JP2005123436A - Manufacturing method of multilayer printed wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide the manufacturing method of a multilayer printed wiring board where surface roughness is excellent and following property of resist is good, and which is effective for narrowing a line/space; and to provide the manufacturing method of the multilayer printed wiring board which contributes much for high density, thinning, reliability improvement and cost reduction of the multilayer printed wiring board without applying much more load than ever to environment. <P>SOLUTION: The manufacturing method obtains the multilayer printed wiring board by heating and pressing at least two kinds of respectively one or more adhesive sheets having the lowest melt viscosities different from each other. In the manufacturing method of the multilayer printed wiring board, the difference between the lowest melt viscosities of the respective adhesive sheets is ≥1,000 Pa s. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a multilayer printed wiring board.

  Conventionally, when manufacturing a multilayer printed wiring board, one or more prepreg sheets obtained by impregnating a glass cloth base material with an epoxy resin and semi-cured are stacked on an inner circuit board on which a circuit is formed, and a copper foil is further formed thereon. It has undergone a process of heat-integrated molding with a stacked hot plate press. In recent years, multilayering has progressed, and there has been a construction method in which multiple layers are electrically connected to each other through through holes. Further, a prepreg sheet is successively stacked thereon to form non-through connection holes. The so-called build-up wiring boards that are connected by the mainstream are becoming mainstream.

  At that time, as a method of embedding through-holes in the inner layer, from the method of using a hole-filling agent, for the purpose of reducing the number of man-hours and matching the thermal expansion coefficient with the insulating layer, for example, a build-up layer as disclosed in Patent Publication 1 is used. A method of filling a through-hole with an insulating layer is becoming widespread.

  On the other hand, in recent years, printed wiring boards are becoming narrower in distance between lines and spaces due to higher density, and high surface smoothness is required due to problems such as resist followability.

JP 2003-37362 A

  When the inner layer through hole is embedded with the resin of the buildup layer, the resin in the vicinity of the through hole flows into the through hole. As a result, the resin thickness on and around the through hole is 5 μm or more thinner than the surroundings. When the outer layer circuit is formed, there is a problem that the resist cannot be in close contact, a gap is formed between the resist and the copper foil, the etching solution penetrates there, and the line is cut off.

  Furthermore, in recent years, electrically insulating resins used for adhesive sheets have various functions such as high frequency compatibility and laser processing compatibility. For this reason, surface smoothness is becoming more and more important for impedance matching and for stabilizing the number of shots in laser processing.

The present invention relates to the following inventions.
(1) A method for producing a multilayer printed wiring board obtained by heating and pressing at least two adhesive sheets having different minimum melt viscosities.
(2) The method for producing a multilayer printed wiring board according to (1), wherein a thermosetting resin containing an electrically insulating filler is used for at least one of the adhesive sheets.
(3) The method for producing a multilayer printed wiring board according to (1) or (2), wherein the difference in minimum melt viscosity of each adhesive sheet is 1,000 Pa · s or more.
(4) The minimum melt viscosity of one of the adhesive sheets is in the range of 3,000 to 20,000 Pa · s, and the other is in the range of 300 to 10,000 Pa · s (1) The manufacturing method of the multilayer printed wiring board as described in (3)-(3).
(5) The method for producing a multilayer printed wiring board according to any one of (1) to (4), wherein at least one of the adhesive sheets uses a resin-coated copper foil.

  The multilayer printed wiring board manufactured according to the present invention is excellent in surface roughness, and therefore has good resist followability and is effective in narrowing the line / space. It can be manufactured with existing equipment and does not place a greater burden on the environment than ever before. Therefore, it greatly contributes to increasing the density, thickness, reliability, and cost of multilayer printed wiring boards.

  An object of the present invention is to control the flow of resin into the inner layer through-hole by using two types of adhesive sheets having different minimum melt viscosities. That is, the inner through hole can be selectively filled with a resin having a lower minimum melt viscosity. The resin having the lowest minimum melt viscosity is intended to form an insulating layer that retains the insulating layer and is more uniform and has less thickness variation.

  The difference in minimum melt viscosity between the two types of adhesive sheets is preferably 1,000 Pa · s or more. When the difference is less than 1,000 Pa · s, it tends to be difficult to selectively flow one adhesive sheet into the through hole. If the difference is 5,000 Pa · s or more, it is more preferable because the resin can flow more selectively.

  Further, the adhesive sheet used in the present invention may be an adhesive sheet having the same composition with different minimum melt viscosities. In this case, the difference in minimum melt viscosity is preferably 1,000 Pa · s or more, and more preferably 5,000 Pa · s or more.

  The method of controlling how the resin flows into the through hole can be realized by using the adhesive sheet as described above and adjusting the heating / pressurizing method. By using a two-stage pressurization method in which the pressurization time is adjusted to around the temperature at which the melt viscosity of the adhesive sheet becomes the minimum, a resin having a lower minimum melt viscosity can flow into the through hole. The heating method can be adjusted to the characteristics of the resin, and it may be heated to a holding temperature at a constant rate of temperature rise, or a two-stage heating method in which it is held in a certain temperature range may be used.

  The resin used in the present invention is a resin used for a prepreg based on a conventional glass cloth, and a thermosetting resin used for an adhesive film not containing a glass cloth base or an adhesive film with a copper foil. Can be used. The resin here means a resin, a curing agent, a curing accelerator, a coupling agent (if necessary), and a diluent (if necessary).

  Examples of the resin used in the present invention include, for example, epoxy resins, bistriazine resins, polyimide resins, phenol resins, melamine resins, silicon resins, unsaturated polyester resins, cyanate ester resins, isocyanate resins, polyimide resins or these resins. Various modified resins are preferred. Among these, bistriazine resin and epoxy resin are particularly preferable in terms of printed wiring board characteristics. As the epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, bisphenol A novolak type epoxy resin, salicylaldehyde novolak type epoxy resin, Bisphenol F novolac type epoxy resin, alicyclic epoxy resin, glycidyl ester type epoxy resin, glycidyl amine type epoxy resin, hydantoin type epoxy resin, isocyanurate type epoxy resin, aliphatic cyclic epoxy resin and their halides, hydrogenated products , And mixtures of the resins are preferred. Of these, bisphenol A novolac type epoxy resins or salicylaldehyde novolac type epoxy resins are preferred because of their excellent heat resistance.

  As the curing agent for the resin used in the present invention, those conventionally used can be used. When the resin is an epoxy resin, for example, dicyandiamide, bisphenol A, bisphenol F, polyvinylphenol, phenol novolac resin, bisphenol A novolac resin and Halides, hydrides, etc. of these phenol resins can be used. Of these, bisphenol A novolac resins are preferred because of their excellent heat resistance. The ratio of the curing agent to the resin is preferably in the range of 2 to 80 parts by weight with respect to 100 parts by weight of the resin. Furthermore, 2 to 5 parts by weight for dicyandiamide and 20 to 70 parts by weight for other curing agents. A range of parts is preferred.

  As the curing accelerator used in the present invention, when the resin is an epoxy resin, an imidazole compound, an organic phosphorus compound, a tertiary amine, a quaternary ammonium salt, or the like is used. The ratio of the curing accelerator to the resin is preferably in the range of 0.01 to 20 parts by weight and more preferably in the range of 0.1 to 1.0 part by weight with respect to 100 parts by weight of the resin.

  The thermosetting resin of the present invention can be diluted with a solvent and used as a resin varnish. As the solvent, acetone, methyl ethyl ketone, toluene, xylene, methyl isobutyl ketone, ethyl acetate, ethylene glycol monomethyl ether, methanol, ethanol, N, N-dimethylformamide, N, N-dimethylacetamide and the like can be used. The ratio of the diluent to the resin may be a ratio conventionally used, preferably 1 to 200 parts by weight, more preferably 30 to 100 parts by weight with respect to 100 parts by weight of the resin.

  Furthermore, in this invention, you may mix | blend a well-known coupling agent, a filler, etc. suitably with resin other than each above-described component as needed. In particular, when a filler is blended, the fluidity of the resin can be suppressed and the minimum melt viscosity can be easily adjusted.

  The filler used in the present invention is an electrically insulating filler. As the kind of filler, one or more kinds selected from aluminum borate, wollastonite, potassium titanate, basic magnesium sulfate, silicon nitride, silicon dioxide (silica), α-alumina and the like are used. be able to. Moreover, an organic filler etc. can also be used.

  When the blending amount of the electrically insulating filler in the resin is less than 5 parts by weight with respect to 100 parts by weight of the resin solids, this prepreg has poor handling properties such as the resin being finely broken and easily scattered during cutting. , When a wiring board is used, sufficient rigidity cannot be obtained. On the other hand, when the blending amount of the filler is 350 parts by weight or more, the hole filling property of the inner layer circuit at the time of hot pressing and the resin filling property between the circuits are impaired, and voids are formed in the filler composite resin layer after the hot pressing. Fading is likely to occur, and there is a risk of damaging the wiring board characteristics. Therefore, the blending amount of the filler is preferably 5 to 350 parts by weight with respect to 100 parts by weight of the resin solid content. Furthermore, it is excellent in filling the inner layer circuit and filling resin between the circuits, and the manufactured wiring board has the same or equivalent rigidity compared to the wiring board manufactured using the conventional glass cloth prepreg. From the reason that it can have dimensional stability and wire bonding property, the blending amount of the filler is more preferably 30 to 230 parts by weight with respect to 100 parts by weight of the resin solid content.

  Further, in order to further enhance the synthesis and heat resistance of the printed wiring board, a filler surface-treated with a coupling agent can be used, and the flowability and bonding property with the resin can be improved. As the coupling agent used at this time, known materials such as silicon, titanium, aluminum, zirconium, zircoaluminum, chromium, boron, phosphorus and amino acids can be used.

  The adhesive sheet of the present invention is obtained by impregnating a base material such as glass cloth or glass paper with a resin obtained by dispersing an electrically insulating filler in the thermosetting resin produced as described above, and heating the thermosetting resin. It is obtained by making the functional resin composition into a semi-cured state.

  In addition, the adhesive sheet of the present invention is obtained by applying the blended thermosetting resin composition to one side of a carrier film, making the thermosetting resin composition semi-cured by heating, and then removing the carrier film. It can also be obtained. As the carrier film at this time, a metal foil such as copper foil or aluminum foil, a polyester film, a polyimide film, a polyethylene terephthalate film, or a film obtained by treating the surface of the metal foil and film with a release agent can be used. .

Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples of the present invention, but the present invention is not limited thereto.
(Example 1)

<< Preparation of Adhesive Sheet A >>
A varnish obtained by diluting 100 parts by weight of a bisphenol A novolak type epoxy resin (epoxy equivalent 210) and 100 parts by weight of a bisphenol A novolak resin (epoxy equivalent 123) and 2 parts by weight of dicyandiamide as a curing accelerator with 80 parts by weight of MEK has an average diameter of 0. 8 μm, an average fiber length of 20 μm, and an aluminum borate whisker having a maximum length of 30 μm were blended so as to be 90 parts by weight with respect to 100 parts by weight of the resin solid content, and stirred until the aluminum borate whisker was uniformly dispersed in the varnish. .
The varnish was applied to a copper foil having a thickness of 18 μm and a polyethylene terephthalate (PET) film having a thickness of 50 μm with a knife coater, followed by heating and drying at a temperature of 150 ° C. for 10 minutes to remove the solvent and the thermosetting resin. Is semi-cured, and the insulating material with copper foil having a whisker volume fraction of 30% and the thickness of the insulating layer made of epoxy resin in a semi-cured state with the whisker and PET is removed by peeling, and the semi-cured state An adhesive film having a thickness of 50 μm made of an epoxy resin was prepared. The resin applied to PET is peeled off and the minimum melt viscosity is measured.
(Measurement equipment: Rheometric Scientific FC rheometer ARES-2K STD-FCO, heating method, heating rate 5.0 ° C / min), it was 8,300 Pa · s.
<< Preparation of adhesive sheet B >>
A varnish diluted with 100 parts by weight of a bisphenol A novolac type epoxy resin (epoxy equivalent 210) and 100 parts by weight of a bisphenol A novolak resin (epoxy equivalent 123) and 1 part by weight of dicyandiamide as a curing accelerator with 150 parts by weight of MEK has an average diameter of 0. The 8 μm silica filler was stirred until the compounded silica filler was uniformly dispersed in the varnish so that the amount was 90 parts by weight with respect to 100 parts by weight of the resin solid content.
This resin is impregnated into a glass cloth (# 1080) with a nominal thickness of 0.06 mm, dried by heating at a temperature of 150 ° C. for 6 minutes, the solvent is removed, and the thermosetting resin is semi-cured to obtain a filler volume fraction. A prepreg made of epoxy resin in a semi-cured state with a filler at 30% was produced. The minimum melt viscosity of this prepreg was measured (measuring instrument is the same as above) and found to be 700 Pa · s.
Further, a double-hole copper clad laminate having an insulating layer thickness of 0.2 mm and a conductor copper foil thickness of 18 μm was drilled at a predetermined position with a diameter of 0.2 mm to produce a through hole. After performing plating treatment with a thickness of 15 μm, adhesive sheets A and B are placed on both sides of the inner circuit board produced by removing unnecessary portions of the copper foil on both sides by etching so that the insulating resin side faces the inner circuit Multi-layer copper with inner layer circuit by heating and pressurizing for 90 minutes at a temperature rise rate of 3.0 ° C / min, 170 ° C, 3 MPa using a press through an 18 µm copper foil outside the adhesive B A tension laminate was obtained. The pressurization timing at this time was 35 minutes after the start of pressing, and the temperature at this time was 133 ° C.
(Example 2)

<< Preparation of Adhesive Sheet A >>
A varnish obtained by diluting 100 parts by weight of a bisphenol A novolak type epoxy resin (epoxy equivalent 210) and 100 parts by weight of a bisphenol A novolak resin (epoxy equivalent 123) with 2 parts by weight of dicyandiamide as a curing accelerator with 80 parts by weight of MEK has an average diameter of 0. 8 μm, an average fiber length of 20 μm, and an aluminum borate whisker having a maximum length of 30 μm were blended so as to be 90 parts by weight with respect to 100 parts by weight of the resin solid content, and stirred until the aluminum borate whisker was uniformly dispersed in the varnish. .
The varnish was applied to a copper foil having a thickness of 18 μm and a polyethylene terephthalate (PET) film having a thickness of 50 μm with a knife coater, followed by heating and drying at a temperature of 150 ° C. for 10 minutes to remove the solvent and the thermosetting resin. Is semi-cured, and the insulating material with copper foil having a whisker volume fraction of 30% and the thickness of the insulating layer made of epoxy resin in a semi-cured state with the whisker and PET is removed by peeling, and the semi-cured state An adhesive film having a thickness of 50 μm made of an epoxy resin was prepared. The resin applied to PET is peeled off and the minimum melt viscosity is measured.
(Measurement equipment: Rheometric Scientific FC rheometer ARES-2K STD-FCO, heating method, heating rate 5.0 ° C / min), it was 8,300 Pa · s.
<< Preparation of adhesive sheet B >>
Average diameter of varnish diluted with 100 parts by weight of bisphenol A novolac type epoxy resin (epoxy equivalent 210) and 100 parts by weight of bisphenol A novolak resin (epoxy equivalent 123), 1.5 parts by weight of dicyandiamide as a curing accelerator with 80 parts by weight of MEK 0.8 μm, average fiber length 20 μm, maximum length 30 μm aluminum borate whisker is blended so that it becomes 90 parts by weight with respect to 100 parts by weight of resin solid content until aluminum borate whisker is uniformly dispersed in varnish Stir.
The varnish was applied to a copper foil having a thickness of 18 μm and a polyethylene terephthalate (PET) film having a thickness of 50 μm with a knife coater, followed by heating and drying at a temperature of 150 ° C. for 10 minutes to remove the solvent and the thermosetting resin. Is semi-cured, and the insulating material with copper foil having a thickness of 80 μm and the insulating layer made of epoxy resin in a semi-cured state with the whisker volume fraction of 30% is removed by peeling, and the semi-cured state An adhesive film having a thickness of 80 μm made of an epoxy resin was prepared. The resin applied to PET is peeled off and the minimum melt viscosity is measured.
(Measuring instrument: Rheometric Scientific FC rheometer ARES-2K STD-FCO, heating method, heating rate 5.0 ° C / min), it was 6,300 Pa · s.
Further, a double-hole copper clad laminate having an insulating layer thickness of 0.2 mm and a conductor copper foil thickness of 18 μm was drilled at a predetermined position with a diameter of 0.2 mm to produce a through hole. After performing plating treatment with a thickness of 15 μm, adhesive sheets A and B are placed on both sides of the inner circuit board produced by removing unnecessary portions of the copper foil on both sides by etching so that the insulating resin side faces the inner circuit Multi-layer copper with inner layer circuit by heating and pressurizing for 90 minutes at a temperature rise rate of 3.0 ° C / min, 170 ° C, 3 MPa using a press through an 18 µm copper foil outside the adhesive B A tension laminate was obtained. The pressurization timing at this time was 35 minutes after the start of pressing, and the temperature at this time was 133 ° C.
(Example 3)

<< Preparation of Adhesive Sheet A >>
A varnish obtained by diluting 100 parts by weight of bisphenol A novolac type epoxy resin (epoxy equivalent 210) and 100 parts by weight of bisphenol A novolak resin (epoxy equivalent 123) with 2 parts by weight of dicyandiamide as a curing accelerator with 80 parts by weight of MEK has an average diameter of 0. 8 μm, an average fiber length of 20 μm, and an aluminum borate whisker having a maximum length of 30 μm were blended so as to be 90 parts by weight with respect to 100 parts by weight of the resin solid content, and stirred until the aluminum borate whisker was uniformly dispersed in the varnish. .
The varnish was applied to a copper foil having a thickness of 18 μm and a polyethylene terephthalate (PET) film having a thickness of 50 μm with a knife coater, and dried by heating at a temperature of 150 ° C. for 20 minutes to remove the solvent, and the thermosetting resin. Is semi-cured, and the insulating material with copper foil having a whisker volume fraction of 30% and the thickness of the insulating layer made of epoxy resin in a semi-cured state with the whisker and PET is removed by peeling, and the semi-cured state An adhesive film having a thickness of 50 μm made of an epoxy resin was prepared. The resin applied to PET is peeled off and the minimum melt viscosity is measured.
(Measuring instrument: Rheometric Scientific FC rheometer ARES-2K STD-FCO, heating method, heating rate 5.0 ° C / min), it was 16,700 Pa · s.
<< Preparation of adhesive sheet B >>
A varnish diluted with 100 parts by weight of a bisphenol A novolac type epoxy resin (epoxy equivalent 210) and 100 parts by weight of a bisphenol A novolak resin (epoxy equivalent 123) and 1 part by weight of dicyandiamide as a curing accelerator with 150 parts by weight of MEK has an average diameter of 0. The 8 μm silica filler was stirred until the compounded silica filler was uniformly dispersed in the varnish so that the amount was 90 parts by weight with respect to 100 parts by weight of the resin solid content.
This resin is impregnated into a glass cloth (# 1080) with a nominal thickness of 0.06 mm, dried by heating at a temperature of 150 ° C. for 6 minutes, the solvent is removed, and the thermosetting resin is semi-cured to obtain a filler volume fraction. A prepreg made of an epoxy resin in a semi-cured state with a filler at 30% was produced. The minimum melt viscosity of this prepreg was measured (measuring instrument is the same as above) and found to be 700 Pa · s.
Further, a double-hole copper-clad laminate with an insulating layer thickness of 0.2 mm and a conductor copper foil thickness of 18 μm was drilled at a predetermined position with a diameter of 0.2 mm to produce a through hole. After performing plating treatment with a thickness of 15μm, adhesive sheets A and B are placed on both sides of the inner circuit board produced by removing unnecessary portions of the copper foil on both sides by etching so that the insulating resin side faces the inner circuit Multi-layered copper with inner layer circuit by heating and pressurizing for 90 minutes under the conditions of a heating rate of 3.0 ° C / min, 170 ° C and 3 MPa using a press through an 18 µm copper foil outside the adhesive B A tension laminate was obtained. The pressurization timing at this time was 35 minutes after the start of pressing, and the temperature at this time was 133 ° C.
(Comparative Example 1)

In Example 1, a multilayer copper-clad laminate with an inner layer circuit was obtained in the same manner as in Example 1 except that the pressurization timing at the time of heating and pressing was set immediately after the start of pressing.
(Comparative Example 2)

  In Example 1, except that the adhesive sheet A was stacked on both sides of the internal circuit board so that the insulating layer resin side faced the internal circuit, the other layer copper-clad laminate containing the internal circuit was formed in the same manner as in Example 1. Obtained.

About the 4-layer shield board obtained by the above each Example and the comparative example, the surface roughness was measured with the stylus type surface roughness meter. The measurement location was the outer surface of the outer layer on a straight line of 10 mm in length, including the portion with and without the inner layer through-hole immediately below.
Moreover, the outer layer circuit was formed about the obtained 4 layer shield board, and the missing of the line after circuit processing was confirmed.
Furthermore, the cross section of the obtained four-layer shield plate was observed, and the resin flowing into the inner layer through-hole was confirmed. The above measurement results are shown in Table 1.

Claims (5)

A method for producing a multilayer printed wiring board obtained by heating and pressing at least two adhesive sheets having different minimum melt viscosities. The method for producing a multilayer printed wiring board according to claim 1, wherein a thermosetting resin containing an electrically insulating filler is used for at least one of the adhesive sheets. The method for producing a multilayer printed wiring board according to claim 1 or 2, wherein the difference in minimum melt viscosity of each adhesive sheet is 1,000 Pa · s or more. The minimum melt viscosity of either one of the adhesive sheets is in the range of 3,000 to 20,000 Pa · s, and the other is in the range of 300 to 10,000 Pa · s. The manufacturing method of the multilayer printed wiring board as described. The method for producing a multilayer printed wiring board according to claim 1, wherein at least one of the adhesive sheets uses a copper foil with resin.