JP4357792B2 - Method for manufacturing printed wiring board - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a printed wiring board used in various electronic devices such as a personal computer, a mobile communication telephone, and a video camera.
[0002]
[Prior art]
In recent years, as electronic devices have higher functions and higher densities, electronic components are increasingly becoming smaller, more integrated, and faster.
[0003]
For this reason, the printed wiring board is also increasingly in the trend of low dielectric constant, thinness, light weight and high density, and improvement of various precisions in products and production processes is required.
[0004]
In particular, in electrostatic coating, which is one of the methods for forming a photographic process for a printed wiring board, improvement in the accuracy of the applied film thickness has been required.
[0005]
Hereinafter, electrostatic coating in a conventional method for producing a printed wiring board will be described.
[0006]
FIG. 7 is a diagram showing a configuration of a conventional electrostatic coating method for a printed wiring board. In this configuration, a coating film is formed in the following order (the process flow is not shown).
[0007]
(1) A printed wiring board 11 on which a circuit pattern is formed is prepared.
[0008]
(2) The printed wiring board is fixed to the conveyance unit 12 maintained in the ground (0 V) state, and the entire surface of the printed wiring board is grounded.
[0009]
(3) The solder resist ink 13 charged with a charge opposite to that of the printed wiring board is discharged through the spray gun 14.
[0010]
(4) The solder resist ink 13 is applied to the entire surface of the printed wiring board 11 by electrostatic attraction generated by electric lines of force generated between the opposite charges in addition to the spraying force of the spray.
[0011]
(5) The applied solder resist ink is dried by touch with hot air at 80 ° C. for about 20 minutes.
[0012]
(6) Then, it exposes by ultraviolet irradiation through the film for exposure, etc., an unexposed part is melt | dissolved and removed with a developing solution, and it hardens by heat processing for about 30 minutes at 130 degreeC, and completes a solder resist.
[0013]
[Problems to be solved by the invention]
The formation density of the circuit pattern formed on the surface of the printed wiring board varies depending on the position on the substrate. Therefore, the charged state differs depending on the electrical characteristics of the part where the circuit pattern made of the metal layer is formed and the part where the circuit pattern is not formed and the substrate is exposed, and the charge density is charged when charging the printed wiring board. Becomes non-uniform.
[0014]
As a result, in the above-described conventional manufacturing method, the electric flux density of the lines of electric force generated between the solder resist ink and the printed wiring board becomes non-uniform.
[0015]
In particular, as shown in FIG. 8, in the corner portion 15 of the printed wiring board 11, the electric flux density of the electric lines of force tends to increase, and the amount of application of the solder resist ink 13 increases, which causes application unevenness and solder resist thickness. There was a problem that the variation of.
[0016]
In addition, the above trend is becoming more noticeable as circuit patterns become thinner and denser, and the lower dielectric constant of the base material is required to meet the demand for higher functionality of printed wiring boards. There was a problem that this tendency became remarkable as it progressed.
[0017]
The present invention solves the above-mentioned conventional problems, and provides a method for producing a printed wiring board in which a solder resist ink is uniformly applied to the surface of the printed wiring board and coating unevenness and solder resist thickness variations are not caused. Objective.
[0018]
[Means for Solving the Problems]
In order to achieve this object, the printed wiring board manufacturing method of the present invention includes a step of processing a corner portion of a printed wiring board constituted by a plurality of individual printed wiring boards into a curved shape having a curvature radius of 2 mm or more, and a corner portion. A step of providing a through hole in a region of 10 mm from two sides, forming a circuit pattern in at least the outermost conductive layer, and at the four corners of the individual printed wiring board, the corner shape is a curve having a curvature radius of 2 mm or more A step of forming a conductive layer; and the printed wiring board having a conductive layer in which the solder resist ink is charged and the through hole and the corner are curved with a curvature radius of 2 mm or more and a curved corner with a curvature radius of 2 mm or more Sorudareji respect is intended that the manufacturing method of the printed wiring board, wherein the obtaining Bei the step of spray coating, thereby the printed wiring board surface Toinki uniformly coated with the coating unevenness is to provide a dispersion-free printed circuit board thickness.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
First, a feature of the present invention is that in the step of providing a means for preventing the density of electric lines of force from increasing at the corners of a plate-like printed wiring board, a printed wiring board having the means is prepared, and the printed wiring board is charged. And charging the ink with a charge opposite to the charge, and a process of electrostatically applying the ink onto the printed wiring board. Thereby, it has the effect | action of reducing the difference of the density of the electric force line of the corner | angular part of a plate-shaped printed wiring board, and a part other than that, and the difference and variation of the coating amount of the ink by electrostatic coating.
[0020]
Further, the present invention provides a means for providing means for preventing the density of electric lines of force from being increased, and is to finish the corners of the printed wiring board into a curved shape having a curvature radius of 2 mm or more, and to apply electrostatically onto the printed wiring board. Thus, the concentration of the electric flux density of the electric field lines at the corner tip can be eliminated by the curved shape, and the concentration of the ink application amount can be prevented.
[0021]
Furthermore, in the present invention, a conductive layer is formed in the vicinity of the corner as a step of providing means for preventing the density of the electric lines of force from being increased, and the conductive layer has a curve having a curvature radius of 2 mm or more. is there. By electrostatically applying on the printed wiring board, the curved conductive layer disperses from the tip of the corner of the electric flux density of the electric field lines, and the amount of ink applied can be made uniform.
[0022]
Furthermore, in the present invention, as a step of providing a means for preventing the density of electric lines of force from being increased, by providing a through hole in a region of 2 mm to 10 mm constituting the corner portion and electrostatically applying on the printed wiring board, By the inflow of ink into the through hole, the thickness of the surface in the vicinity of the corner is reduced, and uniform application is realized as the whole printed wiring board.
[0023]
In particular, the position of the center of the through hole is preferably 10 mm from the two sides constituting the corner, and if it is too close, the diameter of the through hole becomes small and the ink inflow amount is small. If it is too far in the opposite waste is generated in the print wiring board material.
[0024]
The diameter of the through hole is effectively 2 mm or more and 10 mm or less. At the position where the through hole is formed, the diameter is necessary to ensure the amount of ink flowing into the through hole without wasting the printed wiring board material.
[0025]
Furthermore, the present invention is also effective when the printed wiring board is composed of a plurality of individual printed wiring boards.
[0026]
In particular, as a means for preventing the density of electric lines of force from increasing at the corners of the individual printed wiring board, a conductive layer is provided near the corner of the individual printed wiring board, and the conductive layer has a curve with a radius of curvature of 2 mm or more. It is. By electrostatically applying on this printed wiring board, the curved conductive layer disperses from the tip of the corner of the electric flux density of the electric field lines, and the amount of ink applied to each individual printed wiring board can be made uniform. .
[0027]
Furthermore, the present invention is such that the conductive layer of a printed wiring board or an individual printed wiring board is formed on the front and back surfaces, and is electrically connected by a conduction hole so that the front and back surfaces have the same potential. Can be made uniform.
[0028]
(Embodiment)
Embodiments of the present invention will be described below.
[0029]
First, a first embodiment will be described.
[0030]
FIG. 1 shows a printed wiring board according to an embodiment of the present invention.
[0031]
The corners 2 at the four corners of the printed wiring board 1 on which a circuit pattern is formed on an insulating substrate are formed in a curved shape having a curvature radius of 2 mm or more. The step of forming may be before or after the formation of the circuit pattern, but needs to be performed before the subsequent solder resist coating.
[0032]
Next, the manufacturing method of the printed wiring board of this invention is demonstrated.
[0033]
FIG. 2 is a diagram showing the configuration of the electrostatic coating method for a printed wiring board according to the embodiment of the present invention. In this configuration, the solder resist is formed in the following order.
[0034]
(1) A printed wiring board 1 having a corner portion 2 as a means on which a circuit pattern is formed and the density of electric lines of force does not increase is prepared.
[0035]
(2) The printed wiring board 1 is fixed to the conveyance unit 6 maintained in the ground (0 V) state, and the entire surface of the printed wiring board 1 is grounded.
[0036]
(3) The solder resist ink 3 charged with a charge opposite to that of the printed wiring board 1 is discharged through the spray gun 7.
[0037]
(4) The solder resist ink 3 is applied to the entire surface of the printed wiring board 1 by electrostatic attraction generated by electric lines of force generated between the opposite charges in addition to the spray discharge force.
[0038]
(5) The applied solder resist ink 3 is dried by touch with hot air at 80 ° C. for about 20 minutes.
[0039]
(6) Then, it exposes by ultraviolet irradiation through the film for exposure, etc., an unexposed part is melt | dissolved and removed with a developing solution, and it hardens by heat processing for about 30 minutes at 130 degreeC, and completes a solder resist.
[0040]
Next, a second embodiment will be described.
[0041]
FIG. 3 shows a printed wiring board according to the embodiment of the present invention.
[0042]
A conductive layer 4 having a curve having a curve radius of 2 mm or more is formed in the vicinity of the corners 2 at the four corners of the printed wiring board 1 on which a circuit pattern is formed on an insulating substrate. The forming process is performed simultaneously with the formation of the circuit pattern.
[0043]
As shown in FIG. 4, even when the printed wiring board 1 is composed of a plurality of individual printed wiring boards 1b, a conductive layer 4b is formed in the vicinity of the corner 2b of each individual printed wiring board 1b. It can be done at the same time.
[0044]
Furthermore, as shown in FIG. 5, the conductive layer 4 can be formed at substantially the same location on the front and back surfaces of the printed wiring board 1, and electrical connection can be achieved through the conduction hole 5. The conductive hole 5 can be formed by electrolytic plating or by filling with a conductive paste, but may be before the circuit pattern is formed or after the circuit pattern is formed, but not before the solder resist is formed. Don't be.
[0045]
After the step of preparing the printed wiring board 1 provided with the conductive layer 4 or 4b as a means for preventing the density of the electric lines of force from increasing, the configuration and method of FIG. 2 shown in the first embodiment and Similarly, a solder resist can be formed.
[0046]
Next, a third embodiment will be described.
[0047]
FIG. 6 shows a printed wiring board according to the embodiment of the present invention.
[0048]
A through hole 5 is formed in an area of 10 mm from two sides 2c and 2d constituting the corners 2 at the four corners of the printed wiring board 1 on which a circuit pattern is formed on an insulating substrate. The step of forming may be before the formation of the circuit pattern or after the formation of the circuit pattern, but must be before the formation of the solder resist.
[0049]
In particular, the through hole 5 having a diameter of 2 mm or more and 10 mm or less is effective in securing the amount of ink flowing into the through hole 5 without causing waste in the printed wiring board material.
[0050]
After a step of preparing in this way the printed circuit board 1 having a transmural hole 5, it can be in the same manner as in the arrangement and method of Figure 2 shown in the first embodiment to form a solder resist.
[0051]
The operational effects of the present invention will be described.
[0052]
According to the present invention, by concentrating the corners of the printed wiring board in a curved shape, the concentration of the electric flux density of the electric lines of force at the corner tips can be eliminated, and the concentration of the ink application amount can be prevented.
[0053]
Further, by forming a conductive layer having a curve having a curvature radius of 2 mm or more in the vicinity of the corner, the conductive layer can be dispersed from the tip of the corner of the electric flux density of the electric field lines, and the amount of ink applied can be made uniform. Further, by forming conductive layers on both the front and back surfaces and conducting a conductive connection, variations between the front and back surfaces can be reduced.
[0054]
Furthermore, through holes are provided in the 10 mm area from the two sides that make up the corners, and the thickness of the surface near the corners is reduced by the inflow of ink into these through holes, so that the entire printed wiring board can be applied uniformly. Is realized.
[0055]
According to the embodiment of the present invention, the variation of the thickness of the solder resist between the corner portion of the printed wiring board and other portions is about 10 μm, and it can be applied remarkably uniformly as compared with the conventional variation of 20 to 30 μm. .
[0056]
In addition, in said embodiment, although the 1st-3rd embodiment of this invention was each performed independently, it is also possible to raise an effect further by combining each embodiment.
[0057]
【The invention's effect】
As described above, the present invention charges the surface of a printed wiring board to a uniform charge, thereby uniformly applying a solder resist ink, and a method for manufacturing a printed wiring board provided with a solder resist having low coating unevenness and thickness variation. Can be provided.
[Brief description of the drawings]
FIG. 1 is a diagram showing a printed wiring board in an embodiment of the present invention. FIG. 2 is a diagram showing a configuration of an electrostatic coating method for a printed wiring board in an embodiment of the present invention. FIG. 4 is a diagram showing a printed wiring board according to an embodiment of the present invention. FIG. 5 is a diagram showing a printed wiring board according to an embodiment of the present invention. FIG. 7 is a diagram showing a configuration of a conventional method for electrostatic application of a printed wiring board. FIG. 8 is a diagram showing a conventional printed wiring board.
DESCRIPTION OF SYMBOLS 1 Printed wiring board 1b Individual printed wiring board 2, 2b Corner | angular part 2c, 2d Side | side 3 which comprises a corner | angular part Solder resist ink 4, 4b Conductive layer 5 Conductive hole 6 Conveying part 7 Spray gun

Claims (1)

A step of processing a corner portion of a printed wiring board constituted by a plurality of individual printed wiring boards into a curved shape having a radius of curvature of 2 mm or more, a step of providing a through hole in a region of 10 mm from two sides constituting the corner portion, and Forming a circuit pattern in at least the outermost conductive layer and forming a conductive layer having a curved shape with a curvature radius of 2 mm or more at the four corners of the individual printed wiring board; and charging the solder resist ink to form the through hole printed circuit board, characterized in that to obtain Bei the step of spray coating to the printed wiring board corner shape having the corner portions of the conductive layer and the curvature radius of 2mm or more curved shape which is more curved curvature radius 2mm and Manufacturing method.

Images