Guest Editorial -For Plateworld.com                                                 

 Don Baudrand, Don Baudrand Consulting,   e-mail:donwb@tscnet.com

 

Troubleshooting Plating on Plastics

 Don Baudrand, CEF and Ned Mandich PhD, CEF

Abstract

The brief historical development and basic chemical steps for metallizing of conductors in general and plating on ABS plastics in particular are offered. However, the main emphasis is directed toward presentation of comprehensive troubleshooting guide where main technical problems encountered in one preset day plating on plastic plant are detailed . The possible causes of plating defects and solutions of the problems are elaborated.

INTRODUCTION

The ancient alchemists in their biblical teachings record the deposition of metals on other metals. However, as time went on, newer metals and materials were found, and the need for finishing them in different effects or colors to suit the individual requirements soon presented a new field for search and activity. Particularly so is the case in which metals had to deposited on insulating materials for new fields or industries, for instance in the case of electrotyping, where a wax impression of type matter is reproduced in metal so that it may be used as a printing medium itself. The museums of the larger cities have on exhibition examples of metallized wood and terra-cotta made by the Egyptians. This was done only for decorative purposes.

About the earliest recorded method for mold making is accredited to H. Jacobi1 who, in 1837, deposited metals on wax, and subsequently stripped (separated) them., About the same time, Alexander Parks2 was granted a patent for metallizing animals, insects, flowers and fruits by the application of a silver nitrate solution. The silver nitrate formed a part of many other processes, which varied simply in their methods of application. For example, a patent obtained by Noualheir and Provost3 in January, 1857, described the metallization of a soft surface such as a human corpse by placing the body in a suitable attitude and spreading pulverized silver nitrate over it with a brush; then electroplating it in a copper sulphate bath, thus producing a copper plated mummy.

Electroless plating began almost as soon as modern electroplating4. The first description by von Liebig5 in 1835 was the reduction of silver salts by reducing aldehydes. Despite its early start, progress in this field remained slow until W W II.

Modern electroless plating began in 1944 when Brenner and Riddell6,7 rediscovered that hypophosphite could cause nickel deposition. Their subsequent work led to the first patents on commercially usable electroless nickel (ElNi) solutions. Although early solutions were very useful for coating metals, they could not be used on most plastics because their operating temperature was 90-100 0 C. The first electroless nickel solution capable of wide use on plastics was introduced in 19667 as it could operate at room temperature and was extremely stable.

Electroless copper (ElCu) solutions underwent a similar development during the same period8. Most commonly plated plastic, ABS, deforms at the temperatures above 65 0C. This prompted the use of the low temperatures ElCu solutions, but these solutions were several orders of magnitude less stable than room temperature El Ni solutions.

General interest in electroless plating grew as it was shown that uniformity of deposition was very high. This eliminated any high and low current density complications, customized anodes, and special plating fixtures needed with the use of electrolytic plating. The lack of a need for electrical continuity made electroless baths an ideal solution to the problem of plating on plastics (PoP) and plating unconnected metal areas on printed circuit boards (PCB).

RATIONALE

PROCESS. The typical PoP process is presented in Table 1.( Nota Bene: For the reasons of simplicity , necessary rinsing steps are omitted). It consists of the following sequences: preplating steps; etching, etch neutralization, catalyst application, catalyst activation, and electroplating plating step. Most commercial applications, except RFI/EMI shielding, use the initial electroless deposit as a base for subsequent electrolytic plating. The initial copper or nickel layer is coated with successive layers of electrolytic copper, nickel, and chromium. The exact types and thickness of metal used are determined by the end use of the part, e.g., automotive exterior, decorative, plumbing, and others9.

TABLE 1. Typical Plating on Plastics Processing Cycle Outline

STEP

SOLUTION FUNCTION

Alkaline soak cleaning-optional

Removes shop oils, fingerprints, etc.

Pre-Etchant

Promotes Etching

Etchant

Promotes Surface for Adhesion

Neutralizer

Removes Residual Etchant

Catalyst

Deposits Tin-Palladium Layer

Accelerator

Activates Catalyst

Electroless plating

For PoP, nickel or copper, for FRI, copper.

Electrolytic plating

For PoP, copper, nickel or chromium

Rack stripping

Prevents plating on the plating racks and fixtures

Chemistry. Successful POP preplating step depends on the optimized interaction of separate complex chemical solutions10, 11 which have a function to clean, roughen, and catalyze the surface before plating. These steps are critical for formation of an adherent continuous electroless coating and for optimum durability after electrolytic plating.

Etching. This crucial step is necessary to give best possible adhesion of metal to plastic. For plating of ABS plastic substrates, solutions of strongly oxidizing chromic acid-sulfuric acid-water or chromic acid-water are operated near the point of mutual saturation. The etchant both physically roughens the surface and chemically modifies it to give a very hydrophilic surface. Metal adhesion occurs owing to the combined effects of chemical bonding and mechanical locking to the roughened surface. In the etching of ABS plastic, a polymer consisting of polybutadiene spheroids dispersed in a continuous phase of poly (styrene-acrylonitrile), the chromic acid attacks the polybutadiene at a much higher rate than the continuous phase. This gives an excellent micoroughened surface with superior metal-to-plastic bond strength. A typical recommended formulation consists of 20 vol. % sulfuric acid, 420 g/L chromic acid, and 0.1-1.0% of a fluorocarbon wetting agent. The plastic is treated with this formulation for 6-10 min at 60-65°C. In some situations, separate, per-etch, swelling step is introduced in order to prepare plastic or other platable non-conductors for better, more uniform etching12.

Neutralizing. Residual hexavalent chromium is removed from the surface of the part. Hexavalent chromium shortens the life of the catalyst, and trace amounts completely inhibit electroless nickel deposition. The neutralizer is usually a mildly acidic or basic reducing agent, but other types of neutralizers are available especially for substrates that are difficult to plate. The neutralizer may also contain surfactants or other compounds that increase catalyst absorption; absorption promoters are often needed for non-ABS plastics.

Catalysis. Covering of the prepared plastic surface with thin layer of highly conductive metal layer is done by an acidic solution of the stabilized reaction product of stannous chloride and palladium chloride. The older, almost obsolete, two-step process consisted of separate hydrochloric acid solutions of tin (sensitizer) and palladium (activator) chlorides but is now rarely used except in special applications. Catalyst absorption is typically in order of 1-5 µg Pd/cm². Other precious metals can be used, but they are not as cost-effective. The exact chemical identity of this catalyst has been a matter of considerable scientific interest13-22. It seems to be a stabilized colloid, codeposited on the plastic with excess tin. The industry trends have been to use higher activity catalysts at lower concentrations and higher temperatures. Current typical usage is 40-150 ppm of palladium at 60°C maximum with a 30-60 fold or more excess of stannous chloride. Catalyst variations occasionally used include alkaline and non-noble metal catalysts23.

Acceleration. After catalization, the plastic surface is covered with a layer of palladium nuclei, and stannous and stannic hydrous oxides and oxychlorides. The activation step is needed to remove excess tin from the catalyzed surface which would inhibit electroless plating. It also exposes the active palladium sites and removes loose palladium, which can de-stabilize the bath. It can be done by any acid or alkaline solution in which excess tin is appreciably soluble and catalytic palladium nuclei become exposed. Accelerators can be any acidic or alkaline solution, which solubilizes excess tin.

Electroless plating. This step provides continuous surface layer of metal, in either copper or nickel form. A number of papers have indicated that copper may be better for corrosion resistance24-26 . Although the electroless copper plating systems are similar to those used in printed circuit processing, electroless nickel processes differ greatly from those used in metal plating and are not interchangeable. Room temperature nickel solutions are mildly alkaline and give a low and uniform deposition rate. At present, automotive and other heavy-duty applications use copper, whereas decorative and interior articles are often plated with nickel.

Radio frequency interference (also known as Electromagnetic interference, RFI/EMI) shielding applications use nickel-phosphorus for low shielding requirements or a copper layer coated with nickel or other metal for high shielding 27-28.

Room temperature electroless nickel systems are easily controlled and replenished with indefinite bath lives29-35. Electroless copper solutions can approach these bath lives when carefully controlled. As only thin metal layers are deposited, the drag-out losses can be comparable to the actual usage of metal in plating. This drag-out helps bath stability by keeping the reaction products from building up36.

A 0.15-0.5 mm thick layer can be obtained with plating time of 5-20 minutes. That thickness allows the parts to be further processed in the electroplating step, as though it were totally metallic. Plated parts, except those needing RFI/EMI shielding, are electroplated with multiple layers of copper, nickel, and chromium. Precautions must be taken to control the initial current during electroplating or the thin film may overheat and burn off. A nickel or copper strike is usually applied first, followed by any desired decorative or functional coating. Electroless solutions are not generally use for the build-up of metal (due to the high cost relative to electroplating solutions) but only to provide the sufficient surface conductivity of the part37-43.

Special stop-off paints are commonly applied to the backs or large auto parts, such as grills, to confine metal plating to appearance surfaces only. Types and thicknesses of coatings depend on the end use of the part. They range from 22-25 mm total Cu + Ni + Cr for mild service conditions to 25-45 mm for more severe conditions. Recommended minimum electroplate thickness for a bright chromium finish are: bright acid copper, 15 mm, semi bright nickel, 20-30 mm or bright nickel, 7-15 mm; and chromium 0.25 mm (ASTM B604-75).

With all technical improvements that occurred in last 30 years, it must be clear that preparation of plastics and non-conductors for plating will be always inherently more complex, than it is preparing of a platable metal. This is early recognized by the experienced practitioners44-47.

TROUBLESHOOTING. Determining the causes of PoP imperfections, flaws, and miscellaneous defects is far from being easy or clear-cut. The main reason for this is the that in most cases the defect is seen only on the finished product, i.e. after plating is completed. Moreover, many plating defects look alike superficially and it requires considerable experience before accurate diagnosis can implemented and right cure can be administer.

On the whole, it is possible to distinguish between defects, which are due to the material itself, and/or the manufacturing of the part and defects, which are due to the plating operation. The remedies for the first are of course, to be sought in changes in the material or it’s manufacturing. Today, these defects account for by far the highest proportion of rejected parts. This subject will be further discussed and finally presented in a form of comprehensive Troubleshooting Chart.

If both the manufacturing and the plating are done in the same plant, and this is always to be recommended, the management should leave the supervision of both processes to the same person, otherwise the responsibility for defects will not be accepted by either department, a situation that is never in the interests of the company as a whole.

The manufacturer of molded plastics parts (molder) must have sufficient understanding of the electroplater’s difficulties to support the electroplater in the search for causes of trouble, and he must be sufficiently self-critical to accept the need for changes in his own department where necessary.

It often happens that defects, which are due to faults in the material and/or in manufacturing, do not appear until the part has been treated in pre-plating step and is ready for electroplating step. When the plant is running at full capacity, such faults may be overlooked until plating rejects draw attention to them.

To determine whether or not the cause of plating lies in the plastic material itself, it is necessary to proceed systematically 45. The first step is to investigate a part that has been micro-roughened in etching step and then allowed to dry. A microscope may be required for this purpose. If no defect is established at this stage, the surface of the part is blackened with graphite to help to make faults visible. If this does not reveal any defects, the metal coating is removed from a plated component. If the defect is actually in the plastic itself, it is certain to appear at this stage, otherwise it will lie somewhere in the pre-plating or electroplating steps. The virgin unfinished plastic parts can be examined only for gross defects such as cavities, sinks, flow-lines, etc., as their lack of specular surface reflectivity hides any finer faults.

If it is definite that the defect is due to the plastic material or the manufacturing (molding) process, it is more often than not, relatively easy to determine the remedy. Almost all plastics manufacturers have trained technical service engineers who are available to assist the manufactures. Moreover, the instructions, which accompany the individual plastics materials normally, contain sufficient information on possible sources of defects for the fabricator to diagnose any troubles himself.

Inherently it is a good deal more intricate when the parts are not finished in the same plant where they are produced. In this case it is vital for the electroplater to adopt an exact written specification for the quality of the parts supplied for plating, and it is essential that the outside manufacturer diligently follow this specification . There is no point at all in electroplating poor or badly molded material, as the finishing process can never hide the defects in the latter.

CONCLUSION

The preceding troubleshooting approach is not intended to be indicative of a unique method of problem solving. Nor it is a remedy for all problems that can occur in present day treatment of plating on different kinds of platable plastic in a modern plant. It is only an effort to explain after many years of practical, production experience a troubleshooting method which is as applicable as any, and hopefully better than most. Another processes may call for more or less different approach to the given problems, and hence their solutions. The main difference is surface conditioning-etching step. The procedures as outlined above, is presented as a remedial effort to a specific problem, of plating of ABS plastic. However, this troubleshooting scheme should not significantly wary for plating of different kinds of plastic and the employment of such a process.

The above problems are a synopsis of most of the normal plating difficulties, which may be encountered in a bay to day plating on plastic operation. Proper attention to management, maintenance, and manpower will keep this operation protective, decorative, profitable operation that it should be.


REFERENCES

1. B. S. Jacobi, “Raboty po electrokhimii”, (Works on Electrochemistry), Izdatelstvo AN SSSR, Moscow (1957).

2. A. Parks, in S. Wein: ”Metallizing of Nonconductors”, Industrial Publ. Co, NY (1945).

3. Nouhauler and Provost, ibid

4. "The Industrial Revolution" in C. Singer and co-eds. "History of Technology,” Vol. 4, Oxford University Press, New York, (1958).

5. J. von Liebig, US Patent, 33,721 (Nov. 1861).

6. A. Brenner and G. Riddell (to U.S. Government), U.S. Patent 2, 532,283 (1950).

7. A. Brenner, Plating Surf. Finish.,71(7) 24 (1984).

8. E.B. Saubestre, Plating, 59(6) 563 (1972).

9. American Society of Electroplated Plastics, "Standards and Guidelines for Electroplated Plastics", 3rd Ed, Prentice-Hall, Englewood Cliffs, NJ, (1984).

10. G.A. Krulik, J. Chem. Ed., 55, 361 (1978).

11. N.V. Mandich, Plating Surf. Finish., 80, (11), 68 (1993).

12. N.V .Mandich, Trans. Inst. Met. Finish., 72, (1), 41 (1994).

13. G.A. Krulik, Platinum Met. Rev., 26, 58 (1982).

14. N. V. Mandich and G. A. Krulik, Plat. Surf. Finish.,80,(12)68 (1993).

15. E. Matijevic, A.M. Poskanzer and P. Zuman, Plat. Surf.Finish.,62,(10)958 (1975).

16. G.A. Krulik, J. Catal., 6, (5), 95 (1980).

17. N. V. Mandich, Plat. Surf. Finish. 78(12) 50 (1991).

18. N. V. Mandich and G. A. Krulik, Trans. Inst. Met. Finish. 70 (3) 111 (1992).

19. N. V. Mandich and G. A. Krulik, Trans. Inst. Met. Finish.,70 (3) 117 (1992).

20. C. R. Shipley, U.S. Patent 3,001.920 (1963)

21. R. L. Cohen and K. W. West, J. Electroch. Soc., 120 (4) 502 (1973).

22. J. Horkans, ibid, 130(2) 311(1983)

23. N. Pearlstein, US Patents, 4,087.586(1972) and 4, 132.832 (1972).

24. G. A. DiBari and R. L. Coombs, Prod. Finish., 41(4)54(1977).

25. R.G. Wedel, Int. Met. Rev., 217, 97 (1977).

26. G. O. Mallory, Plating, 61(11), 1005 (1974).

27. J. Hajdu and G.A. Krulik, "Plating Surf. Finish., 70,(7 ) 42 (1983); G.A. Krulik, ibid, 71,(12 ) 56 (1984).

28. N. V. Mandich, Plat. Surf. Finish.,81(9)60(1994).

29. N. V. Mandich and D. Tuomi, Trans. Inst. Met. Finish., 72, (2), 72 (1994).

30. G. A. Krulik and N. V. Mandich, US Patents, 5,212.138 (1993), 5,219.815 (1993).

31. G. A. Krulik, and N. V. Mandich, "METALLIC COATINGS", in: Kirk-Othmer Encyclopedia of Chem. Technology, Vol.8, 4th ed., pp.258-291 Wiley, N.Y., (1995).

32. N. V. Mandich, and R. Tuszynski, "METALLIZING OF PLASTICS", in: Engineered Materials Handbook, ASM International, pp. 356-364, (1995).

33. J. McDermott, "Plating of Plastics with Metals, Chemical Technology, Review No.138" (1979); J.I. Duffy, ed, "Electroless and Other Non-electrolytic Plating Techniques-Recent Developments”, Chemical Technology Review No.171, Noyes Data Corp, Park Ridge, NJ (1980).

34. G.G. Gawrilov, "Chemical (Electroless) Nickel-Plating", Portcullis Press, Redhill, UK, (1979).

35. G.O. Mallory, and J. Hajdu (eds),”Electroless Nickel Plating”, AESF, Orlando, Fl.(1990).

36 .J. K. Dennis and T.E. Such, “Nickel and Chromium Plating”, 3rd Ed., Woodland Publ. Co. Cambridge, UK (1993).

37. D. J. Coombs, Plating Surf. Finish., 68,(7 ) 58 (1981).

38. S. Jahn and N.V. Shanmugam, Met. Finish., 84(3) 51(1986).

39. W. Goldie, "Metallic Coating of Plastics”, 2 vol., Electrochemical Publications Ltd, Middlesex, England, 1968.

40. L.J. Durney, ed, "Electroplating Engineering Handbook", 4th ed, Van Nostrand Reinhold Co, Inc, New York, (1984).

41.M. Paunovic and I. Ohno, “Electroless Deposition of Metals and Alloys”, Proceedings Vol.88-12, The Electrochemical Soc., Inc, Pennington, N.Y., (1988).

42. W. Riedel, “Electroless Nickel-Plating”, ASTM International, Metals Park, Oh.(1991).

43. R. Weiner, Ed., “Electroplating of Plastic”, Finishing Publication, Middlesex, UK (1977).

44. G. Muller and D.W. Baudrand, “ Plating ABS Plastics”, Teddington, UK (1971).

45. H. Narcus, Plating, 55(8) 816 (1968),

46. G. H. Carlson, Prod. Finish., 44(9)70 (1980).

47. E. Pollard, ibid, 23(5) 23(1970).

48. C. C. Weekly, Plat. Surf. Finish., 53, (1),107(1966).

49. N.V.Mandich, ”On the Troubleshooting Methodology”, Proceedings of the AESF 86 th Annual Technical Conference, Cincinnati, Oh., (1999).

50. N.V. Mandich, Met. Finish., 97 (8)42(1199).

51. M. Jamison, ”Causes of Stardusting in Plating Plastic”,10th Annual Meeting , Amer. Soc. Electroplated Plastic, San Diego, Ca., (1977).

Table 2. Defects: their causes and remedies.

Symp

Possible Cause

Remedy

Blistering after Electroless deposition

1. Poor etching

2. Greasy surface

3. Electroless solution is too concentrated.

4. Electroless solution is too fast.

5. Entrapped moisture in the plastic substrate; or strains and stresses present.

a. Increase etching treatment time.

b. Increase temperature.

c. Agitate etching solution or work. . d. Use wetting agent in etching solution.

e. Analyze for possible addition of H2SO4.

a. Renew etching solution.

b. Prolong cleaning time or raise temperature.

c. Provide operators with gloves.

a. Dilute electroless plating solution.

b. Lower the reducer’s concentration.

a. Contact molder for remedial action.

Roughness

1. Activating solution too old.

2. Excessive time in Activator solution.

3. Over etching.

4. Excessive H2SO4 in Etch

solution.

5. Contamination of Electroless plating solution

6. Deposition on plating racks.

a. Replace solution.

a. Reduce treatment time.

a. Reduce etch time.

a. Analyze and correct by dilution, followed by CrO3 addition.

a. Filter solution and clean (strip) tank.

a. Strip racks thoroughly

b. Use stainless steel or titanium racks.

Blistering after Electroplating step.

. 1. Overheating at rack contact points, due to the poor electrical contact, at these points or neighboring areas of the pars.

a. Redesign the rack contacts.

No Electroless deposition.

1. Wrong polymer.

2. Low reducer in Electroless bath.

3. Low Etch temperature.

4. Insufficient Activation.

5. Insufficient Acceleration

a. Check the grade and type of polymer for platability.

a. Analyze and correct.

a. Check thermostat and heaters.

a. Increase temperature in the activator, or decrease time in accelerator.

a. Increase acceleration time; Analyze and correct concentration.

Slow Electroless deposition.

1. Catalyzing and/or Activating solution too dilute.

2. Sensitizing and/or activating solution too cold.

3. Electroless plating solution too dilute.

4. Electroless deposit too cold.

5. pH of electroless solution too low

a. Strengthen sensitizing and/or activating solution.

a. Warm-up sensitizing and/or activating solution.

a. Regenerate electroless solution according to operating instructions.

a. Warm-up solution.

a. Adjust pH

Conducting layer burns during electroplating

1. Electroless deposit too thin.

2.Current density too high.

3. Contact points too small.

4. Contact points worn through work movement.

5. Bipolar effect-anodic dissolution.

a. Prolong the plating time.

a. Reduce current density to 3-5 ASF.

a. Increase contact area or size of contacts.

a. Attach work better on racks.

a. Better space racked parts.

Poor adhesion between electroless and electroplated metals.

1. Plastic surface contaminated with mold release compound.

2. Etching time too short.

3. Etching time too long.

4. Etching solution too concentrated or too hot.

5. All other conditions being satisfactory, molding characteristics such as stresses, strains, in the molded parts are present.

6. Electroless Nickel has become passive.

a. Do not use mold release compound.

a. Prolong etching time.

a. Reduce etching time.

a. Dilute etching solution or work at lower temperature.

a. Contact molder.

b. Use full strength Watts nickel bah for a strike ; or use a Wood’s nickel; or use sulfamate nickel.

c. Use Cu-pyrophosphate bath before bright copper or nickel.

a. Use “ live entry” going into bright copper and nickel or nickel activator49.

b. Shorten transfer time from electroless nickel to the first plating tank.

Poor adhesion between electroless metal and plastic.

1.Etching solution out of balance.

2. Stresses and strains in molded plastic part.

3. High pH and to low concentration in the catalyst solution.

4. Too long post-catalyst

treatment.

5. Electroless solution plates too fast.

a. Analyze for Cr(VI), Cr(III) and total acidity.

a. Contact molder for remedial action, after checking for strains and stresses using glacial acetic test.

a. Analyze.

a. Lower treatment time.

a. Lower temperature in electroless bath or its reducer concentration.

Incomplete (skip)

deposition, or complete absence of plating .

1. Work contaminated with silicone.

2. Inadequate etching.

3. Work racked too close.

4. Neutralizer exhausted.

5. pH or temperature of Electroless solution too low.

6. Excessive Etch solution run-out from blind holes, recesses, etc.

7. Concentration of catalyst metal too low, and too low temperature at too low pH.

8. Etch time and temperature too low for certain ABS plastics and highly stressed surfaces.

9. Contaminated Etch.

10. Electroless deposit dissolving in Acid copper solution.

a. Avoid use of silicone mold release compounds.

b. Replace cleaner or increase its concentration.

a. Extend treatment time in etching bath and increase temperature.

a. Improve the racking of the parts.

b. Increase contact area or size of contacts.

a. Replace Neutralizer.

a. Increase time.

a. Adjust pH

b. Warm-up Electroless solution.

a. Improve rinsing and agitation.

a. Analyze and correct Catalyst bath

b. Adjust the temperature and pH.

a. Stressed surfaces and certain plastics may require highest obtainable temperatures and/or longer times.

a. Increase time in Neutralizer.

a. Strike deposit in Woods Ni- strike.

b. Strike in Cu-pyrophosphate before transferring to Acid copper bath.

No Electroplated deposit.

1. Bad racking.

2. Initial current density (CD) too high, causing “burning-off” of thin electroless deposit.

3. Electroless deposit dissolving in Acid copper solution.

4. Passive Electroless Nickel.

a. Improve racking , so that contact points are in medium to high CD areas.

a. Start electroplating step at low CD, ramping to full current within 2 minutes.

a. Strike deposit in Woods Ni- strike or in Cu-pyrophosphate strike before transferring to acid copper bath.

a. Electroplate immediately, or activate in activating dip.

Sand-paper Effect

1. Electroless bath out of balance, giving solid particles precipitation.

2. Plastic surface over etched

3. Dirty electroless solution.

a. Analyze and filter electroless bath.

a. Lower the time and the temperature in the etch tank.

a. Filter bath

Stardusting

1. Controversial problem51

2. Buildup of TiO2 and/or SiO2 in the etchant51

a. Eliminate SnCl2 sensitizer.

b. Use ElCu instead off ElNi

a. Reduce surface tension in the Etch solution.

b. Uses hot save rinse after etch without agitation.

c. Use full spray rinses.

d. Guard against over-etching.

Plating on plating Racks

1. Poor racks maintenance.

2. Too High pH and

concentration of the Catalyst solution.

3.Too high temperature in the Catalyst solution.

4. Too high concentration and/ or time in the Catalyst solution.

5. Too long time in the post-catalyst (Accelerator) solution.

6. Build-up of the catalytic metal or metallic dust in rack striper solution.

7. Contaminated Accelerator solution due to the build up of metallic dust.

a. Strip racks regularly.

a. Lower the concentration of catalyst and /or pH.

a. Lower the temperature of the catalyst solution.

a. Lower the concentration and the time in the Catalyst solution.

a. Lower the time in the Accelerator solution.

a. Replace the rack striper solution.

a. Replace the Accelerator solution.

Voids or Air Pockets

1. Poor cleaning.

2. Insufficient agitation.

3. Low total acidity in etch tank.

4. Poor rinsing of etch solution; or inefficient post conditioner solution.

a. Analyze or replace cleaner.

a. Increase agitation.

a. Analyze for total acidity in the Etch solution.

a. Improve rinsing; or replace post- conditioner solution.

Dull Electroless Plating

1. Electroless bath out of balance.

2.Overetching.

a. Analyze and correct the bath.

a. Lower the temperature and/or time in the etch tank.

High Drag-in

1.Poorly engineered rinse tanks

a. Change rinse tank design to counter current floe ant to spray rinses, especially after Etch and Catalyst tanks.

Overall poor appearance of the plated part

1. Sink marks, pits, splay marks, etc.

a. Contact molder.

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