MOUNTING AND SOLDERING INSTRUCTIONS Page SOLDERING GUIDELINES AND SMD FOOTPRINT DESIGN FOR AXIAL AND RADIAL LEADED PACKAGES AND MEDIUMPOWER SURFACE MOUNT PACKAGES This information is contained in Philips publication SC18 Discrete Semiconductor Packages, (1997), section: 4. PACKING METHODS AND PACKING QUANTITIES This information is contained in Philips publication SC18 Discrete Semiconductor Packages, (1997), section: 6. GENERAL DATA AND INSTRUCTIONS FOR SOD59, SOD100, SOD113, TO 220AB (SOT78), SOT186; SOT186A General rules Mounting methods Heatsink requirements Heatsink compound Thermal data for heatsink mounting methods (SOD59 and SOT78) Soldering Lead bending Additional guide-lines INSTRUCTIONS FOR CLIP MOUNTING Direct mounting with clip Insulated mounting with clip INSTRUCTIONS FOR SCREW MOUNTING Direct mounting with screw and spacing washer Insulated mounting with screw and spacing washer GENERAL DATA AND INSTRUCTIONS FOR SOT223, SOT428, SOT404 Scope SOT223 Thermal management Thermal data for various PCB arrangements SOT428 Thermal management Thermal data for various PCB arrangements 1998 Dec 10 1 MOUNTING AND SOLDERING INSTRUCTIONS Page SOT404 Thermal management Thermal data for various PCB arrangements References Philips Semiconductors also maintains product information on the World-Wide-Web. Our home page can be located at: http://www.semiconductors.philips.com 1998 Dec 10 2 Philips Semiconductors Power Diodes Mounting and Soldering Instructions This method is not permitted for full-pack envelopes because it will damage the plastic encapsulation. GENERAL DATA AND INSTRUCTIONS FOR SOD59, SOD100, SOD113, TO220AB (SOT78), SOT186, SOT186 Heatsink requirements General rules Flatness in the mounting area: 0.02 mm maximum per 10 mm. Mounting holes must be deburred, for further information see clip and screw mounting instructions. 1. Fasten the device to the heatsink before soldering the leads. 2. Avoid stress to the leads. Heatsink compound 3. Keep mounting tool (e.g. screwdriver) clear of the plastic body. The thermal resistance from mounting base to heatsink (Rth mb-h) can be reduced by applying a metallic oxide compound between the contact surfaces. Values given in the following table are of thermal resistance using this type of compound. Dow Corning 340 Heat sink compound is recommended. For insulated mounting, the compound should be applied to the bottom of both device and insulator. 4. The rectangular washer may only touch the plastic part of the body; it should not exert any force on that part (screw mounting). Mounting methods CLIP MOUNTING Mounting by means of spring clip offers: 1. A good thermal contact under the crystal area, and slightly lower thermal resistance than screw mounting. 2. Safe insulation for mains operation. Minimum force for good heat transfer is 10 N. Maximum force to avoid damaging the device is 80 N. M3 SCREW MOUNTING It is recommended that the rectangular spacing washer is inserted between screw head and mounting tab. Do not use self-tapping screws. Mounting torque for screw mounting: For thread-forming screws these are final values. Minimum torque for good heat transfer is 0.55 Nm. Maximum torque to avoid damaging the device is 0.80 Nm. When a nut or screw is driven directly against the tab, the torques are as follows: Minimum torque for good heat transfer is 0.40 Nm. Maximum torque to avoid damaging the device is 0.60 Nm. RIVET MOUNTING NON-INSULATED The device should not be pop-riveted to the heatsink. It is permissible to press-rivet the metal tab providing that eyelet rivets of soft material are used, and the press forces are slowly and carefully controlled. 1998 Dec 10 3 Philips Semiconductors Power Diodes Mounting and Soldering Instructions Thermal data for heatsink mounting methods (SOD59 and SOT78) Typical figures, for exact figures see data for each device type. Additional insulators are generally not required when mounting the full-pack (SOD100, SOD113, SOT186, and SOT186A) outlines. Rth mb-h Thermal resistance from mounting base to heatsink Mounting method K/W Clip Screw direct with heatsink compound 0.3 0.5 direct without heatsink compound 1.4 1.4 with heatsink compound and 0.1 mm maximum mica insulator 2.2 - with heatsink compound and 0.25 mm maximum alumina insulator 0.8 - insulated up to 500 V - 1.4 insulated up to 800 V/1000 V - 1.6 insulated up to 500 V - 3.0 insulated up to 800 V/1000 V - 4.5 with heatsink compound and 0.05 mm mica insulator without heatsink compound and 0.05 mm mica insulator This is also to prevent damage to the seal of the leads within the plastic body. Soldering Recommendation for devices with a maximum junction temperature rating 175 C: Leads can be bent as near to the body as required, but adequate length should always be allowed for clamping. This is a minimum of 1.75 mm from the body to the start of a bend radius. DIP OR WAVE SOLDERING Maximum permissible solder temperature is 260 C at a distance from the body of >5 mm and for a total contact time with soldering bath or waves of <7 s. The internal radius of bend should never be less than the thickness of the lead. A minimum radius of at least 1.5 x lead thickness is preferred. See Fig.1. Surface cracks in the dip tin coating on the lead are common when a radius less than 1.5 x lead thickness is used. Although exposing the copper material, these cracks do not affect the mechanical strength of the lead. Lead forming by Philips is available as an option on all products supplied in these outlines. HAND SOLDERING Maximum permissible temperature is 275 C at a distance from the body of >3 mm and for a total contact time with the soldering iron of <5 s. The body of the device must not touch anything with a temperature >200 C. It is not permitted to solder the metal tab of the device to a heatsink, otherwise the junction temperature rating will be exceeded. clamp area 1.75 min Avoid any force on body and leads during or after soldering; do not correct the position of the device or of its leads after soldering. plastic body RL Lead bending L Maximum permissible tensile force on the body for 5 seconds is 20 N. MGA772 Dimensions in mm. The leads can be bent, twisted or straightened. To keep forces within the above mentioned limits the leads should always be clamped rigidly near the body during bending. 1998 Dec 10 Fig.1 Minimum lead bend radius. 4 Philips Semiconductors Power Diodes Mounting and Soldering Instructions Additional guide-lines It is recommended that where a device is rigidly secured to a heatsink which is in turn rigidly secured to a PCB, that a bend is put in the leads to act as an expansion loop. This will prevent differential expansion of the mounting parts transferring stress to the soldering joint, as shown in Fig.2. This is only necessary where the device is mounted so rigidly that expansion forces are transmitted through the assembly. secure not rigid rigid rigid solder joint rigid PCB secure not rigid solder joint rigid PCB solder joint PCB MGA768 (a) Incorrect (b) Correct Fig.2 Printed circuit board and heatsink mounting. 1998 Dec 10 5 (c) Correct Philips Semiconductors Power Diodes Mounting and Soldering Instructions INSTRUCTIONS FOR CLIP MOUNTING Direct mounting with clip 1. Apply heatsink compound to the mounting base, then place the device on the heatsink. 2. Push the short end of the clip into the narrow slot in the heatsink with the clip at an angle of 10 to 30 to the vertical. See Figs.3 and 4. 3. Push down the clip over the device until the long end of the clip snaps into the wide slot in the heatsink. The clip should bear on the plastic body, not on the tab. See Fig.5. spring clip 4.0 3.8 1.6 1.4 12.0 11.5 1.8 min 2.0 1.0 MGA780 MGA779 Dimensions in mm. Fig.3 Heatsink requirements. Fig.4 Mounting. MGA781 Fig.5 Position of device (top view). 1998 Dec 10 6 Philips Semiconductors Power Diodes Mounting and Soldering Instructions Insulated mounting with clip With the insulators up to 2 kV insulation is obtained. 1. Apply heatsink compound to the bottom of both device and insulator, then place the device with the insulator on the heatsink. 2. Push the short end of the clip into the narrow slot in the heatsink with the clip at an angle of 10 to 30 to the vertical. See Figs 6, 7 and 8. 3. Push down the clip over the device until the long end of the clip snaps into the wide slot in the heatsink. The clip should bear on the plastic body, not on the tab. Ensure that the device is centred on the mica insulator to prevent unwanted movement. spring clip 4.0 3.8 1.6 1.4 16.8 16.3 1.8 min 2.0 1.0 insulator MGA782 MGA783 Dimensions in mm. Fig.6 Heatsink requirements. Fig.7 Mounting. MGA784 Fig.8 Position of device (top view). 1998 Dec 10 7 Philips Semiconductors Power Diodes Mounting and Soldering Instructions INSTRUCTIONS FOR SCREW MOUNTING Direct mounting with screw and spacing washer THROUGH HEATSINK WITH NUT M3 screw rectangular washer (not required for F-pack) 3.5 max 1.5 min heatsink plain washer lock washer 3.3 3.1 MGA751 M3 nut MGA761 Dimensions in mm. Fig.10 Heatsink requirements. Fig.9 Assembly. INTO TAPPED HEATSINK 3.5 max M3 screw rectangular washer (not required for F-pack) 4 min heatsink M3 MGA752 MGA762 Dimensions in mm. Fig.11 Assembly. 1998 Dec 10 Fig.12 Heatsink requirements. 8 Philips Semiconductors Power Diodes Mounting and Soldering Instructions Insulated mounting with screw and spacing washer Not recommended where mounting tab is on mains voltage. Not applicable for F-pack. THROUGH HEATSINK WITH NUT Known as a `bottom mounting'. 180 120 4.7 0.1 0.7 0.1 M3 screw 2.0 0.1 3.6 rectangular washer + 0.2 0 MGA754 Dimension in mm. Fig.14 Heatsink requirements for 500 V insulation. mica insulator heatsink insulating bush 5.5 0.1 plain washer lock washer M3 nut 1.0 0.1 2.0 0.1 MGA759 3.6 Fig.13 Insulated screw mounting with rectangular washer. 1998 Dec 10 + 0.2 0 MGA753 Fig.15 Heatsink requirements for 800 V insulation. 9 Philips Semiconductors Power Diodes Mounting and Soldering Instructions INTO TAPPED HEATSINK Known as a `top mounting'. 180 120 4.7 0.1 2.0 0.1 M3 screw 5 min rectangular washer M3 rectangular insulating bush MGA755 Dimension in mm. Fig.17 Heatsink requirements for 500 V insulation. mica insulator heatsink 180 120 MGA760 5.5 0.1 Fig.16 Insulated screw mounting with rectangular washer into tapped heatsink. 2.0 0.1 6 min M3 MGA756 Dimension in mm. Fig.18 Heatsink requirements for 1000 V insulation. 1998 Dec 10 10 Philips Semiconductors Power Diodes Mounting and Soldering Instructions GENERAL DATA AND INSTRUCTIONS FOR SOT223; SOT428; SOT404 Thermal data for various PCB arrangements For SOT223 we always quote the junction-to-solder point thermal resistance (Rth j-sp) because it is an accurately defined parameter which is easy to measure. As its name implies, the solder point is the point on the copper pad at the edge of the device tab. We also quote junction-to-ambient thermal resistance (Rth j-a) for different PCB arrangements. Scope This chapter summarises important data and recommendations for using power semiconductors in the SOT223, SOT428 and SOT404 envelopes. Please refer to Data Handbook SC18 for a more detailed analysis of placing, soldering and reworking surface mounted components. The References section at the end of this chapter list this and other Philips publications on the subject of surface mounted power semiconductors. Because the Rth j-sp and Rth j-a values are much greater than the internal thermal resistance between the junction and copper leadframe, they tend to mask any small variations that might occur in this internal thermal resistance from one device type to another. Therefore the thermal resistances effectively remain the same for all of our power semiconductors in SOT223. These are shown in the table below. SOT223 The SOT223 envelope is optimized for low cost, high volume, surface mounted assembly. It is the easiest and most versatile power package to surface mount because it is the only one that can either be wave or reflow soldered. This is advantageous when there is a mixture of through-hole mounted and surface mounted components on the PCB, because wave soldering can safely be used to solder both component types in a single soldering process. Rth j-sp Thermal resistance from junction to solder point 15 max. Rth j-a The design of the package means that all solder joints remain exposed on its periphery after assembly. This is the reason why wave soldering can be used. It also means that the joints can be visually inspected for quality. SOT223 is supplied on 180 mm x 12 mm or 330 mm x 12 mm reels for use with high speed pick-and-place machines. The device quantities per reel are 1000 and 4000 respectively. Thermal resistance from junction to ambient 156 typ. FR4 glass-epoxy board, 1.6 mm thick, pad area as in Fig.20 70 typ. 3.8 Thermal management 1.5 min Most of the heat generated in the die is conducted along the main central tab at the top of the package. A little will also be conducted along the centre leg which is electrically connected to the main tab. A very small proportion of the heat will be conducted down the two outer legs. The main PCB pad must conduct the heat away from the device; the larger the pad area, the higher the permitted power dissipation. 2.3 1.5 min 6.3 (3x) 1.5 min As the assembly heats and cools during operation, there will be relative movement between the PCB and device due to differing coefficients of expansion between the printed circuit board and the device, as is common when using low cost glass/epoxy or paper/epoxy substrates. The SOT223 leadform accommodates the thermal expansion stresses, thus minimising the risk of fatigue fracture of the solder joints and stress fracture of the die. 4.6 Dimensions in mm. Fig.19 SOT223 minimum footprint. 11 K/W FR4 glass-epoxy board, 1.6 mm thick, minimum footprint as in Fig.19 min 1998 Dec 10 K/W Philips Semiconductors Power Diodes Mounting and Soldering Instructions Thermal management The SOT428 envelope is designed to minimise the thermal resistance between the die and the printed circuit board, enabling more power to be dissipated. Heat generated in the die is extracted across the copper header to the PCB pad underneath the device. Because of the low thermal resistance between the junction and the main PCB pad, relatively little heat will be extracted down the two leads to the small PCB pads. 36 18 60 4.5 4.6 9 In order to achieve optimum power dissipation from such a small power package, the SOT428 needs to be used in conjunction with a circuit board material and a heatsink capable of conducting heat away efficiently from the mounting base of the device. 10 7 Thermal data for various PCB arrangements 15 For SOT428 we quote the junction-to-mounting base thermal resistance (Rth j-mb). This is inherently a low figure which will vary according to which die is housed within the package. Rth j-mb data is therefore quoted separately for each SOT428 device. We also quote junction-to-ambient thermal resistance (Rth j-a) for PCB mounting. This is shown in the table below. 50 Dimensions in mm. PCB: FR4 epoxy glass 1.6 mm thick; copper laminate 35 m thick. Fig.20 PCB for thermal resistance and power rating for SOT223. SOT428 Rth j-a SOT428 is Philips' version of DPAK. This outline occupies an area on the PCB which is similar to that occupied by SOT223; it can be soldered to a common SOT223/SOT428 pad layout. However, unlike SOT223, SOT428 has a metal base which is soldered directly to the PCB. This forms the "centre leg connection", since there is no centre leg to connect to the PCB. FR4 glass-epoxy board, 1.6 mm thick, minimum footprint as in Fig.21 7.0 The amount of solder paste on the mounting base land must be carefully controlled because an excess will cause the device top edge to rise up and float on a meniscus of solder. Conversely, too little solder will result in an imperfect joint with voids. Both faults will increase the thermal resistance. Furthermore, a defect, especially too little solder, might not be visible after soldering since it will be hidden underneath the device. 2.15 1.5 2.5 4.57 SOT428 is supplied on 330 mm x 24 mm reels for use with high speed pick-and-place machines. The device quantity per reel is 2500. Dimensions in mm. Fig.21 SOT428 minimum footprint. 12 K/W 75 typ. 7.0 The design of the package means that the solder joint remains hidden underneath the device after assembly. A reflow soldering process must be used. Wave soldering is unsuitable because it is not guaranteed to heat the joint sufficiently to achieve full wetting of the joint. 1998 Dec 10 Thermal resistance from junction to ambient Philips Semiconductors Power Diodes Mounting and Soldering Instructions board substrate materials. The figures are representative of a single-sided PCB measuring 60 mm x 40 mm, with the surface mounted power components and copper traces on the top side. The board is fastened to a heatsink with machine screws and a layer of heatsink compound, or a thermally conducting pad is placed between the printed circuit board and the heatsink to improve thermal contact. SOT404 D2PAK. SOT404 is Philips' version of It is the same size and shape as a SOT78 (TO220) package, but it has no tab and its three leads are formed for surface mounting. Despite its similarity to SOT78, it is manufactured differently. A different leadframe without a tab is used. Also, unlike SOT78, all exposed metal surfaces are lead tin plated for good solderability. The figures are typical only. The thermal resistance of individual designs will depend upon the overall size of the printed circuit board, the packing density of the power devices, and the width of the copper traces. The total junction-to-heatsink thermal resistance is obtained by adding the relevant Rth mb-h figure to the Rth j-mb value from the data sheet. The design of the package means that the solder joint remains hidden underneath the device after assembly. A reflow soldering process must be used. Wave soldering is unsuitable because it is not guaranteed to heat the joint sufficiently to achieve full wetting of the joint. The amount of solder paste on the mounting base land must be carefully controlled because an excess will cause the device top edge to rise up and float on a meniscus of solder. Conversely, too little solder will result in an imperfect joint with voids. Both faults will increase the thermal resistance. Furthermore, a defect, especially too little solder, might not be visible after soldering since it will be hidden underneath the device. Rth j-a FR4 glass-epoxy board, 1.6 mm thick, minimum footprint as in Fig.22 Rth mb-h SOT404 is supplied on 330 mm x 24 mm reels for use with high speed pick-and-place machines. The device quantity per reel is 800. Thermal Management Inside the SOT404 envelope, the die is bonded to a large copper header which conducts the heat from the chip directly to the main pad on the printed circuit board. SOT404 has the same thermal resistance as SOT78 and hence can handle the same power. However, in order to dissipate the same power as a well heatsunk SOT78 package, the printed circuit substrate material and the copper traces must conduct heat away efficiently from the mounting base to a heatsink. Thermal data for various PCB arrangements Thermal resistance from mounting base to heatsink K/W 55 typ. K/W FR4 glass-epoxy board, 1.6 mm thick; land size as in Fig.22 50 typ. FR4 glass-epoxy board, 1.6 mm thick, 2.5 cm square mounting land 40 typ. FR4 glass-epoxy board, 1.6 mm thick, land size as in Fig.22, with pattern of 18 x 0.5 mm dia plated through holes filled with solder 8 typ. FR4 glass-epoxy board, 0.8 mm thick, land size as in Fig.22, with pattern of 18 x 0.5 mm dia plated through holes filled with solder 4 typ. Alumina substrate, 0.8 mm thick, land size as in Fig.22 2 typ. Aluminium clad substrate, 1.6 mm thick, land size as in Fig.22 1 typ. Figure 22 shows the recommended land design for SOT404. When used in conjunction with a heatsink, increasing the dimensions of the mounting land will improve the thermal conduction between the mounting base and the heatsink. For SOT404 we quote the junction-to-mounting base thermal resistance (Rth j-mb). This is inherently a low figure due to the envelope design. It will vary according to which die is housed inside, so it is quoted separately for each SOT404 device. We also quote junction-to-ambient thermal resistance (Rth j-a) for PCB mounting. This is shown in the following table. Also shown in the table is mounting base-to-heatsink thermal resistance (Rth mb-h) for different printed circuit 1998 Dec 10 Thermal resistance from junction to ambient 13 Philips Semiconductors Power Diodes Mounting and Soldering Instructions References 11.5 1. Data Handbook SC18 - Discrete Semiconductor Packages. Issued 1997. Order code: 9397 750 02418. 2. Product Application Information - Surface Mounted Triacs and Thyristors. 9.0 Issued 1997. Order code: 9397 750 02622. 17.5 2.0 3.8 5.08 Dimensions in mm. Fig.22 SOT404 minimum footprint. 1998 Dec 10 14