An improved molten solder injection head having a vacuum filter and differential gauge system is provided. In one aspect, an injection head is provided. The injection head includes: a reservoir; an injection port on a bottom of the injection head connected to the reservoir; a vacuum port adjacent to the injection port on the bottom of the injection head connected to a vacuum source; and a filter disposed between the bottom of the injection head and the vacuum source. A method for molten solder injection using the present injection head is provided.