JP3409066B2 - Fluoropolymer composites filled with low volume fraction ceramic - Google Patents

Description

Detailed Description of the Invention Correlation with Related Patent Applications This application is US patent application No. 3 filed June 10, 1989.
67,241, which is a continuation-in-part application of U.S. Patent Application No. 015,191, filed February 17, 1987, and currently U.S. Pat. No. 4,849,284.
U.S. Patent Application No. 279,4 filed Dec. 2, 88
This is a priority claim application based on a part continuation application with No. 74.

BACKGROUND OF THE INVENTION The present invention relates to fluoropolymer composite materials. More particularly, the present invention is particularly well suited for use as a tie layer in multi-layer circuits and as a tie layer in other electrical circuit applications that require fluidity and good thermal, mechanical and electrical properties. Fluoropolymer composite material. The fluoropolymer composites of the present invention also exhibit resistance to chemical degradation, especially high pH (alkaline) environments. U.S. Pat. No. 4,849,284, assigned to the assignee and incorporated herein by reference, is Rogers Cor.
describes a ceramic-filled fluoropolymer based electrical support material sold under the trademark RO-2800 by Poration. The electrical support material preferably comprises silica-filled polytetrafluoroethylene with a small amount of microfiberglass. An important feature of this material is that it is applied to the ceramic filler (silica) with a silane coating material, which makes the surface of the ceramic hydrophobic and provides improved tensile strength, peel strength and dimensional stability. . U.S. Pat. No. 4,84
The 9,284 composite discloses that at least 50% by volume (by volume excluding voids or voids) of filler is disclosed for use as a circuit support or tie layer. The ceramic-filled fluoropolymer-based electrical support material of US Pat. No. 4,849,284 is highly suitable for forming rigid printed wiring board support materials and provides superior electrical performance over other printed wiring boards. Show. Similarly, the low coefficient of thermal expansion and compliance characteristics of this electrical support material improves surface mount reliability and plated through hole reliability. As is known, the individual sheets of electrical support material can be stacked to form a multilayer circuit board.
In fact, a thin film formulation of the material disclosed in US Pat. No. 4,849,284 (and sold by Rogers Corporation under the trademark RO-2810) is used as a tie layer to form a multilayer circuit board. Multiple stacked support layers can be bonded together. It will be appreciated that the high volume fraction of the ceramic filler (greater than 55% by volume) significantly and adversely affects the rheology (eg, flowability) of the ceramic-filled fluoropolymer composite. This is especially important when the composite is used as a bonding film or to fill an opening that was initially rigid in structure. Ceramic filler volume fractions of 50-55% result in significantly improved rheological properties compared to higher filler fractions, but with appreciable modification of excellent thermal, mechanical and electrical properties. Instead, it feels necessary to provide much better flow characteristics. 50% besides adverse effects on rheology
It was also concluded that the above ceramic filler volume fractions adversely affect the chemical resistance of the filled fluoropolymer composites with respect to certain adverse environments, especially high pH (alkaline) baths. Such a high pH bath (eg p
H = greater than 12) is required for electroless copper deposition, which is fine line circuit.
This is a very desirable and often used method for the manufacture of try (ie multi-chip modules). It has been found that high fractions (50% or more by volume) of ceramic fillers can degrade the chemical resistance of fluoropolymer circuit materials during long-term exposure in such alkaline baths. The degradation caused by the low resistance to alkaline baths results in a decrease in the hydrophobicity of the fluoropolymer composite. In turn, this reduction results in an increase in hygroscopicity, with a corresponding, highly undesirable reduction in the electrical properties of the composite circuit material.

SUMMARY OF THE INVENTION US Patent Application No. 367,241 (filed June 16, 1989) (assigned to the applicant,
Incorporated herein by reference in its entirety), U.S. Pat. No. 4,849,2.
The ceramic filler content of the material disclosed in No. 84 can be as low as 45% by volume, excluding porosity. Nevertheless, it retains sufficient thermal, mechanical and electrical properties and can be used as a bonding layer for multilayer circuit materials and as a filling material for certain rigid structures. The ceramic-filled fluoropolymer composite of U.S. Patent Application No. 367,241 has improved rheology as compared to the U.S. Pat. No. 4,849,284 material and provides access holes and Z-axis CTE of the material. Feature flow with resin flow without extra growth
It is useful for applications that require lining). For long exposure to high pH baths US Pat. No. 4,849,28
The significant chemical degradation that results in fluoropolymer composites with high filler content of # 4 (eg, 50% or greater) is:
It has now been discovered by the present invention that reduction and / or mitigation can be achieved by having a low filler level as low as about 26% by volume, excluding porosity. The resulting ceramic-filled composite has excellent mechanical and electrical properties and exhibits a marked improvement in alkali resistance (for high filler loading composites).
Accordingly, the present invention relates to a filled fluoropolymer composite containing 26-45% by volume silane coated ceramic. Another important feature of the invention is that relatively large amounts of silane coatings (up to 2-10% of the total weight of the ceramic filler) of silane, especially plated through-holes and solid post vias.
It has been found to result in improved performance with respect to laser drilling to form a. 10%
The use of coating layers (preferably 6%) was incredible and unexpected. This is because it was generally believed that the amount of silane had to be 1-2%, and that high amounts up to 6-10% did not provide a clear improvement (US Pat. No. 4,849,284). As stated in the issue).
A preferred silane coating layer comprises a blend of phenylsilane and fluorosilane. This combination imparts chemical resistance to alkaline baths and further enhances the ability of laser drilling. Similarly, the combination of the relatively inexpensive phenylsilane and the expensive fluorosilane provides a highly economically effective coating. Those skilled in the art will appreciate and appreciate the above discussed features and advantages of the present invention from the following detailed description and drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The ceramic-filled fluoropolymer composite of the present invention comprises (1) about 26% by volume of ceramic in the first embodiment, based on volume excluding voids.
US, except that it is present in a minor amount, and (2) in the second embodiment, the ceramic filler is applied at 10% or less (based on the total weight of the ceramic filler) of silane. It is essentially similar to the composites described in U.S. Pat. No. 4,849,284 and U.S. patent application Ser. No. 367,241, both of which are fully incorporated herein by reference. In all of these embodiments, it is preferred to utilize a mixture of phenylsilane and fluorosilane to apply the ceramic filler. A preferred embodiment, the first embodiment of the present invention, comprises a specific ceramic filler present in an amount of about 0.26 to less than 0.45 by volume (void-free volume basis), It is composed of a composite material with a fluoropolymer (for example, PTFE) present at 74 to 0.55 parts by volume. The preferred ceramic filler is fused amorphous silica. All other structural aspects and methods of preparation are described in US Pat. No. 4,849,284 (silane coated except for the preferred high weight percent silane coating and the preferred silane blends described herein together. (Including ceramic). Therefore,
The details of U.S. Pat. No. 4,849,284 are applicable. The materials of the present invention are "wet blended" with PTFE polymer in dispersion with ceramic fillers and coagulants or PTFE.
Can be prepared by dry blending the fine powder with the ceramic filler. Reducing the filler content down to about 26% by volume is significant because it increases the resistance of the fluoropolymer composite to alkaline conditions. Comparing Examples 1 and 2 shown in Table 1 below, Example 1 shows that 50% PTFE fluoropolymer, 50% silica filler and 2% by weight phenylsilane filler coating.
Is a composite of the type described in U.S. Pat. No. 4,849,284 having the composition Example 2 is 37.1% silica filler and 62.9% PTFE fluoropolymer.
And 6% by weight (relative to the total weight of the filler) of a blend of phenyl and fluoro-silane (3: 1 ratio) as a composition.

[Table 1] The results in Table 1 show that the amount of filler is reduced (eg US Pat.
0.07 of the present invention for 1.7% of 49,284 materials
%) Clearly shows a significant decrease in H ₂ O absorption (after treatment in alkaline bath). It is found that the acceptable H ₂ O absorption is less than about 0.1%. The results in Table 1 are further substantiated in Examples 3-12 in Table 2. In Examples 6-11, the silane coating consisted of a blend of phenylsilane and fluorosilane. Example 12 utilizes a phenylsilane coating.

[Table 2] Table 2 shows the decrease in filler content at high pH, as evidenced by the decrease in water absorption with decreasing filler content.
It is again shown to result in increased chemical resistance to processing. A comparison of examples having equivalent silane coatings (eg Examples 3-5, 6-8 and 9-11)
At least 1 part shows that lowering the amount of filler increases the chemical resistance. With low amounts (eg 27 and 37% by volume) as in the present invention, US Pat.
It is understood that a significant improvement is achieved over the 50% by volume level properties associated with the 849,284 composite material.
So about 26% by volume (about 26% in Tables 3 and 4
Note that examples having filler contents up to 4% by volume are described) and filled fluoropolymer circuit material composites of the present invention having a filler amount of less than 45% by volume are available in the United States. Patent Application No. 367,241 (filler amount of 45% to less than 50% by volume) and US Pat.
849,284 (filler amount of 50% by volume or more) offers significant advantages over both materials. Yet another feature of the present invention is that the total amount of ceramic filler is 10
High filler amounts up to wt% (preferably 6 wt%)
It has been found to contribute to improving the performance of laser ablation. This finding was found in US Pat.
No. 49,284, a silane coating amount of 1 to 2% was preferable, and at 2% or more, the effect on the silane coating was considered to be neglected and suggested, and thus was not expected. The two criteria used to determine the laser processability of circuit materials are (1) the amount of energy required for ablation (a lower amount is preferred) and (2) a perfectly ablated (non-tapered) hole. From the inner wall surface (preferably 0 °). FIG. 4 shows a substrate 4 having a copper layer 6 thereon.
Figure 2 shows a cross section of a circuit board with laser melting holes 2 formed (made of the composite material of the invention). Corner "a"
Represents the sway from a straight wall. Tables 3 and 4
Shows the results of laser ablation for coating and ceramic filler data for dry and wet blended compositions. Examples 13-30
And Examples 32-38 use a silica filler,
Examples 31 and 39 use a quartz filler.

[Table 3]

[Table 4] The results in Tables 3 and 4 show that high filler loading and high coating loading give the best laser ablation performance (represented by the lowest ablation energy limit). The performance of laser ablation deteriorates when either the amount of filler or the amount of coating, or both, decreases. The filler coating can significantly reduce the abrasion limit, even for filler amounts as low as 26%. This means that Examples 18 and 20 are combined with Example 36.
Very obvious when compared to. In Tables 3 and 4, the coating represented by the ratio 3: 1 is 3 parts phenylsilane to 1 part fluorosilane. The coating identified as 6124 is phenylitrimethoxysilane, the fluorosilane is tridecafluoro-1,1,2,2-tetrahydrooctyl-1-triethoxysilane, and C ₆ F ₁₃ CH ₂ CH ₂ Si. (OCH ₂ CH ₃ ) ₃
And has the chemical formula of C ₆ F. Laser processability (at 248 mm, beam energy, 3.
The effect of the composition on the case of 9 J / cm ² ) is also shown in FIG. The diagonal lines represent the deviation from the straight line of the wall surface of the hole irradiated with the laser (the lower the angle is preferable). In FIG. 3, “silica filler amount” includes the volume percent contributed by the silane coating. It is pointed out from FIG. 3 that higher silane content and / or higher ceramic filter content leads to improved laser ablation (quality of the inner wall of the hole). Note that it is preferable to use high amounts of silane for low amounts of ceramic filler.
As a further feature of the present invention, it has been found that a blend of phenylsilane and fluorosilane is preferred for the silane coating. Fluorosilanes provide chemical resistance to alkaline exposure, while phenylsilanes facilitate laser drilling and are less expensive than fluorosilanes. Table 5 illustrates the superiority of fluorosilane over phenylisilane in the case of imparting resistance to alkali and alkali deterioration. A preferred blend has a 3: 1 weight ratio of phenylsilane to fluorosilane. Examples of suitable phenylsilanes and fluorosilanes are described in US patent application Ser. No. 27.
No. 9,474 (filed Dec. 2, 1988), which is assigned to the applicant and incorporated herein by reference in its entirety.

[Table 5] This reduction in filler content causes the inventive material to "flow" so that its rheology is improved to the extent that it fills relatively large openings in thick metal foils or in inner layers of circuit components. It is US Pat. No. 4,849,284
Advanced filling disclosed in No. (greater than 55% volume fraction)
Some materials cannot be filled. An important feature of the present invention is the fact that it improves rheology without unduly increasing the Z-axis coefficient of thermal expansion (CTE) of the material. The Z-axis CTE of a 30-45% by volume filler blend was measured to be from the widely used fiber reinforced PTFE over the temperature range of -55 to + 125 ° C (typically about 200 ppm / ° C). Was also quite low (see Table 6). Multilayer circuit boards made from RO 2800 laminate bonded together with the tie layer of the present invention exhibit a significantly lower overall CTE than that of fiber reinforced PTFE boards. Reducing CTE is important in increasing the reliability of plated through holes and vias that withstand thermal cycling and high temperature assembly.

[Table 6] The present invention expands the number of applications in which ceramic-filled PTFE composites can be used to construct useful printed wiring boards. The present invention is directed to structures that are already rigid (eg, etched CIC voltage plates or ground plates, and restraining cores).
ore), as well as the openings of circuit components associated with such structures). For example, FIG. 1A depicts a cross section of a rigid ground plane structure 50 having several openings 52. Sheet 5 of the present invention
4 and 56 (for example, about 0.26 to 0.45 ceramic)
Volume fractions) are then applied to both sides of ground plate 50. In B of FIG. 1, the stack 58 of A of FIG. 1 is laminated by applying heat and pressure. The composition of the present invention is capable of flowing smoothly so that it completely fills the openings and provides excellent thermal, mechanical and electrical properties. Next, referring to FIG. The composite material of the present invention can be processed into an undensified, unsintered sheet, which can be used to bond to multilayer printed wiring boards or to construct printed wiring boards by foil deposition. Figure 2
In general, such a multilayer circuit board is designated by 10. Multilayer board 10 comprises a plurality of layers of support material, 12, 14 and 16, all of which consist of electrical support material, preferably sold under the trademark RO-2800, U.S. Pat. No. 4,849. , 284 ceramic-filled fluoropolymer material. Each support layer 12, 14 and 16 has a conductor pattern 18, 20, 22 and 24 respectively. Note that a support layer having a circuit pattern on it means a circuit support. The plated through holes 26 and 28 are interconnected to the selected circuit pattern in a known manner. In the present invention, separate layers 30 and 32 of support material having the composition of the present invention are used as adhesive or binder layers to laminate the individual circuit supports together. A preferred method of forming such a laminate is to make a stack of circuit supports with alternating binder layers of one or more layers. The stack is then fused, thereby fusing the entire multi-layer assembly into a homogeneous composition that generally has the same electrical and mechanical properties.
It should be noted that adhesive bonding layers 30 and 32 may be used to laminate circuit supports comprised of materials other than the silane coated ceramic filled fluoropolymer of US Pat. No. 4,849,284. In a preferred embodiment, the multilayer circuit board comprises a plurality of circuit carriers, all of which are the electrical carrier materials of US Pat. No. 4,849,284. The highly filled composite materials (eg, 50% or more filler) referred to in US Pat. No. 4,849,284 are used in many printed wiring board designs (eg, large multi-layer boards (CPU boards) for mainframe computers, military surface mount assemblies). Very suitable for solid and microwave circuit board coupling assemblies). However, the insulation thickness (diele
Lower filler content (eg 45-50% by volume) for special MLB applications (eg thick power boards, CTE control thick restraint foils) which require thick voltage plates compared to tric thickness. Therefore, it is necessary to allow sufficient flow as instructed in the above-mentioned U.S. Patent Application No. 367,241. Low filler loadings of about 26% to less than 45% according to the present invention, circuit fabrication techniques for the manufacture of multi-chip modules that specifically require small hole laser drilling, good flow, and alkali resistance to electroless baths. Is one solution that promotes the development of. At low filler levels of the present invention (US Pat.
Good quality conventional multilayer boards (as intended by the material described in US Pat. No. 9,284) cannot be made, while US Pat.
The 9,284 material is not suitable for the particular type of multichip module emerging as the preferred packaging technology for high speed, high density devices. While the preferred embodiment has been shown and described, various changes and substitutions can be made therein without departing from the spirit and scope of the invention. Therefore, it should be understood that the present invention has been described by way of illustration and not limitation.

[Brief description of drawings]

1A and 1B are cross-sectional views of a rigid structure with openings before and after filling with a composite material of the present invention, respectively.

FIG. 2 is a cross-sectional view of a multilayer circuit board that uses the thermoplastic composite material of the present invention as a thin film bonding layer.

FIG. 3 is a graph showing the effect of the amount (%) of silane and coated silica filler on the laser processability of the composite at a beam energy of 3.9 J / cm ^{2 at} 248 mm.

FIG. 4 is a cross-sectional view of the circuit board of the present invention.

[Explanation of symbols]

52 opening 50 ground layer 54,56 Sheet of the present invention 58 Stacking of the members of FIG. 10 Multilayer circuit board 12, 14, 16 Layers of support material 18, 20, 22, 24 Conductive pattern 26,28 plated through ball 30,32 adhesive bonding layer 6 copper layers 4 Base material of the composite material of the present invention 2 Laser ablation hole a From the wall

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI H05K 3/46 H05K 3/46 T (72) Inventor Arin F Horn the Third United States, Connecticutto 06239, Daniel Sun, Broad Street 95 (72) Inventor Brett Kircheni Connecticut 06268, Stalls, Cayde Lane 25 (56) Reference JP 62-80916 (JP, A) JP 63-259907 (JP, A) US Patent 4849284 (US, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01B 3/44 H05K 3/38 H05K 3/46

Claims (24)

(57) [Claims] 1. An electrical support material comprising a fluoropolymer material and a ceramic filler material present in an amount of at least 26% to less than 45% by volume of the total electrical support material. An electrical support material with a silane coating on the agent. 2. The electrical support material of claim 1, comprising at least one layer of electrically conductive material disposed on at least a portion of the electrical support material. 3. The electrical utility of claim 1 wherein said fluoropolymer is selected from the group consisting of polytetrafluoroethylene, hexafluoropropene, tetrafluoroethylene or perfluoroalkyl vinyl ether.
Holding material. 4. The ceramic filler comprises silica.
The electrical support material according to claim 1. 5. The silane coating comprises p-chloromethylphenyltrimethoxysilane, aminoethylaminotrimethoxysilane, a mixture of phenyltrimethoxysilane and aminoethylaminopropyltrimethoxysilane, fluorosilane, and at least one. The electrical support material of claim 1, selected from the group consisting of a blend of fluorosilane and at least one phenylsilane. 6. The electrical support material of claim 1, wherein the silane coating is in an amount of greater than 2 wt% and up to 10 wt% based on the weight of the ceramic filler. 7. The silane coating is at least 1
The electrical support material of claim 6, comprising a blend of one fluorosilane and at least one phenylsilane. 8. A multilayer circuit including at least a first circuit layer and a second circuit layer, comprising an adhesive layer sandwiched between the first and second circuit layers, the adhesive layer being a fluoropolymer. At least 26% by volume of the total material and adhesive layer to 4
A multilayer circuit comprising a ceramic filler material in an amount of less than 5% by volume, the ceramic filler being silane coated. 9. The multilayer circuit of claim 8 including at least one plated through hole. 10. The multilayer circuit of claim 8, wherein the fluoropolymer material is selected from the group consisting of polytetrafluoroethylene, hexafluoropropene, tetrafluoroethylene or perfluoroalkyl vinyl ether. 11. The multilayer circuit of claim 8, wherein the ceramic filler comprises silica. 12. The silane coating comprises p-chloromethylphenyltrimethoxysilane, aminoethylaminotrimethoxysilane, a mixture of phenyltrimethoxysilane and aminoethylaminopropyltrimethoxysilane, fluorosilane, and at least one fluoro. 9. The multilayer circuit of claim 8 selected from the group consisting of a silane and a blend of at least one phenylsilane. 13. The multilayer circuit of claim 8, wherein the silane coating is in an amount greater than 2 wt% and up to 10 wt% based on the weight of the ceramic filler. 14. The multilayer circuit of claim 13, wherein the silane coating comprises a blend of at least one fluorosilane and at least one phenylsilane. 15. A rigid structure having at least one opening that at least partially passes through the structure, and at least one of the openings. An article comprising a composite material, the composite material comprising a fluoropolymer material and a silane-coated ceramic filler in an amount of at least 26% to less than 45% by volume of the total composite material. 16. The method of claim 15, wherein the fluoropolymer material is selected from the group consisting of polytetrafluoroethylene, hexafluoropropene, tetrafluoroethylene or perfluoroalkyl vinyl ether.
Product . 17. The article of claim 15, wherein the ceramic filler comprises silica. 18. The silane coating comprises p-chloromethylphenyltrimethoxysilane, aminoethylaminotrimethoxysilane, a mixture of phenyltrimethoxysilane and aminoethylaminopropyltrimethoxysilane, fluorosilane, and at least one. The product of claim 15 selected from the group consisting of a blend of fluorosilane and at least one phenylsilane .
Goods . 19. The method of claim 18, wherein the silane coating is in an amount of up to 10 wt.% Greater than 2% by weight relative to the weight of the ceramic filler, product of claim 15. 20. The method of claim 19, wherein the silane coating comprises a blend of at least one phenyl silane with at least one fluoro silane, product of claim 19. 21. An electrical support material comprising a fluoropolymer material and a ceramic filler material in an amount of at least about 26% by volume of the total support material, the ceramic filler comprising at least one fluoropolymer material. Silane and small
A silan coating comprising a blend with at least one phenylsilane , the silane coating being present in an amount of more than 2% and up to 10% by weight, based on the weight of the ceramic filler, for electrical applications. Support material. 22. A multilayer circuit including at least a first circuit layer and a second circuit layer, comprising an adhesive layer sandwiched between the first and second circuit layers, the adhesive layer being a fluoropolymer. A material and a ceramic filler in an amount of at least 26% by weight of the total adhesive layer, said ceramic filler comprising at least one fluorosilane and at least 1
A multi-layer circuit characterized in that it has a silane coating comprising a blend of phenylsilanes of the species , the silane coating being present in an amount of from 2 to 10% by weight, based on the weight of the ceramic filler. 23. A rigid structure having at least one opening that at least partially extends through the structure; and in the at least one opening. A composite material comprising a fluoropolymer material and a ceramic filler in an amount of at least 26% by volume of the total composite material, the ceramic filler having a silane coating,
The product, wherein the silane coating is in an amount of more than 2% by weight and up to 10% by weight relative to the weight of the ceramic filler. 24. the silane coating comprises a blend of at least one phenyl silane with at least one fluoro silane, product of claim 23.