無電鍍鎳鍍覆已廣泛地應用於微電子封裝工業之導電層，因此導電層中的無電鍍鎳與銲錫間之潤濕性及界面反應是重要之議題。本實驗於Al2O3陶瓷基材及Cu/Al2O3金屬化陶瓷基材上以不同pH值之無電鍍液鍍覆鎳金屬(Ni-P)並深入探討無電鍍鎳與共晶錫鉛銲錫間之潤濕性質及界面反應。
在潤濕性方面，無電鍍鎳與共晶錫鉛間之接觸角並不受無電鍍鎳中磷含量(6wt%P~12wt%P)影響，其接觸角介於30至50度間。為研究熱處理對於無電鍍鎳潤濕性質之影響，則對無電鍍鎳施以350℃下1至3小時的退火處理。退火處理後，經ESCA分析發現，無電鍍鎳表面有NiO，並且無電鍍鎳表面之氧含量明顯地隨退火時間增長而增加。此外經XRD分析得知，Ni3P析出相之繞射峰強度隨退火時間增加而增強。在潤濕性方面，當不以RMA助焊劑清除無電鍍鎳表面之氧化物時，經熱處理後之無電鍍鎳與共晶銲錫間之接觸角近乎180度。然而，當以RMA助焊劑清理之後，接觸角降為120至130度間。此表示未經熱處理之無電鍍鎳較經熱處理過後之無電鍍鎳富具潤濕性。

在界面反應方面，共晶錫鉛/電鍍金/無電鍍鎳/銅導電層/氧化鋁基材及共晶錫鉛/電鍍金/電鍍鎳/銅導電層/氧化鋁基材之兩銲點系統已製備完成。在無電鍍鎳鍍覆方面，高pH值之無電渡液可在銅金屬化陶瓷基材上鍍覆出含低磷含量之無電鍍鎳及表現高鍍覆速率。在多層金屬之顯微結構方面，無電鍍鎳及電鍍鎳皆為柱狀結構，電鍍金則為片狀結構。在240℃下退火試驗中，Ni-P-Cu-Sn-Pb固溶体在無電鍍鎳金屬層(Ni-12.12wt%及Ni-5.52wt%)之銲點系統中生成。而在電鍍鎳之銲點系統中，有Ni3Sn4金屬間化合物生成並零散分佈於銲錫與電鍍鎳之界面處。在200℃之退火試驗中，(Ni,Cu)3Sn4及Ni3Sn4金屬間化合物生成於銲錫與無電鍍鎳金屬層界面處。然而，當(Ni,Cu)3Sn4金屬間化合物內之元素擴散至銲錫中，此金屬間化合物將轉變為Ni-P-Cu-Sn-Pb固溶体。此外，Ni3Sn4金屬間化合物一旦成長至2~3 □m時便停止成長，以及無電鍍鎳(Ni-5.52wt%P)與電鍍鎳金屬化層會隨退火時間之持續而有突起之現象。在電鍍鎳銲點系統中，於相同之退火時間內，Ni3Sn4金屬間化合物在200℃退火下之成長厚度較240℃退火下之成長厚度大。

在熱時效方面,在無電鍍鎳(Ni-12.12wt%P)金屬之銲點系統中，於170℃下之熱時效過程中Ni3Sn4金屬間化合物及Ni-Cu-P-Sn-Pb固溶体生成。在130℃熱時效時，有裂痕及金屬層以片狀方式剝落的情況發生。在無電鍍鎳(Ni-5.52wt%P)金屬之銲點系統中，於170℃下經16天之熱時效試驗，無電鍍鎳(Ni-5.52wt%P)金屬層溶於銲錫中並生成Ni-P-Cu-Sn固溶体；經25天熱時效後，Ni3Sn4金屬間化合物由此固溶体內生成。而在130℃進行熱時效期間，幾乎沒有Ni-Sn金屬間化合物生成，唯有無電鍍鎳金屬層隨熱時效的持續進行而有突起之情況發生。另外，經實驗發現鉛及磷無法與Ni-Sn金屬間化合物共存，故磷析出及聚集於Ni-Sn金屬間化合物與無電鍍鎳金屬層之界面處。在電鍍鎳金屬之銲點系統中，NiSn8.5金屬間化合物於130℃及170℃熱時效過程中生成。事實上，在熱時效試驗中並沒有Au-Sn金屬間化合物生成於此兩個銲點系統中。在拉伸試驗方面，對Ni-12.12wt%P/Cu/Al2O3及Ni-6.63wt%P/Cu/Al2O3多金屬層之銲點而言，未經熱時效處理之銲點強度遠高於時效後之銲點強度。經XRD分析得知，(Ni,Cu)3Sn4或Ni3Sn4存在於無電鍍鎳與共晶銲錫之破裂面處。

The electroless-nickel (EN) has been deposited for the application of pad in the microelectronic industry. The wettability and interfacial reaction between solder and EN on the underlying substrate is thus a critical issue. In this study, EN deposited with various pH values was employed on the Al2O3 and Cu/ Al2O3 substrate, and both the wettability and interfacial reaction between EN and eutectic SnPb solder were investigated.
On wettability, the variations of phosphorous content in EN did not significantly influence the contact angle of Sn-37Pb on EN metallizations. The contact angles between Sn-37Pb and EN with phosphorous contents from 6wt% to 12wt% were in a range from 30 to 55 degree. To probe the effect of thermal treatment of EN on the contact angles, the deposited EN were annealed at 350℃ for 1 to 3 hours. The EN surfaces without RMA cleaning displayed the presence of NiO, and the increased oxygen contents were evident by ESCA spectroscopy. The peak intensity of precipitated phase of Ni3P from the EN was enhanced with increasing annealing time. The contact angles between the annealed EN and Sn-37Pb solder were approaching 180 degree without employing RMA flux. However, after using RMA flux, the contact angles were reduced to between 120 to 130 degree. This indicated that preventing EN from oxidation and precipitation was beneficial to wettability.

Joints of Sn-37Pb/Au/EN/Cu/Al2O3 and Sn-37Pb/Au/Ni/Cu/Al2O3 joints were fabricated. EN deposited with the lower phosphorous contents and higher plating rate on the Cu-metallized substrate were achieved in the bath solution of the higher pH value. Both the deposited EN and the electroplating Ni exhibited columnar structure, while the electroplating Au displayed laminar. During annealing at 240℃, the Ni-P-Cu-Sn-Pb solid solution was formed between the EN-based (Ni-12.12wt%P and Ni-5.52wt%P) multi-metallizations and the Sn-37Pb solder. The intermetallic compound Ni3Sn4 was randomly formed at the interface between the solder and the electroplating Ni. During annealing at 200℃, the (Ni,Cu)3Sn4 and Ni3Sn4 IMCs were present at the interfaces between the solder and the EN (Ni-12.12wt%P and Ni-5.52wt%P) metallizations. However, the (Ni,Cu)3Sn4 IMC transformed into the Ni-P-Cu-Sn-Pb solid solution after migrate into the solder bulk took place, and the Ni3Sn4 IMC stopped growing as soon as the thickness of IMC reached 2~3 □m. In addition, either Ni-5.52wt%P or electroplating Ni metallization became scalloped with increasing annealing time. In the case of Sn-Pb/Au/Ni/Cu joint, the thickness of Ni3Sn4 IMC formed at 200℃ was larger than that at 240℃.

The Sn-37Pb/Au/Ni-12.12wt%P/Cu joint formed the Ni3Sn4 IMC and solid solutions during aging at 170℃. There existed cracks and stripping in a flake during aging at 130℃. The Ni-5.52wt%P metallization in a Sn-37Pb/Au/Ni-5.52wt%P/Cu joint dissolved in the solder and formed the Ni-P-Cu-Sn solid solution during aging at 170℃ for 16 days. After aging for 25 days, the Ni3Sn4 was formed in the solid solution. During aging at 130℃, there was scarcely Ni-Sn IMC formed between the solder and the Au/Ni-5.52wt%P/Cu multi-metallization. There was a phenomenon of the EN scalloping with the increase of aging time. In other respects, Pb and P did not coexist with the Ni-Sn IMC, and there was a presence of phosphorus segregated and aggregated at the interface of the Ni-Sn IMC and EN. The electroplating Ni forms NiSn8.5 IMC with the solder during aging at 130℃ and 170℃. There was not distinct formation of Au-Sn IMC in joints of Sn-37Pb/Au/EN/Cu and Sn-37Pb/Au/EN/Cu. After aging test of pull-off assemblies, the adhesion strength between the solder and either Ni-12.12wt%P/Cu or Ni-6.63wt%P/Cu metallizations evidently was degraded. XRD analysis revealed that either (Ni,Cu)3Sn4 or Ni3Sn4 IMC was present at the fractured surface between EN and Sn-37Pb solder.

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