1. © International Rectifier 2002 www.irf.com 1 DirectFET  MOSFETs Double Current Density In High Current DC-DC Converters With Double Sided Cooling

2. © International Rectifier 2002 www.irf.com 2 Increasing Current Requirement In DC-DC Converters  DC-DC converters for next generation Intel and AMD microprocessors  Trending towards >100A or 25A per phase  Core processor voltages are stabilizing around 1V

3. © International Rectifier 2002 www.irf.com 3 The Challenge: How To Remove The Heat  Current requirements  PCB size   Less and less area to dissipate the heat  30% of R DS(on) of best SO-8 is due to package Power Dissipated in a VRM Module 0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50 5.00 1996199719981999200020012002 Power dissipated/in.sq (W/in 2 )

4. © International Rectifier 2002 www.irf.com 4 Thermal Limitations Of Single-Sided Cooled SO-8  Top-side cooling is inefficient  PCB is the main path of heat dissipation  New SO-8 derivatives improve Rth(j-b), to make it easier to dissipate heat into PCB and lower junction temperature –Fairchild BottomlessSO8™, Siliconix PowerPak™, leadless SO-8  PCB thermal conduction is at its limit now  Standard and derivative SO-8 can only be effectively cooled on 1 side Rth(j-c): 18°C/W Rth(j-pcb): 20°C/W max + Rth(pcb-a)>40 °C/W SO-8 Rth(j-a) top >55°C/W at 400 LFM Actual measurement Rth(j-a) bottom >60°C/W

5. © International Rectifier 2002 www.irf.com 5 What Is DirectFET Power Packaging?  Large area source and gate contacts are directly soldered onto the PCB board  Copper drain clip facilitates the drain connection and also improves transfer of heat from the top of the device.  Proprietary passivation system for electrical isolation, soldering mask and die protection copper track on board copper ‘drain’ clip passivated die die attach material gate connection source connection

6. © International Rectifier 2002 www.irf.com 6 SO-8 1.7 mm Cu-strap SO-8 DirectFET 0.7 mm Best Package Resistance In Any SMT Package  Reducing Die-Free Package Resistance by over 90% over SO-8 0.1mOhm

7. © International Rectifier 2002 www.irf.com 7 Enabling Efficient Dual Sided Cooling  Increases the power dissipated out of the package by removing the heat very efficiently through the top of the package. Rth(j-c): 18°C/W Rth(j-b): 20°C/W max SO-8 Gap filling thermal pad to metallic chassisGap pad cannot justify cost with SO-8 + Rth(pcb-a) >40 °C/W DirectFET  Rth(j-a) top >55°C/W at 400 LFM Rth(j-pcb): 1°C/W Rth(j-c): 3°C/W Rth(c-a) gap pad <9°C/W + Rth(j-a) top <12°C/W Rth(j-a) bottom >60°C/W Rth(j-a) bottom >41°C/W + Rth(pcb-a)>40 °C/W

8. © International Rectifier 2002 www.irf.com 8 Top side cooling benefits  Increases the power dissipated out of the top of the package by 50% compared to standard SO-8 –And by 100% when compared to Bottomless SO-8 105°C PCB Temperature and 70 °C Ambient Minimum footprint. Gap filler.

9. © International Rectifier 2002 www.irf.com 9 Specifications And Availability  20VN for servers and very high end desk-tops.  30VN devices for notebooks and designers who require a higher safety margin.  Sample available immediately, volume production 3 rd quarter 2002  Extensive reliability testing completed.

10. © International Rectifier 2002 www.irf.com 10 50 o C Cooler In Still Air!  Measured results at max standard SO-8 current in still air

11. © International Rectifier 2002 www.irf.com 11 35A/Phase Using 2 DirectFET MOSFETs!  3 applications for DirectFET MOSFETs: –35A/phase with a single pair of DirectFET MOSFETs using top side cooling –33% more current in still air –50°C cooler and up to 3% higher efficiency at same current level DirectFET 30VN Vs 30VN SO-8 using same silicon technology 12V IN, 1.3V OUT, buck Converter @300kHz, 105°C max PCB temperature 17A more! 125 o C Tj 33% more 105 o C Tj 3% 75 o C Tj

12. © International Rectifier 2002 www.irf.com 12 100A at 85% Efficiency

13. © International Rectifier 2002 www.irf.com 13 Double Current Density for 30A/phase!  50% smaller solution footprint  100% improvement in Current Density!  In real circuit, can cut part count by up to 60% compared to best SO-8 (2 DirectFETs replace 5 SO-8)  And lower system cost

14. © International Rectifier 2002 www.irf.com 14 Lower Total System Cost  Cost of heat removal using SO-8 –Additional 1 oz. Cu for the whole PCB area @ >$0.25/sq. in (>$3.50/system) –Additional fan ($2 to $3/system) –Using heat pipe and additional fan ($4 to $10/system)  DirectFET MOSFETs –Can use chassis for heat removal with no additional fan –Can use minimum PCB footprint and fewer devices  DirectFET MOSFETs cut the cost of heat removal by at least 50% –Reduce cost of heat removal –Cut the size of PCB

15. © International Rectifier 2002 www.irf.com 15 4-phase Converter Using DirectFET MOSFETs  Single DirectFET pair/phase for current up to > 25A/phase in a 3.8in x 1.25in footprint for a total of 100A. Existing best 60A.  Low profile allows the DirectFET to be mounted on the back of the board with heatsink and still stay within VRM outline specifications. Heatsink added to remove heat from top of DirectFET TM away from board

16. © International Rectifier 2002 www.irf.com 16 solder mask defined pads drain rail gate rail Source rail Additional drain contact and/or further mechanical stability Ease of Layout  Easier board layout  Easier to parallel

17. © International Rectifier 2002 www.irf.com 17 DirectFET can replace SO-8 with minimal rework Gate = Pin 4 Source = Pin 1 - 3 Drain = Pin 5 - 8 DirectFET outline Vs SO-8 Outline A board can be reworked with a few simple changes

18. © International Rectifier 2002 www.irf.com 18 Alternatives to dissipate heat through the top of the package Forced air cooling + finned sink Gap filling thermal pad to metallic chassis Forced air cooling

19. © International Rectifier 2002 www.irf.com 19 Bend Strength Measurement  DirectFET far outlasted the ceramic capacitors on the board in this measurement  Reliability testing demonstrate reliability similar to SO-8

20. © International Rectifier 2002 www.irf.com 20 DirectFET Package in Summary Reduce package resistance  Increase efficiency  With MOSFET in sub-10mOhm R DS(ON), the package becomes an important contributor to the resistance. Improve thermal characteristics  Enables dual sided cooling in SMT  Remove the heat from the device faster and away from PCB Reduce stray inductance  To enable faster switching frequencies and better response to current transients Double current density Cut PCB by 50% Cut part count by up to 60% Lower total system cost Compatible with high volume manufacturing processes  Easy to design, easy to parallel DirectFET power packaging Environmentally friendly  Lead and bromide free Low profile  0.7mm high