The growth of electronics product has increased rapidly and hence drive challenges among the designers as well as manufacturers to select the best electronic packaging materials for their products. Among those materials, lead free solders has become the best replacement for lead-containing solders even though its performance still could not meet the original specification. Thus, this paper is aiming at studying the effect Nickel (Ni) additional with difference percentage into solder alloy toward intermetallic compound formation (IMC) and growth at the interface of the solder joint. The work was carried out by producing Sn-xNi (x = 0.0, 0.3, 0.5, 0.7, 1.0) through powder metallurgy method. The process started with powder milling at the speed of 1400 rpm for 3 hours. Then it was compacted into a thin pallet with size of 6mm diameter at the pressure of 5 ton. After that, the sample were subjected to reflow soldering for 250˚C for 25min heating duration and 15min holding time. Solder joint strength was carried out using ASTM D1002. Finally, characterisation was made in terms of IMC morphology, thickness and solder joint strength using metallographic microscope as well as scanning electron microscopy-energy dispersive x-ray (SEM-EDX). Results showed that the addition of Ni with different percentage produced different morphology of IMC at the interface after reflow soldering which also affects its growth behaviour. The IMC’s formed after reflow soldering produced closed and packed grain boundary when solder with higher Ni content was used. The type of IMC formed at the solder joint was Cu6Sn5 and its thickness increased with Ni addition. These results were the proof that Ni is a good candidate to improve solder joint performance by restricting the formation and growth of Cu3Sn IMC. In addition, the solder joint strength was found to be increasing upon Ni percentage increment. The highest strength value of 5.885MPa was produce when Ni was added up to 1.0%. This showed that Ni not only a good candidate to improve joint performance in IMC formation but also help in strengthening the solder joint.
Teknologi flip chip memberikan ketumpatan I/O yang sangat tinggi dan mengambil kira prestasi elektrikal yang paling baik dalam penyambungan komponen elektronik. Oleh itu, kajian tentang sebatian antara logam dilaksanakan untuk mengkaji kesan saiz bebola pateri bagi beberapa penyudahan permukaan, iaitu Kuprum dan Nikel tanpa elektrod/Palladium tanpa elektrod/Emas rendaman (ENEPIG). Pelogaman di bawah pateri (UBM) Ni/Pd/Au bagi aplikasi flip chip digunakan dengan sangat meluas dalam pembungkusan elektronik. Analisis FESEM dilakukan untuk menganalisis morfologi dan komposisi bagi sebatian antara logam (IMC). IMC yang terbentuk antara pateri Sn–Pb dan tanpa Pb dengan penyudahan permukaan kuprum semasa proses pematrian logam secara umumnya adalah (Cu, Ni)6Sn5 dan Cu6Sn5 dan Cu6Sn5. Sementara IMC utama yang terbentuk antara pateri Sn–Pb dan tanpa Pb dengan penyudahan permukaan ENEPIG adalah (Ni, Cu)3Sn4 dan Ni3Sn4. Hasil daripada analisis morfologi menggunakan FESEM dengan EDX menyatakan penuaan sesuhu pada suhu 150°C menyebabkan penebalan dan pengasaran struktur IMC serta menjadikan bentuknya kepada lebih sfera. Tebal IMC bagi kedua–dua penyudahan yang dikaji adalah lebih tinggi bagi bebola patri yang lebih kecil. Daripada hasil kajian juga, didapati bahawa kadar pertumbuhan IMC adalah lebih tinggi apabila pematrian dilakukan atas penyudahan kuprum berbanding ENEPIG. Hasil kajian juga menunjukkan ketebalan IMC adalah berkadaran dengan masa penuaan sesuhu. Kata kunci: Flip chip; Kumprum dan Nikel tanpa elektrod; Palladium tanpa elektrod; Emas rendaman (ENEPIG); Pelogaman di bawah pateri (UMB) Ni/Pd/Au Flip chip technology provides the ultimate in high I/O–density and count with superior electrical performance for interconnecting electronic components. Therefore, the study of the intermetallic compounds was conducted to investigate the effect of solder bumps sizes on several surface finishes which are copper and Electroless Nickel/Electroless Palladium/Immersion Gold (ENEPIG) which is widely used in electronics packaging as under–bump metallization (UBM) for flip–chip application nowadays. In this research, field emission scanning electron microscopy (FE–SEM) analyses were conducted to analyze the morphology and composition of intermetallic compounds (IMCs) formed at the interface between the solder and UBM. The IMCs between Sn–Pb and lead–free solder with Cu surface finish during reflowing were mainly (Cu, Ni)6Sn5 dan Cu6Sn5. While the main IMCs formed between Sn–Pb and lead–free solder on ENEPIG surface finish are (Ni, Cu)3Sn4 and Ni3Sn4. The results from FESEM with energy dispersive x–ray (EDX) have revealed that isothermal aging at 150°C has caused the thickening and coarsening of IMCs as well as changing them into more spherical shape. The thickness of the intermetallic compounds in both finishes investigated ware found to be higher in solders with smaller bump size. From the experimental results, it also appears that the growth rate of IMCs is higher when soldering on copper compared to ENEPIG finish. Besides that, the results also showed that the thickness of intermetallic compounds was found to be proportional to isothermal aging duration. Key words: Electroless nickel; electroless palladium; immersion gold (ENEPIG); flip chip; Ni/Pd/Au Under–bump metallization (UMB)
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