Student : Shian-yi yang Student ID:M99L0107 Adviser : Keh-moh Lin Student : Shian-yi yang Student ID:M99L0107 2018/8/8 STUT 太陽能材料與模組實驗室

Outilne Introduction Experimental procedures Results and discussion Summary 2018/8/8 STUT 太陽能材料與模組實驗室 2

Introduction In meeting the demands for high pitch interconnections between electronic components and substrates, high quality soldering is needed [1]. Fundamentally, solders should wet the substrate and provide good adhesion [2]. Thus, soldering reaction has been extensively studied during the last few decades, and the core issue in soldering is the formation and growth of IMC between the solder and the substrate [3–6]. 2018/8/8 STUT 太陽能材料與模組實驗室 3

Due to their good mechanical properties, adequate wetting characteristics as well as the comparable melting temperature, eutectic Sn–Ag and Sn–Ag–Cu lead free solders have been considered to replace lead-tin ones [7]. When we explored the detailed morphologies of the IMC forming at the interface of Sn–3.5Ag–Cu during wetting, we discovered that nano-size Ag3Sn particles were present on the surface of these IMC [8]. 2018/8/8 STUT 太陽能材料與模組實驗室 4

Experimental procedures Fig. 1. Schematic of the soldering process. 2018/8/8 STUT 太陽能材料與模組實驗室 5

For the substrate, 99. 9% pure Ni and Cu coupons of 0 For the substrate, 99.9% pure Ni and Cu coupons of 0.1mm thick and 10mm wide were used. After polishing, the coupons were degreased in a 50% water solution of HCl, followed by cleaning in ethanol and drying in air. After applying of RA flux (non-clean), the coupon was dipped into molten solder alloy using a meniscometer (wetting balance, model ST50) as shown in Fig. 1. 2018/8/8 STUT 太陽能材料與模組實驗室 6

3.1. The surface morphologies of IMC with Ag3Sn formation Fig. 2. Surface morphologies of IMC after wetting for 90 s: (a) Sn–37Pb/Cu; (b) Sn–3.5Ag/Cu; (c) Sn–3.5Ag/Ni. 2018/8/8 STUT 太陽能材料與模組實驗室 7

Fig. 3. Surface morphologies of Sn–3. 5Ag–0 Fig. 3. Surface morphologies of Sn–3.5Ag–0.7Cu/Ni IMC after wetting for 90 s: (a) facetlike IMC on the top of wetting region; (b) large facet-like (Cu,Ni)6Sn5 IMCs with hundreds of Ag3Sn particles embedded; (c) column-shape (Cu,Ni)6Sn5 IMCs with tens of Ag3Sn particles embedded; (d) stick-shaped (Cu,Ni)6Sn5 IMCs with several Ag3Sn particles embedded. 2018/8/8 STUT 太陽能材料與模組實驗室 8

Fig. 4. EDS analysis at the region containing particle on the surface: (a) Sn–3.5Ag/Cu; (b) Sn–3.5Ag–0.7Cu/Ni. 2018/8/8 STUT 太陽能材料與模組實驗室 9

3.2. The effect of soldering and aging time on the particle growth Fig. 5. The average Ag3Sn size at different soldering time on IMC surface. 2018/8/8 STUT 太陽能材料與模組實驗室 10

(a) aging at 70 ◦C for 200 h; (b) aging at 70 ◦C for 500 h aging. Fig. 6. The ripening of Ag3Sn particles on the facetlike (Cu,Ni)6Sn5 IMCs: (a) aging at 70 ◦C for 200 h; (b) aging at 70 ◦C for 500 h aging. 2018/8/8 STUT 太陽能材料與模組實驗室 11

3.3. The formation mechanism of the Ag3Sn particles Fig. 7. Schematic diagrams of formation of an Ag3Sn particle on the intermetallic compound. 2018/8/8 STUT 太陽能材料與模組實驗室 12

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Summary 奈米大小的Ag3Sn顆粒在表面上會發現不同IMC。 銲接時間對錫銀影響不大。這表示Ag3Sn粒子發生凝固過程。 2018/8/8 STUT 太陽能材料與模組實驗室 14

Thank you for your attention 2018/8/8 STUT 太陽能材料與模組實驗室 15