The New Plating Process on Plastics

TRANSACTIONS OF MATERIALS AND HEAT TREATMENTVol.25 No.5PROCEEDINGS OF THE 14H IFHTSE CONGRESSOctober 2004The New Plating Process on PlasticsMakoto Imamura, Jun Okada, Kazuya SatohOkuno Chemical Industries Co,Ltd, JapanAbstract: This process does not use general electroless plating solution containing formaldehyde(carcinogen) andphosphate(the object of waste water regulation). Futhermore, we succeeded in developing a new electroless copper platingsolution which is usable semi-permanently by using the special reducing agent. The electroless deposition forms a very thinconductive film on substrate. Therefore, it can prevent some appearance defects (e.g. pits, pin-holes, laminations andinclusions) that occur in the conventional ones. In addition, it is possible to eliminate electroplating of copper from theprocess by applying the exclusive nickel solution in electroplating. Therefore, the obtained metal parts can be recycled ashigh quality stainless steel. Given this copper electroplating-free process, 25 11 m-thick nickel deposition at the stage ofelectroplating, at least, enables the metal layers to show properties as versatile as those of the conventional(its totalthickness is 25 u m in the comparative conventional process).Key words: plaing on plastis, plating process, rececling. regulation to phosphorus and nitrogenWET- PLATING PROCESS ON PLASTICS has beenphosphate in the electroless solution and the absenceindustrially used since the early 1960s. It is currentlyof copper electroplating step.applied in a wide range of applications such as(2)Excellent Plating Film Propertieselectronic components (e.g.EMI shield) and auto-) The conductive film is extremely thin, so there aremotive decoration parts with the aim of reducing totalfew appearance faults, which would give badcost and product weight.1,2 ABS is one of the mostinfluences to the final appearance, on the surfacecommon resin substrate used. Generally, the steps ofafter the conducting step. That’s the reason why weplating on ABS resin include an initial adsorption ofcan expect more beautiful appearance.tin-palladium colloid on a chemically etched surface to●The adhesion, resistance to thermal cycle and corro-catalyze a subsequent deposition of electroless nickel orsion resistance of plated ABS resin are almost samecopper. Once ABS resin is coated with the conductiveor better degree than those of the conventional one.film, it can be electroplated. The conventional processs,(3) The adhesion, resistance to thermal cycle and corro-however, is confronted with environmental problemssuch as containing formaldehyde, the regulation againstdischarge of nitrogen and phosphorus, and theprohibition against ocean disposal of industrial wastes2. Experimentallike consumed electroless nickel plating solution.3,4We checked the plated ABS resin in terms of appear-Further-more, recycling of plated plasticsance, resistance to thermal cycle, corrosion resistancehas become important task recently.3 Under thisand adhesion. The conventional electroless nickel plat-circumstance, we have developed an innovative platinging process was also performed to evaluate the newprocess on plastics to deal with these environmentalprocess and compare with it. When preparing samplesproblems.5 In this paper, we report about thefor each test, the substrate was ABS resin (CYCOLACmechanism of the process, the properties of plated3001M，UMG ABS Co.,Ltd,Japan:50mm X 90mm Xarticles(ABS resin) and plating film which were treated3mm) and was treated by steps shown in Table 1. Wewith the new process.also investigated effects of thickness of the nickel1. The Features of this New Process and itselectroplating in the new process to the properties withchanging it variously (Shown in Table 2).Products2.1 AppearanceThe features are given below.We checked the surface after chromium plating(1)Environmental Protection Processwhether there are any defects (pits, pin-holes, inclu-●Shortening of the total treatment steps, and reductionsions and laminations) or not, leveling and luster byof waste solution.visual.●The conducting bath contains no formaldehyde, nophosphorus and nitrogen compounds as reducingExE中国煤化工selow.agents.0HCNMH G, 1h→RT, 0.5h●Using a new reducing agent makes it very stable andRT meausueucuperaue al avund 25C. This cyclesemi-permanently.was repeated three times. It followed TOYOTA●Complete phosphorus-free process because of noStandards TSH 6504G1120PROCEEDINGS OF THE 14H IFHTSE CONGRESSOctober 2004Table 1. Treatment steps of each process.film which is only 0.01~0.02 u m. (Figure 1 shows(water rinse between each step are omitted)the cross section of ABS resin which is treated with thenew process by TEM) Ms.Ono and others succeeded inNEWCONVENTIONALTEM (Transmission Electron Microscope) observationCleaningon the cross section of this film, and found that thisEtchingdeposition was composed of grains sized about 2 nm.NeutralizationThis characteristic causes the deposition of electrolyticplating starts from the contact points with racks. FigurePre-dippingCatalyzing2 shows the products after chromium plating. We foundAcceleratingthat the total nickel thickness has to be only 25 μ mConductingElectroless nickel plating(Nickel plating 1 needed 15 u m ) to gain appearance isequal with the conventional one in luster and leveling,Nickel plating 1Activationthe new process doesn't apply copper electroplatingNickel plating 2.Strike platingwhich provides good leveling though.Dur-nickel platingChromium platingAcid copper platingSemi-bright nickel platingBright nickel platingTable 2.Con dactive flmChange of the thickness of the nickel electroplating.Metal layer| Nickel plating 1 I Nickel plating 25,10,15or20 u m10μm.Copper SB-nickelB-nickelCONVENTIONAL 15 u m6μ m4μ mABS2.3 Corrosion Resistance Test (CASS test)Test condition followed (JIS) H 8502. **Figure 1. Image of TEMThe test duration was 50 hours.(the cross section of plated ABS resin)Instrument : CASS TEST instrument II R-ISO-3SUGA Test Instruments, JapanmakingtestingNaCl(g/L)50士550+5CuCl2 . 2H2O(g/L)0.26+0.02 0.26土0.02H.03.0~3.2Spraying rate m/80cm2/h1.5土0.5Salt water temp.(C)50士5 _Air saturation temp. (C)63+2Chamber temp. (C)Compressed air pressure( kPa)70~1672.4 AdhesionAdhesion measurement followed (JIS) H 8630 and(ASTM)***B-533.Instrument: AUTOGRAPH SD-100CFigure 2.Left: sample treated by the conventionalSHIMAZU Corporation, Japanprocess.Right: sample treated by the new process.3.2 Resistance to Thermal Cycle3. Results and DiscussionThe results are shown in Table 3. Cracks were found3.1 Appearance中国煤化工(Nickel plating 1 wasIt was hardly to find pits, pin-holes, inclusions and5μmf YH=;ks on the surface thatlaminations, which are apt to grow in the particularwerelCNMHGlating1neededmoreelectroless solution, on the surface treated by the newthan 10μ m). It is said cracking can be caused byone. This advantage is due to the very thin conductivedifference in linear thermal expansion coefficientVol.25 No.5TRANSACTIONS OF MATERIALS AND HEAT TREATMENT1121between resin and plating film. The results indicate that0r◆thick plating film have a strong resistance to thermal9.8cycle. (however, when the nickel plating 2 film wasthicker than the nickel plating 1, cracks tended to▲appear even if the total thick was the same. That showsappropriate thickness balance exists between the two2 9.2layers.) The total nickel thickness in this process isrequired more than 20 μ m to have a relevant resistance.8.8Table 3. Results of thermal cycle test.★conventionalNickelTotal nickel8.4plating 1RESULTthickness1202305μ m15μ mCrackstotal thiokness of oloctroplating(μ m)10μm.20μm .GoodFigure 3. Results of CASS test of each processNEW15μm25μm(the test duration was 50 hours)20μm30μm16CONVENTotal thickness 25μ m( some samples)企14TIONAL之123.3 Corrosion Resistance书10The results are shown in Figure 3.Plated ABS resinby the new proved to be more resistant to corrosionwith 20um-total thickness and more, in comparisonwith corrosion resistance of the conventional one. Inaddition, articles plated by the conventional formverdigris when corrosion reaches copper layer, butthose by the new process wouldn't form verdigris onaccount of no copper layer. So from the viewpoint ofnowconvontionalvisual, we think that the new process is superior. Theresults indicate the thickness of nickel electroplatingFigure 4. Adhesion strength between substrate andalso affects on corrosion resistance greatly. To keep theplating flm of each process.potential difference between the nickel plating 1 and 2Referenceslayer is important too.1K. Sato. Joumal of Surface Finishing Society of Japan,3.4 Adhesion1996, 47:758Figure 4 shows the results of adhesion measurement.2 K. Sato. Jourmal of the Japan Society of Polymer Processing,The new process showed as good as or better than the2000, 12: 608conventional one.3M. Tsutsui. East Asia Surface Technology forum 2000, 2000, 414 T. Bessho. Joumal of Surface Finishing Society of Japan,4. Conclusions1999, 50: 1085The properties of the plating film deposited by the5 J. Okada, J. Katayama. Joumal of Surface Finishing Societyof Japan, 2001, 52: 48new process are as follows:5 M. Nakamura. Journal of Surface Finishing Society of(1) Better appearance due to less rough deposition andJapan, 2002, 53: 440pits.7 s. Ono, T. Osaka, K. Naitoh, Y. Nakagishi. Joumnal of(2) 25 μ m gives good leveling and luster.Surface Finishing Society of Japan,2002 53: 440(3) The thermal cycle resistance is as same as or better8 S. Ono, T. Osaka, Naitoh, Y. Nakagishi. J.Electrochem Soc.than the conventional one. (the electroplated nickel1999,146: 160layer should be more than 20 u m)(4) The corrosion resistance is as same as or better thanCorres中国煤化工the conventional one. (the electroplated nickel layerEmail:should be more than 20μ m)Mail adfMYHC N M H Gsurumi-ku, Osaka,(5) Adhesion between the plating film and substrate is538-44 JAPANas good as or better than the conventional one.Tel: 81-6-6965- 4114, Fax: 81-6-6963-0740