JP2000022314A - Method of mounting electronic components - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of mounting electronic components whereby the cobwebbing of an adhesive can be prevented and troubles due to the cobwebbing can be effectively avoided in mounting the electronic components on a circuit board. SOLUTION: In a step of coating a conductive adhesive 14 on conductor lands 12 of a circuit board 11, the conductive adhesive 14 is coated, without causing the cobwebbing, using a mask 15 having a fluoro-resin 19 covering the inside faces of openings 17 to a plane facing the circuit board 11. In mounting, an IC chip 13 is adhered onto the conductive adhesive 14, without reducing the adhesion area, thereby avoiding lowering the mechanical connection strength between the IC chip 13 and circuit board 11 to avoid lowering the product quality.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of mounting an electronic component on a predetermined mounting area on a circuit board with an adhesive applied by mask printing.

[0002]

In recent years, an adhesive has been applied to a mounting area on a circuit board by mask printing, and an electronic component has been mounted on the mounting area on which the adhesive has been applied. A mounting method for mounting components has been considered. By the way, in this case, when a metal mask is used as a mask in mask printing, the following problem may occur.

[0003] That is, as shown in FIG.
The metal mask 2 is arranged at a predetermined position on the upper side, and the adhesive is printed from the opening 3 formed in the metal mask 2 so that the adhesive 4 is formed on the circuit board 1 (shown by hatching in FIG. 6). Is applied (see (a) in FIG. 6), and then the metal mask 2 is moved upward from the predetermined position (see (b) in FIG. 6). Due to the good surface wettability between the epoxy resin and the stainless steel that is the material of the metal mask 2 and the large self-cohesiveness of the adhesive 4, stringing occurs and the thickness of the adhesive 4 is reduced. There is a risk that the variation will occur.

When the adhesive 4 hardens in a state where such a stringing phenomenon has occurred (see (c) in FIG. 6), an electronic component (not shown) may be attached to the adhesive in some cases. 4 cannot be mounted on it, or if the
Even if it can be mounted on the electronic component, the bonding area is reduced, so that the mechanical connection strength between the electronic component and the circuit board 1 is reduced, and the quality of the product may be reduced.

Further, as shown in FIG. 7, when a conductive adhesive is used as an adhesive and a conductive adhesive 6 is applied on a conductive land 5 provided on the circuit board 1, as described above. If the stringing phenomenon occurs, the conductive adhesive 6 may be connected by the stringing phenomenon in some cases, and if so, the electronic component 7 and the circuit board 1 may be connected.
Not only does the mechanical connection strength between the conductor lands 5 decrease, but also a short circuit may occur between the conductor lands 5 and the like.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to prevent the occurrence of a stringing phenomenon of an adhesive when mounting an electronic component on a circuit board with the adhesive. It is another object of the present invention to provide a method of mounting an electronic component, which can effectively prevent the occurrence of a defect caused by the stringing phenomenon.

[0007]

According to the electronic component mounting method of the present invention, first, an application step of applying an adhesive to a mounting area is performed. At this time, the mask used in this coating step has at least a predetermined portion extending from the inner peripheral surface of the opening to the surface on the circuit board side covered with a resin having low surface wettability with an adhesive. After placing the mask at a predetermined position on the substrate, printing the adhesive from the opening and applying it to the mounting area, when the mask is moved upward from the predetermined position, the threading phenomenon does not occur, There is no variation in the thickness of the adhesive.

Next, after this coating step is performed,
A mounting process for mounting the electronic component in the mounting area is performed. At this time, by performing the above-described application step, the adhesive is applied without causing the stringing phenomenon, so that the bonding area does not decrease, and
A reduction in mechanical connection strength between the electronic component and the circuit board can be prevented, and a reduction in product quality can be prevented.

According to the electronic component mounting method of the present invention, since the resin is made of fluororesin, the fluororesin is a highly versatile resin, so that it can be easily obtained and handled. In providing the fluororesin at a predetermined site, a known method such as printing, impregnation, and spin coating can be applied.

According to the electronic component mounting method of the present invention, since the adhesive is made conductive, the electronic component and the circuit board are electrically connected in addition to the mechanical connection. In this case, since the stringing phenomenon does not occur as described above, it is possible to prevent a short circuit from occurring between conductor lands to which the conductive adhesive is applied.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. First, FIG.
1 schematically illustrates a mounting form of an electronic component obtained according to the present embodiment. In FIG. 2, a circuit board 11 is formed by printing and baking a Cu thick film paste material on a ceramic substrate, and a conductor land (mounting area in the present invention) 12 is provided at a predetermined portion thereof. I have. And I
The C chip (electronic component according to the present invention) 13 is adhered on the conductor land 12 via a conductive adhesive 14 (shown by hatching in FIG. 2). The conductive adhesive 14 is an amine-curable epoxy resin filled with an Ag filler, and has a viscosity of 150 Pa · S (poise seconds).

As shown in FIG. 3, such a mounting mode is performed by sequentially executing a coating step A1 and a mounting step A2. Hereinafter, specific contents of each of the steps A1 and A2 will be described with reference to FIG. This will be described with reference to FIG.

First, in a coating step A1, a mask 15 is arranged at a predetermined position on the circuit board 11, and a conductive adhesive is printed from an opening 17 to thereby form the circuit board 11.
A conductive adhesive 14 is applied on the conductive land 12 (see FIG. 1A). As printing conditions, the printing load was 1 N, and the moving speed of a squeegee (not shown) was 30 mm /
Seconds.

At this time, the mask 15 used in the coating step A1 is a metal mask 16 made of stainless steel and having a thickness of about 70 μm, as shown in FIG. A portion (a predetermined portion in the present invention) extending to a surface (lower surface in FIG. 4) 18 on the circuit board 11 side is covered with a fluororesin 19.

In this case, the mask 15 is obtained as follows. That is, the surface of the metal mask 16 opposite to the circuit board 11 (FIG. 5)
Medium, upper surface) 20, a tape 21 made of, for example, polyimide having high heat resistance is attached, and in that state, a liquid fluororesin is
The inner surface 17 of the opening 17 in the metal mask 16 is formed by a known method such as printing, impregnation, or spin coating.
Then, a coating is applied to a portion from a to the surface 18 on the circuit board 11 side. Next, the coated liquid fluororesin is cured by heating in an oven, and the tape 21 is peeled off while the fluororesin is being cured by heating. Thus, a mask 15 is obtained.

In this case, the thickness (film thickness) of the fluororesin 19 is about 10 μm, but is 0.5 μm to 10 μm.
If it is m, it is good. This is because if the thickness of the fluororesin 19 is smaller than 0.5 μm, a problem occurs in terms of durability. On the other hand, if the thickness of the fluororesin 19 is larger than 10 μm, the fluororesin 19 is not finely processed. This is because clogging occurs. Further, the thickness of the fluororesin 19 is desirably constant throughout, but is acceptable if the unevenness is less than ± 10 μm. This is because when the unevenness becomes ± 10 μm or more, this coating process A
This is because, in 1, the variation in the distance between the mask 15 and the circuit board 11 caused by the unevenness may have an adverse effect.

After applying the conductive adhesive 14 on the conductor lands 12, the mask 15 is moved upward from the predetermined position (see (b) in FIG. 1). At this time, since the surface wettability between the epoxy resin and the fluororesin 19, which are the main components of the conductive adhesive 14, is low, the threading phenomenon does not occur, and the upper surface of the conductive adhesive 14 The conductive adhesive 14 is substantially flat, and the thickness of the conductive adhesive 14 does not vary.

Next, in the mounting step A2, the IC chip 1
3 is mounted on the conductive land 12, that is, on the conductive adhesive 14 applied on the conductive land 12 (in FIG. 1,
(C)). In addition, as a mounting condition, a load is 6 N and a load application time is 1 second. At this time, the conductive adhesive 14
Since the upper surface is substantially flat, the bonding area does not decrease.

As described above, according to the present embodiment, the circuit board 1
In the application step A1 of applying the conductive adhesive 14 on the one conductive land 12, the portion from the inner peripheral surface 17a of the opening 17 to the surface 18 on the circuit board 11 side is made of a fluororesin 19
Using the mask 15 covered with the IC chip 1
3 is mounted on the conductive adhesive 14, the application step A1 includes the step of mounting the conductive adhesive 14 on the conductive adhesive 14.
Is applied without causing the stringing phenomenon. Accordingly, in the mounting step A2, the IC chip 13
Can be adhered onto the conductive adhesive 14 without reducing the adhesion area.
It is possible to prevent a decrease in mechanical connection strength between the circuit board 3 and the circuit board 11 and to prevent a decrease in product quality.

Particularly, in this case, since the conductive adhesive 14 is used as the adhesive, the IC chip 13 and the circuit board 11 are electrically connected in addition to the mechanical connection. In this case, a short circuit can be prevented from occurring between the conductor lands 12 and the like.

Further, since the fluororesin 19 is employed as a resin having low surface wettability with the conductive adhesive 14, it can be easily obtained and handled because the fluororesin is a highly versatile resin. In covering a predetermined portion of the metal mask 16 with the fluororesin 19, a known method such as printing, impregnation, and spin coating can be applied.

The present invention is not limited to the embodiment described above, but can be modified or expanded as follows. The adhesive is not limited to the conductive adhesive, but may be an insulating adhesive. That is, a configuration may be used in which the electronic component and the circuit board are mechanically connected only.

[Brief description of the drawings]

FIG. 1 is a sectional view (a) showing the operation of an embodiment of the present invention,
(B) and side view (c)

FIG. 2 is a side view schematically showing a mounting mode.

FIG. 3 is a flowchart showing a process flow.

FIG. 4 is a sectional view of a mask.

FIG. 5 is a cross-sectional view showing a state in which a tape is attached to a metal mask.

FIG. 6 is a diagram corresponding to FIG. 1 showing a conventional example.

FIG. 7 is a side view showing another conventional example.

[Explanation of symbols]

In the drawing, 11 is a circuit board, 12 is a conductor land (mounting area), 13 is an IC chip (electronic component), 14 is a conductive adhesive, 15 is a mask, 17 is an opening, 17a is an inner peripheral surface,
Reference numeral 18 denotes a surface, and 19 denotes a fluororesin.

Claims (3)

[Claims] An electronic component mounting method for mounting an electronic component on a predetermined mounting area on a circuit board with an adhesive applied by mask printing, wherein at least an inner peripheral surface of an opening portion faces the circuit board side. An application step of applying an adhesive to the mounting area using a mask in which the predetermined portion is covered with a resin having a low surface wettability with the adhesive; and a mounting step of mounting the electronic component on the mounting area. Are sequentially executed. 2. The method according to claim 1, wherein the resin is a fluororesin. 3. The electronic component mounting method according to claim 1, wherein the adhesive is conductive.