化学镀Ni-Pd-P合金工艺的研究

发布时间：2018-04-18 10:53

  本文选题：化学镀 + 镍钯磷合金　； 参考：《广东工业大学》2016年硕士论文

【摘要】：印制线路板(PCB)的铜质焊盘表面容易形成氧化层,使电阻变大,且易与焊料(特别是含锡的)形成金属间互化物(IMC),这种IMC易发生脆性断裂,严重影响焊接可靠性。为了限制或者消除IMC的存在,在铜与焊料的界面之间加入阻挡层。目前常常采用化学镀镍/浸金的表面处理工艺,但镀镍层具有较大的空隙率,且金沉积的颗粒较大,就需要较厚的镍层和金层来减少空隙；同时,金容易对镍层造成过度腐蚀,存在“黑盘”的风险。本文用化学镀的方法得到了致密的非晶态镍钯磷合金镀层,对比研究了以此镀层为阻挡层的两种方法：(1)直接在铜表面上化学镀镍钯磷合金镀覆层,简称化学镀镍钯合金工艺ENEP(2)在铜表面先镀层薄镍,再化学镀镍钯磷合金镀层,简称化学镀镍/镍钯合金工艺EN/ENEP。由于钯颗粒细小,两种工艺所得镀层比较致密、孔隙率低,外观呈亮白色,可直接用于焊接。同时底层Ni不易发生氧化,可避免“黑盘”问题的出现。通过SEM、EDS、XRD、X射线荧光测厚仪以及电化学工作站,研究了氯化镍、氯化钯、乙二胺、氨水、次磷酸钠、温度以及pH等因素对化学镀镍钯磷合金镀层成分、表面形貌、沉积速率、镀层结构的影响,镀层性能通过结合力试验、中性盐雾试验和可焊性试验进行测试。经过正交实验优化得到镀液基础配方及工艺条件为：NiCl2·6H2O 12g/L, PdCl2 0.1g/L, NaH2PO2·H2O 6g/L,乙二胺(En)9mL/L,氨水7mL/L,氯化铵3g/L温度65～70℃,pH 8.5～9.0。选取了具有代表性的典型添加剂,考擦其对镀液稳定性、镀层孔隙率及沉积速率的影响,最终得到通过正交实验优化的添加剂组合为：二氧化硒7mg/L、硫酸铜15mg/L、三氯化镨7mg/L。所得镀层表面平整,颗粒大小均匀,结晶细致,无明显的气孔和裂纹,镀层中镍钯磷含量分别为Ni 85.19%.、Pd 6.25%、P8.56%,各元素分布均匀；通过调节pH及镀液中镍盐与钯盐的比例,可以控制镀层中Pd的含量,结果表明在pH为8.5的镀液中随着钯盐与镍盐摩尔比从10增加到100,镀层中钯含量可控范围为4～50wt%；Ni-Pd-P合金镀层的耐蚀性、可焊性优于化学镍层,合金中钯含量越多,镀层腐蚀倾向越小。采用线性电势扫描的方法,以铜电极和镍-磷电极为工作电极,研究了Ni-P、Pd-P以及Ni-Pd-P合金的阴极极化曲线,并探讨了各添加剂对阴极沉积过程的影响。发现钯离子可能是通过促进次磷酸根氧化来催化镍、钯以及它们合金的沉积行为的,在Ni-Pd-P合金沉积的过程中,同时伴随着镍与钯置换反应的发生。钯会促进镍的还原沉积,镍对钯的沉积起抑制作用。
[Abstract]:It is easy to form oxide layer on the copper pad surface of printed circuit board (PCB), which makes the resistance become larger, and forms intermetallic intermetallics with solder (especially tin). This kind of IMC is prone to brittle fracture, which seriously affects the reliability of welding.In order to limit or eliminate the existence of IMC, a barrier layer is added between the interface of copper and solder.At present, the electroless nickel plating / gold leaching surface treatment process is often used, but the nickel plating layer has a large void ratio and the gold deposit particles are larger, so the thick nickel layer and gold layer are needed to reduce the void; at the same time, the gold is easy to cause excessive corrosion to the nickel layer.There is a risk of a black disk.In this paper, a dense amorphous Ni-Pd-P alloy coating was obtained by electroless plating. Two methods of electroless Ni-Pd-P alloy plating on copper surface were studied.Electroless nickel-palladium alloy plating process ENEP2) plating on the surface of copper first thin nickel, then electroless Ni-Palladium phosphorus alloy coating, for short, electroless nickel plating / Ni-PD alloy process en / ENEP.Due to the fine palladium particles, the coating obtained by the two processes is compact, with low porosity and bright white appearance, which can be directly used in welding.At the same time, the bottom Ni is not easy to oxidize, which can avoid the problem of "black disk".The effect of nickel chloride, palladium chloride, ethylenediamine, ammonia water, sodium hypophosphite, temperature and pH on the composition, surface morphology and deposition rate of electroless Ni-Pd-P alloy plating was studied by means of SEMS-EDSX X-ray fluorescence thickness meter and electrochemical workstation.The effect of coating structure, coating properties were tested by adhesion test, neutral salt spray test and solderability test.The basic formula and process conditions of plating solution were optimized by orthogonal experiment: 1: NiCl2 6H2O 12g / L, PdCl2 0.1g / L, NaH2PO2 H2O 6g / L, ethylenediamine Enn 9 mL / L, ammonia water 7ml / L, ammonium chloride 3g/L temperature 6570 鈩，

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