Patent ID: 8020607

Claim:
A heat exchanger having a header, the heat exchanger comprising: a plurality of tube insertion holes, each shaped to receive an end of a tube therein, a filler metal groove spaced a distance from the tube insertion hole and extending substantially the length of the header, a plurality of lead grooves, each extending between the filler metal groove and a corresponding one of the plurality of tube insertion holes to provide a sole fluid path therebetween, and a filler metal insert completely contained within the filler metal groove so that, with a rising temperature, melted filler metal flows from the filler metal grove, through the plurality of lead grooves, and down around a contact area of the tube and the tube insertion hole so as to allow fusion, and wherein each lead groove is sized to meter the flow of filler material into a corresponding tube insertion hole, wherein a portion of at least one of the plurality of the tube insertion holes expands outwardly to provide additional clearance between the tube and the tube insertion hole.