JPH06350230A - Printed wiring board and production thereof - Google Patents

Abstract

PURPOSE:To deal with the miniaturization of electronic component by forming a dielectric film between the electrodes formed on a printed wiring board through lamination of patterns having width decreasing toward the upper layer thereby preventing solder bridge without sacrifice of solderability. CONSTITUTION:Wiring patterns 5 and electrodes 2 are formed of a copper foil on the surface of a board body 1 and then a dielectric film layer 3 is formed thereon except the electrode parts 2 which are connected with the lead terminals of an electronic component. The dielectric film layer 3 is formed by screen printing of an epoxy resin resist ink, for example. After curing the dielectric film layer 3, second time screen printing is conducted while superposing a narrow insulation pattern detouring the electrode parts 2 on the underlying dielectric film layer 3 thus forming an upper dielectric film layer 4. A plurality of insulation layer patterns are formed with the width decreasing toward the upper layer. This structure widens the allowable range of shift and prevents the upper dielectric film layer 4 from adhering to the electrode 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed wiring board which prevents short-circuiting of semiconductor parts, chip parts, etc. by solder bridges when the parts are soldered and mounted on the printed wiring board, and a method of manufacturing the same. .

[0002]

2. Description of the Related Art Conventionally, as a structure of a printed wiring board of this type, there has been one as shown in FIG. In FIG. 4, 1 is a substrate body made of an insulating material such as phenol resin or epoxy resin, 2 and 5 are electrodes and wiring patterns formed of copper foil on the surface of the substrate body 1, and 3 are lead wires of electronic parts. The electrode portion 2 to be connected is left and the other portion is covered with a resist ink such as an epoxy resin by a method such as screen printing to be insulated from the outside by a so-called solder resist.

The lead terminals of the electronic component are placed so as to correspond to the electrodes formed on the substrate, and in this state, the lead terminals and the electrodes are soldered. As a result, they are electrically connected and mechanically fixed.

[0004]

In the conventional structure shown in FIG. 4, due to the miniaturization and high-density mounting of electronic components, when the lead terminals of the electronic components are closely spaced, for example, the spacing between adjacent electrodes 2 is 0.25 mm. In the case of being formed in a certain degree, when soldering, there is a drawback in that the solder flows into another adjacent electrode portion in a melted state and solidifies to cause a short circuit, resulting in a so-called solder bridge.

That is, as shown in FIG. 4B, conventionally, since the thickness of the electrode pattern 2 and the thickness of the resist 3 are substantially the same, solder bridges are likely to occur. Therefore, by providing a thicker resist around the electrode 2, the inflow and outflow of solder can be prevented, and the occurrence of solder bridges can be prevented. However, it is technically difficult to obtain a sufficient thickness with one screen printing. Therefore, a method is known in which the same resist pattern is repeatedly screen-printed to obtain a sufficient thickness by forming the resist in multiple layers. However, as described above, the distance between the adjacent electrodes 2 is 0.
When it is formed with a thickness of about 25 mm, the distance between the lower resist 3 and the adjacent electrode 2 is about 50 μm as shown in FIG. 4, so that when the screen printing is repeated, the resist ink bleeds or shifts, and There is a possibility that the resist 4 may adhere to the adjacent electrode 2 and deteriorate the solderability.

An object of the present invention is to provide a thicker resist or the like around the electrodes with high accuracy to prevent the occurrence of solder bridges without deteriorating the solderability, and to correspond to miniaturized electronic parts. And

[0007]

In order to solve the above problems, the present invention provides a printed wiring board on which an electronic component is mounted by soldering, an insulating film formed between electrodes of the printed wiring board being used as an upper layer. It is characterized in that the layers are formed as a pattern having a narrower width. Also, in a printed wiring board on which electronic components are mounted by soldering,
It is characterized in that a resist formed by printing between electrodes of the printed wiring board is formed by printing by superimposing it as a resist pattern having a narrower width in an upper layer.

Further, in the printed wiring board on which the electronic parts are mounted by soldering, an insulating material stuck between the electrodes of the printed wiring board is processed into a film shape to form a film pattern having a narrower width toward the upper layer. It is characterized in that they are attached in layers. Further, the printed wiring board is characterized in that a resist pattern and a film pattern, which are narrower in width toward the upper layer between electrodes, are combined and formed in layers.

Further, an insulating film such as a resist or an insulating film is laminated on at least a predetermined electrode and a surface between the electrodes of a printed wiring board on which electrodes are printed and formed.
It is characterized in that the insulating film on the electrode portion requiring soldering is irradiated with laser light to be removed, and the electrode portion is exposed.

[0010]

In the printed wiring board on which the electronic component is mounted by soldering, the insulating film formed between the electrodes of the printed wiring board is laminated in a pattern having a narrower width in the upper layer. Since the width is narrow, the allowable range of misalignment is increased, the upper insulating film can be prevented from adhering to the adjacent electrode, and a thicker insulating film layer can be accurately formed.

As the insulating film, for example, a resist formed by printing can be used. By forming the resist pattern by overlapping and forming a resist pattern having a narrower width in the upper layer, a thicker insulating film layer can be accurately formed as described above. Can be formed. Further, similar to the print formation in this case, when a film-shaped insulating material stuck between the electrodes of the printed wiring board is used, the cut surface of the portion cut out corresponding to the electrodes in the thick film is used. Since the accuracy of is poor, use thin films on top of each other.

However, as in the case of the resist, a deviation occurs and adheres to an adjacent electrode. Therefore, by adhering a film pattern having a narrower width to the upper layer and adhering it to the wiring board, the deviation allowable range is increased. Therefore, it is possible to prevent the upper film from adhering to the adjacent electrodes, and to form a thicker film layer. Further, when the film is pasted and formed, there is no fear of dripping or bleeding as compared with the case where the resist is screen-printed, so that the processing can be performed with higher accuracy and the reliability is further improved.

In the printed wiring board, by combining a film as a lower layer and a resist as an upper layer or vice versa, it is possible to form a layered wall having characteristics of respective materials. At least a predetermined electrode in the printed wiring board and a surface between the electrodes, a resist, an insulating film such as an insulating film is laminated, and then only the insulating film on the electrode portion that needs to be soldered is removed by irradiating laser light, When the electrode portion is formed by being exposed by post-processing, since the insulating film is removed by using laser light, it is easy to perform fine processing with high accuracy and there is no need to make the upper layer thin. It is possible to form a wall of a stack of thicker insulating films, and it is possible to adapt to a position where electrodes are more adjacent.

[0014]

FIG. 1 shows an embodiment of the present invention. Figure 1 (a)
Shows a plan view, and (b) shows a sectional view taken along line AA '. The wiring pattern 5 and the electrodes 2 are formed on the surface of the substrate body 1 with a copper foil, the electrode portions 2 connected to the lead terminals of the electronic component are left, and the other portions are covered with the insulating film layer 3. The insulating film layer 3 is formed by screen printing with a resist ink of an epoxy resin by a screen printing method, for example. After the insulating film layer 3 is cured, an insulating film pattern having a narrow width that avoids the vicinity of the electrodes is overlapped on the lower insulating film layer 3 as shown in FIG. 1A, and the second screen printing is performed, for example. , The upper insulating film layer 4 is formed. In this manner, a plurality of layers of insulating film patterns are formed, the width of which is narrower toward the upper layer. According to the present embodiment, the width of the upper insulating film layer 4 is smaller than the width of the lower insulating film layer 3 between the adjacent electrodes, so that the allowable range of deviation increases as shown in FIG. As a result, the upper insulating film 4 can be prevented from adhering to the adjacent electrode 2, and a thicker insulating film layer can be accurately formed.

Further, as the insulating film layers 3 and 4, a film made of an insulating material may be used instead of the resist. In this case, since the precision of the cut surface of the thick film corresponding to the electrode is poor, thin films are stacked. However, as in the case of the above-mentioned resist, a shift may occur due to stacking, and an upper layer film may be attached to an adjacent electrode. Similarly, as the upper layer is stacked, a film pattern having a narrower width is stacked and stuck to a wiring board. By increasing the allowable range of the above, it is possible to prevent the upper layer film from adhering to the adjacent electrodes, and it is possible to accurately form a thicker film layer.

Further, the lower insulating film 3 closer to the electrode 2
By attaching a film that can be processed with high precision as the upper layer, using a resist having higher productivity than the film as the upper insulating film 4, and forming a resist pattern having a width narrower than the film pattern, high precision and productivity can be obtained. Can be compatible. FIG. 3 is an embodiment showing a method for manufacturing a printed wiring board according to the present invention. Such a manufacturing method is for a substrate body
The entire surface of the printed wiring board on which the wiring pattern and the electrodes 12 are formed by printing with a copper foil on the surface of 11 is laminated and covered, and only the insulating film 13 on the predetermined electrode portion 12 is irradiated with the laser beam 16. And then removed to expose the electrode portion. According to the present embodiment, since the insulating film 13 is removed by using the laser beam 16, fine processing can be performed with high accuracy regardless of the thickness of the stacked insulating film 3, and a thicker stacked insulating film 3 can be obtained. Moreover, since it is not necessary to make the upper layer thin, it is possible to adapt to a position where the electrode 2 is adjacent.

In the present embodiment, as a method of removing the insulating film 13 on the electrode portion 12 that needs to be soldered, conventionally, a photosensitive insulating film is formed on the entire surface of the substrate on which the wiring pattern and the electrode 12 are formed by printing. The film is thermocompression-bonded, and light is applied to necessary portions of the insulating film such as between electrodes by a photographic method to cure the insulating film by photosensitization, and then the insulating film on the electrode part 12 not exposed to the solvent is removed. There is a method of exposing the electrode portion 12 by removing it. In this method, it is extremely difficult to form the cross section of the insulating film removed by the solvent as a vertical flat surface, and the processing accuracy is poor, so that it is not suitable for forming a pattern of a stacked thick insulating film.

[0018]

As described in detail above, according to the present invention, by providing a thicker resist or the like around the electrodes, it is possible to prevent the occurrence of solder bridges without deteriorating the solderability, and to reduce the size. It becomes possible to deal with the electronic parts that are becoming more and more popular.

[Brief description of drawings]

FIG. 1 is a plan view and a sectional view of a printed wiring board showing an embodiment of the present invention.

FIG. 2 is a substrate cross-sectional view for explaining the effect of the present invention.

FIG. 3 is a sectional view of a board showing an embodiment of a method for manufacturing a printed wiring board according to the present invention.

FIG. 4 is a plan view and a sectional view of a conventional printed wiring board.

FIG. 5 is a sectional view of a substrate showing a conventional problem.

[Explanation of Codes] 1 ... Substrate body 2 ... Electrode 3 ... Insulating film layer (resist layer, film layer, etc.) 4 ... Insulating film layer (resist layer, film layer, etc.) 5 ... Wiring pattern 16 ... Laser light

Claims (5)

[Claims] 1. A printed wiring board on which an electronic component is mounted by soldering, wherein an insulating film formed between electrodes of the printed wiring board is laminated and formed as a pattern having a width narrower toward an upper layer. Wiring board. 2. A printed wiring board on which electronic components are mounted by soldering, wherein a resist formed by printing between electrodes of the printed wiring board is printed and formed as a resist pattern having a width narrower toward an upper layer. Characterized printed wiring board. 3. A printed wiring board on which electronic parts are mounted by soldering, wherein an insulating material stuck between electrodes of the printed wiring board is processed into a film shape and laminated as a film pattern having a narrower width toward an upper layer. A printed wiring board, which is formed by pasting on a wiring board. 4. The printed wiring board according to claim 2 or 3, wherein a resist pattern and a film pattern each having a width narrower in an upper layer between the electrodes are combined and formed in combination. 5. An insulating film such as a resist or an insulating film is laminated on at least a predetermined electrode and a surface between the electrodes of a printed wiring board on which electrodes are printed, and then the insulation on the electrode portion that needs to be soldered. A method for manufacturing a printed wiring board, characterized in that the film is formed by irradiating the film with laser light to expose the electrode portion.