化学镍钯金表面处理工艺研究

采用扫描电子显微镜、润湿性、拔/撞锡球和打金线测试等分析手段,比较研究了四家化学镍钯金药水表面处理焊盘的焊接可靠性,同时比较研究了化学镍钯金表面处理和化学镍金表面处理焊盘的焊接可靠性差异.研究表明,化学镍钯金表面处理相对化学镍金表面处理可有效防止镍腐蚀(黑盘)缺陷引起的连接可靠性问题.     

挠性电路板化学镍钯金工艺技术研究

主要对化学镍钯金表面处理工艺原理进行介绍,通过挠性电路板化学镍钯金后引线健合能力、可焊性、抗老化等一系列可靠性测试,验证其相对其它表面处理技术更加优越,特别适用于表面贴装混合组装板等要求高连接可靠性的产品上,并且满足无铅组装工艺所有需求,非常适合挠性板、封装基板等的表面处理PCB制造。     

化学镍钯金钯层表面孔洞黑点可靠性研究及其标准制定

化学镍钯金为近几年新兴的表面处理方式,因其具备优良的打线和焊接性能被应用得越来越广泛;目前行业内对化学镍金表面处理的镍金层可靠性研究是非常多且有明确的一套接收标准,但对于化学镍钯金表面处理的钯层的一些可靠性研究目前却是非常少的。本文针对化学镍钯金镀层其钯层表面的孔洞黑点进行老化前后的可靠性验证,确定正常、轻微、中度、严重四种不同程度的孔洞黑点推拉力均可满足标准,中度以下的孔洞黑点可以直接放行使用,严重程度的孔洞黑点则需要做进一步的可靠性评估;针对孔洞黑点制定出的管控标准,为企业标准提供依据支持,对镍钯金产品质量管控前移具有重要的意义,可供业内进行参考。     

半导体晶圆ENIG/ENEPIG产品设计考量

通过化学自催化反应在半导体晶圆I/O铝或铜金属垫上沉积具有可焊接性的镍金/镍钯金层,此工艺已在MOSFET、IGBT、RFID、SAW Filter等产品上得到广泛应用。着重阐述了在新产品设计和工程评估阶段,对于晶圆产品本身应予以考量的因素,如钝化层种类及厚度,I/O金属垫的成分及结构,切割轨道上金属图形的大小及钝化层的覆盖,不同I/O pad的电势等。其中一些因素导致的问题会直接影响化学镍金/镍钯金后产品的性能应用。在化镀工艺过程中,要充分了解产品本身结构以及可能造成的相应缺陷及问题,并且应综合考虑这些因素的影响。     

田口试验设计在键合工艺参数优化中的应用

为提高微机电系统(MEMS)封装引线键合的可靠性和经济性,引入了镍钯金印刷电路板(PCB),但由于其保护皮膜中钯层的加入,键合工艺参数也需随之改变,该文运用试验设计(DOE)中的田口试验设计方法,找到了针对新型镍钯金皮膜的最优化键合工艺参数,根据优化结果,改进了键合工艺参数设置,成功地将镍钯金PCB应用到MEMS封装工艺中,不但提高了产品的可靠性,还降低了原材料成本,取得了良好的经济效益。     

LTCC纯银基板的化学镀镍钯金工艺

通过在银导体上逐次化学镀镍钯金来实现在LTCC纯银基板上的键合、钎焊等功能,避免了传统LTCC基板常用的多次贵金属套印,有效降低了生产成本.通过对样品进行试验验证,膜层键合强度和可焊性等都满足使用要求,可广泛应用于表面贴装和裸片邦定的微波产品工艺.     

化学镀镍钯金电路板金丝键合可靠性分析

在微组装工艺应用领域，为保证印制电路板上裸芯片键合后的产品可靠性，采用化学镀镍钯金工艺（ENEPIG），可在焊接时避免“金脆”问题、金丝键合时避免“黑焊盘”问题。针对化学镀镍钯金电路板的金丝键合（球焊）可靠性进行了研究，从破坏性键合拉力测试、第一键合点剪切力测试以及通过加热条件下的加速材料扩散试验、键合点切片分析、键合点内部元素扫描等多方面分析，与常规应用的镀镍金基板键合强度进行了相关参数对比，最终确认了长期可靠性满足产品生产要求。此外，对镍钯金电路板金丝键合应用过程中需要注意的相关事项进行了总结与说明。     

化学镀镍钯金技术在LTCC低成本化进程中的应用

介绍了一种通过在LTCC银导体上化学镀镍钯金替代金导体的工艺方法。利用该方法制备LTCC微波基板可有效解决化学镀镍金在LTCC基板制备过程的工艺缺陷。通过性能测试可知,化学镀镍钯金LTCC基板平均金丝键合强度可达到305 mN,平均金带键合拉力均大于500 mN,平均芯片剪切强度达到5.28 kgf。利用化学镀镍钯金技术制备的LTCC基板性能良好,有效推进了LTCC基板的低成本化进程。     

PCB生产中的化学镍金浅谈

本文针对目前市场PCB厂家化学镍金应用广泛的最终表面处理。化学镍金工艺具有高度的平整性、均匀性、可焊性或耐腐蚀性等,正日益受到广大客户的青睐,本文就实际生产中遇到一些常见品质问题的原因及对策进行探讨。     

化学镍层耐腐蚀影响因素研究

文章通过建立化学镍层表面SEM观测分级制度来检测镍层耐腐蚀性能,然后通过DOE试验分析了产线参数对化学镍层耐腐蚀性的影响,从而达到优化参数,降低风险的目的。     

化学镍/化学钯/浸金的表面涂覆层的可焊性和可靠性

概述了化学镍/化学钯/浸金(ENEPIG)表面涂(镀)覆层的优点。它比化学镍/浸金(ENIG)有更好的可焊接性和焊接可靠性。化学镍/化学钯/浸金表面涂(镀)覆层应该是有发展前景的。     

Study of Electromigration-Induced Failures on Cu Pillar Bumps Joined to OSP and ENEPIG Substrates

This work studies electromigration (EM)-induced failures on Cu pillar bumps joined to organic solderability preservative (OSP) on Cu substrates (OSP–bumps) and electroless Ni(P)/electroless Pd/immersion Au (ENEPIG) under bump metallurgy (UBM) on Cu substrates (ENEPIG–bumps). Two failure modes (Cu pad consumption and gap formation) were found with OSP–bumps, but only one failure mode (gap formation) was found with ENEPIG–bumps. The main interfacial compound layer was the Cu₆Sn₅ compound, which suffered significant EM-induced dissolution, eventually resulting in severe Cu pad consumption at the cathode side for OSP–bumps. A (Cu,Ni)₆Sn₅ layer with strong resistance to EM-induced dissolution exists at the joint interface when a nickel barrier layer is incorporated at the cathode side (Ni or ENEPIG), and these imbalanced atomic fluxes result in the voids and gap formation. OSP–bumps showed better lifetime results than ENEPIG–bumps for several current stressing conditions. The inverse Cu atomic flux (J _Cu,chem) which diffuses from the Cu pad to cathode side retards the formation of voids. The driving force for J _Cu,chem comes from the difference in chemical potential between the (Cu,Ni)₆Sn₅ and Cu₆Sn₅ phases.     

Effect of Thickness and Phosphorus Content on Au/Pd/Ni(P) Metal Finish of Printed Circuit Board

Electroless nickel/electroless palladium/immersion gold [Au/Pd/Ni(P) or ENEPIG] pads consisting of layers of Ni(P) (200 μin), pure palladium (Pd) or palladium phosphorus (PdP) (2 μin, 4 μin or 6 μin), and gold (Au) (2 μin or 4 μin) were prepared using two different processes (wire bonding and lead-free soldering). Each of these processes was done with zero- or two-time reflow. Different tests on solderability, wettability, wire-bonding capacity, and corrosion resistance were performed on different combinations of ENEPIG pads formed using different combinations of processes and conditions. Scanning electron microscopy was also performed to examine the surface characteristics of the pads. It was found that the ENEPIG pad sample with the 4-μin-thick Au and 4-μin-thick PdP layers possessed stable wire-bonding capacity and excellent lead-free solder reliability. In addition, the ENEPIG–PdP systems showed better corrosion resistance, which is attributed to the presence of the amorphous PdP layer protecting the nickel layer.     

适用于IC封装的表面涂覆层——化学镀镍、钯、金的未来

概述了化学镀镍/化学镀钯/浸金涂（镀）覆层的优点,它比起化学镀镍/浸金,不仅更适用于IC封装,而且提高了可靠性,降低了成本。     

Review of Capabilities of the ENEPIG Surface Finish

Surface finishes are used to protect exposed copper metallization in printed circuit boards from oxidation and to provide a solderable surface on which to mount electronic components. While it is true that some people have called electroless nickel electroless palladium immersion gold (ENEPIG) a “universal finish” for a wide range of applications from wire bonding to solder interconnects, this paper provides a review of the current literature on ENEPIG and assesses its overall capabilities compared to other surface finishes. Gaps in understanding the performance of ENEPIG as a printed wiring board surface finish are identified and further testing is recommended.     

化学镀镍镀钯浸金表面处理工艺概述及发展前景分析

随着电子封装系统集成度逐渐升高及组装工艺多样化的发展趋势,适应无铅焊料的化学镀镍镀钯浸金（ENEPIG）表面处理工艺恰好能够满足封装基板上不同类型的元件和不同组装工艺的要求,因此ENEPIG正成为一种适用于IC封装基板和精细线路PCB的表面处理工艺。ENEPIG工艺具有增加布线密度、减小元件尺寸、装配及封装的可靠性高、成本较低等优点,近年来受到广泛关注。文章基于对化学镍钯金反应机理的简介,结合对镀层基本性能及可靠性方面的分析,综述了ENEPIG表面处理工艺的优势并探讨了其发展前景。     

Comparative Study of ENIG and ENEPIG as Surface Finishes for a Sn-Ag-Cu Solder Joint

Interfacial reactions and joint reliability of Sn-3.0Ag-0.5Cu solder with two different surface finishes, electroless nickel-immersion gold (ENIG) and electroless nickel-electroless palladium-immersion gold (ENEPIG), were evaluated during a reflow process. We first compared the interfacial reactions of the two solder joints and also successfully revealed a connection between the interfacial reaction behavior and mechanical reliability. The Sn-Ag-Cu/ENIG joint exhibited a higher intermetallic compound (IMC) growth rate and a higher consumption rate of the Ni(P) layer than the Sn-Ag-Cu/ENEPIG joint. The presence of the Pd layer in the ENEPIG suppressed the growth of the interfacial IMC layer and the consumption of the Ni(P) layer, resulting in the superior interfacial stability of the solder joint. The shear test results show that the ENIG joint fractured along the interface, exhibiting indications of brittle failure possibly due to the brittle IMC layer. In contrast, the failure of the ENEPIG joint only went through the bulk solder, supporting the idea that the interface is mechanically reliable. The results from this study confirm that the Sn-Ag-Cu/ENEPIG solder joint is mechanically robust and, thus, the combination is a viable option for a Pb-free package system.     

Interfacial reaction and mechanical evaluation in multi-level assembly joints with ENEPIG under bump metallization via drop and high speed impact test

The criteria of mechanical reliability in solder joints can be identified and described by comparative evaluation via drop test and high speed pendulum impact test. Systematic samples of assembly and attachment joints with various Pd additions were employed and investigated in this study. The statistical values of mechanical performances were calculated and compared. Better high speed impact performance of SAC305/ENEPIG attachment joints with 0.06 μm Pd layers was confirmed owing to the single Cu₆Sn₅ phase growth. However, the comparative measurement of the better performance on drop testing exhibited in ENEPIG/SAC305/immersion Sn assembly joints with 0.1 μm Pd layers deposit resulted from the thinner and layer-type IMC growth. The correlation between the cracks propagation and Pd addition was established on the basis of the elemental X-ray color mapping via Field-Emission Electron Probe Microanalyzer (FE-EPMA). It is expected that through comparison between impact and drop test in mechanical reliability, a criterion of joints reliability can be established. Besides, the optimal Pd layer deposit for the ENEPIG surface finish in the attachment and assembly solder joints was demonstrated and confirmed.