其目的系正确地辨别不容易氧化之焊接材料。 Cu内核球1系包括：具有规定之大小而在半导体封装和印刷电路基板之间来确保间隔之Cu球2以及被覆Cu球2之焊接层3。Cu内核球1系在温度25℃、湿度40%之室内之150℃恒温槽之72小时之燃烧试验后之L*a*b*表色系之亮度为62.5以上，燃烧试验前之焊接材料之L*a*b*表色系之亮度为65以上，并且，L*a*b*表色系之黄色度为7.0以下。

The present invention accurately distinguishes a soldering material which is less apt to oxidize. The soldering material is Cu-core balls which comprise: Cu balls that have a given size and ensure a space between a semiconductor package and a printed board; and a solder layer with which each Cu ball has been coated. After a 72-hour burning test in a 150 DEG C thermostatic chamber inside a room having a temperature of 25 DEG C and a humidity of 40%, the Cu-core balls have a lightness according to the L*a*b* color system of 62.5 or greater. Before the burning test, the soldering material has a lightness according to the L*a*b* color system of 65 or greater and a yellowness according to the L*a*b* color system of 7.0 or less.