JPH0918123A - Method and structure for mounting electronic component on printed board - Google Patents

Abstract

PURPOSE: To enhance the reliability by ensuring higher bonding strength between a printed board and an electronic component as compared with conventional one when a conductive adhesive is employed as a conducting material. CONSTITUTION: In a printed board having a land 3 for connecting a component formed an a basic material, the land 3 is cut partially to provide a part 4 where the surface of basic material is exposed in the land forming region S. When an electronic component is mounted on the printed board, the electronic component is connected electrically and mechanically to the land forming region S including the exposed part 4 through a conductive adhesive.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed board having a land for connecting parts on a base material, a mounting method and a mounting structure for electronic parts using the same.

[0002]

2. Description of the Related Art Generally, electronic components mounted on a printed circuit board are roughly classified into a surface mounting type and a pin insertion type according to their mounting form. Of these, circular lands are formed on the printed circuit board for pin insertion type electronic components, and square lands are formed for surface-mounted components such as chip resistors and chip capacitors.

FIG. 6 is a perspective view showing a mounting form of a surface mounting type electronic component. In FIG. 6, a pair of lands 3 corresponding to the electrode configurations of the three electronic components 2 are provided on the printed circuit board 1.
Are formed at three locations. Further, each electronic component 2 is fixed to the printed board 1 by the conductive material supplied to each land 3. This conductive material is printed circuit board 1.
Is to electrically and mechanically connect the electrode part of the electronic component 2 to the land 3 of Sn.
(Tin) -based solder is often used. Here, in the conventional printed circuit board, as shown in FIG. 7A, lands 3 are formed in accordance with the shape and dimensions of the electrodes 2a of the electronic component 2, and when mounting the components, the land 3 is shown in FIG. 7B. As described above, the conductive material is applied over substantially the entire area (hatched area) of the land 3 to mount the electronic component 2 on the printed board 1.

However, when solder is used as the conductive material, Sn and Pb are separated from each other within a long period of time to cause cracks in the solder joint portion, and some electronic parts have a heating effect during solder reflow. Some are thermally damaged by. Therefore, a conductive adhesive (adhesive of epoxy resin mainly containing silver filler) that can absorb heat strain and prevent cracks and can be cured at a low temperature level is used as a conductive material instead of solder. May be used.

[0005]

However, since the conductive adhesive containing an epoxy or polyimide resin as a main component has a difficulty in adhering to a metal surface, the land 3 formed of copper foil or the like has a problem. When the electronic component 2 is connected using a conductive adhesive, the adhesive strength of the electronic component 2 to the printed circuit board 1 is lower than that in the case where solder is used as the conductive material, and vibration resistance and impact resistance are improved. In that respect, there was the inconvenience of lack of reliability.

The present invention has been made to solve the above problems, and its object is to achieve higher adhesion between a printed circuit board and an electronic component than before when a conductive adhesive is used as a conductive material. It is to secure strength and improve reliability.

[0007]

In a printed circuit board according to the present invention, a land for connecting parts is formed on a base material serving as a base, and an exposed portion is formed by exposing the surface of the base material in a region where the land is formed. Is adopted. In addition, as a method of mounting an electronic component according to the present invention, a printed circuit board having a land for component connection formed on a base material and an exposed portion formed by exposing the surface of the base material in a region where the land is formed is provided. First, a paste-like conductive adhesive is applied to the land forming area including the exposed portion, and then the surface mount type electronic component is applied to the printed board through the conductive adhesive applied to the land forming area. A procedure of temporarily fixing and then hardening the conductive adhesive to permanently fix the electronic component to the printed circuit board is adopted. Further, as a mounting structure of an electronic component according to the present invention, a land for component connection is formed on a base material, and a printed circuit board provided with an exposed portion which exposes the surface of the base material in a region where the land is formed, ,
The surface mounting type electronic component electrically and mechanically connected to the formation region of the land including the exposed portion via the conductive adhesive is adopted.

[0008]

In the present invention, as the printed circuit board in which the land for connecting the components is formed on the base material, the exposed portion formed by exposing the surface of the base material is provided in the area where the land is formed. When mounting electronic parts using this,
A paste-like conductive adhesive is applied to the land formation region including the exposed portion, and the electronic component is temporarily fixed to the printed circuit board with the conductive adhesive, and then the conductive adhesive is cured to form the electronic component. If you fix it permanently on the printed circuit board,
The electronic component can be electrically and mechanically connected to the land formation region including the exposed portion via the conductive adhesive. As a result, the electronic components will be mechanically connected not only to the land parts such as copper foil but also to the exposed parts where the surface of the base material is exposed by the conductive adhesive, so that the electronic parts for the printed circuit board The adhesive strength of.

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings. In this embodiment, the same components as those in the conventional example will be designated by the same reference numerals.
FIG. 1 is a plan view of a main part showing an embodiment of a printed circuit board according to the present invention. In the figure, (a) shows a land form before adhesive application, and (b) shows an adhesive application area on the land. Is shown. First, in the printed circuit board according to the present embodiment, as shown in FIG. 1A, an electrode form of an electronic component to be mounted, for example, an electrode of a chip-shaped surface mount component such as a chip resistor is mounted on a base material serving as a base. A pair of lands 3 is formed corresponding to the shape. Here, in the conventional printed circuit board, with respect to the land formation region S indicated by the alternate long and short dash line in the figure,
Although the lands 3 of copper foil or the like are formed over the entire area, in the present embodiment, the inner side portions of the respective lands 3 facing each other are cut out in a substantially semicircular shape by patterning,
As a result, the exposed portion 4 that exposes the surface of the base material is provided in the land formation region S.

By the way, in the above-mentioned exposed portion 4, in addition to exposing the underlying portion of the printed circuit board as it is, a resist film serving as a pattern protective film may be exposed as the substrate surface. Further, the shape, size, and the like of the exposed portion 4 in the land formation region S may be appropriately set in consideration of the electrical contact area (which affects the contact resistance) at the joint portion and the desired adhesive strength.

When an electronic component is mounted using this printed board, first, as shown in FIG. 1B, a land forming region S (FIG. 1) including the exposed portion 4 exposing the surface of the base material as described above. The paste-like conductive adhesive is applied to the middle hatched region) by using a coating device such as a dispenser or a screen printing machine. Next, as shown in FIGS. 2A and 2B, the land forming region S on the base material 5 and the electrode 2a of the electronic component 2 are aligned, and the electronic component 2 is mounted on the printed board. At this time, the electrode 2a portion of the electronic component is pressed against the conductive adhesive 6 applied to the land formation region S, and is temporarily fixed to the printed board with its adhesive force. Incidentally, the temporary fixing of the electronic component 2 is usually performed by a mounter device in consideration of productivity and positioning accuracy. Subsequently, the printed circuit board on which the electronic component 2 is temporarily fixed is put into a heating furnace, and heat treatment is performed there until the curing temperature of the conductive adhesive 6 (about 100 ° C. for an adhesive mainly containing epoxy resin). To do. As a result, the conductive adhesive 6 is completely cured and the electronic component 2 is permanently fixed to the printed board.

In the electronic component mounting structure thus obtained, the electronic component 2 is electrically and mechanically connected to the land forming region S including the exposed portion 4 via the conductive adhesive 6. Become. That is, the electrode 2a portion of the electronic component 2 is mechanically connected not only to the land 3 but also to the exposed portion 4 where the surface of the base material 5 is exposed by the conductive adhesive 6. Therefore, since the conductive adhesive 6 has better adhesiveness to the surface (exposed portion 4) of the base material 5 than the land 3, the adhesive between the printed circuit board and the electronic component 2 is higher than before. Strength will be obtained.

By comparison, the adhesive strength between the printed circuit board and the electronic component depending on the presence or absence of the exposed portion 4 was confirmed to be 10 to 20% higher when the exposed portion 4 was provided.

Incidentally, as a land form when the exposed portion 4 is provided in the land formation region S, each land 3 is as described above.
In addition to the cutout of the inner side of the
As shown in (a) and (b), the exposed portion 4 is provided in the land formation region S by cutting out the outer side portion of each land 3, and the land formation region S including the exposed portion 4 is made conductive. Setting as the application area (hatching area) of the adhesive
Alternatively, as shown in FIGS. 4A and 4B, the exposed portion 4 is provided in the land formation region S by partially hollowing out the inside of each land 3, and the land including the exposed portion 4 in the land is formed. The formation area S may be set as a conductive adhesive application area (hatched area).

Furthermore, when it is desired to increase the adhesive hardness between the printed circuit board and the electronic component 2 while ensuring a sufficient electrical contact area between them, as shown in FIGS. 3 is swollen outward, and a part of the swollen portion is hollowed out to provide an exposed portion 4 in the land forming area S, and the land forming area S including the exposed portion 4 is coated with a conductive adhesive. It may be set as an area (hatching area).

In addition, although the present embodiment has been described by taking a rectangular chip-shaped component as an example of an electronic component mounted on a printed circuit board, the present invention is not limited to the application to the chip-shaped component, but may be applied to, for example, a surface. The present invention can be applied to all electronic components that are surface-mounted on a printed circuit board, such as mountable semiconductor packages and various module parts, as mounting targets.

[0017]

As described above, according to the present invention, as a structure of a printed circuit board in which lands for connecting components are formed on a base material, the exposure is performed by exposing the surface of the base material in a land formation region. Since a portion is provided, when mounting an electronic component on this printed circuit board, a paste-like conductive adhesive is applied to a land forming region including an exposed portion,
By electrically and mechanically connecting the electronic component to the land formation region including the exposed portion via the conductive adhesive, the adhesive strength of the electronic component to the printed circuit board can be increased as compared with the conventional case. As a result, even when a conductive adhesive is used as the conductive material in order to avoid the occurrence of cracks at the joint and thermal damage to the electronic components, the adhesive strength of the electronic components to the printed circuit board is increased and vibration resistance is increased. A mounting structure for electronic components that is highly reliable in terms of durability and impact resistance is realized.

[Brief description of the drawings]

FIG. 1 is a plan view of an essential part showing an embodiment of a printed circuit board according to the present invention.

FIG. 2 is a diagram illustrating a mounting form of an electronic component according to the present invention.

FIG. 3 is a plan view (No. 1) of a main part showing a modified example of the printed circuit board according to the present invention.

FIG. 4 is a main part plan view (part 2) showing a modified example of the printed circuit board according to the present invention.

FIG. 5 is a plan view (No. 3) of a main part showing a modified example of the printed circuit board according to the present invention.

FIG. 6 is a perspective view showing a mounting form of a surface mounting type electronic component.

FIG. 7 is a plan view of a principal part showing the configuration of a conventional printed circuit board.

[Explanation of symbols]

 1 Printed Circuit Board 2 Electronic Component 3 Land 4 Exposed Area S Land Forming Area

Claims (3)

[Claims] 1. A printed circuit board in which a land for connecting components is formed on a base material, wherein an exposed portion exposing a surface of the base material is provided in a region where the land is formed. Printed board. 2. A printed circuit board, wherein a land for connecting parts is formed on a base material, and an exposed portion formed by exposing the surface of the base material is provided in an area where the land is formed. A paste-like conductive adhesive is applied to the land forming region including the area, and then a surface mount type electronic component is temporarily attached to the printed board through the conductive adhesive applied to the land forming region. A method of mounting an electronic component, comprising fixing, and thereafter, curing the conductive adhesive to permanently fix the electronic component to the printed circuit board. 3. A printed circuit board, in which a land for connecting a component is formed on a base material, and an exposed portion formed by exposing the surface of the base material is provided in a region where the land is formed, and the printed circuit board including the exposed portion. A mounting structure of an electronic component, comprising: a surface mounting type electronic component electrically and mechanically connected to a land formation region via a conductive adhesive.