JP2562535B2 - Printed circuit board and its processing method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed circuit board, and more particularly to a printed circuit board suitable for dividing and collecting a plurality of printed circuit boards from a single substrate or for producing a modified printed circuit board and a processing method thereof.

[0002]

2. Description of the Related Art Printed boards on which functional elements such as LSI or individual components including passive components such as resistors and connectors are mounted are used in many electronic devices. Circuits, shapes and dimensions of these printed circuit boards are diverse, and the wiring of the circuit, the position of reference holes for component placement and individual component mounting, and the part mountable range on the end face of the wiring board, etc. are also determined according to the design of the printed circuit board. Change. Therefore, each printed wiring board has a chip mounter for mounting individual components,
Alternatively, it is not necessarily designed to meet the standard of the automatic solder bath for soldering them.

Therefore, conventionally, a jig has been manufactured for each module, a printed wiring board is attached to the jig, and components are mounted and automatic soldering is performed. Therefore, the jig manufacturing cost is required, and the shape and size of the jig are different, so that the jig is difficult to store and manage. Further, an extra work of setting the substrate on the jig is required, and further, an error in mounting at that time affects mounting accuracy, and there is a problem in terms of operation of the automatic machine.

As a solution to the above problems, as shown in FIGS. 4 and 5, there is a method of producing a plurality of printed boards 2 or odd-shaped printed boards 3 by using one standardized sheet board 1. was suggested. In this method, by standardizing the sheet substrate so as to conform to the specifications of the chip mounter and the automatic solder bath, (1) no jig is required in the automatic machine and other steps, (2) the reference hole 4 is formed. Since it can be processed simultaneously with, for example, a through hole of a printed circuit board, mounting accuracy of individual components is good. (3) Since a plurality of printed circuit boards can be made using one sheet substrate 1, the manufacturing efficiency of the printed circuit board is high, (4) Since the sheet substrate 1 is standardized, there is an advantage that it can be easily attached to an automatic machine and storage and management can be simplified.

On the other hand, the printed circuit board needs to be divided and sampled from the sheet board or processed by punching or the like between any steps. This division processing has the following problems.

(1) The divisional machining requires precise machining, and the machining accuracy must be maintained at an allowable value.

(2) If there is an individual part projecting outward from the end face of the printed circuit board to be divided, it is impossible to cut by the contour processing machine. Therefore, such an individual part is divided and processed before mounting. And for that,
The advantages of this method described above are diminished.

(3) In the above case, the printed circuit board cannot automatically carry the solder bath. A jig for a solder bath is required for automatic transfer, which requires man-hours for manufacturing the jig and setting the jig, and a soldering failure may occur due to a setting error at that time. When a soldering failure occurs, a new problem occurs such as a correction work or an adverse effect on a subsequent process.

By the way, although many steps are required to manufacture a printed circuit board, for example, a soldering step using an automatic soldering tank is required for soldering individual parts other than chip parts such as connectors. . On the other hand, in the final finishing step of the printed circuit board, it is often easier to work not in the state of the sheet substrate but in the state of the divided printed circuit board alone. Therefore, it is desirable to be able to divide each printed circuit board with a simple tool in the final step after the soldering step is completed.

Therefore, as shown in a plan view of FIG. 6A and a partially enlarged view of FIG. 6B, a width of about 1 mm is provided around the printed board 2 of the sheet board 1 before mounting the individual components. A method of forming the slit 6 by leaving the tab 5 at several places has been proposed. In FIG. 6B, reference numeral 7 denotes parts such as a variable resistor and a connector. According to this method, the printed board can be divided with a very simple tool, and the division is easy even when the individual parts project from the outer edge of the printed board. Moreover, it does not give stress to the divided printed circuit boards, but according to this method, each printed circuit board is supported only by a tab having a very small area,
Its supporting strength is small.

Therefore, the influence of heat is unavoidable in the solder reflow process or the soldering process in the automatic solder bath, the substrate warps depending on the size and thickness of the sheet substrate, and in the mounting process of individual components by the chip mounter. Poor mounting may occur. Also, in the soldering process using the automatic solder bath, a general jet method is used, and the bottom surface of the sheet substrate is brought into contact with the molten solder flow for soldering, but if the warp of the sheet substrate is large, soldering failure easily occurs. In extreme cases, molten solder may even flow through the slit to the top surface of the sheet substrate.

In order to prevent the drawbacks associated with such slit processing, it is conceivable to form a V groove instead of the slit. However, it goes without saying that in the case of the V groove, the width of the upper portion is wider than the width of the bottom of the groove. Due to the demand for miniaturization of electronic devices, high-density mounting of printed circuit boards is progressing,
Wiring is formed or parts are mounted up to the end of the board. Therefore, when forming the V-groove, if the position of the bottom of the groove is adjusted to the external dimensions of the printed circuit board, there is a risk of cutting the wiring pattern or the pad, and if it is attempted to avoid this danger, the finished size of the printed circuit board will increase. There's a problem. In addition, this method has a problem that it is difficult to apply it to a modified printed circuit board.
If the thickness of the substrate at the bottom of the groove is large, it is not easy to cut, and stress is applied to the divided printed circuit board. Conversely, if the substrate at the bottom of the groove is thinned, the warpage of the substrate of the sheet substrate is larger than that of the slit-processed substrate. Sometimes, it falls off the rail for automatic transportation.

[0013]

As described above, in the prior art, in order to improve the productivity of the printed circuit board, a large number of printed circuit boards or odd-shaped printed circuit boards are formed by using one standardized sheet substrate. It was impossible to produce a printed circuit board by a simple tool without warping the sheet board due to heat during production.

The present invention overcomes these drawbacks of the prior art,
It is an object of the present invention to provide a printed circuit board which does not warp during the soldering process and can be easily divided into individual printed circuit boards.

A further object of the present invention is to provide a method of treating a substrate to achieve the above object.

[0016]

A printed circuit board according to the present invention has at least one printed wiring area, and a slit is formed around the printed wiring area while leaving a plurality of microscopic areas. Is characterized in that it is filled with a resin different from the resin constituting the printed circuit board.

A method of treating a printed circuit board according to the present invention comprises a step of providing slits around a printed wiring area formed on an insulating substrate while leaving a plurality of minute areas, and a resin different from the resin forming the printed circuit board is provided in the slits. It is characterized by having a step of filling and a step of curing the resin.

[0018]

According to the present invention, a slit is provided around the printed wiring area of the sheet substrate while leaving a slight tab, and a resin having good peelability from the substrate, that is, a resin forming the substrate is provided in the slit. It is filled with non-adhesive or weakly adhesive resin. Therefore, the sheet substrate does not warp in the soldering process, the resin can be easily removed from the substrate, and each printed circuit board can be easily divided with a simple tool.

[0019]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a flow chart for explaining a printed circuit board processing method according to the present invention.

First, in step A, the wiring pattern of the printed board 2 is formed at a predetermined position of the sheet board 1.
At this time, usually four reference holes 4 of the sheet substrate 1 are provided along with the through holes of each printed circuit board. As the sheet substrate, a glass base material epoxy resin copper clad laminate, a glass composite base material and the like are usually used. All materials can be used.

Next, in step (B), slits 6 having a width of about 1 mm to 2 mm are provided around each printed circuit board 2. The slits 6 are separated by tabs 5. The size and number of the tabs are determined in consideration of the strength required for the subsequent automatic mounting and automatic soldering of LSI chips and parts, but the width is usually about 1 mm, and several tabs are provided for each printed circuit board.

Next, in step (C), the slit 6 is filled with the resin 8. If this resin is not cured, the strength of the board will be lower than in the case where there is no slit, and the printed board will be distorted in the subsequent step of mounting the chip component. Therefore, as the resin 8, the hardness after curing is sufficient to support the printed circuit board, and the resin 8 has good releasability from the sheet substrate, that is, non-adhesiveness or weakness to the resin forming the printed circuit board. It is necessary that it is adhesive and that the substrate does not warp during curing. Although it is possible to use a thermosetting resin, if a thermosetting resin is used, the process of applying heat for curing is increased by one process, so stress is added to the printed circuit board by that amount, so do not apply heat. A resin that cures is more desirable.

In order to meet such requirements, an ultraviolet curable resin, particularly a solder masking agent used for covering unnecessary portions for soldering in the soldering process can be used. As a method for filling the resin in the slit, a pressure-feeding method using a dispenser or a screen printing method can be used.

Next, in step (D), the resin 8 filled in the slit 6 is irradiated with ultraviolet rays to be cured.

Using the sheet substrate thus treated, after the steps of mounting components such as an LSI chip, a resistor, a connector, etc., automatic soldering, etc., as in the conventional case,
The cured resin is removed, and the tab is cut with a tool such as a nipper to divide the printed circuit board.

Next, a specific manufacturing example will be described.

Width 19 cm. Length 19 cm, thickness 0.8 m
m glass-based epoxy resin copper-clad laminate 1 of m was prepared, and a printed wiring pattern was formed in each of two regions 2 of 16 cm × 6 cm. The distance between the two printed circuit board areas was 2.5 cm. As shown in FIG. 2, slits 6 having a width D of 1 mm were provided around the two printed circuit boards by cutting. The width d is 1 between the slits 6.
mm tabs 5 are left, so the slits are discontinuous. Although FIG. 2 shows only a part of the sheet substrate, the tabs 5 are provided at four corners of each printed circuit board. Note that FIG.
6A is a spare slit for facilitating the division of the printed circuit board later.

Next, a modified acrylate type ultraviolet curing resin 8 (LITEMASK manufactured by Nippon Loctite Co., Ltd.) was slit 6 by a pressure-feeding method using a dispenser.
And filled in 6A. This state is shown in FIG. This resin is the solder masking material described above. The filled resin was irradiated with a mercury lamp having an illuminance of 100 mW / cm ² for 2 seconds to cure the resin.

A component 7 such as an LSI chip, a resistor, and a connector is mounted on the printed circuit board (sheet substrate) processed in this way using a chip mounter, and further, necessary soldering is performed using an automatic soldering tank. Further, during soldering, almost no warpage was observed in the sheet substrate, and the amount of warpage was equal to the amount of warpage in the sheet substrate that was not slit. On the other hand, for comparison, in the case of a sheet substrate of the same size in which slit processing was performed and resin was not filled, the difference in height from the horizontal plane was 4 at the central portion and the peripheral portion of the substrate.
A warp of about mm occurred. The warp of the board is larger as the board is larger and thinner, and when a board having an outer shape of 30 cm × 25 cm and a thickness of 0.8 mm is slit, a warp of 1 cm in height may occur in the soldering process. is there. However, according to the present invention, the strength of the resin filled in the slit after curing is sufficient to suppress the warpage of the substrate, and in a necessary step after the soldering step, the cured resin is removed from the slit. It could be peeled off easily. After removing the resin, the individual printed circuit boards could be easily separated from the sheet substrate by cutting the tabs.

The width of the slit is determined according to the external dimensions and thickness of the sheet substrate and each printed circuit board. As a result of experiments on substrates of various sizes, the slit width was 0.9
By setting the thickness to mm to 2.0 mm, it was possible to suppress the warpage of a wide range of substrates. The width of the tab separating the slits is suitably 0.5 to 1 mm, and when the printed board is rectangular, the number is 2 to 4 and may be provided at an appropriate place in each corner or each side. . When the printed circuit board has an irregular shape, it may be determined in consideration of the convenience of forming the slit.

[0032]

As described above, according to the present invention,
Using standardized sheet boards, multiple printed boards including odd-shaped printed boards can be manufactured at the same time. In particular, (1) The printed boards can be easily divided for the final finishing process. It is possible to eliminate the time loss of the movement between steps.

(2) A jig for setting the substrate in the automatic soldering tank is not required, the manufacturing cost of the jig and the jig setting process can be omitted, and the production yield can be prevented from lowering due to a setting error. You can

(3) A jig for setting the board on an automatic machine or a semi-automatic machine for mounting various parts such as an LSI chip on the printed circuit board is unnecessary.

(4) The setup time of the automatic machine can be reduced by standardizing the dimensions of the sheet substrate.

(5) The odd-shaped printed board can be handled like a rectangular printed board, and the board can be easily managed.

(6) By using a solder mask material as the resin with which the slits are filled, the resin can be filled and cured simultaneously with the masking process, and the process can be simplified.

(7) The production efficiency of the printed circuit board can be greatly improved.

It has the excellent effect of

[Brief description of drawings]

FIG. 1 is a flowchart illustrating a method of treating a printed circuit board according to the present invention.

FIG. 2 is a plan view illustrating an embodiment of the present invention.

FIG. 3 is a partially enlarged view of FIG.

FIG. 4 is a plan view of a conventional sheet substrate.

FIG. 5 is a plan view of a conventional sheet substrate.

FIG. 6 shows another conventional example, (a) is a plan view and (b) is a partially enlarged view thereof.

[Explanation of symbols]

 1 Sheet Substrate 2 Printed Circuit Board 3 Variant Printed Circuit Board 4 Reference Hole 5 Tab 6 Slit 7 Parts 8 Resin

Claims (5)

(57) [Claims] 1. A slit having at least one printed wiring region and a plurality of minute regions remaining around the printed wiring region, the slit being different from the resin forming the printed circuit board. A printed circuit board characterized by being filled with the resin of. 2. The printed circuit board according to claim 1, wherein the foreign resin is non-adhesive or weakly adhesive to the resin forming the printed circuit board. 3. The printed circuit board according to claim 1, wherein the foreign resin is an ultraviolet curable resin. 4. A step of providing slits around a printed wiring area formed on an insulating substrate while leaving a plurality of minute areas, a step of filling the slits with a resin different from a resin constituting the printed board, and the resin. A method of treating a printed circuit board, comprising a step of curing. 5. The treatment of a printed circuit board according to claim 4, wherein the resin is a radiation-sensitive curable resin, and the step of curing the resin is a step of irradiating the radiation-sensitive curable resin with radiation. Method.