JPS63120784A - Adhesive composition and method of using same as adhesive - Google Patents

Abstract

PURPOSE:To obtain an adhesive which has excellent stability at ordinary temperature and maintains a uniform and stable semihardened state, by compounding a thermosetting epoxy resin composition, a specified thermosetting epoxymethacrylate resin composition, a filler, and a thixotropic agent so that it has a specified viscosity. CONSTITUTION:A thermosetting epoxy resin composition is mixed with a thermosetting epoxymethacrylate resin composition which does not cure or hardly cures when heated at the curing temperature of the former composition, but cures when heated at a temperature higher than that. This mixture is mixed with a filler and a thixotropic agent to give an adhesive composition having a viscosity at 25 deg.C under a rate of shear of 1sec<-1> with a Brookfield viscometer of 200-500 P and a thixotropy index, defined as (a viscosity under a rate of shear of 1sec<-1>)/(a viscosity under a rate of shear of 100sec<-1>) with a Brookfield B viscometer, of 10-60.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an adhesive used for bonding printed wiring boards to each other, or to bonding a printed wiring board to a base material, copper foil, etc. 1 composition and its use as an adhesive.

[Prior Art] Conventionally, the adhesive sheet used for bonding printed wiring boards and the like is epoxy resin.

A thermosetting resin composition mainly composed of unsaturated polyester resin or the like is impregnated or coated onto a base material, but it can be semi-contained by forming it into a sheet or film and heating it at an appropriate temperature and time. It is produced by making it into a hardened state. Then, the prepreg, sheet, or film produced by the above method is thermocompressed (temporary bonding) by pressing onto one side of the adherend such as a printed wiring board.
After that, the printed wiring board or the like was subjected to mechanical processing, and this was again thermocompression bonded (main bonding) to the other object to be bonded using a press or the like.

However, the above thermosetting adhesive sheet and its adhesion method had the following drawbacks.

First, in order to bring the resin set into the desired semi-cured state homogeneously and with good reproducibility, it was necessary to strictly control manufacturing conditions such as heating temperature and time. Next, since the adhesive sheet is in a semi-cured state, the curing reaction of unreacted resin reactive groups gradually proceeds even at room temperature. Therefore, the storage stability of the adhesive sheet was extremely poor.

Next, the above adhesive sheet has not only adhesive strength but also
In order to suppress the extrusion of the resin to the circuit-forming metal and the edges of the base material, low flowability of the resin is required during heating and pressurization. In this regard, conventional adhesive sheets are made flexible by adding a rubbery component to a thermosetting resin composition, and have both low flowability and adhesive strength. However, since conventional adhesive sheets contain rubber-like components, they have the disadvantage that properties such as heat resistance, moisture resistance, and chemical resistance are greatly reduced.

On the other hand, conventional bonding methods for printed wiring boards, etc. have the following drawbacks.

First, in the conventional bonding method for printed wiring boards, etc., during machining after the temporary bonding described above, a portion of the resin is melted by a heated trill, and this is scattered onto the bonding surface, causing the surface of the printed wiring board to melt. This caused unevenness that should not exist.

Second, with conventional bonding methods for printed wiring boards, etc., it takes too much time from temporary bonding to final bonding, which causes problems such as the resin absorbing moisture and dust adhering to the board surface. was.

[Problems to be Solved by the Invention] The present invention has been made in order to solve various problems in conventional adhesive sheets and bonding methods thereof, as described below. An adhesive composition that can uniformly and stably obtain a semi-cured state, has excellent storage stability at room temperature, has good adhesion at low flowability, and has satisfactory heat resistance, moisture resistance, and chemical resistance. and to provide an adhesion method in which the above adhesive is applied to an adherend by a screen printing method so that there is no unevenness on the surface of the base material and there is no risk of moisture absorption or dust adhesion. .

[Means for Solving the Problems] In order to achieve the above object, as a result of extensive research by the present inventors, the following adhesive composition and its method of use as an adhesive have been developed using conventional methods. I found that it was significantly better than.

That is, the composition of the adhesive composition adopted in the present invention is as follows: "thermosetting epoxy resin composition (I), and this composition (
I) is mixed with a thermosetting epoxy methacrylate resin composition (II) that does not harden or hardens when heated at the curing temperature, but hardens when heated at a temperature higher than that, and a filler and a filler are added to the mixture. An adhesive composition (III) kneaded with a thixotropic agent, which has a viscosity of 200 to 500 PS at a temperature of 25°C and a shear rate of 1 sec-' as measured by a B-type viscometer, and (a shear rate of 1 sec-' as measured by a B-type viscometer). "An adhesive composition characterized by having a thixotropic index of 10 to 60, expressed as: (viscosity at a shear rate of 100 sec-' as measured by a B-type viscometer)", and such a composition As a method of using it as an adhesive for printed wiring boards, etc., there is a method for using ``thermosetting epoxy resin composition (I) and this group JA product (1) that does not harden or does not harden when heated at the curing temperature.'' , a thermosetting epoxy methacrylate resin composition (II) that hardens when heated at a temperature higher than that, and a filler and a thixotropic agent are kneaded into this mixture.
II), whose viscosity is 200 to 500 PS at a temperature of 25°C and a shear rate of 1 sec measured by a B-type viscometer, and (
Viscosity at a shear rate of 1 Sec-' measured by a B-type viscometer)/(B
An adhesive composition having a thixotropic index (viscosity at a shear rate of 100 sec-' measured by a type viscometer) of 10 to 60.

After applying the adhesive composition (III) to the thermosetting epoxy resin composition (I) by applying the adhesive composition (III) to the surface of the printed wiring boards, or the printed wiring board and the base material, or the copper foil by a screen printing method and drying it. The adhesive composition as an adhesive is characterized in that only the thermosetting epoxy resin composition (I) in the adhesive composition (III) is cured by heating at a peaking temperature of How to use it.

Below, the above means of the present invention will be explained in detail.

Thermosetting epoxy resin composition (I) used in the present invention
has an epoxy resin and at least one type of curing agent selected from amine curing agents, polyamide curing agents, and imidazole curing agents as essential components.

First, the epoxy resins used in the present invention include glycidyl ethers of polyhydric phenols such as bisphenol A, bisphenol F, phenol novolac resins, and cresol novolac resins, and glycidyl ethers of polyhydric alcohols such as butanediol and polypropylene glycol. Examples include glycidyl-type epoxy resins such as glycidyl esters of carboxylic acids such as ether, phthalic acid, and tetrahydrophthalic acid, and alicyclic-type epoxy resins obtained by epoxidizing the orphine bond in one molecule with peracetic acid or the like.

The epoxy curing agent used in the present invention is 50 to 12
Those that can cure the epoxy resin sufficiently in the temperature range of 0° C. are selected. For example, aliphatic polyamines such as diethylenetriamine and diethylaminopropylamine, alicyclic polyamines such as menthene diamine and isophorone diamine, metaphenylene diamine, Amine compounds such as aromatic amines such as diaminodiphenylmethane, polyamide compounds produced by condensation of dimer acid and polyamine, fast-curing imidazole compounds such as 2-methylimidazole and 2-ethyl-4-methylimidazole, etc. Can be mentioned.

These hardening agents are preferably those that harden the epoxy resin within the range of 50 to 120°C. This is 50℃
A curing agent that has high curing properties at a lower temperature will have a very short pot life, resulting in poor workability, and if the temperature is higher than 120°C, the curing reaction (II) will also proceed gradually. This temperature range is more preferably 70 to 10
It is desirable to cure the epoxy resin within the range of 0°C to form a vine hardener.

These curing agents are appropriately selected depending on the type of epoxy resin mentioned above and usage conditions.

In addition, a tertiary amine such as benzyldimethylamine, a compound having a phenolic hydroxyl group such as salicylic acid, etc. may be used as a curing accelerator, if necessary.

Next, the thermosetting epoxy methacrylate resin composition (■) used in the present invention contains an epoxy methacrylate resin, a copolymerizable crosslinking agent, and a radical polymerization initiator as essential components.

First, the epoxy methacrylate resin used in the present invention is bisphenol Af! ! Jli or addition reaction product of bisphenol F type epoxy resin and methacrylic acid
Ii, bisphenol type epoxy methacrylate resin which is a product, novolac type epoxy methacrylate resin which is an addition reaction product of phenol novolac epoxy resin or cresol novolac epoxy resin and methacrylic acid, glycidyl ether type epoxy resin of polyhydric alcohol and methacrylic acid. The main component is at least one kind of aliphatic epoxy methacrylate resin which is an addition reaction product with. Further, in the present invention, an epoxy acrylate resin, which is an addition reaction product of these epoxy resins and acrylic acid, can also be copolymerized with an epoxy methacrylate resin and used, if necessary.

Examples of copolymerizable crosslinking agents include unsaturated groups that react with acrylic esters such as diallyl phthalate, triethylene glycol diacrylate, and trimethylene propane triacrylate, and epoxy methacrylate resins such as trimethylolpropane trimethacrylate and polypropylene. A monomer having two or more terminals or a prepolymer thereof can be used. It is preferable to use these copolymerizable crosslinking agents that are hardly volatile at temperatures below 120°C, because if they are volatile, the thermosetting epoxy resin composition (I This is because the copolymerizable crosslinking agent volatilizes and decreases during the curing process.

The copolymerizable crosslinking agent is epoxy methacrylate resin 100
10 to 200 parts by weight, preferably 50 to 200 parts by weight
Preferably it is 100 parts by weight. If it is less than 50 parts by weight, the viscosity of the epoxy methacrylate resin composition (If) becomes high, resulting in poor workability, and if it is more than 100 parts by weight, the performance of the cured product deteriorates, which is not preferable.

Next, the radical polymerization initiator is, for example, cumene hydroperoxide, t-butyl hydroperoxide, dicumyl peroxide, di-t-butyl peroxide, 2
．． Preferred are those that decompose and generate radicals when heated within the range of 100 to 200°C, such as 5-dimethyl-2,5-di-t-butylperoxyhexane. This is because if radicals are generated at a temperature lower than 100°C, the curing of the above (ff) will proceed during the curing of the above (I), and if it is higher than 200°C, workability during bonding will deteriorate, and equipment and fuel costs will be increased. This is because it becomes expensive. More preferably 1
A temperature range of 20"C to 170C is desirable.

Next, the mixing ratio of (I) to (n) is 1/
It is desirable that the ratio is within the range of 9 to 9/1. If it is smaller than 1/9, the surface of the produced adhesive sheet will become extremely sticky, and if it is larger than 9/l, the unreacted content in the adhesive will become sticky. Since the proportion of the above-mentioned (n) is too small, the adhesive strength decreases. More preferably 3/7 to 7/3.

Fillers include fused silica, crystalline silica, alumina,
Examples include aluminum hydroxide, zirconium oxide, zirconium silicate, calcium carbonate, talc, titanium oxide, precipitated barium sulfate, and mica.

Examples of thixotropic agents include fine inorganic powders such as silica and magnesium oxide, metal soaps such as aluminum stearate and aluminum octoate, and organic bentonite. These thixotropic agents are the adhesives of the present invention! lt
It is an important component that has a large effect on the titanium tropic index of objects.

The adhesive composition according to the present invention is a composition containing the above (I), (■), a filler, and a thixotropic agent, but may also contain other colorants, antifoaming agents, etc. as necessary. can. As the colorant to be mixed here, organic pigments, disperse dyes, etc. can be used, and as the antifoaming agent, silicone oil can be used.

The adhesive composition of the present invention has characteristics suitable for forming an adhesive layer by a printing method such as screen printing or stamp printing. In other words, the viscosity at a temperature of 25°C and a shear rate of 1see-' using a B-type viscometer is 200~
500 P S, and (shear rate 1 by type B viscometer)
sec-' viscosity)/(shear rate due to type B clogging 10
The titanium trophic index indicated by the viscosity of 0 sec-' is 1.
It is characterized by being a~60.

Since the adhesive composition of the present invention is a non-Newtonian fluid, in order to limit its viscosity, it is necessary to specify the type of viscometer 8 and measurement conditions. An 85 viscometer was used to measure viscosity, and the measurement conditions were a temperature of 25°C and a shear rate of 1 s.
e(', the adhesive composition of the present invention is 200
It has a viscosity of ~500 PS. Viscosity is zoo
If PS is not swirled, the resin will wrap around the original document during screen printing, causing bleeding, etc. On the other hand, if the viscosity exceeds 500PS, the resin will not come out from the mesh of the screen, causing blurring, etc. For reasons such as ease of printing, a viscosity of 200 to 500 PS is suitable for the printing method. The adhesive layer formed by the screen printing method using the adhesive composition of the present invention is filled between patterns and must also be applied on the patterns, so the viscosity of the adhesive composition is 250
It is more preferable to set it to 350 PS.

Next, we calculated the titasotropic index (shear rate of 1 sec using a B-type viscometer), which has a large relationship with screen printing characteristics.
-' viscosity)/(shear rate 100se by B-type viscometer
The adhesive composition of the present invention has a titasotropic index of 1O to F10, as defined by the viscosity of "c-". If the titasotropic index exceeds 60, the resin will not flow down from the squeegee or scraper when moving the resin with a squeegee or scraper during screen printing, resulting in a so-called blank printing state. For these reasons, the titasotropic index is preferably in the range of lO to 60. In particular, the adhesive layer formed by screen printing using the adhesive composition of the present invention has a pattern and Fill between the patterns,
Moreover, it must be coated on the pattern as well, and it is necessary to minimize the irregularities on the surface of the adhesive layer, so the titasotropic index.

A range of 25 to 5 is more desirable.

Adhesive of the present invention! It is a composition containing an epoxy resin, an epoxy methacrylate resin, a curing agent, a polymerization initiator, a filler, and a thixotropic agent, and has a viscosity and a titasotropic index within a predetermined range, and has a so-called -wavy type. This is not related to distinctions such as two-component type. That is, even in the case of a two-component adhesive composition, the adhesive composition of the present invention includes all adhesives whose viscosity and titasotropic index are within a predetermined range when mixed and used.

[Actions of the Invention] The present invention has the following effects by adopting the above measures.

First, an epoxy resin is generally cured by an addition reaction with a functional group of a curing agent through a ring-opening reaction of an epoxy ring. The curing reaction of an epoxy resin using an amine curing agent, which is a typical curing agent, is shown below.

→R-C■, -CH-C112-N11-R0■ Below margin 01 amount...(1) Next, generally, the curing of thermosetting epoxy methacrylate resin is caused by the generation of radicals due to the decomposition of peroxide, The unsaturated groups undergo radical polymerization and harden. The curing reaction formula of epoxy methacrylate resin is shown below.

R-0-0-R'-→ R-0・+・0-R'
・-(2) HU Lllz (a L
U - is also 12-+1 110H In the present invention, the reactivity of the epoxy group and curing agent shown in formula (1) and the decomposition of peroxide shown in formula (2) are in a temperature range that is different from each other. The epoxy resin curing agent and peroxide are selected so that That is, thermosetting epoxy resin set Jj2. contains an epoxy group and a curing agent that exhibits high reactivity within the range of 50 to 120°C. Thing (I)
il! exhibits high decomposition within the range of 100 to 200°C and generates radicals! A thermosetting epoxy methacrylate resin composition (II) containing S oxide is mixed.

Furthermore, a filler and a thixotropic agent are kneaded into this mixture,
Adjust to the desired viscosity and titanium tropic index. Furthermore, by changing the mixing ratio of (I) and (■), any semi-cured state can be selected. This means that the flowability of the resin can be selected arbitrarily.

Next, a detailed explanation will be given of the parts of the adhesive composition of the present invention.

As mentioned above, the adhesive composition (III) can be in a semi-cured state as desired by changing the mixing ratio of (I) and (II), and can be heated at 50 to 120°C.
When heated within this range, (II) hardly reacts, so a stable semi-cured adhesive layer can always be obtained without strict control of the curing conditions. Furthermore, since (rI) does not react even at room temperature, the storage stability of the adhesive layer is excellent.

Next, by applying adhesive using screen printing, machining can be performed before gluing, and there is no resin scattering due to drilling, and if pressed immediately after printing, it can be left in the air. Problems such as moisture absorption of the resin and dust adhesion to the surface of the base material that occur during the process are reduced.

[Example] Next, the present invention will be specifically explained using examples.

First, mixing examples of the adhesive composition of the present invention will be described, but the present invention is not limited to the following mixing examples. In the following formulation examples, all "parts" mean "parts by weight."

Formulation Example 1 100 parts of bisphenol A epoxy resin (average molecular weight 950, E-1001 manufactured by Yuka Ciel Co., Ltd.), 12 parts of Laromin C-260 (manufactured by BASF Corporation) as a curing agent.
．． Mix 5 parts and use this as composition (I). In addition, bisphenol A type epoxy methacrylate resin (average molecular l 1000, manufactured by Nippon U-Pica Co., Ltd., Neo Ball 8104)
), 75 parts of diallyl phthalate (manufactured by Osaka Soda Co., Ltd.) as a copolymerizable crosslinking agent, and 1.8 parts of Bark Mill D (F) (manufactured by NOF Corporation) as a radical polymerization initiator were mixed. Let (II) be the set r&thing. And (I
) composition and (If) composition were mixed in a ratio of 2=1, and further 33 parts of titanium oxide, 8.3 parts of talc, and 8.3 parts of fine silica powder were added.
parts were mixed and kneaded using a Miki roll mill.

Formulation Example 2 In Formulation Example 1, NK Kostel T was used as a copolymerizable crosslinking agent.
100 parts of MPT (manufactured by Shin Nakamura Kogyo Co., Ltd.), 2 parts of Verbutyl D (manufactured by NOF Corporation) as a radical polymerization initiator, 50 parts of fused silica as a filler, and 5.0 parts of fine magnesium oxide powder as a thixotropic agent. Formulation example 1 except for using 5 parts
Same as .

Formulation Example 3 Formulation Example 1 was the same as Formulation Example 1 except that 61 parts of talc was used as a filler and 5.5 parts of fine silica powder was used as a thixotropic agent.

Formulation Example 4 In Formulation Example 1, 40 parts of crystalline silica was used as a filler, and 7.5 parts of fine silica powder was used as a thixotropic agent. The procedure is the same as in Formulation Example 1 except that 1 is used. The storage stability, moisture resistance, and heat resistance of Formulation Examples 1 to 4 were evaluated using the following methods, and the results are shown in Table 1.

(Storage stability): The amount of M generated before and after heat treatment at 100° C. for 2 hours was measured by DSC, and changes were determined from the formula shown below.

Table 1 Storage stability = (8 Calorific value before treatment - Calorific value after heat treatment) (Heat resistance):
Beer strength after 240 hours at 150°C.

(After humidity resistance): Beer strength after 100 hours at PCT (121″C2 atm).

Further, the viscosity and titasotropic index of each formulation example are shown in Table 2.

Table 2 Next, an example of the adhesive method of the present invention will be described in more detail using the composition of Formulation Example 1 as an adhesive composition, but the adhesive method of the present invention is limited to the following example. It's not something you can do.

First, as shown in FIG. 1, the composition (10) of Formulation Example 1 was applied onto a machined printed circuit board (21) by a conventional screen printing method.

At this time, when using a stainless steel screen (mesh opening t78pm, emulsion thickness 40ILm), there may be problems such as bleeding due to resin wrapping around the original sheet, blurring due to poor resin coming out from the screen mesh, and printing. There were no occurrences of anyone occurring at the time of release and at the time of release. Furthermore, after the composition (10) of Formulation Example 1 was applied by the screen printing method, it reliably entered the periphery of the conductor circuit (22) formed on the printed circuit board (21).

The composition applied by the screen printing method as described above (
10) is cured as shown in Figure i2 to obtain the composition (
10) was used as an adhesive layer (11). This adhesive layer (11
) on top of the bonded substrate (23
) were stacked and heated and pressurized using a heating plate.

The printed wiring board formed as described above exhibited extremely excellent characteristics as a semiconductor device fi (20) as shown in FIG. That is, the bonded substrate (23) is bonded onto the printed circuit board (21) with an adhesive layer (11) made of the composition (IO), thereby forming the conductor circuit (22).
When protecting the conductor circuit (22), since the bonded board (23) is reliably bonded onto the printed circuit board (21) by the adhesive layer (11), the conductor circuit (22) is reliably protected. It is. In addition, in Fig. 4, the symbol (24
) indicates a silicon chip to be mounted on the printed circuit board (21) h, and symbol (25) indicates a sealing resin for protecting this silicon chip (24).

[Effects of the Invention] As is clear from the Examples, the following advantages were found in the adhesive and the bonding method of the present invention.

1,'\ Since (n) hardly reacts at the heating temperature used to form the cured state, an adhesive layer always in a uniform semi-cured state can be obtained.

2. Since (II) does not react even at room temperature, an adhesive with extremely excellent storage stability can be obtained.

3. The resin flow can be determined by the mixing ratio of (1) and (II) above, and a stable flow can always be obtained.

4. Since it does not contain rubbery components, it is heat resistant, moisture resistant,
Excellent chemical resistance.

-5. To apply adhesive by screen printing method,
Machine processing can be performed before printing, there is no unevenness on the substrate surface due to resin scattering6, and the process from printing to pressing is completed in a short time, so there is no risk of moisture absorption or dust adhesion during the process.

[Brief explanation of the drawing]

From FIG. 1 to FIG. 3, the adhesive composition of the present invention is applied to a printed circuit board by a screen printing method. It is an enlarged sectional view. Explanation of symbols 10...adhesive composition, ti-...adhesive layer, 21-
- Printed circuit board, 22--conductor circuit, 23--laminated board. 24... Silicon chip, 25-... Sealing resin.

Claims (1)

[Claims] 1) A thermosetting epoxy resin composition (I) that does not cure or is difficult to cure when heated at the curing temperature of this composition (I), and when heated at a higher temperature. and a thermosetting epoxy methacrylate resin composition (II) to be cured, and a filler and a thixotropic agent are kneaded into this mixture, the adhesive composition (III) comprising: a temperature of 25° C. as measured by a B-type viscometer; Shear speed 1sec^-^
1 has a viscosity of 200 to 500 PS, and a thixotropic index expressed as (viscosity at a shear rate of 1 sec^-^1 by a B-type viscometer)/(viscosity at a shear rate of 100 sec^-^1 by a B-type viscometer) is 10. -60. 2) The thermosetting epoxy resin composition (I) contains an epoxy resin and at least one curing agent selected from an amine curing agent, a polyamide curing agent, or an imidazole curing agent as essential components. The adhesive composition according to claim 1, characterized in that: 3) Claim 1, characterized in that the curing agent contained in the thermosetting epoxy resin composition (I) is a curing agent capable of curing the epoxy resin within the range of 50 to 120°C. The adhesive composition according to item 1 or 2. 4) The thermosetting epoxy methacrylate resin composition (II) is a bisphenol-type epoxy methacrylate resin obtained by adding methacrylic acid to a bisphenol-type epoxy resin, or a novolak-type epoxy methacrylate resin obtained by adding methacrylic acid to a novolak-type epoxy resin. Alternatively, at least one resin selected from aliphatic epoxy methacrylate resins obtained by adding methacrylic acid to glycidyl ether type epoxy resins of polyhydric alcohols, a copolymerizable crosslinking agent, and a radical polymerization initiator are required. Claims 1 to 3 are characterized in that
The adhesive composition according to any one of Item 3. 5) The radical polymerization initiator contained in the thermosetting epoxy methacrylate resin composition (II) is 100 to 20
The adhesive composition according to any one of claims 1 to 4, characterized in that it decomposes within a temperature range of 0°C and generates radicals. 6) A patent characterized in that the mixing ratio of the thermosetting epoxy resin composition (I) to the thermosetting epoxy methacrylate resin composition (II) is within the range of 1/9 to 9/1. An adhesive composition according to any one of claims 1 to 5. 7) A thermosetting epoxy resin composition (I) and a thermosetting type that does not harden or hardens when heated at the curing temperature of this composition (I), but hardens when heated at a higher temperature. An adhesive composition (III) prepared by mixing the epoxy methacrylate resin composition (II) and kneading a filler and a thixotropic agent into this mixture, at a temperature of 25°C and a shear rate of 1 sec as measured by a B-type viscometer. The viscosity of 1 is 200~
500PS, and (shear rate 1se by B-type viscometer)
c^-^1 viscosity)/(shear rate by B-type viscometer 10
An adhesive composition having a thixotropic index of 10 to 60 (viscosity of 0 sec^-^1) is applied to printed wiring boards, or to the surface of a printed wiring board and a base material or copper foil by a screen printing method. After drying, the thermosetting epoxy resin in the adhesive composition (III) is heated by heating the adhesive composition (III) at the curing temperature of the thermosetting epoxy resin composition (I). A method of using an adhesive composition as an adhesive, characterized by curing only the resin composition (I).