JP2000204263A - Thermosetting resin composition and mounting method for electronic part using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a thermosetting resin composition which has relatively high thixotropic properties even when asbestos is not used and which is suitable for application with a dispenser by compounding a thermosetting resin with a curing agent and a filler of which at least a part is a hydrophobic inorganic powder having the surface processed to be hydrophobic. SOLUTION: This composition comprises a thermosetting resin, a curing agent, and a filler of which at least a part is a hydrophobic inorganic powder having the surface processed to be hydrophobic. Preferably, at least a part of the surface of the hydrophobic inorganic powder is subjected to a surface treatment to enhance the cohesiveness; that is, the thixotropic properties of the composition can be adjusted by suitably controlling the surface state of the hydrophobic inorganic powder. The thixotropic properties, when they are too high, can be reduced by converting a part of the hydrophobic inorganic powder into spherical particles. Preferably, the hydrophobic inorganic powder has a particle size of 10-20 nm and is contained in a concentration of 2.0-2.4 wt.%. Preferably, the particle size of a filler other than the hydrophobic inorganic powder is 10-20 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermosetting resin composition used for manufacturing electronic components and mounting electronic components on circuit boards, and a method for mounting electronic components using the same.

[0002]

2. Description of the Related Art Conventionally, various resin compositions have been used for sealing materials for electronic components and adhesives for temporarily fixing components. In particular, curable resin compositions are often used because of their properties. The method of curing the curable resin composition includes a photocuring method in which a curing reaction is performed by irradiating ultraviolet rays or the like, a thermosetting method in which a curing reaction is performed by heating, and a curing reaction by exposing to a room temperature for a certain time. And a room temperature curing method.
Examples of the photocurable resin composition used in the photocuring method include an acrylic resin composition. As the thermosetting resin composition used in the thermosetting method, there is an epoxy resin composition and the like. The basic composition of the thermosetting epoxy resin composition is composed of an epoxy resin, a curing agent, a filler, and a coloring agent, and a thixotropic agent is added as necessary. As the curing agent, amine adduct, polyamide, polymercaptan, or the like is used, and as the filler, silica, talc, mica, clay, or the like is generally used.

Here, FIG. 1 shows an example of a process of applying an adhesive made of the above resin composition onto a circuit board using a dispenser. First, as shown in FIG. 1A, the adhesive 1 contained in the syringe 3 is pushed out from the nozzle 2 at the tip of the syringe by the float 4 which has received the air pressure 5 instantaneously. Next, as shown in FIG. 1B, the syringe 3 is lowered to attach the adhesive 1 to the circuit board 6. Then, as shown in FIG. 1C, the syringe 3 moves up to complete the application, and the syringe 3 moves to another place (FIG. 1D). After repeating this application process, the electronic component is mounted on the portion where the adhesive 1 has been applied,
Further, the adhesive is cured in a heating furnace, and finally, soldering is performed to complete the mounting of the electronic component.

What is important in the above coating process is the ease with which the adhesive is cut when the syringe 3 is raised, that is, in FIGS. 1B to 1C. This is because if the adhesive is hard to be cut, the adhesive 1 expands in a thread shape when the syringe 3 rises as shown in FIG. 2, and when the syringe 3 moves in this state, the adhesive 1 becomes a thread shape as shown in FIG. This is because a phenomenon called stringing occurs in which the extended portion falls down sideways and the adhesive adheres to unnecessary portions. Also,
If the thread-like portion breaks during the fall,
As shown in (b), a phenomenon of splashing, which adheres in the form of droplets to the side of the application portion, occurs. in this way,
If the adhesive adheres to the electrodes of the circuit board due to stringing or splashing, the solder may not be wet, which causes a problem of causing defective soldering.

[0005] In general, a resin composition in which powder particles are dispersed in a liquid resin is fluidized when stirred, and its viscosity is reduced.
When left unattended, the particles agglomerate due to frictional force and lose fluidity, increasing the viscosity (thixotropic properties).
It is simply called "thixotropic property". ). The thixotropy is determined by the thixo ratio (the ratio of the viscosity at low shear to the viscosity at high shear; hereinafter, the rotor speed 0.5 with respect to the viscosity at a rotor speed of 5 rpm using an E-type viscometer).
(ratio of viscosity at rpm). And, since the resin composition is more easily cut as the thixo ratio is higher and the occurrence of the above-described soldering failure can be prevented, conventionally, a thixotropy-imparting agent such as asbestos or an aliphatic amide is added to the resin composition. It is blended to give the resin composition an appropriate thixotropic property.

[0006]

However, asbestos is harmful, and it is necessary to consider use of a harmless thixotropy-imparting agent from the necessity of taking measures for safety and health and environmental protection. In the above-mentioned application step, the viscosity of the resin composition used as the adhesive is also important. If the viscosity is too high, even if air pressure is applied to the float, it becomes difficult for the adhesive to come out of the nozzle, which causes an empty shot or an insufficient amount of application. As a result, there is a possibility that defects such as missing parts may be caused. In order to suppress the occurrence of such a defect, it is necessary to adjust the viscosity of the adhesive to a viscosity suitable for using a dispenser. In particular, in the high-speed coating process,
It is required to lower the viscosity of the adhesive. At this time, to prevent the adhesive strength of the cured adhesive from decreasing,
The adhesive had to be reduced in viscosity without reducing the compounding ratio of the filler. In view of the above problems, the present invention has a relatively high thixotropy without reducing the compounding amount of the filler and without using harmful asbestos, and is suitable for an adhesive suitable for application using a dispenser. An object is to obtain a thermosetting resin composition. It is another object of the present invention to provide a method for mounting an electronic component using the thermosetting resin composition.

[0007]

The present invention provides a thermosetting resin, a curing agent and a filler, wherein at least a part of the filler is a hydrophobic inorganic powder whose surface is subjected to a hydrophobic treatment. Characteristic thermosetting resin composition. In this case, it is preferable that at least a part of the surface of the hydrophobic inorganic powder is subjected to particle surface treatment to enhance cohesion. Also,
Preferably, the hydrophobic inorganic powder is a spherical inorganic powder. Further, the particle diameter of the hydrophobic inorganic powder is 10 to 20 nm.
It is preferred that Further, the thermosetting resin composition preferably contains the hydrophobic inorganic powder in an amount of 2.0 to 2.4% by weight. Further, the thermosetting resin is preferably an epoxy resin. Preferably, the epoxy resin contains at least one low-viscosity crystalline epoxy resin. On the other hand, it is preferable that the filler further contains a spherical inorganic powder. Further, the filler other than the hydrophobic inorganic powder preferably has a particle size of 10 to 20 μm.

Further, the present invention provides a step of applying the thermosetting resin composition on a circuit board using a dispenser.
The present invention also relates to a method for mounting an electronic component, comprising a step of mounting an electronic component on the applied adhesive, and a step of curing the applied adhesive by heating to fix the component on a substrate. In this case, in the applying step, it is preferable to control the application speed of the dispenser in accordance with the viscosity of the adhesive.

[0009]

DETAILED DESCRIPTION OF THE INVENTION As described above, the thermosetting resin composition for an adhesive of the present invention is most effective when a hydrophobic inorganic powder whose surface is subjected to hydrophobic treatment is used as a part of a filler. Has features. This hydrophobic inorganic powder, because the hydrophobic group present on the surface is not disturbed by water molecules,
It exhibits the property of being easily aggregated in the thermosetting resin composition. Therefore, the thermosetting resin composition of the present invention containing a hydrophobic inorganic powder exhibits thixotropy such that the composition loses fluidity when left to stand and its viscosity decreases when stirred. Therefore, it can be suitably used as an adhesive applied using a dispenser. That is, since the hydrophobic inorganic powder functions as a thixotropy-imparting agent conventionally carried by asbestos in a resin composition, in the present invention, it is not necessary to mix harmful asbestos as a thixotropy-imparting agent. . Since the hydrophobic inorganic powder has low water absorption, it also has an advantage that deterioration of the obtained thermosetting resin composition can be prevented.

First, a thermosetting resin, a curing agent and a filler which are components of the thermosetting resin composition of the present invention will be described below. The thermosetting resin used in the present invention is not particularly limited. For example, bisphenol A epoxy resin, bisphenol F epoxy resin, cresol novolak epoxy resin, phenol novolak epoxy resin, cycloaliphatic epoxy resin, Epoxy resins such as a chain aliphatic epoxy resin, a glycidyl ester type epoxy resin, and a glycidylamine type epoxy resin, and the like, and these may be used alone or in any combination within a range not to impair the effects of the present invention Can be. In addition, it is preferable to use a liquid epoxy resin such as a bisphenol A type epoxy resin or a bisphenol F type epoxy resin from the viewpoint that the obtained thermosetting resin composition is excellent in light resistance and heat resistance. When the epoxy resin is used, if at least a part thereof contains a low-viscosity crystalline epoxy resin such as a bisphenol F epoxy resin, the viscosity of the obtained thermosetting resin composition can be reduced. It is suitable. In other words, when a resin component having different viscosity characteristics is used in combination, it becomes possible to manufacture a target electronic component or a resin composition suitable for a dispenser application speed,
The reliability of mounting is improved. For example, a resin mixture obtained by mixing a bisphenol F type epoxy resin with a bisphenol A type epoxy resin has a higher thermosetting when air pressure is applied to the float in FIG. It is easy to discharge the conductive resin composition. In this case, there is also an effect that the adhesive strength of the resin composition after heat curing is higher than that of the case where only the non-crystalline resin is used.

Next, the curing agent will be described. The curing agent used in the present invention can be appropriately selected by those skilled in the art according to the type of the thermosetting resin. For example, an amine-based curing agent, an acid anhydride-based curing agent, a polyamide-based curing agent, and the like can be given. Further, a microcapsule-type curing agent or the like can also be used.

The filler used in the present invention is not particularly limited as long as it has been conventionally used, and various organic fillers and inorganic fillers can be used. Then, in order to improve the thixotropy, the hydrophobic inorganic powder is used as a part of the filler. Examples of the organic filler include wood flour, cellulose fiber, bakelite shavings, urea resin shavings, starch, walnut powder, and aliphatic amide. The inorganic filler is not particularly limited, and examples thereof include silica, talc, and mica. The particle shape of these fillers is not particularly limited, and examples thereof include a sphere, a scale, and a fiber. Among them, the point that the strength after curing is increased by increasing the filling rate of the filler, the point that the viscosity can be reduced by reducing the friction between the fillers during the flow of the obtained thermosetting resin composition, and A spherical shape is preferred because a microcapsule-type curing agent is hardly damaged when used. In addition, when only such a filler is used, even if the obtained thermosetting resin composition is left standing and stirred, its viscosity remains low, and the thixotropy described above cannot be imparted. . Therefore, in the present invention, a hydrophobic inorganic powder is used as a part of the filler so that the viscosity of the obtained thermosetting resin composition increases when it is left unattended. The filler is vacuum-dried from the viewpoint of preventing the cured product from being deteriorated by water molecules.
It is preferable to remove the water by a method such as heating and drying.

Next, the hydrophobic inorganic powder used as a part of the filler will be described. This hydrophobic inorganic powder plays the most important role of imparting thixotropy to the thermosetting resin composition of the present invention. Such a hydrophobic inorganic powder can be obtained by subjecting the surface of the inorganic powder to a hydrophobic treatment. The reason why inorganic powders are used instead of organic powders is that they are chemically inert and do not have a risk of chemically reacting or dissolving during surface treatment.

First, the inorganic powder used for the hydrophobic inorganic powder in the present invention may be any one having a hydrophilic group on its surface. Specifically, silica, talc, mica and the same as the above-mentioned inorganic filler are used. And so on. Among them, it is preferable to use the same filler as the filler because it is chemically stable and hardly causes a reaction or the like. Further, as the shape of the inorganic powder, the filling rate is high, the strength after curing is increased, the friction between the fillers during flow can be reduced and the viscosity can be reduced, and the microcapsule type curing agent is hardly damaged. From the viewpoint, it is preferably spherical. Further, the particle diameter of the inorganic powder is preferably about 10 to 20 nm from the viewpoint of imparting an appropriate thixotropy to the thermosetting resin material. The filler other than the hydrophobic inorganic powder may have a particle size of 10 to 20 μm in order to secure the same adhesive strength as described above and to prevent the occurrence of cracks.

[0015] The hydrophobic treatment means that a hydrophilic group present on the surface of the inorganic powder is replaced with a hydrophobic group. For example, taking silica as an example, the --OH of the silanol group present on the silica surface is replaced with a hydrophobic group such as a methyl group.
Examples of such a hydrophobic group include an alkyl group, an aromatic alkyl group, and a halogenated alkyl group. The method of the hydrophobizing treatment is not particularly limited. For example, surface treatment with a surfactant having an alkyl group or a silane compound such as dialkylenedihalogenated silane, surface treatment by microencapsulation, and surface treatment by a chemical reaction Processing and the like. In the surface treatment method using a surfactant, after immersing the inorganic powder in a water-soluble surfactant, a water-soluble calcium salt or barium salt is added to precipitate the surfactant as a calcium salt or barium salt, By filtering and drying, the surface of the inorganic powder can be made hydrophobic. Examples of the surface treatment method by microencapsulation include a spray drying method, a simple coacervation method, and an interface reaction method. For example, in the spray drying method, an inorganic powder is dispersed in a solution in which a surface treatment substance such as dimethyldichlorosilane is dissolved, and the dispersion is instantaneously dried or solidified to perform surface treatment. On the other hand, there is a method in which a chemical reaction is performed on the surface of the inorganic powder to introduce a hydrophobic group to the surface of the inorganic powder by covalent bonding.

Next, in the present invention, it is preferable that at least a part of the surface of the hydrophobic inorganic powder is subjected to particle surface treatment to enhance cohesion. This is because the thixotropic property of the obtained thermosetting resin composition is adjusted by appropriately controlling the surface state of the hydrophobic inorganic powder contained in the thermosetting resin composition. That is, the thixotropic properties of the obtained thermosetting resin composition may be too high depending on the types of the thermosetting resin, curing agent and filler used in the present invention. If the thixotropy is too high, there is a problem that unevenness in application amount and blanking occur.In such a case, by reducing the friction between fillers as a part of the hydrophobic inorganic powder as spherical particles. The thixotropy is reduced.

The proportion of each component in the thermosetting resin composition of the present invention is preferably 100% by weight in total from the viewpoint of optimizing the viscosity, thixo ratio and adhesive strength. Thermosetting resin 35-40% by weight Hardener 20-22% by weight Filler 35-45% by weight Hydrophobic inorganic powder 2.0-2.4% by weight. In particular, the compounding ratio of the filler excluding the hydrophobic inorganic powder is preferably in this range from the viewpoint of securing an adhesive strength of 1.5 kgf per an application diameter of 0.6 mm per dot. In addition, in addition to the above components, for example, conventionally known components such as pigments can be added as long as the effects of the present invention are not impaired. Further, the thermosetting resin composition of the present invention can be produced by kneading the above components by a conventionally known method. In addition, from the viewpoint of removing air bubbles mixed during kneading and injection into the syringe, it is preferable to perform defoaming by two kinds of methods: vacuum stirring and defoaming after kneading, and centrifugal defoaming after injection into the syringe.

The thixotropic ratio of an adhesive suitable for application using a dispenser is about 4.5 to 6.5. In particular, when the dispensing speed is 0.12 to 0.7 seconds / point,
A thixotropic ratio of about 5.0 to 6.5 is suitable. The thixo ratio of the thermosetting resin composition of the present invention obtained as described above is in the range of 5.5 to 6.5, and is suitable for application using a dispenser.

The present invention further provides a step of applying an adhesive comprising the thermosetting resin composition on a circuit board using a dispenser, a step of mounting an electronic component on the applied adhesive, and a step of applying the applied adhesive. The present invention also relates to a method for mounting an electronic component, comprising a step of curing the agent by heating to fix the component on a substrate. In this case, in the application step, the application speed of the dispenser can be controlled according to the viscosity of the adhesive. in this way,
By fixing the components mounted on the substrate with the adhesive, it is possible to prevent the components from shifting or missing during soldering. Further, by controlling the dispensing speed in accordance with the viscosity of the adhesive to be used and the electronic component to be mounted, it is possible to shorten the lead time of the mounting process and improve the mounting accuracy. For example, at a dispensing speed of 0.3 to 0.15 seconds / point, the viscosity of the adhesive (hereinafter referred to as 30 ° C. using an E-type viscometer with a cone angle of 3 °)
The viscosity at the second rotation when the rotor is rotated at 0.5 rpm. ) Is 250-500 Pa · s, and when the dispensing speed is 0.12-0.07 sec / point, 15
0 to 250 Pa · s is suitable. For example, if the electronic component is a small chip component, the viscosity is 150 to 250P.
a.s resin composition is used. Dispense speed 0.12
Apply at ~ 0.07 sec / point. In the case of a large component such as a semiconductor package, a high-viscosity adhesive may be applied at a dispensing speed of about 0.28 seconds / point, and the component shape and position may be recognized and accurately mounted. In addition to the above examples, various applications are possible. Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited thereto.

[0020]

<Example 1> A mixture of bisphenol A type epoxy resin, bisphenol F type epoxy resin and polymercaptan microcapsule type curing agent (Plainset XBM-1000, manufactured by Ajinomoto Co., Inc.)
And the fillers shown in Table 1 using a propeller stirrer
The mixture was kneaded under the conditions of 00 rpm and 25 minutes, and then defoamed by two methods of vacuum stirring defoaming and centrifugal defoaming to produce the thermosetting resin composition 1 of the present invention. Table 1 shows the mixing ratio of each component constituting the obtained thermosetting composition 1. Filler A was obtained as follows. That is, by treating the surface of a spherical silica powder having a particle diameter of 12 nm (Aerosil RY200 manufactured by Nippon Aerosil Co., Ltd.) with dimethyldichlorosilane, -OH at the tip of a silanol group on the powder surface is modified with a methyl group to make it hydrophobic. Treatment to obtain a hydrophobic inorganic powder. Due to the presence of silanol groups on the surface of the hydrophobic inorganic powder, the particles are liable to agglomerate and tend to exhibit thixotropy after dispersion. The filler B has a particle size of 10 to
The water content of a 12 μm amorphous silica sintered product (Fuselex E-II manufactured by Tatsumori Co., Ltd.) was adjusted to 60 ° C., 13 mmHg,
It is a silica sintered product obtained by heating and drying under vacuum for 3 hours. As filler C, scaly talc having a particle size of 8 μm (Mistron CB manufactured by Nippon Mistron Co., Ltd.)
Was removed by heating and vacuum drying at 60 ° C. and 13 mmHg for 3 hours. Then, when the viscosity of the obtained thermosetting resin composition was measured, 30
The temperature was 400 Pa · S, and the thixo ratio was 6.6. This is put into the dispenser, and the dispensing speed is set to 0.
The coating was performed in a dot shape having a coating diameter of 0.6 mm at 28 seconds / point. Then, the stringing occurrence rate ((number of stringing occurrences / total number of dots) × 100), the scattering occurrence rate ((the number of scattering occurrences /
The total number of dots) × 100) and the occurrence rate of empty spaces ((the number of generated empty spaces / total number of dots) × 100) were determined. Table 1 shows the results.
Shown in

Example 2 As a thermosetting resin component, a low-viscosity bisphenol F epoxy resin (Epicoat 806 manufactured by Yuka Shell Epoxy Co., Ltd., viscosity: 7.
Except that 0 Pa · s) was used, a thermosetting resin composition 2 of the present invention was produced in the same manner as in Example 1. The viscosity of the obtained thermosetting resin composition was 220 Pa · s, and the thixo ratio was 6.3. Dispensing speed 0.12
It was applied in the form of dots having an application diameter of 0.6 mm at a rate of seconds / point, and each defect occurrence rate was measured in the same manner as in Example 1. Table 1 shows the results.

Example 3 Further, spherical silica having a particle diameter of 12 nm (Aerosil RY20 manufactured by Nippon Aerosil Co., Ltd.)
A thermosetting resin composition 3 of the present invention was produced in the same manner as in Example 2, except that 0.94 g was added as the filler D without hydrophobizing 0). The viscosity of the obtained thermosetting resin composition was 185 Pa · s, and the thixo ratio was 6.6.
The dispensing speed is 0.07 sec / point and the coating diameter is 0.6
It was applied in a dot shape of mm, and each defect occurrence rate was measured in the same manner as in Example 1. Table 1 shows the results. << Comparative Example >> As filler, shape: fibrous, size: about 5
μm asbestos (Cadori asbestos RG244 manufactured by Tomoe Kogyo Co., Ltd.) and aliphatic amide-based thixotropic agent (Dispalon A603-20X manufactured by Kusumoto Kasei Co., Ltd.)
A thermosetting resin composition for comparison was produced in the same manner as in Example, except for using. The viscosity of the obtained comparative thermosetting resin composition was 140 Pa · s, and the thixo ratio was 4.5. This was applied in the form of a dot having an application diameter of 0.6 mm, and each defect occurrence rate was measured in the same manner as in Example 1. Table 1 shows the results.

[0023]

[Table 1]

As shown in Table 1, each of the thermosetting resin compositions produced in Examples 1 to 3 had a low failure rate. In addition, it was found that it had a performance comparable to that using harmful asbestos used conventionally.

As described above, according to the present invention, a thermosetting resin composition for an adhesive which is suitable for application with a dispenser without using harmful asbestos and provides an electronic circuit board of excellent quality is provided. Obtainable.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an example of a process of applying an adhesive on a circuit board using a dispenser.

FIG. 2 is a view showing a state in which an adhesive is stretched in a thread shape in the step shown in FIG.

FIG. 3 is a diagram showing a state of stringing and scattering of an adhesive in a step shown in FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Adhesive 2 Nozzle 3 Syringe 4 Float 5 Air pressure 6 Circuit board

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Takashi Akiguchi 1006 Kazuma Kadoma, Kazuma, Osaka Matsushita Electric Industrial Co., Ltd.F-term (reference) EL136 EN006 FB087 FB097 FB287 FD013 FD017 FD142 FD146 GQ05 5E319 AA03 AC01 CD15 CD27

Claims (10)

[Claims] 1. A thermosetting resin composition comprising a thermosetting resin, a curing agent and a filler, wherein at least a part of the filler is a hydrophobic inorganic powder whose surface is subjected to a hydrophobic treatment. object. 2. The thermosetting resin composition according to claim 1, wherein at least a part of the surface of the hydrophobic inorganic powder is subjected to particle surface treatment to enhance cohesion. 3. The thermosetting resin composition according to claim 1, wherein the hydrophobic inorganic powder is a spherical inorganic powder. 4. The particle size of the hydrophobic inorganic powder is from 10 to 20.
The thermosetting resin composition according to any one of claims 1 to 3, which has a nm. 5. The thermosetting resin composition according to claim 1, wherein the content of the hydrophobic inorganic powder is 2.0 to 2.4% by weight. 6. The thermosetting resin composition according to claim 1, wherein the thermosetting resin is an epoxy resin. 7. The thermosetting resin composition according to claim 6, wherein the epoxy resin contains at least one low-viscosity crystalline epoxy resin. 8. The thermosetting resin composition according to claim 1, wherein the filler other than the hydrophobic inorganic powder has a particle size of 10 to 20 μm. 9. A step of applying an adhesive comprising the thermosetting resin composition according to claim 1 onto a circuit board using a dispenser, and mounting an electronic component on the applied adhesive. A method for mounting an electronic component, comprising: a step of curing the applied adhesive by heating to fix the component on a substrate. 10. The electronic component mounting method according to claim 9, wherein in the applying step, the application speed of the dispenser is controlled in accordance with the viscosity of the adhesive.