A thermal module structure includes an aluminum base having a heat pipe receiving groove formed on one side thereof; a heat dissipation unit including a plurality of radiation fin assemblies or heat sinks and being provided with a first heat pipe receiving section; a plurality of heat pipes made of a copper material and respectively having a heat absorption section and a horizontally extended condensation section; and a copper embedding layer provided on surfaces of the heat pipe receiving groove and the first heat pipe receiving section. The aluminum base and the heat dissipation unit are horizontally parallelly arranged. The heat absorption sections are fitted in the heat pipe receiving groove, and the condensation sections are extended through the first heat pipe receiving section. With the copper embedding layer, the aluminum base and the heat dissipation unit can be directly welded to the heat pipes.