A　self-made　solidification　controlling　facility　was　developed　in　accordance　with　the　principle　of　directional　solidification　to　study　the　solidification　behavior　of　SAC305　solder　alloy　and　the　effect　of　directional　solidification　on　the　alloy　microstructure.　The　microstructure　of　the　tin-rich　phase　grows　with　significant　orientation　under　the　rapid　cooling　conditions.　Increasing　the　cooling　rate　can　enhance　the　continuity　of　columnar　tin-rich　phase　and　is　likely　to　inhibit　the　secondary　dendrite　growth.　Rapid　cooling　reduces　the　size　and　disperses　intermetallic　compounds　significantly,　resulting　in　the　increase　of　the　microhardness　of　the　solder.