树脂表面化学镀镍层及其电磁性能评价-Applied Mechanics.pdf

Electroless Plating Nickel Film on Surface of Epoxy Resin and Evaluation of Its Electromagnetic Shielding Effectiveness Peng Jin1 a Shi Yun Dong1 b Bin Shi Xu1 c Zhan Yong Song1 d 1Science and Technology on Remanufacturing Laboratory Academy of Armored Forces Engineering Beijing 100072 China ajinpeng1301 bsyd422 cxubinshi dstranger303 Keywords Epoxy Resin Electroless nickel plating Electromagnetic shielding effectiveness Abstract Nickel coating was prepared on surface of Epoxy Resin plate by electroless plating process Surface and section morphologies of the coatings were observed by scanning electron microscopy SEM and metallographic optic microscopy Electromagnetic shielding effectiveness was evaluated via flanged coaxial electromagnetic shielding effectiveness tester The results showed that the surface of the nickel coating prepared by electroless plating process was smooth and its structure was fine and compact The electroless deposition rate of the nickel coating reached at 12 m h In the frequency range of 300 kHz to 100MHz the electromagnetic shielding effectiveness of the nickel coating was above 60dB and in the frequency range of 100MHz to 1 5GHz the electromagnetic shielding effectiveness of the nickel coating was above 44dB Introduction Epoxy resin is one kind of thermosetting polymer materials with good adhesive electrical insulation corrosion resistance high strength and other properties In the meantime as an electronic device and integrated circuits packaging material it is widely used in electronics industry to prevent moisture dust and harmful gas from ingressing into electronic devices or integrated circuits 1 3 But as a kind of electrical insulator materials the epoxy resin has no shielding function for electromagnetic waves It must be processed for the metallization and conductive treatment in order to have the function of electromagnetic shielding effectiveness The electroless plating as an effective method for non metallic surface metallizing satisfies the performances including good plating layer uniformity corrosion resistance abrasion resistance electrical and magnetic properties 4 6 The coating parameters directly affect the coating performance By now the research of electroless plating on the epoxy resin surface is focused on the process of optimization solution components design and evaluation of coating performance 7 11 In this paper electroless nickel coating was prepared on surface of epoxy resin plate at the low temperature The surface and cross section morphologies of the coatings were observed and electromagnetic shielding effectiveness was tested Experimental Sample preparation The sample substrate material was o cresol formaldehyde epoxy resin Its size was 50mm 50mm 2mm It was pre processed as the following procedures such as Degreasing NaOH 70g L Na3PO4 30g L Na2CO3 15g L Washing Roughening HF 150ml L H2SO4 600ml L Washing Sensitizing SnCl2 2H2O 10g L HCl 40ml L Washing Activation PdCl2 0 25g L HCl 10ml L Washing Reduction NaH2PO2 H2O 10g L Washing The basic compositions of the alkaline electroless plating solution were NiSO4 6H2O 30g L NaH2PO2 H2O 30g L Na4P2O7 10H2O 60g L N CH2CH2OH 3 100ml L and appropriate amount additives During the plating process the water bath kettle was kept temperature around 35 C And pH value of the electroless plating solution was always kept around 10 Applied Mechanics and Materials Vols 148 149 2012 pp 963 967 Online available since 2011 Dec 22 at 2012 Trans Tech Publications Switzerland doi 10 4028 All rights reserved No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP ID 130 88 99 230 09 10 12 17 05 26 Tests and analysis Surface and section morphologies of the coatings were observed by Philips Quanta 200 scanning electron microscopy and OLYMPUS PMG3 metallographic optic microscopy Electromagnetic shielding effectiveness was evaluated via DN1015A flanged coaxial electromagnetic interference shielding effectiveness tester Results and discussion Surface morphology Fig 1 showed the surface morphologies of electroless nickel coating plating duration was 90 minutes From the figure it can be seen that the coating surface morphology presented the typically cellular structure and the cellular are tightly coupled between bodies The cellular showed the compact structure and each of the larger cellular bodies was composed by some smaller cellular bodies while its surface covered with tiny cellular particles The reason was that the nickel deposition firstly occurred at the point where had much more activated and these points became the centers of the nickel deposition During the process of electroless nickel plating the initial nickel deposition centers on the surface of epoxy resin were not continuous and these centers were some scattered particles presented like islands With the electroless plating reaction going on these scattered particles grew up and gradually spread outward At the same time there were more and more points activated during reaction thereby the deposition centers increased In other words the scattered particles increased which decrease the distance between these scattered particles At last these scattered particles gathered together and formed a complete coating These scattered particles developed thicker and ultimately the surface cellular morphology was formed The cross section morphology of the electroless nickel coating was showed at Fig 2 It was obvious that the nickel coating was well distributed and connected tightly with the epoxy resin Fig 1 SEM surface morphologies of the coatings Fig 2 Metallographic section morphologies a low magnification b high magnification of the coatings Electroless nickel plating deposition rates Temperature and pH value of the solution were two important factors which could influence the deposition rate of electroless plating To evaluate the influence of temperature on electroless nickel plating deposition rate the electroless plating reactions were carried out at different temperatures respectively and the plating duration was 90 minutes Then the plating temperature was kept at 35 C and changed pH value to examine the influence of pH value on electroless nickel plating When the temperature of electroless plating was at 25 C the coating would be produced after the sample was placed into the solution for 20 minutes During the whole reaction process there was only a little hydrogen separated out and a little Ni deposited and the deposition rate was low When the temperature of electroless plating was at 30 C and the sample was placed in the solution for 10 minutes and then deposition occurred After the reaction lasted for 40 minutes the hydrogen precipitation reached to peak value This indicated that the amount and rate of nickel deposition rate was higher at 30 C compared to 25 C When electroless plating temperature was at 35 C and the sample was placed into the solution for 5 minutes the coating was presented After 20 minutes Coating a b 964Mechanical Engineering Materials and Energy later the amount of hydrogen precipitation reached to peak value This showed that the amount of deposition and the rate of nickel deposition could be further improved with the increase of temperature When the electroless plating temperature was over 40 C there was a large number of hydrogen separated out The precipitation of hydrogen was still abundant during the whole reaction processing and the reaction was violent The deposition rate was obtained at different temperatures by measuring the coating thickness The result was showed in Fig 3 What can be seen from the figure was that the deposition rate went up with the increase of temperature The reason for this phenomenon could be as the temperature increases the rate of ionic diffusion became faster and the reaction went more activated thus the rate of coating deposition increased As a word the rate of coating deposition was higher at the some higher temperatures When the pH value of the solution was less than 8 5 there was no electroless plating reacted The coating was rough and incomplete when the pH value was greater than 10 5 When the pH value was between 9 0 and 10 5 it could prepare the continuous nickel coating on the surface of epoxy resin The coating thickness was measured after electroless plating at different pH value solution and the plating duration was 90 minutes When the pH value was 10 the thickness of coating was the thickest and it could reach at about 18 m When the solution pH value was 9 the thickness of coating was the thinnest and it was only about 8 m The relationship between the pH value and deposition rate was shown in Fig 4 When the pH value was less than 10 the coating deposition rate increases with the increasing of Ph but when the pH value is greater than 10 the coating deposition rate decreased with the increasing of pH The coating deposition rate was the highest when the pH value was 10 and it can reach 12 m h 0 4 8 12 16 20 20253035404550 deposition Rate m h 1 Temperature 0 3 6 9 12 15 8 599 51010 51111 5 deposition Rate m h 1 pH Fig 3 The variation of the nickel coating Fig 4 The variation of plating rate with the deposition rate with the temperature pH value of plating solution Electromagnetic shielding effectiveness Electromagnetic shielding effectiveness could become an issue when electromagnetic fields interfere with the other electronic equipments Electromagnetic fields are radiated from sources such as equipment for television cellular telephone radio communication computer radar and other devices 12 Electromagnetic shielding is a process by which a material is able to reduce the transmission of electromagnetic radiation that affects the human or other equipments 13 Electromagnetic shielding material can provide EMI isolation and prevents the escape of radiated emissions Electromagnetic shielding effectiveness is an important indicator for measuring which kind of shielding materials is suitable or not According to the material electromagnetic shielding effectiveness test method SJ20524 1995 Epoxy resin was prepared to be disc whose diameter was 115mm then plated Ni on both sides of its surface The coating thickness was about 15 m for each side Electromagnetic shielding effectiveness was tested by DN1015A flange coaxial device The test equipment schematic was showed Fig 5 and Fig 6 showed the electromagnetic shielding effectiveness of nickel plating We can observe that in the frequency range of 300KHz to 8MHz the electromagnetic shielding effectiveness went up with increasing frequency The highest Applied Mechanics and Materials Vols 148 149965 electromagnetic shielding effectiveness could reach 86 8dB After the frequency was over 8MHz electromagnetic shielding effectiveness presented a decreasing trend The effectiveness could be over 65dB in frequency range of 8MHz to 100MHz however it was over 44dB in frequency range of 100MHz to 1 5 GHz 101001000 40 50 60 70 80 90 Shielding Efficiency dB Frequency MHz 1500 Fig 5 Electromagnetic shielding effectiveness testing setup Fig 6 The SE result of plating Conclusions 1 The surface of the nickel coating prepared by electroless plating process was smooth and its structure was fine and compact When the temperature of the solution was 35 C and the pH value was 10 the electroless nickel coating deposition rate reached 12 m h 2 The electroless nickel coating deposition rate increased with the increasing of temperature When the pH value was between 9 0 and 10 0 the coating deposition rate went up with the increasing of pH but when the pH value was greater than 10 the coating deposition rate decreased with the increasing of pH 3 The electromagnetic shielding effectiveness was tested via flanged coaxial electromagnetic interference shielding effectiveness tester The results showed that in the frequency range of 300KHz to 100MHz the electromagnetic shielding effectiveness of the electroless nickel coating was above 60dB and the highest electromagnetic shielding effectiveness can reach 86 8dB In the frequency range of 100MHz to 1 5GHz the electromagnetic shielding effectiveness of the coating was from 44dB to 60dB References 1 Harper C A Electronic materials and processes handbook New York Mc Graw Hill 2005 2 Tobias Merkel Michael Graeber Lienhard Pagel A new technology for fluidic Microsystems based on PCB technology Sensors and Actuators 77 2 1999 98 105 3 Zweben C Advances in composite materials for thermal management in electronic packaging JOM 6 1998 47 49 4 NARAYANAN TSNS BASKARANBI KRISH NAVENIAK et al Deposition of electroless Ni P graded coatings and evaluat ion of their corrosion resistance Surface Coat ings Technology 200 2006 3438 3445 5 Domenech S C Lima J E Drago V et a1 Electroless plating of nickel phosphorous on surface modified poly ethylene terephthalate films Applied Surface Science 220 1 2003 238 250 6 Chen C C Hung C W Yang S Y et al Effect of swelling pretreatment on the deposition structure on electroless copper of poly acrylonitrile nanocomposites for electromagnetic interference