Abstract
Copper wires have been attracting much attention for Large Scale Integration (LSI) bonding because of their excellent mechanical and electrical properties, in addition to their low material cost. The ends of these wires are usually joined to pads or through-holes on a printed circuit board, and lead-free soldering is one of the popular bonding methods. Since the deformation resistance of solder is lower than that of copper, especially in slow deformation due to creep, the strain tends to be increased in the solder and concentrated near the copper/solder joint interface. Thus, fracture frequently occurs at this interface and may influence the quality of the product. It is therefore important to evaluate the bonding strength of thin copper wire and lead-free solder. In this paper, pullout tests of thin copper wire from lead-free solder were carried out, and the pullout behavior of the wires was observed. The bonding strength was evaluated based on the actual bonded area on the copper wire surface. Finally, the strength of the thin copper wire/solder joint was summarized using the shear and tensile strengths of the copper/solder interface as well as the tensile strength of the copper wire.
Highlights
Gold wire is a very popular interconnection material in semiconductor packaging
Considering that these curves coincide are found bothare in found fast and pullout tests.pullout. Considering that these that curves coincide the characteristics bothslow in fast and slow tests. Considering these curves with coincide with obtained by the the show load-displacement diagramdiagram obtained by the tensile tests oftests the of copper wire,wire, the curves show the with the the load-displacement load-displacement diagram obtained by the the tensile tensile tests of the copper copper wire, the curves curves show the plastic property of copper wires
Examples of the copper wire surface observed by SEM after the fast and slow pullout tests are shown in Figures 6 and 7, respectively
Summary
Gold wire is a very popular interconnection material in semiconductor packaging. alternative metals gradually come to be used for wiring to reduce the cost [1,2]. It is understood that the pullout strength cannot be evaluated accurately only from the size and shape of Crystals 2017, 7, 255 solder fillet. The pullout strength to ofthe thinheight wire of from solder the is still important considering static load was roughly proportional thelead-free fillet. Pullout tests of thin copper wire lead-free solder were carried out,Since and the pullout strength cannot be evaluated accurately only from from the size and shape of solder fillet. The bonding strength was examined based on the through-hall components have a considerable margin of safety due to the relatively long andactual large bonded area between wire solder. The strength of the thin copper wire/solder joint solder/metal interface,the very littleand research has been performed on this topic. Pullout tests of thin copper wire from lead-free solder were carried out, and the.
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