Patent WO-2020182361-A1 (WO)
Title: Method for making a cohesive connection by fluxless chip- or element soldering, gluing or sintering using a material preform
Inventor: ULRICH HOLGER
IPC: H01L21/58
Filed: 2020-01-27
Abstract: A method (100) for making a cohesive connection of a first component (1) (e.g., a DCB (Direct Copper Bonding) substrate) of a power semiconductor module to a second component (2) (e.g., an electronic component, in particular a semiconductor) of the power semiconductor module comprises the steps of: applying (101) a bonding material preform (14) to a bonding surface (3) of the first component (1), the bonding material preform (14) comprising a first surface (7) to be placed on the bonding surface (3) of the first component (1) and a second surface (6), opposite the first surface (7), which comprises one or more locating structures (13, 15, 16) suitable for locating the second component (2); arranging (103) the second component (2) on the surface (6) of the bonding material preform (14) opposite to the surface facing the first component (1) and located using the locating structures (13, 15, 16); and processing (104) (e.g., by heating and/or applying pressure) the complete area of the bonding material (9). The locating structures (13, 15, 16) ensure that the second component (2) is accurately and firmly retained in position in relation to the bonding material preform (14). The locating structures (13, 15, 16) may comprise a raised wall (15) or raised indexes (16) protruding from the otherwise substantially flat second surface of the bonding material preform (14). The bonding material preform (14) may be formed by preparing (105) a flat bonding material preform (4) and modifying (106) the flat material preform (4) to form a material preform (14) comprising one or more locating structures (13) suitable for locating the second component (2). The method may comprise, after applying the material preform (4, 14) to the bonding surface of the first component (1), a step of fixing (102) the material preform (4, 14) to the first component (1) by heating in a locally delimited partial area (5) of the material preform, wherein the heating may be provided by a laser (17) or by a heating probe (8). The bonding material (9) may be a sintering material, a solder, an organic foil or a thermosetting adhesive. The material preform (14) may comprise a stabilizing means (30), which keeps a specific gap between the surfaces being connected during the period when the material of the material preform (14) is at a raised temperature and may therefore be in a liquid state. This may be the case if the method is used to simultaneously connect a plurality of surfaces in a single stack but using material preforms (4, 14) of differing materials, such as a sintering material and a solder material. The stabilizing means (30) may be solid spacer means (e.g., substantially spherical bodies made of metal (in particular copper), glass or ceramics, or a wire mesh, in particular made of metal (in particular copper)) which are incorporated in a soldering material preform (14). It is also possible to arrange a distribution of the stabilizing means (30) within the material preform (14) to ensure a separation between the finally connected surfaces which is constant, or which is at an angle, for example increases across the surface from one side to another, e.g. when the stabilizing means (30) comprises a copper wire mesh.