JPH0732976U - Thick film circuit board - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To provide a thick film circuit board which achieves high density and has improved bonding reliability. [Structure] Wiring patterns 3 and 4 are provided on both main surfaces of an insulating substrate 2, and both wiring patterns 3 and 4 are land electrodes 5b and 5c.
In the thick film circuit board 1 formed by soldering the terminal electrodes 6b and 6c of the electronic component 6 which can be surface-mounted to the wiring patterns 3 and 4 while being connected by the conductive through hole 5 having The electrodes 6b and 6c are placed on the land electrodes 5b and 5c of the conduction through hole 5 and solder S-bonded.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a thick film circuit board in which surface mountable electronic components are arranged on a circuit board having arrangement patterns on both main surfaces of a ceramic and heat resistant glass epoxy board.

[0002]

[Prior art]

 When an electronic component is mounted on a thick film circuit board, the electronic component may be a lead terminal type electronic component having a lead terminal penetrating the thick film circuit board or a surface mount having a terminal electrode on the back surface of the electronic component body. Molded electronic components and surface-mounted electronic components in which lead terminals extending from the electronic component body are bent so as to be parallel to the thick film circuit board are used.

In the lead terminal type electronic component, the lead terminal of the electronic component is inserted into the lead terminal through hole formed in the wiring pattern portion, and solder is supplied around the penetrated lead terminal to perform solder joining. .

In the surface mount type electronic component, cream solder is applied on the wiring pattern of the thick film circuit board, the terminal electrode portion of the electronic component is placed on the cream solder, and reflow solder bonding is performed by a reflow furnace. Was.

[0005]

[Problems to be solved by the device]

 In recent years, in order to increase the density of wiring patterns formed on thick film circuit boards, wiring patterns have been formed on both main surfaces.

Regarding the electronic components to be mounted on the circuit board, the lead-type electronic components have a smaller occupied area for mounting, but it seems to be suitable for high density, but the solder bonding process is complicated. In consideration of the above, and that the back surface side becomes a dead space, the surface mount type electronic component as a whole is easier to deal with higher density and easier soldering.

However, in the conventional surface mount type electronic component, it is necessary to form an electrode pad in order to mount the surface mount type electronic component on the wiring pattern, and this electrode pad has been an obstacle to high density.

The present invention has been devised in view of the above problems, and an object thereof is to improve the mounting density of surface mounted electronic components to achieve higher density. Further, the present invention provides a thick film circuit board having improved bonding reliability.

[0009]

[Means for Solving the Problems]

 The present invention provides an electronic component having wiring patterns on both main surfaces of an insulating substrate, connecting both wiring patterns by a conductive through hole having a land electrode, and having a surface mountable terminal electrode on the insulating substrate. In the thick film circuit board, the terminal electrode of the electronic component is placed on the land electrode of the conductive through hole and solder-bonded.

[0010]

[Action]

 According to the present invention, since the predetermined wiring patterns are formed on both main surfaces of the circuit board, it is possible to achieve high density of the wiring patterns on the circuit board.

Further, since the electronic component mounted on the main surface is a surface mount type electronic component, the solder joining is application of cream solder, placement of the electronic component, and reflow treatment, so that a large number of electronic components are required. Solder joining can be performed collectively.

Since the terminal electrodes of the surface mount type electronic component are bonded to the land electrodes around the openings of the conductive through holes for connecting the wiring patterns formed on both main surfaces, the surface mount type electronic component is Since it is not necessary to form electrode pads only for connecting electronic components, the occupied area required for mounting the wiring patterns and electronic components is substantially reduced, so that higher density wiring patterns can be easily achieved. .

Further, the solder for joining the terminal electrode and the land electrode of the surface mount type electronic component is interposed at the interface between them, and further, on the inner wall surface of the conductive through hole orthogonal to the joining surface of the terminal electrode. A solder meniscus is also formed between the conductor film and the surface mounting type electronic component and the land electrode is soldered more firmly, so that the joint reliability is improved.

[0014]

【Example】

 Hereinafter, the present invention will be described with reference to the drawings. FIG. 1 is a partial plan view of a thick film circuit board according to the present invention, and FIG. 2 is a sectional view thereof.

The thick film circuit board of the present invention comprises a circuit board 1 including a board 2, a front side wiring pattern 3, a back side wiring pattern 4 and a conductive through hole 5, and a surface mount type electronic component 6. Has been done.

The board 2 that constitutes the circuit board 1 is made of ceramic, heat-resistant glass epoxy, or the like. A wiring pattern 3 having a predetermined pattern is formed on the front surface of the substrate 2, and a wiring pattern 4 having a predetermined pattern is formed on the back surface thereof. Further, the substrate 2 is formed with a through hole which penetrates in the thickness direction thereof and serves as a conductive through hole for connecting the two wiring patterns 3 and 4.

The wiring patterns 3 and 4 are formed by printing and baking a conductive paste containing Ag, Cu or the like as a main component.

The conductive through-holes 5 are, for example, conductor films 5a, 5b, and 5c on the inner wall surface having a through hole diameter of 100 to 800 μm and around both openings (hereinafter, the conductor film on the inner wall surface is simply referred to as the conductor film 5a, the front surface side periphery Is formed on the back surface side opening, and the conductor film around the opening on the back surface side is formed on the land electrode 5c.

Such a circuit board is formed by the following steps.

First, the substrate 2 having a through hole at a predetermined position is prepared. Next, the wiring pattern 3 on the front surface side is printed on the surface of the substrate 2 by screen printing using, for example, an Ag-based conductive paste, and dried. Next, the wiring pattern 4 on the back surface side is printed on the back surface of the substrate 2 by screen printing using, for example, an Ag-based conductive paste, and dried. Incidentally, when the wiring patterns 3 and 4 are printed, the wiring patterns 3 and 4 are formed by a pattern including the through holes to form the land electrodes 5b and 5c. As a result, by printing the pattern that becomes the land electrode 5b on the front surface side, the conductive paste is transmitted to the inner wall surface of the through hole, and a part of the conductor film 5a on the inner wall surface (on the front surface side) Part) is formed, and by printing a pattern to be the land electrode 5c on the back surface side, the conductive paste is transmitted to the inner wall surface of the through hole, and the conductive film on the inner wall surface is formed on the back surface side of the through hole. A part (a part on the back surface side) of 5a is formed, and by printing from both surfaces, a conductor film 5a having a predetermined thickness is formed on the inner wall surface of the through hole. Note that the conductive film 5a is formed on the inner wall surface by the weight of the conductive paste, but the viscosity of the conductive paste and the like play a large role. When a conductive paste having a high viscosity is used, the printing may be performed while applying a reduced pressure from the surface opposite to the printing surface and sucking the conductive paste from the through hole.

Thereafter, the wiring patterns 3 and 4, the conductive film 5a to be the conduction through hole 5, and the land electrodes 5b and 5c are baked at, for example, 500 to 700 ° C. in an oxidizing atmosphere (atmosphere) to thereby form a circuit board. 1 is achieved. Although the baking process is performed collectively in the above description, for example, from the front surface side of the substrate 2, the front surface side wiring pattern 3, a part of the conductor film 5a, and the land electrode 5b on the front surface side to the conductive paste. After printing, drying and baking are performed. Further, from the back surface side of the substrate 2, the back surface side wiring pattern 4, a part of the conductor film 5a, and the land electrode 5c on the back surface side are printed by a conductive paste. After forming and drying, baking may be performed.

The surface-mounted electronic component 6 is a chip-shaped electronic component in which terminal electrodes 6b and 6c are formed at opposite ends of an electronic component element body 6a, such as a laminated ceramic capacitor, a chip resistor element, and a multiple resistor resistor. Elements, chip coil elements, trimmer parts, etc., and electronic parts whose lead terminals extending from the electronic part element body are bent so that they can be surface-mounted in parallel to the surface of the substrate 2, although not shown, for example, Surface mount type oscillators, surface mount type dielectric filters, flat type semiconductor parts, hybrid type ICs and the like can be mentioned.

In the surface-mounted electronic component 6, the terminal electrodes 6b and 6c or the lead terminals subjected to bending treatment are surface-mounted via solder on a part of the wiring patterns 3 and 4 formed on both main surfaces of the substrate 2. It has been soldered.

Here, a characteristic of the present invention is that the wiring patterns 3 and 4 formed on the substrate 2 become part of the wiring patterns 3 and 4 in order to reduce the pattern area, and the terminals of the electronic component 6 are formed. That is, the electrode pads connected to the electrodes 6b, 6c, etc. are eliminated as much as possible.

Specifically, one or both of the electrode pads connected to the terminal electrodes 6b and 6c of the electronic component 6 are substituted for the land electrodes 5b and 5c. For example, in the figure, the conductive through hole 5 is covered with at least the terminal electrode 6b of the electronic component 6. That is, the terminal electrode 6b of the electronic component 6 is placed on the cream solder in which the terminal electrode 6b of the electronic component 6 is applied on the land electrode 5b on the front surface side, and the reflow process is performed to place the terminal electrode 6b of the electronic component 6 The terminal electrode 6b and the land electrode 5b on the front surface side are soldered to each other. Note that, depending on the design of the wiring pattern 3 and the other conductive through hole 5, the other terminal electrode 6b may be connected to the front surface side land electrode 5b of the other conductive through hole 5. Further, the electronic component 6 may be similarly bonded to the wiring pattern 4 on the back surface side of the substrate 2.

By adopting the above-described joining structure of the conductive through hole 5 and the electronic component 6, as described above, the exclusive area for forming the wiring patterns 3 and 4 of the substrate 2 and the mounting of the electronic component 6 can be achieved. Therefore, the occupied area can be reduced, and high density of the circuit of the circuit board 1 can be achieved.

Further, as can be understood from the cross-sectional view of the joint portion in FIG. 3, the surface mounting type electronic component 6 solder S for electrical connection and mechanical joining is connected to the terminal electrode 6 b of the surface mounting type electronic component 6. Since the solder meniscus S ′ is formed by the surface tension of the melted solder between the terminal electrode 6b and the conductor film 5a orthogonal to the terminal electrode 6b as well as at the interface with the land electrode 5b, the mechanical joining of the electronic component 6 is particularly important. The strength is greatly improved.

The same is true for the land electrode 5b side, and even if a force for peeling the land electrode 5b from the substrate 2 due to heat or solder S acts in the solder reflow process, the land electrode 5b is not affected by this force. Since the conductor films 5a orthogonal to each other are integrated, peeling or the like does not occur, and the land electrode 5b and the conductor film 5a are stably maintained. By stabilizing the land electrode 5b and the conductor film 5a, the thick film circuit board 1 with high bonding reliability is obtained.

As a result of various conditions conducted by the present inventor, the land electrodes 5b and 5c have a shape corresponding to the shape of the terminal electrodes 6b and 6c of the electronic component 6, but the diameter of the through hole is It is desirable that the diameter is 100 to 800 μm within a range of at least not larger than this shape.

If the diameter is less than 100 μm, it becomes substantially difficult to perforate the circuit board 1. Even if a through hole having a diameter of less than 100 μm can be formed, the conductor film 5a is formed on the inner wall surface of the through hole. Therefore, when the conductive paste is printed, the opening portion of the through hole is closed, a disconnection occurs in the middle, and the conduction between the land electrodes 5b and 5c cannot be achieved.

Further, when the diameter exceeds 800 μm, even when the surface mount type electronic component 6 is soldered using the land electrode 5b, the melted solder S enters into the through hole by its own weight, and the surface mount type The solder meniscus S ′ for holding the electronic component 6 firmly and stably cannot be formed sufficiently, and conversely, the solder joint reliability of the surface-mounted electronic component 6 deteriorates.

As described above, according to the present invention, the density of the entire circuit of the thick film circuit board 1 in which the surface mount type electronic component 6 is structurally mounted on the circuit board 1 can be increased, and The solder joint strength between the terminal electrode of the component 6, for example 6b, and the conductive through hole 5, for example, the land electrode 5b, is improved, and the land electrode 5b and the conductor film 5a are not peeled off. It is possible to improve the sex.

In the above embodiment, the substrate 2 is made of single-plate ceramic or glass-epoxy, but it may be a multilayer ceramic substrate.

[0034]

[Effect of device]

 As described above, according to the present invention, the predetermined wiring patterns are formed on both main surfaces of the circuit board, and further, the surface mounting type electronic device is mounted on the land electrode around the opening of the conductive through hole for connecting both wiring patterns. Since the components are joined together, the formation of electrode pads to which the electronic components are joined can be omitted from the surface wiring pattern of the circuit board, so that it is possible to achieve high density of the entire circuit of the thick film circuit board.

Further, the surface mount type electronic parts are joined by cream solder application and reflow processing, so that a large number of electronic parts can be soldered together at the same time, and the solder is the terminal electrode and the land of the surface mount type electronic part. The bonding reliability is improved because the bonding is performed also at the interface with the electrode and the conductive film on the inner wall surface of the conductive through hole orthogonal to the bonding surface of the terminal electrode.

[Brief description of drawings]

FIG. 1 is a partial plan view of a thick film circuit board according to the present invention.

FIG. 2 is a partial cross-sectional view of a thick film circuit board according to the present invention.

FIG. 3 is an enlarged cross-sectional view of a joint portion of the thick film circuit board according to the present invention.

[Explanation of symbols]

 1 --- Thick film circuit board 2 --- Board 3 --- Front side wiring pattern 4 --- Back side wiring pattern 5 --- ... Conduction through hole 5a ... Conductor film on inner wall surface 5b ... Land electrode on front surface 5c ... Land electrode on back surface 6 ...・ ・ Electronic parts 6a ・ ・ Electronic parts body 6b, 6c ・ ・ ・ Terminal electrodes of electronic parts S ・ ・ ・ ・ Solder S '・ ・ ・ ・ ・ ・ Sensor meniscus

Claims (1)

[Scope of utility model registration request] 1. An electronic component having wiring patterns on both main surfaces of an insulating substrate, connecting both wiring patterns by a conductive through hole having a land electrode, and having a surface mountable terminal electrode on the insulating substrate. In the thick film circuit board, the terminal electrode of the electronic component is placed on the land electrode of the conductive through hole and solder-bonded.