JP2006102753A - Thermosetting flux, flux sheet, and multilayer printed circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermosetting flux, which can surely carry out a solder joining operation, and does not need to remove the remaining flux by washing after the solder joining operation, and can keep the electric insulation resistance even in a hot and moist atmosphere, and is excellent in the dielectric characteristic, and can achieve a highly reliable solder joining, and further to provide a flux sheet and a multilayer printed circuit board. <P>SOLUTION: The thermosetting flux serving as a flux in the solder joining operation contains a resin (A) having a phenolic hydroxy group, a resin (B) serving as a hardening agent for the resin (A), and a cyclo-olefinic resin (C). The multilayer printed circuit board has interlayer joined portions joined by the solder joining operation through the thermocompression bonding of heating and pressing a joining layer and a layer to be joined via a flux layer composed of the thermosetting flux, the joining layer having wiring patters, conductor posts formed on the wiring patterns, and solder layers formed on the surfaces of the tip ends of the conductor posts, and the layer to be joined having interlayer joining lands for the conductor posts. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a thermosetting flux, a flux sheet, and a multilayer wiring board.

  Solder bonding is used for electrical and mechanical connections in most electronic components and electronic devices. In recent years, as the concern for the environment has increased worldwide, efforts to make these electronic components and electronic devices lead-free are spreading in the semiconductor industry and the electronic equipment industry. Under these circumstances, the biggest problem for semiconductor packages is that the reflow temperature required for joining lead-free products is higher than that of conventional solder joints using tin-lead eutectic solder, and this maximum value is In general, the temperature is set to 260 ° C. This means that all components mounted on the semiconductor mounting substrate are exposed to the melting point of lead-free solder, and there is a need for packaging materials with high heat resistance and low water absorption that can cope with higher reflow temperatures. It has been.

  On the other hand, conventionally, a soldering flux characterized by containing a thermosetting resin, an activator, and a solvent is known (for example, see Patent Document 1). In a reflow profile with a high temperature, voids may occur during solder bonding unless processing such as drying before reflow is performed strictly. Even if the bonding is achieved without problems, there is a possibility that problems such as swell due to a moisture absorption heat resistance test with a lead-free reflow profile, and adhesion interface peeling may occur.

  Also, in recent use of electronic equipment, high-speed transmission is performed for information transmission, and deterioration of electrical signals is a problem in high-speed transmission, and in particular, due to the dielectric properties of the interlayer insulating material of multilayer wiring boards. The resulting dielectric loss is significantly degraded when the electric signal frequency is increased. Therefore, in order to solve this problem, a countermeasure is required for the insulating material. This is because the epoxy resin or polyimide resin that has been used as an insulating material for electronic parts such as wiring boards may have insufficient electrical characteristics such as dielectric constant and dielectric loss tangent, and is compatible with high-speed transmission. Is difficult.

JP-A-8-90283

  The present invention enables reliable solder bonding, and does not require cleaning and removal of residual flux after solder bonding, maintains electrical insulation even in high temperature and high humidity atmospheres, and has excellent dielectric characteristics and high reliability. An object of the present invention is to provide a thermosetting flux, a flux sheet, and a multilayer wiring board that can be used.

That is, the present invention
1. A thermosetting flux that acts as a flux at the time of soldering, comprising a resin (A) having a phenolic hydroxyl group, a resin (B) that is a curing agent of the resin, and a cyclic olefin resin (C) Thermosetting flux,
2. The thermosetting flux according to item 1, wherein the cyclic olefin-based resin includes a norbornene-based resin,
3. The thermosetting flux according to item 2, wherein the norbornene-based resin is an addition polymer of a norbornene monomer.
4). The thermosetting flux according to the second or third item, wherein the norbornene-based resin has a repeating unit represented by the following general formula (1):

[X in Formula (1) represents —O—, —CH ₂ — or —CH ₂ CH ₂ —, and R ₁ , R ₂ , R ₃ and R ₄ are each hydrogen, an alkyl group, cyclo A group selected from an alkyl group, a vinyl group, an alkenyl group, an alkynyl group, an alkylidenyl group, an aryl group, an aralkyl group, a silyl group, an ester group, an ether group, a (meth) acryl group, and an epoxy group. These groups are alkyl groups. They may be bonded via a group, an ether group or an ester group, and may be the same or different. m is an integer of 10 to 10000, and n is an integer of 0 to 5. ]

5). The thermosetting flux according to any one of Items 2 to 4, wherein the norbornene-based resin is an addition copolymer of a monomer represented by the following general formula (2):

[X in Formula (1) represents —O—, —CH ₂ — or —CH ₂ CH ₂ —, and R ₁ , R ₂ , R ₃ and R ₄ are each hydrogen, an alkyl group, cyclo A group selected from an alkyl group, a vinyl group, an alkenyl group, an alkynyl group, an alkylidenyl group, an aryl group, an aralkyl group, a silyl group, an ester group, an ether group, a (meth) acryl group, and an epoxy group. These groups are alkyl groups. They may be bonded via a group, an ether group or an ester group, and may be the same or different. m is an integer of 10 to 10000, and n is an integer of 0 to 5. ]

6). The thermosetting flux according to any one of Items 1 to 5, wherein the resin (A) having a phenolic hydroxyl group is at least one selected from phenolphthaline and dihydroxybenzoic acid,
7). A flux sheet comprising a flux layer made of the thermosetting flux according to any one of items 1 to 6, and at least one protective film layer that can be peeled off,
8). A connection layer having a wiring pattern, a conductor post formed on the wiring pattern, a solder layer formed on a front end surface of the conductor post, and a connected layer having a land for interlayer connection with the conductor post; A multilayer wiring board having an interlayer connection portion soldered by heating and pressurizing and thermocompression bonding through a flux layer made of the thermosetting flux according to any one of items 1 to 6;
9. The multilayer wiring board according to claim 8, wherein the flux layer is obtained by laminating the flux sheet according to claim 7.
Is to provide.

  According to the present invention, it is possible to surely perform solder bonding at the time of mounting a semiconductor chip and solder bonding such as interlayer connection of a multilayer wiring board, and it is not necessary to clean and remove residual flux after solder bonding, and a high temperature, high humidity atmosphere. However, it is possible to obtain a good bond that retains electrical insulation, has excellent dielectric characteristics, and is highly reliable.

The present invention is a thermosetting flux that acts as a flux during solder joining, and includes a resin (A) having a phenolic hydroxyl group, a resin (B) that is a curing agent of the resin, and a cyclic olefin resin (C). It is the thermosetting flux characterized by this.
The thermosetting flux of the present invention acts as a flux at the time of solder bonding, and then cures by heating to act as an adhesive between layers. Moreover, the thermosetting flux of the present invention removes oxides on the solder-bonded metal surface and the solder surface at the time of soldering, retains electrical insulation even at high temperature and high humidity, and has excellent dielectric properties. Enables reliable and good bonding.
Furthermore, the thermosetting flux of the present invention does not need to be removed by washing after soldering, and is heated as it is to become a three-dimensionally cross-linked resin, which has excellent adhesion, multilayer wiring boards, semiconductor elements and multilayers. Acts as an adhesive between layers such as wiring boards. Further, the flux sheet using this has good sheet properties in the uncured state of the thermosetting flux.
In addition, a connection layer having a wiring pattern, a conductor post formed on the wiring pattern, a solder layer formed on the front end surface of the conductor post, and a land to be connected to the conductor post having an interlayer connection land In a multilayer wiring board having an interlayer connection part which is soldered by heating and pressurizing and thermocompression bonding the layer, the connection layer and the connection layer are connected via a flux layer made of the thermosetting flux. By bonding, it is possible to obtain a multilayer wiring board having solder bonding that maintains electrical insulation even in a high temperature and high humidity atmosphere, has excellent dielectric characteristics, and has high reliability.

  Among the cyclic olefin-based resins, norbornene-based resins are generally characterized by low hygroscopicity because their main chain skeleton has an alicyclic structure. Thereby, since the water absorption rate of the sheet | seat single body before hardening can be lowered | hung, the void generation | occurrence | production at the time of high temperature at the time of soldering using the curable flux of this invention can be suppressed. In addition, a cured product with low water absorption can be obtained even after heat curing, avoiding problems such as interfacial debonding, blistering, joint damage, popcorn cracking, etc. due to a reflow heat resistance test after moisture absorption treatment in a high temperature and high humidity atmosphere. be able to.

  The cyclic olefin resin used in the present invention includes, as cyclic olefin monomers, for example, monocyclic compounds such as cyclohexene and cyclooctene, norbornene, norbornadiene, dicyclopentadiene, dihydrodicyclopentadiene, tetracyclododecene, tricyclopentadiene, dihydrotricyclohexane. Polymerized from polycyclic compounds such as pentadiene, tetracyclopentadiene and dihydrotetracyclopentadiene.

  Such polymers of cyclic olefin monomers include, for example, (co) polymers of cyclic olefin monomers, copolymers of cyclic olefin monomers and other monomers capable of copolymerization such as α-olefins, and the like. And hydrogenated products of the copolymer. Examples of these known polymers include random copolymers, block copolymers, and alternating copolymers. These cyclic olefin-based resins can be produced by a known polymerization method, and examples of the polymerization method include an addition polymerization method and a ring-opening polymerization method. Of these, polymers obtained by polymerizing norbornene-type monomers (particularly addition (co) polymerization) are preferred, but the present invention is not limited thereto.

  Examples of addition polymers of cyclic olefin resins include (1) addition (co) polymers of norbornene monomers obtained by addition (co) polymerization of norbornene monomers, (2) norbornene monomers and ethylene or α- Addition copolymers with olefins, (3) addition copolymers with norbornene-type monomers and non-conjugated dienes, and other monomers as required. These resins can be obtained by all known polymerization methods.

Such an addition polymer of a cyclic olefin resin is obtained by coordination polymerization or radical polymerization using a metal catalyst. Among them, in coordination polymerization, a polymer is obtained by polymerizing monomers in a solution in the presence of a transition metal catalyst (NiCOLE R. GROVE et al. Journal of Polymer Science: part B, Polymer Physics, Vol. 1). 37, 3003-3010 (1999)).
Representative nickel and platinum catalysts as metal catalysts for coordination polymerization are described in PCT WO 9733198 and PCT WO 00/20472. Examples of metal catalysts for coordination polymerization include (toluene) bis (perfluorophenyl) nickel, (mesylene) bis (perfluorophenyl) nickel, (benzene) bis (perfluorophenyl) nickel, bis (tetrahydro) bis ( Known metal catalysts such as perfluorophenyl) nickel, bis (ethyl acetate) bis (perfluorophenyl) nickel, and bis (dioxane) bis (perfluorophenyl) nickel may be mentioned.

The radical polymerization technique is described in Encyclopedia of Polymer Science, John Wiley & Sons, 13, 708 (1998).
Generally, in radical polymerization, the temperature is raised to 50 ° C. to 150 ° C. in the presence of a radical initiator, and the monomer is reacted in a solution. Examples of the radical initiator include azobisisobutyronitrile (AIBN), benzoyl peroxide, lauryl peroxide, azobisisocapronitrile, azobisisoleronitrile, t-butyl hydrogen peroxide, and the like.

  Examples of the ring-opening polymer of the cyclic olefin-based resin include (4) a ring-opening (co) polymer of a norbornene-type monomer, and a resin obtained by hydrogenating the (co) polymer if necessary, (5) a norbornene-type resin A ring-opening copolymer of a monomer and ethylene or an α-olefin, and a resin obtained by hydrogenating the (co) polymer if necessary, (6) a norbornene-type monomer and a non-conjugated diene, or another monomer Examples thereof include a ring-opening copolymer and a resin obtained by hydrogenating the (co) polymer if necessary. These resins can be obtained by all known polymerization methods.

  Such a ring-opening polymer of a cyclic olefin resin is obtained by ring-opening (co) polymerizing at least one or more norbornene-type monomers by a known ring-opening polymerization method using titanium or a tungsten compound as a catalyst. A co) polymer, and then, if necessary, a hydrogenated carbon-carbon double bond in the ring-opened (co) polymer by a conventional hydrogenation method to produce a thermoplastic saturated norbornene resin. Obtained by.

  Examples of the polymerization solvent used for the addition polymerization and ring-opening polymerization include hydrocarbons and aromatic solvents. Examples of the hydrocarbon solvent include pentane, hexane, heptane, and cyclohexane, but are not limited thereto. Examples of the aromatic solvent include, but are not limited to, benzene, toluene, xylene and mesitylene. Diethyl ether, tetrahydrofuran, ethyl acetate, ester, lactone, ketone, amide can also be used. These solvents can be used alone or as a polymerization solvent.

  In the above cyclic olefin-based resin, in particular, the addition-type norbornene-based resin is excellent in heat resistance, and in particular, in the chemical structure of the addition-type norbornene-based resin having a structure represented by the following general formula (1). The main chain skeleton has a heat resistance with a glass transition temperature of about 300 ° C., which is preferable.

X in the formula (1) represents —O—, —CH ₂ — or —CH ₂ CH ₂ —, and R ₁ , R ₂ , R ₃ and R ₄ are each hydrogen, an alkyl group or cycloalkyl. Group, vinyl group, alkenyl group, alkynyl group, alkylidenyl group, aryl group, aralkyl group, silyl group, ester group, ether group, (meth) acryl group, and a group selected from epoxy groups, and these groups are alkyl groups , May be bonded via an ether group or an ester group, and may be the same or different. m is an integer of 10 to 10000, and n is an integer of 0 to 5.

  Examples of the alkyl group include (C1-C20) alkyl groups that may have a side chain such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, and an isobutyl group, and the cyclo group. Examples of the alkyl group include (C3-C15) cycloalkyl groups such as cyclohexyl group, cyclopentyl group, and methylcyclohexyl group. Examples of the alkenyl group include (C3-C10) alkenyl group and examples of the alkynyl group include , An ethynyl group, a propenyl group, a hexenyl group, an octenyl group and a heptenyl group (C2-C20) alkynyl group, the alkylidenyl group, for example, (C1-C6) alkylidenyl group, the aryl group, for example, phenyl Group, tolyl group, naphthyl group, benzyl group and Examples of the (C6-C40) aryl group such as phenylethynyl group and the aralkyl group include (C7-C15) aralkyl group and the silyl group include, for example, a trimethoxysilyl group, a triethoxysilyl group, and a triethoxysilyl group. Group and silyl group such as triethoxysilylethyl group, as the ester group, for example, ester group such as methyl ester group, ethyl ester group, n-butyl ester group, t-butyl ester group and n-propyl ester group, Examples of the (meth) acryl group include a (meth) acryl group such as a methacryloxymethyl group, and examples of the epoxy group include an epoxy group such as a glycidyl ether group.

  In the present invention, it is preferably an addition polymer of a norbornene-type monomer, and in particular, an addition copolymer using two or more monomers represented by the general formula (2) which is a norbornene-type monomer having the above-described substituent. By combining, properties such as adhesion and electrical properties can be imparted in a well-balanced manner, which is more preferable.

[X in Formula (1) represents —O—, —CH ₂ — or —CH ₂ CH ₂ —, and R ₁ , R ₂ , R ₃ and R ₄ are each hydrogen, an alkyl group, cyclo A group selected from an alkyl group, a vinyl group, an alkenyl group, an alkynyl group, an alkylidenyl group, an aryl group, an aralkyl group, a silyl group, an ester group, an ether group, a (meth) acryl group, and an epoxy group. These groups are alkyl groups. They may be bonded via a group, an ether group or an ester group, and may be the same or different. m is an integer of 10 to 10000, and n is an integer of 0 to 5. ]

Examples of the norbornene monomer having the substituent include, for example, those having an alkyl group, such as 5-methyl-2-norbornene, 5-ethyl-2-norbornene, 5-propyl-2-norbornene, and 5-butyl-2-norbornene. 5-pentyl-2-norbornene, 5-hexyl-2-norbornene, 5-heptyl-2-norbornene, 5-octyl-2-norbornene, 5-nonyl-2-norbornene, 5-decyl-2-norbornene, 5 -Methylene-2-norbornene, etc .; as having a cycloalkyl group, 5-cyclohexyl-2-norbornene, 5-cyclohexenyl-2-norbornene, etc .; as having an alkenyl group, 5-vinyl-2-norbornene And 5-allyl-2-norbornene; Examples of the group having 5- group include 5- (2-propenyl) -2-norbornene, 5- (3-butenyl) -2-norbornene, 5- (1-methyl-2-propenyl) -2-norbornene, 5- (4-pentenyl) -2-norbornene, 5- (1-methyl-3-butenyl) -2-norbornene, 5- (5-hexenyl) -2-norbornene, 5- (1-methyl-4-pentenyl)- 2-norbornene, 5- (2,3-dimethyl-3-butenyl) -2-norbornene, 5- (2-ethyl-3-butenyl) -2-norbornene, 5- (3,4-dimethyl-4-pentenyl) ) -2-norbornene, 5- (7-octenyl) -2-norbornene, 5- (2-methyl-6-heptenyl) -2-norbornene, 5- (1,2-dimethyl-5-hexenyl) -2- Examples of those having an alkylidenyl group include 5- (5-ethyl-5-hexenyl) -2-norbornene, 5- (1,2,3-trimethyl-4-pentenyl) -2-norbornene; Ethylidene-2-norbornene, 5-isopropylidene-2-norbornene, etc .; those having an aryl group include 5-phenyl-2-norbornene, 5-benzyl-2-norbornene, 5-phenethyl-2-norbornene, 5 -Pentafluorophenyl-2-norbornene, 5-pentafluorophenylmethane-2-norbornene, 5- (2-pentafluorophenylethyl) -2-norbornene, 5- (3-pentafluorophenylpropyl) -2-norbornene, etc. ;, As those having a silyl group, 1,1,3,3,5, 5-hexamethyl-1,5-dimethylbis ((2- (5-norbornen-2-yl) ethyl) trisiloxane, 5-trimethoxysilyl-2-norbornene, 5-triethoxysilyl-2-norbornene, 5- (2-trimethoxysilylethyl) -2-norbornene, 5- (2-triethoxysilylethyl) -2-norbornene, 5- (3-trimethoxypropyl) -2-norbornene, 5- (4-trimethoxybutyl) ) -2-norbornene, 5-trimethylsilylmethyl ether-2-norbornene, dimethylbis ((5-norbornen-2-yl) methoxy)) silane, etc .; those having an epoxy group include 5-allylglycidyl-ether- 2-norbornene, etc .;
Further, those having a hydroxyl group, carboxyl group, ester group, acryloyl group or methacryloyl group include 5-norbornene-2-methanol, acetic acid 5-norbornene-2-methyl ester, and propionic acid 5-norbornene-2-methyl ester. , Butyric acid 5-norbornene-2-methyl ester, valeric acid 5-norbornene-2-methyl ester, caproic acid 5-norbornene-2-methyl ester, caprylic acid 5-norbornene-2-methyl ester, capric acid 5-norbornene- 2-methyl ester, lauric acid 5-norbornene-2-methyl ester, stearic acid 5-norbornene-2-methyl ester, oleic acid 5-norbornene-2-methyl ester, linolenic acid 5-norbornene-2-methyl ester, 5 -Nor Lunene-2-carboxylic acid, 5-norbornene-2-carboxylic acid methyl ester, 5-norbornene-2-carboxylic acid ethyl ester, 5-norbornene-2-carboxylic acid t-butyl ester, 5-norbornene-2-carboxylic acid i-butyl ester, 5-norbornene-2-carboxylic acid trimethylsilyl ester, 5-norbornene-2-carboxylic acid triethylsilyl ester, 5-norbornene-2-carboxylic acid isobornyl ester, 5-norbornene-2-carboxylic acid 2- Hydroxyethyl ester, 5-norbornene-2-methyl-2-carboxylic acid methyl ester, cinnamic acid 5-norbornene-2-methyl ester, 5-norbornene-2-methylethyl carbonate, 5-norbornene-2-methyl n -Butyl carbonate, 5- Rubornene-2-methyl t-butyl carbonate, 5-methoxy-2-norbornene, (meth) acrylic acid 5-norbornene-2-methyl ester, (meth) acrylic acid 5-norbornene-2-ethyl ester, (meth) Acrylic acid 5-norbornene-2-n-butyl ester, (meth) acrylic acid 5-norbornene-2-n-propyl ester, (meth) acrylic acid 5-norbornene-2-i-butyl ester, (meth) acrylic acid 5-norbornene-2-i-propyl ester, (meth) acrylic acid 5-norbornene-2-hexyl ester, (meth) acrylic acid 5-norbornene-2-octyl ester, (meth) acrylic acid 5-norbornene-2- Decyl ester and the like.

As an example of a polymer obtained from these monomers, in the addition-type norbornene resin having the structure represented by the general formula (1), the substituents R ₁ , R ₂ , R ₃ , and R ₄ are: According to the purpose, the characteristics can be made favorable by adjusting the kind of the substituent and the ratio of the repeating unit having the substituent. For example, in the general formula (1), X is —CH ₂ —, R ₃ and R ₄ are hydrogen, n is 0, and R ₁ and R ₂ are introduced, for example, when the alkyl group is introduced, It is preferable because a polynorbornene resin film having excellent flexibility can be obtained. In addition, when a trimethoxysilyl group or a triethoxysilyl group is introduced, adhesion with a metal such as copper is improved, which is preferable. However, when the ratio of triethoxysilyl group and trimethoxysilyl group is large, the dielectric loss tangent of the polynorbornene resin may increase, so the repeating unit of norbornene having a triethoxysilyl group and / or trimethoxysilyl group is In 1 molecule of norbornene represented by the general formula (1), it is preferably in the range of 5 to 80 mol%. More preferably, it is 5-50 mol%.

  Among them, in order to obtain a resin film having particularly good flexibility, adhesion and dielectric properties, 90 mol% of norbornene having an n-butyl group and 10 mol% of norbornene having a triethoxysilyl group in the general formula (1) Polynorbornene comprising 90 mol% unsubstituted (substituent is a hydrogen atom) norbornene having 10 mol% having norethoxysilyl group, polynorbornene having 75 mol% unsubstituted norbornene and 25 mol% norbornene having n-hexyl group Is preferred.

  Further, in place of the triethoxysilyl group and trimethoxysilyl group in the side chain, norbornene having an epoxy group is used in an amount of 5 to 95 mol%, preferably 20 to 80 mol%, more preferably 30 to 70%. When it does, adhesiveness with a base material can be improved.

The weight average molecular weight of the cyclic olefin-based resin is not particularly limited, but is preferably 1,000 to 1,000,000, particularly preferably 5,000 to 500,000, more preferably 10,000 to 250,000, Furthermore, 12,000-70,000 is preferable. When the weight average molecular weight (Mw) is within the above range, the heat resistance, solder bondability, sheet properties of the flux sheet, smoothness of the surface of the molded article, etc. are excellent in balance.
The weight average molecular weight can be evaluated in terms of polystyrene measured by, for example, gel permeation chromatography (GPC) using cyclohexane or toluene as an organic solvent.

The molecular weight distribution of the cyclic olefin-based resin [the ratio of the weight average molecular weight: Mw to the number average molecular weight: Mn (Mw / Mn)] is not particularly limited, but is preferably 5 or less, particularly preferably 4 or less, particularly 1 ~ 3 is preferred. When the molecular weight distribution is within the above range, the electrical characteristics are particularly excellent.
As a method for measuring the molecular weight distribution, for example, it can be measured by GPC using cyclohexane or toluene as an organic solvent.
In the case of a cyclic olefin resin whose weight average molecular weight or molecular weight distribution cannot be measured by the above method, it is possible to use a resin having a melt viscosity and a degree of polymerization that can form a resin layer by an ordinary melt processing method. it can. Although the glass transition temperature of the said cyclic olefin resin can be suitably selected according to a use purpose, it is 50 degreeC or more normally, Preferably it is 70 degreeC or more, More preferably, it is 100 degreeC or more, More preferably, it is 125 degreeC or more.

  The content of the cyclic olefin resin used in the present invention is preferably 5 wt% or more and 50 wt% or less of the entire curable flux. In the content, uncured sheet properties, adhesive strength after curing, flexibility, and solderability are more preferable.

  As the resin (A) having a phenolic hydroxyl group used in the present invention, for example, novolak type phenol resins such as phenol novolak resin, alkylphenol novolak resin and polyhydric phenol novolak resin, resol type phenol resin resin, polyvinyl phenol resin and the like are preferable. Can be used. Among these, the polyhydric phenol novolac resin has two or more phenolic hydroxyl groups in one benzene ring, so that it has dramatically improved as a solder joint flux compared to a monofunctional phenol novolac resin. Has performance. In addition, dihydroxybenzoic acid such as 2,4-dihydroxybenzoic acid and 2,5-dihydroxybenzoic acid, hydroxynaphthoic acid such as 1-hydroxy-2-naphthoic acid and 2-hydroxy-3-naphthoic acid, phenolphthaline, Hydroxybenzoic acid, hydroxyphenylacetic acid, 4-hydroxy-3-methoxybenzoic acid, diphenolic acid, 4-hydroxy-3-nitrobenzoic acid and the like have a carboxyl group in the molecule, and therefore, oxides on solder and metal surfaces The action of removing such stains is improved, and it is suitable for achieving a stable solder joint, and among them, dihydroxybenzoic acid and phenolphthaline are more preferable.

  Specific examples of the resin (B) that acts as a curing agent for the resin having a phenolic hydroxyl group used in the present invention include bisphenol A epoxy resin, bisphenol F epoxy resin, phenol novolac epoxy resin, and cresol novolac epoxy. Resin, alkylphenol novolac type epoxy resin type, biphenol type epoxy resin type, epoxy resin such as naphthol type epoxy resin, resorcinol type epoxy resin, dicyclopentadiene type epoxy resin, isocyanate resin or cyanate resin having the same skeleton as the above resin. May be. Moreover, the epoxy compound and isocyanate compound modified | denatured based on skeletons, such as aliphatic, cycloaliphatic, and unsaturated aliphatic, are mentioned. For example, a silicone-modified epoxy resin can be used.

  In the thermosetting flux of the present invention, the resin having a phenolic hydroxyl group is preferably contained in an amount of 5 wt% to 80 wt%. If it is less than 5% by weight, the effect of cleaning the metal surface is lowered, and there is a possibility that soldering cannot be performed. On the other hand, if it is more than 80% by weight, a sufficient cured product cannot be obtained, and the bonding strength and reliability may be lowered. The compounding amount of the resin acting as a curing agent for the resin having a phenolic hydroxyl group is, for example, at least 0.5 times the epoxy group equivalent or isocyanate group equivalent of the hydroxyl group equivalent of the resin having a phenolic hydroxyl group. Although 5 times or less is preferable, it is not this limitation when favorable metal bondability and hardened | cured material property are obtained.

In the thermosetting flux of the present invention, a thermoplastic resin can be used in a range that does not impair the above characteristics when improving the sheet properties of the flux layer in the flux sheet. Examples of the thermoplastic resin include phenoxy resin, polyvinyl butyral resin, polyester resin, polyurethane resin, polyimide siloxane resin, polypropylene, styrene-butadiene-styrene copolymer, polyacetal resin, polyamide resin, acrylonitrile-butadiene copolymer. Polymer, acrylonitrile-butadiene-methacrylic acid copolymer, acrylonitrile-butadiene-styrene copolymer, polyvinyl acetate resin, nylon, styrene-isoprene copolymer, styrene-butylene-styrene block copolymer, styrene-ethylene-butylene -A styrene block copolymer, a polymethylmethacrylate resin, etc. can be mentioned.
Moreover, you may add various additives, such as an inorganic filler, a curing catalyst, a coloring agent, an antifoamer, a flame retardant, a coupling agent, and a solvent other than the said component to an adhesive agent.

  The thermosetting flux of the present invention is obtained by blending and mixing the respective components in a desired ratio. The obtained thermosetting flux can be mixed with a solvent and used as a thermosetting flux varnish. Examples of the solvent include acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, toluene, mesitylene, xylene, hexane, isobutanol, n-butanol, 1-methoxy, 2-propanol acetate, butyl cellosolve, ethyl cellosolve, and methyl cellosolve. , Cellosolve acetate, ethyl lactate, ethyl acetate, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, diethylene glycol, n-butyl benzoate, N-methylpyrrolidone, N, N-dimethylformamide, tetrahydrofuran, γ-butyl lactone And anisole.

  The flux sheet of the present invention is composed of a flux layer composed of a thermosetting flux and at least one protective film layer that can be peeled off. The method for producing the flux sheet of the present invention will be described below. First, the resin varnish used as the material of a flux sheet is adjusted. On the peelable protective film, a curable flux varnish is applied to form a thermosetting flux layer and dried to obtain a flux sheet. Examples of the protective film include polyester, polyolefin, polyphenylene sulfide, polyvinyl chloride, polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, polyvinyl alcohol, polycarbonate, polyimide, polyether ether ketone, and the like. Examples of the application method include printing, curtain coating, bar coating, comma coating, and die coating. Although the thickness of a thermosetting flux layer can be suitably selected in relation to workability, flux activity, adhesive force, thermal stress relaxation effect, etc., 0.5-500 micrometers is preferred and 1-250 micrometers is still more preferred. The drying temperature depends on the solvent used, but is preferably 60 ° C to 180 ° C, and more preferably 70 ° C to 150 ° C. Moreover, in order to prevent the curable flux sheet surface and the protective film separation surface from being fused after rewinding, a peelable cover film may be bonded to the dried flux sheet application surface.

Next, an example of the manufacturing method of the multilayer wiring board using the flux sheet of this invention is shown.
As a method for manufacturing a multilayer wiring board of the present invention, first, a two-layer structure comprising a metal foil 101 and an insulating layer 102 is prepared, and a via hole 103 is formed in the insulating layer 102 (FIG. 1A). The two-layer structure can be obtained by directly applying a resin varnish on the metal foil 101 by a method such as printing, curtain coating, or bar coating. Furthermore, a two-layer structure such as a commercially available copper foil with resin (for example, copper foil with polyimide) may be prepared. The two-layer structure can also be obtained by etching one copper foil of the glass epoxy double-sided copper-clad laminate.

  Any method may be used for forming the via hole 103 as long as it is suitable for this manufacturing method, and examples thereof include dry etching using laser and plasma, chemical etching, and the like. As the laser, a carbon dioxide laser, an ultraviolet laser, an excimer laser, or the like can be used. When the insulating layer 102 includes a reinforcing fiber such as glass epoxy, it is preferable to use a carbon dioxide gas laser that can penetrate the resin and the glass cloth to form the via hole 103. When the insulating layer 102 does not include a reinforcing fiber such as polyimide, it is preferable to use an ultraviolet laser that can form a finer via hole 103. In the case where the insulating layer 102 is made of a photosensitive resin, the via hole 103 can be formed by selectively exposing and developing the insulating layer 102.

  Next, the conductive post 104 is formed in the via hole 103 by electrolytic plating using the metal foil 101 as an electrolytic plating lead (feeding electrode), and subsequently, the solder layer 105 is formed on the front end surface of the conductive post 104. (FIG. 1 (b)). If the conductor post 104 is formed by electrolytic plating, the shape of the tip of the conductor post 104 can be freely controlled, and the conductor post should be the same as the surface layer surface of the insulating layer 102 or protrude from the surface layer surface. Is desirable. This is because by making the conductor post project from the surface layer surface, the solder formed at the tip of the conductor post is melted and a solder joint in which a reinforcing structure is formed is obtained.

  The material of the conductor post 104 may be any material suitable for this manufacturing method, and examples thereof include copper, nickel, gold, tin, silver, and palladium. In particular, by using copper, a stable conductor post 104 can be obtained with low resistance.

  As a method for forming the solder layer 105, a method such as a method of forming by electroless plating, a method of forming the metal foil 101 as an electrolytic plating lead (power supply electrode) by electrolytic plating, a method of printing a paste containing solder, and the like. Is mentioned. In the printing method, it is necessary to align the printing mask with respect to the conductor post 104 with high accuracy. However, in the method using electroless plating or electrolytic plating, the solder layer 105 is formed in addition to the tip surface of the conductor post 104. Therefore, the conductor posts 104 can be easily miniaturized and densified. In particular, the electrolytic plating method is very suitable because the metal that can be plated is more diverse and the chemical solution can be easily managed than the electroless plating method.

  As a material of the solder layer 105, it is preferable to use Sn or In, or solder composed of at least two of Sn, Ag, Cu, Zn, Bi, Pd, Sb, Pb, In, and Au. More preferably, it is an environmentally friendly Pb-free solder.

  Next, the metal foil 101 is selectively etched to form a wiring pattern 106 to obtain a connection layer 110 (FIG. 1C).

  Next, a flux sheet 108 is formed on the surface of the connection layer 120 having the interlayer connection lands 107 arranged corresponding to the conductor posts 104 of the connection layer 110 (FIG. 1D). A method for forming the flux sheet 108 may be a method suitable for the resin to be used, and examples thereof include a method of laminating by a method such as vacuum lamination and vacuum press. Although FIG. 1 shows a method for forming an adhesive layer on the surface of the connection layer 120, an adhesive layer may be formed on the surface of the connection layer 110 on which the solder bumps are formed.

  Next, the connecting layer 110 and the connected layer 120 are aligned (FIG. 1E). The alignment uses a method such as a method of reading and aligning a positioning mark formed in advance on the connection layer 110 and the layer to be connected 120 with an image recognition apparatus, a method of aligning with a positioning pin or the like. Can do.

  Next, the adhesive layer 108 is brought into close contact with the connection layer 110 and the connected layer 120 (FIG. 1E). Examples of the close contact method include a method of softening the adhesive layer 108 by heating and pressurizing using a vacuum press or a pressure type vacuum laminator. In the above process, it is preferable that the solder layer 105 and the interlayer connection land 107 are kept in non-contact.

  Next, the connection layer 110 and the connection layer 120 are heated to a temperature equal to or higher than the melting point of the solder constituting the solder layer 105 to melt the solder and pressurize it to join the solder (FIG. 1 (f)). Finally, the multilayer wiring board 130 of the present invention is obtained through a desired process such as curing of the adhesive layer 108 and, if necessary, formation of a solder resist and singulation.

  Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited thereto.

(1) Preparation of adhesive varnish 1 105 g of m, p-cresol novolac resin (Nippon Kayaku Co., Ltd. PAS-1, OH group equivalent 120) and diallyl bisphenol A type epoxy resin (Nippon Kayaku Co., Ltd.) 500 g of RE-810NM, epoxy equivalent 220), 150 g of phenolphthalene and 700 g of polynorbornene solution (manufactured by Promelas, abaterol (30 wt% mesitylene solution of 90 mol% butyl norbornene and 10 mol% triethoxysilane norbornene)) Were mixed and stirred to prepare a curable flux varnish. Next, after applying the curable flux varnish obtained above to a polyester (Diafoil Hoechst Co., Ltd., T-100G, thickness 25 μm) film, it is dried at 100 ° C. for 20 minutes to form a 50 μm thick curable flux layer. Formed to obtain a curable flux sheet.

<Manufacture of wiring boards for manufacturing multilayer wiring boards>
A dry film resist (AQ-2058 manufactured by Asahi Kasei Co., Ltd., AQ-2058) is roll-laminated on a rolled copper plate (metal plate 201, manufactured by Furukawa Electric Co., Ltd., EFTEC-64T) having a thickness of 150 μm. The negative resist film was exposed and developed to form a plating resist necessary for forming the conductor circuit 211. Next, using a rolled copper plate as a lead for electrolytic plating, a gold layer and a nickel layer were formed by electrolytic plating, and further, electrolytic copper plating was performed to form a copper circuit to obtain a conductor circuit. The conductor circuit had a line width / interline / thickness = 20 μm / 20 μm / 10 μm. Next, a resin-coated copper foil (manufactured by Sumitomo Bakelite) was formed by vacuum lamination while embedding the wiring pattern irregularities, and the copper foil was entirely etched to form a 25 μm thick insulating layer.

  Next, vias having a top diameter of 45 μm and a bottom diameter of 25 μm were formed in the insulating layer using a UV-YAG laser. After cleaning the inside of the via and the periphery of the via with a permanganate resin etchant, electrolytic copper plating is performed using the rolled copper plate on the back surface as a lead for electrolytic plating (power supply electrode), and the via is filled with copper. Then, a copper post was formed. Here, the electrolytic copper plating time was adjusted so that the diameter of the copper post was 45 μm. Next, a nickel layer 205 is formed on the surface of the copper post by electrolytic plating to a thickness of 1 μm, and subsequently a Sn—Ag (2.5%) eutectic solder coating is formed by electrolytic plating to a thickness of 5 μm. A conductor post was obtained. In addition, the height which protruded from the insulating layer surface of the front-end | tip surface of Sn-Ag (2.5%) eutectic solder film was 11 micrometers. Finally, the rolled copper plate was removed by etching. Thus, a wiring board for producing a multilayer wiring board was obtained in which the conductor post was composed of a copper post, a nickel layer, and a solder coating, and the conductor circuit was composed of a copper circuit, a nickel layer, and a gold coating.

<Manufacture of multilayer wiring boards>
The above-mentioned curable flux sheet is applied to the surface of the insulating layer, that is, the surface on which the Sn—Pb eutectic solder layer is formed by bar coating on the wiring board for producing a multilayer wiring board obtained by the above-described method. Lamination was performed using a vacuum laminator, and the PET film was peeled off to form a curable flux layer.

  On the other hand, using a glass epoxy double-sided copper-clad laminate equivalent to FR-5 (ELC-4781 manufactured by Sumitomo Bakelite Co., Ltd.) having a 12 μm thick copper foil formed on both sides, the copper foil was selectively etched, A circuit pattern was formed to obtain a core substrate (core substrate 230).

  Next, a positioning mark formed in advance on the wiring board for manufacturing a multilayer wiring board obtained by the above-described process and the core board is read by an image recognition apparatus, and both are aligned, and 250 ° C., 0 Thermocompression bonding was performed at a condition of 5 MPa for 1 minute. Thereby, a multilayer wiring board was obtained. Further, in order to cure the curable flux layer, heat treatment was performed at 250 ° C./60 minutes in a nitrogen atmosphere. As a result of investigating the presence or absence of peeling at the interface between the curable flux layer and the core substrate or the wiring substrate for manufacturing the multilayer wiring board, the obtained multilayer wiring board was delaminated using a SAT (ultrasonic imaging device). The occurrence of was not observed.

  After confirming the continuity of the obtained multilayer wiring board, a temperature cycle test was conducted in which one cycle was −55 ° C. for 10 minutes and 125 ° C. for 10 minutes. The number of samples was 10. The disconnection defective joint after 1000 cycles of the temperature cycle test was zero.

  The obtained multilayer wiring board was subjected to heat treatment and moisture absorption treatment according to JEDEC standard level 2, and moisture absorption heat-resistant reliability evaluation was performed. Specifically, after pre-drying at 125 ° C./24 hours, moisture absorption treatment is performed at 85 ° C. and 60% RH for 196 hours, and a reflow profile corresponding to a lead-free solder having a peak temperature of 260 ° C. Was passed three times. The appearance of the multilayer wiring board after reflow was observed to confirm the presence or absence of swelling. In addition, the occurrence of voids in the multilayer wiring board and the peeled state were investigated using an SAT (ultrasonic imaging device). As a result, no swollen part was observed from the appearance observation with a microscope. Also, from the results of SAT, defects such as peeling, swelling and voids were not recognized.

  Further, in order to measure the dielectric properties of the insulating layer, the flux sheet obtained above was applied to the glossy surface of a 70 μm thick copper foil (trade name: 3EC-VLP foil, manufactured by Mitsui Kinzoku Co., Ltd.) using a vacuum laminator. Then, they were cured by heat treatment at 180 ° C. for 1 hour using a dryer in a nitrogen atmosphere. Next, the 70 μm thick copper foil was removed by etching to obtain a cured film of a flux sheet. Dielectric characteristics were measured by a perturbation method using a cylindrical cavity resonator, and a microwave network analyzer HP8510B (manufactured by Agilent Technologies) was used. As a result, the dielectric constant was 3.4, and the dielectric loss tangent was 0.005.

  From the above, the multilayer wiring board using the curable flux of the present invention has high joint reliability and high moisture absorption heat resistance reliability, and the effects of the present invention are obvious.

  According to the present invention, it is possible to surely perform solder bonding at the time of mounting a semiconductor chip and solder bonding such as interlayer connection of a multilayer wiring board, and it is not necessary to clean and remove the residual flux after solder bonding, which is high as an adhesive. Hygroscopic heat-resistant reliability can be obtained.

An example of the manufacturing method of the multilayer wiring board using the flux sheet of this invention is shown.

Explanation of symbols

101 Metal foil 102 Insulating layer 103 Via hole 104 Conductor post 105 Solder layer 106 Wiring pattern 107 Land 108 for interlayer connection Flux sheet (adhesive layer)
110 connection layer 120 connected layer 130 multilayer wiring board 130

Claims (9)

A thermosetting flux that acts as a flux at the time of soldering, comprising a resin (A) having a phenolic hydroxyl group, a resin (B) that is a curing agent of the resin, and a cyclic olefin resin (C) Thermosetting flux. The thermosetting flux according to claim 1, wherein the cyclic olefin-based resin includes a norbornene-based resin. The thermosetting flux according to claim 2, wherein the norbornene-based resin is an addition polymer of a norbornene-type monomer. The thermosetting flux according to claim 2 or 3, wherein the norbornene-based resin has a repeating unit represented by the following general formula (1).
[X in Formula (1) represents —O—, —CH ₂ — or —CH ₂ CH ₂ —, and R ₁ , R ₂ , R ₃ and R ₄ are each hydrogen, an alkyl group, cyclo A group selected from an alkyl group, a vinyl group, an alkenyl group, an alkynyl group, an alkylidenyl group, an aryl group, an aralkyl group, a silyl group, an ester group, an ether group, a (meth) acryl group, and an epoxy group. These groups are alkyl groups. They may be bonded via a group, an ether group or an ester group, and may be the same or different. m is an integer of 10 to 10000, and n is an integer of 0 to 5. ] The thermosetting flux according to any one of claims 2 to 4, wherein the norbornene-based resin is an addition copolymer of a monomer represented by the following general formula (2).
[X in Formula (1) represents —O—, —CH ₂ — or —CH ₂ CH ₂ —, and R ₁ , R ₂ , R ₃ and R ₄ are each hydrogen, an alkyl group, cyclo A group selected from an alkyl group, a vinyl group, an alkenyl group, an alkynyl group, an alkylidenyl group, an aryl group, an aralkyl group, a silyl group, an ester group, an ether group, a (meth) acryl group, and an epoxy group. These groups are alkyl groups. They may be bonded via a group, an ether group or an ester group, and may be the same or different. m is an integer of 10 to 10000, and n is an integer of 0 to 5. ] The thermosetting flux according to any one of claims 1 to 5, wherein the resin (A) having a phenolic hydroxyl group is at least one selected from phenolphthalin and dihydroxybenzoic acid. A flux sheet comprising a flux layer comprising the thermosetting flux according to any one of claims 1 to 6 and at least one protective film layer that can be peeled off. A connection layer having a wiring pattern, a conductor post formed on the wiring pattern, a solder layer formed on a front end surface of the conductor post, and a connected layer having a land for interlayer connection with the conductor post; A multilayer wiring board having an interlayer connection part which is solder-bonded by heating and pressurizing and thermocompression bonding via a flux layer made of the thermosetting flux according to any one of claims 1 to 6. The multilayer wiring board according to claim 8, wherein the flux layer is obtained by laminating the flux sheet according to claim 7.