JPH10163261A - Manufacture of electronic component mounting wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the welded parts between a wiring board and an electronic component from being broken easily, even if a thermal stress, etc., are applied between both. SOLUTION: Along with attaching solder layers 3 to parts of the top surface of each of a plurality of wiring conductors 2 formed on an insulating substrate 1, an isolation band 4 having a thickness appraximately equal to the sum of the thicknesses of a wiring conductor 2 and a solder layer 3 is provide between each wiring conductor and the next on the top surface of the above-mentioned insulating board. Next, an electronic component 7 with a plurality of terminal electrodes 7a having areas smaller than the solder layers 3 is put on the insulating board 1, so that each terminal electrode 7a may touch a part of a solder layer 3. Next, the exposed region of the solder layer 3 brought into contact with the terminal electrode 7a of the electronic component 7 is covered with flow-out preventing material 8 having a thermal decomposition temperature higher than the melting temperature of the solder layer 3. And the solder layers 3 are heated and melted, and the terminal electrodes 7a of the electronic component 7 are joined with solder to the wiring conductors 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a wiring board for mounting electronic components on which electronic components such as a light emitting diode array and an LSI are mounted by a flip chip method.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 5, a wiring board on which electronic components such as a light emitting diode array and an LSI are mounted is formed on an upper surface of an insulating substrate 11 made of alumina ceramics or glass. And a plurality of wiring conductors 12 each having a predetermined thickness and a predetermined pattern are attached and formed, and a solder layer 13 having a predetermined thickness is attached on a partial upper surface of the wiring conductors 12 by screen printing or the like. The solder layer 13 is heated and melted at a high temperature in a state where the terminal electrode 15 of the electronic component 14 is in contact with the solder layer 13 of the wiring board, and the terminal electrode 15 of the electronic component 14 is connected to the wiring conductor 12. The electronic component 14 is mounted on the wiring board by soldering.

However, in this conventional wiring board, the arrangement density of the wiring conductors 12 is high (for example, 10
0 μm or less), the solder layer 1
When the solder 3 was heated and melted, the melted solder 13 spread laterally due to its surface tension, the weight of the electronic component 14, and the like. In order to solve the above-mentioned drawbacks, the inventors of the present invention provided a separator between each of the wiring conductors 12 on the insulating substrate 11 and having a thickness substantially equal to the total thickness of the wiring conductors 12 and the solder layers 13. It has been proposed to prevent the molten solder 13 from being spread laterally by the band (see Japanese Patent Application No. 8-166243).

However, in recent years, electronic components such as light-emitting diode arrays and LSIs have tended to be gradually reduced in size in order to respond to the demand for downsizing, and accordingly, the area of terminal electrodes and solder layers of the electronic components has become extremely small. It has become to. In this case, since the terminal electrodes of the electronic component are joined to the wiring conductor by a very small amount of solder, sufficient mechanical strength cannot be given to the solder joint, and thermal stress or the like between the wiring board and the electronic component cannot be provided. Is applied, this leads to the disadvantage that the solder joints are easily broken.

[0005]

SUMMARY OF THE INVENTION The present invention has been devised in view of the above-mentioned drawbacks, and a method of manufacturing a wiring board for mounting electronic components according to the present invention is directed to a method for manufacturing a plurality of wiring conductors formed on an insulating substrate. Disposing a solder layer on each partial upper surface and disposing a separator between the wiring conductors on the upper surface of the insulating substrate and having a thickness substantially equal to the total thickness of the wiring conductor and the solder layer; A step of placing an electronic component on which a plurality of terminal electrodes having an area smaller than the layer is formed on an insulating substrate so that each terminal electrode is in contact with a part of the solder layer,
Covering the exposed area of the solder layer with which the terminal electrode of the electronic component is in contact with an outflow prevention material having a higher thermal decomposition temperature than the melting temperature of the solder layer; and heating and melting the solder layer. And bonding a terminal electrode of the electronic component to the wiring conductor by soldering.

According to the method of manufacturing a wiring board for mounting electronic components of the present invention, a solder layer is applied to a partial upper surface of each of a plurality of wiring conductors formed on an insulating substrate, and the upper surface of the solder layer is formed. And applying an outflow prevention film having a thermal decomposition temperature higher than the melting temperature of the solder layer and having a window for exposing a part of each solder layer on the upper surface of the insulating substrate located between the wiring conductors. The electronic component having a plurality of terminal electrodes having substantially the same area as the window portion of the outflow prevention film is placed on an insulating substrate, and each terminal electrode is brought into contact with a solder layer in the window portion of the outflow prevention film. And heating and melting the solder layer, and soldering the terminal electrode of the electronic component to the wiring conductor.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. (First Embodiment) First, a first embodiment of the manufacturing method of the present invention will be described. FIG. 1 is a partial plan view of a wiring board for mounting electronic components manufactured according to a first embodiment of the manufacturing method of the present invention, FIG. 2 (a) is a cross-sectional view taken along line XX of FIG. 1, and FIG. FIG. 2 is a cross-sectional view taken along the line YY, where 1 is an insulating substrate, 2 is a wiring conductor, 3 is a solder layer,
Reference numeral 4 denotes a separator, 7 denotes an electronic component, 7a denotes a terminal electrode, and 8 denotes an outflow preventing material.

The insulating substrate 1 is made of, for example, borosilicate glass, soda lime glass, alumina ceramics or the like having a thickness of about 1 mm, and has a plurality of wiring conductors 2, a solder layer 3, a separation band 4, etc. on its upper surface. Has come to support.

The plurality of wiring conductors 2 attached on the upper surface of the insulating substrate 1 are arranged at a high density (for example, at a pitch of 100 μm or less) at a predetermined interval from adjacent wiring conductors 2. They are arranged and formed with a thickness of 3 to 20 μm using a metal such as Ag, Cu, or Au.

The wiring conductor 2 is electrically connected to a terminal electrode 7a of an electronic component 7 via a solder layer 3 attached to a part of the upper surface of the wiring conductor 2, thereby providing the electronic component 7 with driving power and various electric power. It supplies signals and the like.

The solder layer 3 applied to a part of the upper surface of the wiring conductor 2 is connected to a terminal electrode 7 of an electronic component 7 described later.
a to be solder-bonded to the wiring conductor 2, and one end of each of the plurality of wiring conductors 2 has a substantially constant thickness (5 to 30 μm).
m).

A separation band 4 having a thickness substantially equal to the total thickness of the wiring conductor 2 and the solder layer 3 is provided between the wiring conductors 2 on the upper surface of the insulating substrate.

The separator 4 is made of an electrical insulating material having poor solder wettability, for example, glass, thermoplastic resin, etc., and has a height substantially equal to the sum of the thicknesses of the wiring conductor 2 and the solder layer 3 between the adjacent solder layers 3. When the solder layer 3 is heated and melted (solder reflow) when mounting an electronic component 7 to be described later on the insulating substrate 1, the molten solder 3 has a surface tension and a surface tension of the electronic component 7. The separation band 4 can effectively prevent an attempt to cause a short circuit with the adjacent solder layer 3 due to weight or the like.

At a predetermined position on the upper surface of the insulating substrate 1, an electronic component 7 such as a light emitting diode array or an LSI is mounted in a flip-chip manner.

On the lower surface of the electronic component 7, a plurality of terminal electrodes 7a having an area smaller than that of the solder layer 3 are formed, and the lower surfaces of these terminal electrodes 7a are partially covered on the upper surface of the solder layer 3. The terminal electrode 7a of the electronic component 7 is electrically connected to the wiring conductor 2 via the solder layer 3 by being attached.

As described above, the terminal electrode 7 of the electronic component 7
The reason why the area of “a” is made smaller than that of the solder layer 3 is to secure a sufficient amount of solder for firmly joining the terminal electrode 7 a to the wiring conductor 2 by soldering. Damage to the solder joints when thermal stress or the like is applied between the electronic component 1 and the electronic component 7 can be effectively prevented.

Further, on the upper surface of the solder layer 3 with which the terminal electrode 7a is in contact, an outflow preventing material 8 is applied in a region other than the contact portion.

When the solder layer 3 is heated and melted (solder reflow) when the electronic component 7 is mounted on the insulating substrate 1, the outflow preventing material 8 surrounds the melted solder 3 by the separation band 4 or the like. It is formed of an electrically insulating material having a thermal decomposition temperature higher than the melting temperature of the solder layer 3, for example, resin, wax, rubber, or the like, which acts as a lid to prevent the solder layer from flowing out.

Next, a method of manufacturing the above-described wiring board for mounting electronic components will be described with reference to FIG. (1) First, as shown in FIG. 3A, a solder layer 3 is applied to a partial upper surface of each of a plurality of wiring conductors 2 formed on an insulating substrate 1 and an upper surface of the insulating substrate 1 is formed. A separator 4 having a thickness substantially equal to the total thickness of the wiring conductor 2 and the solder layer 3 is provided between the wiring conductors 2.

The wiring conductor 2 is formed, for example, by applying a conventionally known screen printing or the like to the upper surface of the insulating substrate 1 by using a silver paste obtained by adding and mixing an appropriate organic solvent, an organic solvent and the like to silver powder. A predetermined pattern having a thickness (3 to 20 μm) and a predetermined pattern are printed and applied. Thereafter, the resultant is baked at a temperature of about 580 ° C. to be formed on the insulating substrate 1.

After forming the wiring conductor 2 as described above, the separation band 4 is covered with a predetermined thickness and a predetermined pattern by employing a conventionally known thick film technique, a photolithography technique (lift-off method) or the like. Weared and formed. Specifically, first, a liquid-cured resin precursor formed in a liquid state is applied to a predetermined region on the upper surface of the insulating substrate 1 to a predetermined thickness by a screen printing method, a spin coating method, or the like. Exposure and development are performed in accordance with the reverse pattern of No. 4, and thereafter, a glass paste is applied and baked over the region on the upper surface of the insulating substrate on which the electronic component 7 is mounted, and finally the photocured resin is deposited thereon. Separation band 4 made of glass is adhered and formed in a predetermined pattern by peeling off the glass together with the glass. In this case, since the separation zone 4 is formed of glass having a relatively low thermal conductivity,
The heat applied from the outside during the solder reflow described later is well accumulated in the separation zone 4, and the solder reflow can be efficiently performed in a short time.

The above-mentioned solder layer 3 can be formed very simply by forming a separation band 4 as described above and then employing a conventionally well-known dipping method or the like. That is, the solder is selectively adhered to the surface of the wiring conductor 2 by immersing the insulating substrate 1 on which the wiring conductor 2 and the separation band 4 are formed on the upper surface as it is in a solder bath. Will be formed. When the solder layer 3 is formed by such a dipping method, the solder resist layer 5 must be previously applied to a region where solder is not to be attached.

(2) Next, as shown in FIG. 3B, an electronic component 7 having a plurality of terminal electrodes 7a having an area smaller than that of the solder layer 3 is placed on the insulating substrate 1 and each terminal electrode 7a Is placed in contact with a part of the solder layer 3.

For example, when the area of the solder layer 3 is 7.0 × 10 ⁻³ mm ² , the terminal electrode 7a of the electronic component 7 is 3.2 × 1
0 ^-3 mm ² , and by making the solder layer 3 larger than the terminal electrode 7a,
The terminal electrode 7a is connected to the wiring conductor 2 at the time of solder reflow described later.
In this case, it is possible to secure a sufficient amount of solder for making a strong solder joint.

(3) Subsequently, as shown in FIG. 3 (c), the exposed region of the solder layer 3 where the terminal electrode 7a of the electronic component 7 is in contact is heated to a temperature higher than the melting temperature of the solder layer 3. It is covered with an outflow prevention material 8 having a decomposition temperature.

When the melting temperature of the solder layer 3 is 180.degree. C., for example, when the melting temperature of the solder layer 3 is 180.degree. It is made of various resin materials such as high epoxy resin, polyimide resin, and acrylic resin, various wax materials such as carnauba wax, montan wax, and candelilla wax, and rubber materials such as nitrile rubber and silicone rubber. When using a photocurable resin, a precursor of the photocurable resin is applied in a band shape with a thickness of about 100 to 300 μm to a region where the solder layer 3 is exposed using a dispenser or the like, and a UV lamp or the like is applied to the precursor. It is formed by irradiating light and curing the light.

When a thermosetting resin is used as the outflow preventing material 8 in place of the photocurable resin, it is not necessary to cure the resin in this step. It may be cured at the same time.

(4) Finally, the solder layer 3 is heated and melted, and the terminal electrode 7a of the electronic component 7 is joined to the wiring conductor 2 by soldering.

The solder layer 3 is subjected to solder reflow in a furnace set at a temperature sufficiently lower than the thermal decomposition temperature of the outflow prevention member 8 (for example, 200 to 250 ° C.). The conductor 2 and the terminal electrode 7a of the electronic component 7 are electrically and mechanically connected by the flip chip method.

In this case, the area of the solder layer 3 is formed sufficiently larger than the terminal electrode 7a of the electronic component 7, and even if the electronic component 7 is extremely small, the area of the terminal electrode 7a and the wiring conductor 2 is small. Can be firmly joined by more solder 3, so that even if a thermal stress or the like is applied between the insulating substrate 1 and the electronic component 7, the solder joint between the two is not easily broken, and The component mounting wiring board can function well for a long period of time.

Further, since the exposed area of the solder layer 3 is covered with the outflow preventing material 8 having a higher thermal decomposition temperature than the melting temperature of the solder 3, the molten solder 3 at the time of the solder reflow has An outflow preventing member 8 effectively prevents the outflow from the region surrounded by the separation band 4 or the like due to tension or the like, and the mounting operation of the electronic component 7 can be performed more reliably.

(Second Embodiment) Next, a second embodiment of the manufacturing method of the present invention will be described. FIGS. 4A and 4B are cross-sectional views of an electronic component mounting wiring board manufactured by the second embodiment of the manufacturing method of the present invention, where 9 denotes a flow-out preventing film, and 9a denotes a window.
It should be noted that the division diagrams (a) and (b) of FIG.
The same reference numerals are given to the same components as those of the above-described first embodiment, and redundant description will be omitted.

The wiring board for mounting electronic components shown in FIG.
The difference from the one manufactured according to the embodiment is that the outflow prevention film 9 having a plurality of windows 9a is used instead of the separation band 4 and the outflow prevention material 8 used in the first embodiment.

The outflow prevention film 9 is formed of an electrically insulating material having a thermal decomposition temperature higher than the melting temperature of the solder layer 3, for example, an epoxy resin or an acrylic resin. It is interposed between the insulating substrate 1 and the electronic component 7 so as to be located above.

The terminal electrode 7a of the electronic component 7 has an area substantially equal to the window 9a of the outflow prevention film 9.
The terminal electrode 7a is connected to the solder layer 3 in the window 9a of the outflow prevention film 9.
To the terminal electrodes 7 of the electronic component 7.
a is electrically connected to the wiring conductor 2 via the solder layer 3.

Then, the above-mentioned wiring board for mounting electronic components is manufactured according to the following procedures (1) to (4). (1) First, an insulating substrate 1 on which a plurality of wiring conductors 2 are formed
Is prepared, and a solder layer 3 is applied to a partial upper surface of each of the wiring conductors 2 on the insulating substrate 1.

(2) Next, the upper surface of the solder layer 3 and the upper surface of the insulating substrate 1 located between the wiring conductors 2 have a thermal decomposition temperature higher than the melting temperature of the solder layer 3 and each solder layer 3
The outflow prevention film 9 having the window 9a for exposing a part of the film is applied.

When the outflow prevention film 9 is made of, for example, a photo-curable epoxy resin, a window portion 9a is formed on each solder layer 3 by a conventionally known screen printing method or the like using a precursor of the resin. Then, the precursor is printed and applied with a predetermined thickness, and then the precursor is irradiated with ultraviolet rays using a UV lamp, and the precursor is photo-cured to form the precursor. At this time, the thickness of the outflow prevention film 9 must be substantially equal to or smaller than the thickness of the terminal electrode 7a of the electronic component 7.

(3) Subsequently, the window 9a of the outflow prevention film 9
An electronic component 7 having a plurality of terminal electrodes 7a having substantially the same area as the electronic component 7 is mounted on the insulating substrate 1 such that each terminal electrode 7a is in contact with the solder layer 3 in the window 9a of the outflow prevention film 9. Place.

(4) Finally, the solder layer 3 is heated and melted at a predetermined temperature, and the terminal electrodes 7 of the electronic component 7 are joined to the wiring conductor 2 by soldering, thereby completing the electronic component mounting wiring board.

According to the manufacturing method of the second embodiment, the area of the solder layer 3 is formed sufficiently larger than the terminal electrode 7a of the electronic component 7, and even if the electronic component 7 is extremely small, Since the terminal electrode 7a and the wiring conductor 2 can be firmly joined by more solder 3,
Even when thermal stress or the like is applied between the insulating substrate 1 and the electronic component 7, the solder joints of the two are not easily broken, and the electronic component mounting wiring board can function well for a long period of time. .

The entire area of the surface of the solder layer 3 except for the area where the terminal electrode 7a is in contact is covered with the outflow prevention film 9 having a thermal decomposition temperature higher than the melting temperature of the solder layer 3. Therefore, the solder 3 melted at the time of solder reflow does not spread laterally due to surface tension or the like or flows out, and the mounting work of the electronic component 7 can be reliably performed.

The present invention is not limited to the above-described embodiment, and various changes and improvements can be made without departing from the gist of the present invention.

[0044]

According to the present invention, the area of the solder layer can be formed sufficiently larger than the terminal electrode of the electronic component.
Even if the electronic component is extremely small, the terminal electrode and the wiring conductor can be firmly joined with more solder. Therefore, even when thermal stress or the like is applied between the insulating substrate and the electronic component, the solder joints of the two are not easily damaged, and the electronic component mounting wiring board can function well for a long period of time. .

According to the present invention, the exposed surface of the solder layer is covered with the outflow prevention material or the outflow prevention film having a thermal decomposition temperature higher than the melting temperature of the solder. The molten solder does not leak out, and the mounting operation of the electronic component can be performed reliably.

[Brief description of the drawings]

FIG. 1 is a partial plan view of an electronic component mounting wiring board manufactured by a first embodiment of a manufacturing method of the present invention.

2A is a cross-sectional view taken along line XX of FIG. 1, and FIG.
5 is a sectional view taken along line YY of FIG.

3 (a) to 3 (c) are cross-sectional views for respective steps showing one embodiment of the manufacturing method of the present invention.

FIGS. 4A and 4B are cross-sectional views of an electronic component mounting wiring board manufactured by a second embodiment of the manufacturing method of the present invention.

FIG. 5 is a partial sectional view of a conventional wiring board for mounting electronic components.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Insulating board 2 ... Wiring conductor 3 ... Solder layer 4 ... Separation band 7 ... Electronic component 7a ... Terminal electrode 8 ... Outflow prevention material 9 ... Outflow prevention film 9a ..Windows

Claims (2)

[Claims] 1. A solder layer is applied to a partial upper surface of each of a plurality of wiring conductors formed on an insulating substrate, and the total thickness of the wiring conductor and the solder layer is provided between the respective wiring conductors on the insulating substrate upper surface. Arranging a separation band having substantially the same thickness with respect to the electronic component on which a plurality of terminal electrodes having an area smaller than the solder layer are formed on an insulating substrate; each terminal electrode being part of the solder layer; And mounting the exposed part of the solder layer to which the terminal electrode of the electronic component is abutted with an outflow prevention material having a thermal decomposition temperature higher than the melting temperature of the solder layer. And a step of heating and melting the solder layer, and soldering a terminal electrode of the electronic component to the wiring conductor by soldering. 2. A method according to claim 1, further comprising: applying a solder layer to a part of an upper surface of each of the plurality of wiring conductors formed on the insulating substrate;
Having a thermal decomposition temperature higher than the melting temperature of the solder layer, and applying an outflow prevention film having a window for exposing a part of each solder layer; and Placing an electronic component having a plurality of terminal electrodes of equal area on an insulating substrate such that each terminal electrode is in contact with a solder layer in a window of the outflow prevention film; and heating the solder layer. A method of melting and causing a terminal electrode of the electronic component to be solder-bonded to the wiring conductor.