Adhesives for electronic materials

Abstract

The objective is to provide an adhesive for electronic materials that can be visually inspected using a solder printing inspection machine. [Solution] The adhesive for electronic materials according to the first invention is an adhesive for electronic materials comprising an epoxy resin, a curing agent, and a filler, wherein the filler comprises at least one inorganic solid material selected from titanium dioxide, zinc oxide, and zirconium oxide, the dispersion degree of the adhesive for electronic materials is 50 μm or less, and the curing agent is a modified aliphatic polyamine. The adhesive for electronic materials according to the second invention is an adhesive for electronic materials comprising an epoxy resin, a curing agent, and a filler, wherein the filler comprises at least one inorganic solid material selected from titanium dioxide, zinc oxide, and zirconium oxide, the dispersion degree of the adhesive for electronic materials is 50 μm or less, and the content of the inorganic solid material is 5.0% by mass or more and 65.0% by mass or less of the total amount of the adhesive for electronic materials.

Description

Technical Field

[0001] The present invention relates to an adhesive for electronic materials.

Background Art

[0002] Conventionally, when mounting an electronic component on a substrate, for example, an adhesive for electronic materials is used for the purpose of temporarily fixing the electronic component during flow soldering, preventing the dropping, displacement, floating, etc. of the lower surface component during double-sided reflow, and the like. As such an adhesive for electronic materials, for example, Patent Document 1 discloses an adhesive containing an epoxy resin, a curing agent, a curing accelerator, and a filler.

[0003] The adhesive for electronic materials is applied, for example, to a location where an electronic component is to be mounted using a dispenser or the like after printing solder paste on a substrate. Then, by further mounting the electronic component and performing reflow, the adhesive for electronic materials is cured, and as a result, the electronic component is fixed to the substrate.

[0004] By the way, the solder paste printed on the substrate is visually inspected using a solder printing inspection machine to confirm whether there is a problem with the printing state. Although various methods are known as the visual inspection method (see, for example, Non-Patent Document 1), in recent years, a phase shift method that projects a plurality of stripes with different phases and measures the three-dimensional shape from the change in the stripe shape has been widely used.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Non-Patent Documents

[0006]

Non-Patent Document 1

[0007] Traditionally, the adhesive used for electronic materials applied to a circuit board has been visually inspected to ensure that the required amount is applied to the desired location and that there are no abnormalities in the application shape (for example, the formation of protrusions on the surface). This is because insufficient application of the adhesive may cause components to detach, while excessive application or abnormal application shape may cause the adhesive to adhere to unintended areas. In either case, these can lead to defects such as unsoldered areas during soldering.

[0008] However, in recent years, with the miniaturization and increased performance of electronic devices, the electronic components used have also become smaller, resulting in an enormous number of adhesive application points per circuit board. This makes visual inspection difficult and also consumes a lot of time. While it is possible to use inspection machines, electronic adhesives cannot be visually inspected with solder printing inspection machines, requiring the use of separate inspection machines, which is time-consuming. Therefore, there is a demand to be able to visually inspect electronic adhesives applied to circuit boards using solder printing inspection machines.

[0009] This invention has been made in view of the above circumstances, and aims to provide an adhesive for electronic materials that can be visually inspected using a solder printing inspection machine. [Means for solving the problem]

[0010] The adhesive for electronic materials according to the first invention of the present invention is an adhesive for electronic materials comprising an epoxy resin, a curing agent, and a filler, wherein the filler comprises at least one inorganic solid material selected from titanium dioxide, zinc oxide, and zirconium oxide, the dispersion degree of the adhesive for electronic materials is 50 μm or less, and the curing agent is a modified aliphatic polyamine.

[0011] The adhesive for electronic materials according to the second invention of the present invention is an adhesive for electronic materials comprising an epoxy resin, a curing agent, and a filler, wherein the filler comprises at least one inorganic solid material selected from titanium oxide, zinc oxide, and zirconium oxide, the dispersion degree of the adhesive for electronic materials is 50 μm or less, and the content of the inorganic solid material is 5.0% by mass or more and 65.0% by mass or less of the total amount of the adhesive for electronic materials. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide an adhesive for electronic materials that can be visually inspected using a solder printing inspection machine. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 shows three-dimensional images of the adhesives for electronic materials of Examples 1 to 9, created using a solder printing inspection machine. [Figure 2] Figure 2 shows three-dimensional images of the adhesives for electronic materials of Comparative Examples 1 to 5, created using a solder printing inspection machine. [Modes for carrying out the invention]

[0014] The following describes adhesives for electronic materials according to embodiments of the present invention.

[0015] <Adhesives for electronic materials> The adhesive for electronic materials according to this embodiment includes an epoxy resin, a curing agent, and a filler.

[0016] (Epoxy resin) The epoxy resin is not particularly limited. For example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, novolak type epoxy resin, alicyclic epoxy resin, glycidyl ester type epoxy resin, glycidyl amine type epoxy resin, alicyclic epoxy resin, etc. may be mentioned. The epoxy resin may be used alone or in combination of two or more.

[0017] From the viewpoint of enhancing the filling property and mechanical strength of the adhesive for electronic materials to the substrate, the content of the epoxy resin is preferably 30.0% by mass or more, more preferably 35.0% by mass or more, based on the total amount of the adhesive for electronic materials. Also, from the viewpoint of enhancing the filling property of the adhesive for electronic materials to the substrate, the content of the epoxy resin is preferably 80.0% by mass or less, more preferably 70.0% by mass or less, based on the total amount of the adhesive for electronic materials. When two or more epoxy resins are contained, the content is the total content of the epoxy resins.

[0018] (Curing agent) Examples of the curing agent include amine-based curing agents. Examples of the amine-based curing agents include aliphatic amines such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine, dipropylenediamine, m-xylenediamine, isophoronediamine, aromatic amines such as metaphenylenediamine, diaminodiphenylmethane, diaminodiphenylsulfone, and modified products thereof. Among these, from the viewpoint of making the curing temperature correspond to the temperature profile during reflow, the amine-based curing agent is preferably a modified aliphatic polyamine which is a modified product of an aliphatic amine. The curing agent may be used alone or in combination of two or more. In the adhesive for electronic materials according to the embodiment of the first invention, the curing agent is a modified aliphatic polyamine.

[0019] From the perspective of obtaining a cured product with a strength capable of suppressing component displacement and preventing component detachment, the content of the curing agent is preferably 4.0% by mass or more, more preferably 8.0% by mass or more, based on the entire adhesive for electronic materials. Also, from the perspective of suppressing an increase in the viscosity of the adhesive for electronic materials, the content of the curing agent is preferably 40.0% by mass or less, more preferably 30.0% by mass or less, based on the entire adhesive for electronic materials. When two or more kinds of curing agents are included, the content is the total content of the curing agents.

[0020] (Filler) The filler according to this embodiment contains at least one inorganic solid material selected from titanium oxide, zinc oxide, and zirconium oxide.

[0021] From the perspective of further enhancing the recognition of the adhesive for electronic materials in a solder printing inspection machine, the content of the inorganic solid material is preferably 0.5% by mass or more, more preferably 5.0% by mass or more, based on the entire adhesive for electronic materials. Also, from the perspective of enhancing the filling property of the adhesive for electronic materials onto the substrate, the content of the inorganic solid material is preferably 65.0% by mass or less, more preferably 50.0% by mass or less, based on the entire adhesive for electronic materials. When two or more kinds of inorganic solid materials are included, the content is the total content of the inorganic solid materials. In the adhesive for electronic materials according to the embodiment of the second invention, the content of the inorganic solid material is 5.0% by mass or more and 65.0% by mass or less based on the entire adhesive for electronic materials.

[0022] From the perspective of enhancing the filling property of the adhesive for electronic materials onto the substrate, the filler according to this embodiment may contain other fillers other than the inorganic solid material. Examples of other fillers include inorganic fillers such as silica, talc, mica, zirconium phosphate, boron nitride, aluminum nitride, silicon nitride, and aluminum oxide, and organic fillers such as cellulose fiber. Note that other fillers may be used alone or in combination of two or more kinds.

[0023] From the viewpoint of maintaining the viscosity of the adhesive for electronic materials and increasing its mechanical strength, the content of other fillers is preferably 0.1% by mass or more, and more preferably 5.0% by mass or more, relative to the total amount of the adhesive for electronic materials. Furthermore, from the viewpoint of suppressing an increase in the viscosity of the adhesive for electronic materials and improving its ability to fill the substrate, the content of other fillers is preferably 60.0% by mass or less, and more preferably 30.0% by mass or less, relative to the total amount of the adhesive for electronic materials. Note that if two or more types of other fillers are included, the above content refers to the total content of the other fillers.

[0024] The degree of dispersion of the adhesive for electronic materials according to this embodiment is 50 μm or less, and preferably 30 μm or less, from the viewpoint of further improving the recognition of the adhesive for electronic materials in a solder printing inspection machine. The degree of dispersion can be measured according to JIS K 5600-2-5. Furthermore, the degree of dispersion can be adjusted to 50 μm or less by mixing each component contained in the adhesive for electronic materials and then dispersing the filler contained in the mixture using a three-roll mill. Specifically, the degree of dispersion can be adjusted to 50 μm or less by controlling the gap between the rolls of the three-roll mill to 50 μm or less. For example, a feeler gauge (leaf with a thickness of 0.05 mm or less) can be used to control the gap.

[0025] The viscosity of the adhesive for electronic materials according to this embodiment is preferably 20 Pa·s to 150 Pa·s, and more preferably 30 Pa·s to 90 Pa·s, from the viewpoint of improving the filling ability of the adhesive for electronic materials into the substrate. The viscosity can be measured according to JIS K 7117-2. Furthermore, the viscosity can be adjusted to 20 Pa·s or higher by increasing the amount of filler added. Conversely, it can be adjusted to 150 Pa·s or lower by decreasing the amount of filler added.

[0026] The method for producing an adhesive for electronic materials according to this embodiment includes a kneading step of obtaining a mixture containing an epoxy resin, a curing agent, and a filler under reduced pressure, and a dispersion step of dispersing the filler contained in the mixture.

[0027] In the mixing process, epoxy resin, curing agent, filler, and other components as needed are mixed under reduced pressure to obtain a compound. The mixing method is not particularly limited, and mixing can be done using conventionally known mixing machines and conventionally known methods.

[0028] In the dispersion process, the fillers contained in the mixture obtained in the mixing process can be dispersed using a three-roll mill. Specifically, by controlling the gap between the rolls of the three-roll mill, the aggregated filler particles can be dispersed. This allows the fillers to spread uniformly to even the finest details of the resin, enabling recognition of even the finest areas of the printed portion of the adhesive for electronic materials, thereby improving the recognition of the adhesive for electronic materials in solder printing inspection machines. For example, a feeler gauge can be used to control the gap.

[0029] The adhesive for electronic materials manufactured in this manner can be applied to a predetermined location on a substrate (for example, the location where electronic components are placed) using conventionally known equipment such as a dispenser.

[0030] The adhesive for electronic materials according to this embodiment is fluid at room temperature (25°C to 30°C) and can be cured by heating to 60°C to 260°C. Due to these characteristics, it can be suitably used, for example, as an adhesive for fixing electronic components to a substrate in the process of mounting electronic components onto a substrate.

[0031] The adhesive for electronic materials according to this embodiment is an adhesive for electronic materials comprising an epoxy resin, a curing agent, and a filler, wherein the filler includes at least one inorganic solid material selected from titanium oxide, zinc oxide, and zirconium oxide, and the dispersion degree of the adhesive for electronic materials is 50 μm or less, thereby enabling visual inspection with a solder printing inspection machine. Specifically, the solder printing inspection machine recognizes the three-dimensional shape of the object to be inspected by shining light on the object and capturing the reflected light. By including at least one inorganic solid material selected from titanium oxide, zinc oxide, and zirconium oxide as the filler, and by having a dispersion degree of 50 μm or less of the adhesive for electronic materials, it is possible to improve the recognition of the adhesive for electronic materials in the solder printing inspection machine, and to acquire the image necessary for visual inspection. This enables visual inspection with a solder printing inspection machine. Furthermore, by having a dispersion degree of 50 μm or less of the adhesive for electronic materials, the fillability of the adhesive in the substrate and the mechanical strength can be improved.

[0032] In the adhesive for electronic materials according to the first embodiment of the invention, the curing agent is a modified aliphatic polyamine, which allows the curing temperature to correspond to the temperature profile during reflow.

[0033] In the adhesive for electronic materials according to the second embodiment of the invention, the content of the inorganic solid material is 5.0% by mass or more and 65.0% by mass or less relative to the total amount of the adhesive for electronic materials, thereby further improving the visibility of the adhesive for electronic materials in a solder printing machine.

[0034] <Visual Inspection Method for Adhesives for Electronic Materials> The method for inspecting the appearance of an adhesive for electronic materials according to this embodiment is a method for inspecting the appearance of an adhesive for electronic materials applied to a substrate, and involves using a solder printing inspection machine to image the applied adhesive for electronic materials and acquire an image.

[0035] The solder printing inspection machine is not particularly limited, and conventionally known solder printing inspection machines can be used. For example, a solder printing inspection machine can be used that includes an illumination device as an illumination means for irradiating the surface of the substrate with light from above, a high-resolution camera as an imaging means for imaging the substrate irradiated with light, and a control device for performing image processing, calculation processing, etc. The high-resolution camera is not particularly limited, and for example, a CCD camera can be used.

[0036] Examples of inspection methods for solder printing inspection machines include the light section method, phase shift method, spatial coding method, and gracile projection method. Among these, the phase shift method is preferred for solder printing inspection machines. The phase shift method involves irradiating the surface of the substrate with light (fringes with different phases) multiple times and measuring the three-dimensional shape from the change in the fringe shape.

[0037] In the visual inspection method for electronic material adhesives according to this embodiment, an image is acquired by imaging the applied electronic material adhesive using such a solder printing inspection machine.

[0038] Specifically, first, the illumination device of the solder printing inspection machine irradiates the surface of the substrate coated with electronic adhesive with predetermined light (stripes with different phases) from above. Subsequently, a high-resolution camera captures an image of the illuminated substrate to obtain an image of the electronic adhesive.

[0039] Next, the control unit of the solder printing inspection machine measures the three-dimensional shape of the adhesive for electronic materials based on images obtained from a high-resolution camera. Then, the measurement results are compared with inspection information (for example, the height and volume of the adhesive for electronic materials in an ideal application state) stored in the solder printing inspection machine to determine whether the adhesive for electronic materials is good or bad. A specific method for determining whether the adhesive is good or bad is, for example, whether the measured height of the adhesive for electronic materials matches the height recorded in the inspection information.

[0040] The method for inspecting the appearance of an adhesive for electronic materials according to this embodiment is a method for inspecting the appearance of an adhesive for electronic materials applied to a substrate, and involves using a solder printing inspection machine to image the applied adhesive for electronic materials and acquire an image. This makes it possible to perform the appearance inspection of the adhesive for electronic materials using the same equipment as the appearance inspection of solder paste, thus making it efficient.

[0041] In this embodiment, the visual inspection method for adhesives for electronic materials is such that the inspection method of the solder printing inspection machine is a phase shift method, allowing the visual inspection of adhesives for electronic materials to be performed using a general-purpose solder printing inspection machine. [Examples]

[0042] The following describes embodiments of the present invention, but the present invention is not limited to the following embodiments.

[0043] <Fabrication of adhesives for electronic materials> (Examples 1-9 and Comparative Examples 1-4) The epoxy resin, hardener, and filler in the amounts shown in Tables 1 and 2 were placed in a kneader (universal mixing and stirring machine 8NDMV-Qr, manufactured by Dalton Co., Ltd.) and kneaded under reduced pressure of -0.1 MPa to -0.05 MPa. Next, the gap between the rolls of a three-roll mill (DR-35, manufactured by Kaneda Rika Kogyo Co., Ltd.) was adjusted using a feeler gauge (JIS standard feeler gauge, manufactured by Nagai Gauge Seisakusho Co., Ltd.). The kneaded mixture was then placed in the three-roll mill to disperse the filler, and adhesives for electronic materials of Examples 1 to 9 and Comparative Examples 1 to 4 were obtained. Details of each raw material shown in Tables 1 and 2 are shown in Table 3.

[0044] (Comparative Example 5) The epoxy resin, curing agent, and filler in the proportions shown in Table 2 were placed in a kneader (universal mixing and stirring machine 8NDMV-Qr, manufactured by Dalton) and kneaded under reduced pressure of -0.1 MPa to -0.05 MPa to obtain the adhesive for electronic materials of Comparative Example 5.

[0045] [Table 1]

[0046] [Table 2]

[0047] [Table 3]

[0048] [Measurement of variance] The dispersion degree (μm) of the adhesives for electronic materials in each example and comparative example was measured in accordance with JIS K 5600-2-5 using a grind gauge (Sheen) for 0-100 μm and a scraper (Sheen). The measurement results are shown in Tables 1 and 2.

[0049] [Viscosity measurement] The viscosity (Pa·s) of the adhesives for electronic materials in each example and comparative example was measured using an E-type viscometer RE-100U (manufactured by Toki Sangyo Co., Ltd.) in accordance with JIS K 7117-2. The measurement results are shown in Tables 1 and 2.

[0050] [Measuring adhesive strength] Adhesion strength (kgf / mm²) of adhesives for electronic materials in each example and comparative example 2 The bond tester 4000Plus (manufactured by Nordson DAGE) was used to measure the bond in accordance with JIS Z 3198-7. The measurement results are shown in Tables 1 and 2.

[0051] [Evaluation of perceptibility] <Fabrication of test boards> 200g of each example and comparative example of the adhesive for electronic materials was placed on a metal mask set up in a printing press (YSP, manufactured by Yamaha Motor Co., Ltd.), and printing was performed under the following printing conditions in an environment of 24-26°C and 50-60%RH. (Printing conditions) Printing squeegee: Metal squeegee Metal mask thickness: 150 μm Circuit board used: Plain resist board Printing area size and shape: 0.9mm x 1.1mm, square shape Number of print locations: 60

[0052] <Evaluation of Recognition> The adhesives for electronic materials of each example and comparative example printed on the substrate were detected using a solder printing inspection machine (KOHYOUNG aSPIer, manufactured by KOH YOUNG TECHNOLOGY). A photograph of the adhesive printed on one printing location located in the center of 60 printing locations and a 3D image created by the solder printing inspection machine were obtained. The acquired 3D images are shown in Figures 1 and 2. Recognition was evaluated by comparing the shape of the photograph with the shape of the 3D image, and the number of protrusions that appeared on the surface of the adhesive in the 3D image was used to evaluate it. Specifically, if there were 0 protrusions, it was evaluated as "1 (Excellent)", and if there were 1 to 3 protrusions, it was evaluated as "2 (Good)". Furthermore, if there were 4 or more protrusions, if the shape of the adhesive could not be recognized as in Comparative Example 2, or if the shape of the photograph and the shape of the 3D image differed significantly as in Comparative Example 5, it was evaluated as "3 (Poor)". The evaluation results are shown in Tables 1 and 2.

[0053] As can be seen from the results in Tables 1 and 2, the adhesives for electronic materials of each embodiment that satisfy all the requirements of the present invention exhibit excellent recognition on solder printing inspection machines and can acquire images necessary for visual inspection. Therefore, visual inspection can be performed using a solder printing inspection machine.

Claims

1. An adhesive for electronic materials comprising epoxy resin, a hardening agent, and a filler, The filler comprises at least one inorganic solid material selected from titanium oxide, zinc oxide, and zirconium oxide. The degree of dispersion of the aforementioned adhesive for electronic materials is 50 μm or less. The curing agent is a modified aliphatic polyamine. Adhesives for electronic materials.

2. An adhesive for electronic materials comprising epoxy resin, a hardening agent, and a filler, The filler comprises at least one inorganic solid material selected from titanium oxide, zinc oxide, and zirconium oxide. The degree of dispersion of the aforementioned adhesive for electronic materials is 50 μm or less. The content of the inorganic solid material is 5.0% by mass or more and 65.0% by mass or less relative to the total amount of the adhesive for electronic materials. Adhesives for electronic materials.

Images