• Journal of the Microelectronics and Packaging Society
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• v.12 no.1 s.34
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• pp.87-93
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• 2005

Interfacial reactions between 48Sn-52In solder and $0.1{\mu}m$ Ti/3 ${\mu}m$ Cu/Au under bump metallurgies(UBM) with various Au thickness of $0.1{\~}0.7{\mu}m$ have been investigated after solder reflow at $150^{\circ}C,\;200^{\circ}C$, and $250^{\circ}C$ for 1 minute. Ball shear strength and shear energy of the Sn-52In solder bump on each UBM was also evaluated. With reflowing at $150^{\circ}C$ and $200^{\circ}C$, $Cu_6(Sn,In)_5$ and $AuIn_2$ intermetallic compounds were formed at UBW solder interface. However, UBM was consumed almost completely with reflowing at $250^{\circ}C$. While ball shear strength was not consistent with UBM/solder reactions, ball shear energy matched well with UBM/solder reactions.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2003.09a
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• pp.193-215
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• 2003

Fracture Mechanism of Flip Chip Electromigration Failure - Mostly caused by Cathode Depletion at the UBM/Solder Interface Guideline to Increase Electromigration Resistance Material Selection: Sn/Ag(/Cu) > Pb/63Sn Cu UBM > Ni UBM (but, Solder Material combination) UBM Design: thick UBM is preferable (but, Stress Issue) Pad open/UBM size: as large as possible (but, pad size & pitch limit)

• Korean Journal of Materials Research
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• v.10 no.12
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• pp.853-863
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• 2000

In this study, a new UBM materials system for solder flip chip interconnection of Cu pads were investigated using electroless copper (E-Cu) and electroless nickel (E-Ni) plating method. The interfacial reaction between several UBM structures and Sn-36Pb-2Ag solder and its effect on solder bump joint mechanical reliability were investigated to optimife the UBM materials design for solder bump on Cu pads. Fer the E-Cu UBM, continuous coarse scallop-like $Cu_{6}$ $Sn_{5}$ , intermetallic compound (IMC) was formed at the solder/E-Cu interface, and bump fracture occurred this interface under relative small load. In contrast, Fer the E-Ni/E-Cu UBM, it was observed that E-Ni effectively limited the growth of IMC at the interface, and the Polygonal $Ni_3$$Sn_4$ IMC was formed because of crystallographic mismatch between monoclinic $Ni_3$$Sn_4$ and amorphous E-Ni phase. Consequently, relatively higher bump adhesion strength was observed at E-Ni/E-Cu UBM than E-Cu UBM. As a result, it was fecund that E-Ni/E-Cu UBM material system was a better choice for solder flip chip interconnection on CU PadS.

• Journal of the Microelectronics and Packaging Society
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• v.14 no.3
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• pp.43-49
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• 2007

Thickness of intermetallic compounds and consumption rates of under bump metallurgies (UBMs) were investigated in wafer-level solder bumping with variations of UBM materials and reflow times. In the case of Cu UBM, $0.6\;{\mu}m-thick$ intermetallic compound layer was formed before reflow of Sn solder, and the average thickness of the intermetallic compound layer increased to $4\;{\mu}m$ by reflowing at $250^{\circ}C$ for 450 sec. On the contrary, the intermetallic layer had a thickness of $0.2\;{\mu}m$ on Ni UBM before reflow and it grew to $1.7\;{\mu}m$ thickness with reflowing for 450 sec. While the consumption rates of Cu UBM were 100nm/sec fur 15-sec reflow and 4.50-sec for 450-sec reflow, those of Ni UBM decreased to 28.7 nm/sec for 15-sec reflow and 1.82 nm/sec for 450-sec reflow.

• Journal of the Microelectronics and Packaging Society
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• v.7 no.2
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• pp.55-62
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• 2000

The wetting balance test was performed in an attempt to estimate the wetting properties of the UBM-coated Si-wafer on one side to the Sn-Pb solder. The wetting curves of the one and both side-coated UBM layers had the similar shape and the parameters characterizing the curve shape showed the similar transition tendency to the temperature. The wetting property estimation was possible with the new wettability indices from the wetting curves of one side-coated specimen; $F_{min}$, $F_{s}t_{s}$ and $t_s$. For UBM of Si-chip, Au/Cu/Cr UBM was better than Au/Ni/Ti in the point of wetting time. The contact angle of the one side coated Si-plate to the Sn-Pb solder could be calculated from the force balance equation by measuring the static state force and the tilt angle.

• Journal of the Microelectronics and Packaging Society
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• v.12 no.2 s.35
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• pp.95-103
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• 2005

The interfacial reaction between 42Sn-58Bi solder (in wt.$\%$ unless specified otherwise) and electroless Ni-P/immersion Au has been investigated before and after thermal aging, with a focus on formation and growth of an intermetallic compound (IMC) layer, consumption of under bump metallurgy (UBM), and bump shear strength. The immersion Au layer with thicknesses of 0 (bare Ni), 0.1, and $1{\mu}m$ was plated on the $5{\mu}m$ thick electroless Ni-P ($14{\~}15 at.\%$P) layer. Then, the 42Sn-58Bi solder balls were fabricated on three different UBM structures by screen-printing and pre-reflow. The $Ni_3Sn_4$ layer (IMC1) was formed at the joint interface after pre-reflow for all the three UBM structures. On aging at $125^{\circ}C$, a quaternary phase (IMC2) was observed above the $Ni_3Sn_4$ layer in the Au-containing UBM structures, which was identified as $Sn_{77}Ni{15}Bi_6Au_2$ (in at.$\%$). The thick $Sn_{77}Ni{15}Bi_6Au_2$ layer deteriorated the integrity of the solder joint and the shear strength of the solder bump was decreased by about $40\%$ compared with non-aged joints.

• Journal of the Microelectronics and Packaging Society
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• v.8 no.1
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• pp.45-51
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• 2001

The effects of wettability and surface oxidation on the low temperature and ultra-fine solder bump formation have been studied. Difference sequences of near eutectic In-Ag and eutectic Bi-Sn solders were evaporated on Au/Cu/Cr or Au/Ni/Ti Under Bump Metallurgy (UBM) pads. Solder bumps were formed using lift-off method and were reflowed in Rapid Thermal Annealing (RTA) system. The solder bumps in which In was in contact with UBM in In-Ag solder and the solder bumps in which Sn was in contact with UBM in Bi-Sn solder showed better bump formability during reflow than other solder bumps. The ability to form spherical solder bumps was affected mainly by the wettability of solders to UBM pads.

• Journal of the Microelectronics and Packaging Society
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• v.19 no.2
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• pp.35-39
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• 2012

We studied interfacial reaction and bonding characteristics of a flip chip bonding with the viewpoint of formation behavior of intermetallic compounds. For this purpose, Sn-0.7Cu and Sn-3Cu solders were reflowed on the Al/Cu and Al/Ni UBMs. When Sn-0.7Cu was reflowed on the Al/Cu UBM, no intermetallic compounds were formed at the solder/UBM interface. The $Cu_6Sn_5$ intermetallic compounds formed by reflowing Sn-3Cu solder on the Al/Cu UBM were spalled from the interface, resulting in delamination of the solder/UBM interface. On the other hand, the $(Cu,Ni)_6Sn_5$ intermetallic compounds were formed by reflowing of Sn-0.7Cu and Sn-3Cu on the Al/Ni UBM and the interfacial bonding between the Sn-Cu solders and the Al/Ni UBM was kept stable.

• Journal of Welding and Joining
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• v.18 no.6
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• pp.74-82
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• 2000

The fluxless wetting properties of UBM-coated Si-wafer to the binary lead-free solders(Sn-Ag, Sn-Sb, Sjn-In, Sn0Bi) were estimated by wetting balance method. With the new wettability indices from the wetting curves of one side coated specimen, the wetting property estimation of UBM-coated Si-wafer was possible. For UBM of Si-chip, Au/Cu/Cr UBm was better than au/Ni/TI in the point of wetting time/ At general reflow process temperature, the wettability of high melting point solders(Sn-Sb, Sn-Ag) was better than that of low melting point one(Sn-Bi, Sn-In). The contact angle of the one side coated Si-plate to the solder could be calculated from the force balance equation by measuring the static state force and the tilt angle.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2002.11a
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• pp.33-37
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• 2002

본 연구에서는 전해도금법을 이용하여 플립칩용 Ni, Ni-Cu 합금 UBM (Under Bump Metallurgy) 및 Sn-Ag 무연 솔더 범프를 형성하였다. 솔더 범프의 전해도금시 고속도금 방법으로 균일한 범프 높이를 갖도록 하는 도금 조건 및 도금 기판의 역할로서의 UBM의 영향을 조사하였다. Cu/Ni-Cu 합금/Cu UBM을 적용한 경우 음극시편의 전극 접점수를 증가시켰을 때 비교적 균일한 솔더 범프를 형성시킬 수 있었던 반면, Ni UBM의 경우는 접점수를 증가시켜도 다소 불균일한 솔더 범프를 형성하였다. 리플로 시간을 변화하여 범프 전단 강도 및 파단 특성을 조사하였는데 Ni UBM의 경우 Cu/Ni-Cu 합금/Cu UBM에 비해 전단강도가 다소 낮은 값을 가졌고 금속막이 웨이퍼에서 분리되는 파괴 거동이 관찰되었다.