Cu-Sn composites coatings by cold spray with wide ranges of particle size and shape (round to flake) were investigated regarding their intermetallic compound (IMC) formation. It was found when certain size and shape combination of Cu-Sn composite raw materials were employed, the embedded Cu-Sn IMCs such as Cu_6Sn_5 and Cu_3Sn were observed even in assprayed states without additional heat treatments. These results implied that the impact energy of colliding particles of the cold spraying could be enough to activate IMC compounding process. It seems that this can be also true in several composite systems that have relatively low activation energy of IMC compounding. After post annealing, the Cu_6Sn_5 formed in as-coated state were transformed into the Cu_3Sn phase and the residue of unreacted Sn particles were fully changed into the Cu_3Sn phase (Cu_6Sn_5→Cu_3Sn). These conversion processes also depended strongly on the choices of the shape and size combinations of Cu and Sn particles.
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