JP2001308501A - Method for mounting electronic parts - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method by which electronic parts can be mounted on the conductor electrode of a circuit board by using a conductive adhesive by performing electrical inspections before the adhesive is cured and, if necessary, the parts can be exchanged with another parts or remounted. SOLUTION: This method includes a step (S101) of applying a conductive adhesive to the conductor electrode, a step (S102) of mounting electronic parts on the conductor electrode by positioning the parts to the electrode, and a step (S103) of pressing the parts against the circuit board. The method also includes a step (S104) of inspecting continuity between the circuit board and electronic parts, and a step (S106) of completing the mounting of the parts by curing the conductive adhesive. When the result of the inspection is not good, the electronic parts are removed (S108) and the steps from (S101) to (S106) are repeated again.

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 circuit board by using a conductive adhesive instead of solder in the field of electronic component mounting.

[0002]

2. Description of the Related Art Recently, awareness of environmental issues has increased,
In the field of mounting in electronics, regulation of lead contained in solder is about to be enforced, and there is an urgent need to establish a joining technology that does not use lead for mounting electronic components. Lead-free mounting technology mainly includes lead-free solder and conductive adhesives. However, conductive adhesives, which are expected to have advantages such as flexibility of joints and lower mounting temperatures, are receiving more attention. .

Conventional conductive adhesives are generally obtained by dispersing a conductive filler in a resin-based adhesive component, and connect the connection terminals of an electronic component and the connection terminals of a circuit board with the adhesive interposed therebetween. After that, the resin is cured, and the electrical connection of the connection portion is secured by the contact between the conductive fillers in the adhesive. Therefore, since the connection portion is bonded with a resin, it has a merit that it flexibly responds to deformation due to heat or external force, and that the connection portion is less likely to crack as compared with solder in which the connection portion is an alloy. Therefore, it is expected as a substitute material for solder.

[0004]

When an electronic component is mounted using conventional solder, the solder melts during the reflow process and the electronic component moves due to its surface tension, so that a defect occurs in the reflow process. There is a possibility, and it is necessary to perform an electrical inspection after the component mounting process is completed. Even if a defect is found, a device that heats only that part is necessary to remove the part, and in some cases,
It is necessary to remove the solder. When re-mounting, re-heating is necessary, and a load is applied to the electronic components and the circuit board.

In the case of a conventional mounting method of a component using a conductive adhesive, an electrical connection is made by hardening the conductive adhesive. When a failure occurs in a typical inspection, it is difficult to repair a circuit board on which electronic components are mounted. In other words, as the resin in the conductive adhesive, a thermosetting resin is often used in order to secure the adhesive strength, and once the thermosetting resin is cured, the resin is repaired so that it can be repaired. This is because it is difficult to peel off the part.

Therefore, a conventional method of mounting a component using a conductive adhesive has been performed by the steps shown in FIG. First, a conductive adhesive is applied on the conductor electrodes of the circuit board (S
301) Then, the components are positioned and mounted (S30).
2). Next, after the conductive adhesive is cured (S303), an electrical inspection is performed (S304). As a result of the inspection, if the product is non-defective (S305), the mounting is completed (S30).
6). If it is not good, it is discarded (S307). Such inability to repair has caused a reduction in efficiency in the manufacturing process.

In some cases, a thermoplastic resin is used, but it is difficult to secure the adhesive strength, and it is often necessary to reinforce the resin with an underfill or the like.

Accordingly, an object of the present invention is to provide a method of mounting an electronic component so that the electronic component can be connected using a conductive adhesive and inspected in a state where the electronic component can be repaired. .

[0009]

A method for mounting an electronic component according to the present invention is a method for mounting an electronic component on a conductive electrode of a circuit board using a conductive adhesive. Applying a conductive adhesive on the conductor electrodes,
Positioning the electronic component and mounting it on the conductor electrode;
A step of pressing the electronic component against the circuit board, a step of performing an electrical continuity test between the circuit board and the electronic component, and, if the result of the test is good, curing the conductive adhesive to form the electronic component. And a step of completing the mounting. If the result of the inspection is defective, the electronic component is removed and replaced, and the steps from the step of applying the conductive adhesive to the step of conducting the continuity test are repeated.

According to this method, by applying a sufficient load even before curing, almost the same electrical characteristics as after curing can be obtained. Therefore, the inspection can be performed before the conductive adhesive is cured, and parts can be replaced or remounted as necessary. Inspect electrically in the uncured state of the conductive adhesive,
By curing only non-defective products, it is possible to eliminate defects during product production. In the case of mounting using a conductive adhesive, the electronic component does not move in the step of curing the conductive adhesive, so that the electronic component can be inspected before the curing step if it is electrically connected. Before curing, since the conductive adhesive is in a paste state, the components can be easily removed at room temperature, and the conductive adhesive can also be removed by wiping or the like. In this manner, replacement of components and re-mounting of components can be performed easily.

In the above method, preferably, when the electronic component is pressurized, a load at a portion where the electronic component and the circuit board are in contact with each other is set to 0.2 MPa or more. Thereby, it is possible to exhibit good electrical characteristics that can be inspected before the conductive adhesive is cured.

In the above method, the electronic component may be heated at a temperature lower than a temperature at which the conductive adhesive is cured when the electronic component is pressed. By raising the temperature, the viscosity of the conductive adhesive can be reduced, and electrical characteristics that can be inspected even with a low load can be exhibited. It should be noted that even when a load is simply applied without heating the electronic component when heating it, it is possible to exhibit electrical characteristics that can be inspected.

In the above method, preferably, vibration is applied when the electronic component is pressed. Electrical characteristics that can be inspected by load and vibration can be exhibited more suitably.

In the above method, the step of positioning and mounting the electronic component and the step of pressing the electronic component can be performed simultaneously. Thereby, the manufacturing process can be shortened, and the productivity can be improved.

In the above method, preferably, the content of the conductive filler in the conductive adhesive is 85 wt% or less. In the method of the present invention, the amount of the conductive filler is at least good in order to exhibit conductivity by a load. Thereby, since the amount of the resin in the conductive adhesive can be relatively increased, the adhesive strength of the electronic component can be increased. As the content of the conductive filler decreases, the resistance increases,
Even when the conductive filler is not contained at all, the electrode of the electronic component and the conductor electrode are in direct contact with each other due to the load, so that conduction can be exhibited even before curing.

In the above method, preferably, the conductive adhesive is configured to include at least a spherical filler and a flake-like conductive filler at the same time. A lower electric resistance can be obtained as compared with the case of only a spherical shape or the case of only a flake shape.

In the above method, preferably, the resin used for the conductive adhesive is a thermosetting resin. Thereby, testable electrical characteristics and sufficient adhesive strength of the electronic component after curing are obtained.

[0018]

(Embodiment 1) FIG. 1 shows steps of an electronic component mounting method according to Embodiment 1 of the present invention. First, a conductive adhesive is applied on the conductor electrodes of the circuit board (S101), and the components are positioned and mounted (S101).
102). Next, the component is pressurized (S103), and an electrical inspection is performed in that state (S104). As a result of the inspection, if the product is non-defective (S105), the conductive adhesive is cured by heating (S106), and the mounting is completed (S107). As a result of the inspection, if it is not a good product (S105), the component is removed and washed (S108), and a step of applying a conductive adhesive (S1).
01) is repeated. As described above, by electrically inspecting the conductive adhesive in an uncured state and curing only non-defective products, it is possible to eliminate defects at the time of manufacturing a product.

Next, a method for mounting an electronic component according to the present embodiment will be described in more detail with reference to FIG.

First, as the conductive adhesive, a conductive filler of silver (1: 1 spherical and flake-like) is 80 wt%.
And a thermosetting resin containing an epoxy resin. Then, as shown in FIG. 2A, as a circuit board,
Glass epoxy board 1 with circuit pattern formed of copper foil
Was prepared. The circuit pattern formed on the glass epoxy substrate 1 includes a conductor electrode 2 and a measurement pad 3.

Next, as shown in FIG.
The conductive adhesive 4 is applied by dispensing on the top, and FIG.
As shown in (c), the chip resistor 5 (here, 3216
Short chip). Next, as shown in FIG. 2D, the chip resistor 5 was pressed using the pressing jig 6. The pressing surface of the chip resistor 5 is 3.2 mm x 1.6 mm
Is the size of The resistance values before and after curing with respect to the load at this time are shown in (Table 1). In addition, about the same load, it investigated about the case where it heats at 50 degreeC during pressurization, and the case where it does not heat, respectively.

According to the embodiment shown in Table 1, the load was set to 0.2MP.
It can be seen that a value of a or more shows a sufficiently low resistance value even before curing. In addition, it shows a sufficient resistance value without heating when pressing. In this manner, an electrical inspection can be performed before the conductive adhesive is cured, and the electronic component can be easily replaced.

[0023]

[Table 1]

(Embodiment 2) As in Embodiment 1,
A chip resistor was mounted. Next, when pressurizing the chip resistor, the resistance value was measured while applying vibration. The results are shown in (Table 2). The applied vibration has a frequency of 50H
z, amplitude 2 microns.

From Table 2, it can be seen that by applying vibration, a sufficiently low resistance value can be obtained even before curing. The vibration may have a frequency of about several tens of Hz, and a frequency of 20 kHz.
Ultrasonic vibration of z or more may be used.

[0026]

[Table 2]

(Embodiment 3) As in Embodiment 1, silver (spherical and flake-like 1: 1) is used as a conductive filler and a thermosetting resin is used as a resin. Epoxy resin was used. However, a conductive filler whose content was changed from 70 wt% to 90 wt% was prepared.
The results of comparing the shear strengths with each conductive adhesive are shown in (Table 3). The shear strength indicates a shear force when a break is reached when a shear force is applied horizontally and vertically to a longitudinal portion of the chip component.

[0028]

[Table 3]

As the content of the conductive filler increases, the volume of the resin component in the conductive adhesive decreases, so that the shear strength decreases. When the conductive filler is contained in an amount of 85 wt% or more, the volume of the resin decreases, and when the conductive filler is 90 wt%, the volume ratio becomes about 50%. From Table 3, it can be seen that when the conductive filler is 85 wt% or less, the shear strength can be maintained at 3.8 kg, and there is no practical problem.

(Embodiment 4) As a resin of the conductive adhesive, an epoxy resin of a thermosetting resin was prepared. Although 80 wt% of silver was contained as the conductive filler, the mixing ratio of the spherical powder and the flake powder was changed at that time. Table 4 shows the relationship between the compounding ratio and the resistance value.

[0031]

[Table 4]

It can be seen that the resistance value is reduced by containing both the spherical powder and the flake powder. In the case of flake-like powder alone, the surface area of the conductive filler increases and the volume resistance of the conductive adhesive decreases, but the contact resistance with components and substrates decreases by including the spherical powder together, resulting in a lower resistance value. Is obtained. If the compounding ratio of the spherical powder is 25 to 75 wt%, a practically preferable resistance value can be obtained, but the content ratio is more preferably close to 1: 1.

In the embodiment described above, a chip resistor has been described as an electronic component.
Needless to say, it can be applied to a bare IC chip and other electronic components.

[0034]

According to the present invention, by applying a sufficient load even before curing, almost the same electrical characteristics as those after curing can be obtained, and the electrical conductivity of the conductive adhesive in an uncured state is obtained. Can be inspected. Inspection can be performed before the conductive adhesive is cured, and parts can be replaced or re-mounted if necessary. By curing only non-defective products, it is possible to eliminate defects during product production.

[Brief description of the drawings]

FIG. 1 is a process chart showing a mounting method of an electronic component according to an embodiment of the present invention.

FIGS. 2A to 2C show a mounting method of an electronic component according to an embodiment of the present invention for each step, wherein FIGS. 2A to 2C are plan views and FIG.

FIG. 3 is a process diagram showing a method for mounting an electronic component using a conventional conductive adhesive.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Glass epoxy board 2 Conductor electrode 3 Measurement pad 4 Conductive adhesive 5 Chip resistance 6 Jig for press

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroki Takezawa 1006 Kazuma Kadoma, Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (72) Takashi Kitae 1006 Kadoma Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co. Terms (reference) 5E319 AA03 AA07 BB11 CC61 CD04

Claims (8)

[Claims] 1. A method of mounting an electronic component on a conductive electrode of a circuit board using a conductive adhesive, the method comprising: applying the conductive adhesive on the conductive electrode; and positioning the electronic component. A step of mounting on the conductor electrode, a step of pressing the electronic component against the circuit board, a step of performing an electrical continuity test between the circuit board and the electronic component, and a result of the test being good. Curing the conductive adhesive, and completing the mounting of the electronic component.If the result of the inspection is defective, the electronic component is removed and replaced, and the conductive adhesive is removed. A method of mounting an electronic component, comprising repeating a process from a step of applying an agent to a step of performing the conduction test. 2. The method for mounting an electronic component according to claim 1, wherein, when pressing the electronic component, a load at a portion where the electronic component and the circuit board are in contact with each other is set to 0.2 MPa or more. 3. The method for mounting an electronic component according to claim 1, wherein the pressing of the electronic component is performed at a temperature lower than a temperature at which the conductive adhesive cures. 4. The method for mounting an electronic component according to claim 1, wherein vibration is applied when the electronic component is pressurized. 5. The method according to claim 1, wherein the step of positioning and mounting the electronic component and the step of pressing the electronic component are performed simultaneously. 6. The conductive filler according to claim 1, wherein the content of the conductive filler in the conductive adhesive is 85 wt% or less.
6. The method for mounting an electronic component according to any one of claims 1 to 5. 7. The electronic component mounting method according to claim 1, wherein the conductive adhesive includes at least a spherical filler and a flake-like conductive filler at the same time. . 8. The electronic component mounting method according to claim 1, wherein the resin used for the conductive adhesive is a thermosetting resin.