MiniSKiiP copyright Vincotech Handling Instructions for MiniSKiiP These handling instructions apply to all types of MiniSKiiP modules. Handling Instruction 04 03 Ver Thermal paste thickness, pattern modified housing; doc. update Alteration 09.26.2014. Tokes A. 09.12.2011. Nabilek J. Date Des. / Mod. Ori A. Őri A. Appr. V23990-K-M118-*-31 Page 1 / 10 MiniSKiiP copyright Vincotech Table of contents: 1. PCB specifications for the MiniSKiiP contact system................................................................................................. 3 2. Assembly ............................................................................................................................................................................ 3 2.1 Preparations and surface specifications........................................................................................................................ 3 2.1.1 Heat sink .......................................................................................................................................................... 3 2.1.2 Mounting surface ............................................................................................................................................. 5 2.2 Spring contact specifications ....................................................................................................................................... 7 2.2.1 Spring contact quality ...................................................................................................................................... 7 2.3 Assembly ..................................................................................................................................................................... 8 2.2.1 Applying the thermal paste .............................................................................................................................. 8 2.2.2 Pre-applied thermal paste ................................................................................................................................ 8 2.2.3 Mounting ....................................................................................................................................................... 10 2.2.4 Mounting screw specifications ...................................................................................................................... 11 3 Storage and Shelf Life Conditions .................................................................................................................................. 12 4 ESD protection ................................................................................................................................................................. 12 5 Disclaimer ......................................................................................................................................................................... 12 Table of figures: Fig. 2.1 Heat sink surface specifications _______________________________________________________________ 3 Fig. 2.2 DCB with fingerprints and discolorations _______________________________________________________ 5 Fig. 2.3 DBC's bottom surface after rework _____________________________________________________________ 5 Fig. 2.4 Scratches on the MiniSKiiP's bottom surface ____________________________________________________ 6 Fig. 2.5 Etching hole (reaching down to the substrate) in a MiniSKiiP 's bottom surface _________________________ 6 Fig. 2.6 Etching hole (shallower than the substrate) in a MiniSKiiP 's bottom surface ___________________________ 6 Fig 2.7 Variance in the DBC's position ________________________________________________________________ 6 Fig 2.8: Spring overlay _____________________________________________________________________________ 7 Fig 2.9: Examples of discolored spring surfaces _________________________________________________________ 7 Fig. 2.11 Fig. 2.12 Fig. 2.13 ___________________________________________________________________ 10 Fig. 2.14 Fig. 2.15 Fig. 2.16 ___________________________________________________________________ 10 Fig.2.17: Skin on thermal paste _____________________________________________________________________ 10 Handling Instruction 04 03 Ver Thermal paste thickness, pattern modified housing; doc. update Alteration 09.26.2014. Tokes A. 09.12.2011. Nabilek J. Date Des. / Mod. Ori A. Őri A. Appr. V23990-K-M118-*-31 Page 2 / 10 MiniSKiiP copyright Vincotech 1. PCB specifications for the MiniSKiiP contact system The combination of surface materials where the MiniSKiiP spring and the PCB landing pad meet affects the contact resistance for various currents. This is why the PCB has to be made with sufficiently thick plating. PCB surface coatings must also comply with RoHS regulations. The following finishes are recommended: Gold flash over nickel (NiAu) Hot air-leveled tin (HAL Sn) Chemical tin (Chem.l Sn) Boards with OSP (organic solderability preservative) passivation are not recommended. OSP is unsuitable as there is no guarantee that the contact will remain free of corrosion over time. OSP passivation practically vanishes during soldering or after around six months in storage. The data set needed to properly design PCBs are to be found at the Vincotech website. These package data documents contain drawings showing PCB size specifications, pin positions and lid specifications for all MiniSKiiP® housings. 2. Assembly 2.1 Preparations and surface specifications The heat sink and module must meet the following requirements to achieve maximum thermal conductivity. 2.1.1 Heat sink Fig. 2.1 Heat sink surface specifications The heat sink must be free of grease and particles. The heat sink's mounting surface irregularity has to be ≤ 50 μm per 100 mm (DIN EN ISO 1101). RZ ≤ 6.3 μm (DIN EN ISO 4287) Handling Instruction 04 03 Ver Thermal paste thickness, pattern modified housing; doc. update Alteration 09.26.2014. Tokes A. 09.12.2011. Nabilek J. Date Des. / Mod. Ori A. Őri A. Appr. V23990-K-M118-*-31 Page 3 / 10 MiniSKiiP copyright Vincotech No steps > 10 μm (DIN EN ISO 4287) Handling Instruction 04 03 Ver Thermal paste thickness, pattern modified housing; doc. update Alteration 09.26.2014. Tokes A. 09.12.2011. Nabilek J. Date Des. / Mod. Ori A. Őri A. Appr. V23990-K-M118-*-31 Page 4 / 10 MiniSKiiP copyright Vincotech 2.1.2 Mounting surface The MiniSKiiP module's mounting surface also has to be free of grease and any foreign particles. MiniSKiiP modules are made using DBC without finishing or with a gold-flash finish (NiAu). Fingerprints or discolorations (Fig. 2.2) on the bottom of the DBC have no impact on thermal behavior and are therefore not failure criteria. Rework or a second cleaning operation could leave imperfections in the gold-flash finish on the bottom of the DBC. Such an imperfection in the gold-flash finish does not affect thermal behavior (Fig 2.3). The gold-flash finish is necessary only on the DBC's top side to serve as the spring landing pad. It is far more costly to plate a single side, so the bottom is only coated as a by-product of the plating process. The bottom of the MiniSKiiP module may exhibit scratches, holes or similar marks incurred during manufacturing. The pictures below show surface marks that do not affect thermal behavior. Failures can occur in the event of deformations exceeding the tolerances specified below. Fig. 2.2 DCB with fingerprints and discolorations Fig. 2.3 DBC's bottom surface after rework MiniSKiiP modules must always comply with the specifications indicated for Fig 2.4 to Fig. 2.6. Handling Instruction 04 03 Ver Thermal paste thickness, pattern modified housing; doc. update Alteration 09.26.2014. Tokes A. 09.12.2011. Nabilek J. Date Des. / Mod. Ori A. Őri A. Appr. V23990-K-M118-*-31 Page 5 / 10 MiniSKiiP copyright Vincotech Fig. 2.4 Scratches on the MiniSKiiP's bottom surface Fig. 2.5 Etching hole (reaching down to the substrate) in a MiniSKiiP's bottom surface Fig. 2.6 Etching hole (shallower than the substrate) in a MiniSKiiP's bottom surface Etched dimples on the edge of the DBC reduce stress between the copper layer and the ceramic substrate. Dimples are usually around 0.6 mm in diameter and around 0.3 mm in depth. They are never located below an IGBT or Diode chip and therefore do not affect thermal behavior. There may some manufacturing-related variance in the substrate's position within the plastic housing. The gap between the housing and substrate may be no greater than 0.55 mm (Fig 2.7). Fig 2.7 Variance in the DBC's position Handling Instruction 04 03 Ver Thermal paste thickness, pattern modified housing; doc. update Alteration 09.26.2014. Tokes A. 09.12.2011. Nabilek J. Date Des. / Mod. Ori A. Őri A. Appr. V23990-K-M118-*-31 Page 6 / 10 MiniSKiiP copyright Vincotech 2.2 Spring contact specifications The spring must protrude from the housing no less than 1.1 mm (Fig. 2.8), measured from the top surface to the head of the spring, to ensure a proper contact after mounting. Typically, it protrudes 1.35 mm. The spring's base material is a high-performance copper alloy. The spring is not expected to fatigue over the MiniSKiiP's lifetime. To function properly, spring contacts may not be contaminated by oil, sweat or other substances. The spring surface is never to be touched with bare fingers! It is advisable to wear gloves when handling MiniSKiiP modules. Do not apply contact spray or other chemicals to the springs! Min.: 1.1mm Fig 2.8: Spring overlay 2.2.1 Spring contact quality The silver surface of spring pins in MiniSKiiP® modules is covered with a silver passivation film to protect it from deterioration. It is merely cosmetic, protecting the silver surface from sulfuration and tarnishing for around half a year. The silver springs may begin to decolorize after that depending on the tarnish protection's thickness. Different springs on the same module may exhibit different levels of discoloration as shown in the examples in Fig. 2.9. Fig 2.9: Examples of discolored spring surfaces Handling Instruction 04 03 Ver Thermal paste thickness, pattern modified housing; doc. update Alteration 09.26.2014. Tokes A. 09.12.2011. Nabilek J. Date Des. / Mod. Ori A. Őri A. Appr. V23990-K-M118-*-31 Page 7 / 10 MiniSKiiP copyright Vincotech The yellow marks shown above are caused by thin sulphide layers that are easily pierced during mounting and do not impair the electrical contact. 2.3 Assembly 2.2.1 Applying the thermal paste Apply a thin layer of thermal paste to the heat sink or the module's bottom surface. VINCOTECH recommends for it to be screen-printed because this method of application is reproducible and achieves a uniform layer. Paste may also be applied using a hard rubber roller, but this has to be done with painstaking care to achieve acceptable results. The thickness of the thermal paste layer should be measured and confirmed. The following thicknesses are recommended for Silicone Paste P 12 made by WACKER CHEMIE: MiniSKiiP 0: MiniSKiiP 1: MiniSKiiP 2: MiniSKiiP 3: min. 16 μm 21 μm 38 μm 27 μm max. -- 28 μm -- 38 μm -- 60 μm -- 43 μm These specifications apply to a continuous film of thermal paste. If the application tool leaves a pattern as is the case with printing, the thickness has to be adjusted so that the resultant continuous layer of thermal paste is within values specified above. 2.2.2 Pre-applied thermal paste VINCOTECH offers the MiniSKiiP module with pre-applied thermal paste to facilitate assembly. Thermal paste is applied before the modules ship, thereby eliminating this critical step from the customer’s manufacturing process and making assembly more efficient, reproducible and controllable. An automated and monitored screen printer applies thermal paste to the module in a layer with precisely the right thickness. If you wish to order MiniSKiiP products with pre-applied thermal paste, please use the following code: -/1A/-/1B/1 indicates the applied thermal paste. A indicates a standard 6.5 mm thick lid. B indicates a thin 2.8 mm thick lid. Example order: V23990-K420-A60-/1A/-PM The product will be delivered with thermal paste and a 6.5 mm thick lid. Handling Instruction 04 03 Ver Thermal paste thickness, pattern modified housing; doc. update Alteration 09.26.2014. Tokes A. 09.12.2011. Nabilek J. Date Des. / Mod. Ori A. Őri A. Appr. V23990-K-M118-*-31 Page 8 / 10 MiniSKiiP copyright Vincotech The following slight deviations may occur because of the automated screen-printing process. They have no affect on the mounting process or thermal properties. Handling Instruction 04 03 Ver Thermal paste thickness, pattern modified housing; doc. update Alteration 09.26.2014. Tokes A. 09.12.2011. Nabilek J. Date Des. / Mod. Ori A. Őri A. Appr. V23990-K-M118-*-31 Page 9 / 10 MiniSKiiP copyright Vincotech Slight variations in print positioning Slight variances in the thermal paste's pattern (Fig. 2.11-2.15) Slight subsurface migration (Fig. 2.16) The honeycomb pattern may vary by no more than 5% in size. Fig. 2.11 Fig. 2.12 Fig. 2.13 Fig. 2.14 Fig. 2.15 Fig. 2.16 If the modules are stored or transported (see also section 3, Storage and Shelf Life Conditions) at temperatures <60°C and at high humidity >85%, a thin skin may form on the surface of the thermal paste layer (Fig. 2.17). This has no affect on the module's thermal properties or the thermal grease's function. Fig.2.17: Skin on thermal paste NOTE: Always observe the thermal paste manufacturer’s specifications as set down in the safety data sheet. The latest versions are posted on the following website: Wacker P12: <http://www.drawin.de/dasat/index.php?cid=100153&conid=0&sid=dasat> 2.2.3 Mounting Handling Instruction 04 03 Ver Thermal paste thickness, pattern modified housing; doc. update Alteration 09.26.2014. Tokes A. 09.12.2011. Nabilek J. Date Des. / Mod. Ori A. Őri A. Appr. V23990-K-M118-*-31 Page 10 / 10 MiniSKiiP copyright Vincotech Place the MiniSKiiP on the heat sink's target area and tighten the screw with a nominal torque of 2.0 Nm < M < 2.5 Nm. For MiniSKiiP 3 modules with two screws, first fasten both screws with a torque no higher than 1 Nm and then tighten them with the nominal torque of 2.0 Nm < M < 2.5 Nm. An electrical power screwdriver is preferable to a pneumatic tool. Torque and RPM may be controlled far more accurately with electrically powered tools and they reach the target torque much more smoothly. The action of a pneumatic tool's clutch can produce a mechanical shock and overshoot the target torque, both of which could damage the module. Fasten mounting screws at a speed slow enough to allow thermal paste to flow and be distributed uniformly, especially when using denser pastes. If screws are tightened at faster speeds, the ceramic may crack because the paste is unable to flow as fast as necessary, leaving an irregular surface. The specifications given below apply to Wacker P12 thermal paste and electrical power screwdrivers. Limit the rotational speed to no greater than 250 rpm when fastening screws. It is also advisable to gently decelerate, thereby preventing torque overshoot and reducing the stress on components. Loosening torque is lower because of the housing and thermal paste's elasticity. 0.6 Nm is sufficient to achieve a proper thermal contact. The housing's design, the elastic give of the metal plate in the pressure lid, and the thermal paste's adhesive properties ensure an electrical contact is made and sufficient thermal coupling is achieved between the module and heat sink. Caution: Do not retighten screws to the nominal mounting torque! This will place undue stress on the DBC, housing and springs. The pressure lid and PCB may be removed from the MiniSKiiP module for rework or testing and then remounted or replaced. If a module is incorrectly aligned with the heat sink, it may be removed and then placed in the proper position, but only if it has not already been fastened to the heat sink with a screw. The thermal paste is quite adhesive, so this will require some painstaking effort. Subsequently, all thermal paste has to be carefully removed from the module and heat sink. Alcohol may be used to clean the surfaces. The pressure will drop somewhat over time in an assembled MiniSKiiP because of the give of its components. Although a MiniSKiiP may be re-assembled, the pressure could be distributed differently than in a new module and its thermal resistance may differ from the values given in the data sheet. 2.2.4 Mounting screw specifications Recommended mounting screw: M4 according to DIN 7991 - 8.8 or a similar screw with a TORX head Screw class: 8.8 Tensile strength: Rm= 800 N / mm² Yield point: Re= 640 N / mm² Handling Instruction 04 03 Ver Thermal paste thickness, pattern modified housing; doc. update Alteration 09.26.2014. Tokes A. 09.12.2011. Nabilek J. Date Des. / Mod. Ori A. Őri A. Appr. V23990-K-M118-*-31 Page 11 / 10 MiniSKiiP copyright Vincotech The minimum depth of the screw in the heat sink is 6.0 mm. 3 Storage and Shelf Life Conditions MiniSKiiP power modules are qualified to IEC 60721-4-1 and may be stored in the original package for two years under climatic class 1K2 (IEC 60721-3-1): Relative humidity: Storage temperature: 5%...85% 5°C…40°C Although the following shelf life conditions have not been tested, they are advisable and experience has shown that they should not be exceeded or disregarded: Relative humidity: Storage temperature: Condensation: Storage time: 85% max. -25°C…+60°C none 2 years max. The reverse current limits may be exceeded after extreme humidity, but this does not adversely affect the performance of the MiniSKiiP. 4 ESD protection Electrostatic discharges can damage or destroy sensitive semiconductors in modules. Semiconductive plastic trays in the shipment box protect all modules against ESD. It is advisable to wear a conductive grounded wristlet and work at a conductive grounded station when handling and assembling modules. 5 Disclaimer The information given in this document should not be used in substitution for the customer’s tests because the conditions and circumstances of the application are beyond Vincotech's control. The content of this document is true and accurate to the best of our knowledge, reflects current standards, and has been compiled with due care. MiniSKiiP® is a trademark of SEMIKRON Elektronik GmbH & Co. KG Handling Instruction 04 03 Ver Thermal paste thickness, pattern modified housing; doc. update Alteration 09.26.2014. Tokes A. 09.12.2011. Nabilek J. Date Des. / Mod. Ori A. Őri A. Appr. V23990-K-M118-*-31 Page 12 / 10