JP2004235191A - Printed wiring board and electronic-part mounting substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printed wiring board in which the printing thickness of cream solder can further be equalized, and to provide an electronic-part mounting substrate. <P>SOLUTION: In the printed wiring board having a base material 2, a plurality of copper foils 3 formed on the material 2 low-layer resists 5 formed among the foils 3 and formed on the material 2, and high-layer resists 6 extended and formed from the resists 5 on the foils 3, and in which cream solder is printed on the specified foils 3 through the opening sections 15E, 15F and 15G of a metal mask 15, the resists 5 are coated with an insulating material 7 and the differences of the irregularities of the resists 6, and the resists 5 are reduced by the materials 7. Accordingly, since the differences of the heights of the opening sections of the metal mask are decreased, the thicknesses of cream solder printed on the exposure surfaces of the copper foils through the opening sections of the metal mask can further be equalized. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a printed wiring board on which cream solder is printed on a predetermined copper foil through an opening of a metal mask, and an electronic component mounting board provided with the same.
[0002]
[Prior art]
An example of this type of printed wiring board is disclosed in Japanese Patent Application Laid-Open No. 6-99568. FIG. 6 is a cross-sectional view of a principal part showing a state where cream solder is supplied to the printed wiring board disclosed therein through a metal mask. This has a substrate 2 and a plurality of copper foils 3 formed thereon, and a printed wiring on which a cream solder 10 is printed on a predetermined copper foil 3 through an opening of a metal mask 15. In the substrate, cream solder is performed using a metal mask 15 having divided openings 15A and 15B obtained by dividing an opening having a printing width exceeding 0.8 mm into a plurality of portions in the width direction.
[0003]
Since the opening having a printing width exceeding 0.8 mm is divided into the openings 15A and 15B, the squeegee used when squeezing the cream solder into the opening is less likely to bite into the opening. It can reduce the print blur of the cream solder.
[0004]
[Patent Document 1]
JP-A-6-99568
[Problems to be solved by the invention]
However, it has been found that when cream solder is supplied to the above-mentioned printed wiring board with fine copper foil, the printed thickness of cream solder varies. To explain this, as shown in FIG. 7, a printed wiring board is formed on a base material 2, a plurality of copper foils 3 formed thereon, and provided on the base material 2 provided between the copper foils 3. And a high-level resist 6 provided on the copper foil so as to extend from the low-level resist. A silk 10 is formed on these resists 5 and 6. Then, the metal mask 15 is brought into close contact with the printed wiring board, and the cream solder is squeezed into the openings 15E, 15F, and 15G with a squeegee from above, so that the metal mask 15 is deformed as shown in FIG. The heights of the portions were as indicated by H1, H2, and H3, and it was found that the difference in the height caused variations in the printed thickness of the cream solder.
[0006]
SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a printed wiring board and an electronic component mounting board capable of making the printed thickness of cream solder more uniform.
[0007]
[Means for Solving the Problems]
The printed wiring board of the invention according to claim 1 includes a base material, a plurality of copper foils formed thereon, a lower resist formed between the copper foils and formed on the base material, And a high-level resist provided extending from the low-level resist, and applying an insulating material to the low-level resist on a printed wiring board on which cream solder is printed on a predetermined copper foil through an opening of the metal mask. The insulating material reduces the difference in unevenness between the high-level resist and the low-level resist.
[0008]
A printed wiring board according to a second aspect of the present invention is characterized in that, in the first aspect, the insulating material is formed of silk.
[0009]
A printed wiring board according to a third aspect of the present invention is characterized in that, in the second aspect, the insulating material is formed of silk, and the silk is not extended over the high-level resist.
[0010]
According to a fourth aspect of the present invention, in the printed wiring board according to the first aspect, the insulating material is formed of an adhesive.
[0011]
According to a fifth aspect of the present invention, there is provided an electronic component mounting board comprising the printed wiring board according to any one of the first to fourth aspects, wherein the difference in the height of the high-level resist and the low-level resist of the printed wiring board is reduced. An electronic component is mounted on the part.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described with reference to FIG. FIG. 1 is a sectional view of a main part of a printed wiring board. It comprises a base material 2, a plurality of copper foils 3 formed thereon, a lower resist 5 provided between the copper foils 3 and formed on the base material 2, and a lower resist 5 formed on the copper foil 3. 5 is a printed wiring board having a high-level resist 6 provided so as to extend therefrom, and a cream solder printed on a predetermined copper foil 3 through an opening of a metal mask.
[0013]
The base material 2 is formed of a glass epoxy material, a paper phenol material, or the like. In FIG. 1, a copper foil 3 is formed on one side surface. The copper foil 3 has a coated surface covered with the high-level resist 6 and a bare surface that is not covered with the high-level resist 6, and cream solder is printed on the exposed surface. The resist includes a lower resist 5 provided between the copper foils 3 and formed on the base material 2 and a higher resist 6 provided on the copper foil 3 so as to extend from the lower resist 5. ing.
[0014]
What is important here is that the insulating material 7 is applied to the low-order resist 5, and the insulating material 7 reduces the difference in the unevenness between the high-order resist 6 and the low-order resist 5. More specifically, the insulating material 7 is formed by a silk 10 (silk map) used for display or the like, and the silk 10 is not extended on the high-level resist 6. Specifically, a silk having a thickness of about 20 μm is formed on the lower resist 5 so that the upper surface of the silk and the upper surface of the higher resist 6 have substantially the same height.
[0015]
When a metal mask is brought into close contact with the printed wiring board configured as described above, a cross-sectional view of a main part thereof is as shown in FIG. That is, the upper surface of the printed wiring board is in close contact with the lower surface of the metal mask 15, and the contact surface is substantially horizontal. In this state, when cream solder is squeezed into the openings 15E, 15F, and 15G from above the metal mask 15, the metal mask 15 does not bend as described with reference to FIG. The heights of the openings 15 are substantially the same as indicated by H1. Therefore, the thickness of the cream solder printed on the exposed surface of the copper foil 3 through the openings 15E, 15F, and 15G of the metal mask 15 is substantially the same.
[0016]
By bonding the electronic component to the cream solder, the electronic component can be borrowed, and the electronic component is less likely to be inclined and attached to the copper foil surface of the printed wiring board. The attachment process is easy to perform.
[0017]
According to this embodiment, the insulating material 7 is applied to the low-level resist 5, and the insulating material 7 reduces the unevenness between the high-level resist 6 and the low-level resist 5, so that the insulating material 7 is not provided. In comparison, the height of the opening of the metal mask 15 can reduce the difference in height as indicated by H1. Therefore, the thickness of the cream solder printed on the exposed surface of the copper foil 3 through the openings 15E, 15F, and 15G of the metal mask 15 can be made more uniform. In addition, since the insulating material 7 is formed of the silk 10, the insulating material 7 can be easily formed on the lower resist 5 without using a new material.
[0018]
Also, since the insulating material 7 is formed of the silk 10 and the silk 10 is not extended on the high-level resist 6, the electronic component can be brought closer to the exposed surface of the copper foil 3, so that the cream solder The thickness can be reduced, and thus the amount of cream solder used can be reduced.
[0019]
FIG. 3 shows an application example of this embodiment, and is a cross-sectional view of a main part of a printed wiring board. This application example has been described with reference to FIG. 1 except that the insulating material 7 is used as the adhesive 8. According to this application example, even in the case of a printed wiring board in which the unevenness between the high-level resist 6 and the low-level resist 5 already exists, the unevenness between the high-level resist 6 and the low-level resist 5 can be obtained by appropriately applying the adhesive 8. The difference can be reduced.
[0020]
Also, in an electronic component mounting board provided with a printed wiring board, a portion provided with the printed wiring board described with reference to FIG. 1 or FIG. 3, wherein a difference between the high-level resist and the low-level resist of the printed wiring board is reduced. By using an electronic component mounting board with electronic components mounted on it, unevenness between the electronic component and the printed wiring board is reduced, so that the electronic component can be mounted at an angle to the copper foil surface, The mounting can be performed without generating a portion that contacts the printed wiring board and a portion that does not contact the contact surface with the printed wiring board. In particular, when a substrate having a high heat dissipation property such as an alumina material is used as the base material of the printed wiring board, it is expected that the heat dissipation property can be expected when the electronic component is in uniform contact with the printed wiring board, and the electronic component described above is used. This is particularly useful because heat does not accumulate in places where it does not come into contact with the printed wiring board.
[0021]
(First Reference Example)
A first reference example will be described with reference to FIG. FIG. 4 is a sectional view of a main part of the printed wiring board. In this reference example, the projection 20 is provided substantially along the periphery of the exposed surface which is not covered with the high-level resist 6 of the copper foil 3 but is exposed as described with reference to FIG. In this case, since the thickness of the cream solder accumulated on the inner peripheral side of the convex portion 20 provided on the peripheral edge of the exposed surface can be increased, the cream solder having a thickness greater than the thickness of the metal mask 15 can be applied. The protrusions 20 may be provided as appropriate by applying an adhesive or the like.
[0022]
(Second reference example)
A second reference example will be described with reference to FIG. FIG. 5 is a perspective view in which electronic components are mounted on a printed wiring board. This reference example includes a substrate 2, a plurality of copper foils formed thereon, and a resist 50 provided between the copper foils and formed on the substrate 2.
[0023]
What is important here is that the copper foil is provided with a lead joint land 3a to which the lead portion A of the electronic component substantially contacts and a solder increasing land 3b extended therefrom. Then, the width of the copper foil is reduced at the boundary between the lead joint land 3a and the additional solder land 3b. The solder paste is printed on the additional land 3b by printing cream solder on the lead connection land 3a and the solder increase land 3b, mounting the lead A of the electronic component on the lead connection land 3a and soldering. Is attracted to the lead portion A side of the electronic component, that is, to the lead joining land 3a. Therefore, the amount of solder adhering to the lead portion A of the electronic component can be increased.
[0024]
【The invention's effect】
In the invention according to claim 1, a base material, a plurality of copper foils formed thereon, a low-level resist provided between the copper foils and formed on the base material, and a low-level resist formed on the copper foil. A high-level resist provided extending from the resist, and in a printed wiring board on which cream solder is printed on a predetermined copper foil through an opening of the metal mask, an insulating material is applied to the low-level resist. By using this insulating material, the difference in height between the high-level resist and the low-level resist is reduced, so that the difference in height between the openings of the metal mask is reduced. This makes it possible to make the thickness of the cream solder printed on the exposed surface more uniform.
[0025]
According to the second aspect of the present invention, since the insulating material is formed of silk, the effect described in the first aspect is exhibited, and the insulating material is formed on the lower resist without using a new material. Can be done.
[0026]
According to the third aspect of the present invention, the insulating material is formed of silk, and the silk is not extended on the high-level resist. Can be made closer to the exposed surface of the copper foil, so that the thickness of the cream solder can be reduced by that much, and hence the amount of the cream solder used can be reduced.
[0027]
According to the fourth aspect of the present invention, by forming the insulating material with an adhesive, the printed wiring board having the effects described in the first aspect and having the unevenness between the high-level resist and the low-level resist already exists. Even in this case, by appropriately applying the adhesive, the difference in the unevenness between the high-order resist and the low-order resist can be reduced.
[0028]
According to a fifth aspect of the present invention, there is provided the printed wiring board according to any one of the first to fourth aspects, wherein the printed wiring board is provided at a portion where the difference in the height of the high-level resist and the low-level resist is reduced. By mounting the electronic component, the effects described in Claims 1 to 4 are exhibited, and the unevenness between the electronic component and the printed wiring board is reduced. And a portion not contacting the printed wiring board on the contact surface between the substrate and the printed wiring board.
[Brief description of the drawings]
FIG. 1 is a sectional view of a principal part of a printed wiring board according to a first embodiment of the present invention.
FIG. 2 is a cross-sectional view of a main part when a metal mask is brought into close contact with the printed wiring board.
FIG. 3 is a diagram showing an application example of the above printed wiring board, and is a cross-sectional view of a main part of the printed wiring board.
FIG. 4 is a diagram showing a first reference example of the printed wiring board, and is a cross-sectional view of a main part of the printed wiring board.
FIG. 5 is a diagram showing a second reference example of the printed wiring board, and is a cross-sectional view of a main part of the printed wiring board.
FIG. 6 is a cross-sectional view of a principal part showing a state in which cream solder is supplied onto the printed wiring board via a metal mask on the printed wiring board according to the conventional example. It is principal part sectional drawing of.
[Explanation of symbols]
2 Base material 3 Copper foil 4 Seed 5 Low resist 6 High resist 7 Insulating material 10 Silk 15 Metal mask 15E Opening 15F Opening 15G Opening

Claims (5)

A base material, a plurality of copper foils formed thereon, a lower resist formed on the base material provided between the copper foils, and a higher resist provided extending from the lower resist on the copper foils In a printed wiring board on which cream solder is printed on a predetermined copper foil through an opening of a metal mask, an insulating material is applied to the lower resist, and the insulating material allows the higher resist and the A printed wiring board characterized in that the difference in unevenness from a lower resist is reduced. The printed wiring board according to claim 1, wherein the insulating material is formed of silk. 3. The printed wiring board according to claim 2, wherein the insulating material is formed of silk, and the silk is not extended on the high-level resist. The printed wiring board according to claim 1, wherein the insulating material is formed by an adhesive. 5. An electronic device comprising: the printed wiring board according to claim 1; and an electronic component mounted on a portion of the printed wiring board in which a difference in height between a high-level resist and a low-level resist is reduced. Component mounting board.

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