JPH05198904A - Fluoropolymer filled with ceramic in low content - Google Patents

Abstract

PURPOSE: To provide a fluoropolymer composite material, which is especially suitable for usage of joint layer in a multilayered circuit and other electronic circuits in which superior thermal, mechanical and electrical characteristic as well as fluidity are required. CONSTITUTION: This material comprises a ceramic (e.g. silica) filled fluoropolymer (e.g. polytetrafluoroethyene), and the ceramic is covered with a zirconate coupling agent (e.g. neopentyl (diaryloxy) tri (dioctyl) pyrophosphate zirconate) and/or titanate coupling agent (e.g. neopenyl (diaryl) oxytrineodecanonyltitanate), and the volume percent of ceramic therein is about 26 to 50%.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to fluoropolymer composite materials. More specifically, the present invention is particularly suitable for use as a tie layer in multilayer circuit boards and other electronic circuits that need to have flowability and excellent thermal, mechanical and electrical properties. It relates to a polymer composite material. The fluoropolymer composites of the present invention are also resistant to chemical degradation, especially in high pH (alkaline) environments.

[0002]

U.S. Pat. No. 4,849,284, assigned to the Applicant, describes electrical substrate materials based on ceramic-filled fluoropolymers. The material is Rogers Corpo
marketed under the trademark RO-2800. This electrical substrate material preferably comprises silica filled polytetrafluoroethylene with a small amount of fine glass fibers. An important feature of this material is that the ceramic filler (silica) is coated with a silane coating material which imparts hydrophobicity to the ceramic surface and improves its tensile strength, peel strength and dimensional stability. When the composite material of US Pat. No. 4,849,284 is used as a circuit board or tie layer, the volume fraction of filler in the composite material is 50% or more without voids.

The ceramic-filled fluoropolymer-based electrical substrate materials of US Pat. No. 4,849,284 are very suitable substrate materials for forming rigid printed wiring boards and other materials used in forming printed wiring boards. Shows improved electrical performance compared to. The electrical substrate material also has a low coefficient of thermal expansion and flexibility, so that it has a certain degree of surface fixation and a plated through-hole.
The certainty of the hole) is also improved. Individual sheets of this electrical substrate material can be laminated by known methods to form a multilayer circuit board. In fact, it was disclosed in US Pat. No. 4,849,284 (Rogers Corporation).
A thin film-like product made from the material (commercially available under the trademark RO-2810 from R.S.A.) can be used as a bonding layer to bond a plurality of laminated substrate layers together to form a multilayer circuit board.

Ceramic filler (55% by volume or more)
Inclusion of high volume fractions significantly degrades the rheology (eg, flowability) of ceramic-filled fluoropolymer composites. This effect cannot be neglected when the composite material is used as a bonding film or for opening filling of originally rigid structures. Materials containing 50-55% volume fraction of ceramic filler have significantly improved their rheological properties compared to materials containing higher volume fractions of filler. However, in the case of fluoropolymer composites, it must be possible to provide good flowability, while at the same time the good thermal, mechanical and electrical properties must not be significantly reduced.

Fluoropolymer composite materials containing a volume fraction of ceramic material above 50% not only have their rheological properties worsened, but also to some adverse environments, especially high pH (alkaline) baths. Chemical resistance is also decreasing. However, such high pH baths (eg pH = 12 and above) must be used in electroless copper plating, which is often used as a highly preferred processing method in the manufacture of fine line circuit components (eg multi-chip modules). It has been found that high levels (50% or more by volume) of ceramic fillers impair the chemical resistance of fluoropolymer circuit materials that have been in prolonged contact with alkaline baths. Deterioration occurs as a result of the reduced resistance to alkaline baths, which reduces the hydrophobicity of the fluoropolymer composite, which in turn increases its hygroscopicity, and correspondingly the electrical properties of the composite circuit material. Is reduced.

US Pat. No. 5,061,548 (assigned to the Applicant) discloses a ceramic filler content (with a silane coating) disclosed in US Pat. No. 4,849,284 as low as 45% by volume without voids. However, it is disclosed that the composite material retains suitable thermal, mechanical and electrical properties that enable it to be used as a bonding layer in multilayer circuit materials and as a filling material for certain rigid structures. ing. The ceramic-filled fluoropolymer composite of US Pat. No. 5,061,548 is described in US Pat.
It has an improved rheology as compared to material No. 84, allowing access holes and structures to be filled with resin flow without unduly increasing the material's z-axis coefficient of thermal expansion (CTE). ..

US Pat. No. 5,024,871 (assigned to the applicant) discloses a silane coating of a ceramic filler of an electrical substrate material disclosed in US Pat. No. 4,849,284 with a zirconate coupling agent and / or a titanate cup. It is disclosed that the resulting composite material retains the same excellent thermal, mechanical and electrical properties as the material described in U.S. Pat. No. 4,849,284 when replaced with a ring agent.

[0008]

SUMMARY OF THE INVENTION The inventor has found that high filler content (eg, 50% or more) fluoropolymer composites disclosed in US Pat. No. 4,849,284 occur when exposed to high pH baths for extended periods of time. It has been found that significant chemical degradation can be reduced and / or mitigated by using filler levels as low as about 26% by volume without voids. When the ceramic is coated with a titanate and / or zirconate coating, the resulting ceramic-filled composite material has excellent mechanical and electrical properties,
Significantly improved alkali resistance (compared to higher filler level composites). Accordingly, the present invention provides a ceramic-filled fluoropolymer composite material containing a titanate and / or zirconate coated ceramic in a proportion of 26-50% by volume.

[0009]

The above and other features and advantages of the present invention include:
Those skilled in the art will readily understand from the following detailed description based on the drawings.

The ceramic-filled fluoropolymer composite material of the present invention has a ceramic content of about 26% by volume without voids.
US Pat. No. 4 except that it is present in small amounts
No. 849284, No. 5061548 and No. 50248
Substantially similar to the composite material described in No. 71.

The first embodiment of the present invention is present with a particulate ceramic filler present in a volume fraction of about 0.26 to 0.50 without voids, and also in a volume fraction of 0.74 to 0.50. A composite material consisting of a fluoropolymer (eg PTFE) is shown as a preferred embodiment. The preferred ceramic filler is fused amorphous silica, but other particulate siliceous fillers such as sand and clay may also be used. In addition, reinforcing materials such as glass fibers, solid glass beads and crushed glass panels may be used in amounts up to 2% by weight. The ceramic filler is coated with a titanate and / or zirconate coating. All other compositional features and manufacturing methods are the same as in US Pat. No. 4,849,284. Therefore, for details thereof, see US Pat.
See No. 84. The material of the present invention may be prepared by wet mixing, in which the ceramic filler is dispersed and solidified in the PTFE polymer, or may be prepared by dry mixing of the PTFE fine powder and the ceramic filler.

Non-limiting examples of suitable zirconate coupling agents are neopentyl (diallyloxy) tri (dioctyl) pyro-phosphate zirconate and neopentyl (diallyloxy) tri (N-ethylenediamino) ethyl zirconate. The latter zirconate is Ke
nrich Petrochemicals, Inc.
Under the trademark LZ-44.

Examples of suitable titanate coupling agents are:
Neopentyl (diallyl) oxytrineodecanonyl titanate, neopentyl (diallyl) oxytri (dodecyl) benzene-sulfonyl titanate, neopentyl (diallyl) oxytri (dioctyl) phosphatotitanate, neopentyl (diallyl) oxytri (dioctyl) pyro-phosphatotitanate, Neopentyl (diallyl) oxytri (N-ethylenediamino) ethyl titanate, neopentyl (diallyl) oxytri (m-
Amino) phenyl titanate and neopentyl (diallyl) oxytrihydroxycaproyl titanate. All of these titanates are from Kenrich P
Trademark LIC from etrochemicals, Inc.
It is marketed as A.

The preferred zirconate and titanate coating that achieves the important features of the electrical substrate materials of the present invention is 1% by weight of the filler (ceramic) material.

By reducing the filler content to values as low as about 26% by volume, the fluoropolymer composite's resistance to alkaline environments is significantly enhanced. Such enhanced resistance to alkaline environments is described in detail in USSN 641427 filed Jan. 17, 1991 (assigned to the applicant) in connection with silane coatings. As in the above-referenced US Pat. No. 5,024,871, zirconate and titanate coatings will give results close to, if not equal to, silane. Thus, the titanate and / or zirconate coated ceramic filled fluoropolymers of the present invention will exhibit the same or similar properties as the silane coated composites.

Low filler levels according to the invention (eg 27
˜37% by volume) significantly enhances chemical resistance compared to the 50% by volume level of the composite of US Pat. No. 4,849,284. Thus, the filled fluoropolymer composite material of the present invention having a filler level of about 26 to 50% by volume is a significant circuit material advantage over the material of US Pat. No. 4,849,284 (at or above 50% by volume filler level). ..

By reducing the filler content in this manner, the material of the present invention has improved rheology and becomes "flowable", and high filler levels (volume fraction 55) as disclosed in US Pat. No. 4,849,284. % Or more) of material allows the filling of relatively large openings in thick metal foils or inner layers of circuits.

An important feature of the present invention is that the rheology is improved without unduly increasing the z-axis coefficient of thermal expansion (CTE) of the material. The z-axis coefficient of thermal expansion of a product containing 30 to 50% by volume of filler is -55 to +12.
In the temperature range of 0 ° C, much lower than the widely used fiber reinforced PTFE (typically about 200 pp
m / ° C.). A multilayer circuit board comprising a tie layer of the present invention and a RO2800 laminate joined by the layer,
It showed a much lower coefficient of thermal expansion than the fiber reinforced PTFE plate. Such a reduction in coefficient of thermal expansion provides the important advantage of increasing the reliability of the coating of through holes and vias for heating cycles and high temperature assembly.

The present invention may be used in a number of applications where ceramic-filled PTFE composites produce useful printed wiring boards. The invention is particularly applicable to etched C
Used to fill openings in originally rigid structures, such as IC voltage or ground planes, or to secure cores or circuit components that are coupled to such structures. For example, FIG. 1A shows a cross-sectional view of a rigid ground plane structure 50 having a plurality of apertures 52. Sheet 5 of the present invention
4, 56 (for example, a ceramic having a volume fraction of about 0.26 to 0.50) are arranged on both sides of the ground plane 50. In FIG. 1B, the laminate 58 of FIG. 1A is laminated under heat and pressure. The composition of the present invention has sufficient fluidity so that it can completely fill the apertures and still provide excellent thermal, mechanical and electrical properties.

Further according to FIG. 2, the composite material of the present invention is processed into the form of a sheet which has not been densified and sintered and is used for bonding multilayer printed wiring boards, or It can be used to manufacture printed wiring boards by laminating foils. In FIG. 2, the multilayer circuit board as a whole is indicated by reference numeral 10. Multilayer board 1
0 comprises a plurality of substrate material layers 12, 14 and 16, all of which are electrical substrate materials, preferably US Pat.
No. 849284, No. 5061548, No. 502487
No. 1 or USSN 641427 ceramic-filled fluoropolymer material. Each substrate layer 12, 14 and 16 has a conductive pattern 18, 20, 22 and 24 respectively. Note that the substrate layer carrying the circuit pattern shapes the circuit board. Covered hole 2
6, 28 interconnect the selected circuit patterns in a known manner.

According to the present invention, separate sheets 30, 32 of substrate material having the composition of the present invention are used as adhesive or tie layers to bond individual circuit boards together. A preferred method of forming such a laminate results in a laminate of circuit boards alternating with one or more tie layers. The laminate is then fused. That is, the entire multi-layer assembly is melted and fused such that the entire interior is a homogeneous structure with constant electrical and mechanical properties. Tie layers 30 and 3 for laminating circuit boards made of materials other than fluoropolymer filled ceramics coated with silane, titanate and / or zirconate
Note that 2 can be used. However, in a preferred embodiment, the circuit board of the multilayer circuit board consists only of the ceramic-filled fluoropolymer electrical board material.

Composite materials containing high levels (eg, 50% or more by volume) of fillers, such as those described in US Pat. No. 4,849,284, are used in printed wiring boards of various designs (eg, large multi-layer boards for host computers). (CPU board), military surface mount assembly, microwave circuit board bond assembly). However, when a voltage surface that is thicker than the thickness of the dielectric is required, especially when used for MLB (for example, when using a thick power surface for controlling thermal expansion coefficient and a thick control layer),
In order to provide suitable fluidity, as shown in the above-mentioned U.S. Pat. No. 5,061,548, the filler content (from 45 to
It is necessary to reduce (to 50% by volume). Materials with low filler content of about 26-50% according to the present invention can accommodate the development of circuit processing technology for multichip module manufacturing. Especially in the manufacture of such multi-chip modules, laser drills are used to provide small openings and also require good flowability and alkali resistance to electroless baths. With the low filler content of the present invention (such as the materials described in US Pat. No. 4,849,284)
While it may not be possible to produce excellent conventional multilayer boards, the materials described in US Pat. No. 4,849,284 are not suitable for multi-chip modules that have emerged as the preferred packaging technology for high speed, high density designs.

The preferred embodiments of the present invention have been described above with reference to the drawings. However, it should be understood that many modifications and substitutions can be made without departing from the spirit and scope of the present invention, and that the description in the text is a representative and non-limiting description of the present invention.

[Brief description of drawings]

FIG. 1A is an elevational cross-sectional view of a rigid structure having apertures before filling with a composite material of the present invention and B after filling.

FIG. 2 is an elevational cross-sectional view of a multilayer circuit board using the thermoplastic composite material of the present invention as a film-like bonding layer.

[Explanation of symbols]

 10 Multilayer Circuit Board 12, 14, 16 Substrate Material Layer 18, 20, 22, 24 Conductive Pattern 26, 28 Coated Through Hole 30, 32 Bonding Layer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number FI Technical display location C08L 27/12 9166-4J (72) Inventor Guo S Suway USA, Masachi Yousets 01532, Northborough, Valentin Rod 60 (72) Inventor Allen F Horn the Third United States, Connecticut 06239, Danielson, Broad Street 95 (72) Inventor Brett Kirheny United States, Connecticut 06268, Stores, Sheaday Lane 25

Claims (17)

[Claims] 1. A fluoropolymer material and a ceramic filler material, wherein the filler material comprises about 2% of the total substrate material.
An electrical substrate material, characterized in that it is present in an amount of 6 to 50% by volume or more and the ceramic filler is coated with a zirconate or titanate coating. 2. Material according to claim 1, characterized in that at least one layer of electrically conductive material is arranged on at least part of the electrical substrate material. 3. The material of claim 1, wherein the fluoropolymer material is selected from the group consisting of polytetrafluoroethylene, hexafluoropropene, tetrafluoroethylene or perfluoroalkyl vinyl ether. 4. The material of claim 1, wherein the ceramic filler comprises silica. 5. The zirconate coating comprises neopentyl (diallyloxy) tri (dioctyl) pyro-phosphate zirconate and neopentyl (diallyloxy).
A material selected from the group consisting of tri (N-ethylenediamino) ethyl zirconate.
The material described in. 6. The titanate coating comprises neopentyl (diallyl) oxytrineodecanonyl titanate, neopentyl (diallyl) oxytri (dodecyl) benzene-sulfonyl titanate, neopentyl (diallyl).
Oxytri (dioctyl) phosphatotitanate, neopentyl (diallyl) oxytri (dioctyl) pyro-
Selected from the group consisting of phosphatotitanate, neopentyl (diallyl) oxytri (N-ethylenediamino) ethyl titanate, neopentyl (diallyl) oxytri (m-amino) phenyl titanate, and neopentyl (diallyl) oxytrihydroxycaproyl titanate. Material according to claim 1, characterized in that 7. In a multilayer circuit including at least a first circuit layer and a second circuit layer, an adhesive layer is sandwiched between the first circuit layer and the second circuit layer, and the adhesive layer is fluoro. Comprising a polymeric material and a ceramic filler material, said filler material being present in an amount of greater than or equal to about 26-50% by volume of the total adhesive layer, said ceramic filler being coated with a titanate or zirconate coating. Characteristic multi-layer circuit. 8. The multilayer circuit according to claim 7, which has at least one covering hole. 9. The multilayer circuit of claim 7, wherein the fluoropolymer material is selected from the group consisting of polytetrafluoroethylene, hexafluoropropene, tetrafluoroethylene or perfluoroalkyl vinyl ether. 10. The multilayer circuit of claim 7, wherein the ceramic filler comprises silica. 11. The zirconate coating is selected from the group consisting of neopentyl (diallyloxy) tri (dioctyl) pyro-phosphate zirconate and neopentyl (diallyloxy) tri (N-ethylenediamino) ethyl zirconate. The multilayer circuit according to claim 7. 12. The titanate coating comprises neopentyl (diallyl) oxytrineododecanoyl titanate,
Neopentyl (diallyl) oxytri (dodecyl) benzene-sulfonyl titanate, neopentyl (diallyl) oxytri (dioctyl) phosphatotitanate,
Neopentyl (diallyl) oxytri (dioctyl) pyro-phosphatotitanate, neopentyl (diallyl)
8. A compound selected from the group consisting of oxytri (N-ethylenediamino) ethyl titanate, neopentyl (diallyl) oxytri (m-amino) phenyl titanate, and neopentyl (diallyl) oxytrihydroxycaproyl titanate. The described multilayer circuit. 13. A rigid substrate having at least one aperture at least partially penetrating the substrate, and a composite material in the at least one aperture, the composite material comprising:
A fluoropolymer material and a ceramic filler material, said ceramic filler material comprising about 26% of the total composite material.
A product, characterized in that it is present in an amount of ˜50% by volume or more and the ceramic filler is coated with a titanate or zirconate coating. 14. A product as set forth in claim 13 wherein said fluoropolymer material is selected from the group consisting of polytetrafluoroethylene, hexafluoropropene, tetrafluoroethylene or perfluoroalkyl vinyl ethers. 15. A product as set forth in claim 13 wherein the ceramic filler comprises silica. 16. The zirconate coating is selected from the group consisting of neopentyl (diallyloxy) tri (dioctyl) pyro-phosphate zirconate and neopentyl (diallyloxy) tri (N-ethylenediamino) ethyl zirconate. The product according to claim 13. 17. The titanate coating comprises neopentyl (diallyl) oxytrineodecanonyl titanate, neopentyl (diallyl) oxytri (dodecyl) benzene-sulfonyl titanate, neopentyl (diallyl).
Oxytri (dioctyl) phosphatotitanate, neopentyl (diallyl) oxytri (dioctyl) pyro-
Selected from the group consisting of phosphatotitanate, neopentyl (diallyl) oxytri (N-ethylenediamino) ethyl titanate, neopentyl (diallyl) oxytri (m-amino) phenyl titanate, and neopentyl (diallyl) oxytrihydroxycaproyl titanate. The product according to claim 13, characterized in that