JP2003283092A - Circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a board structure which can increase fixing strength of a mounting component on a mica substrate and improve connection reliability in an electrical connection part, and enables manufacture of a circuit board which is thin as compared with the conventional one. <P>SOLUTION: In a substrate surface part which faces a bottom surface of the mounting component and a component terminal part, one or more penetrating holes or bored holes are formed. An adhesive agent or a conducting material having adhesive function is poured into the penetrating holes or a bored hole part, and the periphery is covered and coated with the adhesive material, thereby bonding the mounting component to the substrate. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly contributes to an improvement in fixing strength of mounting components to a substrate and reliability of electrical connection in an electronic circuit substrate using mica as a base material regardless of single layer or multilayer. The present invention relates to a board structure, and particularly to an electronic circuit board that needs to be thin.

[0002]

2. Description of the Related Art A circuit board using mica as a base material has a wiring pattern formed on the surface of the mica board by an etching method or a screen printing method, and a hole is formed in the same manner as a general printed wiring board to form a through hole, By connecting layers using via holes or the like, a multilayer wiring board having excellent high frequency characteristics can be manufactured, and various parts can be mounted on both sides of the board. (See JP-A-62-145799.)

However, for example, as shown in FIG.
The mounted component 1 fixed on the mica substrate 3 regardless of the multi-layered substrate has a drawback that even if the component is adhered to the substrate with an adhesive or the like, the substrate fixing strength after the adhesion is small and the component easily comes off. It was Originally, the mica plate has a molecular structure having a planar structure arranged in the plate thickness direction, and the bond between the molecular layers is extremely small, so that the mica plate is easily cleaved between the molecular layers. Since the bonding force between the molecular layers is extremely small as compared with the adhesive force between the adhesive and the surface of the mica, the mounted component adhered to the surface of the mica easily falls off together with the molecular layer of the mica.

Similarly, when the soldering terminal 6 is formed on the surface of the mica substrate 3 as shown in FIG. 2 and the surface mounting component 4 is mounted by soldering or a conductive adhesive, the soldering terminal 6 on the substrate is Since the fixing strength is small and the soldering terminals on the board are easily separated from the board due to external stress, there is a problem in reliability after component mounting. Therefore, as shown in FIG. 3, in order to increase the adhesion area to the mica substrate, an adhesive was poured into the gap between the bottom surface of the surface mount component 4 and the substrate and fixed together with the substrate, but with the mica surface in contact with the adhesive layer 2. Peeling did not occur, and the bond strength was not significantly improved. In order to solve these problems and improve the reliability, as shown in FIG. 4, the lead terminal 9 is attached to the mica substrate 3 on which the mounting component 1 is mounted, set in the outer case 7, and the casting resin 8 is added. It is necessary to devise a structure that does not give stress to the mica substrate itself on which the components are mounted by fixing with, and there is a problem that the production cost is increased and it is difficult to produce a thin mica substrate.

[0005]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, mainly by increasing the fixing strength of the mounted components on the mica substrate and improving the connection reliability in the electrical connection portion. It is an object of the present invention to provide a substrate structure that enables the production of a thinner circuit board than ever before.

[0006]

According to the present invention, in order to solve the above-mentioned problems, a single or a plurality of through holes or perforations are provided in a board surface portion where a bottom surface of a mounted component and a component terminal portion face each other. An adhesive is poured into the holes or perforations, and the periphery of the holes or perforations is coated with an adhesive to adhere the mounted components to the substrate.

When a through hole is used, the adhesive is poured into the through hole so that the adhesive partially sticks out on the back side of the substrate and is cured, so that the cured adhesive holds the mica substrate through the through hole. It functions as a material, and since it is integrated with the adhesive layer that bonds the board surface and the bottom surface of the mounted component, it is possible to suppress the molecular delamination of the mica substrate itself and improve the component adhesion strength to the substrate. .

Further, the position of arranging the through hole or the perforated portion is not limited to the area of the substrate surface where the bottom surface of the mounted component faces, but an adhesive is formed near the outer peripheral portion of the mounted component and the entire mounted component and the through holes and perforated holes The strength of fixing the mounted component to the substrate can also be improved by covering the part so as to be poured.

On the other hand, even when the perforations are used instead of the through holes, by pouring the adhesive into the perforations, the mounted components are not simply adhered to the substrate surface, but the adhesive inside the perforations has a pile shape. As a structural material, the mounted component is fixed on the substrate, and the fixing strength of the mounted component to the substrate is improved.

The above is the means mainly for improving the fixing strength of the parts on the board. However, in the terminal part on the board for the purpose of electrical connection, a through hole or a perforated part is provided in the terminal part to bond the parts. By replacing the agent with a material that also has conductivity and pouring it into the through-holes and perforations as described above, and bonding and hardening the mounted components, the effect of improving the fixing strength of the terminals can be obtained, and the reliability of electrical connection It can be improved.

Both methods are particularly effective when the mica material is exposed on the front and back surfaces of the substrate, but a material such as a prepreg material or a thermoplastic resin sheet that can be bonded to mica through an adhesive layer is used. Even in the case of a combined multi-layer substrate, and even when the mica material is not necessarily exposed on the front and back surfaces, the effect of similarly improving the bonding strength can be exhibited.

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments in which the circuit board according to the present invention is applied to a mica substrate will be described below with reference to FIGS. 5, 6, 7, and 8.
Will be described with reference to.

[0012]

[Embodiment 1] FIG. 5 shows a first embodiment in which a mounting component having a ceramic exterior is bonded onto a single-layer mica substrate. First, in the bottom area of the 5 mm × 5 mm mounted component 1 of the mica substrate 3 having a thickness of 50 μm, the through hole 10 of φ0.4 mm is formed.
5 are opened by drilling. In this case, a drilling machine is used, but a punching method can also be used. Next, an epoxy resin is applied as an adhesive so as to cover the through hole area, and 5 m on top of this.
After mounting the mounting component 1 of m × 5 mm, it was cured by heating at 180 ° C. for 30 minutes and adhered on the mica substrate. The adhesive to be used is not limited to the epoxy resin, and various organic and inorganic adhesives can be selected and used.

Here, in the case where the through holes are not formed and an adhesive is applied and bonded (level 1 in the embodiment of FIG. 1).
With respect to the mica substrate when two through-holes according to the present invention are formed (level 2) and when five through-holes according to the present invention are formed (level 3 in the embodiment of FIG. 5). The results shown in Table 1 were obtained by comparing the component fixing strengths. or,
Graph 1 is a graph of the result.

[Table 1]

[Graph 1]

The adhesive strength is measured by fixing a wire on the surface of the component after the adhesive is cured, and pulling this wire in the vertical direction of the substrate at a constant speed of approximately 1 mm / sec using a push-pull gauge to remove the mounted component from the substrate. The strength when peeled off was measured.

From Table 1 and Graph 1, two through holes (level 2) and five (level 3) through holes according to the method of the present invention are punched with respect to the fixing strength in the conventional method (level 1) in which no through holes are drilled. In the case of the one provided, it is apparent that the bond strength is improved. In level 3, the strength is improved to about 8 times that in level 1 which is the conventional construction method, which clearly shows the effect of the through hole structure according to the present invention.

[0016]

Example 2 Next, FIG. 6 shows Example 2 in which through holes were formed in advance on a mica substrate, soldering terminals were formed by a screen printing method so as to cover the through holes, and then surface mount components were mounted. Show. Example 2 is an example in which the substrate structure of the present invention is applied to a terminal portion on a substrate for electrical connection. On the mica substrate 3 having a thickness of 50 μm, two through holes 10 each having a diameter of 0.3 mm are formed at positions corresponding to the two left and right terminals of the surface mount component 4, and the through holes 10 are passed through the screen printing method using conductive silver paste. Through holes were formed, and soldering terminals 6 were formed on the front and back.

Thereafter, the conductive silver paste is applied to a peak temperature of 56.
After baking at 0 ° C for 3 minutes to make a conductor, the substrate is dipped in a solder bath to solder 5 on the terminals and in the through holes.
Was attached. After that, solder paste was applied onto the connection terminals, mounted components were mounted, and reflow soldering was performed to obtain electrical connections.

As described above, the mounting component can be fixed on the mica substrate with the same structure as that of the first embodiment, and the electrical connection can be obtained at the same time. In addition, the first embodiment is further prepared in advance on the surface of the substrate facing the bottom portion of the mounted component excluding the terminal portion.
It is also possible to provide a further fixing strength by forming a through hole as described above and pouring an adhesive into the gap between the mounting component and the substrate after the reflow to cure the adhesive. Although the solder paste is used in the second embodiment, any conductive material that is hardened after connection can be used regardless of the form of the adhesive such as liquid, paste or sheet.

[0019]

Third Embodiment Next, FIG. 7 shows a third embodiment in which a semiconductor element is flip-chip mounted on a mica substrate. In FIG. 7, the connection terminals of the semiconductor element 13 and the corresponding connection terminals / wirings on the mica substrate 3 are omitted. After the circuit wiring is formed on the mica substrate 3 by the screen printing method, the semiconductor element 13 and the terminals on the mica substrate 3 are connected using the conductive resin 11 such as a conductive adhesive or an anisotropic conductive material. On the mica substrate 3, approximately 1 from the outer peripheral portion of the semiconductor element 13 is previously prepared.
A plurality of through holes 10 are formed at positions separated by mm, and after mounting the semiconductor element 13, the surface of the semiconductor element 13 and the through hole 10 are formed.
The exterior resin 12 was applied so as to cover the above and fixed on the mica substrate 3. The position of the through hole 10 is approximately 1 / l of the vertical and horizontal dimensions from the end surface with respect to the occupied position of the mounted component.
Within 2 is effective, and preferably within about 1/4 in the vertical and horizontal dimensions from the end face of the mounting component.

As a result, the exterior resin 1 on the surface of the semiconductor element
Since 2 has the structure of Example 1 in the portion outside the outer periphery of the component, the exterior resin 12 is firmly fixed to the mica substrate 3. Further, since the semiconductor element 13 has a structure in which it is wrapped with the mica substrate 3 and the exterior resin 12, the electrical reliability between the semiconductor element and the mica substrate is improved against external stress. Also in this third embodiment, it is possible to further improve the fixing strength by applying the first and second embodiments to the bottom of the semiconductor element and the terminal surface on the substrate.

[0021]

[Embodiment 4] FIG. 8 shows an embodiment in which a semiconductor element is fixed on a mica multilayer substrate. The multi-layered substrate has three layers of electric circuit patterns 18 formed on both sides of the mica substrate 3 by a screen printing method, and a glass adhesive layer 17 using a low melting point glass having a melting point of about 540 ° C. as an interlayer adhesive material. The mica substrate 3 is integrated, and the interlayer wiring between the mica substrates is connected by through holes,
The total substrate thickness is about 250 μm.

First, five perforated portions 16 having a depth of 0.1 mm and a diameter of 0.4 mm are formed in the semiconductor fixing portion on the multilayer substrate. After the adhesive is applied to the surface of the substrate so that the adhesive may flow into the formed perforations, the semiconductor element 13 is placed on the substrate 180
It was fixed on the substrate by heating and curing at 30 ° C. for 30 minutes.

As a result, the adhesive flows into the perforated portion,
The hardened pile-shaped adhesive portion exerts an anchor effect in the vertical direction of the substrate, and the adhesive layer formed on the bottom surface of the semiconductor is integrally hardened with the pile-shaped adhesive portion, so that the semiconductor and the substrate are fixed. Strength has improved significantly. Further, by using the third embodiment together, the adhesion strength to the substrate can be further improved.

Although the through holes and perforations of Examples 1 to 4 are formed in a cylindrical shape on the mica substrate as described above, the same effect can be obtained even in a shape other than the cylindrical shape, and the positions and holes to be formed are different. The number can also be determined as appropriate.

[0025]

As described above, according to the present invention, in a single-layer / multi-layer board using mica as a base material, it penetrates on the surface of the board facing the bottom surface of the mounting component, the connection terminal portion, and the outside of the mounting component. After forming holes or perforations and applying adhesive or conductive material to cover those parts, fix the mounting parts to improve the strength of attachment of the mounting parts to the board and also improve the reliability of electrical connection. I was able to do it. Further, since it is not necessary to form a protective structure for the mounted components together with the substrate by resin molding or the like, it is possible to reduce the cost and manufacture a thin and highly reliable circuit board.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a conventional component bonding structure on a mica substrate.

FIG. 2 is a mounting cross-sectional view of a mounting component in a conventional mica-board soldering terminal.

FIG. 3 is a mounting cross-sectional view of a mounting component in a conventional mica-board soldering terminal.

FIG. 4 is a cross-sectional view of a conventional mica substrate with an outer case.

FIG. 5 is a substrate top view and a sectional view showing the component bonding structure on the mica substrate of the present invention in Embodiment 1.

FIG. 6 is a board top view and a sectional view showing a component soldering structure on a mica board of the present invention in Embodiment 2;

FIG. 7 is a substrate top view and a cross-sectional view showing a component bonding structure on a mica substrate of the present invention in Example 3.

FIG. 8 is a substrate top view and a cross-sectional view showing a component bonding structure on a multilayer mica substrate of the present invention in Example 4;

[Explanation of symbols]

1 ... Mounted parts 2 ... Adhesive layer 3 ... Mica substrate 4 ... Surface mount components 5 ... Solder 6 ... Soldering terminals 7 ... Exterior case 8 ・ ・ Casting resin 9 ... Lead terminals 10 ... through hole 11 ... Conductive resin 12 ... Exterior resin 13 ... Semiconductor element 14 ... Bonding wire 15-through hole 16 ... Perforated part (pile-shaped adhesive part) 17 ... Glass adhesive layer 18 ... Electric circuit pattern

Claims (2)

[Claims] 1. A single-layer / multi-layer circuit board using at least one layer of mica as a base material, at least a through hole in a board surface facing a bottom surface area of a mounting component or a board surface in a region near the outside of the mounting component, Alternatively, the circuit board has a perforated portion, and the mounted component is fixed by being integrated with these through holes or perforated portions through an adhesive material. 2. A single-layer / multi-layer circuit board using at least one layer of mica as a base material, wherein a terminal portion on the board for electrical connection with a mounting component has a through hole or a perforated portion, A circuit board having a structure in which a conductive material is filled in the through hole or the inside of a perforated portion to electrically connect mounted components and fix the mounted components on the board at the same time.