Latest technology trend of packaging materials for power devices. KYOCERA Chemical Corporation

Transcription

1 Latest technology trend of packaging materials for power devices KYCERA Chemical Corporation

2 Requirement to assembly materials for power devices Encapsulant : Epoxy resin, Silicone Die Bonding wire : Al, Cu ribbon Lead Flame (High thermal conductive substrate) Solder, Die attach paste Die attach materials >>> Rigidity of Pb free solder, Heat resistance of the organic die attach materials Bonding wire >>> Heat resistance of Al and Cu Encapsulants >>> Heat resistance Target temperature >>> 175deg.C 25deg.C 2/17

3 Encapsulation for power device packages Properties requirement for power device package materials >>> Heat resistance >>> Heat dissipation λ=.7w/m K λ=3.1w/m K By encapsulating with high thermal conductive compound, localized overheating can be avoided. 3/17

4 High thermal conductivity molding compound 4/17

5 Increasing of thermal conductivity of molding compounds Effect of thermal conductivity of the molding compounds for thermal resistance. Thermal resistivity of the package (deg.c/w) General molding compound 一般の汎用封止樹脂 QFP16pin, 7.6mm sq. die Alloy アロイフレーム frame Calm condition 無風状態 Thermal conductivity of the molding compound (W/m K) Thermal resistivity of the package (deg.c/w) Wind velocity.2 m/s Wind velocity 2. m/s SP1pin, 4mil Cu frame Thermal conductivity of the molding compound (W/m K) Thermal resistance of the packages can be reduced by introducing high thermal conductive molding compound. 5/17

6 Increasing of thermal conductivity of molding compounds Law of mixture for thermal conductivity Bruggeman s law of mixture 1-v=[(λe-λd)/(λc-λd)](λc/λe)1/3 λe:thermal conductivity of composite λc:thermal conductivity of matrix resin λd:thermal conductivity of filler v:volume fraction of filler For high thermal conductivity High thermal conductive filler High content of the filler High thermal conductive matrix resin Relative thermal conductivity(-) Experimental (Maxwell) (Bruggeman) Concentration of silica (vol%) 6/17

7 Increasing of thermal conductivity of molding compounds High thermal conductive filler Filler Thermal conductivity Thermal expansion Specific gravity Fused silica Si2 1.3 (W/m K).5 (ppm/deg.) 2.21(-) Crystalline silica Sio Alumina Al Silicon nitride Si3N Magnesium oxide Mg Boron nitride BN Ammonium nitride AlN Beryllium oxide Be Silicon carbide SiC Titanium oxide Ti /17

8 Increasing of thermal conductivity of molding compounds High filler loading Mooney s equation (Viscosity of the composite) ln (E/E1) = K P / (1-P / Pm) E : viscosity(composite) E1 : viscosity (matrix) P : filler volume content Pm : Maximum packing rate of the filler K : constant Low viscosity High viscosity No flow high high viscosity viscosity Mono dispersion Ideal (delicate) Large particle with sufficiently small particle o fill vacancy (realistic) low low content P Pm high low 8/17

9 Increasing of thermal conductivity of molding compounds Viscosity change calculation from each packing models Large particle only Combination of large and small particle (not saturated) (saturated) (excess) Viscosity (Pa s) Experimental data pml=.74 pms=.6 Calculated Small particle ratio 9/17

10 Heat resistant molding compound 1/17

11 KYCERA Chemical Confidential Volume resistivity Water absorption Volume resistivity [ohm cm] Flexural modulus Flexural modulus [GPa] Flexural strength Flexural strength [MPa] Heat resistant molding compound Performance of current molding compound applied to automotive 1.E+17 1.E+16 1.E+15 1.E+14 1.E+13 1.E deg.C store 2deg.C store 1.E+11 1.E Storing time [h] deg.C store 2deg.C store Storing time [h] 2 175deg.C store 2deg.C store Water absorption [% ] ; PCT2atm deg.C store 2deg.C store Storing time [h] Thermal expansion coefficient Glass transition temperature Glass transition temperature [deg.c] 175deg.C alpha1 175deg.C alpha2 2deg.C alpha1 2deg.C alpha deg.C store / Storing time [h] Storing time [h] Thermal expansion coefficient [deg.-1] Storing time [h] 2deg.C store

12 KYCERA Chemical Confidential Heat resistant molding compound Performance of current molding compounds applied to automotive Ion impurity Cl- Ionic impurity Cl- [ppm] degC store 2degC store Ion impurity Na+ Ionic impurity Na+ [ppm] degC store 2degC store ph Storing time [h] 175degC store 2degC store Electrical conductivity 1 Storing time [h] 175degC store 2degC store 8 ph [-] 6 4 EC [ms/m] Storing time [h] Storing time [h] 12/17

13 Heat resistant molding compound Performance of current molding compounds applied to automotive Result of the degradation test at 175/2degC is as follows. * Could keep electrical properties and mechanical properties. * Could keep water absorption and impurities level * Slightly change could be seen in thermal expansion and glass transition temperature There may be the solution under 2 deg.c condition in extension of current compounds. For higher temperature condition, new heat resistant matrix resin should be applied. 13/17

14 Heat resistant molding compound Heat resistant matrix resin Several new structure have been studied and high performance can be expected by combination with high thermal conductivity. Confirmation, however, with the actual devices is still needed. Heat resistant matrix resin Multi-functional epoxy resin Crystalline type epoxy resin Polyimide resin Cyanate ester resin Benzoxazine resin Benzoxazine resin Insulation 29 Takeichi et al Toyohashi University of Technology Modification by diamine or siloxane Glass transition temperature ; over 25deg.C Crystalline type epoxy resin Insulation 21 Takahashi et.al Yokohama National University.. Pai-stack of naphthalene or anthracene segment. Glass transition temperature ; 236deg.C Thermal expansion ; 49 ppm/deg. Cyanate ester resin N C Insulation 21 Takahashi et.al Yokohama National University. Combination with the specific epoxy resin Glass transition temperature ; 215deg.C n 14/17

15 Heat resistant molding compound Effect of modification by maleimide Room temperature Bi-phenyl series Fracture toughness K1c (MPa m1/2) Novolac series Multi-functional series Polyimide series Homo polymerization of maleimide Reaction between maleimide and amine compounds 215deg.C Glass transition temperature (deg.c) 25 15/17

16 Heat resistant molding compound Item Grade Unit KE-G125DS X6 KE-G125DS X5HT KE-G3 HT KE-G3D Filler type - Si2 Al23/ Si2 Al23/ Si2 Si2 Matrix resin - Modified multi functional EP Modified multi functional EP Hydrophobic EP Hydrophobic EP Spiral flow (175oC) cm Gel time (175oC) s Viscosity (175oC) Pa s Specific gravity C.T.E a1/ a2 ppm/ o C 14 / / / 5 1 /38 Tg o C Flexural strength (25oC) MPa Flexural modulus (25oC) GPa Mold shrinkage % Moisture absorption (PCT 2atm.) % Volume resistivity (15 o C) W cm 5E+12 5E+12 5E+12 5E+12 Impurity Cl- ppm Thermal conductivity W/mK /17

17 Summary For the new power devices, heat resistivity of the assembly materials are concerned. High heat resistance and high heat dissipation should be required for the encapsulation resin. Target temperature varies from 175deg.C to 25deg.C. There may be the solution under 2 deg.c condition in extension of current compounds. For higher temperature condition, new heat resistant matrix resin should be applied. Several new structure have been studied and high performance can be expected by combination with high thermal conductivity. Confirmation, however, with the actual devices is still needed. Closer relationship between device and material should be important for achieving the new power device package. 17/17

18 18/17

19 Calculated maximum packing rate (Pm) for each packing form (A) Large particle only (B) Large particle + Small particle (not saturated) Pm= pml Pm= pml/(1-x) Pm ; Maximum packing rate of total particle pml ; Maximum packing rate of large particle pms ; Maximum packing rate of small particle x ; small particle rate for total particle (C) Large particle + Small particle (saturated) x= (1/pmL-1)/(1/pmL+1/pmS-1) (D) Large particle + Small particle (excess) Pm= pms/[(1-pms)x+pms] 19/17

20 Change of viscosity by small particle replacing -fitting to the theoretical curve- Viscosity (Pa s) pml=.74 pms=.52 Experimental data pml=.74 pms=.6 pml=.74 pms=.74 By comparison between actual and calculated viscosity curve, packing mode of large and small filler could be estimated, for large filler pml=.74 >>> rhombohedral for small filler pms=.6>>> orthohombic Small particle ratio 2/17

21 Effect of small particle diameter to the viscosity 15 Viscosity (Pa s) Small particle diameter (um) 21/17

22 appendix Typical packing form and maximum packing Packing form Packing rate Tetragonal series (a) cubic.54 (b) orthorhombic.6 (c) rhombohedral.74 Hexagonal series (d) orthorhombic.6 (e) tetragonal spheniodal.7 (f) rhombohedral.74 22/17

23 Increasing of thermal conductivity of molding compounds Properties of high thermal conductive molding compounds Item unit Crystalline silica (KE-85S) Silicon nitride (KE-87) Combination Alumina and others (KE-88) Combination Alumina and others (G125HT) Spiral flow cm Gelation time sec Specific gravity Thermal expansion coefficient (alpha 1) ppm/deg Glass transition temperature deg.c Flexural strength (room temperature) MPa Flexural modulus (room temperature) GPa Thermal conductivity W/m K (Kyocera chemical products; representative data) 23/17

24 Increasing of thermal conductivity of molding compounds High thermal conductive matrix resin Matrix resin General novolac Bi-phenyl Thermal conductivity(w/m K) n 3 High density of of pai-electron Staking 24/17 structure of of the the segment based on on the the affinity by by pai-electron.

25 Estimation X 線回折回折によるによる分子配向性 of the 分子配向性の定量化 orientation by X-ray diffraction Intensity(cps) Increasing of thermal conductivity of molding compounds 8 6 bserved data Gaussian fitting 4 2 High thermal conductive matrix resin 2 I x m ( ) I obs = exp + ax + b 2 2πσ 2σ I obs : 実測値 measured value x :2θ/θ χ : / θ peak center 2θ /θ m : ピークセンター値 (2θ/θ) σ : 標準偏差 standard deviation ax+b:back ground θ/θ 2d sinθ = λ p-cnge p-bp p-bpdge/ p-badge TMBPDGE m (d/a ) (4.63) 19.5 ( ) (4.58) 19. (4.67) σ λ:x-ray 波長 wave length d : Distance 配向間距離 between orientation H H H 2 n 3 Ichikawa et al, J.Adhesion society of Japan, 4, 51(24) 25/17