Application note 8-resistor bussed network As more and more computer motherboards adopt highspeed CPUs to increase their data processing power and functionality, board space becomes ever more critical for layout design. This is particularly true for motherboards based on the latest Pentium series of high-speed processors, which require pull-up and pull-down networks to provide signal matching. To meet this requirement, Phycomp has recently introduced a new 8 resistor bussed network in a 10-pin 1206 case with two ground connections. As Fig.1 shows, the new resistor network takes up significantly less board space than a network based on discrete resistors. It is even small enough to be placed beneath the processor IC itself, allowing for further savings in board space and improvements in reliability since interconnections are then much shorter. PHYCOMP 102 8R network 33R 33R 33R 33R 33R 33R 33R 33R SUMMARY Phycomp’s new 8-resistor bussed network offers important advantages to designers of computer motherboards, especially boards using the latest Pentium processors which require pull-up and pulldown networks to provide signal matching. In a 10-pin 1206 case with two ground con-nections, the resistor network takes up significantly less board space than a network based on discrete resistors. It is even small enough to be placed beneath the processor IC itself, allowing for further savings in board space and improvements in reliability. PHYCOMP 0603 PHYCOMP 8-resistor bussed network Phycomp’s new R-Chip takes up less space that equivalent discrete resistors In addition, in surface-mounting processes the use of the resistor network instead of discrete resistors allows for significant savings in placement costs and, since the number of solder joints is reduced from 16 to 10, savings in inspection costs after mounting. 2 MSC813 1.0 0.8 65% saving ! 0.6 0.4 0.2 0.0 0603 x 8 product cost Fig.2 10P8R network x 1 mounting cost PC board cost The use of a resistor network can give up to 65% saving on total cost Specifications and mechanical details Table 1 Quick-reference data Resistance range Resistance tolerance Temperature coefficient 10 Ω to 100 Ω 100 Ω to 100 kΩ Number of resistors Number of terminals Abs. max. dissipation @ Tamb = 70 °C Operating temperature range Climatic category ( IEC 68 ) Basic specification Max. permissible voltage 10 Ω to 100 kΩ 5% 0 ~ 500 ppm/°C 200 ppm/°C 8 10 1/32 W, 1/16 W 55 to +125 °C 55/125/56 IEC 115-8 25 V, 50 V (DC or RMS) Mechanical construction MSD070A Fig.1 cost index The network comprises 8 resistors in a 10-pin 1206 case with two ground connections at pins 5 and 10 (Fig.3). The provision of two ground pins diametrically opposite each other simplifies placement on the PC board since it means that the component can be placed either way round on the solder pads. The resistors are constructed on a high-grade ceramic (aluminium oxide) body. Internal metal electrodes are added at each end and connected by a resistive paste, which is applied to the top surface of the substrate. The composition of the paste is adjusted to give the approximate resistance required and the value is trimmed to within tolerance by laser cutting of this resistive layer. 3 MSC817 10 9 8 7 6 300 10 s T ( o C) 250 ~ 245 C 200 215 o C 180 o C 150 130 o C 260 oC o • Mount the products as far as possible from the break line of the PC board and from any line of large holes on the PC board • Do not break the PC board by hand. We recommend the use of a machine or jig to break the board. 10 s 1 2 3 4 IC IC 5 100 MSC814 Fig.3 0 The resistive layer is covered with a protective coating and printed with the resistance value, after which the external end terminations are added. For ease of soldering, the outer of these end terminations is a leadtin alloy. Figure 4 gives the outline and dimensions of the resistor network. Fig.6 W1 W protective coating IC C A IC P1 103 P2 W pull-up resistor L W 1206 (3216) 3.30 ± 0.20 1.60 ± 0.15 OUTLINE VERSION T 0.55 ± 0.10 A 0.50 ± 0.05 B 0.35 ± 0.05 REFERENCES IEC JEDEC EIAJ C P G 0.40 ± 0.15 0.64 ± 0.05 0.40 ± 0.15 EUROPEAN PROJECTION ISSUE DATE 98-07-10 MSC815A Mechanical details (dimensions in mm) Typical Applications Figure 5 shows a basic application example that saves space, reduces interconnection lengths on the PC board and provides for greatly simplified layout design. 4 MSC816 no more through-holes Dimensions Fig.4 Fig.7 damping resistor L size (mm) PC board W 0.35 ± 0.05 W1 0.50 ± 0.05 H1 + 0.40 2.80 _ 0.20 H2 0.80 ± 0.10 P1 0.70 ± 0.05 P2 0.65 ± 0.05 A 3.20 ± 0.10 MSC818 B ceramic substrate 250 Dimension in mm VCC H2 H1 G 200 Fig.5 8R network A 8R network P T 150 Soldering conditions end termination protective coating 100 50 t (s) through hole marking vacuum nozzle 50 The network comprises 8 resistors with two ground connections to facilitate automatic placement resistor layer another component 40 s 2K/s Phycomp’s resistor network as a pull-up network on a computer motherboard Component soldering Reflow soldering profile • Print solder paste to a thickness of 100 to 150 µm • Use rosin-based flux, do not use activated flux (containing, for example, more than 0.2% by weight of chlorine) • Use solder consisting of Sn/Pb in the proportions 63/37 or 60/40. Soldering Conditions Surface-mount resistors are tested for solderability at a temperature of 235 °C for 2 seconds. Figure 6 shows typical examples of soldering cycles that have been found to provide reliable joints without any damage. Soldering footprint (dimensions in mm) Handling precautions Soldering precautions • Note that this product will be easily damaged by rapid heating, rapid cooling or local heating • Do not subject the product to thermal shock by the use of soldering temperatures greater than 100 °C. We recommend the use of preheating and annealing (gradual cooling) stages during the soldering cycle • Wave soldering of this product is not recommended since this can lead to the formation of solder bridging due to the narrow 0.8 mm pitch of the product. Solder gun precautions Note the following precautions when using a solder gun for replacement: • The tip temperature must not exceed 280 °C for 3 s. To ensure this, use a solder gun with a power of less than 30 W • The solder gun tip must not come into direct contact with the product. Substrate handling precautions • Ensure that the PC board is not flexed excessively after the product and other components have been soldered. If necessary, use a support pin to prevent excessive flexing on the PC board support pins Fig.8 MSC819 Precautions when handling substrates Storage conditions Note the following precautions when storing the product: • Avoid high-temperature, high-humidity and dusty environments and atmospheres containing corrosive gases (e.g. hydrogen chloride, sulphuric acid gas, hydrogen sulphide) since these can degrade terminal solderability • Keep the storage temperature less than 40 °C, relative humidity less than 70% and, if possible, do not keep in storage longer than 6 months • Avoid direct heat and sunshine to prevent the packaging tape from melting and sticking to the product. Ordering information Table 2 Order number: 2350 230 10... Resistance decade (Ω) 10 to 91 100 to 910 1 to 9.10 k 10 to 91.0 k 100 to 910 k Last digit 9 1 2 3 4 Complete the catalogue number (see Table 2) by replacing the first two dots of the remaining code by the first two digits of the resistance value and the third dot by figure indicating the decade. 5 Ordering example Resistance value of 47 Ω, 5% tolerance, 5000 per reel; the ordering code is 2350 230 10479 More information For more information and data contact your local Yageo sales representative (address on the back cover) or visit our web site on http://www.yageo.com. 6 7 YAGEO - A GLOBAL COMPANY ASIA China, Beijing Tel. +86 10 851 20810 Fax. +86 10 851 20200 China, Dongguan Tel. +86 769 772 0275 Fax. +86 769 791 0053 China, Suzhou Tel. +86 512 6825 5568 Fax. +86 512 6825 5386 Hong Kong Tel. +852 2342 6833 Fax. +852 2342 6588 Japan, Tokyo Tel. +81 3 5833 3331 Fax. +81 3 5833 3116 Korea, Kyunggi-Do Tel. +82 31 712 4797 Fax. +82 31 712 5866 Malaysia, Kuala Lumpur Tel. +60 3 5882 2854 Fax. +60 3 5882 8700 Malaysia, Penang Tel. +60 4 397 3317 Fax. +60 4 397 3272 Singapore Tel. +65 6244 7800 Fax. +65 6244 4943 Taiwan, Taipei Tel. +886 2 2971 7555 Fax. +886 2 2917 4286 EUROPE Benelux, Roermond Tel. +31 475 385 357 Fax. +31 475 385 589 Czech Republic, Brno Tel. +420 7 2317 5035 Fax. +420 5 4325 4936 France, Paris Tel. +33 1 55 51 84 00 Fax. +33 1 55 51 84 24 Germany, Hamburg Tel. +49 4121 870 0 Fax. +49 4121 870 271 Hungary, Budapest Tel. +36 30 3777 441 Fax. +36 94 517 701 Italy, Milan Tel. +39 02 2411 301 Fax. +39 02 2411 3051 Russia, Moscow Tel. +7 095 585 8853 Fax. +7 095 214 7888 Spain, Barcelona Tel. +34 93 238 9172 Fax. +34 93 217 6536 Sweden, Stockholm Tel. +46 8 735 64 58 Fax. +46 8 642 99 08 UK, Leatherhead Tel. +44 1372 364 500 Fax. +44 1372 364 567 NORTH AMERICA U.S.A., Dallas Tel. +1 972 599 0099 Fax. +1 972 599 0099 U.S.A., Woodinville Tel. +1 425 492 2818 Fax. +1 425 492 2819 For more detailed and always up-to-date contact details of sales offices, distributors and representatives, please go to our web site at: www.yageo.com c YAGEO Corporation All rights are reserved. Reproduction in whole or in part is prohibited without the prior written consent of the copyright owner. The information presented in this document does not form part of any quotation or contract, is believed to be accurate and reliable and may be changed without notice. No liability will be accepted by the publisher for any consequence of its use. Publication there of does not convey nor imply any license under patent or other industrial or intellectual property rights. Document order number: 29398 084 34011 Date of release: May 2001 www.yageo.com