Thermomechanical reliability of a Cu/Sn-3.5Ag solder joint with a Ni insertion layer in flip chip bonding for 3D interconnection

Tang, Chu; Zhu, Wenhui; Chen, Zhuo; Wang, Liancheng

doi:10.1007/s10854-021-05819-4

Cited by 6 publications

(1 citation statement)

References 30 publications

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“…Since the Sn consumption was almost completed, we estimated Cu 6 Sn 5 and Cu 3 Sn growth-rate constants of about 140 nm/

and 29 nm/

, respectively. These values are in reasonable agreement with [ 41 ], wherein a growth-rate constant of 161.3 nm/

(Cu 6 Sn 5 + Cu 3 Sn) was obtained for a bonding temperature of 325 °C. From this, one can estimate a full IMC growth time of about 5 min when using 30 µm balls instead.…”

Section: Resultssupporting

confidence: 91%

Laser-Assisted Micro-Solder Bumping for Copper and Nickel–Gold Pad Finish

2022

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Flip-chip bonding is a key packaging technology to achieve the smallest form factor possible. Using copper as a direct under-bump metal and performing bonding under little force and at a low temperature eliminates the processing step for the deposition of a suitable wetting metal and offers an economical solution for electronic chip packaging. In this paper, various samples with copper and nickel–gold surface finishes are used to apply an in-house solder bumping, flip-chip bonding and reflow process to exhibit the bump-bond feasibility. Native oxides are reduced using process gases, and copper surface protection and solder wetting are achieved using copper formate. Lead-free 40 µm solder balls were bumped on 80 µm copper pads and 120 µm copper pillars to demonstrate a full intermetallic Cu–Cu bond as a base study for stacking applications. Using a low-force bonding technique, various chips with different dimensions were bonded at 0.5–16 MPa, followed by a reflow step at a maximum temperature of 270 ∘C. Then, 30 µm solder balls are utilized to bump the samples with NiAu and Cu bond pads at 50 µm pitch. A mean shear strength of 44 MPa was obtained for the 30 µm Cu samples. To the best of our knowledge, 30 µm solder bumping directly on the copper pads by producing copper formate is a novel research contribution.

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“…Since the Sn consumption was almost completed, we estimated Cu 6 Sn 5 and Cu 3 Sn growth-rate constants of about 140 nm/

and 29 nm/

, respectively. These values are in reasonable agreement with [ 41 ], wherein a growth-rate constant of 161.3 nm/

(Cu 6 Sn 5 + Cu 3 Sn) was obtained for a bonding temperature of 325 °C. From this, one can estimate a full IMC growth time of about 5 min when using 30 µm balls instead.…”

Section: Resultssupporting

confidence: 91%