From 半(はん)田(だ) (handa, “solder”) + 付(つ)け (tsuke, “attaching”, 連(れん)用(よう)形(けい) (ren'yōkei, “stem or continuative form”) of the verb 付(つ)ける (tsukeru, “to attach”)).
はんだづけ or ハンダづけ • (handazuke)