Sn-based brazing filler metal capable of achieving high-strength interconnection of CSP devices

Abstract

The invention discloses Sn-based brazing filler metal capable of achieving high-strength interconnection of CSP devices. The Sn-based brazing filler metal comprises Al nanowires, Cu submicron particles, Bi and Sn. The Al nanowires are added, a structure similar to a net can be formed to be distributed in the internal structure of a welding spot, Bi-rich and Sn-rich crystal grains can be tightly wound together, Cu submicron particles can react with a matrix Sn to form Cu6Sn5 intermetallic compound particles, part of the particles can be gathered at the grain boundary of the Bi-rich and Sn-rich crystal grains, the effect of pinning the Al nanowires is achieved, so that the Al nanowires and the Cu6Sn5 intermetallic compound particles can be coupled to strengthen the welding spots; in addition, in a welding spot interface area, part of Al nanowires and Cu6Sn5 intermetallic compound particles can be enriched in an interface layer area, so that rapid growth of interface intermetallic compounds is prevented, and therefore, the welding spots can still keep high strength and long service life in the service period, and the requirement for high reliability of the CSP devices can be met.

Description

Technical field [0001] The present invention relates to an Sn-based solder, in particular a high strength can be achieved CSP devices interconnected Sn-based solder, chip-level packaging technologies. Background technique [0002] CSP (Chip Scale Package) That chip scale package is the latest generation of memory chip packaging technology, CSP packaging can make than the chip area and packaging area exceeds 1: 1.14, very close to 1: Ideally 1, the absolute size is only 32 square millimeters, about the ordinary BGA (ball grid array package ball grid array package) 1 / 3, only the equivalent of 1 / 6 TSOP (thin small Outline package thin small outline package) memory chip area, the BGA package compared, CSP package may be up to three times the storage capacity under the same space. Small package CSP is the main features of the product. Due to changes in the structure of the package, opposite QFP (Quad Flat Package Quad Flat Package) and BGA devices devices, the number of solder joints ...

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Problems solved by technology

Another example is the Sn-based lead-free solder disclosed in Chinese patent ZL201811096803.6, which includes (0.5-1.0%) Cu, (0.05-0.35%) Ni, (0.003-0.008%) Se, (0.01-0.03%) Zr, (0.4 ~0.6%) Ga, (0.04~0.06%) Nd, and the rest is Sn. The wettability of solder joints, the thickness of the solder joint interface, and tin whiskers have been studied. By adding a certain amount of Nd, Zr, Se, and Ga, the It has good wettability, can effectively inhibit the growth of intermetallic compounds at the interface of solder joints, and inhibit the growth of tin whiskers, but there is no record that the added elements can improve the mechanical properties of solder and the performance of solder joints

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