JPH05121578A - Composite base material having high thermal conductivity and low alpha-particle emission property for electronic package - Google Patents

Abstract

PURPOSE: To obtain a high memory density circuit package, using a MOS memory chip of high memory density by forming from a circuit card, in which a filler is first added to a dielectric containing a perfluorocarbon polymer and a synthetic inorganic filler. CONSTITUTION: This minute electronic circuit package contains an integrated circuit stacked on a circuit card and has an electric connection of a signal, a power and a ground therebetween. The circuit is formed of a filled polymer dielectric, containing a perfluorocarbon polymer and a synthetic inorganic filler which is dispersed all over in this polymer and has a low alpha particle radiation rate, a high thermal mobile coefficient and a low thermal expansion coefficient. The filled polymer is set to have a thermal expansion coefficient lower than that of a polymer and a thermal mobile coefficient high than that of a polymer. This is in particular advantageous in the use of a high memory density MOS memory chip circuit package.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to microelectronic circuit packages having thermally stable organic fluorocarbon polymer composite dielectric structures, and more particularly to high circuit density packages. This circuit package is characterized by a circuit-dense integrated circuit chip that is highly sensitive to alpha particle emission. More specifically, the present invention relates to the addition of low dielectric constant, high thermal conductivity, low alpha particle emitting fillers to fluorocarbon polymers to form dielectric composites.

In one particularly preferred embodiment, the filler is thermally conductive, electrically non-conductive and encapsulated within a dielectric film, coating or layer. In this example of the invention, the filler particles are contacted with a slurry, dispersion, suspension or emulsion of a dielectric polymeric material in a solvent and heated to drive off the solvent and deposit the polymeric material on the filler particles. As a result, a thermally conductive and electrically non-conductive composite material containing conductive filler particles in the polyfluorocarbon dielectric was obtained.

[0003]

2. Description of the Related Art The general structure and manufacturing method of electronic packaging are, for example, Principles of Electronic Packaging of Donald P. Sraphim, Ronald Lasky and Che-Yo Li. )
(McGraw-Hill Book C
ompany, New York, NY, USA, published in 1988)
And Microelectronic Packaging Handboo by Rao R. Tummala and Eugene J. Rymaszewski
k;) (Van Nos
trand Reinhold, New York, NY, 1988
Annual publication), and both publications are cited.

As described by Seraphim et al. And Tumara et al., Electronic circuits include a large number of individual electronic circuit components. For example, it contains thousands and millions of individual resistors, capacitors, inductors, diodes and transistors. These individual circuit components are interconnected to form a circuit, and the individual circuits are interconnected to form a functional unit. Power and signals are distributed through these interconnections. Individual functional units require mechanical support and structural protection. This electrical circuit requires electrical energy to function and removal of thermal energy to maintain function. Microelectronic packages such as chips, modules, circuit cards and circuit boards are used to protect, house, cool and interconnect circuit components and circuits.

Within a single integrated circuit, an integrated circuit chip provides interconnections between circuit components and circuits, heat dissipation and mechanical protection. In the art, this chip is a "zero order"
Characterized as a package, the chips contained in the module are referred to as first level packaging.

There are even higher levels of packaging. The second level packaging is circuit cards. The circuit card has at least four functions.
First, circuit cards are used because the total number of circuits or bits required to perform the desired function exceeds the total number of bits in the first level package or encapsulated chip. Second, the second level package or circuit card provides a portion of the component that is not easily integrated into the first level package or encapsulated chip or module. These components include, for example, capacitors, precision resistors, inductors, electromechanical switches, optical couplers, and the like.
Third, the circuit card provides signal interconnection with other circuit elements. Fourth, the second level package has the function of heat management, that is, it dissipates heat.

Most applications, especially personal computers, high performance workstations, mid-range computers and mainframe computers, have third level packaging. This is a board level package. This board is a connector for accepting multiple cards and circuitizing elements for inter-card communication.
on), I / O devices for external communication and often sophisticated thermal management systems.

The package features a material used as a dielectric, such as a ceramic package or a polymer package. The basic manufacturing method of polymer-based composite packages is George P. Schmitt, Bernd K. Appelt and Jeffrey T. Gotro.
See Seraphim, Rusky, and Lee's Electronic Packaging Principles, cited above, pages 334-371, entitled "Polymers for Electronics and Polymer-Based Composites."
nd Polymer Based Composites for Electronic Applicat
ions), and also P. Seraphim, Donald E. Barr, W
illiam T. Chen, George P. Schmitt, and Rao R. Tummala, also cited earlier, by Tumala and Rymaszews.
Ki) Microelectronic Packaging, pp. 853-922, "Printed Circuit Board Packaging"
ing) ”.

In one method of manufacturing a polymer package, particles such as fibers and spherical particles are impregnated with resin. This step involves coating the particles with a resin, for example with an epoxy resin solution, evaporating the solvent contained in the resin and partially curing the resin. The partially cured resin is referred to as a B-stage resin. A material composed of a granular material and a B-stage resin is called a prepreg. This prepreg is easy to handle and stable and can be cut into sheets for subsequent processing.
Typical resins used to form prepregs include epoxy resins, dicyanate resins, polyimides and fluoropolymers.

Epoxy resins, dicyanate resins and polyimides have certain processing advantages, but relatively high dielectric constants. In contrast, fluorocarbon polymers have a low dielectric constant. The low dielectric constant of fluorocarbon polymers is useful in applications involving closely spaced circuit surfaces where low signal noise and high propagation speed are important.

Perfluorocarbon polymers are derived from symmetric monomers and therefore dipole effects are minimized. As a result, fluorocarbon polymers are characterized by a low dielectric constant. Furthermore, a symmetrical addition polymerized polymer formed from a symmetrical olefin monomer having a stable C—F bond and having no functional group causing strong polarization is a thermally and chemically stable polymer.

Polytetrafluoroethylene ("PTF
E ") is a particularly stable low dielectric constant polymer. Thermoplastic fluorocarbon polymers such as perfluorovinyl ether polymers (perfluoroalkoxides or "PFA"), polyhexafluoropropylene and chlorotrifluoropropylene polymers and copolymers are crystalline polymers with high melting points and glass transition temperatures.

Processing of polymer substrates includes drilling vias and through holes. Vias and through holes are drilled into individual core structures or partially laminated modules. The next process is to form a circuit, that is, a Cu signal line pattern, that is, a power line pattern on the prepreg. Circuitization is performed additively or subtractively. The resulting circuitized prepreg is referred to as the core. An adhesive is generally required between the circuit and the prepreg, especially in the case of polyimide prepreg.

This composite printed circuit package is manufactured by inserting additional prepreg sheets and surface circuits into the core (including signal core, signal / signal core, power core, power / power core and signal / power core). .. After lamination, the drilling, photolithography and plating processes are repeated to obtain a multilayer composite.

The use of low dielectric constant fluorocarbon polymers in the core results in cores with low signal dissipation and signal distortion, which is ideal for high frequency applications. However, the prior art perfluorocarbon polymer dielectrics suffered from a number of drawbacks.

The first is that the glass filler having a low thermal conductivity and the perfluorocarbon interact with each other to have a low thermal conductivity. Secondly, the glass-reinforced perfluorocarbon polymer has a large coefficient of thermal expansion.
126 μm / m ° C. at 14 ° C., 146.3
The temperature is about 113.4 μm / m ° C. Furthermore, glass fillers have high alpha particle emission characteristics, for example alpha particle emission characteristics of the order of 0.02 counts / hour-square centimeter.

In an attempt to overcome these drawbacks,
For example, Arthur (David J. Arthur), Mosco (John
C. Mosko), Connie S. Jackson and G. Robinson Traut "Electrica
US Patent No. 4,84 entitled "Substrate Materials)"
Polytetrafluoroethylene dielectrics may include silane coated glass fibers as described in 9,284. The substrate is formed from a fluorocarbon polymer and a ceramic filler, as described in the aforementioned US patent specifications. Ceramic fillers make up about 55 weight percent or more of the total substrate. The ceramic is disclosed as amorphous fused silica, which is coated with silane.

The use of conductive fillers for conductive compositions is described. For example, Japanese Patent Application Laid-Open No. 61-069853 of Fuji Electric Manufacturing Co., Ltd.
No. 59-193102; published on April 10, 1986) "Conductive fluororesin composition containing conductive filler and PTFE fine particles"
Describes a composition comprising (a) a filler, (b) a fluoropolymer and (c) 5 to 30 weight percent polytetrafluoroethylene microparticles (diameter 10 microns or less). This filler is described as carbon fine particles, carbon fibers, Ag, Al, Cu or nickel particles, Al fibers, stainless steel fibers or glass fibers coated with a conductive metal. The resulting composite is a conductive structure that cannot be used as a dielectric.

Another issue is alpha particle emission from the filler. FET devices are particularly sensitive to alpha particle emission. When alpha particles pass through the channel of a FET device, they can form electron-hole pairs, resulting in spurious signals or erroneous memory states.
This problem is most frequently addressed in the field of gate insulator chemistry and physics, but is especially acute in high density storage chips.

The aforementioned patents and documents do not address the problems of low thermal conductivity of glass reinforced polyperfluorocarbon dielectrics, their emission of alpha particles and the high coefficient of thermal expansion of polyperfluorocarbon dielectrics. Therefore, there is a need for a filler that reduces the emission of alpha particles, has a high thermal conductivity and a low thermal expansion coefficient, and maintains the dielectric properties including the low dielectric constant.

[0021]

SUMMARY OF THE INVENTION One object of the present invention is to provide a microelectronic circuit package with high circuit density.

Another object of the present invention is to provide a high storage density circuit package for use in high storage density MOS storage chips.

Yet another object of the present invention is low alpha particle emission, eg at least about 0.005 curie / hour.
It is to provide a microelectronic circuit package that is less than a square centimeter.

A still further object of the present invention is to have a low coefficient of thermal expansion, for example less than about 126.8 micrometers / m ° C at 32.2 ° C and less than about 113.4 micrometers / m ° C at 146.3 ° C. It is to provide certain polyfluorocarbons, such as polyperfluorocarbon dielectrics.

A still further object of the present invention is to provide a polyfluorocarbon, such as a polyperfluorocarbon dielectric, having a high thermal conductivity.

A further object of the present invention is to achieve the above objects while maintaining the low dielectric constant of the polyfluorocarbon resin.

[0027]

The above and other objects of the present invention are achieved by the synergistic effect of a synthetic heat conductor dispersed in a polyfluorocarbon resin as a filler and encapsulated. As an example of the present invention, a microelectronic circuit package is presented. This package contains an integrated circuit mounted on a circuit card. The package contains electrical connections for signal, power and ground between the circuit card and the integrated circuit chip.

The circuit card is formed from a polymeric dielectric plus filler. The dielectric contains a perfluorocarbon polymer and a synthetic inorganic filler. The filler has a low alpha particle emission rate, a high coefficient of heat transfer and a low coefficient of thermal expansion and is endlessly dispersed within the polymer.

More specifically, the filled polymer has a lower coefficient of thermal expansion than the polymer itself and a higher coefficient of heat transfer than the polymer itself.

In a further embodiment of the invention, the synthetic thermal conductor particles are prepared by encapsulating in an encapsulant. In the present invention, the conductor particles are coated and encapsulated with an emulsion or colloidal dispersion of polyfluorocarbon. The resulting dispersion of heat conductive particles and polyfluorocarbon is applied to a polyfluorocarbon sheet or placed between the polyfluorocarbon sheets and heated to drive off volatile components. This material is then sintered to form the dielectric of the present invention, as is well known in the polytetrafluoroethylene art.

That is, the microelectronic circuit package and the manufacturing method thereof according to the present invention have a low coefficient of thermal expansion, for example, 32.
Less than about 126.8 micrometers / m ° C at 2 ° C, 14
Provide a high circuit density microelectronic circuit package featuring a dielectric with a coefficient of thermal expansion of less than about 113.4 micrometers / m ° C at 6.3 ° C, a high coefficient of thermal diffusion and a low alpha particle emission rate. It is a thing. Low alpha particle emission rates, such as at least about 0.0005 curie / hour-less than a square centimeter, are particularly advantageous for packaging high storage density circuits for use in high storage density MOS storage chips.

[0032]

The invention can be better understood with reference to the accompanying drawings.

In accordance with the invention described herein, a microelectronic circuit package having integrated circuits mounted on a circuit card is presented. This package is shown generally in FIG. The package 1 has an integrated circuit chip 51 on a card 11. Signals between the integrated circuit chip 51 and the card 11,
Make electrical connections for power and ground.

In the present invention, the circuit card 11 is formed from a filled polymer dielectric 21. The filled dielectric is: a. Perfluorocarbon polymer b. It has a synthetic inorganic filler.

The structure of the composite is shown in more detail in FIGS.

Polyperfluorocarbon is a polymer containing one or more of tetrafluoroethylene CF ₂ ═CF ₂ , perfluoropropylene CF ₂ ═CF—CF ₃ or perfluoroethers such as CF ₂ ═CF—O—CF ₃ . Furthermore, non-perfluorinated fluorocarbons such as vinyl fluoride CF ₂ ═CHF, vinylidene fluoride C
H ₂ = CF ₂ or chlorotrifluoroethylene CClF
= CF ₂ etc. can also be used. Perfluorocarbons are preferred due to their low dielectric constants, but asymmetric fluorocarbons can also be used as a partial replacement due to their low glass transition temperature and therefore relative ease of processing.

Generally fluorocarbons are predominantly perfluorocarbons. In one preferred example, the perfluorocarbon is polytetrafluoroethylene.

Typical prior art fillers are SiO ₂ products such as quartz, amorphous fused silica or glass fibers.
However, the filler in the present invention is a synthetic filler, which is a conductive filler having a low alpha particle emission rate, a high heat transfer coefficient, and a low thermal expansion coefficient.

Various synthetic materials having an alpha particle emission rate of less than about 0.005 curie / hour / square centimeter and a thermal conductivity greater than about 1 watt / m ° K can be used. Examples are boron nitride, silicon carbide, aluminum nitride and beryllium oxide. Aluminum nitride (AlN) is particularly suitable. This preferred high purity synthetic AlN has an alpha particle emission rate of less than about 0.005 curie / hour / square centimeter and about 200 watt / m 2.
It has a thermal conductivity of more than ° K.

The thermally conductive filler for synthesis is a spherical particle, having a diameter of, for example, about 0.1 to about 40 microns. Alternatively, the filler has a length of about 0.1 to about 40 microns, a diameter of about 0.1 to 40 microns, and an aspect ratio (diameter / length ratio) of about 1: 1 to about 0.025:
It may be one acicular particle. Suitable AlN materials are about 0.1 to about 10 microns in length and about 0.1 to 10 in diameter.
It is a needle having a micron and an aspect ratio (diameter / length ratio) of about 1: 1 to about 0.1: 1.

When the particles are thermally or electrically or both conductive, they are encapsulated by coating them with an emulsion or colloidal dispersion of polyfluorocarbon. The emulsion generally contains from about 1 to about 50 weight percent polyfluorocarbon particles. The polyfluorocarbon particles have a diameter of about 0.1 to about 29 microns. These particles are dispersed in a solvent together with, for example, a surfactant and a dispersant. An example of a solvent is 0.1% dispersant.
Deionized water containing 10 to 10 weight percent. The dispersion and filler particles are thoroughly mixed using, for example, ultrasonic agitation of the emulsion.

The resulting dispersion of heat conductor particles and polytetraethylene is generally about 0.1 to about 60 parts by weight, preferably about 0.1 to 9 to 10 parts by weight per part by weight of the organic fluorocarbon. Contains parts by weight of filler.

The filler is dispersed throughout the polymer. This dispersity and the relative particle size of the dispersed filler and the encapsulated polymer are such that the coefficient of thermal expansion is smaller than that of the neat polymer and the coefficient of heat transfer is greater than that of the neat polymer. Is. In the case of conductive fillers, individual filler particles must be encapsulated in fluorocarbon resin to avoid percolation mode conduction.

In a further embodiment of the invention, the synthetic conductor particles are encapsulated in an encapsulant to prepare the dielectric. This is shown in the flow chart of FIG. 2. Provide synthetic conductor particles according to the method shown in block 1 of FIG.

The particles are coated with an emulsion or colloidal dispersion of polyfluorocarbon. This is indicated by block 2 in FIG. In one preferred embodiment, the colloidal dispersion contains from about 10 to about 60 weight percent of 0.1 to about 2.0 micron polytetrafluoroethylene particles in water containing the dispersant.

The resulting dispersion of conductor particles and polyfluorocarbon is either applied to the polyfluorocarbon sheet or placed between the polyfluorocarbon sheets, as shown in block 3 of FIG. The coated sheet is then heated to remove volatiles, as shown in block 4 of FIG. This curing or drying step is typically performed at temperatures above about 250 ° C. to drive off the volatiles of the polymer without inconvenient sintering. The resulting encapsulated particles have a structure as conceptually shown in FIG. As shown, the AlN particles are encapsulated in polytetrafluoroethylene particles.

Next, this material is sintered, as shown in block 5 of FIG. This sintering forms the dielectric of the present invention, as is well known in the polytetrafluoroethylene art.

The polymer dielectric was prepared by encapsulating acicular synthetic AlN (aluminum nitride) conductor particles in an encapsulant. The particles are about 0.1 to 10 microns long and about 0.1 to about 10 microns in diameter. The particles contain less than 1.0 ppm of impurities.

The conductor particles were coated and encapsulated with a polyfluorocarbon emulsion or colloidal dispersion.
The emulsion contained 10 to 50 weight percent 0.1 to 10 micron diameter polytetrafluoroethylene particles in deionized water containing 0.1 to 10 weight percent dispersant. The dispersion and particles were mixed.
The coating was applied to AlN fibers using ultrasonic agitation of the emulsion.

The resulting dispersion of conductor particles and polytetrafluoroethylene contained 3 parts by weight of organic material with respect to 2 parts by weight of filler. This dispersion has a thickness of 76
It was applied to a micrometer (3 mil) polytetrafluoroethylene sheet. The sheet was heated to 300 ° C. for 30 minutes to drive off the solvent. Then, the two-layer coating film was laminated at 327 ° C. for 30 minutes to form the dielectric material of the present invention.

The dimensional change of this dielectric was tested as a function of temperature and compared to plain polytetrafluoroethylene. The dimension versus temperature of the filled material of the present invention is shown in FIG. 5, and the dimension change versus temperature of polytetrafluoroethylene of the same dimension is shown in FIG. It is noted that the dielectrics prepared using the method of the present invention have a significantly lower coefficient of thermal expansion.

[0052]

That is, the microelectronic circuit package and its manufacturing method of the present invention provide a microelectronic circuit package having a high circuit density. This package features a low dielectric constant, a lower coefficient of thermal expansion than the neat polyfluorocarbon, a higher coefficient of thermal diffusion than the neat polyfluorocarbon, and a low alpha particle emission rate. The composite dielectric of the present invention has a low coefficient of thermal expansion, eg, about 126.8 micrometers / m ° C. at 32.2 ° C.
Less than about 113.4 micrometers at 146.3 ° C /
It has a coefficient of thermal expansion of less than m ° C. This composite dielectric is further characterized by a high thermal diffusion coefficient. Furthermore, the composite dielectric of the present invention has a low alpha particle emission rate. This low alpha particle emission rate, eg, at least about 0.005 curie / hour-less than a square centimeter, is particularly advantageous for high storage density circuit packages for high storage density MOS storage chips.

The above and other advantages of this composite dielectric are believed to be based on the synergy of the polyfluorocarbon resin and the encapsulated low alpha particle emission rate thermal and electrical conductors dispersed therein. Be done.

[Brief description of drawings]

FIG. 1 is a perspective view in which a part of an electronic circuit package embodying a composite dielectric of the present invention is cut out.

FIG. 2 is a flow diagram of one method of implementing the method of the present invention.

FIG. 3 is a diagram illustrating filler particles encapsulated within uncured polyperfluorocarbon particles.

FIG. 4 represents encapsulated filler particles between two sheets of polyperfluorocarbon material.

FIG. 5 is a graph plotting the change in length of a filled composite material of the present invention as a function of temperature, with point values for the coefficient of thermal expansion noted on the graph.

FIG. 6 is a graph plotting the length change of an unfilled composite of the prior art as a function of temperature, the point value of the coefficient of thermal expansion being noted in the graph.

[Explanation of symbols]

 1 Package 11 Card 21 Polymer Dielectric 51 Integrated Circuit Chip

Claims (12)

[Claims] 1. A microelectronic circuit package comprising an integrated circuit mounted on a circuit card with electrical connections for signal, power and ground therebetween, said circuit comprising: a. A perfluorocarbon polymer; and b. Formed of a filled polymer dielectric containing a synthetic inorganic filler having a low alpha particle emission rate, a high coefficient of heat transfer and a low coefficient of thermal expansion dispersed throughout the polymer; A microelectronic circuit package having a lower coefficient of thermal expansion than the polymer and a higher coefficient of heat transfer than the polymer. 2. The microelectronic circuit package of claim 1, wherein the perfluorocarbon comprises polytetrafluoroethylene. 3. The microelectronic circuit package of claim 1, wherein the synthetic inorganic filler comprises AlN. 4. The microelectronic circuit package of claim 1, wherein the perfluorocarbon comprises polytetrafluoroethylene and the synthetic inorganic filler comprises AlN. 5. The microelectronic circuit package according to claim 1, wherein the synthetic inorganic filler is a granular filler, and individual filler particles are enclosed in a perfluorocarbon resin. 6. A step of providing thermally and electrically conductive particles; contacting the particles with a polyfluorocarbon resin dispersed in a solvent to form a filler particle composite coated with the polyfluorocarbon resin in a solvent. Forming therein; applying a composite of filler particles coated with a polyfluorocarbon resin contained in a solvent to one or more polyfluorocarbon sheets; heating the sheet and the polyfluorocarbon resin filler particles to form a solvent And heating the dried sheet and the polyfluorocarbon resin coated filler particles to fuse the particles and sheet to form a filled polyfluorocarbon dielectric composite. Method for producing a polyfluorocarbon dielectric composite. 7. The method of claim 6, wherein the filler is electrically and thermally conductive. 8. A group of polyfluorocarbon resins dispersed in a solvent consisting of polymers and copolymers of tetrafluoroethylene, perfluoropropylene, perfluoroethers, vinyl fluoride, vinylidene fluoride, chlorotrifluoroethylene and mixtures thereof. 7. The method of claim 6 selected from 9. The polyfluorocarbon sheet comprises tetrafluoroethylene, perfluoropropylene, perfluoroethers, vinyl fluoride, vinylidene fluoride,
7. The selected from the group consisting of polymers and copolymers of chlorotrifluoroethylene and mixtures thereof.
the method of. 10. The method of claim 6 wherein the weight ratio of filler to total fluorocarbon is from about 0.1 to about 9.0. 11. The method of claim 6 wherein the composite dielectric has a higher thermal conductivity than pure polyfluorocarbon. 12. The composite dielectric material has a lower coefficient of thermal expansion than the neat polyfluorocarbon.
the method of.