Prepregs and laminates with uniform dielectric properties

Abstract

To provide a prepreg for a high frequency substrate, a metal laminate and a printed wiring board manufactured therewith that solve the distortion problem by eliminating a gap between the dielectric constant of a matrix and the dielectric constant of a reinforcing material.SOLUTION: In a prepreg 10 including a partially cured resin-impregnated reinforcing material portion 14 and a free resin portion 12, the resin includes at least one kind of high dielectric constant material, when the dielectric constant of the free resin portion is DKw, and the dielectric constant of the resin-impregnated reinforcing material portion is DKWR, a high dielectric constant material is added to the resin in such an amount that DKWR and DKW do not differ more than (±)15%.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] 2. Background of the Invention (1) Field of the invention The present invention relates to resin compositions comprising one or more high Dk materials together with a base resin, where the high Dk materials have a dielectric constant higher than that of the cured base resin.The present invention also relates to prepregs and laminates made with the resin compositions of the present invention, which have a uniform dielectric constant across the cross section of the prepreg or laminate. [Background technology]

[0002] (2) Description of technology Prepregs and copper-clad laminates are planar materials routinely used in the manufacture of printed circuit boards. Prepregs and laminates are composite structures that typically contain a reinforcing material such as woven fiberglass, non-woven glass, paper, or other fibrous or non-fibrous materials, and a polymeric resin used as a matrix material - a material that is applied or used to impregnate the reinforcing material.

[0003] As the operating frequencies of electronic devices are constantly increasing, it is becoming more important that the dielectric properties of the prepregs and laminates used in the manufacture of PCBs be carefully controlled. One problem with current prepregs and laminates is that the dielectric properties of the reinforcement and matrix materials are very different. When very high speed signals are transmitted through structures such as printed circuit boards assembled with such metal-clad laminates, the signals experience distortion and differences in velocity as the signals propagate across anisotropic regions. The problem is further compounded when different signals are running, and in worst case scenarios, the differences in velocity of propagation over long distances lead to major signal integrity problems and in some cases total signal loss. This problem is of great concern to electronic device designers, especially with on-board frequencies running up to and beyond 14 GHz to transmit 100 gigabits per second over four channels, where distortion appears to be a major design challenge. Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention is directed to prepregs and laminates that solve the distortion problem by eliminating the gap between the dielectric constant of the matrix and the dielectric constant of the reinforcement material. [Means for solving the problem]

[0005] Thus, one aspect of the present invention is a resin composition comprising one or more base resins and one or more high Dk materials, where the one or more high Dk materials are present in the resin composition in an amount sufficient to impart to the resin composition a cured Dk that matches to within plus or minus (±) 15% the Dk of the reinforcing material to which the resin composition is applied.

[0006] Another aspect of the present invention is a resin composition comprising at least one base resin and about 5 to about 60 weight percent particles of one or more high Dk materials selected from the group consisting of strontium titanate, barium titanate, lead titanate, lead zirconate, lead lanthanum zirconate titanate, and combinations thereof, wherein the Dk of the resin composition matches to within plus or minus (±) 15% the Dk of the woven or woven glass fiber reinforcement material to which the resin composition is applied.

[0007] Yet another aspect of the present invention is a method for the detection of Dk R Reinforcement material having Dk W wherein Dk R teeth Dk W more than 15% grater than The resin composition further comprises a Dk R Plus or My Hardening Dk matches within (±)15% W in an amount sufficient to impart Contains one or more high Dk materials present in the composition.

[0008] Yet another embodiment of the present invention is a prepreg comprising: a reinforcement portion impregnated with at least a partially cured resin; and a free resin portion, wherein the resin comprises at least one high dielectric constant material, the free resin portion having a dielectric constant DKw, and the resin impregnated reinforcement portion having a dielectric constant DKw. WR where the high dielectric constant material has a D WR DK W Match it with D K WR and D.K. W Introduce into the resin in sufficient quantity so that the It is entered. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view of a prepreg or laminate embodiment of the present invention that includes a uniform dielectric constant across its cross-section. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Description of the Present Embodiment The present invention is generally directed to reinforced prepregs and laminates for use in the electronics industry that include a resin or matrix component and a reinforcing component. The starting components used in the prepregs and laminates of the present invention have dielectric constants that differ by more than 15%. In particular, the resin component is DK W The reinforcing component is DK R DK W and D.K. R The difference is greater than 15%. In fact, R And the DK of the resin material without the high Dk material (referred to herein as DK0) can easily differ by more than 30%.

[0011] The term "dielectric constant of the starting components" refers to the dielectric constant of each of the starting materials before they are combined to form the resin impregnated reinforcing material and / or before they are incorporated into reinforced prepregs and / or laminates.

[0012] In one embodiment of the invention, a high dielectric constant material is used to modify the resin component to form a prepreg or laminate in which the dielectric constant of the matrix component and the dielectric constant of the reinforcement material are "uniform" or "matched." The terms "uniform" or "matched" are used interchangeably herein to refer to two dielectric constants that do not differ from each other by more than plus or minus (±) 15%, and more preferably do not differ from each other by more than plus or minus (±) 5%.

[0013] Another aspect of the present invention is prepregs and laminates that have a consistent or uniform dielectric constant across their cross-section. In the case of a prepreg or laminate, this is the dielectric constant (DKWR ) is the dielectric constant (DK W In this embodiment, the resin The dielectric constant is matched to that of the resin impregnated reinforcing material to form a laminate having a matched dielectric constant across its cross section.

[0014] In the above embodiment, the dielectric constant (Dk R ) is generally fixed. Furthermore, The dielectric constant (Dk0) of the resin or matrix material without high dielectric constant material is generally Electricity rate (Dk R ) is significantly different, i.e., is different by more than ±15%. Before the matrix material is combined with the reinforcement material, one or more high dielectric constant (Dk) The dielectric constant is matched by incorporating the material into a resin (also referred to as a matrix material).

[0015] Referring now to Figure 1, a prepreg (10) of the present invention is shown having a cross section "Y". The prepreg includes a free resin portion (12) and a resin impregnated reinforcing material portion (14). The free resin portion has a Dk W The resin-impregnated reinforcement material part has Dk WR Prepreg Or the free resin part of the laminate is Dk WR Dk can be determined independently of W Having The term "free resin" refers to resin that is part of a prepreg or laminate, but is at least one micron from any reinforcement surface - top surface (16), bottom surface (18) or sides (20) and (22) - after the resin has been introduced into the resin impregnated reinforcement material section. Free resin will generally be b-staged or c-staged resin. This includes, for example, the free resin remaining after a resin-coated copper sheet is applied face down to a core resin-impregnated reinforcement material to form a copper-coated prepreg or laminate.

[0016] All "dielectric constants" discussed herein and dielectric constant ranges or values ​​referred to herein are determined by the Bereskin test method, or alternatively, by the split post method. When a comparison of dielectric constants is discussed, the dielectric constants being compared are determined by the same test method. The dielectric constant of a resin is determined using a fully cured resin sample. The dielectric constant of a resin impregnated reinforcement part, Dk WR is determined using a sample of the reinforcement material impregnated with fully cured resin.

[0017] The reinforcing material can be any sheet or ground material known to be useful in the manufacture of substrate sheets for fabrication of prepregs or laminates used in the manufacture of printed circuit boards. As mentioned, ground material(s) such as ground glass fiber materials can be used, but the reinforcing material is preferably a sheet material. For example, the reinforcing sheet material can be inorganic fiber fabrics including various glass fabrics (e.g., roving cloth, cloth, chopped mat, and surfacing mat), metal fiber fabrics, etc.; woven or nonwoven fabrics made from liquid crystal fibers (e.g., wholly aromatic polyamide fibers, wholly aromatic polyester fibers, and polybenzazole fibers); woven or nonwoven fabrics made from synthetic fibers (e.g., polyvinyl alcohol fibers, polyester fibers, and acrylic fibers); natural fiber fabrics (e.g., cotton, linen, and felt); carbon fiber fabrics; and natural cellulosic fabrics (e.g., kraft paper, cotton paper, and paper-glass combined fiber paper).

[0018] In one aspect of the invention, the reinforcing material is a woven glass fabric material. Such woven glass fabric materials have a Dk of about 3.5 to 7.0 or higher. R Such glass fibers will have Examples of fiber and textile materials include those having a Dk of about 3.5 to about 4.5. R Low Dk glass with E- Glass; including R-glass, ECR-glass, S-glass, C-glass, Q-glass and other glass fabrics of the type known to be useful in the manufacture of glass fabric reinforced prepregs and laminates.

[0019] The resin compositions of the present invention will include one or more base resins known in the art to be useful in the manufacture of prepreg and laminate materials. The base resin will typically be a thermosetting or thermoplastic resin. Examples of useful base resins include epoxy resins, polyphenylene ether based resins, cyanurate resins, bismaleimide resins, polyimide resins, phenolic resins, furan resins, xylene formaldehyde resins, ketone formaldehyde resins, urea resins, melamine resins, aniline resins, alkylene resins, arylamine ... Examples of the resins that can be used include unsaturated polyester resins, diallyl phthalate resins, triallyl cyanurate resins, triazine resins, polyurethane resins, silicone resins, and combinations or mixtures thereof.

[0020] In one aspect of the invention, the base resin is or comprises an epoxy resin. Some examples of useful epoxy resins include phenolic type, such as those based on diglycidyl ether of bisphenol A, those based on polyglycidyl ether of phenol-formaldehyde novolac or cresol-formaldehyde novolac, those based on triglycidyl ether of tris(p-hydroxyphenol)methane or those based on tetraglycidyl ether of tetraphenylethane; amine type, such as those based on tetraglycidyl-methylenedianiline or those based on triglycidyl ether of p-aminoglycol; cycloaliphatic type, such as those based on 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate. The term "epoxy resin" also refers to the reaction product of a compound containing an excess of epoxy (such as of the above-mentioned type) with an aromatic dihydroxy compound. These compounds can be halogen-substituted. Epoxy-resins that are derivatives of bisphenol A, especially FR-4, are preferred. FR-4 is made by the advancing reaction of excess diglycidyl ether of bisphenol A with tetrabromobisphenol A. Mixtures of epoxy resins with bismaleimide resins, cyanate resins and / or bismaleimide triazine resins can also be applied.

[0021] In addition to the base resin, the resin composition will typically include an initiator or catalyst, one or more optional flame retardants, and a solvent. The flame retardant can be any flame retardant material known to be useful in resin compositions used in the manufacture of prepregs and laminates used in the manufacture of printed circuit boards. The flame retardants can contain halogens or they can be halogen-free. Alternatively, or in addition, the resin can contain halogens such as bromine to impart flame retardancy to the cured resin.

[0022] The resin composition may also include a polymerization initiator or catalyst. Some useful examples of initiators or catalysts include, but are not limited to, peroxides or azo-type polymerization initiators (catalysts). The initiator / catalyst generally chosen may be any compound known to be useful in the synthesis or curing of resins, whether or not it performs one of these functions.

[0023] The resin composition includes one or more solvents, which are typically used to solubilize the appropriate resin composition components and / or to control the viscosity of the resin and / or to keep the resin components in a suspended dispersion. Any solvent known by those skilled in the art to be useful in connection with thermosetting resin systems can be used. Particularly useful solvents include methyl ethyl ketone (MEK), toluene, dimethylformamide (DMF) or mixtures thereof. As described below, the resin composition is used to make prepregs and laminates. During the manufacturing process, reinforcement materials are impregnated or otherwise combined with the resin composition, and some or most of the solvent is removed from the resin composition to make the prepregs and laminates. Thus, when weight percentage amounts of the resin composition are listed, they are reported on a dry, solvent-free basis unless otherwise noted.

[0024] The resin composition may contain a variety of other optional ingredients, including fillers, reinforcing agents, adhesion promoters, defoamers, leveling agents, dyes and pigments. For example, fluorescent dyes may be added in trace amounts to the resin composition and laminates made therefrom may be exposed to UV light in an optical inspection device in a board shop. Other optional ingredients known by those skilled in the art to be useful in resins used in the manufacture of printed circuit board laminates can also be included in the resin compositions of the present invention.

[0025] The resin composition of the present invention will also include one or more high Dk materials. The high Dk material can be any material that can be introduced into a liquid resin such that the Dk of a cured or partially cured resin composition containing the high Dk material is different from, and preferably higher than, the Dk of the resin component of the resin composition. In one embodiment, the high Dk material will have a Dk greater than about 200, and more preferably greater than about 500.

[0026] One class of useful high Dk materials are ferroelectric materials. Examples of some useful ferroelectric materials include strontium titanate, barium titanate, lead titanate, lead zirconate titanate, lead lanthanum zirconate titanate, and combinations thereof. Particularly useful high Dk materials are strontium titanate and barium titanate.

[0027] The high DK material can be introduced into the resin composition as a particulate material. When using a high DK material, the high DK material will typically have a particle size ranging from about 1 nm to 40 microns.

[0028] The high DK material will be included in the resin composition in an amount sufficient to form a homogeneous prepreg or laminate. In one embodiment, the homogeneous prepreg or laminate is formed by mixing the high DK material with the high DK material. R The resin composition or matrix is ​​within ±15%, and preferably within ±5% of the above. Sex Dk W In another embodiment, a homogeneous prepreg or laminate may be used. is the Dk of the resin-impregnated reinforcement material part WR Dk within ±15%, and preferably within ±5% W The resin will have free moieties having the formula:

[0029] The amount of high DK material introduced into the resin composition is determined by the DK of the base resin and the DK of the reinforcement material. R In general, Dk0 and Dk RThe greater the difference between the Dk and the higher the amount of high Dk material that will be included in the resin composition. Generally, greater than about 2% by weight of the resin composition on a dry basis is needed to cause a change in the Dk of the base resin. The maximum amount of high Dk material that can be introduced into the resin composition without significantly affecting the properties of the resin composition is about 70% by weight on a dry, solvent-free basis. In another embodiment, the high Dk material will be present in the resin composition in an amount ranging from about 5 to about 60% by weight on a dry basis. We have found that the addition of about 5 to about 60% by weight of particulate barium titanate to a base resin having a Dk of about 40%. is the Dk of the resin composition W From just above 4 at 5 wt.% addition to 60 wt.% It was found that the addition of 50% increased the β-amylindrical acid concentration to values ​​higher than 7.5.

[0030] The above resin compositions are particularly useful for the manufacture of prepregs and / or laminates used in the manufacture of printed circuit boards. To be useful in the manufacture of printed circuit boards, the laminates can be partially cured or b-staged - to form what is known in the industry as prepregs - in which state they can be laid up with additional sheets of material to form c-staged or fully cured laminate sheets. Alternatively, the resins can be built up into c-staged or fully cured sheets of material.

[0031] In one useful processing system, the resin composition / reinforcement material combination described above is useful for the production of prepregs in a batch or continuous process. Prepregs are generally made with a "core" material, such as a roll of woven glass fiber web, which is unwound into a series of drive rolls. The web then passes through a coating area where it is coated with the resin composition / reinforcement material of the present invention. The glass web passes through a tank containing a clear thermosetting resin system, solvent, and other ingredients, where the glass web becomes saturated with resin. The saturated glass web then passes through a pair of metering rolls, which remove excess resin from the saturated glass web, after which the resin-coated web travels through a section of a drying tower for a selected time until the solvent evaporates from the web. Second and subsequent coatings of resin can be applied to the web by repeating these steps until production of the prepreg is complete, at which point the prepreg is wound onto a roll. The woven glass web can be replaced with woven materials, paper, plastic sheets, felt, and / or particulate materials, such as glass fiber particles or particulate materials.

[0032] In another method for the manufacture of prepreg or laminate materials, the thermosetting resins of the present invention are premixed in a mixing vessel at ambient temperature and pressure. The viscosity of the premix is ​​about 600-1000 cps and can be adjusted by adding or removing solvent from the resin. A woven substrate - such as E-glass - is pulled through a dip tank containing the premixed resin and through an oven tower where excess solvent is driven off, and the prepreg is rolled or sheeted to size and combined between Cu foils in various configurations depending on the glass weave style, resin content and thickness requirements.

[0033] The resin composition can also be applied in a thin layer to a Cu foil substrate (RCC--resin coated Cu) using a slot die or other related coating methods.

[0034] The resins, prepregs and resin-coated copper foil sheets described above can be used to produce laminates, such as those used in the manufacture of printed circuit boards, in a batch or continuous process. In a typical continuous process for producing the laminates of the present invention, continuous sheets in the form of copper, resin prepreg and thin woven fabric sheets are continuously unwound into a series of drive rolls to form a layer of woven fabric web adjacent to the resin prepreg sheet adjacent to the copper foil sheet, such that the prepreg sheet is placed between the copper foil sheet and the woven fabric sheet. The web is then subjected to heat and pressure conditions for a time sufficient to drive the resin into the woven fabric material and to fully cure the resin. In the resulting laminate, the migration of the resin material into the woven fabric reduces the thickness of the resin layer (the distance between the copper foil material and the woven fabric sheet material) to approach zero as the combined layer discussed above transforms from a three-layer web into one laminate sheet. In an alternative to this method, a prepreg resin sheet can be applied to one side of a textile material layer and the combination sandwiched between two copper layers, after which heat and / or pressure can be applied to the combination to cause the resin material to flow and fully impregnate the textile layer and bond both copper foil layers to the central laminate.

[0035] In yet another embodiment, the resin composition coated copper sheets can be produced simultaneously with the production of laminates by applying a thin coating of resin to two continuously moving copper sheets, removing excess resin from the sheets to control the resin thickness, and then partially curing the resin under conditions of heat and / or pressure to form a b-staged resin coated copper sheet that can then be used directly in the laminate production process.

[0036] In yet another embodiment, a fabric material, with or without pretreatment, can be continuously fed into a bath of the resin composition, allowing the fabric material to be impregnated with the resin composition. Optionally, the resin composition can be partially cured at this stage of the process. One or two copper foil layers are then mated with the first and / or second flat surfaces of the resin composition-impregnated fabric sheet to form a web, after which heat and / or pressure are applied to the web to fully cure the resin composition.

[0037] The present invention has been described in an illustrative manner. It is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. Many modifications and variations of the present invention are possible in light of the above description. Thus, within the scope of the appended claims, the present invention may be practiced other than as specifically described.

Claims

1. an at least partially cured resin-impregnated reinforcement material portion; and Free resin part wherein the resin comprises at least one high dielectric constant material, the free resin portion having a dielectric constant DKw and the resin impregnated reinforcement material portion having a dielectric constant DK WR where the high dielectric constant material has a D WR and D.K. W DK should not differ by more than ±15%. WR DK W is introduced into the resin in an amount sufficient to match Here, the dielectric constant is determined by the split post method. The prepreg described above.

2. 2. The prepreg of claim 1, wherein the one or more high Dk materials each have a Dk of at least 500.

3. 2. The prepreg of claim 1, wherein the one or more high Dk materials is a particulate material.

4. The prepreg of claim 3, wherein the particle size of the one or more high Dk materials ranges from 1 nm to 40 microns.

5. 2. The prepreg of claim 1, wherein the one or more high Dk materials is a ferroelectric material.

6. 6. The prepreg of claim 5, wherein the ferroelectric material is selected from the group consisting of strontium titanate, barium titanate, lead titanate, lead zirconate titanate, lead lanthanum zirconate titanate, and combinations thereof.

7. 2. The prepreg of claim 1, wherein the base resin is a thermosetting or thermoplastic resin.

8. The prepreg of claim 1, wherein the one or more high Dk materials are present in the composition in an amount ranging from 2 to 70 weight percent.

9. 2. The prepreg of claim 1, wherein the reinforcing material is selected from the group consisting of woven and woven fiberglass fabric, paper, felt, fiberglass and plastic sheeting.

10. 10. The prepreg of claim 9, wherein the reinforcing material is a low Dk woven or woven fiberglass fabric.

11. The prepreg of claim 10, wherein the low Dk knitted or woven glass fiber fabric has a Dk in the range of 3.5 to 7.

0.

12. 2. The prepreg of claim 1, wherein the free resin is resin that is at least 1 micron from any reinforcement surface.

13. 2. The prepreg of claim 1, wherein the resin composition comprises at least one base resin and from 5 to 60 weight percent particles of a higher Dk material selected from the group consisting of strontium titanate, barium titanate, lead titanate, lead zirconate titanate, lead lanthanum zirconate titanate, and combinations thereof.

14. D.K. WR and D.K. W 2. The prepreg of claim 1, wherein the thickness varies by no more than (±) 5%.

15. A laminate comprising the fully cured prepreg of claim 1.

16. 16. The laminate of claim 15 comprising at least one copper layer.

17. 10. A printed circuit board comprising the prepreg of claim 1 fully cured in at least one layer.

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