JP2005178118A - Laminated sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a copper clad laminated sheet which enhances the heat resistance level of a printed wiring board using the copper clad laminated sheet and causes no trouble such as a blister or the like at the time of a reflow process. <P>SOLUTION: In the copper clad laminated sheet constituted by superposing a prepreg. which is impregnated with a thermosetting resin and dried, and a base material one upon another to heat and press them, the prepreg before heated and pressed is subjected to dehumidification treatment for 15-120 min at 0-45°C under an atmospheric pressure of 7×10<SP>4</SP>-10×10<SP>4</SP>Pa. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a laminated board.

  As electronic devices have become smaller and more multifunctional in recent years, printed circuit boards have become denser and smaller, and paper-based phenolic resin copper-clad laminates have improved punchability and drillability. Because it is excellent and inexpensive, it is widely used as a printed wiring board substrate for consumer electronic devices. A paper base phenolic resin laminate is a prepreg obtained by reacting phenols and aldehydes in the presence of an alkali catalyst to obtain a phenol resin, adjusting the phenol resin with a solvent, and impregnating and drying the paper base material. It is manufactured by heating and pressing a predetermined number of sheets. Usually, a prepreg and copper foil are combined to form a copper-clad laminate, and the copper foil is etched to form a circuit to be a printed wiring board.

  In addition, set manufacturers are considering or adopting solder that does not use lead, which is a hazardous substance (lead-free solder), due to increased awareness of environmental protection. However, lead-free solder has a higher melting temperature than conventional lead-containing solder (Sn-Pb), and therefore the set temperature during the reflow process tends to be higher, improving the heat resistance of the printed wiring board, In particular, improvement in heat resistance in the reflow process is required.

A resin composition obtained by reacting a reaction product obtained by reacting a mixture of a phenol compound and urea with a xylene resin in the presence of an acid catalyst with formaldehyde, for example, in JP-A-2002-145975 and the like. A method for obtaining a paper-based copper clad laminate excellent in heat resistance, moisture resistance, punching workability and flame retardancy is disclosed.
JP 2002-145975 A

  Paper-based phenolic resin copper-clad laminates are widely used because they are inexpensive, but they have a lower heat resistance level than glass-based epoxy resin copper-clad laminates, so the temperature during the reflow process The setting is also set low, and problems such as blistering occur when the temperature setting is high. The main cause of blistering during the reflow process is gas (moisture) generated from the base material.

  In general, a paper base phenolic resin copper clad laminate is manufactured by storing a prepreg impregnated and dried with a phenolic resin on a paper base and heating and pressurizing it for a certain period (0 to 14 days). During this prepreg storage period, the base material absorbs moisture, and even in the subsequent heating and pressurizing process, the absorbed moisture is not completely removed and remains, so that it was exposed to a high temperature such as a reflow process. Occasionally, problems such as blistering occur due to the rapid expansion and volatilization of moisture.

  Storage for a certain period of time (0 to 14 days) after prepreg manufacture is indispensable for steady operation of the manufacturing process and uniform quality. Recently, solder used in the reflow process has been changed from conventional Sn-Pb solder to lead-free solder due to environmental problems. Lead-free solder has a melting temperature higher than that of Sn-Pb solder. Therefore, when using lead-free solder, the temperature setting in the reflow process is also set high, so printed wiring boards using paper-based phenolic resin copper-clad laminates are prone to problems such as blistering. An object of the present invention is to provide a copper-clad laminate that improves the heat resistance level of a printed wiring board using the copper-clad laminate and does not cause problems such as blistering during the reflow process.

The present invention relates to the following.
(1) In a laminated plate obtained by laminating a prepreg impregnated and dried with a thermosetting resin on a base material and heating and pressing, the prepreg before heating and pressurizing is 7 × 10 ⁴ Pa or more and 10 × 10 ⁴ Pa or less. A laminated board, which is dehumidified at a temperature of 0 to 45 ° C. for 15 to 120 minutes.
(2) The laminate according to (1), wherein the thermosetting resin is a phenol resin.

According to the present invention, in a laminate obtained by laminating and drying a prepreg impregnated and dried with a phenol resin on a base material, the prepreg before heating and pressurization is 7 × 10 ⁴ Pa or more and 10 × 10 ⁴ Pa or less. By performing dehumidification treatment for 15 to 120 minutes at a temperature of 0 to 45 ° C. under atmospheric pressure, a laminate having excellent reflow heat resistance can be obtained.

In the present invention, a base material is impregnated with a thermosetting resin and dried to produce a prepreg, and after the production, the prepreg several days later is used at a pressure of 7 × 10 ⁴ Pa or more and 10 × 10 ⁴ Pa or less using a vacuum tank or the like. Below, dehumidify at a temperature of 0 to 45 ° C. for 15 to 120 minutes. After the treatment is completed, a predetermined number of prepregs are stacked and heated and pressed to produce a laminate. The base material used in the present invention can be any base material generally used for prepreg, such as paper base material, glass cloth, glass nonwoven fabric, and aramid fiber. Paper substrates are preferred. As the paper substrate, kraft paper, cotton linter paper, mixed paper of linter and kraft pulp, mixed paper of glass fiber and paper fiber, etc. can be used.

The method for dehumidifying the prepreg uses a vacuum tank in the above. However, if a pressure state of 7 × 10 ⁴ Pa or more and 9.5 × 10 ⁴ Pa or less is possible, for example, the prepreg is made of an aluminum bag, It may be put in a plastic bag, sucked using a pump or the like, and decompressed. Note that the degree of pressure reduction during the dehumidification process is 7 × 10 ⁴ Pa or more. This is because if it is less than 7 × 10 ⁴ Pa, the prepreg has little dehumidifying effect and the effect cannot be obtained. Moreover, since the dehumidifying effect is obtained by reducing the pressure from atmospheric pressure (10.13 × 10 ⁴ Pa), it is performed at 10 × 10 ⁴ Pa or less.

  The dehumidification treatment time is 15 to 120 minutes, preferably 20 to 60 minutes. If it is less than 15 minutes, the time is short and the prepreg dehumidification is incomplete. If the treatment is performed for more than 120 minutes, the volatile components of the prepreg become too small, the fluidity of the resin is lowered, and after heating and pressurization, defects such as scraping occur on the laminate. The dehumidifying temperature is 0 to 45 ° C., preferably 15 to 35 ° C. If it is less than 0 ° C., the temperature is too low, the prepreg freezes, and the dehumidifying effect cannot be obtained. If the temperature exceeds 45 ° C., the resin of the semi-cured prepreg is cured, and after heating and pressurization, defects such as scraping occur in the laminate.

  Examples of the thermosetting resin used in the present invention include an epoxy resin, a melamine resin, an unsaturated polyester resin, a polyimide resin, and the like, but a vegetable oil-modified phenol resin is preferable because it is inexpensive. The vegetable oil-modified phenol resin is obtained by reacting phenols and vegetable oil in the presence of an acid catalyst, and then reacting aldehydes in the presence of an alkali catalyst. Examples of the acid catalyst include p-toluenesulfonic acid. Examples of the alkali catalyst include amine catalysts such as ammonia, trimethylamine, and triethylamine.

  As the vegetable oil to be used, it is preferable to use dry oil, and examples thereof include paulownia oil, linseed oil, dehydrated castor oil, and deer oil. As phenols, phenol, metacresol, paracresol, orthocresol, isopropylphenol, nonylphenol and the like are used. Examples of aldehydes include formaldehyde, paraformaldehyde, acetaldehyde, paraacetaldehyde, butyraldehyde, octylaldehyde, benzaldehyde and the like, and are not particularly limited. In general, formaldehyde or paraformaldehyde is used.

  A phenol resin composition using a phenol resin preferable as a thermosetting resin is adjusted with a solvent, dissolved or dispersed, and impregnated into a base material as a varnish. You may process with a water-soluble phenol resin or water-soluble melamine resin in the step before impregnating a phenol resin. Various plasticizers and flame retardants may be added to the varnish in order to impart plasticity and flame retardancy to the phenol resin laminate. The above varnish is impregnated and dried into a paper base material to obtain a prepreg. After the obtained prepreg is dehumidified, a predetermined number of layers are stacked, and copper foil is stacked thereon, and heated at a temperature of 150 to 180 ° C. and a pressure of 9 to 20 MPa. Pressurize to make a paper base phenolic resin copper clad laminate.

EXAMPLES Next, although an Example demonstrates this invention concretely, this invention is not limited to these.
(Synthesis of phenolic resin for top coating)
150 parts by weight of paulownia oil, 280 parts by weight of phenol, and 0.2 parts by weight of p-toluenesulfonic acid are charged in a reaction kettle, reacted at 90 ° C. for 1 hour, and then 200 parts by weight of paraformaldehyde and 30 parts by weight of 28% by weight ammonia water are added. And reacted at 75 ° C. for 2 hours to obtain a tung oil-modified resole resin having a tung oil modification rate of 35% by weight. To 100 parts by weight of tung oil-modified resole resin, 15 parts by weight of melamine-modified phenol resin and 35 parts by weight of triphenyl phosphate shown in Table 1 were dissolved with a solvent to obtain a varnish having a resin content of 50% by weight.

(Synthesis of water-soluble phenol resin)
1 mol of phenol and 37 wt% formalin were reacted with 1.2 mol of formaldehyde and 0.4 mol of triethylamine aqueous solution (concentration: 30 wt%) at 70 ° C for 6 hours to obtain a water-soluble phenol resin. . The obtained water-soluble phenol resin was diluted with a mixed solvent of water 1 to methanol 1 in a weight ratio to obtain a water-soluble phenol resin having a solid content of 12% by weight.

First, water-soluble phenolic resin was attached to kraft paper having a thickness of 0.2 mm and a basis weight of 125 g / m ² so that the amount of adhesion was 18% by weight, and then the phenolic resin varnish for top coating was dried. A prepreg was obtained by impregnation and drying so that the total resin adhesion amount was 50% by weight.

As shown in Table 1, 10 obtained prepregs were put in an aluminum bag and stored for several days. Immediately before the manufacture of the copper-clad laminate, the prepreg was dehumidified at a temperature of 30 ° C. for a certain period of time (15 to 120 minutes) under an air pressure of 7 × 10 ⁴ Pa, and the treated prepregs were stacked, A thickness of 1.6 mm obtained by stacking copper foil with an adhesive having a thickness of 35 μm on both sides so that the adhesive layer is on the prepreg side and heating and pressing at a temperature of 170 ° C. and a pressure of 15 MPa for 90 minutes. These single-sided copper clad laminates were designated as Examples 1 to 4.

(Comparative example)
Comparative Examples 1 and 2 were double-sided copper clad laminates having a thickness of 1.6 mm obtained in the same manner as in the Examples except that the prepreg was not subjected to dehumidification.

The single-sided copper-clad laminate obtained above was evaluated for heat resistance and punchability. The results are shown in Table 1. The test method was as follows.
(1) The heat resistance evaluation was performed in accordance with JIS C 6481, and the solder heat resistance at 260 ° C. for 30 seconds and the heat resistance in a constant temperature bath at 200 ° C. for 40 minutes were evaluated. Problems such as base blistering and copper foil blistering were observed visually.
○: No blistering occurred, ×: Blistering occurred (2) Punching workability changes the surface temperature (60 ° C, 70 ° C, 80 ° C) of the test piece, punch diameter 1.0 to 1.2 mm, between holes Punching was performed using a test mold with a pitch of 2.54 mm and 24 holes. The area around the hole in the punched specimen was visually observed, and the state was indicated by symbols.
○: No peeling white, Δ: Some peeling white, ×: White peeling (3) Reflow heat resistance is formed by etching a circuit with a residual copper ratio of 70% and a reflow peak temperature of 250 ° C. (base material) Surface temperature), a reflow furnace set at a temperature range of 230 ° C. or higher for 45 seconds was passed once to twice, and defects such as base blistering and copper foil blistering were observed visually.
○: No blistering occurred, ×: Blistering occurred

As shown in Table 1, in the examples, problems such as base blistering and copper foil blistering did not occur at all, and the heat resistance and reflow heat resistance were higher than in the comparative example in which the prepreg was not dehumidified. Are better. Therefore, according to the present invention, a printed wiring board having excellent reflow heat resistance and the like can be obtained.

Claims (2)

In a laminate obtained by laminating and drying a prepreg impregnated and dried with a thermosetting resin on a base material, the prepreg before heating and pressurization is set to 0 under an atmospheric pressure of 7 × 10 ⁴ Pa or more and 10 × 10 ⁴ Pa or less. A laminate comprising a dehumidifying treatment at a temperature of ˜45 ° C. for 15 to 120 minutes. The laminated board according to claim 1, wherein the thermosetting resin is a phenol resin.