JP2000294890A - Paste for filling through hole, printed wiring board using that and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a recess from being formed at the open face of a through hole and sufficiently lengthen the time for which paste is processible by specifying cure starting temperature obtained from a heating curve containing a plurality of independent heating peak when temperature is raised at a specific rate. SOLUTION: Using a differential scanning calorimeter, a heating curve which contains two independent heating peaks when temperature is raised at a rate of 10 deg.C/min is obtained. It is preferable that the cure starting temperature obtained from the heating curve should be 90 deg.C-135 deg.C and it is especially preferable that the cure starting temperature should be 110 deg.C-130 deg.C. If the cure starting temperature is less than 90 deg.C, paste starts to gelate or be cured immediately after the paste is prepared as the result of mixture of various types of resin and the like and the time for which the paste is processible is shortened. This is undesirable. If the temperature exceeds 135 deg.C, the amount of paste flowing out of a through hole S is increased due to bleed-out and a recess D is prone to be formed on the open face of the through hole S.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a paste for filling through holes, a printed wiring board using the same, and a method of manufacturing the same. More specifically, after filling the through-hole with the paste for filling the through-hole and heating and curing, it is possible to prevent the formation of a concave portion on the opening surface of the through-hole, and the paste for filling the through-hole is gelled. Provided is a paste for filling a through-hole, which has a sufficiently long time that can be used without being cured or cured (hereinafter, simply referred to as a pot life). Further, the present invention relates to a printed wiring board excellent in adhesion and durability because a concave portion is not formed in an opening surface of a through hole, and a method for manufacturing the same. The present invention relates to a lipophilic treatment such as a rust-proof treatment for improving adhesion to a resin on an outer peripheral surface of a substrate on which a through hole is formed and a peripheral conductor layer formed on a periphery of an opening end of the through hole. This is particularly useful when a chemical conversion treatment has been performed. A printed wiring board using this paste for filling through holes can be used for an MPU IC package or the like.

[0002]

2. Description of the Related Art With the miniaturization of electric and electronic equipment, the size of circuits to be mounted has been further reduced and the density thereof has been promoted, and the multilayer structure of printed wiring boards has been increased. As a method of multilayering this printed wiring board, a method of filling a through hole provided in a substrate with a resin, curing the resin, and then alternately stacking an insulating layer and a conductor layer to be a circuit on the substrate is used. is there. When such a method is used, the surface of the conductor layer formed of copper plating and copper foil formed on the substrate is subjected to a surface roughening treatment, and then the interlayer insulating layer and the solder resist layer laminated on the conductor layer In some cases, lipophilic treatment is performed to improve the adhesion with the like or to prevent rusting. As a result, the adhesion and wettability between the conductor surface and the resin contained in the interlayer insulating material, the solder resist, and the like are improved, and multilayering and high-density circuits can be stably performed.

However, when a conventionally used through-hole filling paste is filled into a through-hole provided in a substrate subjected to this lipophilic treatment and cured,
On the opening surface of the through hole, a recess of 20 to 300 μm may be formed toward the inside of the through hole.
When lamination is performed on the substrate with this recess formed,
There is a problem that cracks, peeling, and the like are likely to occur in the laminated portion on the concave portion. Heretofore, it has been considered that the cause of the formation of the concave portion is a curing shrinkage of the resin component or a volume decrease due to volatilization of the volatile component. For this reason, attempts have been made to use a resin that hardly shrinks on curing or use a paste or the like that does not use a solvent, but it has not been possible to sufficiently prevent the formation of concave portions.

Also, Japanese Patent Application Laid-Open Nos. 8-83971, 10-75027, and 10-200265
JP, JP-A-10-209615, JP-A-10-209615
JP-A-224034 discloses a filling ink and a resin filler used for a printed wiring board, and a printed wiring board using the same. However, none of these technologies is intended to be used for through holes provided in a lipophilic substrate.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. Particularly, even when a conductor layer having high wettability to resin or the like is formed on the periphery of the through-hole, the through-hole is not required. It is an object of the present invention to provide a through-hole filling paste that can prevent a concave portion from being formed on an opening surface of a through-hole after filling and curing a filling paste, and that has a sufficiently long pot life. I do. Another object of the present invention is to provide a printed wiring board using the paste for filling through holes and a method for manufacturing the same.

[0006]

SUMMARY OF THE INVENTION According to the present invention, a paste softened in a process of filling a through hole with a through hole filling paste (hereinafter, also simply referred to as a paste) and then heating and hardening the same is particularly useful for forming a peripheral conductor layer. When the surface has high wettability with respect to the resin, it rapidly flows down the peripheral conductor layer (hereinafter, this phenomenon is referred to as "bleed-out").
For this reason, it has been found that a concave portion (D in FIG. 1) is formed, and the present invention has been made based on this finding. That is,
It is considered that this bleed-out can be prevented by shortening the time from the start of heating to harden the paste to the gelling or hardening until the bleed-out does not occur. However, when a hardener having high activity is used simply to shorten the time required for the paste to gel or harden, the pot life is also shortened at the same time. If the pot life is short, there is a great disadvantage in workability and efficiency in mass production. The present invention solves these problems at the same time.

The paste for filling a through hole according to the first invention is a paste for filling a through hole used for a printed wiring board. When the temperature is increased at a rate of 10 ° C./min by a differential scanning calorimeter, the paste becomes an independent paste. An exothermic curve having two exothermic peaks is obtained, and a curing start temperature determined from the exothermic curve is 90 to 135 ° C.

[0008] The "printed wiring board" has a "substrate" in the center layer. This substrate is provided with "through holes" penetrating in the thickness direction. A "peripheral conductor layer" (31 in FIG. 1) is provided on the outer surface of the substrate where the through hole is formed, which is the periphery of the opening end of the through hole. Usually, a wall surface conductor layer (32 in FIG. 1) is provided on the inner wall surface of the through hole. The wall conductor layer has a function of conducting between the conductor layers provided on the front and back surfaces of the substrate including the peripheral conductor layer or in the printed wiring board. The aspect ratio (thickness of the substrate / diameter of the through hole) of the through hole is not particularly limited, but is usually 2 to 4. The peripheral conductor layer and the wall conductor layer may be formed of the same material and continuously, and the peripheral conductor layer and the wall conductor layer may be integrated. In the present invention, the materials of the substrate, the conductor layer, and the like are not particularly limited. Further, the material and the like of the printed wiring board are not particularly limited.

The above-mentioned "heat generation curve" is a "differential scanning calorimeter".
And has two independent exothermic peaks obtained by differential scanning calorimetry (hereinafter, also simply referred to as DSC). In this measurement, although the measurement object is different, JIS K71
21. This makes it possible to evaluate various properties such as the correlation between the heating temperature and the curing temperature. JI
The test piece referred to in SK7121 is a paste in the present invention. Therefore, "condition adjustment of test piece" and "test piece" are "condition adjustment of paste" and "paste" respectively.
Can be said. Conditioning of the paste is, in principle, carried out at a temperature of 23 ± 2 ° C. and a relative humidity of 50 ± 5%.
It is carried out by allowing to stand for 〜8 hours without any heat treatment. In addition, since the paste is measured in the form of a paste, there is no regulation on dimensions.

The above "curing start temperature" is defined in JIS K7
It is to be calculated according to the method for obtaining the extrapolation melting start temperature specified in 121. That is, a straight line extending from the low-temperature side baseline to the high-temperature side and the low-temperature side heat generation peak,
The temperature at the intersection of the tangents drawn at the point where the gradient becomes maximum on the low temperature curve is defined as the curing start temperature. However, JIS K712
1 is an endothermic curve, whereas the present invention is an exothermic curve. The curing start temperature determined from this heat generation curve is 90
To 135 ° C, more preferably 100 to 130 ° C, particularly preferably 110 to 130 ° C. When the curing start temperature is less than 90 ° C,
Immediately after preparing the paste by mixing various resins and the like, since this paste gels or hardens,
The pot life is shortened, which is not preferable. If this temperature is 1
If the temperature exceeds 35 ° C., the amount of paste flowing out of the through-hole due to bleed-out increases, and a recess is easily formed on the opening surface of the through-hole, which is not preferable.

The formation of the recess is also affected by the peak heat generation temperature on the low temperature side. The exothermic peak temperature on the low temperature side is J
It shall conform to the method of determining the melting peak temperature specified in IS K7121. That is, of the two heat generation peaks of the heat generation curve, the temperature at the top of the heat generation peak on the low temperature side is defined as the heat generation peak temperature on the low temperature side. However, JISK7
The curve 121 shows an endothermic curve, whereas the present invention shows an exothermic curve. The exothermic peak temperature on the low temperature side is 100 to 1
The temperature is preferably 40 ° C, more preferably 100 to 135 ° C, and particularly preferably 105 to 135 ° C. When the exothermic peak temperature on the low temperature side is lower than 100 ° C., the pot life of the paste becomes short, which is not preferable. On the other hand, if the temperature exceeds 140 ° C., the amount of paste flowing out of the through-hole due to bleed-out increases, and a recess is easily formed on the opening surface of the through-hole, which is not preferable.

Further, the formation of the concave portion is also affected by the temperature difference between the curing start temperature and the exothermic peak temperature on the low temperature side.
Therefore, as in the second invention, the above-mentioned "temperature difference" between the curing start temperature and the exothermic peak temperature on the low temperature side obtained from the exothermic curve is preferably 20 ° C or less (usually 3 ° C or more). This temperature difference is more preferably from 3 to 15 ° C, and even more preferably from 3 to 10 ° C. If this temperature difference exceeds 20 ° C., the time from the start of heating for curing the paste to the curing becomes long. For this reason, bleed-out easily occurs, and formation of a concave portion cannot be sufficiently prevented.

When the heat generation curve has two or more heat generation peaks, these heat generation peaks are said to be “independent” as in the case of Reference Example 1 in FIG. The difference between the point a indicating the lowest heat generation amount between the peak and the heat generation peak located on the higher temperature side, and the straight line including this point a as an extension of the baseline, and the point b intersecting, , 0.5 mW or less. In Reference Example 1, the difference between the heat values at points a and b was 0.5 mW.
It indicates the following case, and in such a case, 2
The two exothermic peaks are independent. On the other hand, Reference Example 2 in FIG. 4 shows a case where the difference in the heat value between the points a and b exceeds 0.5 mW, and in such a case, the two heat generation peaks are not independent. This difference is preferably 0.3 mW or less, and more preferably 0.2 mW or less.
Thereby, the pot life can be extended.

In the heat generation curve of the present invention, the heat value may be indicated by a negative value as shown in FIG. 4. This is caused by the difference in heat capacity between the sample and the measurement sample, and does not indicate that heat is actually absorbed. The actual calorific value of the sample to be measured is defined as a calorific value of 0 mW at the point where the baseline starts to be stabilized after the start of the temperature rise.

The above "paste for filling through holes"
It is a paste that can be filled in the through-holes and filled with the cured product generated by curing. This paste contains a thermosetting resin and a curing agent. As the thermosetting resin, epoxy resin, unsaturated polyester resin, urea resin, melamine resin, phenol resin, amino resin, polyurethane resin, silicone resin, addition polymerization type polyimide resin, bismaleimide type polyimide resin, etc. should be used. Can be. Among these, epoxy resin, addition polymerization type polyimide resin and bismaleimide type polyimide resin are used because heat resistance, insulation, moisture resistance and mechanical strength are high, the coefficient of thermal expansion is small, and the shrinkage due to curing is small. Is preferred.

As the thermosetting resin, it is preferable to use an epoxy resin as in the third invention. Examples of the “epoxy resin” include bisphenol A epoxy resin, bisphenol A bromide epoxy resin, bisphenol F epoxy resin, bisphenol S epoxy resin, bisphenol AF epoxy resin, biphenyl epoxy resin, and naphthalene epoxy resin. And a fluorene type epoxy resin, a phenol novolak type epoxy resin, an orthocresol type epoxy resin, a trishydroxyphenylmethane type epoxy resin, a tetraphenolethane type epoxy resin and the like.
These are all excellent in heat resistance and the like.

Of these, bisphenol A type epoxy resin (product name: E-828), bisphenol F type epoxy resin (product name: E-807), phenol novolak type epoxy resin and the like (product name: E-152) are particularly preferred. It is preferable to use bisphenol A type epoxy resin (product name: YL980) and bisphenol F type epoxy resin (product name: YL983U), which are particularly low-chlorinated epoxy resins among these resins. . By using this low-chlorinated epoxy resin, even when the printed wiring board is used in a high-temperature and high-humidity environment, a short circuit of the circuit can be prevented. These epoxy resins may be used alone or in combination of two or more. Furthermore,
It may be modified with another compound or the like. Also,
The product names shown above are all trade names of Yuka Shell Epoxy.

Since these epoxy resins greatly differ in the properties of the cured product obtained depending on the type of curing agent, a cured product having high heat resistance, low water absorption and high insulation can be formed. It is preferable to use a curing agent which has high activity and can extend the pot life. As such a "curing agent", polyamine, acid anhydride, polyphenol, isocyanate, organic acid, amines, imidazole, Lewis acid and the like can be used. Among these, it is preferable to use an imidazole-based curing agent. Further, among the imidazole-based curing agents, it is preferable to use a compound represented by the general formula (1) (hereinafter, simply referred to as trimellitate-based curing agent) as in the third invention. This compound is obtained by reacting an imidazole compound with trimellitic acid. Thereby, a paste having temperature characteristics such as the above-described curing start temperature can be manufactured.

Examples of such trimellitate curing agents include 1-cyanoethyl-2-ethyl-4-methylimidazole trimellitate (2E4MZ-CNS) and 1-cyanoethyl-2-undecylimidazole trimellitate (C11Z-CNS). ), 1-cyanoethyl-2-phenylimidazole trimellitate (2PZ-CNS),
1-cyanoethyl-2-methylimidazole trimellitate and the like can be mentioned. In addition, these trimellitate-based curing agents may be used alone or in combination of two or more. Further, all the product names shown above are trade names of Shikoku Chemical Industry Co., Ltd.

The mixing ratio of the epoxy resin and the curing agent is 90 to 98 parts when the total amount of the epoxy resin and the curing agent is 100 parts by weight (hereinafter simply referred to as "parts"). And the curing agent is 2 to 10 parts (more preferably, 92 to 97 parts of the epoxy resin, and 3 to 10 parts of the curing agent).
8 parts). If the compounding ratio of the epoxy resin exceeds 98 parts, that is, if the compounding ratio of the curing agent is less than 2 parts, it is not preferable because the epoxy resin cannot be sufficiently cured. On the other hand, if the compounding ratio of the epoxy resin is less than 90 parts, that is, if the compounding ratio of the curing agent exceeds 10 parts, the heat resistance of the cured product is likely to be lowered, which is not preferable.

Various fillers can be added to further reduce shrinkage due to curing of the paste of the present invention, and at the same time, bring the coefficient of thermal expansion closer to the material constituting the substrate. As such a filler, an inorganic filler composed of silica, alumina, or the like, a metal filler composed of copper, nickel, iron, or the like, a mixture thereof, or the like can be used. The material and the like of these fillers are preferably selected in consideration of the thermal stability, moisture resistance, mechanical strength, and the like of the cured product after curing the paste.

The particle size of the filler is preferably selected in consideration of the viscosity of the paste and the mechanical strength of the cured product after the paste is cured.
m (more preferably 0.1 to 10 μm) can be used. If the particle size of the filler exceeds 20 μm, cracks may occur at the interface between the filler and the resin, which is not preferable. If the particle size is less than 0.1 μm, it is difficult to handle and is not preferable.

The filler is 25 to 300 parts (more preferably 60 to 150 parts) when the paste is 100 parts.
Parts, more preferably 90 to 130 parts). By mixing the epoxy resin, the curing agent and the filler at such a mixing ratio, the viscosity of the paste is 10 to 2000 Pa · s (more preferably 50 to 15 Pa · s).
00 Pa · s, and more preferably 100 to 1000 Pa · s).

The pastes of the first to third inventions can be suitably used for through-holes whose peripheral conductor layers have been subjected to lipophilic treatment as in the fourth invention. The surface of the peripheral conductor layer subjected to such lipophilic treatment has a high affinity for a resin or the like and is easy to bleed out, and the amount of the paste to be bleed out is easily increased. . However, by using the pastes of the first to third inventions, the recesses are formed 10
It can be kept to a depth of less than μm (preferably less than 5 μm, or even not formed). With such a concave portion, lamination can be performed without any problem. Usually, this lipophilic treatment is performed not only on the peripheral conductor layer but also on the wall surface conductor layer.

The above-mentioned "lipophilic treatment" usually means that at least the surface of the conductor layer is covered with a coupling agent or the like. Examples of such a coupling agent include a silicon-based coupling agent, a titanium-based coupling agent, a zirconium-based coupling agent, and an aluminum-based coupling agent. Specifically, as the silicon-based coupling agent (silane coupling agent), vinyltrichlorosilane, vinyltris (β-methoxyethoxy) silane, vinyltriethoxysilane,
Vinyltrimethoxysilane, γ- (methacryloyloxypropyl) trimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-
Glycidyloxypropyltrimethoxysilane, γ-glycidyloxypropylmethyldimethoxysilane, N-
β- (aminoethyl) -γ-aminopropyltrimethoxysilane, N-β- (aminoethyl) -γ-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxy Examples thereof include silane, γ-mercaptopropyltrimethoxysilane, imidazole silane compounds, benzimidazole silane compounds, and bistrialkoxysilyl compounds.

Further, as the titanium-based coupling agent,
Diisopropoxybis (acetylacetonato) titanium,
Isopropoxy (2-ethyl-1,3-hexadiolato) titanium, diisopropoxybis (triethanolaminato) titanium, di (2-ethylhexoxy) bis (2
-Ethyl-1,3-hexanediolato) titanium, di-n
-Butoxybis (triethanolaminato) titanium, tetraacetylacetonate titanium, hydroxybis (lactone) titanium, isopropyltriisostearolyl titanate, isopropyltri-n-dodecylbenzenesulfonyl titanate, isopropyltris (dioctylpyrophosphate) titanate, tetra Isopropyl bis (dioctyl phosphite) titanate, tetraoctyl bis (ditridecyl phosphite) titanate,
Tetra (2,2-diallyloxymethyl-1-butyl)
Bis (di-tridecyl) phosphite titanate, bis (dioctyl pyrophosphate) oxyacetate titanate, bis (dioctyl pyrophosphate) ethylene titanate and isopropyl tri (N-aminoethyl-aminoethyl) titanate can be mentioned.

In addition, acetylacetone tributoxy zirconium as a zirconium coupling agent, (alkyl acetoacetato) aluminum diisopropylate as an aluminum coupling agent, vanadium oxyacetylacetonate as a vanadium coupling agent and the like are also included. Can be mentioned. Each of these coupling agents may be used alone, or two or more of them may be used in combination. In addition, other compounds may be contained.

Due to such lipophilic treatment, the contact angle of water on the surface of the peripheral conductor layer may be 90 ° or more (further 93 ° or more, particularly 95 ° or more, usually 120 ° or less). The paste of the present invention can be particularly suitably used for a through-hole provided with a peripheral conductor layer having such a high contact angle. Even when the paste of the present invention is used for such a through-hole, the recess formed on the opening surface of the through-hole is less than 10 μm (preferably less than 5 μm, and more preferably less than 5 μm) toward the inside of the through-hole. Not) can be kept at a depth. With such a concave portion, lamination can be performed without any problem.

The peripheral conductor layer having a contact angle with water of 90 degrees or more prevents rust on the surface of the peripheral conductor layer.
And / or in order to improve the adhesiveness of the resin layer further laminated on this peripheral conductor layer, it is formed by performing the above-described lipophilic treatment. This contact angle depends on the temperature 2
It is assumed that the angle is measured by a contact angle measuring instrument at 0 to 25 ° C and humidity of 40 to 60%. The measuring method is as follows. First, adjustment is performed with a parallelizer so that the surface to be measured of the object to be measured is horizontal. Pure water is dripped or adhered to the parallel surfaces to be measured very quietly so that the diameter thereof becomes 1.5 to 2 mm (preferably 2 mm). A tangent is drawn to the interface between the water droplet and the atmosphere from the contact point between the water droplet thus formed and the surface to be measured and the air. Of the angles between the tangent line and the surface to be measured, the angle including the water drop is read by a contact angle measuring device as the contact angle.

Usually, when the contact angle is measured on the surface of metallic copper which is often used as a conductor layer, it is 70 to 85 degrees on the surface of the conductor layer which has not been subjected to the roughening treatment. The angle is 75 to 90 degrees on the surface of the conductor layer subjected to the roughening treatment by the oxidation treatment (usually called the blackening treatment). Furthermore, the temperature is 85 to 100 degrees on the conductor layer surface (metal copper on which fine irregularities are formed) subjected to a roughening treatment for eluting the metal copper surface.

A printed wiring board according to a fifth aspect of the present invention is a printed wiring board having a through hole provided in a substrate, and a peripheral conductor layer formed on the outer surface of the substrate and around the opening end of the through hole. In the wiring board, the inside of the through hole is formed of a cured body made of the paste for filling a through hole according to any one of claims 1 to 4.

Each of the "printed wiring board", "substrate", "through hole", "peripheral conductor layer", and "paste for filling through hole" is the same as in the first to fourth inventions. Usually, such a printed wiring board has a structure as shown in FIG. That is, a peripheral conductor layer 31 and a wall conductor layer 32 are provided on the periphery and the inner wall surface of the through hole provided in the substrate 1, and the through hole is constituted by the cured body 2 made of the paste of the first to fourth inventions. Is done.
Further, the surface of the peripheral conductor layer is further laminated by an interlayer insulating layer 4. A conductor layer 33 is further formed on the surface of the interlayer insulating layer. On the surface of the conductor layer 33, a solder resist layer 5 is further formed. Note that two or more interlayer insulating layers and conductor layers may be formed on the front and back surfaces of the substrate. However, the solder resist layer is formed only on the outermost layer.

Further, the printed wiring board of the present invention has a lipophilic treatment similar to that described above on the peripheral conductor layer, as in the sixth invention, and further has a structure as in the seventh invention. To
Even when the contact angle with water is 90 ° or more (more preferably 93 ° or more, particularly 95 ° or more) by the lipophilic treatment, the through holes are filled with the paste according to the first to fourth inventions and cured. Thus, the concave portion formed at the opening end of the through hole can be made smaller than 10 μm (preferably smaller than 5 μm, and furthermore, not formed), and good lamination can be performed on this substrate. Therefore, it is possible to obtain a highly reliable printed wiring board that does not crack, peel off, bend, or the like even in an environment of high temperature and high humidity. The printed wiring board is not limited to a multilayer printed wiring board, but may be a double-sided printed wiring board or the like.

According to the eighth aspect of the present invention, there is provided the printed wiring board manufacturing method, wherein the surface of the peripheral conductor layer formed on the outer surface of the substrate and at the periphery of the opening end of the through hole provided in the substrate is subjected to lipophilic treatment. , And then, the through hole is subjected to claim 1.
5. A step of filling the paste for filling a through-hole according to any one of the above items 4 to 4, and thereafter heating and curing the paste for filling a through-hole.

The above "printed wiring board", "through hole", "peripheral conductor layer" and "lipophilic treatment" are the same as in the first to fourth inventions. Further, as in the ninth invention, when the contact angle of water on the surface of the peripheral conductor layer after the lipophilic treatment is 90 degrees or more, this production method can be particularly preferably used. The “contact angle” is the same as in the first to fourth inventions.

The working life of the pastes of the first to fourth inventions is long, and the reason why the use of this paste can prevent the formation of a concave portion on the opening surface of a through hole is not clear. However, it can be inferred as follows. That is, the trimellitate-based curing agent is a salt of an imidazole-based compound and trimellitic acid, and when this curing agent is used for curing an epoxy-based resin, a carboxyl group in trimellitic acid and a polyaddition reaction of the epoxy-based resin are performed. Then, it is considered that the polymerization reaction of the epoxy resin using the imidazole compound as a catalyst proceeds thereafter. This is inferred from the appearance of two independent peaks in the exothermic curve,
It is considered that the exothermic peak on the low temperature side corresponds to the polyaddition reaction, and the exothermic peak on the high temperature side corresponds to the polymerization reaction.

That is, when the paste of the present invention is heated,
When the temperature exceeds the curing start temperature, the polyaddition reaction proceeds rapidly, the molecular weight of the resin increases, the bleed out can be prevented due to an increase in viscosity, and the polymerization reaction of the epoxy resin that occurs thereafter is sufficient. It is considered that a cured product having heat resistance is obtained. Further, the level of the activity of the curing agent is considered to be affected by the strength of the basicity of the imidazole-based compound. By reducing the basicity, the pot life of the paste can be extended. Since the trimellitate-based curing agent used in the present invention forms an organic acid salt, the basicity of the imidazole-based compound is reduced. Therefore, the pot life of this paste is considered to be long.

[0038]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described specifically with reference to examples. Example (1) Preparation of Paste The epoxy resin and the curing agent shown in Table 1 were mixed in a quantitative ratio shown in Table 1 with a three-roll mill and sufficiently dispersed, and the pastes for filling through holes of Experimental Examples 1 to 5 were used. Prepared.

[0039]

[Table 1]

However, in Table 1, epoxy resin EA; bisphenol A type epoxy resin, manufactured by Yuka Shell Co., Ltd., trade name "YL980" Curing agent KA; 1-cyanoethyl-2-ethyl-4-methyl Imidazole trimellitate, manufactured by Shikoku Chemicals,
Trade name "2E4MZ-CNS"KB; 1-cyanoethyl-2-undecylimidazole trimellitate, manufactured by Shikoku Chemicals Co., Ltd., trade name "C11Z-CNS"KC; 1-cyanoethyl-2-phenylimidazole Trimerite, manufactured by Shikoku Chemical Industry Co., Ltd., trade name "2
PZ-CNS "KD; 2,4-diamino-6- {2'-methylimidazolyl- (1 ')}-ethyl-s-triazine, manufactured by Shikoku Chemicals Corporation, trade name" 2MZA "KE 2-Ethyl-4-methylimidazole, manufactured by Shikoku Chemicals Co., Ltd., trade name "2E4MZ"KF; 2-Phenylimidazole, manufactured by Shikoku Chemicals Co., Ltd., trade name "2PZ" Filler FA: Silica filler , Made by Tatsumori Co., Ltd.
OC2 "

(2) Measurement of Differential Scanning Calorimetry For 5 ± 1 mg of each paste of Experimental Examples 1 to 5, a differential scanning calorimeter (manufactured by Seiko Instruments Inc., Model “D”)
SC22 "), the temperature was raised at a temperature of 30 to 180 ° C at a rate of 10 ° C / min to obtain a DSC curve. The curing start temperature and the exothermic peak temperature were determined from the DSC curve by the methods described above. These temperatures are also shown in Table 1. Also,
FIG. 4 shows the heat generation curves of Experimental Examples 3 and 4. The exothermic curve of Experimental Example 4 has one exothermic peak,
In Experimental Example 3, two exothermic peaks are recognized independently. In FIG. 4, c and d are the curing start temperature and the exothermic peak temperature on the low temperature side in Experimental Example 3. Further, e and f are the curing start temperature and the exothermic peak temperature on the low temperature side in Experimental Example 4. c, d, e and f are respectively 119 ° C. and 128
139 ° C, 154 ° C.

(3) Treatment of the Conductive Layer Surface of the Substrate One of the following two treatments was applied to the substrate, and the contact angle of the peripheral conductor layer was measured. [1] Contact angle measuring method Contact angle measuring device (trade name “CA” manufactured by Kyowa Interface Science Co., Ltd.)
-A "). The method was performed according to the attached instructions. That is, pure water (electric conductivity is 0 to 1 μs
/ Cm of pure water. ) Was adjusted by a droplet adjuster to form a droplet at the tip of the dripping needle. These droplets had a scale of 15 to 20 on a QI optical scale and had a diameter of about 2 mm. The sample stage on which the substrate was fixed was lifted toward this droplet, and the substrate was slowly brought into contact with the droplet to move the droplet onto the substrate. From the magnifying glass with a cross drawn on the lens,
While visually observing the droplet, a cross was searched for the apex of the droplet. That is, as shown in FIG. 6A, after the cross is aligned with the interface between the droplet and the atmosphere, the cross is moved vertically as shown in FIG. And the air interface. The point at which the intersection of the cross and the interface between the droplet and the atmosphere intersect is the apex of the droplet. The vertex and a contact, which is an interface between the substrate, the droplet, and the atmosphere, are connected by a straight line. That is, FIG.
(C). The contact angle was twice the angle θ between this straight line and the sample stage.

[2] Surface Treatment of Peripheral Conductor Layer and Measurement of Contact Angle of Its Surface Contact Angle of Peripheral Conductor Layer After Blackening Treatment The epoxy resin substrate was immersed in a 75 ° C. aqueous NaClO ₂ solution for 5 minutes. Then, the conductor surface was roughened. The contact angle of the blackened peripheral conductor layer (the surface of the peripheral conductor layer was copper oxide) was measured to be 87 degrees. Contact angle of peripheral conductor layer subjected to rust prevention treatment (lipophilic treatment) After roughening the conductor surface of the substrate with a commercially available micro-etching solution, it is further immersed in the provided rust prevention solution for one minute to prevent rust. Treatment (lipophilic treatment) was performed. The measured contact angle of the peripheral conductor layer subjected to this treatment was 101 degrees.

(4) Filling and curing of each paste The pastes of Experimental Examples 1 to 5 prepared in (1) were placed in through holes provided in an epoxy resin substrate which had been subjected to blackening treatment or rust prevention treatment. Each was filled and heated at a temperature of 120 ° C. for 20 minutes, and then further heated at 150 ° C. for 5 hours. The through hole of the substrate thus obtained was observed with a measuring microscope, and the presence or absence and depth of the concave portion were evaluated. The results are shown in Table 1. In Table 1, “none” indicates that no recess was formed, “、” indicates that a recess of less than 10 μm was formed, “△” indicates that a recess of 10 to 20 μm was formed, and “×” was 20 μm. Each of the above-described concave portions is shown. In Table 1, * indicates that the value is outside the scope of the first invention.

(5) Measurement of pot life The pastes of Experimental Examples 1 to 5 adjusted in (1) were allowed to stand at 23 ° C., and every 24 hours, a rotational viscometer (manufactured by RION, model “VISCOTESTER VT-04”) was used. )). The time required for the viscosity to be twice the viscosity measured immediately after preparing the paste was defined as the pot life. The results are shown in Table 1.

From the results shown in Table 1, when the curing starting temperature of the paste is 130 ° C. or lower, the concave portions are formed on both the substrate subjected to the blackening treatment and the substrate subjected to the rust prevention treatment which is the lipophilic treatment. Is not formed. Further, when a curing agent other than a trimellitate curing agent is used as in Experimental Example 4, bleed-out cannot be sufficiently prevented. On the other hand, it can be seen that the pot life can be sufficiently extended by using the trimellitate curing agent according to the present invention. Note that the heat generation peak is independent since the heat generation difference between the minimum heat generation amount between the two heat generation peaks and the extension of the baseline in Experimental Example 3 is 0.2 mW.

On the other hand, as shown in FIG. 7 and FIG. 8, the curing start temperatures of Experimental Examples 5 and 6 are 111 ° C. and 115 ° C., respectively, which are within the range of the first invention. Can be prevented. However, in Experimental Example 5, there is only one exothermic peak, and in Experimental Example 6, the difference in the calorific value between the minimum calorific value between the two exothermic peaks and the extension of the baseline was 4.5 mW, indicating that the first exothermic peak was obtained. It does not have two independent exothermic peaks referred to in the invention. For this reason, it can be seen that in Examples 5 and 6, the pot life is one-fifth or less of that when the trimellitate-based curing agent is used.

It should be noted that the present invention is not limited to the specific embodiments described above, but can be variously modified within the scope of the present invention according to the purpose and application. That is, other components may be mixed within a range that does not substantially affect the present invention. For example, a thixotropic agent, a coloring agent, a leveling agent, a viscosity adjusting agent, a stabilizer, and the like can be added in a range that does not substantially affect insulation properties and moisture resistance. In addition, the paste of the present invention is usually used by filling in through holes, but can also be used for filling other holes such as vias, holes and grooves.

[0049]

According to the first to fourth aspects of the present invention, even a through-hole having a peripheral conductor layer whose surface has been subjected to rust prevention treatment and lipophilic treatment for improving adhesion to a resin or the like is provided. Thus, it is possible to obtain a paste that can be cured without bleeding out and without forming a concave portion on the opening surface of the through hole. At the same time, a paste having a sufficiently long pot life can be obtained. Further, according to the fifth to seventh inventions, the paste is filled into the through-hole provided in the substrate subjected to the lipophilic treatment,
Even with a printed wiring board provided with a cured substrate, a printed wiring board having excellent adhesion can be obtained without causing cracks, peeling, and bending. Furthermore, according to the eighth and ninth inventions, even when the peripheral conductor layer having a contact angle with water of 90 degrees or more is formed by performing the lipophilic treatment, the bleed out can be effectively prevented. This can prevent the formation of the concave portion.

[Brief description of the drawings]

FIG. 1A is a cross-sectional view schematically illustrating a configuration of a peripheral edge of a through hole in a state where a paste for filling a through hole is cured without forming a concave portion on an opening surface of the through hole. (B) is a cross-sectional view schematically showing a configuration of a peripheral edge of a through hole in a state where a recess is formed due to bleed-out.

FIG. 2 is a cross-sectional view schematically illustrating an example of a configuration of a printed wiring board which is filled with a paste for filling a through hole according to the present invention and cured.

FIG. 3 is an explanatory diagram showing the independence of heat generation peaks according to a heat generation curve of Reference Example 1.

FIG. 4 is an explanatory diagram showing non-independence of heat generation peaks according to a heat generation curve of Reference Example 2.

FIG. 5 is a graph showing curing start temperatures and exothermic peak temperatures of Experimental Examples 3 and 4.

FIG. 6 is an explanatory view schematically showing a method for measuring a contact angle.

FIG. 7 is a graph showing a heat generation curve of Experimental Example 5.

FIG. 8 is a graph showing a heat generation curve of Experimental Example 6.

[Explanation of symbols]

S: through hole, D: concave portion, 1; substrate, 2: cured body of paste for filling through hole, 31; peripheral conductor layer, 32; wall surface conductor layer, 33; conductor layer, 4; interlayer insulating layer, 5; Solder resist layer.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H05K 1/11 H05K 1/11 N 3/40 3/40 K (72) Inventor Masahiko Okuyama Mizuho-ku, Nagoya 14-18, Takatsuji-cho F-term in Japan Special Ceramics Co., Ltd. AF05 AF06 AF08 AF15 DB22 DC41 FA02 FA05 JA07 JA08 4J038 DA061 DA131 DA141 DA161 DB001 DB061 DB071 DB081 DD181 DG001 DG262 DJ021 DL001 JA35 JA52 JB04 JB05 JB32 KA03 KA08 PB09 PC02 PC08 5E317 AA24 BB01 BB11 CD27

Claims (9)

[Claims] 1. A paste for filling a through hole used for a printed wiring board, which is measured at 10 ° C. by a differential scanning calorimeter.
When the temperature is increased at a rate of / minute, a heat generation curve having two independent heat generation peaks is obtained, and the curing start temperature determined from the heat generation curve is 90 to 135 ° C, and the through hole filling is characterized in that For paste. 2. The temperature difference between the curing start temperature and the low-temperature-side exothermic peak temperature determined from the exothermic curve is 20 ° C.
The paste for filling a through hole according to claim 1, wherein 3. The paste for filling a through hole according to claim 1, wherein the paste for filling a through hole contains an epoxy resin and a curing agent, and the curing agent is represented by the following general formula (1). Embedded image (However, R ₁ , R ₂ and R ₃ each represent a hydrogen atom or a carbon atom 1
And R ₁ , R ₂ and R ₃ may be the same or different. ) 4. A printed wiring board having a peripheral conductor layer formed on an outer surface of a substrate and a peripheral edge of an opening end of a through hole provided in the substrate, and the surface of the peripheral conductor layer is subjected to an oleophilic treatment. The paste for filling a through hole according to claim 1, which is used. 5. A printed wiring board comprising: a through hole provided in a substrate; and a peripheral conductor layer formed on an outer surface of the substrate and at a periphery of an opening end of the through hole. A printed wiring board, wherein the inside is made of a cured body made of the paste for filling a through hole according to any one of claims 1 to 4. 6. The printed wiring board according to claim 5, wherein the peripheral conductor layer is subjected to an oleophilic treatment. 7. The printed wiring board according to claim 6, wherein a contact angle of the surface of the peripheral conductor layer with water is 90 degrees or more. 8. A lipophilic treatment is applied to the surface of the peripheral conductor layer formed on the outer surface of the substrate and on the periphery of the opening end of the through hole provided in the substrate. 5. A method for producing a printed wiring board, comprising a step of filling the paste for filling a through hole according to any one of 1 to 4, and thereafter heating and curing the paste for filling a through hole. . 9. The contact angle of water on the surface of the peripheral conductor layer after the lipophilic treatment is 90 degrees or more.
The method for producing a printed wiring board according to the above.