JPS61103906A - Curing of conductive resin by laser beam irradiation - Google Patents

Abstract

PURPOSE:To accomplish bonding through curing to materials of low-heat resistance such as plastics, by coating a conductive filler-incorporated specific polymerizing composition followed by laser beam irradiation to effect selective and instantaneous bonding for the objective portion. CONSTITUTION:A polymerizing composition comprising (A) at least one active duble bond-carrying polymerizable compound [e.g., 2,2-bis(4-methacryloxyphenyl) propane], (B) a polymerization initiator and (C) conductive filler (e.g., silver powder) is coated between conductive members followed by laser beam irradiation on said coated portion to effect curing through polymerization. Preferably, in addition to the above components (A), (B) and (C), (D) a colorant is incorporated followed by laser beam irradiation in a similar way to effect decoloring during the curing.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method of curing conductive resin by irradiating a laser beam, and is applicable to applications where it is difficult to use normal bonding methods due to some conditions, or where heat is applied to areas other than the bonded area. A polymeric composition having a predetermined composition is applied between conductive members, etc., which is not allowed, and a laser is irradiated to the applied area in a limited manner,
This invention relates to a method of instantaneously curing adhesive. .

(Prior art) Recently, materials for electronic components have become diverse.
The use of materials with low heat resistance such as plastics and non-solderable materials such as solid carbon has increased significantly, and many thick electrical adhesives have been developed to replace solder. As conductive adhesives, composites of epoxy, phenol, urethane, acrylic resins, etc. containing conductive fillers such as metal powder and carbon are generally used, and these are cured between conductive members such as between terminals. As methods, room temperature curing methods and heat curing methods are widely used, and ultraviolet curing methods, visible light curing methods, electron beam curing methods, etc. are also being considered.

(Problems to be Solved by the Invention) However, while each of the above-mentioned curing means has its advantages, it also has some drawbacks.

First, the room temperature curing method cures even at room temperature, so it is advantageous for bonding parts that do not like heat, but the curing time is very long (
It has the disadvantage of low physical strength and low adhesive strength.

On the other hand, in the heat curing type, areas other than those to be cured are inevitably heated, resulting in extremely poor thermal efficiency. Also,
This curing method cannot be used when the substrate is plastic, paper, etc. that cannot be heated, or it is not preferable to heat it, or when the substrate is distorted due to dimensional accuracy.

Next is the ultraviolet curing method, which involves irradiating ultraviolet rays onto a composition containing an ultraviolet aggravating agent such as benzoin alkyl ether as a polymerization initiator, and curing does not occur until ultraviolet rays are irradiated. , there are no restrictions on handling time. Since it is non-heating, it can be applied to substrates that cannot be heated, but ultraviolet rays are
It has poor curing properties and cannot be cured to a large depth. It is difficult to apply to opaque materials containing conductive fillers, etc. Undercut areas are not irradiated with ultraviolet rays and curing does not occur. Mercury lamps have many problems, such as being susceptible to deterioration (short lifespan).

In addition, the visible light curing method is a method that improves the drawbacks of the ultraviolet curing method, and is a method in which visible light is irradiated to a composition containing a photoinitiator such as dl-camphorquinone as a polymerization initiator. In this method, a xenon lamp or a halogen lamp is used as a light source, and the wavelength is 350~
Since it uses visible light of 550 nm, compared to ultraviolet rays,
Safety is significantly improved and lamp life is significantly longer. However, in other aspects, it has the same drawbacks as the ultraviolet curing method.

Furthermore, electron beam curing requires a polymerization initiator.
'This is a method of irradiating the polymer composition with the energy of an electron beam, but it cannot achieve a large curing depth, requires an inert gas for curing, and requires consideration of secondary X-rays and ozone. There are drawbacks such as:

(Means for Solving the Problems) The present invention solves the problems of conventional adhesive methods, especially between electrically sensitive parts (such as bonding between terminals) in electronic circuits, etc. The purpose of the present invention is to provide a method for instantly curing and bonding a polymer composition between electrically conductive members by irradiating a laser beam in a limited manner to only the portions to be cured.

The configuration of the present invention will be explained below.

That is, the first invention has at least one active double bond.
A laser whose main feature is to apply a polymer composition composed of a polymerizable compound, a polymerization initiator, and a conductive filler between conductive members, and to irradiate the applied part with laser light to polymerize and harden it. A second invention is a method of curing a conductive resin by light irradiation, and the second invention is a composition comprising a polymerizable compound having at least one active double bond, a polymerization initiator, a conductive filler, and a coloring agent. This is a method of curing conductive resin by irradiating laser light, which consists of irradiating an object with laser light to polymerize and harden it, and decolorizing it during curing.

Here, the polymerizable composition used in the present invention is a polymerizable composition containing a polymerizable compound having at least one active double bond, a polymerization initiator, and a conductive filler as essential components, and which is at room temperature. These include types that harden gradually under the atmosphere, anaerobic types that harden by blocking air, and types that harden by heating. A polymerizable compound having at least one active double bond is a compound having at least one active double bond in its chemical structure, including monomers, prepolymers, mixtures thereof, and copolymers. It has a chemical form such as. Examples of monomers include alkylene acrylates or methacrylates such as methyl acrylate, methyl methacrylate, ethyl acrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, ethylene glycol monoacrylate, Alkylene and polyalkylene glycol monoacrylates or methacrylates such as ethylene glycol monomethacrylate and triethylene glycol monomethacrylate, acrylates having a hydroxyl group or epoxy group in lower alkylenes such as 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, and glycidyl methacrylate. Or alkylene diacrylate or methacrylate such as methacrylate, ethylene diacrylate, ethylene dimethacrylate, butylene diacrylate, butylene dimethacrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, triethylene glycol diacrylate, triethylene glycol dimethacrylate, trimethylol Examples include alkylene and polyalkylene glycol di- and triacrylates or methacrylates such as propane triacrylate and trimethylolpropane trimethacrylate, and aromatic diacrylates or methacrylates corresponding to the following general formula.

In the general formula, R1-Rz represents hydrogen or a methyl group, R3 and R4 represent a hydrocarbon chain, which hydrocarbon chain may be substituted with one or more hydroxyl groups, A is aromatic, For example, in the crosslinked phenylene represented by the general formula of Hue, B represents a lower alkylene such as methylene, ethylene, ethylidene, isopropylene, butylene, etc. Typical examples of these include 2,2-bis(P-2
'Hydroxy-3' methacryloxypropoxyphenyl)propane, 2I2-bis(4-methacryloxyphenyl)propane, 2.2-bis(4-methacryloxypropoxyphenyl)propane, 2.2-bis(4-methacryloxypoly ethoxyphenyl)propane, etc.

Examples of prepolymers include polyester-diacrylate or methacrylate, polyurethane-diacrylate or methacrylate, and polyamide-diacrylate or methacrylate.
Diacrylate or methacrylate, epoxy
Examples include diacrylate and methacrylate. The above monomers and prepolymers can be used by mixing or copolymerizing several components depending on the desired consistency, properties, etc.

Furthermore, organic peroxides and azo compounds are used as polymerization initiators. Here, preferred organic peroxides include acetyl peroxide, propionyl peroxide, octanoyl peroxide, decanoyl peroxide, lauroyl peroxide, 3.3.5-
) diacyl peroxides such as remethylhexanoyl peroxide, succinic acid peroxide, benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, m-trioyl peroxide,
t-Butyl peroxy bivalate, t-butyl peroxy neodecanate, t-butyl peroxy 3.5.7-
) Contains peroxy esters such as trimethylhexanate, t-butyl peroxylaurate, and t-butyl peroxybenzoate, and hydroperoxides such as cumene hydroperoxide, t-butyl hydroperoxide, and diisopropylbenzene hydroperoxide. It will be done. Furthermore, a typical azo compound is azobisisobutyronitrile. These polymerization initiators are 1
A species may be used alone or two or more species may be used in combination. Further, the amount added can be in a wide range from 0.05 to 20% by weight based on the compound having an active double bond, but a range of 0.1 to 10% is particularly desirable.

If you want the polymerizable composition to have room-temperature curability, you can use a reducing agent such as a tertiary amine, naphthenate, mercaptan, or organometallic compound in addition to the above-mentioned organic peroxide. good. Examples of these are N,N"-dimethylaniline, N,N'-diethylaniline, N,N"
-dimethyl-P-)luidine, N,N'-diethyl-P-toluidine, N,N'-diethyl-m-)luidine, N-methyl-N'-β-hydroxyethylaniline, N,N'-di(β- Hydroxyethyl Jl/)P-
) luidine, cobalt naphthenate, methyl mercaptan, triethyl aluminum triethyl boron, diethyl zinc, etc. These may be used alone or in combination of two or more. The amount added varies depending on the organic peroxide used, but is preferably in the range of 1 to 100% by weight based on the organic peroxide. In addition, other redox catalysts include hydrogen peroxide - Fe g + base, persulfate -
It is also possible to use the N a HS O: l system. The conductive filler includes metal powder, carbon, etc., and the metal powder includes powdered, plate-like, and flake-like metals or alloys such as gold, silver, copper, aluminum, nickel, stainless steel, copper, bronze, etc. , fiber-shaped ones can be used. The filling amount varies depending on the required conductivity, but is preferably in the range of 10 to 60% by volume.

If the metal powder is smaller than 10% by volume, the conductive filler will not be able to form a bond even after curing, and will not exhibit conductivity at all, or will be unstable even if conductivity is obtained. On the other hand, if the amount of metal powder exceeds 60% by volume, the cured product loses its physical and chemical stability, and strong connections between the metal powders are not obtained and the conductivity becomes unstable. It is preferable that the particle diameter is 100 μm or less; if it is more than 100 μm, the contact resistance will increase and the conductivity will deteriorate. It also uses carbon.

When the amount is added, the amount added is preferably in the range of 10 to 60% by weight.
Preferably, particles with a particle size of 10 to 200 mμ are applicable. Furthermore, additives such as polymerization inhibitors, inorganic fillers, plasticizers, colorants, etc. may be added to the polymer composition consisting of the above-mentioned active double bond-containing compound, polymerization initiator, and conductive filler. I don't mind if you do that.

The polymerization inhibitor is added to prevent early polymerization of the monomers and prepolymers described above and to improve storage stability, and can be selected from known hydroquinone derivatives. Polymerization inhibitors that can be used for this purpose include hydroquinone, hydroquinone monomethyl ether, butylated hydroquinone, catechol, catechol methyl ether, t-butylcatechol, pyrogallol, pyrogallol monomethyl ether, pyrogallol dimethyl ether, and the like.

These polymerization inhibitors are preferably contained in an amount of 0.001 to 1 part by weight based on 100 parts by weight of the above-described active double bond-containing compound.

In addition, inorganic fillers are effective in adjusting the viscosity of the polymer composition, imparting thixotropic properties, and improving the abrasion resistance, compressive strength, and water resistance of the cured product, and include silicon dioxide, aluminum oxide, titanium dioxide, α- Common inorganic fillers such as quartz, zirconium dioxide, silicon nitride, and glass powder can be used. Although the filling amount can be set within a wide range depending on the application and characteristics, it is preferably contained in a range of 20 to 400 parts by weight per 100 parts by weight of the compound having an active double bond.

In addition, when using the above-mentioned inorganic filler, the surface of the filler is coated with a coupling agent to improve the bond between the filler and the binder or prepolymer, and to improve the mechanical properties of the cured product. It is preferable to treat with

Coupling agents that can be used for this purpose include both silane-based and titanium-based coupling agents. Silane coupling agents are effective in improving the mechanical strength and rigidity of cured products, and titanium coupling agents are effective in improving flexibility of cured products. These may be used alone or in combination of two or more. Silane cassopring agents that can be used for this purpose include vinyltrichlorosilane, vinyltris(β-methoxyethoxy)silane, vinyltriethoxysilane, vinylmethoxysilane, γ-methacryloxypropyltrimethoxysilane, and β(3,4-epoxycyclohexyl). ethyltrimethoxy)silane, γ
-Glycidoxyprobyltrimethoxysilane, N-β
(aminoethyl γ-noaminopropyltrimethoxy)silane, N-β(aminoethyl)γ-aminopropyl(methyldimethoxy)silane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, Examples include γ-chloropropyltrimethoxysilane. In addition, examples of titanium-based coupling agents include isopropyl triisostearoyl titanate, isopropyl tridodecylbenzenesulfonyl titanate, isopro and lutris (dioctyl pyrophosphate) titanate, and tetra(2,2-diallyloxymethyl-1-butyl)bis(ditris). These include dodecyl phosphite) titanate and bis(dioctyl pyrophosphate) titanate. All of these can be surface treated using a conventional method (the appropriate amount to be used is about 1% by weight of the filler).

Further, a plasticizer may be added to the above-mentioned composition as needed, and preferred plasticizers include phthalic acid esters such as dimethyl phthalate, diethyl phthalate, dibutyl phthalate, and dioctyl phthalate, and dimethyl glycol phthalate. , ethyl phthalyl ethyl glycolate, methyl phthalyl ethyl glycolate, and other glycol esters.

Furthermore, in the present invention, as described above, a coloring agent is added to a polymer composition composed of a polymerizable compound having at least one active double bond, a polymerization initiator, and a conductive filler. Apply between parts,
When the coated area is irradiated with laser light, the coloring agent is applied.

One of the features of this method is that the coloring is decolored during curing so that the state of the cured adhesive can be objectively grasped. Here, as the coloring agent that can be added, for example, organic pigments such as Lysol Rubin BCA, Lake Red C, Lake Red CBA, Brilliant Lake Red R1 Permanent Red F5R, Sudan ■, Orange ■, Oil Red
There are azo dyes such as O, Orange SS, and anthraquinone dyes such as Sudan Blue B1 Alizuline Barber SS and Quinizarine Green SS. Further, the amount of these colorants added is preferably in the range of 0.001 to 0.02% by weight, particularly 0.005 to 0.01% by weight, based on the main components. If the amount added is small, the coloring property will be poor, and if the amount added is large, it will be difficult to identify the change to a decolored state. The decolorization property decreases and it becomes difficult to completely decolorize, making it difficult to check the cured state. In addition, based on the experimental fact that the Nd:YAG laser is particularly selective with respect to colors and is very well absorbed in black, blue, and green colors, it is recommended that the composition be colored with these colors. If this is done, the amount of energy required for the laser beam to be irradiated can be kept low, so it is more optimal from an energy saving standpoint.

Furthermore, although any laser source can be used as the laser that can be used in the present invention, either a solid laser or a gas laser is preferable. and,
As the solid laser, a Nd:YAG laser is particularly preferred, and as a gas laser, a CO□ laser is most preferred. YAG (yttrium aluminum garnet) is currently the most commonly used solid-state laser material because it is not only a physically and chemically excellent crystal, but also optically uniform and large crystals can be obtained. Nd:YAG lasers using it have been put into practical use for micro-drilling, micro-welding, scribing, etc. from an early stage. When this Nd:YAG laser is used, it is possible to continuously oscillate light with a wavelength of 1.06 μm, and a high-speed repetitive pulse Q switch has also been put into practical use. On the other hand, CO2 lasers are also widely used for processing because they have high oscillation efficiency, are compact and can provide high output. This Co2 laser oscillates light with a wavelength of 10.2 μm, and like the Nd:YAG laser, it can perform continuous oscillation or high-speed repetitive pulse oscillation.

All of these lasers can be guided through flexible glass fibers, making them extremely easy to operate.Also, the beam diameter can be adjusted, so they can be used accurately on any complex shape or minute part. It also becomes possible to easily irradiate. On the other hand, the wavelength of the Nd:YAG laser and the Co2 laser differs by a factor of 10, and there are also some differences in the optical characteristics accordingly. For example, Nd:YAG laser has better material permeability,
The hardening depth increases accordingly. On the other hand, CO, laser,
- has poor substance permeability, but has a strong tendency for energy to concentrate near the surface (and can be cured with low energy density.The energy required to cure and bond the above-mentioned polymeric composition with a laser is: The type and blending ratio of the seven polymers or prepolymers that make up the composition, the type and amount of polymerization initiator added, the presence or absence of inorganic fillers, plasticizers, and colorants, and the amount added thereof, the type of conductive filler and its addition. Although it varies greatly depending on the amount, the type of laser used, irradiation conditions, etc., when a Nd:YAG laser is used, complete curing can be achieved at an energy density of approximately 10 to 800 J/d. especially,
As a conductive filler, carbon black was added to the polymer composition. As mentioned above, Nd:
Since the YAG laser has good light absorption for black, the energy density of the laser can be kept extremely low to IOJ/cd, resulting in more energy savings. However, when it is expected to know the point of hardening due to decolorization, the conductive filler to be added is other than a carbon-based black filler such as carbon black.

In addition, when using a COz laser, 1 to 50 J/
With the energy density of cd, the aforementioned Nd:YA
.

Cured adhesion almost the same as that of G laser can be obtained.

When irradiating the laser, any of continuous irradiation, repeated Siharth irradiation, and Q-switch pulses may be employed. However, when using continuous irradiation or Q-switch pulse irradiation, the temperature will rise rapidly as the irradiation time passes, so if the power density is too high,
Foaming may occur on the surface of the composition. However, on the contrary,
If the power density is too low, the irradiation time becomes long and the cooling effect is accordingly large, resulting in a significant decrease in efficiency. For this reason, when using a Nd:YA-G laser, the power density should be 5 to 20 W/cd, and when using a CO□ laser, the power density should be 1 to 30 W/cd.
It is preferable to set it within the range of d. On the other hand, when using the repeated c) L/S method, the pulse width and interval can be set according to the purpose of use, but if the interval is too long, the influence of the cooling effect will become large and the energy efficiency will drop significantly. Therefore, it is preferable to limit the time to 2 seconds or less.

The larger the pulse width, the better the energy efficiency, but if the pulse width is made smaller and the number of repetitions is increased, the rapid rise of the surface of the composition can be suppressed and troubles such as foaming can be prevented. The beam diameter can be arbitrarily set depending on the size, shape, etc. of the target composition, but preferably a method is employed in which a minute beam is irradiated in a scanning manner to partially cure and bond.

Next, an application example of the laser curing method according to the present invention will be shown. In the laser curing method, only the polymerizable composition is irradiated with laser light, so it is difficult to cure between conductive members such as plastics and paper that cannot be heated, or between conductive members where it is undesirable to heat from the standpoint of dimensional accuracy. The filled or applied composition can be instantly cured and bonded between the conductive members without the influence of heat. In addition, by utilizing the properties of laser light that can be irradiated remotely, it is possible to apply compositions that are filled or applied between conductive members in environments that are difficult for humans to work with (e.g., high temperature, low temperature, vacuum, high pressure). Even if instant curing is required (e.g., under diluted air or toxic gas), it is also possible to cure and bond by remotely irradiating laser light from a safe location.

(Effects of the invention) When the curing adhesive method using laser beams of the present invention is adopted,
Since it can be cured and bonded instantly by irradiation with laser light, it will not be cured and bonded instantly unless it is irradiated with laser light, so there are very few restrictions on handling operation time. In addition, by using a heat source called a laser beam, it is possible to heat the area to be cured and bonded in a limited manner, and the area to be cured and bonded can be instantly cured and bonded.
The effect of heat on the board can be minimized, and problems such as distortion can be avoided. Therefore, the curing adhesive method of the present invention can be applied to substrates that cannot be heated, such as plastics and paper. Furthermore, although the present invention is a method that uses light rays, the light energy is converted into heat, and 2. Due to its excellent substance permeability, it can be cured and bonded to even fairly thick materials depending on the irradiation conditions. In addition, if a self-curing or anaerobic polymeric composition is selected, only the upper layer can be cured with laser light, and the interior can be cured slowly at room temperature, allowing for a deep cure. can be expanded infinitely. By adopting this partial (upper layer only) curing method, less energy is required.
Moreover, a cured adhesive with little internal strain can be obtained. Furthermore, the laser curing method has excellent features not found in ultraviolet or visible light curing methods, such as being able to cure and bond to a considerable depth even colored opaque materials containing conductive fillers. There is. In addition, in the past, in order to instantaneously cure adhesive using a normal heat source, for example, hot air, the temperature of the hot air had to be considerably high, and there was a risk of foaming in the composition. As a means of polymerization and curing, laser light irradiation is used to increase the temperature of the composition.

Because it can be easily controlled, it can be cured and bonded instantly, without causing any foaming phenomenon.

Furthermore, the laser beam can be guided by a flexible glass fiber and the beam diameter can be adjusted, making it extremely easy to operate and can be used to accurately and easily work on any complex shape or minute part. It also becomes possible to irradiate in a scanning manner.

Further, by applying the method of the present invention in the field of precision electronic components such as IC circuits that are sensitive to heat, it is possible to bond only predetermined locations without damaging the circuit.

Furthermore, laser beams have very good directionality, and in particular in conditions without an atmosphere, such as outer space, the beam hardly spreads, so it can be irradiated remotely, and polymer compositions can be produced in outer space. A wide range of development applications can be expected as a means of curing adhesive.

In addition, when a colorant is added to a composition, the color is decolored at the same time as curing, so it is possible to objectively check the point of curing, making it possible to avoid excessive irradiation with laser light and to minimize laser irradiation. It is safe and energy-saving.

Furthermore, by adding to the method of the present invention a means for automatically confirming the point of decolorization using a color sensor or the like, curing adhesion can be automatically controlled, and automation in the field of electronic components can be achieved.

(Example) Example 1 A mixed monomer consisting of 50 parts of 2.2-bis(P-2''hydroxy-31methacryloxypropoxyphenyl)propane, 40 parts of triethylene glycol dimethacrylate, and 10 parts of trimethylolpropane trimethacrylate, Hydroquinone monomethyl ether 0.001,
1 part benzoyl peroxide, 3 parts silver powder with an average particle size of 5μ
00 parts were added to obtain a paste-like composite. A portion of it was filled into a Teflon mold with an inner diameter of 41 m and a height of 5 dragons.
On its surface, N with irradiation power 20W1 beam diameter 6IIjl
d: YAG laser was irradiated for 5 seconds. Then, the compressive strength and compressive modulus of the material obtained by this irradiation were determined using an Instron universal machine at a loading rate of 0.5 w/min. The obtained result is that the compressive strength is 15.1 kg/Tsuru 2
, the compression modulus was 497.5 kg/Tsuru2.

Furthermore, it has good electrical conductivity and is considered to be fully applicable to joining electronic components that require electrical conductivity. In addition,
The electrical conductivity can be selected quite freely depending on the amount of conductive filler (silver in this example) added to the composition.

Example 2 Amino blank 10B was added to the same composition as in Example 1.
．． 0.015 parts was added to connect terminals (between conductive members) of electronic circuits. Next, the connection point was irradiated with a Nd:YAG laser with an irradiation power of 10 W and a beam diameter of 6 fl, and after 5 seconds, decolorization of the connection point was confirmed and the irradiation was stopped.

The electronic circuit obtained in this manner exhibited electronic conductivity similar to that of conventional terminal-to-terminal connection by soldering, and did not exhibit any defects. Considering this, the adverse effect of heat on the vicinity of the connection point, which was often seen in the case of conventional soldering connections between terminals, is essentially due to the fact that the connection point is not cut, and the hardening of the adhesive at the connection point. Since the condition of the product can be confirmed objectively through decolorization, the introduction of color sensors will not only enable automatic control in this type of field, but will also greatly reduce the risk of defective products during quality control inspections. There is hardening that can be easily checked.

Claims (2)

[Claims] (1) A polymer composition composed of a polymerizable compound having at least one active double bond, a polymerization initiator, and a conductive filler is applied between conductive members, and the applied portion is irradiated with laser light. A method for curing a conductive resin by irradiating a laser beam, characterized by polymerization and curing. (2) A composition containing a colorant in addition to a polymerizable compound having at least one active double bond, a polymerization initiator, and a conductive filler is applied between conductive members, and a laser beam is applied to the applied area. is irradiated to polymerize and harden,
A method for curing a conductive resin by irradiating a laser beam, characterized by decolorizing it during curing.