SEMITOP2,3,4 Press-Fit

Transcription

1 Mounting Instruction SEMITOP2,3,4 Press-Fit Revision: 03 Issue date: Prepared by: Roberto Agostini Approved by: Werner Obermaier Keyword: SEMITOP, mounting instructions, one screw mounting, no baseplate, press-fit pins, 12mm height, thermal paste, assembly, torque, washer, screw, heatsink. Revision history SEMITOP 2, 3, 4 with Press-Fit pins PCB specifications Specification for components close to module pins Matching the power module and the PCB Press-in setup Press-in process Basic requirements Press-in tool parameters Press-in control parameters Press-out setup Press-out tool parameters Press-out control parameters Reworking of the assembly module and PCB Multiple per PCB Heatsink specifications and preparation Module specifications Assembly Thermal grease application Standard thermal grease specification Assembling SEMITOP Press-fit+PCB onto heatsink ESD Protection Caption of figures Caption of tables References Disclaimer by SEMIKRON / Mounting Instruction / SEMITOP2,3,4 Press-Fit / PROMGT.1027/ Rev.3/ Template Mounting Instruction Page 1/14

2 Revision history SEMIKRON reserves the right to make changes without further notice herein Date Revision n Description First release Improvement of contents PTH tin plating details for direct soldering to the PCB New template and general review 14 Pages Update of Mounting specifications for SEMITOP (Table 6); - Harmonization of thermal grease thicknesses (Table 5). 14 by SEMIKRON / Mounting Instruction / SEMITOP2,3,4 Press-Fit / Page 2/14

3 1. SEMITOP 2, 3, 4 with Press-Fit pins SEMITOP Press-Fit is the alternative solution to SEMITOP solder mounting version. One step PCB assembly to the module is possible thanks to solder free terminals; replacement of PCB is also possible. The new platform is still 12mm height module in order to offer a 100% mechanical compatibility with the soldered version. The following chapters describe the assembly procedure and parameter specifications to fix the module to the PCB and onto the heatsink. 1.1 PCB specifications The following requirements as regards the Plated Through Hole (PTH) of the PCB need to be fulfilled according to international standard IEC in order to ensure the proper functioning. SEMIKRON performed all the qualification tests following these requirements. The qualification tests were done using a standard FR4 PCB with an immersion tin (I-Sn) surface finish. The following table shows the specification of the PTH: Table 1: Specification of PTH for the press-in process Min. Typ. Max. Recommended size of drill 1.6mm Drilled hole diameter 1.575mm 1.6mm 1.625mm Copper thickness in via 25µm Tin plating in via 0.5µm Final hole diameter 1.39mm 1.45mm 1.54mm Cu width of the Annular ring 100µm Thickness of PCB 1.6mm In case of soldering of Press-Fit pins directly to the PCB, the following table shows the PTH specification: Table 2: Specification of PTH for soldering of Press-Fit pins to the PCB Min. Typ. Max. Drilled hole diameter 2.10mm 2.15mm 2.25mm Copper thickness in via 25µm Tin plating in via 10µm Final hole diameter 2.00mm Cu width of the Annular ring 100µm Thickness of PCB 0.8mm 1.6mm by SEMIKRON / Mounting Instruction / SEMITOP2,3,4 Press-Fit / Page 3/14

4 The recommended hole diameter for the mounting post to fix the SEMITOP Press-Fit to the PCB should be in accordance with the following table: Table 3: Specification of PCB hole diameter for the mounting post Module type Diameter [mm] SEMITOP4 Press-Fit 3.6 SEMITOP3 Press-Fit 2 SEMITOP2 Press-Fit 2 Mounting post 1.2 Specification for components close to module pins Particular attention must be paid for those components that need to be placed close to the module pins like resistors, capacitors or diodes. A minimum distance of 4mm is required between the edge of these components and the center of the PTH; this ensures enough space for the pressing tool. Figure 1: Minimum distance between components and hole center of PTH by SEMIKRON / Mounting Instruction / SEMITOP2,3,4 Press-Fit / Page 4/14

5 2. Matching the power module and the PCB For a successful press-in process with high process capability, it is recommended to use equipment that allows control of relevant process parameters like force and distance. The following table shows an overview of the available presses and their main characteristics: Table 4: Specification of press-type Press type Control of force Control of distance Comments Manual, hydraulic and pneumatic Low Low Servo electric High High Additional visual inspection is recommended to ensure reliable press-in process Accurate control of speed and position enables instant reaction to changes of pressin force Servo electric presses are recommended to mate PCB and press-fit modules. SEMIKRON performed tests using an electric press by KISTLER. 2.1 Press-in setup The following picture shows a concept view of the press-in equipment: Figure 2: Schematic view of the press-in setup Press-in tool top SEMITOP press-fit module Module anchor pins PCB Space for press-fit pins Anchor post PCB holes for module anchor pins Press-in tool base Support part for PCB The lower part of the press-in tool must be designed in order to provide free space for the components mounted on the surface of the PCB. Therefore shape and size of the available space for pins and components depends on size and position of the components on the PCB. The anchor posts are needed to keep the PCB aligned during the press-in phase. The base of the anchor post should support the PCB during the press-in process and therefore has to have the same height than the support part to avoid bending of the PCB. The support part should be fixed to the press-in tool. The PCB will be first positioned onto the support part through the anchor posts. The module is then placed on the PCB and aligned via the module anchor pins. by SEMIKRON / Mounting Instruction / SEMITOP2,3,4 Press-Fit / Page 5/14

6 The module is pressed with the top of the press-in tool which has to be parallel to the support part and the press-in tool base. Particular care should be taken for the bottom part of the press-in tool top side, it has to be clean and free from any particles that could damage the module. 2.2 Press-in process Basic requirements To ensure a proper press-fit contact, the center of the press-fit pin head has to be at least 0.5mm below the top surface and at least 0.5mm above the bottom surface of the PCB (refer to the following picture). Figure 3: Press-in depth in PCB Center of press-fit pin head min. 0.5mm min. 1.6mm min. 0.5mm Press-in tool parameters The following parameters are based on SEMIKRON press-in tool in use: Press-in force per terminal: 95±10N Press-in speed: 5-10mm/s Press-in control parameters In case the press is equipped with the possibility to record the force and distance during the press-in process, the following relevant values should be considered. A typical force vs. distance profile for a press-in process is shown in the following picture. There are three sections that are typical for the press-in curve (valid only for the first insertion): Black curve: first raising section. The press-fit terminal slides into the holes and will be deformed to fit the holes. Here, maximum deformation of press-fit terminal occurs. Blue curve: second section. The pin heads are fully inserted into the holes and slides to the final position Red curve: third section. Sliding of the pin is stopped. The anchor pins get in contact with the PCB and they start to bend the PCB. The press-in process has to be stopped at the beginning of the second raising section (red curve) to avoid damaging the PCB. The press-in force for each terminal is between 95N±10N. If the press-in force did not show the typical shape with the intervals before mentioned, this could indicate faulty plating, improper diameter of the holes or pin displacement. by SEMIKRON / Mounting Instruction / SEMITOP2,3,4 Press-Fit / Page 6/14

7 Figure 4: Typical press-in diagram for a 26 pins module 2.3 Press-out setup The following picture shows a concept view of the press-out equipment: Figure 5: Schematic view of the press-out setup Press-out tool top PCB Centring pin SEMITOP press-fit module Space for press-fit module after press-out process Support part for PCB Press-out tool bottom Base of support part for PCB The lower part of the press-in tool should be fixed. The system module and PCB will be positioned onto the support part. The alignment is possible thanks to the centring pin. Between the module and the base of the support part some space is needed to provide clearance for the pushed out module. The module is pressed out with the upper tool that has to be aligned parallel to the lower part. Once the module is pressed-out, it will be located on the base of the support part. by SEMIKRON / Mounting Instruction / SEMITOP2,3,4 Press-Fit / Page 7/14

8 In the following picture the press-out process is shown: Figure 6: Press-out process Module+PCB is placed on the support part The press-out tool will start to go down until it will be in contact with the terminals; the terminals will slide out of the PCB The press-out tool stops to go down when it touches the support tool. The module will be located on the base of the support part Press-out tool parameters The following parameters are based on SEMIKRON press in use: Press-out force per terminal: > 40N Press-out speed: 2-5mm/s Press-out control parameters A typical force vs. distance profile for a press-out process is shown in the following picture. The curve exhibits a peak that indicates the breaking of the cold weld joint connection between terminal and PCB. Figure 7: Typical press-out diagram for a module with 26 pins Connections brake by SEMIKRON / Mounting Instruction / SEMITOP2,3,4 Press-Fit / Page 8/14

9 2.4 Reworking of the assembly module and PCB Each SEMITOP Press-Fit type can be used only once. In case the system module+pcb needs to be disassembled, following options are possible: Module can be reused by soldering the press-fit pins to the PCB. Due to the pin deformation by the initial press-in process, any additional press-in process will result in low holding forces between the terminal and the PCB hole and is therefore not recommended. 2.5 PCB can be reused. The number of times depends on the plating of the via : Multiple per PCB Sn > 0.5µm: PCB can be disassembled and used two additional times Au µm over µm Ni: PCB cannot be reused. It is possible to assemble multiple modules onto one PCB. In this case the modules can be pressed one by one (subsequently) or all at once. Pressing multiple modules at once requires a press-in tool according to the above detailed single tool. The tool has to ensure the correct levelling of the modules and PCB to avoid mechanical stresses. 3. Heatsink specifications and preparation To obtain the maximum thermal conductivity, the bottom side of the module must be free from dust and dirt. The heat sink must fulfil following mechanical specifications: Figure 8: Heat sink surface specifications 50 µm per 100 mm Heat sink Rz 6.3µm Flatness of heat sink mounting area must be 50µm per 100 mm (DIN EN ISO 1101) Roughness Rz 6,3 µm (DIN EN ISO 4287) No steps Machined without overlaps Surface of heat sink should be free of grease, e.g. by cleaning the heat sink in a fat-dissolving solvent. A good indication is given by the DIN 53364, surface tension 32 N/m. Tap holes must be free of turnings. The supplier of the heat sinks should chose adequate packaging to avoid contamination and mechanical damage during transport. by SEMIKRON / Mounting Instruction / SEMITOP2,3,4 Press-Fit / Page 9/14

10 4. Module specifications The mounting surface of SEMITOP modules must be free from grease and particles. Fingerprints on the bottom side do not affect the thermal behaviour. Due to manufacturing process, the bottom side of SEMITOP may exhibit scratches, holes or similar marks. Discoloration of bottom side do not affect the thermal behaviour. The following pictures define surface characteristics, which do not affect the thermal behaviour: Figure 9: Scratch specification for SEMITOP modules Figure 10: Discoloration of SEMITOP on bottom side No influences in the thermal behavior 5. Assembly Before setting up the electrical connection (including any electrical incoming test), the module must first be mounted onto the heat sink as described as follows. 5.1 Thermal grease application To avoid air gaps at the interface between the module and the heat sink a thermal grease must be applied. The grease should follow the shape of the two surfaces (module and heatsink), allowing a metal-to-metal contact where it is possible, and filling the remaining gaps. This metal-to-metal contact can be ensured by using a standard thermal grease or by pre-applied thermal paste. by SEMIKRON / Mounting Instruction / SEMITOP2,3,4 Press-Fit / Page 10/14

11 5.2 Standard thermal grease specification Recommended thermal grease material is Wacker-Chemie P12. SEMIKRON recommends an hard rubber roller or a screen print for an even distribution of the grease. Following table shows the recommended average thickness of the applied grease layer. Table 5: Recommended thermal grease thickness for SEMITOP modules Module types SEMITOP 2,3,4 Press-Fit General Specification Maximum allowed thickness Minimum allowed thickness 40µm ± 25% 50µm 30µm If there is a margin in the thermal dissipation in the specific application, and under customer approval, this thickness can be further moderated. Further evaluations have shown that even layers with thicknesses in the range of 50µm - 80µm do not cause any functional problem if an even distribution of the layer is respected. SEMIKRON has qualified the SEMITOP power modules under the above mentioned conditions. It is customer s responsibility to qualify his own paste printing process as deviations from the recommended process may impact reliability or technical performance of the modules. The thickness of the applied grease can be checked by a measuring gauge (e.g. Fa, ELCOMETER Instrument Gmbh, Ulmer Straße 68, Aalen, , Sechseck-Kamm µm) like the one shown in the picture: Figure 11: Example of gauge to measure the thermal grease thickness 5.3 Assembling SEMITOP Press-fit+PCB onto heatsink In a first process step the module will be press in to the PCB. In a second step the mounting surface of the heatsink should be cleaned. The thermal interface material than should be applied and the PCB with module mounted onto the heatsink. Figure 12: Assembling module+pcb to the heatsink Mounting screw Heatsink Module+PCB Thermal grease by SEMIKRON / Mounting Instruction / SEMITOP2,3,4 Press-Fit / Page 11/14

12 It is recommended to tighten the screws with the corresponding mounting torque: Table 6: Mounting specifications for SEMITOP Press-Fit Module Screw Saw tooth washer (optional) Flat washer Mounting torque SEMITOP 2 Press-Fit DIN 912-M-4x16 DIN 6798 Form A DIN 125 2,0 Nm +0/-10% SEMITOP 3 Press-Fit DIN 912-M-4x16 DIN 6798 Form A DIN 125 2,5 Nm +0/-10% SEMITOP 4 Press-Fit DIN 912-M-4x16 DIN 6798 Form A DIN ,6 Nm +/-5% SEMIKRON recommends: a torque wrench with automatic control. Electric power screwdriver is recommended over a pneumatic tool. The specified screw parameters are better adjustable and especially the final torque will be reached more smoothly. A limitation to the mounting torque screw velocity is recommended to allow the thermal paste to flow and distribute equally. If tightened with higher velocity the ceramic may develop cracks due to the inability of the paste to flow as fast as necessary and therefore causing an uneven surface. The maximum screw velocity should not exceed 250rpm if recommended Wacker P12 paste is used. A soft level out (no torque overshoot) will reduce the stress even further and is preferable the above recommended screws and washers tighten the screws only once. After the mounting do not re-tighten the screws to the nominal mounting torque value. Due to relaxation of the housing and flow of thermal paste, the loosening torque is lower than the mounting torque. However, the construction of the housing, the washers and the adhesion of the thermal paste still ensure sufficient thermal coupling of the module to the heat sink Do not exceed the mounting torque because a further increase of the maximum mounting torque will not improve the thermal contact but could damage the module 6. ESD Protection SEMITOP Press-Fit IGBT and MOSFET modules are sensitive to electrostatic discharge, because discharge of this kind can damage or destroy the sensitive MOS structure of the gate. All SEMITOP Press-Fit modules are ESD protected during transport, storage and mounting process with an ESD cover. When handling and assembling the modules it is recommended that a conductive grounded wristlet is worn and a conductive grounded workplace is used. All staff should be trained suitably for correct ESD handling. by SEMIKRON / Mounting Instruction / SEMITOP2,3,4 Press-Fit / Page 12/14

13 7. Caption of figures Figure 1: Minimum distance between components and hole center of PTH... 4 Figure 2: Schematic view of the press-in setup... 5 Figure 3: Press-in depth in PCB... 6 Figure 4: Typical press-in diagram for a 26 pins module... 7 Figure 5: Schematic view of the press-out setup... 7 Figure 6: Press-out process... 8 Figure 7: Typical press-out diagram for a module with 26 pins... 8 Figure 8: Heat sink surface specifications... 9 Figure 9: Scratch specification for SEMITOP modules Figure 10: Discoloration of SEMITOP on bottom side Figure 11: Example of gauge to measure the thermal grease thickness Figure 12: Assembling module+pcb to the heatsink Caption of tables Table 1: Specification of PTH for the press-in process... 3 Table 2: Specification of PTH for soldering of Press-Fit pins to the PCB... 3 Table 3: Specification of PCB hole diameter for the mounting post... 4 Table 4: Specification of press-type... 5 Table 5: Recommended thermal grease thickness for SEMITOP modules Table 6: Mounting specifications for SEMITOP Press-Fit References [1] [2] SEMITOP Technical Explanations by SEMIKRON / Mounting Instruction / SEMITOP2,3,4 Press-Fit / Page 13/14

14 10. Disclaimer The data given in this document shall be for information purposes only. It may not reflect the product in its latest status. For a valid product specification please refer to the relevant product data sheet in its actual version. SEMIKRON reserves the right to make changes without further notice herein to improve reliability, function or design. Information furnished in this document is believed to be accurate and reliable. However, no representation or warranty is given and no liability is assumed with respect to the accuracy or use of such information, including without limitation, warranties of non-infringement of intellectual property rights of any third party. SEMIKRON does not assume any liability arising out of the application or use of any product or circuit described herein. Furthermore, this technical information may not be considered as an assurance of component characteristics. No warranty or guarantee expressed or implied is made regarding delivery, performance or suitability. This document supersedes and replaces all information previously supplied and may be superseded by updates without further notice. SEMIKRON products are not authorized for use in life support appliances and systems without the express written approval by SEMIKRON. SEMIKRON INTERNATIONAL GmbH P.O. Box Nuremberg Germany Tel: Fax: sales.skd@semikron.com by SEMIKRON / Mounting Instruction / SEMITOP2,3,4 Press-Fit / Page 14/14