Mounting instructions SKiM(R) Preliminary Basic comments on baseplateless module design In standard modules with baseplates, the geometry of the interface between the module case and heat sink is only controlled by the shape of the baseplate. Therefore, modules with baseplates are specified with a convex baseplate curvature to allow for a good thermal contact when mounted. The concept of baseplateless design is to achieve a good thermal contact in the active area of the DCB-substrate close to the dies by an implemented pressure contact system (SKiiP technology). This pressure contact system is activated by mounting the module onto the heat sink. During this process, the spring contact system is activated and assures a close contact between the heat sink and the module. The integrated pressure contact system does not require a pre-shaped module base. Therefore, the specification limits for the base geometry of an unmounted module are more than for baseplate modules. SKiiP technology constant distance = constant pressure on the DCB Bottom view of a SKiM 4 module, mounted on a transparent heat sink. The evenly distributed thermal grease layer shows the homogeneous pressure distribution. (c) by SEMIKRON 2003-09-04 1 SKiM(R) 1.2 ESD protection SKiM 4/5 modules are sensitive to electrostatic charges. All SKiM modules are ESD protected during transport, storage and mounting process with an ESD cover. When unpacking the module and during assembly use conductive grounded wristlet and a conductive grounded working place. 1.3 Sectional drawings of SkiM 4 , SkiM 5 Interface drawings for mechanical design are available in PDF-format. PDF - files are available in the internet: http://www.semikron.com/products/skim_.html 2 Module assembly 2.1 Heat sink specification To obtain the maximum thermal conductivity of the module, the mounting area on the heat sink must be clean and free of grease and particles. The mechanical specification of the mounting area is: Flatness: 50 m per 100 mm Roughness Rz : 6,3 m Machined without overlaps 2.2 Specification for bottom surface of module The mounting surface of SKiM modules must be free from grease and particles. Due to the manufacturing process of the DBC substrate, the bottom side of the SKiM might show scratches, holes or similar marks. The following figures (Fig 3.1 - Fig 3.3) define surface characteristics, which do not affect the thermal conduction behaviour. Reworked bottom surfaces (Fig. 3.4) have to comply with the surface specification according to Fig. 3.1 - Fig. 3.3 Fingerprints do not affect the thermal behaviour. 600 m 10 m 300 m Fig. 3.1: Scratches on the SKiM bottom surface. 1.0 mm = 300 m Fig. 3.2: Etching hole (hole down to substrate level ) in the SKiM bottom surface (c) by SEMIKRON 2003-09-04 2 SKiM(R) 2.0 mm < 250 m Fig. 3.3: Etching holes (hole not down to substrate level) in the SKiM bottom surface Fig. 3.4: SKiM bottom surface after rework 2.3 Application of thermal grease To avoid air gaps at the interface between the module and the heat sink a layer of thermal grease must be applied. The function of the grease is to flow according to the shape of the interface, allowing a metal-to-metal contact where it is possible and filling the remaining gaps. Recommended thermal grease material is Wacker-Chemie P 12. The thermal grease can be applied either to the base area of the module or to the mounting area of the heat sink. A hard rubber roller or a screen print (mesh-size 43T) is recommended for an even distribution of the grease. The thickness of the applied grease layer should be 40 - 60 m. It can be checked by a measuring gauge (e.g. Fa. ELCOMETER Instruments GmbH, Himmlingstr. 18, 73434 Aalen, Tel. +49-7366919283: Sechseck-Kamm 5 - 150 m). 2.4 Mounting of the module After applying the thermal grease, the SKiM 4 or SKiM 5 is placed on the heat sink. The mounting screws are inserted and evenly tightened by hand (approx. 0.5 Nm) and afterwards tightened to the final torque (ref. table 3.1) in the sequence shown in Fig. 3.5 (SKiM 4) or Fig 3.6 (SKiM 5). Torque wrenches with automatic release are strongly recommended. Subsequent tightening of the screws is not allowed. (c) by SEMIKRON 2003-09-04 3 SKiM(R) The minimum torque already establishes the specified thermal contact. A further increase of the maximum mounting torque will not improve the thermal contact. . Module Screw Washer SKiM 4 SKiM 5 M5 M5 M5 - ISO 7092 M5 - ISO 7092 Torque min. max. 2 3 2 3 unit Nm Nm Table 3.1: Torque specification for heat sink fixing 1 3 4 2 Fig. 3.5: Torquing sequence SKiM 4 8 1 3 5 6 4 2 7 Fig. 3.6: Torquing sequence SKiM 5 Module Screw SKiM 4 SKiM 5 M6 M6 Torque min. Max. 4 5 4 5 unit Nm Nm Table 3.2: Torque specification for terminals The maximum immersion depth of the screws for SkiM 4 and SkiM 5 may not exceed 9 mm. (c) by SEMIKRON 2003-09-04 4 SKiM(R) 2.5 Mounting of DC bus bars The functionality of the pressure contact system can be disturbed by too high pulling forces on main terminals, resulting in malfunction of the module. For the maximum allowed pulling forces per terminal on SKiM 4 and SKiM 5 modules refer to table 3.4. and Fig. 3.7 Force: FX FY F+Z Maximum allowed force < 100 N < 100 N < 100 N F-Z < 500 N Remark only for short time during mounting - Table 3.4: Maximum allowed pulling forces per terminal Fig. 3.7: Maximum allowed pulling forces In order to reduce pulling forces, dc link bus-bar and cables may be fixed by additional posts (Fig. 3.8) dc bus bar / ac terminals fixing post heat sink Fig. 3.8 : Recommended dc-bus bar assembly (c) by SEMIKRON 2003-09-04 5 SKiM(R) 3 Driver- Assembly For SKiM 4 and SKiM 5 the following IGBT-gate drivers with protection functions (for details refer to chapter SEMIDRIVER) are available: Module SKiM 4 SKiM 5 Types all all IGBT Driver SKHI 64 SKHI 65 Table 3.5: Available SKiM SEMIKRON gate driver The SEMIDRIVER or other driver printed circuit boards (PCBs) can easily be snapped onto the SKiM module. Lateral movements of the driver PCB during mounting are not allowed to avoid damage of the spring contacts. It is recommended to use guiding pins temporarily located in the posts as shown in Figure 3.9 (pins can be ordered by SEMIKRON). Fig. 3.9: SKiM module with guiding pins Fig. 3.10: Alignment of the PCB on the SKiM module and assembly. (c) by SEMIKRON 2003-09-04 6 SKiM(R) For mounting the PCB on the SKiM module all snappers have to be snapped in according to Fig. 3.11. The guiding pins then have to be removed and the PCB has to be fixed by self tapping screws EJOT PT K30x8 WN 1452 (the details of screw head design can be chosen by the customer). Click !! Holes for screws Fig. 3.11: Final assembly of driver PCB . Table 3.6 specifies the minimum and maximum torque values for the PCB mounting screws. The usage of torque wrenches with automatic release is strongly recommended. Subsequent tightening of the screws is not allowed. Module Screw Value Unit min. Max. SKiM 4 PT K...30x8 0,9 1,1 Nm SKiM 5 PT K...30x8 0,9 1,1 Nm Table 3.6: mounting torque for PCB mounting screws Recommended screws may be supplied by EJOT Verbindungstechnik GmbH, http://www.ejot.de, info@ejot.de. (c) by SEMIKRON 2003-09-04 7