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©VENTEC ELECTRONICS Thermally Conductive Substrates; A Rapidly Growing PCB Mfg Opportunity.

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Presentation on theme: "©VENTEC ELECTRONICS Thermally Conductive Substrates; A Rapidly Growing PCB Mfg Opportunity."— Presentation transcript:

1 ©VENTEC ELECTRONICS Thermally Conductive Substrates; A Rapidly Growing PCB Mfg Opportunity

2 ©VENTEC ELECTRONICS Areas of Thermal Substrate Application Development; – Power Electronics: DC power supplies, inverters, power controllers, motor drivers. – Automotive Electronics: ABS braking modules, brake energy regeneration – High Speed Computing: Higher speeds mean more excess heat to dissipate. – LED lighting: Backlit LCD monitors*, commercial displays, municipal lighting. Thermal Management Requirements Increasing in Demand in the Marketplace

3 ©VENTEC ELECTRONICS (Almost) Everywhere lighting is in use, LED designs will replace it within 5-8 years. Thermal Management Requirements Increasing in Demand in the Marketplace

4 ©VENTEC ELECTRONICS What is Watts per meter-Kelvin? Heat flow across a surface per unit area per unit time, divided by the negative of the rate of change of temperature with distance in a direction perpendicular to the surface. Also known as Coefficient of Thermal Conductivity

5 ©VENTEC ELECTRONICS Thermal Management Lexicon Thermal Impedance: Cº- /watt The effective temperature rise per unit power dissipation above the temperature of a stated external reference point under conditions of thermal equilibrium. Also known as thermal resistance. Thermal Resistance: ºC/watt A measure of an object's ability to prevent heat from flowing through it, equal to the difference between the temperatures of opposite faces of the body divided by the rate of heat flow. Also known as heat resistance. Thermal Conductivity: Watt/ k A measure of the ability of a substance to conduct heat, determined by the rate of heat flow normally through an area in the substance divided by the area and by minus the component of the temperature gradient in the direction of flow. in 2 m2m2

6 ©VENTEC ELECTRONICS How to Disperse Excess Heat? Radiation/Convection; - Passive/active energy transmission into immediate environment Conduction; – External heat-sink: Copper ladder add-on frame – Internal heat-sink: (Copper-INVAR-Copper) – Thermally conductive substrate (non-metallic) – Thermally conductive insulated metal substrate (IMS)

7 ©VENTEC ELECTRONICS How to Disperse Excess Heat? Passive Heat Sink Active Heat Sink;

8 ©VENTEC ELECTRONICS Types of Thermally-conductive dielectric materials; Pastes & Adhesives: - Passive device thermal under-fill and encapsulation - Passive device permanent mounting. (Fralock) Substrate core and prepregs - Woven-glass reinforced - Non-reinforced dielectric - Metal-clad & metal core substrate; > (IMS, Aluminum, Copper, INVAR core)

9 ©VENTEC ELECTRONICS Functions of Thermally-conductive Dielectric Materials (IMS); Thermal conduction of extraneous heat away from active and passive electronic devices. Electrical insulation of circuitry from chassis. Adhesion – bonding copper to aluminium (IMS substrate) or heat-sinks to chip sets Structural electronic thermally conductive platform.

10 ©VENTEC ELECTRONICS Typical Thermal Conductivity Values;

11 ©VENTEC ELECTRONICS How to Disperse Excess Heat? Thermally conductive PCB laminates and prepregs

12 ©VENTEC ELECTRONICS How to Disperse Excess Heat? Thermally conductive insulated metal substrate (IMS)

13 ©VENTEC ELECTRONICS How to Disperse Excess Heat?

14 ©VENTEC ELECTRONICS Typical CTE Values for Thermally Conductive Materials;

15 ©VENTEC ELECTRONICS CTE differences Inherent in IMS Materials CTE differences between copper, dielectric & aluminium highlighted during thermal cycling. Power-on & power-off heating & cooling cycling. Day/night & seasonal temperature & humidity variation. Thermal Stress fatigue may ultimately cause cracking of solder joints, ceramic components, or delamination of substrate to aluminum.

16 ©VENTEC ELECTRONICS Typical Characteristics of IMS laminates CompanyMaterial Type Thermal Conductivity (W/m*K) DuPontCooLam LX0.80 Arlon91ML BergquistCML Arlon99ML1.10 VentecVT4A BergquistMP Arlon92ML2.00 BergquistHT VentecVT-4A22.50 LairdT-Lam SS 1KA VentecVT-4A33.00

17 ©VENTEC ELECTRONICS Characteristics of IMS laminates: Beware of Data Sheets! A Sampling of Data Sheet Test Methods; Spec/Test MethodIntended Spec Purpose ASTM F433-02:Standard Practice for Evaluating Thermal Conductivity of Gasket Materials * ASTM D :Standard Test Method for Thermal Transmission Properties of Thermally Conductive Electrical Insulation Materials ASTM E :Standard Test Method for Thermal Diffusivity by the Flash Method NANo specification or test method listed * Intended specification for use with Thermally Conductive Electrical Insulation Materials

18 ©VENTEC ELECTRONICS Typical Characteristics of IMS Substrates Single-sided, print-and-etch technology Aluminium 0.5mm – 3mm ( ) thick – Different grades (5052/6061) available to suit different applications – Different Alloys have significant differences in mechanical characteristics Dielectric thickness 75μm – 150μm ( ) Copper thickness; 18 μm+ (1/2 oz +) Thermal conductivity ranges; - Glass reinforced: 0.4 to 3.0 W/mK - Up to 8+ W/mK available for non reinforced dielectrics

19 ©VENTEC ELECTRONICS Primary IMS Aluminum Alloys 5052 & 6061

20 ©VENTEC ELECTRONICS PCB Fabrication considerations: Alloy Physical Differences Alloy Alloyed WithTensileElongation %Yield Brinell Hardness 5052 H32Mg % T6Mg+Si+Fe % H-strain-hardened (wrought products only). Applies to products which have their strength increased by strain-hardening, with or without supplementary thermal treatments to produce some reduction in strength. T-applies to products which are thermally treated, with or without supplementary strain-hardening, to produce stable tempers.

21 ©VENTEC ELECTRONICS PCB Fabrication considerations: Lamination Heavy filler loading leads to differing prepreg flow characteristics at lamination; - Moderately less flow than standard prepreg materials > No fill required, therefore less flow not a process concern - Aluminum-FR4 lamination bonds materials with highly differing CTE rates; > Low/slow rates of cooling at conclusion of cure segment are advised. > Pin-less Lamination requires caution in tooling stack heights.

22 ©VENTEC ELECTRONICS PCB Fabrication considerations: Drilling Tendency to rapid tool wear due to presence of thermal filler and aluminum. Drill bits with under-cut geometry preferred Chip loads 50-60% of that used for FR4 Spindle speeds 60-70% of that used for FR4 Drilling from copper side generally more successful in avoiding exit/entry burrs.

23 ©VENTEC ELECTRONICS IMS PCB Fabrication considerations: Routing Rapid tool wear a significant Issue General Parameter Recommendations; - Router RPM speed; 15,000 to 20,000 RPM - Table Feed; IPM - Router Type: - Carbide or Diamond coated 2-flute end mill best option. - Tools (2 or 3 flute end-mills) tend to pull out of collet. - No vacuum path required/desired - Change backer with each new pass. Break-away tabs do not need to be as wide as in standard designs for FR4 laminates. > Scoring across break-away tabs may be effective to assist in part removal with minimal flash removal required.

24 ©VENTEC ELECTRONICS IMS PCB Fabrication considerations: Array Scoring Scoring Aluminum-FR4 IMS composite a Challenge Suggested Starting Parameters; - Scoring Blade RPM range: 1,500 – 2,500 RPM - Scoring Head/Table IPM range: IPM - Blade Tooth Count: > 1-3 blade passes, dependent upon cut depth & material thickness. - Lubricant use very helpful: (Tap Magic: Aluminum). - Scoring across routed array tabs is a good design practice in Al substrate array designs.

25 ©VENTEC ELECTRONICS PCB Fabrication considerations: Solder Mask Much of the surge of interest in IMS is LED Lighting demand. LED Lighting in visual ranges often requires white solder mask as a reflecting surface to enhance brightness. White LPI Solder Masks often brown after assembly due to exposure to flux chemistries and heat in combination. - White LPI does hold up as well as desired, and becomes brittle when cured sufficiently to avoid pink/purple assembly discoloration. - Two newer white masks have shown promise in resisting discoloration; > Peters (SD2491SM TSW) > Sun Chemicals (CAWN 2589/2591)

26 ©VENTEC ELECTRONICS IMS Compatibility with lead-free soldering and thermal cycling Reliability influenced by construction & manufacturing process of IMS. Glass reinforced dielectric has lower Z-axis CTE than non-reinforced materials. Wide range in Tg values in currently available thermal substrates; - Resin chemistry determines Tg and Td

27 ©VENTEC ELECTRONICS Compatibility with lead-free soldering and thermal cycling Surface treatment of aluminium critical in thermal shock performance - Mechanical or chemical roughening of surface μm Rz surface roughness desired for mechanical bond strength. Presence of moisture is critical at Pb-free HASL assembly; Higher internal vapour pressures are generated as the moisture is expelled during reflow operations. Desiccate!

28 ©VENTEC ELECTRONICS Compatibility with lead-free soldering and thermal cycling Desiccate prior to Assembly! Bake panels; Time: minutes (at temp) Temp: 225º – 235º F (107º- 113º C) Stack (preferred): (25.4 – 38 mm) Rack: Use only vertical racks with support the full height of panels.

29 ©VENTEC ELECTRONICS Summary Increasing interest in cost-effective thermal management of electronics; - IMS-type materials are the board-level solution. Choose materials to suit the application - Many different levels of thermal relief available. Do your own qualification tests, and dont take data sheet values too literally. - Ventec VT4A-1 data sheets under-state the thermal capabilities of the material.

30 ©VENTEC ELECTRONICS Thank you for your attention!

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