JPH0563343A - Electronic parts packaging method - Google Patents

Abstract

PURPOSE:To enable application of a parts or a board of low thermal resistance, reduce the cost of the parts or the board itself, enable simultaneous packaging of electronic parts such as a liquid crystal display element and an aluminum electrolytic capacitor of essentially low thermal resistance which packaging has been impossible in the conventional techique, and simplify a packaging process. CONSTITUTION:Thermoplastic resin is used as the material of an insulative board 2. Conductive adhesive agent 11 or anisotropic conductive adhesive agent is used for connecting an electronic parts 4 with a conductor pattern 3. The conductive adhesive agent 11 or the anisotropic conductive adhesive agent is kept at a temperature lower than or equal to the thermal deformation temperature of the thermoplastic resin, and thermoset.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic component mounting method for mounting and connecting surface mounting type electronic components on the surface of a printed wiring board.

[0002]

2. Description of the Related Art Conventionally, as a method of mounting various electronic components such as a semiconductor IC on a printed wiring board, a method of melting and joining solder has been widely used.

However, in the surface mounting method using solder, a component standing (tombstone / Manhattan) phenomenon caused by a remarkably large surface tension of molten solder, a connection failure trouble such as short circuit between circuit terminals due to generation of solder balls, Furthermore, the problem of using CFCs in the removal and cleaning of residual flux (depletion of the earth's ozone layer) has become a serious problem. Furthermore, surface mounting makes it difficult to heat only the necessary connection parts, and it is generally called a "reflow furnace". Due to the fact that a soldering method that passes through the whole is used, extremely harsh heat is applied to the parts / boards, and particularly strict heat resistance design is required for the parts. The above sacrifice is great.

Moreover, this heat resistance is not essentially required except in very special cases in electronic equipment, and is heat resistance in the so-called process (process) which is necessary only during soldering and originally It is useless performance that is not needed at all.
In addition, liquid crystal display elements, aluminum electrolytic capacitors, and other parts that are not inherently heat-resistant to soldering temperatures cannot be mounted at the same time, so they must be mounted as a separate process, resulting in a significant decrease in productivity and cost. The fact is that the rise in

For these reasons, a "low temperature solder", which is a conventional tin-lead alloy solder added with bismuth or the like in order to lower the soldering temperature, has been studied and partially put into practical use. The temperature is at most 130 degrees Celsius
However, there is a problem that the temperature is limited and there is a limit to lowering the temperature, and the mechanical strength is significantly lowered.

Although it has been attempted to use a conductive adhesive or an anisotropic conductive adhesive instead of solder, in the past, a heat curing temperature of at least about 150 degrees Celsius was required, and the temperature was lowered. The merit is small, and the liquid crystal display element, the aluminum electrolytic capacitor, and the like described above cannot be mounted at the same time. Therefore, there is almost no merit compared to the low-temperature solder, and it has not been put to practical use.

[0007]

In view of the above problems, the present invention makes it possible to use a component or substrate having low heat resistance by significantly reducing the temperature for connection, and the cost of the component or substrate itself. Mounting that can reduce the cost and simplifies the mounting process by enabling simultaneous mounting of electronic components with inherently low heat resistance, such as liquid crystal display elements and aluminum electrolytic capacitors, which was impossible in the past. It provides a method.

[0008]

In order to solve the above-mentioned problems, the mounting method according to the invention of claim 1 is a surface mounting type electronic component on a printed wiring board having a conductor pattern on the surface of an insulating substrate. In the electronic component mounting method for mounting and connecting, a conductive adhesive or an anisotropic conductive adhesive is used for connection between the electronic component and the conductor pattern, and the conductive adhesive or the anisotropic conductive is used. The heat-curable adhesive is held at a temperature of 100 degrees Celsius or less to be thermally cured.

In a mounting method according to a second aspect of the present invention, a thermoplastic resin is used as a material for the insulating substrate, and a conductive adhesive or an anisotropic conductive adhesive is used for connecting the electronic component and the conductor pattern. While using, the conductive adhesive or the anisotropic conductive adhesive is heat-cured while being held at a temperature equal to or lower than the thermal deformation temperature of the thermoplastic resin.

In the mounting method according to the third aspect of the invention, the resin component of the conductive adhesive or the anisotropic conductive adhesive is mainly composed of a thermosetting resin. In the mounting method according to the fourth aspect of the invention, the electronic component includes an electronic component having low soldering heat resistance such as a liquid crystal display element or an aluminum electrolytic capacitor.

[0011]

[Operation] In order to connect electronic parts to the printed wiring board,
A conductive adhesive or the anisotropic conductive adhesive is used, and this is held at a temperature lower than the conventional temperature of 100 degrees Celsius or less and thermally cured. This prevents the electronic components from being thermally damaged.

A thermoplastic resin is used as the material of the insulating substrate. In that case, the conductive adhesive or the anisotropic conductive adhesive is held at a temperature lower than the thermal deformation temperature of the thermoplastic resin and thermally cured. This prevents thermal damage to the insulating substrate and the electronic components.

[0013]

1 is a view showing a part of a printed board unit according to an electronic component mounting method according to the present invention. In FIG. 1, a printed wiring board 1 has an insulating substrate 2 made of a thermoplastic resin and a conductor pattern 3 formed on the surface of the insulating substrate 2. This printed wiring board 1 has electronic components 4
In order to mount, the conductive adhesive 11 is applied to the land portion on the surface of the conductor pattern 3, the electronic component 4 is placed so as to match the conductor pattern 3, and the material used for the insulating substrate 2 is Temperature lower than heat distortion temperature, that is, insulating substrate 2
The conductive adhesive 11 is cured in a state where the temperature is maintained so as not to cause deformation, and the electronic component 4 is fixed and electrically connected to the printed wiring board 1 by the conductive adhesive 11.

Here, as the material of the insulating substrate 2, polystyrene, polyolefin, ABS resin, AS resin, PM
A relatively inexpensive general-purpose thermoplastic resin such as MA, polycarbonate, or rigid PVC can be used. Since these thermoplastic resins are inferior in heat resistance to the thermosetting resins, in a conventional electronic component mounting method for connecting at a relatively high temperature of about 150 to 230 degrees Celsius, as a material for an insulating substrate, It has not been used.

However, in addition to these thermoplastic resins, it is also possible to use conventionally used materials such as paper phenol resin or glass epoxy resin.
It is also possible to use a flexible substrate based on polyimide or polyester.

As a method of forming the conductor pattern 3,
Various conventional pattern forming methods can be used, such as a subtractive method using a copper clad laminate as a material and an additive method using electroless plating.

It is also possible to form a circuit using conductive ink or the like, and it is also possible to use an ITO wiring film on a glass substrate such as a liquid crystal display element or a conductive paste wiring film on a ceramic substrate such as alumina. It is possible.

Further, an external housing of an electronic device formed by injection molding of a thermoplastic resin is used as an insulating substrate 2, and a conductor pattern 3 is formed on the inner surface side of the external housing with a conductive paste or the like to form a printed wiring board 1. It is also possible to use

The electronic component 4 is preferably a surface mounting type, but a pin insertion mounting type can also be mixedly mounted. In the pin insertion mounting type, for example, after mechanically fixing to the printed wiring board 1 using a fixing adhesive or the like, electrical connection may be made with the conductive adhesive 11.

The electronic component 4 is supplied by a so-called SOP (small outline package), QFP (quad flat package), a semiconductor IC with a lead such as DIP (dual inline package), or a TAB (tape automated bonding) method. Semiconductor ICs such as semiconductor ICs or semiconductor ICs supplied as paired chips such as flip chips, semiconductor parts such as transistors or diodes, passive circuit parts such as resistors, capacitors, coils, and mechanical parts such as switches or connectors. Various electronic components such as a display device such as a liquid crystal display element can be used.

Among these electronic components, even those that are structurally inferior in heat resistance, such as an aluminum electrolytic capacitor or a liquid crystal display element, have a low temperature for thermosetting the conductive adhesive 11, The occurrence of thermal damage as in the case of using the conventional electronic component mounting method in which connection is performed at a relatively high temperature is prevented, and the electronic component mounting method has a great advantage.

The conductive adhesive 11 is obtained by dispersing conductive particles in a resin or a resin composition, and is in the form of paste or film depending on the usage form. As the conductive particles, particles of gold, silver, copper, nickel, solder powder, carbon graphite, tin oxide, or the like, or a particulate powder having a metal plated surface can be used.

The resin and resin composition used for the conductive adhesive 11 are preferably thermosetting resins.
Examples thereof include phenol resin, unsaturated polyester resin, allyl resin, epoxy resin, silicone resin and acrylic ester resin.

Further, a curing agent, a curing accelerator, a cross-linking agent, a catalyst, a reaction initiator, etc. may be appropriately selected and used together with the thermosetting resin in accordance with the cured physical properties that match the purpose of use. Be done.

In consideration of stability during use, a thermosetting resin may be used as a main component together with a curing agent and the like in a two-component type, and the two may be mixed before use. Further, in order to improve the physical properties, various compounding agents such as a viscosity imparting agent, a softening agent,
Stabilizers, surface modifiers, antioxidants, reaction inhibitors, colorants, fillers, solvents, diluents and the like may be added.

The ratio of the conductive particles to the resin component is usually 100% based on the balance of adhesiveness and conductivity.
The range of 50 to 2500 parts by weight of conductive particles is preferable, and the range of 150 to 900 parts by weight of conductive particles is more preferable. If the ratio is out of this range, the conductive resistance becomes high, which is disadvantageous in practical use.

The curing temperature of the conductive adhesive 11 needs to be set low according to the heat resistance of the electronic component 4 and the material of the insulating substrate 2. It is necessary to cure at a temperature lower than the heat distortion temperature.

Generally, in view of the heat distortion temperature or heat resistance of the thermoplastic resin, the conductive adhesive 11 is set to 100 degrees Celsius.
It is preferable to perform heat curing at a temperature of not more than 80 degrees Celsius, particularly preferably at a temperature of not more than 80 degrees Celsius. When the thermosetting temperature is high, the electronic component 4 and the insulating substrate 2 are poor in heat resistance.
It is difficult to use materials for.

FIG. 2 is a view showing another example of a part of the printed board unit by the electronic component mounting method according to the present invention.

In FIG. 2, the anisotropic conductive adhesive 12 is used in place of the conductive adhesive 11. The anisotropic conductive adhesive 12 is inserted between the conductor pattern 3 and the electrode of the electronic component 4, and by thermocompression bonding the connecting portion of the electrode, the adhesive exhibits conductivity in the thickness direction and the surface direction. Shows an insulating property, whereby the conductor pattern 3 and the electronic component 4 are connected.

The anisotropic conductive adhesive 12 is obtained by dispersing conductive particles in a resin or resin composition having a high insulating property, and is formed into a paste or a film in accordance with the usage form. As the conductive particles, those similar to the case of the conductive adhesive 11 can be used, but other than that, for example, particles obtained by metal-plating plastic particles can be used.

As the resin or resin composition, the same one as in the case of the conductive adhesive 11 can be used. further,
A curing agent or the like is used as in the case of the conductive adhesive 11, and various compounding agents can be appropriately used. The curing temperature is similar to that of the conductive adhesive 11.

According to the above-mentioned embodiment, the conductive adhesive 11 or the anisotropic conductive adhesive 12 is applied at a lower temperature than before.
Is heat-cured, whereby the printed wiring board 1 and the electronic component 4 can be prevented from being damaged by heat, and the reliability of the connection in mounting the electronic component can be maintained.

By setting the thermosetting temperature lower than the thermal deformation temperature of the insulating substrate 2, an inexpensive general-purpose thermoplastic resin can be used as the material of the insulating substrate 2.
The cost of the printed wiring board 1 can be significantly reduced.

[0035]

Concrete Example A printed board unit for a digital liquid crystal timepiece was manufactured based on the electronic component mounting method of the present invention.

(Preparation of Styrene Substrate) On the surface of a polystyrene commercial extruded product (electrochemical HIE-4, thickness 2 mm, heat distortion temperature 78 ° C.), an epoxy adhesive (Epicoat 828 made of oiled shell epoxy was used as the main agent, and oil was used. Of epoxy resin epoxy Epomate B-002W as a curing agent, the main agent and the curing agent are mixed in a ratio of 2 to 1), and electrolytic copper foil (thickness 35 μm) is laminated and pressed at a temperature of 60 degrees Celsius. A copper-clad styrene substrate was prepared by pressurizing for 2 hours with a machine, then cooling and taking out after 24 hours.

(Preparation of Printed Wiring Board) A photomask having a pattern for a digital liquid crystal watch is prepared, and a conductor pattern for a digital liquid crystal watch is formed on the surface of the copper-clad styrene substrate prepared above by a conventional photolithography method. Was formed, and etching processing was performed, thereby forming a printed wiring board.

(Preparation of Conductive Adhesive) The following components were mixed and mixed and stirred to prepare a conductive adhesive. Epoxy resin Nippon Kayaku RE-304S 20 parts by weight Curing agent ACR H-3842 1.6 parts by weight Shikoku Chemicals Curesol 2MZ 0.5 parts by weight Conductive silver powder Tokuriki Chemical TCG-7 80 parts by weight

The conductive adhesive thus prepared was cured at 60 degrees Celsius for 2 hours and the volume resistance was measured.
It showed 10 ⁻⁴ ohm · cm.

(Electronic parts) Commercially available semiconductor IC (QFP)
MSM5055L-18, MSM6243-0
2, MSC1161, and laminated ceramic capacitor were used. As the liquid crystal display element and the switch, a commercially available pin insertion mounting method was used after being modified to the surface mounting method.

(Preparation of Printed Circuit Board Unit) After applying a conductive adhesive on the conductor pattern (on the land portion) of the printed wiring board by screen printing, all electronic components are placed and placed in an oven. Then, the conductive adhesive was thermally cured by heating at 60 degrees Celsius for 2 hours, and then taken out.

When a predetermined power source was connected to the produced digital liquid crystal timepiece, all the functions such as the time display function and the voice output function worked normally.

(Comparative Example of Making a Printed Board Unit) In the above-mentioned printed board unit making process, a digital liquid crystal timepiece for making a comparison was made by setting the heating temperature in the oven to 90 degrees Celsius (2 hours), and from the oven. When taken out and observed, the printed wiring board was significantly deformed.

[0044]

EFFECTS OF THE INVENTION According to the present invention, it is possible to use a component or substrate having low heat resistance to reduce the cost, and essential components such as a liquid crystal display element and an aluminum electrolytic capacitor which have been impossible in the past. It is possible to simultaneously mount electronic components with low heat resistance.

According to the second aspect of the invention, an inexpensive thermoplastic resin excellent in various electrical characteristics such as high frequency characteristics can be used as the material of the insulating substrate.

[Brief description of drawings]

FIG. 1 is a diagram showing a part of a printed board unit by an electronic component mounting method according to the present invention.

FIG. 2 is a diagram showing another example of a part of the printed board unit by the electronic component mounting method according to the present invention.

[Explanation of symbols]

 1 Printed Wiring Board 2 Insulating Substrate 3 Conductor Pattern 4 Electronic Component 11 Conductive Adhesive 12 Anisotropic Conductive Adhesive

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nobuo Shizugi 7-1 Akita-cho, Takatsuki-shi, Osaka Techno Sun Star Co., Ltd.

Claims (4)

[Claims] 1. An electronic component mounting method for mounting and connecting a surface mounting type electronic component on a printed wiring board having a conductor pattern on the surface of an insulating substrate, comprising: connecting the electronic component and the conductor pattern; A conductive adhesive or an anisotropic conductive adhesive is used for the connection, and the conductive adhesive or the anisotropic conductive adhesive is used in 1 degree Celsius.
An electronic component mounting method characterized by holding at a temperature of 00 ° C. or lower and thermally curing. 2. An electronic component mounting method for mounting and connecting a surface mounting type electronic component on a printed wiring board having a wiring pattern provided on a surface of an insulating substrate, wherein a thermoplastic resin is used as a material of the insulating substrate. And
While using a conductive adhesive or anisotropic conductive adhesive for connection between the electronic component and the conductor pattern, the conductive adhesive or the anisotropic conductive adhesive, the thermal deformation temperature of the thermoplastic resin or less A method for mounting electronic parts, characterized in that the method is carried out by holding the temperature at the temperature and thermally curing it. 3. The electronic component mounting method according to claim 1, wherein the resin component of the conductive adhesive or the anisotropic conductive adhesive is composed mainly of a thermosetting resin. 4. An electronic component having low soldering heat resistance such as a liquid crystal display element or an aluminum electrolytic capacitor is included as the electronic component.
Electronic component mounting method described.