Diffusion barrier property of electroless Ni-W-P coating in high temperature Zn-5Al/Cu solder interconnects

Abstract

The operating temperature of high-temperature electronics can significantly promote the growth of intermetallic compounds (IMCs) at solder/substrate interfaces, particularly for low-cost Zn-based solders because of the rapid rate of reaction of Zn with Cu. Thus, a reliable and robust diffusion barrier is indispensable for suppressing the reactions between solder and substrate. In this work, a ternary Ni-W-P alloy was prepared via electroless plating. Its diffusion barrier property was evaluated by comparing the microstructures of IMC layers in Zn-5Al/Ni-W-P/Cu and Zn-5Al/Cu interconnects after liquid-solid reaction for prolonged durations. When the reaction lasted for 30 min, the thickness of the Al 3 Ni 2 produced in the Zn-5Al/Ni-W-P/Cu solder interconnects was only 2.15 μm, whereas the thickness of the interfacial layer of Cu-Zn IMCs (CuZn 4 , Cu 5 Zn 8 and CuZn) at the Zn-5Al/Cu interface was 94 μm. Because of the unbalanced growth of the IMCs in the Zn-5Al/ Cu interconnects, notable numbers of Kirkendall voids were identified at the CuZn 4 /Cu 5 Zn 8 , Cu 5 Zn 8 /CuZn and CuZn/Cu interfaces after prolonged liquid-solid reaction. By contrast, the Al 3 Ni 2 layer in the Zn-5Al/ Ni-W-P/Cu solder joints remained intact, showing the potential to effectively enhance the mechanical reliability of electronic devices.

Akımsız Kaplama Yöntemi ile Üretilen Ni-W-P Çoklu Alaşımların Sertlik ve Aşınma Özelliklerine Sodyum Tungsten İçeriğinin Etkisi

“…Sürtünme katsayısındaki bu düşüşün önemli sebeplerinden biri banyoya dahil edilen sodyum tungsten ile kaplamalarda tipik karnabahar yapısı oluşumudur. Kaplamalarda oluşan bu karnabahar deseninin yüzey temasını azaltmasından dolayı (gerçek temas alanına ulaşılmamış olması) sürtünme katsayısını düşürdüğü ve kaplamaların aşınma direncine fayda sağladığı önceki çalışmalarda bildirilmiştir (L. Liu et al, 2017;Mahmood et al, 2015). Yine benzer şekilde nikel matriste aşınma esnasında meydana gelen nikel oksitlerin kırılmasıyla aşındırıcı etki yapma durumuna bağlı olarak sürtünme katsayısında artışa neden olabilmektedir.…”

Thermal stability of high temperature Pb-free solder interconnect characterised by in-situ electron microscopy

“…The interconnect was prepared in 3 steps: (i) an electroless Ni-W-P ternary alloy was produced on polycrystalline copper substrates; (ii) Zn-5Al solder pellets (weight: approximately 0.15 g, melting point: 382°C) were then placed on Ni-W-Pplated Cu substrates; (iii) reflow was conducted at 450°C on a hotplate attached to a temperature control unit. Details of the electroless plating and reflow profile can be found in a previous paper [6].…”

“…However, rapid interfacial reactions between Zn-Al solders and Cu substrates significantly deteriorate the reliability of the solder interconnects [5]. Thus, novel metallisation such as electroless Ni based interlayers (Ni-W-P, Ni-P) were applied [6] as a diffusion barrier to resist the interfacial interaction and subsequent diffusion.…”

Characterizing the Soldering Alloy Type Zn–Al–Cu and Study of Ultrasonic Soldering of Al7075/Cu Combination

“…The addition of a small amount of suitable alloying elements lowers the melting temperature of these solders and enhances the solderability. Research on Zn-based solders has been carried out by many authors [8][9][10][11][12][13][14]. In their works, they have mainly used solders based on Zn-Al or Zn-Sn with the addition of other elements.…”