If you require metal joints that are strong and permanent, brazing and welding are probably your best bets. They both can integrate into production processes and they both use filler metals. However, welding joins metals by melting and fusing them together -- typically with the addition of a filler metal. The result is generally a very strong joint. Welding temperatures start at the melting point of the metals being joined, so you're dealing with considerable heat which can create issues with distortion or warping if the base metals are not thick. Additionally, the process can be energy intensive due to the level of heat required.