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Autocatalytic deposition of nickel-tin-copper-phosphorus amorphous alloys
0'
Autocatalytic Deposition Nickel-Tin-Copper-Phosphoftls Amorphous Alloys by Zhang Bangweia , Xie Haowenb , and Xu Xiewenc °International Centre of Materials Science, Academia Sinica, Shenyang, P.R. China; bChangsha Communications University, Changsha, P.R. China; and cDepartment of Chemical Engineering, Hunan University, Changsha, P.R. China
ecently, electroless multicomponent alloy deposits have been receiving much attention because the addition of one or two elements into a binary nickel-phosphorus deposit will improve its properties. For example, to obtain a low temperature coefficient of resistance (TCR) tungsten, l chromium,2 or coppe~ can be added into binary deposits. Ternary nickel alloy deposits also have low TCR values; therefore, they are expected to be applied as metal films and thin-film resistors. Besides industrial and technological applications, study of electroless multicomponent alloy deposits can help in understanding the mechanism of electroless plating. Amorphous copper-nickel-tin-phosphorus alloys prepared by splat quenching are a good filler alloy.a.4 The quaternary deposits prepared by electroless plating were, therefore, studied systematically based on the study of electroless ternary nickel-tinphosphorus alloy deposits. This paper describes the preparation technology, composition, and structure of electroless quaternary nickel-tin-copper-phosphorus deposits from a practical and theoretical viewpoint.
R
~1••IInAL
The substrates used are copper or carbon steel sheets 2 X 2 cm, which were cleaned, degreased, and polished with methylbenzene and propanone, and 0.4 M sodium hydroxide solution at 90·C for 10 min. They were then rinsed with deionized water. The basic bath was as follows: 55 gIL NiCI2'6H20; 5 gIL Na2SnOa'3H20; 0.3 gIL CuCI2'5H2 0; 18 gIL NaH 2P02'H20; and 80 gIL NaaC6H507'2H20; with pH of 9 at go·C. Plating time was one hour. All of the chemicals used were analytically pure. When the effect of one composition ofthe bath solution was studied only its content was changed and others were kept constant. The deposition rate was determined by weighing the samples before and after plating. The composition of the film was examined by EDAX analysis. October 1999
The structure was investigated on an X-ray diffractometer with Cu Ka radiation. ......TS AND DUe. . . . . .
Effect of Nickel Chloride The deposition rate was determined by changing the concentration of nickel chloride, which is called Ni series for convenience. The results are shown in Figure 1. One can see that the deposition rate increases with an increase of NiCI 2, but its increase becomes low when the concentration of NiCl 2 rises to a certain value. If the concentration of NiCl 2 is too low the plating rate is very low and no deposit is obtained. Effect of Copper Chloride The effect of copper chloride composition on the deposition rate is shown in Figure 2 (nickel chloride was 40 gIL and the complexing agent was 60 gIL). Now the case is called Cu series for convenience. The results show that the deposition rate increases to a maximum and then decreases with a rise in copper chloride concentration; however, the plating rate is still high enough when CuCl2 is zero, which is different from the Ni series. The increase of metal salt concentration means an increase of metal ions and the ratio of metal ions to reductant increases. The gradually increasing metal ions released from the complexed group of ions are reduced by the electrons produced from sufficient reductant and become neutral atoms. These gradually increasing neutral metal atoms then deposit onto the autocatalyzed substrate, increasing the plating rate; however, the amount of reductant is limited. The released electrons and reduced neutral atoms will decrease; thereby the deposition rate rises to a maximum value and then decreases. Copper is not autocatalyzed but nickel is. When the CuCl 2 content is zero the composition ofthe bath is not changed and, if the NiCl 2 content is high enough, the deposition rate is still high. The deposit 35
10
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40
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80
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o
01--""---...._..1---.......-.....1 o 2 4 e 1 ro
ColllliibldlOh of NlCI. (g/L)
CoIlll1i" lib' 01 Na.IIO. (g/l-)
Figure 1. Effect of nickel chloride concentration on deposition of Ni-Sn-Cu-P deposits.
Figure 3. Effect of sodium stannate concentration on deposition rate of Ni·Sn-eu·p deposits.
is nickel-tin-phosphorus alloy with copper. It is different for the low content of NiCl 2 as no deposit is obtained and the plating rate of course is zero because of the nonautocatalytic nature of copper.
Effect of Sodium Hypophosphite The relationship between deposition rate and reductant sodium hypophosphite concentration is shown in Figure 4. It is called P series for convenience. With increasing NaH 2P0 2 concentration the plating rate increases but the amount of increase gradually decreases. As the reductant increases the reducing ability of the bath increases. In other words the reduced neutral metal atoms and neutral metalloid atoms decomposed from the reducing agent increase. So, the deposition rate increases; however, when the reducing agent is in excess the stability of the bath becomes worse and may decompose.
Effect of Sodium Stannate Figure 3 shows the effect of changing the sodium stannate concentration on the deposition rate. This is called Sn series for convenience. From the beginning the deposition rate decreases with an increase ofsodium stannate, which is different from the effect of other metal salts on the rate. A similar thing was also found by two other authors 5 •6 in electroless ternary nickel-molybdenum-phosphorus deposits, in which the deposition rate also decreased with increase of Na2Mo04' No explanation was given by these authors. It is obvious that the results may come from the precipitation of tin or molybdenum but the mechanism that made the plating rate decrease remains to be researched further. 20..--------------,
OL.....o........_-'-_....L....~ .................__......J o " 1 U 2 U 8 CuniAiollelb1 ofClCl. (g/l)
Figure 2. Effect of copper chloride concentration on deposition rate of Ni·Sn·Cu-P deposits.
36
Effect of Sodium Citrate The effect of complexing agent sodium citrate on the plating rate is shown in Figure 5. The deposition rate decreases with increase of sodium citrate. The effectiveness of adding complexing agent into 10 - - - - - - - - - - - - - - ,
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Figure 4. Effect of sodium hypophosphite concentration on deposition rate of Ni-Sn-Cu-P deposits. Metal Finishing
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Some key findings, supported by text, tables and figures, are: • QUALITY Quality is more Important than price when selecting a supplier. • TECHNICAL SERVICE The most important critenon ,n supplier selection. • HIGH USE OF PROPRIETARY CHEMICALS The maJoney of finishers use proprietary chemicals in preference to "home brews." • PROCESSES WITH HIGHEST EXPECTATIONS FOR GROWTHINJOBSHOPS Electroless copper and electroless nickel plating are expected to show the highest growth. • PROCESS WITH HIGHEST EXPECTATION FOR GROWTH IN CAPTIVE SHOPS Tin-lead plating is expected to show the highest growth over the next tWO years
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FIgure 5. Effect of sodium cltrete concen1ratlon on depoaltlon rete of NI·Sn·Cu·P deposits.
the bath is due to its buffering action because it forms a complex with the metal ions in solution, making the bath stablized. Otherwise, the free metal ions formed would precipitate rapidly causing the bath to be noneffective. In the present case, experiment showed that a deposit could not be formed because of forming precipitates when heating the bath if the complexing agent was less than 60 gIL. When the concentration was higher than that value the deposition rate decreased gradually because excessive complexing agent made metal ions released from the complex decrease successively. That is why the plating rate decreases with increase of complexing agent. When the sodium citrate concentration was higher than 110 gIL the bath on heating became a colloidal solution, making it noneffective.
Effect of pH Value The effect of changing pH value of the bath on the plating rate is shown in Figure 6. The deposition
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FIgure 7. Effect of temperature on depoaltion rete of NI-5n-
eu.p depoaib.
rate approaches a maximum at a pH value of about 8. The deposit is difficult to form when the pH value is less than 5. When it is higher than 12 the deposit could still form but the deposition rate is very small because of a colloidal solution formed. For the bath using NaH2P02 as reductant the reaction equation for deposit of metal nickel atoms can be presented as Ni 2
+ 2H -+ Ni + 2H + or the overall reaction equation as Ni 2
+
(1)
+
+ 2H2 P02 ' + 2Hp-+
Ni + H 2 + 4H + + 2HPOs 2'(2)
(2)
One can see from Equation (1) or (2) that the more the H+ ions in the solution the less the deposit of nickel. When the pH is less than a certain value no deposit forms at all. As the pH is raised the reaction is shifted to the right of the equation. The H+ ions decrease and deposition of nickel increases. After the pH reaches a certain value, here 8, two factors appear and become stronger and stronger as the pH is continuously raised. One is the concentration of free nickel ions becomes low, 7 another is the resulting precipitation of basic salts in the bath consume some nickel ions. Both of these cause the plating rate to increase and that is why the deposition rate results in a maximum at an appropriate pH value.
Effect of Temperature Figure 7 shows the measured results of the effect of temperature on the deposition rate of nickel-tincopper-phosphorus deposits. The plating rate increases with an increase of temperature. It is found for the present case that the nickel-tin-copper-phosphorus deposit is hard to obtain when the temperature is less than 70·C. It is also difficult to form Metal Fln....lng
T.b1e I. Composition .nd Structure of Electrol... Ni-Sn-eu-p Alloy Deposits. Composition In Atomic %
Ni series
Cu series
Sn series
P series
No.a
Ni
Sn
Cu
P
1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 1 2 3 4 5 6
57.40 68.35 80.98 84.49 87.08 90.73 79.55 83.28 69.73 71.78 66.05 63.82 90.02 81.60 82.91 74.09 80.24 84.76 85.45 81.09 78.49 84.18 79.14
11.40 4.65 1.25 1.09 0.32
15.10 5.14 2.45
16.10 21.86 15.32 14.50 9.63 6.43 15.61 11.11 20.86 18.35 15.26 14.19 8.20 15.69 12.26 22.47 11.01 1.66 5.93 9.67 17.79 14.43 20.51
2.14 1.38 1.70 1.26 1.22 1.17 0.49 1.42 1.59 3.66 1.28 1.64 3.75 1.39 1.39 0.35
2.97 2.84 2.70 4.23 7.71 8.61 17.47 20.82 1.78 2.22 3.41 1.85 5.09 12.30 6.98 5.49 2.33
Structure Amorphous Amorphous Amorphous Amorphous Crystalline Crystalline Amorphous AmorphouB Amorphous Amorphous Amorphous Crystalline Crystalline Amorphous Amorphous Amorphous Amorphous Amorphous Amorphous Amorphous Amorphous Amorphous Amorphous
QThe increase of figure in every series indicates increasing the concentration of the changing component of the bath solution. For example No. 1 to 6 in Ni series indicated the NiCl2 concentration increases from 20 to 80 gIL.
because it is hard to control the stability of the bath solution when the temperature is higher than 90·C. At low temperatures the complex metal ions usually cannot release from the complexing group of ions because of a lack of enough energy; therefore, no deposit forms at low temperature. The deposition rate would be very small in that case. The metal ions released from the complexed group of ions increase with increasing temperature so the plating rate increases; however, the tendency of autodecomposition for the bath solution and precipitation from the solution would increase, which causes its stability to worsen as temperature increases.
plating Conditions and Composition The composition ofthe nickel-tin-copper-ph08phorus deposits was determined for the Ni series, Cu series, Sn series, and P series, respectively. The results are shown in Table I. For the Ni series the nickel content increases but copper, tin, and phosphorus basically decrease with increasing NiCl 2 concentration. It is easy to understand because with no change of other conditions the deposited nickel amount increases with increase ofNiCl2 in solution. The nickel content is the main component ofthe deposits so the other contents, of course, decrease. For the Cu series the copper content increases with increasing of CuCl2 but the other three contents decrease. The reasons are basically the same 8S the ones for the effect of NiCI 2· October 1999
For the Sn series the tin content increases with increasing Na2SnOa, which is easy to understand; however, the copper content also increases gradually and the phosphorus content exhibits a maximum with an increase of sodium stannate for which the reasons are not clear. For the P series the phosphorus content increases with increasing NaH 2P02 concentration but the other three contents decrease. When the other components of the bath are not changed the metalloid phosphorus ions released from the reductant increase with increasing NaH 2 P02 concentration. So, the amount of phosphorus atoms increases and the other three components decrease.
Plating Conditions and Structure
Figures 8 to 11 show the X-ray diffraction (XRD)
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90
Figure 8. XRD patterns for NI·Sn-Cu-P depsolts prep.reeI with different NiClz:1. 20; 2. 30; 3. 55; 4. 85; 5. 70; .nd e. 80 gIL. respectively. 31
6
-
5 <4
J
20
2 I
2,
90
Figure 9. XRD patterns for Ni-Sn-eu·p deposits prepared with different CuCla: 1.01; 2. 03; 3. 05; 4. 10; 5. 2.0; and 6.3.0 gIL, respectively.
patterns for the samples of the Ni series, Cu series, Sn series, and P series, respectively. For the Ni series the XRD pattern shows that samples 1 to 4 are typical amorphous structures while samples 5 and 6 are crystalline. For the Cu series, except for sample 6, all are amorphous. For the Sn series sample 5 is crystalline--others are all amorphous. Samples 1 to 6 in the P series are amorphous. In order to verify the effect of adding copper and tin into nickel-phosphorus deposits on their structure, the structure of the binary nickel-phosphorus deposits with different phosphorus contents was also determined. The experimental data indicated that the deposit with phosphorus content higher than 12.53% atomic was amorphous but one with 5 3 2
2,
20
90
Figure 10. XRD patterns for Ni-Sn-Cu-P deposits prepared with different NaaSnOa: 1. 0; 2. 2.5; 3. 5.0; 4. 7.5; and 5. 10 gIL, respectively.
6 5 ~
-
3
-
I
-
20
~
2,
90
Figure 11. XRD patterns for Ni-Sn-Cu-P deposits prepared with different NaHaPOa: 1. 6; 2. 12; 3. 18; 4. 24; 5. 30; and 6. 36 gIL, respectively.
8.03% phosphorus or less was microcrystalline or crystalline. So the critical phosphorus content for producing an amorphous structure is about 9 to 10%. This is similar to the conclusion in the literatureS that the nickel-phosphorus deposits with phosphorus content greater than 9% are amorphous. Sample 1 in the Sn series has more obvious crystallinity than the nickel-phosphorus deposit with 8.03% phosphorus because it has 1.78% copper even though it has somewhat higher phosphorus content (8.2%). Sample 5 in the Ni series with more phosphorus content (9.65%) is crystalline because it has more copper (2.97%). Sample 6 in the Cu series with the phosphorus amount up to 14.19% is still crystalline and not amorphous because of the high content of copper, 20.82%; therefore, the addition of copper into nickel-phosphorus alloy is not favorable for the formation of an amorphous structure. The action of adding tin is just the opposite from that of copper, which is favorable for amorphous formation. This effect is especially obvious for samples 1 and 2 in the P series. Their phosphorus contents are much less than the lower limit of phosphorus content for amorphous formation of binary nickel-phosphorus alloys. Also their copper contents are up to 12.3 and 6.98% but their structures are still amorphous, not crystalline, because they contain 1.28 and 1.65% tin, respectively. How do we understand the favorable and unfavorable effect of tin and copper on the amorphous formation of nickel-phosphorus deposits? Zhang Bangwei et al. 9 and Zhang Heng et al. 10 explained the experimental data of expanding the glass-forming ability for the liquid-quenching ternary alloys by adding nickel into binary copper-phosphorus alloys and for the liquid-quenching quaternary alloys by adding tin into ternary copper-nickel-phosphorus alloys using the formation theory of amorphous alloys proposed by Zhang Bangwei. 11,12 Using the same scheme the present experimental data can also be understood. According to Zhang's formation theory of amorphous alloys the amorphous format ability (AFA) of an alloy can be analyzed. The calculated results show that the AFA of the binary alloys in the quaternary nickel-tin-copper-phosphorus alloy increases according to the following sequence: coppernickel, copper-tin, nickel-phosphorus, copper-tin, tin-phosphorus, and copper-phosphorus. Copper-nickel and nickel-tin are located in the nonforming region. Nickel-phosphorus is an amorphous-forming alloy system but it locates the boundary area between the amorphous-forming and -nonforming region in the map indicating the AFA of it is not strong. After adding copper there are two kinds Metal finishing
I!?',': of interaction-copper-nickel and copper-phosphorus- besides nickel-phosphorus. The AFA of coppernickel is the worst; thereby it must impede the amorphous formation. The interaction of the copperphosphorus bond is the most strong, causing the easy formation of intermediate compound CuaP. It is also favorable for the formation of a crystalline phase; therefore, the addition of copper into nickelphosphorus must hamper the formation ofthe amorphous phase. When adding tin into nickel-phosphorus alloy two new kinds of atomic bond-nickel-tin and tin-phosphorus-are formed. The location of tin-phosphorus in the amorphous-forming region of the map is not deeper than that of copper-phosphorus indicating the tendency of forming an intermediate compound is less than that of copper-phosphorus; therefore, its AFA is strong. Though the nickel-tin is located in the amorphous-nonforming region its ability to promote the formation of a crystalline phase is less than that of copper-nickel. As a whole the effect of adding tin into nickel-phosphorus improves its AFA; therefore, the present experimental data have been explained. .IOG......I. .
Zhang Bangwei is a Professor in the Department of Applied Physics at Hunan University. He was a visiting professor in the Max-Planck-Institute fur Plasmaphysik, West Germany, in 1987 to 1988, and
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senior scientist in the Department of Materials Science at University of Virginia in 1989. Xie Haowen is a Lecturer in the Department of River and Ocean Engineering at Changsha Communications University. He received his MS of Materials Science at Hunan University in 1995. Xu Xiewen is a Master Student in the Department of Chemical Engineering at Hunan University.
....-.c:a
1, Aoki, K. and O. Takano, Plating and Surface Finishing, 77(3):48-52; 1990 2. Iwamatsu, K., Metal Finishing, 87(5):25-27; 1989 3. Datta, A. et a1., Welding Journal, 63(10):14-21; 1984 4. Bangwei, Z. et aI., China Welding, 2(2):95-105; 1993 5. Sheng-Long, L. and L. Han-Hsi, Plating and Surface Finishing, 79(2):56-59; 1992 6. Kaiwa, I. et aI., Journal orthe Electrochemical Society, 135(3):718-2360; 1988 7. Abrantes, L.M. and J.P. Correia, Journal or the Electrochemical Society, 141(9):5356-2360; 1994 8. Raj am, K.S. et aI., Materials and Chemical Physics, 33:289-297; 1993 9. Bangei, Z. et aI., "The Formation Ability and Thermal Properties of Cu-P Based Amorphous Alloys," Proceedings of the 2nd Pacific Rim International Conference on Advanced Materials Processing, Shin, K.S. et a1. (Eds), The Korean Institute of Metals and Materials, p. 1903-1903; 1995 10. Ileng, Z. et aI., Philos. Mag., B66(1):63-75; 1992 11. Bangwei, Z., Physica, 121B:405-408; 1983 12. Bangwei, Z., Physica, 132B:319-322; 1985 MF
Does size really matter? .~~.~,.
..
.
..
There seems 10 be on obsession with size lately, especially with electroless nickel suppliers. With all 01 the recent compony mergers, many EN platers are len wondering .....Is bigger belter?
As the big EN suppliers get bigger, Important croos such as resoorch & development and personal· IZed customer service ore replaced With Ihlngs like morkel shore analysis, acquisition tooms and corporate stock options As compomes merge, whole product lines are o"en eliminated and in some cases, right along With the key people you've come to know and rely on. The ullimole elfecl on you, the plater, IS unreliable service, higher prices and mediocre technology At SIRIUS TECHNOLOGY we aren't concerned about size. We believe irs the linte things thai mo"er. Personalized service thai includes ovemight deliveries, in-house training seminars and immediate response 10 our customers' needs IS where yoU'll Iirst notice a difference. From the meticulous appearance at our shipping containers to Ihe consistent high performance at our MlllENIUM" line at electroless nickel products, our o"enllon to detail IS unmistakable So, does size really malter? At Sirius Technology, we think il does We may be small in size, but we're big In performance and we think you'll agree that thors where we measure up.
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41
Autocatalytic Deposition Nickel-Tin-Copper-Phosphoftls Amorphous Alloys by Zhang Bangweia , Xie Haowenb , and Xu Xiewenc °International Centre of Materials Science, Academia Sinica, Shenyang, P.R. China; bChangsha Communications University, Changsha, P.R. China; and cDepartment of Chemical Engineering, Hunan University, Changsha, P.R. China
ecently, electroless multicomponent alloy deposits have been receiving much attention because the addition of one or two elements into a binary nickel-phosphorus deposit will improve its properties. For example, to obtain a low temperature coefficient of resistance (TCR) tungsten, l chromium,2 or coppe~ can be added into binary deposits. Ternary nickel alloy deposits also have low TCR values; therefore, they are expected to be applied as metal films and thin-film resistors. Besides industrial and technological applications, study of electroless multicomponent alloy deposits can help in understanding the mechanism of electroless plating. Amorphous copper-nickel-tin-phosphorus alloys prepared by splat quenching are a good filler alloy.a.4 The quaternary deposits prepared by electroless plating were, therefore, studied systematically based on the study of electroless ternary nickel-tinphosphorus alloy deposits. This paper describes the preparation technology, composition, and structure of electroless quaternary nickel-tin-copper-phosphorus deposits from a practical and theoretical viewpoint.
R
~1••IInAL
The substrates used are copper or carbon steel sheets 2 X 2 cm, which were cleaned, degreased, and polished with methylbenzene and propanone, and 0.4 M sodium hydroxide solution at 90·C for 10 min. They were then rinsed with deionized water. The basic bath was as follows: 55 gIL NiCI2'6H20; 5 gIL Na2SnOa'3H20; 0.3 gIL CuCI2'5H2 0; 18 gIL NaH 2P02'H20; and 80 gIL NaaC6H507'2H20; with pH of 9 at go·C. Plating time was one hour. All of the chemicals used were analytically pure. When the effect of one composition ofthe bath solution was studied only its content was changed and others were kept constant. The deposition rate was determined by weighing the samples before and after plating. The composition of the film was examined by EDAX analysis. October 1999
The structure was investigated on an X-ray diffractometer with Cu Ka radiation. ......TS AND DUe. . . . . .
Effect of Nickel Chloride The deposition rate was determined by changing the concentration of nickel chloride, which is called Ni series for convenience. The results are shown in Figure 1. One can see that the deposition rate increases with an increase of NiCI 2, but its increase becomes low when the concentration of NiCl 2 rises to a certain value. If the concentration of NiCl 2 is too low the plating rate is very low and no deposit is obtained. Effect of Copper Chloride The effect of copper chloride composition on the deposition rate is shown in Figure 2 (nickel chloride was 40 gIL and the complexing agent was 60 gIL). Now the case is called Cu series for convenience. The results show that the deposition rate increases to a maximum and then decreases with a rise in copper chloride concentration; however, the plating rate is still high enough when CuCl2 is zero, which is different from the Ni series. The increase of metal salt concentration means an increase of metal ions and the ratio of metal ions to reductant increases. The gradually increasing metal ions released from the complexed group of ions are reduced by the electrons produced from sufficient reductant and become neutral atoms. These gradually increasing neutral metal atoms then deposit onto the autocatalyzed substrate, increasing the plating rate; however, the amount of reductant is limited. The released electrons and reduced neutral atoms will decrease; thereby the deposition rate rises to a maximum value and then decreases. Copper is not autocatalyzed but nickel is. When the CuCl 2 content is zero the composition ofthe bath is not changed and, if the NiCl 2 content is high enough, the deposition rate is still high. The deposit 35
10
{
8
!
8
r--------------,
20.-----------.
I
o
I: / 2Il
40
eo
80
100
o
01--""---...._..1---.......-.....1 o 2 4 e 1 ro
ColllliibldlOh of NlCI. (g/L)
CoIlll1i" lib' 01 Na.IIO. (g/l-)
Figure 1. Effect of nickel chloride concentration on deposition of Ni-Sn-Cu-P deposits.
Figure 3. Effect of sodium stannate concentration on deposition rate of Ni·Sn-eu·p deposits.
is nickel-tin-phosphorus alloy with copper. It is different for the low content of NiCl 2 as no deposit is obtained and the plating rate of course is zero because of the nonautocatalytic nature of copper.
Effect of Sodium Hypophosphite The relationship between deposition rate and reductant sodium hypophosphite concentration is shown in Figure 4. It is called P series for convenience. With increasing NaH 2P0 2 concentration the plating rate increases but the amount of increase gradually decreases. As the reductant increases the reducing ability of the bath increases. In other words the reduced neutral metal atoms and neutral metalloid atoms decomposed from the reducing agent increase. So, the deposition rate increases; however, when the reducing agent is in excess the stability of the bath becomes worse and may decompose.
Effect of Sodium Stannate Figure 3 shows the effect of changing the sodium stannate concentration on the deposition rate. This is called Sn series for convenience. From the beginning the deposition rate decreases with an increase ofsodium stannate, which is different from the effect of other metal salts on the rate. A similar thing was also found by two other authors 5 •6 in electroless ternary nickel-molybdenum-phosphorus deposits, in which the deposition rate also decreased with increase of Na2Mo04' No explanation was given by these authors. It is obvious that the results may come from the precipitation of tin or molybdenum but the mechanism that made the plating rate decrease remains to be researched further. 20..--------------,
OL.....o........_-'-_....L....~ .................__......J o " 1 U 2 U 8 CuniAiollelb1 ofClCl. (g/l)
Figure 2. Effect of copper chloride concentration on deposition rate of Ni·Sn·Cu-P deposits.
36
Effect of Sodium Citrate The effect of complexing agent sodium citrate on the plating rate is shown in Figure 5. The deposition rate decreases with increase of sodium citrate. The effectiveness of adding complexing agent into 10 - - - - - - - - - - - - - - ,
-'"""""-.....1__.....
01-_.....
o
,
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411
Coo lllIi "alb i of NaH.PO. (gft.)
Figure 4. Effect of sodium hypophosphite concentration on deposition rate of Ni-Sn-Cu-P deposits. Metal Finishing
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Some key findings, supported by text, tables and figures, are: • QUALITY Quality is more Important than price when selecting a supplier. • TECHNICAL SERVICE The most important critenon ,n supplier selection. • HIGH USE OF PROPRIETARY CHEMICALS The maJoney of finishers use proprietary chemicals in preference to "home brews." • PROCESSES WITH HIGHEST EXPECTATIONS FOR GROWTHINJOBSHOPS Electroless copper and electroless nickel plating are expected to show the highest growth. • PROCESS WITH HIGHEST EXPECTATION FOR GROWTH IN CAPTIVE SHOPS Tin-lead plating is expected to show the highest growth over the next tWO years
The fifth report prepared by the Surface Finishing Market Research Board (SFMRB) is the most comprehensive to date. Not only does it confirm and update data in some of the previous reports, it provides important new information on purchasing practices, technology trends and sludge disposal. Report #5 is 82 pages in length, with 125 tables and figures. The work undertaken by the SFMRB since its establishment in 1993 attempts to fill a previous void: the lack of accessible marketing information on the surface finishing industry. The SFMRB is composed of representatives of the following sponsoring organizations: the National Association of Metal Finishers (NAMF). the Metal Finishing Suppliers Association (MFSA) and the American Electroplaters and Surface Finishers Society (AESF). The level of cooperation among these three organizations as well as the support of trade publications (Products Fmlshing. Metal Finishing. Finishers' Management, and Platmg and Surface Finishing) on SFMRB projects has steadily increased. and the size and scope of the surveys reflect that effort. The SFMRB surveys the surface finishing industry annually in accordance with mutually agreed-on directives from the sponsors. The cost of Report #S is $125 for members of the sponsoring organizations and $250 for non-members. Computer disk (includes report) $495 for member/non·member. The report
• F006 RECYCLING ApprOXimately 40 percent of finishing shops send their F006 sludge out for recycling.
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• TOP SUBSTRATES Carbon steel and stainless steel substrates, followed by aluminum and aluminum alloys. • F006 DISPOSAL The average finishing shop disposes of 23.2 tons/yr of F006 charactenstlc waste sludge.
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FIgure 5. Effect of sodium cltrete concen1ratlon on depoaltlon rete of NI·Sn·Cu·P deposits.
the bath is due to its buffering action because it forms a complex with the metal ions in solution, making the bath stablized. Otherwise, the free metal ions formed would precipitate rapidly causing the bath to be noneffective. In the present case, experiment showed that a deposit could not be formed because of forming precipitates when heating the bath if the complexing agent was less than 60 gIL. When the concentration was higher than that value the deposition rate decreased gradually because excessive complexing agent made metal ions released from the complex decrease successively. That is why the plating rate decreases with increase of complexing agent. When the sodium citrate concentration was higher than 110 gIL the bath on heating became a colloidal solution, making it noneffective.
Effect of pH Value The effect of changing pH value of the bath on the plating rate is shown in Figure 6. The deposition
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FIgure 7. Effect of temperature on depoaltion rete of NI-5n-
eu.p depoaib.
rate approaches a maximum at a pH value of about 8. The deposit is difficult to form when the pH value is less than 5. When it is higher than 12 the deposit could still form but the deposition rate is very small because of a colloidal solution formed. For the bath using NaH2P02 as reductant the reaction equation for deposit of metal nickel atoms can be presented as Ni 2
+ 2H -+ Ni + 2H + or the overall reaction equation as Ni 2
+
(1)
+
+ 2H2 P02 ' + 2Hp-+
Ni + H 2 + 4H + + 2HPOs 2'(2)
(2)
One can see from Equation (1) or (2) that the more the H+ ions in the solution the less the deposit of nickel. When the pH is less than a certain value no deposit forms at all. As the pH is raised the reaction is shifted to the right of the equation. The H+ ions decrease and deposition of nickel increases. After the pH reaches a certain value, here 8, two factors appear and become stronger and stronger as the pH is continuously raised. One is the concentration of free nickel ions becomes low, 7 another is the resulting precipitation of basic salts in the bath consume some nickel ions. Both of these cause the plating rate to increase and that is why the deposition rate results in a maximum at an appropriate pH value.
Effect of Temperature Figure 7 shows the measured results of the effect of temperature on the deposition rate of nickel-tincopper-phosphorus deposits. The plating rate increases with an increase of temperature. It is found for the present case that the nickel-tin-copper-phosphorus deposit is hard to obtain when the temperature is less than 70·C. It is also difficult to form Metal Fln....lng
T.b1e I. Composition .nd Structure of Electrol... Ni-Sn-eu-p Alloy Deposits. Composition In Atomic %
Ni series
Cu series
Sn series
P series
No.a
Ni
Sn
Cu
P
1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 1 2 3 4 5 6
57.40 68.35 80.98 84.49 87.08 90.73 79.55 83.28 69.73 71.78 66.05 63.82 90.02 81.60 82.91 74.09 80.24 84.76 85.45 81.09 78.49 84.18 79.14
11.40 4.65 1.25 1.09 0.32
15.10 5.14 2.45
16.10 21.86 15.32 14.50 9.63 6.43 15.61 11.11 20.86 18.35 15.26 14.19 8.20 15.69 12.26 22.47 11.01 1.66 5.93 9.67 17.79 14.43 20.51
2.14 1.38 1.70 1.26 1.22 1.17 0.49 1.42 1.59 3.66 1.28 1.64 3.75 1.39 1.39 0.35
2.97 2.84 2.70 4.23 7.71 8.61 17.47 20.82 1.78 2.22 3.41 1.85 5.09 12.30 6.98 5.49 2.33
Structure Amorphous Amorphous Amorphous Amorphous Crystalline Crystalline Amorphous AmorphouB Amorphous Amorphous Amorphous Crystalline Crystalline Amorphous Amorphous Amorphous Amorphous Amorphous Amorphous Amorphous Amorphous Amorphous Amorphous
QThe increase of figure in every series indicates increasing the concentration of the changing component of the bath solution. For example No. 1 to 6 in Ni series indicated the NiCl2 concentration increases from 20 to 80 gIL.
because it is hard to control the stability of the bath solution when the temperature is higher than 90·C. At low temperatures the complex metal ions usually cannot release from the complexing group of ions because of a lack of enough energy; therefore, no deposit forms at low temperature. The deposition rate would be very small in that case. The metal ions released from the complexed group of ions increase with increasing temperature so the plating rate increases; however, the tendency of autodecomposition for the bath solution and precipitation from the solution would increase, which causes its stability to worsen as temperature increases.
plating Conditions and Composition The composition ofthe nickel-tin-copper-ph08phorus deposits was determined for the Ni series, Cu series, Sn series, and P series, respectively. The results are shown in Table I. For the Ni series the nickel content increases but copper, tin, and phosphorus basically decrease with increasing NiCl 2 concentration. It is easy to understand because with no change of other conditions the deposited nickel amount increases with increase ofNiCl2 in solution. The nickel content is the main component ofthe deposits so the other contents, of course, decrease. For the Cu series the copper content increases with increasing of CuCl2 but the other three contents decrease. The reasons are basically the same 8S the ones for the effect of NiCI 2· October 1999
For the Sn series the tin content increases with increasing Na2SnOa, which is easy to understand; however, the copper content also increases gradually and the phosphorus content exhibits a maximum with an increase of sodium stannate for which the reasons are not clear. For the P series the phosphorus content increases with increasing NaH 2P02 concentration but the other three contents decrease. When the other components of the bath are not changed the metalloid phosphorus ions released from the reductant increase with increasing NaH 2 P02 concentration. So, the amount of phosphorus atoms increases and the other three components decrease.
Plating Conditions and Structure
Figures 8 to 11 show the X-ray diffraction (XRD)
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Figure 8. XRD patterns for NI·Sn-Cu-P depsolts prep.reeI with different NiClz:1. 20; 2. 30; 3. 55; 4. 85; 5. 70; .nd e. 80 gIL. respectively. 31
6
-
5 <4
J
20
2 I
2,
90
Figure 9. XRD patterns for Ni-Sn-eu·p deposits prepared with different CuCla: 1.01; 2. 03; 3. 05; 4. 10; 5. 2.0; and 6.3.0 gIL, respectively.
patterns for the samples of the Ni series, Cu series, Sn series, and P series, respectively. For the Ni series the XRD pattern shows that samples 1 to 4 are typical amorphous structures while samples 5 and 6 are crystalline. For the Cu series, except for sample 6, all are amorphous. For the Sn series sample 5 is crystalline--others are all amorphous. Samples 1 to 6 in the P series are amorphous. In order to verify the effect of adding copper and tin into nickel-phosphorus deposits on their structure, the structure of the binary nickel-phosphorus deposits with different phosphorus contents was also determined. The experimental data indicated that the deposit with phosphorus content higher than 12.53% atomic was amorphous but one with 5 3 2
2,
20
90
Figure 10. XRD patterns for Ni-Sn-Cu-P deposits prepared with different NaaSnOa: 1. 0; 2. 2.5; 3. 5.0; 4. 7.5; and 5. 10 gIL, respectively.
6 5 ~
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-
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-
20
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2,
90
Figure 11. XRD patterns for Ni-Sn-Cu-P deposits prepared with different NaHaPOa: 1. 6; 2. 12; 3. 18; 4. 24; 5. 30; and 6. 36 gIL, respectively.
8.03% phosphorus or less was microcrystalline or crystalline. So the critical phosphorus content for producing an amorphous structure is about 9 to 10%. This is similar to the conclusion in the literatureS that the nickel-phosphorus deposits with phosphorus content greater than 9% are amorphous. Sample 1 in the Sn series has more obvious crystallinity than the nickel-phosphorus deposit with 8.03% phosphorus because it has 1.78% copper even though it has somewhat higher phosphorus content (8.2%). Sample 5 in the Ni series with more phosphorus content (9.65%) is crystalline because it has more copper (2.97%). Sample 6 in the Cu series with the phosphorus amount up to 14.19% is still crystalline and not amorphous because of the high content of copper, 20.82%; therefore, the addition of copper into nickel-phosphorus alloy is not favorable for the formation of an amorphous structure. The action of adding tin is just the opposite from that of copper, which is favorable for amorphous formation. This effect is especially obvious for samples 1 and 2 in the P series. Their phosphorus contents are much less than the lower limit of phosphorus content for amorphous formation of binary nickel-phosphorus alloys. Also their copper contents are up to 12.3 and 6.98% but their structures are still amorphous, not crystalline, because they contain 1.28 and 1.65% tin, respectively. How do we understand the favorable and unfavorable effect of tin and copper on the amorphous formation of nickel-phosphorus deposits? Zhang Bangwei et al. 9 and Zhang Heng et al. 10 explained the experimental data of expanding the glass-forming ability for the liquid-quenching ternary alloys by adding nickel into binary copper-phosphorus alloys and for the liquid-quenching quaternary alloys by adding tin into ternary copper-nickel-phosphorus alloys using the formation theory of amorphous alloys proposed by Zhang Bangwei. 11,12 Using the same scheme the present experimental data can also be understood. According to Zhang's formation theory of amorphous alloys the amorphous format ability (AFA) of an alloy can be analyzed. The calculated results show that the AFA of the binary alloys in the quaternary nickel-tin-copper-phosphorus alloy increases according to the following sequence: coppernickel, copper-tin, nickel-phosphorus, copper-tin, tin-phosphorus, and copper-phosphorus. Copper-nickel and nickel-tin are located in the nonforming region. Nickel-phosphorus is an amorphous-forming alloy system but it locates the boundary area between the amorphous-forming and -nonforming region in the map indicating the AFA of it is not strong. After adding copper there are two kinds Metal finishing
I!?',': of interaction-copper-nickel and copper-phosphorus- besides nickel-phosphorus. The AFA of coppernickel is the worst; thereby it must impede the amorphous formation. The interaction of the copperphosphorus bond is the most strong, causing the easy formation of intermediate compound CuaP. It is also favorable for the formation of a crystalline phase; therefore, the addition of copper into nickelphosphorus must hamper the formation ofthe amorphous phase. When adding tin into nickel-phosphorus alloy two new kinds of atomic bond-nickel-tin and tin-phosphorus-are formed. The location of tin-phosphorus in the amorphous-forming region of the map is not deeper than that of copper-phosphorus indicating the tendency of forming an intermediate compound is less than that of copper-phosphorus; therefore, its AFA is strong. Though the nickel-tin is located in the amorphous-nonforming region its ability to promote the formation of a crystalline phase is less than that of copper-nickel. As a whole the effect of adding tin into nickel-phosphorus improves its AFA; therefore, the present experimental data have been explained. .IOG......I. .
Zhang Bangwei is a Professor in the Department of Applied Physics at Hunan University. He was a visiting professor in the Max-Planck-Institute fur Plasmaphysik, West Germany, in 1987 to 1988, and
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senior scientist in the Department of Materials Science at University of Virginia in 1989. Xie Haowen is a Lecturer in the Department of River and Ocean Engineering at Changsha Communications University. He received his MS of Materials Science at Hunan University in 1995. Xu Xiewen is a Master Student in the Department of Chemical Engineering at Hunan University.
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1, Aoki, K. and O. Takano, Plating and Surface Finishing, 77(3):48-52; 1990 2. Iwamatsu, K., Metal Finishing, 87(5):25-27; 1989 3. Datta, A. et a1., Welding Journal, 63(10):14-21; 1984 4. Bangwei, Z. et aI., China Welding, 2(2):95-105; 1993 5. Sheng-Long, L. and L. Han-Hsi, Plating and Surface Finishing, 79(2):56-59; 1992 6. Kaiwa, I. et aI., Journal orthe Electrochemical Society, 135(3):718-2360; 1988 7. Abrantes, L.M. and J.P. Correia, Journal or the Electrochemical Society, 141(9):5356-2360; 1994 8. Raj am, K.S. et aI., Materials and Chemical Physics, 33:289-297; 1993 9. Bangei, Z. et aI., "The Formation Ability and Thermal Properties of Cu-P Based Amorphous Alloys," Proceedings of the 2nd Pacific Rim International Conference on Advanced Materials Processing, Shin, K.S. et a1. (Eds), The Korean Institute of Metals and Materials, p. 1903-1903; 1995 10. Ileng, Z. et aI., Philos. Mag., B66(1):63-75; 1992 11. Bangwei, Z., Physica, 121B:405-408; 1983 12. Bangwei, Z., Physica, 132B:319-322; 1985 MF
Does size really matter? .~~.~,.
..
.
..
There seems 10 be on obsession with size lately, especially with electroless nickel suppliers. With all 01 the recent compony mergers, many EN platers are len wondering .....Is bigger belter?
As the big EN suppliers get bigger, Important croos such as resoorch & development and personal· IZed customer service ore replaced With Ihlngs like morkel shore analysis, acquisition tooms and corporate stock options As compomes merge, whole product lines are o"en eliminated and in some cases, right along With the key people you've come to know and rely on. The ullimole elfecl on you, the plater, IS unreliable service, higher prices and mediocre technology At SIRIUS TECHNOLOGY we aren't concerned about size. We believe irs the linte things thai mo"er. Personalized service thai includes ovemight deliveries, in-house training seminars and immediate response 10 our customers' needs IS where yoU'll Iirst notice a difference. From the meticulous appearance at our shipping containers to Ihe consistent high performance at our MlllENIUM" line at electroless nickel products, our o"enllon to detail IS unmistakable So, does size really malter? At Sirius Technology, we think il does We may be small in size, but we're big In performance and we think you'll agree that thors where we measure up.
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October 1999
SIRIUS TECHNOLOGY, INC. Supplierof EleclrolessNickel and Relaled Metal FinishingProducts PO. Box 751 • 132 Clear Rood' Oriskany, NY 13424 Tel: 315.768.6635.· Fox: 315.768.3561 • www.sirius-lech.com
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