Growth competition between layer-type and porous-type Cu 3 Sn in microbumps

Electronic devices need to work at high temperature in some fields for a long time, peculiarly step soldering technology, primary packaging and flip-chip connections, etc., along with the application of electronic products more and more widely. These phenomena promote the further development of hightemperature solders. Because of the high melting temperatures of Sn-Ag and Sn-Sb, they are suitable for high-temperature fields such as automotive electronics and avionics. In this review, the influences of trace elements and nanoparticles on microstructure, intermetallic components (IMC) growth, mechanical properties, wettability, melting behavior, and creep behavior of Sn-Ag and Sn-Sb solders have been summarized systematically. It was found that the addition of trace elements or nanoparticles into solders to be beneficial in improving the performance of Sn-Ag and Sn-Sb solders. Besides, the melting behavior of the solder at high temperatures can be further improved if Sn-Ag and Sn-Sb are used better as high-temperature solders.

Section: Sn-agmentioning

confidence: 99%

Microstructure and properties of Sn-Ag and Sn-Sb lead-free solders in electronics packaging: a review

Wang

Zhang

2021

“…As a result, it was concluded that the thickness of the Sn-based alloy used for the TLPB process should be relatively small in order to carry out the assembly in a reasonable processing time. This was the case for recent TLPB research works for microelectronic packaging [16][17][18][19] which have used Sn-based solder thicknesses lower than 10 lm. However, all these studies performed by using electrodeposited layers of Cu and solder alloys, report formation of mainly two key defects: classical Kirkendall voids at interface between Cu and IMCs and above all numerous porosities and very large cavities inside the joints.…”

Section: Introductionmentioning

confidence: 99%

Bubble formation and growth during Transient Liquid Phase Bonding in Cu/SnAg system for microelectronic packaging

Barik

Gillot

Hodaj

2021

In this work, we study the Transient Liquid Phase Bonding (TLPB) for flip chip interconnexion using copper pillar and SnAg solder alloy technologies. Cu and SnAg bumps with a size of 90 9 90 lm 2 were deposited using electroplating process with a thickness of 20 lm and 15-30 lm, respectively. Two types of Cu were deposited: with or without additives. Before the TLPB process, soldering experiments with or without pre-reflow were carried out at 250 °C in order to insure a good filling of the joint. Afterwards, isothermal holdings up to 4 h were performed in the temperature range between 250 and 350 °C under air atmosphere. Two main aspects of Cu/SnAg system are studied and analyzed: (i) the evolution of morphology, microstructure, and growth kinetics of intermetallics (IMCs) during the TLPB and especially (ii) the formation and growth of gas bubbles within the liquid solder during TLPB process. Destructive (scanning electron microscopy) and non-destructive (X-ray) characterizations are performed to analyze and understand the evolution of microstructure as well as the formation and evolution of cavities within the joint during the TLPB process. Non-destructive X-ray radiography with 5 lm resolution and 3D X-ray tomography analysis with 0.7 lm resolution were conducted for the same joint at different steps of its evolution between its initial state (just after the soldering process: about 3 min at 250 °C) and 4 h at 250 °C in order to follow ''in situ'' the evolution of volume defects inside the joint and especially the evolution of gas bubbles within the joints.

“…[4][5][6] When the size of Cu pillar bumps reduces to several microns, the physical characteristics of the solder joint will change signi cantly, which raises new potential threats. [7,8] During the re ow and solid-state aging process, the excessive growth of intermetallic compound (IMC) would deplete the Sn solder [9]. Subsequently, abundant porous Cu 3 Sn is produced in the interface of Cu/Sn, [10,11,6] which decreases the mechanical strength of the solder joint.…”

Section: Introductionmentioning

confidence: 99%

“…Previous literatures have pointed out that a porous-type of Cu 3 Sn is formed due to the decomposition of Cu 6 Sn 5 . [12,13,7] Andriy M. Gusak et al [10] concluded that one of the necessary condition for the porous structure formation is the overgrowth of IMC to deplete the free Sn. Therefore, retarding the overgrowth of IMC has become an increasingly important issue to inhibit the formation of porous Cu 3 Sn and ensure the stability of micro-interconnects.…”

Section: Introductionmentioning

confidence: 99%

Inhibiting effects of the Ni barrier layer on the growth of porous Cu3Sn in 10-μm microbumps

Liu

Yang

Ling

et al. 2021

With the shrinkage of size, porous Cu 3 Sn have become a new potential threat of the reliability in micron Cu pillar bump. The formation of porous Cu 3 Sn is contributed the decomposition of Cu 6 Sn 5 , which is caused by the overgrowth of intermetallic compounds (IMC) and the stress introduced by the phase transition of Cu 6 Sn 5 . In this paper, uniform Ф10 µm Cu/Sn and Cu/Ni (~0.6 μm)/Sn microbumps have been fabricated by multilayer electrodeposition and the effect of the Ni layer on the growth behavior of porous Cu 3 Sn was investigated by comparing the evolution of IMC in Cu/Sn and Cu/Ni/Sn bumps aged at 170 ℃ and 200 ℃. The ~0.6 μm Ni layer can effectively retard the Cu atoms diffusion, which can hinder IMC from overgrowth. Moreover, with the help of X-ray diffraction (XRD), the ability of the Ni layer in stabilizing Cu 6 Sn 5 phase is strengthened, which weakens the tendency of the porous Cu 3 Sn formation.Under the conjoint action of retarding the growth of IMC and stabilizing Cu 6 Sn 5 phase, the Ni layer can inhibit the formation of porous Cu 3 Sn e caciously.