JP2005302904A - Paste for filling hole and method for filling through-hole or bottomed hole of substrate by using paste - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide paste for filling a hole filling through-holes or bottomed holes formed at narrow intervals. <P>SOLUTION: At least one kind epoxy resin of 100 pts. wt. is selected from a group composed of: a glycidyl amine type epoxy having an epoxy equivalent of 80 to 110 g/eq and a viscosity of 25 dPa s or less; a bisphenol A type epoxy having the epoxy equivalent of 150 to 250 g/eq and the viscosity of 150 dPa s or less; a chelate denatured epoxy having the epoxy equivalent of 150 to 250 g/eq and the viscosity of 80 dPa s or less; the bisphenol F type epoxy having the epoxy equivalent of 150 to 250 g/eq and the viscosity of 40 dPa s or less; and a rubber modified epoxy having the epoxy equivalent of 170 to 350 g/eq and the viscosity of 100 dPa s or less. An imidazole curing agent of 1.5 to 40 pts. wt. and a foaming agent of 0.1 to 10 pts. wt. having a grain size of 30 μm or less are contained to one kind or two kinds or more of the epoxy resins of 100 pts. wt.. A thermal expansion coefficient at 25 to 260°C after a curing is less than 2.0%. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a hole filling paste used for manufacturing a printed wiring board and a method for filling a through hole or a bottomed hole of a substrate using the paste.

  As electronic devices have become smaller and lighter in recent years, high-density mounting of components has become an indispensable technology. In printed wiring boards intended for high-density mounting, in order to obtain conduction between the front and back surfaces of the insulating substrate, through holes are provided, the walls are plated, and the through holes are filled with a filler. A technique that enables mounting of components is also used above.

  For example, as shown in FIG. 1, a printing method is used as a method for filling a through hole with a filling material. For example, as shown in FIG. 1, (a) a step of plating the wall surface of the through hole, and (b) a hole filling printing. A step, (c) a step of curing the filler and smoothing the surface by polishing, and (d) a step of forming a lid plating is added if necessary.

  However, in recent years, with the increase in the density of the substrate, the interval (pitch) between the through holes is narrowed, and as shown in FIG. 2, the paste 5 between adjacent through holes is often connected on the surface at the time of curing. In such a case, problems such as unpolished residue and elongation of the substrate due to an increase in polishing load occur, which is a problem. The same applies to the paste 6 filled in a hole having a bottomed structure as shown in FIG. 3 (hereinafter referred to as a bottomed hole).

As a method for preventing the surface linking of the paste, the paste before curing that adheres to the surface after filling is also scraped off using a squeegee, and in this case, the problem is that the cured paste is connected on the surface as described above. However, as shown in FIG. 4, the surface of the cured paste 7 tends to be recessed from the surface of the substrate after curing, causing a problem in surface smoothness. In this regard, in Japanese Patent Laid-Open No. 2-284680, a liquid material mixed with an inert gas is pressurized and discharged from the nozzle tip, and the liquid material is foamed at the time of discharge. Filling with a foam material is disclosed. However, since this method requires a special device for foaming at the time of filling and foams simultaneously with discharge, it cannot be applied to ordinary screen printing or the like.
Japanese Laid-Open Patent Publication No. 2-284680

  The present invention has been made in view of the above, and when filling through holes or bottomed holes provided at narrow intervals, problems such as polishing residue due to paste connection and substrate elongation due to increased polishing load occur. The object is to provide no hole filling paste. Specifically, since the paste expands moderately when cured, it is a hole-filling paste that is easy to polish without removing dents even if the paste is removed and cured after applying the paste. The object of the present invention is to provide a hole-filling paste that can be stored in a conventional manner and can be applied by ordinary screen printing or the like. Moreover, it aims at providing the filling method of a through-hole or a bottomed hole using this.

  In order to solve the above problems, the hole filling paste of the present invention has a polyfunctional glycidylamine type epoxy resin having an epoxy equivalent of 80 to 110 g / eq and a viscosity of 25 dPa · s or less, and an epoxy equivalent of 150 to 250 g / eq. Bisphenol A type epoxy resin having an eq viscosity of 150 dPa · s or less, a chelate-modified epoxy resin having an epoxy equivalent of 150 to 250 g / eq and a viscosity of 80 dPa · s or less, an epoxy equivalent of 150 to 250 g / eq and a viscosity of 40 dPa · s Epoxy resin 100 which is a blend of one or two or more selected from the group consisting of bisphenol F type epoxy resin of s or less and rubber-modified epoxy resin having an epoxy equivalent of 170 to 350 g / eq and a viscosity of 100 dPa · s or less 1.5 to 40 parts by weight of imidazole curing agent with respect to parts by weight And 0.1 to 10 parts by weight of a foaming agent having a particle size of 30 μm or less, and after curing, the coefficient of thermal expansion at 25 ° C. to 260 ° C. is less than 2.0% (Claim 1). .

The hole-filling paste of the present invention further contains 200 to 600 parts by weight of metal powder having an apparent density of 2.0 g / cm ³ or more and a particle diameter of 1 to 100 μm with respect to 100 parts by weight of the epoxy resin. (Claim 2).

  Further, instead of the metal powder or in addition to the metal powder, it may further contain 5 to 600 parts by weight of an inorganic filler having a particle size of 0.1 to 100 μm with respect to 100 parts by weight of the epoxy resin. (Claim 3).

  The method for filling a through hole or bottomed hole in a substrate according to the present invention includes a step of filling any of the above hole filling paste into the through hole or bottomed hole of the substrate, and a through hole or bottomed surface on the surface of the substrate. Removing the excess hole filling paste protruding from the hole, foaming and hardening the hole filling paste in the through hole or the bottomed hole after removing the excess hole filling paste, and filling the hole And polishing the surface of the substrate after foaming and curing the adhesive paste to remove the cured product protruding from the surface of the substrate (claim 4).

  According to the hole filling paste of the present invention and the filling method of through holes or bottomed holes using the same, it is possible to fill through holes and bottomed holes provided at narrow intervals without causing various problems. A highly reliable printed wiring board can be easily obtained.

  In the hole filling paste of the present invention, as the epoxy resin, polyfunctional glycidylamine type epoxy resin such as metaxylenediamine type and aminophenol type, bisphenol A type epoxy resin, bisphenol F type epoxy resin, chelate modified epoxy resin In addition, a blend with one or more epoxy resins selected from rubber-modified epoxy resins is preferably used.

  The bisphenol A type epoxy resin has an epoxy equivalent (gram number of resin containing 1 g equivalent of an epoxy group) of 150 to 250 g / eq, and a viscosity (hereinafter the same) in a B type viscometer is 150 dPa · s or less. It is preferable. When the epoxy equivalent is less than 150 g / eq, curing shrinkage is large, and cracks and peeling from the copper foil may occur. When it exceeds 250 g / eq, it is difficult to obtain desired heat resistance. On the other hand, when the viscosity exceeds 150 dPa · s, the viscosity of the paste increases and the workability deteriorates.

  For the same reason, the polyfunctional glycidylamine type epoxy resin has an epoxy equivalent of 80 to 110 g / eq and a viscosity of 25 dPa · s or less, and the bisphenol F type has an epoxy equivalent of 150 to 250 g / eq and a viscosity. For those having a viscosity of 40 dPa · s or less, for a chelate-modified epoxy resin, those having an epoxy equivalent of 150 to 250 g / eq and a viscosity of 80 dPa · s or less, and for a rubber-modified epoxy resin, an epoxy equivalent of 170 to 350 g / eq and a viscosity of 100 dPa -The thing below s is preferable respectively.

  As described later, when nickel powder or copper powder is used as the metal powder, wetting with the epoxy resin is poor, and when added to the epoxy resin, the viscosity rises. In such a case, a chelate-modified epoxy resin should be added. Thus, wetting is improved and an increase in viscosity is suppressed. Further, the addition of a low-viscosity polyfunctional glycidylamine solves the problem of viscosity increase while maintaining heat resistance. Thereby, a low-viscosity paste is possible even without a solvent.

  The blend ratio of the polyfunctional glycidylamine type epoxy resin and the other epoxy resin is preferably 10 to 70 parts by weight of the polyfunctional glycidylamine type epoxy resin in 100 parts by weight, and 20 to 50 parts by weight. It is more preferable. If it is less than 10 parts by weight, the desired heat resistance cannot be obtained, and if it exceeds 70 parts by weight, curing shrinkage is large, and cracks and peeling from the copper foil may occur.

  In the epoxy resin, one or more of alkyd resin, melamine resin, and phenol resin may be mixed for the purpose of modification as long as there is no problem in properties such as adhesion and heat resistance (swelling). .

  The kind of the imidazole-based curing agent used in the present invention is not particularly limited, and examples thereof include 2-phenyl-4,5-dihydroxymethylimidazole, 2-heptadecylimidazole, 2,4-diamino-6- (2′- Undecylimidazolyl) ethyl-S-triazine, 1-cyanoethyl-2-phenylimidazole, 2-phenylimidazole, 5-cyano-2-phenylimidazole, 2,4-diamino-6- [2'-methylimidazolyl- (1 ′)]-Ethyl-S-triazine isocyanuric acid adduct, 2-phenylimidazole isocyanuric acid adduct, 2-methylimidazole isocyanuric acid adduct, 1-cyanoethyl-2-phenyl-4,5-di (2-cyanoethoxy) ) Alkyl group, ethyl in imidazole ring such as methylimidazole Anomoto, hydroxyl, compounds azine is added, and the like. Among these, a cyanoethyl group adduct and an azine adduct are preferable from the viewpoint of adhesion to the copper foil in the through hole portion.

  The imidazole curing agent is preferably blended in an amount of 1.5 to 40 parts by weight, more preferably 3 to 20 parts by weight with respect to 100 parts by weight of the epoxy resin. When the number of added parts is less than 1.5 parts by weight, curing becomes insufficient and physical properties are deteriorated. On the other hand, when the amount exceeds 40 parts by weight, the degree of thickening with time is large, resulting in a decrease in printability. In addition, the paste thickens during storage and workability deteriorates, and the hole cannot be sufficiently filled with the paste.

  As the curing agent, in addition to the imidazole curing agent, other curing agents such as a phenol curing agent may be further used. The amount of the phenolic curing agent used is preferably about 0.5 to 20 parts by weight with respect to 100 parts by weight of the epoxy resin.

  Next, an organic foaming agent can be used as the foaming agent. Examples thereof include azo compounds such as azodicarbonamide and azobisisobutyronitrile, nitroso compounds such as dinitrosopentamethylenetetramine, and paratoluene. And hydrazide compounds such as sulfonyl hydrazide. Two or more foaming agents may be used.

  The particle size of the foaming agent is preferably 30 μm or less. When it exceeds 30 μm, each bubble becomes large, which may cause a dent on the surface.

  As for the compounding quantity of a foaming agent, 0.1-10 weight part is preferable with respect to 100 weight part of epoxy resins. If the amount is less than 0.1 parts by weight, sufficient foaming cannot be obtained, and a dent is generated after curing, so that a smooth substrate may not be obtained. When the amount exceeds 10 parts by weight, there arises a problem that the bulk strength is lowered and the size of the void cannot be controlled.

  In this invention, a metal powder (metal filler) and an inorganic filler can be used as needed.

When metal powder is used, nickel powder or copper powder is preferred because it is inexpensive and does not adversely affect copper plating. Apparent density is preferably 2.0 g / cm ³ or more metal powders, 2.2 g / cm ³ or more, more preferably, 3.5 g / cm ³ or more is more preferable. When this is less than 2.0 g / cm ³ , the viscosity of the paste increases and the workability deteriorates. Moreover, 1-100 micrometers is preferable and, as for a particle size, 2-30 micrometers is more preferable. When metal powder is used, it is integrated with the plated copper foil layer to provide an anchor effect.

  The metal powder is preferably blended in an amount of 200 to 600 parts, more preferably 300 to 500 parts, with respect to 100 parts of the epoxy resin. When the amount is less than 200 parts, a sufficient anchor effect cannot be obtained, and peeling may occur between the plated copper foil layer and the paste. When the amount exceeds 600 parts by weight, workability may decrease due to thickening.

  When using an inorganic filler, the kind is not particularly limited, and examples thereof include silica, calcium carbonate, talc and the like. In consideration of wettability with resin, printability, and anchor effect in plating, an inorganic filler such as substantially spherical silica that is finer than metal powder and enters between metal powder and metal powder is preferable. These inorganic fillers function to prevent the paste from blurring and sagging during curing and to suppress thermal expansion.

  The particle size of the inorganic filler is preferably 0.1 to 100 μm. The inorganic filler is blended in an amount of 5 to 600 parts by weight with respect to 100 parts of the epoxy resin.

  The shape of the metal powder and the inorganic filler is not particularly limited, and examples thereof include a dendritic shape, a spherical shape, and a flake shape. Moreover, only 1 type may be used for an inorganic filler and a metal powder, or 2 or more types may be mixed and used for them.

  The paste for hole filling of the present invention preferably has a coefficient of thermal expansion at 25 ° C. to 260 ° C. after curing of less than 2.0%. The thermal expansion coefficient can be controlled mainly by selecting the epoxy resin.

  The hole-filling paste of the present invention can be used for both through holes and bottomed holes, and can be used both with and without lid plating.

  Next, the filling method of the present invention is a method of filling the hole filling paste of the present invention into a through hole or a bottomed hole. (1) The hole filling paste is filled into a through hole or a bottomed hole of a substrate. A step of filling, (2) a step of removing excess hole-filling paste before curing protruding from the through-hole or bottomed hole on the surface of the substrate, and (3) after removing the excess hole-filling paste A step of foam-curing the hole-filling paste in the through-hole or the bottomed hole, and (4) a step of polishing the substrate surface after foam-curing the hole-filling paste and removing the cured product protruding from the substrate surface Is included at least.

  In order to remove excess paste in the step (2), a spatula, a squeegee or the like may be used as appropriate, and the method is not particularly limited.

  The curing conditions and the like in the above step (3) are determined by the epoxy resin to be used and the like, but usually 1 is about 150 to 180 ° C. and about 30 to 60 minutes.

  In the paste foam cured product 8 obtained through the step (3), the swollen portion protrudes from the surface of the substrate as shown in FIG. The amount of swelling can be adjusted according to the type and amount of the foaming agent. By setting the amount to an appropriate amount, polishing in the step (4) is facilitated, and occurrence of problems associated with polishing can be suppressed.

  Examples of the present invention are shown below, but the present invention is not limited thereto.

[Examples 1 to 20, Comparative Examples 1 to 12]
For filling holes by mixing the epoxy resin, foaming agent, imidazole curing agent, metal powder (copper powder) and inorganic filler (silica) shown in Table 1 and Table 2 in the proportions (parts by weight) shown in each table. A paste was prepared and the viscosity was measured with a B-type viscometer. Details of each component are as follows.

Epoxy resin A: Chelate-modified epoxy resin, epoxy equivalent 150-250 g / eq, viscosity 80 dPa · s or less Epoxy resin B: Rubber-modified epoxy resin, epoxy equivalent 170-350 g / eq, viscosity 100 dPa · s or less Epoxy resin C: polyfunctional Glycidylamine type epoxy resin, epoxy equivalent 80-110 g / eq, viscosity 25 dPa · s or less Foaming agent A: hydrazodicarbonamide, particle size 20 μm
Blowing agent B: 4,4-oxybis (benzenesulfonylhydrazide), particle size 4 μm
Foaming agent C: N, N-dinitrosopentamethylenetetramine, particle size 15 μm
Foaming agent D: azodicarbonamide, particle size 7 μm
Imidazole-based curing agent: Shikoku Kasei Kogyo Co., Ltd., 2PZ-CN
Copper powder: Apparent density 3.2 g / cm ³ , average particle size 7 μm, dendritic silica: Apparent density 0.4 g / cm ³ , average particle size 0.5 μm, spherical

  A paste having the composition shown in Tables 1 and 2 was filled in a through hole with a hole diameter of φ = 0.6 mm provided on a glass epoxy substrate having a thickness of 1.0 mm by screen printing, and an excess paste protruding from the substrate surface. Was removed with a spatula, pre-heated at 100 ° C. for 30 minutes, and then fully cured at 180 ° C. for 60 minutes. The amount of swelling due to foaming of the obtained cured product (height from the substrate at the top of the cured product, dimension a in FIG. 5) was measured.

  After removing excess paste on the substrate by polishing, chemical copper plating and electrolytic copper plating were performed in this order to produce a chip-on-through-hole substrate.

  This chip-on-through-hole substrate was dipped in a solder bath at 260 ° C. for 30 seconds, the expansion coefficient was measured, and the presence of burst dents and lid plating peeling was examined. The results are shown in Tables 1 and 2.

  The hole filling paste of the present invention and the method of filling through holes or bottomed holes using the paste are used for manufacturing various printed wiring boards.

It is a schematic cross section which shows the filling method of the through-hole of the conventional board | substrate. It is a schematic cross section which shows the state with which the paste was connected between the adjacent through-holes on a board | substrate. It is a schematic cross section which shows the state with which the paste was connected between the adjacent bottomed holes on a board | substrate. It is a schematic cross section which shows the dent state of the hardened | cured material hardened after removing the excess paste on a board | substrate using the conventional paste. It is a schematic cross section which shows the swelling state of the foaming hardened | cured material hardened after removing the excess paste on a board | substrate using the paste of this invention.

Explanation of symbols

1 ... Substrate 2 ... Plating 3, 5, 6, 7, 8 ... Hole filling paste (or cured product thereof)
4 ... Lid plating

Claims (4)

Polyfunctional glycidylamine type epoxy resin having an epoxy equivalent of 80 to 110 g / eq and a viscosity of 25 dPa · s or less, bisphenol A type epoxy resin having an epoxy equivalent of 150 to 250 g / eq and a viscosity of 150 dPa · s or less, epoxy equivalent Is a chelate-modified epoxy resin having a viscosity of 150 to 250 g / eq and a viscosity of 80 dPa · s or less, a bisphenol F type epoxy resin having an epoxy equivalent of 150 to 250 g / eq and a viscosity of 40 dPa · s or less, and an epoxy equivalent of 170 to 350 g / eq. For 100 parts by weight of an epoxy resin that is a blend with one or more selected from the group consisting of rubber-modified epoxy resins having a viscosity of 100 dPa · s or less,
It contains 1.5 to 40 parts by weight of an imidazole curing agent, and 0.1 to 10 parts by weight of a foaming agent having a particle size of 30 μm or less,
A hole-filling paste characterized by a coefficient of thermal expansion at 25 ° C. to 260 ° C. of less than 2.0% after curing. 2. The hole according to claim 1, further comprising 200 to 600 parts by weight of metal powder having an apparent density of 2.0 g / cm ³ or more and a particle diameter of 1 to 100 μm with respect to 100 parts by weight of the epoxy resin. Filling paste. The hole-filling paste according to claim 1, further comprising 5 to 600 parts by weight of an inorganic filler having a particle size of 0.1 to 100 μm with respect to 100 parts by weight of the epoxy resin. Filling the hole filling paste according to any one of claims 1 to 3 into a through hole or a bottomed hole of a substrate;
Removing the excess hole filling paste protruding from the through hole or the bottomed hole on the surface of the substrate;
Foam curing the hole filling paste in the through hole or bottomed hole after removing the excess hole filling paste; and
Polishing the substrate surface after foam-curing the hole-filling paste and removing the cured product protruding from the substrate surface.

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