JPH0424373B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a manufacturing method by continuous molding of a laminate used as a printed wiring board.

BACKGROUND OF THE INVENTION In recent years, frequencies used in fields such as electronic industry, communications, and computers have shifted to high frequency regions such as MHz and GHz. In the insulating layers of printed wiring boards used in such high frequency ranges, it is necessary to have a smaller dielectric constant in order to shorten signal propagation delay, and a smaller dielectric loss tangent in order to reduce power loss. Each is desired. For this purpose, resins such as tetrafluoroethylene resin (Teflon) and polyphenylene oxide (PPO), which have small dielectric constants and dielectric loss tangents, are used, and prepregs made by impregnating base materials such as glass cloth with these resins are laminated. Attempts have been made to create laminates that serve as insulating layers for printed wiring boards by molding. Furthermore, in order to reduce the dielectric constant of the laminate serving as the insulating layer, it is effective to increase the resin content in the prepreg. That is, the volume fraction of the resin in the laminate is V _R , the volume fraction of the glass cloth base material in the laminate is V _G , the dielectric constant of the resin is ε _R , the dielectric constant of the glass cloth base material is ε _G , Then, the dielectric constant ε of the entire laminate is
becomes like the following formula. logε=V _R logε _R +V _G logε _G And since the dielectric constant ε _R of resin is generally smaller than the dielectric constant ε _G of glass (by the way, the dielectric constant of the polymer according to the formula () of the present invention is about 2.8). On the other hand, the dielectric constant of E glass is 7.23, and the dielectric constant of D glass is
4.74), the larger the volume fraction V _R of the resin and the smaller the volume fraction V _G of the glass cloth base material, the smaller the dielectric constant ε of the entire laminate. On the other hand, the specific gravity of glass is about 2.2 and the specific gravity of resin is about 1.4, and if the resin content is x% by weight, then V _R = (x/1.4)/{(x/1.4) + (100−x )/
2.2} Since V _G =1−V _R , the larger x becomes, the larger V _R becomes and the smaller V _G becomes. Therefore, as the resin content x increases, the dielectric constant ε of the entire laminate decreases.

[Problem to be solved by the invention]

However, when forming an insulating layer using the above resins, the glass transition temperature (Tg) of these resins is 180 to 200.
There are problems such as insufficient heat resistance, which is as low as 10°C, and the inability to form a multilayer printed wiring board because the reliability of the through holes cannot be obtained due to the occurrence of smear during through hole processing. Furthermore, as mentioned above, it is advantageous to increase the resin content in order to lower the dielectric constant, and therefore it is desirable to manufacture a laminate using prepreg with a high resin impregnation rate. In the case of laminated molding using a multi-stage press, slips are likely to occur between the prepreg layers due to a large amount of resin flowing during hot and pressure molding, and if the resin content is 45 to 50% by weight or more, Molding becomes almost impossible. For this reason, there is a limit to increasing the resin content when molding is performed using a multistage press. The present invention has been made in view of the above points, and provides a method for manufacturing a laminate that can maintain low dielectric constant, dielectric loss tangent, and high heat resistance, and can also improve flame retardancy. The first objective is to further increase the resin content and mold it, and the second objective is to make it possible to lower the dielectric constant in this respect as well.

[Means to solve the problem]

The present invention provides a polyaromatic cyanate represented by the following formula (), (In the formula, Ar is aromatic. B is a _C7-20 polycyclic aliphatic group. D is each independently a substituent containing no active hydrogen.
q, r, and s are each independently an integer of 0, 1, 2, or 3, provided that the sum of q, r, and s is greater than or equal to 2. t is an integer from 0 to 4, each independently. x is a number from 0 to 5) A flame retardant represented by the following formula (), (In the formula, R and R' are aromatic or brominated aromatic substituents that do not contain active hydrogen. n is a positive number) A flame retardant represented by the following formula (), (In the formula, n is an integer of 0, 1 or 2) A varnish is prepared by blending a polyaromatic cyanate with a reaction catalyst, and a base material is impregnated with this varnish to create a long belt-shaped prepreg. The present invention relates to a method for manufacturing a laminate, which is characterized in that a plurality of laminates are piled up, taken off, continuously fed, heated and pressurized, and laminated. The present invention will be explained in detail below. As the polyaromatic cyanate represented by the formula (), those disclosed in Patent Application Publication No. 1988-500434 can be used. That is, this polyaromatic cyanate provides an aromatic polytriazine (polyaromatic cyanate resin) that is significantly more stable against hydrolysis and has superior thermal stability than conventional polytriazine. In the polyaromatic cyanate of formula () used in the present invention, the aromatic group Ar means any group containing an aromatic group, such as benzene, naphthalene, phenanthracene, anthracene, or biaromatic group. group, two or more aromatic groups bridged by alkylene moieties. Suitable examples include benzene, naphthalene, biphenyl, binaphthyl, and diphenylalkylene groups, with benzene groups being particularly preferred. The C _7-20 polycyclic aliphatic group B means an aliphatic group containing two or more rings, and the polycyclic aliphatic group has one or more double bonds or triple bonds. may be included.
Suitable polycyclic aliphatic groups include the following. (In the formula, Y is -CH ₂ -, -S-,

[Formula], and D ¹ is a C _1-5 alkyl group. ) especially (a)
(b)(c)(d)(e)(f)(g) or (l) are preferred, more preferred are (a)(b)(c)(d)(l), Particularly preferred is (a). D in formula () means all substituents that can be substituted on the organic hydrocarbon group, but substituents containing active hydrogen atoms are excluded. Active hydrogen atom means a hydrogen atom bonded to an oxygen, sulfur, or nitrogen atom. Each D in formula () is defined independently, and includes, for example, alkyl, alkenyl, alkynyl, aryl, alkaryl, aralkyl, halo, alkoxy, nitro,
carboxylate, sulfone, sulfide, carbonate, etc., preferably _C1-10 alkyl,
C _1-10 alkenyl, nitro, halo, C _1-3
most preferred are alkyl, _C1-3 alkynyl, bromo, chloro. Further, t in formula () is an integer from 0 to 4, preferably an integer of 0, 1 or 2, more preferably 0 or 1, and most preferably 0. Each t in formula () is defined independently.
q, r, s are integers of 0, 1, 2, or 3, and optimally 1. Although q, r, and s are each defined independently, their total is set to be 2 or more. Furthermore, x is a positive number from 0 to 5. The polyaromatic cyanate of formula () has x of 0
It is found as a mixture of up to 5 compounds, where x is defined as the average number of this mixture. A preferred embodiment of the polyaromatic cyanate of formula () is represented by the following formula. Therefore, the aromatic polytriazine (polyaromatic cyanate resin) obtained from the polyaromatic cyanate of formula () has a low dielectric constant (ε2.78 or so), a low dielectric loss tangent (tan δ0.003 or so), and high heat resistance. (Glass transition temperature Tg250 or higher, oven heat resistance 300
It has excellent properties as a resin constituting the insulating substrate of a printed wiring board.
Therefore, in the present invention, a flame retardant represented by the formula () and a flame retardant represented by the formula () are further blended to impart flame retardant properties required for printed wiring boards. In the phenoxy-terminated tetrabromobisphenol A carbonated oligomer of formula (), R and R' are aromatic or brominated aromatic substituents containing no active hydrogen, e.g.

【formula】

【formula】

[Formula] (R ₁ is Br, CH ₃ , C ₂ H ₅ , etc., or a combination thereof, m is an integer of 1, 2, or 3)
etc. In the formula (), n is a positive number that is not particularly limited, but those currently available are mixtures where n=10 to 20. Other values of n can also be used. The flame retardant effect of formula () or formula () combination of flame retardants depends on the amount of Br, and is based on the UL standard.
In order to obtain flame retardancy at the level of 94V-0, the content of Br must be 5 to 10% by weight relative to the total amount of the polyaromatic cyanate of formula () and the flame retardant of formula () and formula (). % flame retardant of formula (),
Formula () so that the Br content is 5 to 10% by weight
It is best to mix each flame retardant. In order to blend the flame retardant of formula () so that the Br content is 5 to 10% by weight, the compound amount as a compound should be 10 to 20% by weight, and the flame retardant of formula () should be blended at 10 to 20% by weight.
In order to achieve a Br content of 3 to 10% by weight, the amount of each compound is generally set to 6 to 20% by weight. If the amount of flame retardant is too large, problems may arise in heat resistance, so the upper limit is preferably set to the above value. As the reaction catalyst for polymerizing the polyaromatic cyanate of formula (), organic metal salts such as imidazoles, tertiary amines, organic cobalt salts such as cobalt naphthenate and cobalt octylate can be used, and in particular Organic cobalt salts are preferred. Although the amount of the reaction catalyst is not particularly limited, for example, when organic cobalt salts are used as the reaction catalyst, the amount of cobalt ions relative to the weight of the polyaromatic cyanate of formula () may be adjusted depending on the desired gel time of the varnish (described later). Weight ratio: 10~
It is blended in a range of about 700ppm. and polyaromatic cyanate of the above formula (),
A varnish is prepared by dissolving formula (), a flame retardant of formula (), a reaction catalyst, etc. in an organic solvent. The organic solvent is not particularly limited as long as it dissolves the polyaromatic cyanate of formula () and the flame retardant of formula () and formula () and does not adversely affect the reaction, such as aromatic hydrocarbons, alcohols, and ketones. For example, toluene, acetone, methyl ethyl ketone, dimethyl formamide, methyl cellosolve, etc. can be used alone or in combination of two or more. The concentration of varnish is 50 to 70 solids.
It is common to adjust it so that it is % by weight. However, when preparing prepreg,
The base material is not particularly limited, but woven or nonwoven glass fiber fabric is generally used, and this base material is impregnated with varnish and dried by heating. E-glass is generally used as the glass that makes up the glass fibers, but while E-glass has a dielectric constant of 7.23, D-glass has a low dielectric constant of 4.47, so it is inferior in terms of dielectric constant. It is preferable to use D-glass fiberglass. However, E-glass fibers are superior in terms of processability and cost. Although Q glass has an extremely low dielectric constant of 3.89, it is not practical in terms of processability and cost. The amount of varnish impregnated into the base material should be set so that the ratio of solid content (compound of formula () to compound of formula (), formula ()) to the base material is 50% to 70% by weight. preferable. As mentioned above, the dielectric constant can be lowered by increasing the resin content.
By setting the value as high as 50% by weight or more, for example, if E-glass cloth is used as the base material, the dielectric constant of the laminate will be about 3.3 to 3.6, and the dielectric loss tangent will be about 3.3 to 3.6.
When D glass cloth is used as the base material, the dielectric constant of the laminate is 3.1 to 0.005.
It is possible to make the dielectric loss tangent about 3.4 and about 0.001 to 0.005. If the resin content is too high, the resin tends to foam during molding and become uneven, so it is preferable to set the upper limit of the impregnation rate to 70% by weight as described above. The heating and drying conditions when preparing prepreg are influenced by the amount of reaction catalyst blended, etc., but in the present invention, the reactivity of the prepreg is lowered than in the case of multistage press because the molding is performed using a continuous molding press. It is preferable to allow the gel to proceed slightly, for example, the gel time at 170℃ is
It is preferable to set the reactivity of the prepreg to about 45 to 70 seconds. In order to set the reactivity of the prepreg to this level, the gel time of the varnish at 170°C is preferably set to about 3 to 4 minutes. In the present invention, a prepreg is prepared in the form of a long strip using a long strip as a base material, and it is preferable to store it by winding it into a roll.
Then, a laminate can be manufactured using a continuous molding press, for example, as shown in FIG. Fig. 1 shows a double-belt type continuous forming press equipped with a pair of upper and lower steel belts 1, 1, in which a plurality of sheets of prepreg 2, 2... are continuously fed out from a roll and stacked on top of each other. Further, long strip-shaped metal foils 3 are stacked on both or one side of the upper and lower sides, and these are continuously introduced between the steel belts 1, 1. The steel belts 1 and 1 are equipped with a heating device, and the prepreg 2 is heated while being pressurized between the steel belts 1 and 1, and the polyaromatic cyanate impregnated into the prepreg 2 is polymerized and hardened, and the prepreg 2 is heated to form a plurality of sheets. The prepregs 2 are laminated and a metal foil 3 is bonded to the outer layer to form a double-sided metal foil-clad laminate 4 or a single-sided metal foil-clad laminate 4. This laminated plate 4 is cooled while being pulled out from between the steel belts 1 by a cooling roll 5, and further cut into a predetermined length by a cutter 6. In this way, in the continuous forming press method, the prepreg 2 is heated and press-formed between the steel belts 1, 1 under tension due to pulling, and the prepregs 2, 2... The molding is done without free movement. Therefore, even if a prepreg 2 with a high resin content is used, there is no risk of slips occurring between the prepregs 2 due to the flow of resin, unlike in the case of multistage pressing, and the prepreg has a high resin impregnation rate. 2 can be used to form a laminate 4 with a high resin content. Here, the metal foil is 9μ thick copper foil with aluminum carrier layer, 18μ thick copper foil,
Double-sided roughened copper foil with a thickness of 35μ, 70μ, or 105μ can be used. The molding conditions for this continuous molding press are a molding temperature of 170 to 230°C and a molding pressure of 10°C.
It is common to set the pressure to ~50 kg/cm ² and the forming time (passing time between the steel belts 1 and 1) to about 2 to 3 minutes. The inner layer printed wiring board 7 can be prepared by etching the metal foil 3 of the laminated board 4 with metal foil on both sides or one side formed as described above to form the circuit 8. Then, as shown in FIG. 2, a plurality of inner layer printed wiring boards 7 are stacked with prepreg 2 interposed therebetween, and a metal foil 3 is stacked on the outermost layer, which is heated and pressure molded to form a multilayer printed wiring board. can be created. Molding conditions include heating temperature of 170℃~
Generally, the temperature is set at 230°C, the maximum pressure is about 30 to 40 kg/cm ² , and the time is about 90 to 120 minutes.
When after-curing at a temperature of about 220 to 230°C after molding, a molding temperature of about 170 to 180°C is sufficient.

【Example】

The present invention will be explained in detail below using examples. Example 1 78 parts by weight of polyaromatic cyanate (XU-71787 manufactured by Dow Chemical Company) represented by the following formula, In formula (), R and R' are formula (b), and n is 10
15 parts by weight of a flame retardant mixture of ~20 (brominated carbonate oligomer; BC-58 manufactured by Great Lakes), 7 parts by weight of a flame retardant (tetrabromobisphenol A: TBBA) with n = 0 in formula () (total Br content is 13% by weight), stirred and dissolved in a 1:1 mixed solvent of methyl ethyl ketone and N,N'-dimethylformamide to a solid content of 60% by weight, and reacted with this. A varnish was prepared by adding cobalt octylate as a catalyst at a weight ratio of 300 ppm of cobalt ion to polyaromatic cyanate. This varnish was impregnated into a long 2116 type E glass cloth substrate (116E manufactured by Nitto Boseki Co., Ltd.) so that the solid content (polyaromatic cyanate and flame retardant) was 63% by weight. A prepreg was prepared by heating and drying under the following conditions. The gel time of this prepreg at 170°C was 60 seconds. The long belt-shaped prepreg thus produced was then wound into a roll. Next, these four prepregs are pulled out from the roll and stacked, and a long double-sided roughened copper foil with a thickness of 70μ is stacked on both sides of the top and bottom, and this is placed between the steel belts of the double belt as shown in Figure 1. The material was passed through the film continuously, and hot and pressure molding was performed while taking it off with a cooling roll. The molding conditions are heating temperature 200℃,
Molding pressure 25Kg/cm ² , molding time 2 minutes (feed rate 2
m/min). The laminate formed in this way between the steel belts is cooled for 40 minutes by cooling rolls.
Cooled under pressure at 140℃ with a pressure of Kg/ ^cm2 , then cut with a cutting device, and then heated in an electric oven at 230℃.
By performing after-curing for 2 hours, a double-sided copper-clad laminate for inner layer printed wiring boards with a thickness of 0.5 mm was obtained. Example 2 A 2116 type D glass cloth base material (manufactured by Nittobo Co., Ltd.) was used instead of a 2116 type E glass cloth base material as a base material.
A double-sided copper-clad laminate for an inner layer printed wiring board having a thickness of 0.5 mm was obtained by continuous molding and pressing in the same manner as in Example 1, except that the prepreg was created using WDX-723). Example 3 An inner layer printed wiring board was prepared by etching the copper foil of the double-sided copper-clad laminate obtained in Example 1 to form a circuit. These two inner-layer printed wiring boards are stacked with the two sheets of prepreg obtained in Example 1 interposed between them, and 18 μ thick copper foil is layered above and below with two sheets of prepreg interposed between them, and this is pinned. After positioning the layers using the lamination method, multi-stage press molding was performed at a molding temperature of 170°C, a molding pressure of 40 kg/cm ² , and a molding time of 90 minutes. After molding, the layers were placed in an electric oven for 230 min. C. for 2 hours to obtain a multilayer printed wiring board with a thickness of 2.0 mm and an 8-layer circuit configuration. Example 4 Eight layers with a thickness of 2.0 mm were prepared in the same manner as in Example 3, except that the inner layer printed wiring board made from the double-sided copper-clad laminate obtained in Example 2 was used, and the prepreg prepared in Example 2 was used. A multilayer printed wiring board with the following circuit configuration was obtained. Comparative Example 1 A polyimide resin varnish was prepared by dissolving polyamino bismaleimide resin (Kelimide 601 manufactured by Nippon Polyimide Co., Ltd.) in N-methyl-2-pyrrolidone so that the solid content was 60% by weight. This varnish was applied to the same D glass cloth substrate as in Example 2 with a resin content of 45%.
It was impregnated in an amount of % by weight and dried in the same manner as in Example 2 to prepare a prepreg. Next, 5 sheets of this prepreg were stacked together, and 70 μ thick double-sided roughened copper foil was stacked on both the top and bottom sides, and multi-stage press molding was performed at a molding temperature of 170°C, a molding pressure of 40 kg/cm ² , and a molding time of 90 minutes. Laminate molding was performed, and after-curing was carried out in an electric oven at 200° C. for 2 hours to obtain a double-sided copper-clad laminate with a thickness of 0.5 mm for an inner layer printed wiring board. By etching the copper foil of the double-sided copper-clad laminate obtained in this way to form a circuit, an inner layer printed wiring board was created, and two inner layer printed wiring boards were placed between each in the same manner as above. Layered through 3 sheets of prepreg, and layered with 3 more sheets of prepreg above and below.
By stacking 18μ thick copper foils, laminating them under the same conditions as above, and then post-curing them at 200℃ for 2 hours, we created a 2.0mm thick 8-layer circuit configuration with multilayer printed wiring. Got the board. Comparative Example 2 A varnish was prepared in the same manner as in Example 1 using only the polyaromatic cyanate (XU-71787 manufactured by Dow Chemical Company) used in Example 1 (no flame retardant was added), and the rest was carried out. A prepreg was prepared in the same manner as in Example 1, and laminated molding and after-curing were performed in the same manner as in Example 1 to obtain a double-sided copper-clad laminate having a thickness of 0.5 mm for an inner layer printed wiring board. Comparative Example 3 Using the same polyaromatic cyanate of formula (), formula () and flame retardant of formula () as in Example 1, 75 parts by weight of polyaromatic cyanate of formula () and flame retardant of formula () were used. 12.5 parts by weight of the flame retardant of formula () were taken (total Br content is 13% by weight), and these were mixed with methyl ethyl ketone, N,
A 1:1 mixed solvent of N'-dimethylformamide was stirred and dissolved so that the solid content was 60% by weight, and cobalt naphthenate was added thereto as a reaction catalyst at a weight ratio of 150 ppm of cobalt ions to the polyaromatic cyanate resin. A varnish was prepared. A prepreg was prepared by impregnating a 2116 type E glass cloth substrate with this varnish to a solid content of 45% by weight and drying it by heating at 150° C. for 4 minutes. Next, 5 sheets of this prepreg were stacked together, and 70 μ thick double-sided roughened copper foil was layered on both the top and bottom sides, and laminated molding was performed in a multistage press at a molding temperature of 170°C, a molding pressure of 40 kg/cm ² , and a molding time of 90 minutes. After molding, the product was after-cured in an electric oven at 230° C. for 2 hours to obtain a double-sided copper-clad laminate with a thickness of 0.5 mm for an inner layer printed wiring board. The electrical properties, thermal properties, etc. of the laminates of Examples 1 to 4 and Comparative Examples 1 to 3 obtained as described above were measured, and the results are shown in the following table.
In the following table, dielectric constant, dielectric loss tangent, flame resistance, and oven heat resistance were measured based on JIS C 6481. Moreover, the glass transition temperature was measured from the chart of the viscoelastic spectrum.

【table】

[Table] As seen in the results in the table, each example in which the insulating substrate was formed using aromatic polytriazine (polyaromatic cyanate resin) obtained by polymerizing polyaromatic cyanate was formed using polyimide resin. It is confirmed that the dielectric constant and dielectric loss tangent are lower than those of Comparative Example 1 in which an insulating substrate is formed, and the glass transition temperature and heat resistance temperature are also maintained at high levels. In each example in which a flame retardant was blended with group cyanate, the HB level was 94V-
It is confirmed that the flame retardancy increases to a level of 0.
Furthermore, as is clear from the comparison between Example 1 and Comparative Example 3, the resin of Example 1, which was manufactured using a continuous molding press to increase the resin content, was lower than the resin manufactured using a multistage press. It is confirmed that the dielectric constant can be lowered than that of Comparative Example 3, which has a lower content.

【Effect of the invention】

As mentioned above, in the present invention, prepregs prepared from a varnish prepared by blending a polyaromatic cyanate of the formula () with a flame retardant of the formula () and the formula () are laminated by lamination molding. Since the plate was manufactured, the high frequency properties of the laminate can be ensured due to the low dielectric constant and dielectric loss tangent of the polyaromatic cyanate polymer, and the high frequency properties of the laminate can be ensured by adding flame retardants. This makes it possible to increase the flame retardant grade of the laminate and maintain a high level of heat resistance. In addition, since the molding is carried out using a continuous molding press that heats and presses multiple sheets of the prepreg stacked together and continuously fed while being pulled off, the prepregs are prevented from slipping due to the tensile force applied when they are pulled off. This means that even if prepreg with a high resin content is used, molding can be carried out without the risk of slips occurring between the prepregs. It is possible to mold a laminate with a lower dielectric constant by using a prepreg with a high resin content and a higher resin content.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing a double-belt continuous molding method, and FIG. 2 is a schematic diagram showing a laminated structure for manufacturing a multilayer printed wiring board. 1 is a steel belt, 2 is a prepreg, 3 is a metal foil, and 4 is a laminate.

Claims (1)

[Claims] A polyaromatic cyanate represented by the primary formula (), (In the formula, Ar is aromatic. B is a _C7-20 polycyclic aliphatic group. D is each independently a substituent containing no active hydrogen.
q, r, and s are each independently an integer of 0, 1, 2, or 3, provided that the sum of q, r, and s is greater than or equal to 2. t is an integer from 0 to 4, each independently. x is a number from 0 to 5) A flame retardant represented by the following formula (), (In the formula, R and R' are aromatic or brominated aromatic substituents that do not contain active hydrogen. n is a positive number) A flame retardant represented by the following formula (), (In the formula, n is an integer of 0, 1 or 2) A varnish is prepared by blending a polyaromatic cyanate with a reaction catalyst, and a base material is impregnated with this varnish to create a long belt-shaped prepreg. A method for manufacturing a laminate, which comprises stacking a plurality of laminates, continuously feeding them while taking them, heating and pressurizing them to form a laminate.