APPLICATION NOTE #100 Proposal Design Manufacture High Speed Mult

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APPLICATION NOTE #100 Proposal Design Manufacture High Speed Mult

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APPLICATION NOTE #100
Proposal Design Manufacture High Speed Multichip Module Signal Processing
Point Contact: Terlizzi Tel:(516) 752-2418
APPLICATION NOTE #100
Revised 6/96
Technical Description
Aeroflex proposing thin film MCM, type configuration High Speed Multichip Module Signal Processing. following description module with similar technologies those that will used meet 1GHz data processing speed. Also presented rationale materials processes indicated.
HASP Module
example comparative MCM, HASP module chosen. HASP (Hybrid Associative String Processor) module illustrated Figure designed manufactured design specialist, John Reche. Reche consulant associated with Aeroflex design development advanced packaging technologies. HASP module contains microprocessor that operate parallel processor mode achieve million operations second. This module designed operate clock speed. contains following additional devices: each 20R4 PAL, each 22VlO PAL, each 74FC type transceiver addition decoupling capacitors. technology used silicon silicon substrate, with thin film copper conductors polymer insulating medium. power dissipation approximately watts 2.5" 2.5" package. When sixteen these modules combined together they perform 12.6 giga-operations additions) clock frequency MHz. proposed High Speed module will same technologies described below) except substrate material, which will changed from silicon aluminum nitride. aluminum nitride twice thermal conductivity silicon.
Basic Material Technologies
will combination advanced substrate dielectric materials meet requirements circuit density, clock speed, power dissipation cost. basic module will consist aluminum nitride substrate supporting ultrafine line MCM-D circuit. multilayer conductor pattern copper, interconnects semiconductor devices controlled impedance transmission lines. This technology known high density multilayer interconnect (HDMI). This process successfully been used construct metallization layer substrate structure. proposed multichip module will fabricated aluminum nitride substrate deposition process with polymer, bisbenzocyclobutene (BCB) dielectric layers copper interconnections. polymer choice because dielectric constant (2.70) water absorption. ceramic cover will bonded over completed circuit mechanical protection. Leads will available four sides surface mounting. 1.2.1 Aluminum Nitride Substrate Aluminum nitride (AlN) used substrate bottom package because highly efficient thermal conductor with thermal conductivity W/mK, slightly less than that
APPLICATION NOTE #100
Revised 6/96
HASP DEMONSTRATOR
Microprocessor (16)
Thin Film Multilayer Substrate From Technology
20R4 (16)
22V10
74FCXX Transceiver (12) Cermic Capacitors Chip 0.001 .050" .040" 2.5" Lead Metal Flatpack Lead Centers .050"
Figure
APPLICATION NOTE #100
Revised 6/96
beryllium oxide. attaching directly aluminum nitride substrate, heat transfer optimized (see page Thermal Analysis). Aluminum nitride several other advantages, they are: coefficient thermal expansion substrate very close that silicon die, thus preventing bond failures that could occur under thermal cycling conditions. dielectric constant electrical resistance similar aluminum oxide. material higher bending strength which makes stronger package. basic blank substrate material available from several sources reasonable prices. 1.2.2 Copper conductor patterns advantages using copper over other conductor materials such aluminum tungsten well known. copper reduces resistive losses, improves rise time reduces pulse delay. Typical line widths range from microns microns very dense packing components. 1.2.3 Bisbenzocyclobutene (BCB) Insulator layers From transmission line theory, propagation delays transmission line structure inversely proportional square root dielectric constant. Therefore advantageous lower dielectric constant materials build MCMs that must operate very high frequencies. bisbenzocyclobutene polymeric insulator material with relatively dielectric constant 2.7, major factor design MCM. material will support clock frequencies well above 1000mHz. This substantial improvement over dielectrics normally used multichip modules such alumina polyimide, whose dielectric constants range from high 3.4. material also advantage water absorption which reduces high frequency losses, improves efficiency reduces heating effects. permits practical line widths conductor spacing that used attain characteristic impedance values range Ohms Ohms which matches standard semiconductor requirements.
interconnections
reasons cost delivery, initial units will designed with gold aluminum wire bonding. This technology usable clock frequencies permits quick assembly preproduction units with little extra tooling charges. Eventually, when production quantities generated, conversion tape automated bonding (TAB) will employed reduce costs speed deliveries. permits improved testing very conducive automatic assembly. will also improve frequency response reducing lead bond inductance.
APPLICATION NOTE #100
Revised 6/96
1.3.1 Package Sealing illustrated following package cross section, basic package consists substrate covered with ceramic cover prevent damage provide seal against dust humidity. leads placed substrate edge, where they shaped surface mount plug applications.
Ceramic Cover
Aluminum Nitride Substrate
Thermal Design
1.4.1 Thermal Management thermal management facilitated ways first, partially eliminating power consumption circuit, second, allowing substrates packages which dissipate heat better. lower capacitance Aeroflex design translates proportional reduction power dissipation. power dissipated interconnections between
POWER
where clock frequency, line capacitance, logic voltage swing. substantial portion total circuit power dissipation typical circuits used charge discharge line capacitance inter-chip voltage swings. modern MCMs, reasonable expect reduction line capacitance least order magnitude over printed circuit boards typical digital circuit. consequence reduced line capacitance, possible reduce power dissipation ASIC logic line drivers. estimated that average power dissipated chip dissipated periphery line drivers. Line drivers normally designed handle long traces boards. Many circuits developed technology have reduced power dissipation line driver level because they ASICs which tailored purpose. addition,the substrate material optimized dissipate larger amounts power unit area closely match coefficient expansion large size semiconductor dies. increased packaging density MCMs requires better heat conduction capability than older hybrid technology required. Alumina ceramic longer suitable because coefficient expansion high (which would stress large dies attached thermal conduction poor. Aluminum nitride will used because excellent electrical insulating properties, good heat conduction matching thermal coefficient expansion.
APPLICATION NOTE #100
Revised 6/96
1.4.2 Thermal resistance figure next page presents thermal resistance calculations internal semiconductor outside module. calculation made determine thermal resistance from semiconductor junction case, J-C. This calculation assumes heat spreading, which conservative assumption that will result higher than actual thermal resistance. smaller surface area will have higher thermal resistance, other factors being equal. calculation involves three layers material, silicon die, adhesive, aluminum nitride case substrate. bonding method adhesive used does cause voids under die, effects voids will neglected. calculated thermal resistance 0.431 inch square 0.178 C°/W, 0.300 inch square 0.368 C°/W. This calculation based uniform heat source (the same heat flux density) applied across semiconductor die. This calculation will accurately determine thermal resistance have about same power dissipation unit surface area, since there will thermal effects from another. however, higher power dissipation unit area, this higher dissipating will represent worst case temperature condition, thus limit maximum junction temperature rise given maximum case temperature. This simplified analysis will also apply this situation, since hotter will create heat spreading effect, which results lower thermal resistance. While true that this hotter will tend increase thermal resistance nearby lower power density devices, reality hotter will worst case. modern multichip modules which microprocessors, large ASICs memory devices, dimensions typically twenty times substrate thickness. Under these conditions,because large surface area thickness ratio, most heat flows downward heat sink heat spreading kept minimum. When designed, more through finite element thermal analysis will performed actual configuration confirm these approximations. 1.4.3 Heat Sink Thermal Resistance following heat sink, cooled forced shown chart page will maintain junction temperatures below 85°C with power dissipations indicated. 3.2"
2.75"
APPLICATION NOTE #100
Revised 6/96
Multichip Module Thermal Analysis
Silicon Attach Adhesive Heat Flow Aluminum Nitride
Thermal Resistance calculation Thermal resistance C°/W= Thickness/(Thermal conductivity)(Area) Note: dimensions Inches Silicon die, 0.020 inches thick 0.431 inches square 0.20/(2.13)(0.431)(0.431) 0.051 C°/W Adhesive, 0.002 inches thick 0.002/(0.14)(0.431)(0.431) 0.076 C°/W Aluminum Nitride Substrate, 0.40 inches thick 0.040/(4.25)(0.431)(0.431) 0.051 C°/W Total Thermal resistance 0.178 C°/W; smaller die, mils size, thicknesses remain same, thermal resistance calculated 0.368 C°/W
APPLICATION NOTE #100
Revised 6/96
Characteristics heat sink terms thermal resistance velocity shown below: HEAT SINK THERMAL RESISTANCE VELOCITY
VELOCITY FEET MINUTE 1000 THERMAL RESISTANCE FROM HEAT SINK AMBIENT WATT
This heat sink mechanically attached case. Sufficient pressure least pounds/ inch) conductive joint compound used make intimate thermal contact case. estimated temperature rise determined thermal resistance follows:
Temperature Rise Sizes Junction case Case heat sink Heat sink ambient, (air velocity 300ft/min) Total, junction ambient 0.431"X 0.431" 0.178 °C/W 2.67 0.200 °C/W 5.00 1.100 °C/W =27.50 35.17°C Module 0.300" 0.300" 0.368 °C/W 15W= 5.52 0.200 °C/W 25W= 5.00 1.100 °C/W 25W=27.50 37.02°C
temperature rise 37°C within required maximum junction temperature, maximum ambient temperature 45°C assumed. Please note that these values temperature rise conservative since they assume other mode heat transfer. reality, cooled following additional means: Conduction through bond wires connections. Internal module convection from case convection around case. Heat spreading conduction from edge substrate. Radiation from case, from case heat sink air. Heat capacity storage effects substrate heat sink, duty cycle less than 100%.
Conclusion
Aeroflex proposed thin film MCM, type configuration High Speed Multichip Module Signal Processing this application note. technology develop MCMs that used meet data processing speed available commercial military products. your specific needs please contact application representative.
APPLICATION NOTE #100
Revised 6/96

APPLICATION NOTE #100 Proposal Design Manufacture High Speed Mult

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