JPS6010798A - Method of mounting circuit element - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for mounting a circuit element on a circuit board of an electronic device.

Conventional configurations and their problems - 1 - In recent years, as the demand for smaller and lighter electronic devices has increased, circuit elements that make up electronic devices have rapidly become smaller and leadless. It's here. Recently, technology for integrating these circuit elements on a circuit board at high density has become an important issue.

Conventionally, leadless small circuit elements and even planar connection type small circuit elements with leads, such as metal glaze chip resistors, multilayer ceramic chip capacitors, mini-molded transistors, and even semiconductors. The general method for mounting chip carrier-type semiconductor devices, etc., which are ultra-small packages of IC or LSI chips, on a circuit board with fine wiring is to go through the steps shown in Figure 1A-C. be exposed. In this method, first, as shown in FIG. 1A, a circuit board is used, in which wiring circuit conductors 2 are formed on the surface of an extremely rigid substrate 1 made of a synthetic resin substrate such as glass epoxy or a ceramic such as alumina. As shown in Fig. 1B, cream solder 3 is applied to the wiring circuit conductor 2 of this circuit board -2-, and then, as shown in Fig. The small circuit elements 4a and 4h are placed on a circuit board so that their connection terminals are in contact with the creamy solder 3, and the circuit board is passed through a high-temperature furnace to remelt the solder 3, which is the so-called solder reflow method, to make a planar connection. This is a method of attaching a type of small circuit element 4a and a persimmon to a circuit board.

However, this conventional circuit element mounting method has the following disadvantages.

■ is Iυ At the time of reflow, small circuit elements 4a and 4b
However, the highly integrated circuit structure is difficult.

■ During solder reflow, droplets of the solder 3 are scattered together with the flux contained in the solder cream, and a short circuit between the wiring circuit conductors 2 is likely to occur.

■ When small circuit elements 4a and 4h are packed together or when mounting items with narrow terminal pitches, such as small packages for semiconductor ICs, solder bridges and poor connections may occur. ), the correction is complicated.

[Solder ref] Since the small circuit elements 4a and 4b are exposed to high temperatures at one time, the heat resistance of the circuit board is restricted.

OBJECTS OF THE INVENTION The present invention solves the above-mentioned conventional drawbacks, and an object of the present invention is to provide a method for mounting circuit elements that can configure a more highly integrated electronic circuit board when assembling electronic equipment. .

Structure of the Invention In order to achieve the object (h), the method for mounting a circuit element of the present invention is to mount a circuit element on a flat surface using an adhesive on a circuit board on which a conductive layer in the form of a wiring circuit is formed on at least one main surface of an insulating board. A connection type circuit element is fixed, and a conductive metal layer is formed by electroless plating to electrically connect the circuit board and the circuit element.

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Description of Examples] Hereinafter, one embodiment of the present invention will be described based on the drawings. I will explain.

FIGS. 2A to 2D are sectional views of essential parts of the circuit board at each step for explaining the mounting method of a flat connection type small circuit element. In Fig. 2, 5 is an insulating substrate, 6 is a wiring circuit-shaped conductor layer formed on the insulating substrate 5, 7 is an adhesive applied between the conductor layers 6 and 6, and 8a and 8b are planar connection type. The small circuit element 9 is a conductive metal layer deposited by electroless plating.

When installing the circuit elements, first, as shown in FIG. 2, a wiring circuit-shaped conductor layer 6 made of copper foil is formed on the main surface of an insulating substrate 5 made of a synthetic resin substrate such as a glass epoxy laminate. Using a circuit board, as shown in Figure 2B, an adhesive 7 made of a thermosetting resin such as epoxy resin or acrylic resin is applied between the conductor layers 6.6 of the circuit board using a screen printing method or a dispenser. A predetermined amount of adhesive is applied, and then, as shown in FIG. - Equipped with multi-layer chip resistors, multilayer ceramic chip capacitors, leadless tantalum solid electrolytic capacitors, multilayer chip inductors, and ultra-small resin molded packages for semiconductor ICs and LSI chips. After pressurizing the external connection terminals of each small circuit element 8a, 8b and bringing them into precise contact with the η body layer 6 of the circuit board, and curing the adhesive 7 by heating, the circuit board is bonded with copper, nickel, etc. The conductor layer 6 and small circuit elements 8 of the circuit board are immersed in an electroless plating solution as shown in the second diagram.
A conductive gold R layer 9 made of copper or nickel is deposited on the external connection terminals 8a and 8b to electrically connect the small circuit elements 8a and 8b to the conductor layer 6 of the circuit board.

FIG. 3 is a cross-sectional view of a main part of a circuit board for explaining the second embodiment. A so-called conductive adhesive 10 in which fine powder of copper or silver is dispersed in a thermosetting resin such as an epoxy resin is applied to the conductor layer 6 to form a small circuit element 8a.

8b is fixed and electroless plating is used to create S-electrode adhesion-6.
- A conductive metal layer 9 is deposited on the surface of the agent 10.

In this embodiment, electroless bonding is performed with the small circuit elements 8a and 8h electrically connected in advance to the conductor layer 6 of the circuit board using a conductive adhesive 10, thereby achieving a more reliable electrical connection. (Characterized by 1c).

In addition, in the embodiment shown in "-", the small circuit element Ra.

An example has been described in which a conductor layer 6 made of copper foil is formed on an insulating substrate 5 made of a synthetic resin such as a glass boxy laminate as a circuit board for attaching the 8b. J: U'/, it is not limited to the composition,
A conductor layer 6 is formed on an insulating substrate 5 made of ceramics such as alumina by high-temperature firing using a so-called thick film paste made of silver, copper, tungsten, molybdenum, etc., or a conductive layer 6 made of polyimide, polyester, etc. There are various types of F according to the purpose of use, such as one in which nine layers 6 made of copper foil are formed on a film-like insulating substrate 5.
Of course, a 1':I filter is used.

Moreover, the small circuit element 8a, Rh is coated with an electroless plating solution.
7- Since the capacitor is immersed in the electroless potting solution, it is essential to use a capacitor with a structure that does not deteriorate its characteristics due to the electroless potting solution, but ordinary ceramic-based leadless dip resistors and bump capacitors are It was confirmed that it was sufficiently durable for use. However, in semiconductor ICs and LSIs, it has been confirmed that if the chips are not made of resin or hermetically sealed chips, they will have poor characteristics.

DETAILED DESCRIPTION OF THE INVENTION According to the present invention, the following effects can be obtained compared to the conventional solder reflow method.

■ Since planar connection type circuit elements are electrically connected to the circuit board using electroless plating, even if the circuit elements are mounted closely together on the circuit board, the electrical connection can be made reliably, making it possible to achieve high integration. A circuit board can be obtained.

(4) Since high temperatures as in the solder reflow method are not required when connecting circuit elements, there are no restrictions regarding the temperature of the circuit elements or the humidity of the circuit board, providing greater freedom of choice.

■ Even when installing a large number of circuit elements with extremely small pitches of external connection terminals, especially semiconductor ICs or [circuit boards made of ultra-compact ST chips packaged into five wires] There is no short circuit at all, a reliable electrical connection is possible, and the reliability of the connection is also extremely good compared to those connected by soldering.

[Brief explanation of the drawing]

Figures 1 Δ to C are cross-sectional views of the main parts of the circuit board at the main T section of the K East method, and Figures 2 A to D are the method for mounting circuit elements in the first embodiment of the present invention. Fig. 3 is a cross-sectional view of a main part of a circuit board in which a circuit element is attached by one method of removing a circuit element in a second embodiment of the present invention. 5...IP! Edge board board...conductor layer, 7, 10...
・Adhesive, 8a, 8b... Small circuit element (circuit element), 9... Conductive metal layer -9- Figure I (A) CB>

Claims (1)

[Claims] 1. A planar connection type circuit element is fixed using an adhesive to a circuit board which has a conductor layer in the form of a wiring circuit on at least one main surface of an insulating substrate, and is conductive by electroless plating. A method for mounting a circuit element in which a metal layer is formed to electrically connect the circuit board and the circuit element. 2. When fixing the circuit element to the circuit board, a conductive adhesive is applied to the conductive layer of the circuit board, and the external connection terminals of the circuit element are fixed with the conductive adhesive. The method for installing the circuit elements described in Scope 1.