after

1 hr. at 400°C

5000 CS-10 3.0 0.15
TABI£ 11

. Composition of Electroless

BATH:

Nickel Chloride {6H^0) ^1

Nickel Sulfate (SH^O) g/1

Ethylenedlamine (92%) ml/1

Glycollc Acid g/1

Citric Acid

Sodium Hydroxide g/1

Cone. Hydrochloric Acid ml/1

Amnonium Hydroxide to pH:

pH

Sodium Borohydride g/1

Dimethylajnine Borane g/1

Sodium Cyanoborohydride g/1

lhallium Nitrate mg/1

Lead Acetate mg/1

Mercaptobenzothiozole mg/l

Temperature °C

Nickel-Boron Baths

1 2 3 i 5

30 30 30 - 30 - - - 20 -

65 65 - - 65

- 11.7 -

- - - 10 -

i^O ^0 - - 40

- 25 -

13-14 13-14 5-6 - 13-14

1.0 1.0 - - 0.5

1.0 2,75 -

- - - - 0.15

7.0 100 - - - 20 - -

1.0 -

80 80-95 65 70 90

USCOMM-NBS-OC
Q.

CO

.— 2: 2

2

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Flg^-e 5. Effect of duration of heat treatment at GOO°C on hardness
001 >,H

Figure 8 - Photomicrograph of cross section of brass bolt plated with

electroless nickel in Brenner bath without agitation at

0.6 mil/hr. Overplated with nickel. 90X

Peak to valley thickness ratio is 2.
Figure. 9 - Photomicrograph of cross section of brass bolt plated with

electroless nickel in Bath A without agitation at 0.2 mil/hr.

Overplated with nickel. 90X

Peak to valley thickness ratio is 1.2.
Figure 10 - Photomicrograph of cross section of brass bolt plated with

electroless nickel in Bath A with agitation at 0.6 mil/hr.

Overplated with nickel. 90X

Peak to valley thickness ratio is 1.01.
Figure 11 - Photomicrograph of cross section of 4 mil copper wire plated

with electroless nickel in Bath A with agitation at 0.6 mil/hr.

Overplated with nickel. 470X

Maximum thickness ratio is 1.25.
NBS-114A (REV. 7-73)

U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET

1. PUBLICATION OR REPORT NO.

NBSIR 75-720

2. Gov't Accession

No.

3. Recipient's Accession No.

4. TITLE AND SUBTITLE

Effects of Electroless Nickel Process Variables on

Quality Requirements

5. Publication Date December 1974

6. Performing Organization Code

7. AUTHOR(S)

Fieldinp; Ogburn and Christian E. Johnson

8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Proiect/Task/Work Unit No. .3120^67

11. Contract/Grant No.

12. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP)

Research Directorate

Thomas J. Rodman Laboratory

Rock Island Arsenal

Rock Island, Illinois 60201

13. Type of Report & Period

Covered

FINAL REPORT

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES

16. ABSTRACT (A 200-word or less {actual summary of most si^ilicant intormation. It document includes a significant

bibliography or literature survey, mention it here.)

Deposition rate, phosphorus content, hardness, appearance, and metal

distribution are reported for deposits from several hypophosphite type

electroless nickel baths, both proprietary and non-proprietary. The baths

were operated under a variety of conditions with variations of composition.

Extensive data is given on the relation of deposit hardness to phosphorus

content and to heat treatment at 100, 200, and 400°C. Some data is given

relative to electroless Ni-B, Ni-P-Cu, and Ni-P-Mn alloys.

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name; separated by semicolons) Autocatalytic nickel ; oloctroless nlckol ; electroless nickel

composition; electroless nickel hardness; electroless nickel properties; electraless

plating; hardness of electroless nickel; and nickel-phosphorus alloy.

18. AVAILABILITY [^Unlimited 19. SECURITY CLASS

(THIS REPORT)

21. NO. OF PAGES

1 1 For Official Distribution. Do Not Release to NTIS

UNCL ASSIFIED 47

1 1 Order From Sup. of Doc, U.S. Government Printing Office Washington. D.C. 20402. SD Cat. No. C13

20. SECURITY CLASS

(THIS PAGE)

22. Price

\X. ! Order From National Technical Information Service (NTIS)

Springfield, Virginia 22151 UNCLASSIFIED $3.75

USCOMM-DC 29042-P74