JPS6349218B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a divided projection exposure method for printed circuit boards in which a wiring pattern to be printed is divided into a plurality of parts and exposed by projection onto corresponding parts on a printed circuit board. .

[Conventional technology]

BACKGROUND OF THE INVENTION In recent years, as the performance of electronic devices has improved, there has been a strong desire to increase the wiring density of printed circuit boards and increase their size.

Generally, printed circuit boards are made of phenol paper,
After uniformly bonding extremely thin copper foil to the surface of an insulating plate-like substrate such as epoxy paper or epoxy glass, and forming a photosensitive resist layer on top of it, the desired wiring pattern is exposed and baked, followed by etching. Therefore, the unexposed portions of the copper foil are removed to form printed wiring, and the resist remaining thereon is peeled off with a solvent or alkaline solution.

There are two methods for exposing wiring patterns: the contact exposure method, in which a reticle with a wiring pattern formed thereon is brought into direct contact with the surface of the printed circuit board, and the other is the contact exposure method, in which the reticle pattern is optically projected onto the surface of the printed circuit board. There is a projection exposure method.

The former has a simple exposure device and can maintain good reticle adhesion, so it is often used especially when it is difficult to maintain flatness, such as with flexible substrates. There was a serious problem that could easily occur.

On the other hand, in the latter case, the exposure equipment becomes complicated, and in the case of a flexible substrate, it is difficult to maintain flatness, but since the reticle is located far from the substrate, there is no risk of scratches, and workability is good. Therefore, it is becoming the mainstream of future printed circuit board exposure methods.

[Problem that the invention seeks to solve]

However, in such a printed circuit board exposure method using the projection exposure method, the reticle pattern is projected onto the printed circuit board through a projection lens to perform exposure, so the resolution of the projected image is maintained at a good level, and its illuminance is In order to make the image uniform, there is a natural restriction on the size of the image surface that can be projected, and it has been extremely difficult to create large printed circuit boards using the projection exposure method.

Further, even if a large wiring pattern is formed by projecting and exposing a plurality of wiring patterns adjacent to each other on a printed circuit board, it is not easy to connect each wiring pattern in a circuit manner.

SUMMARY OF THE INVENTION An object of the present invention is to provide a divided projection exposure method for printed circuit boards that can solve these conventional problems.

[Means for solving problems]

Therefore, in the first aspect of the divided projection exposure method for a printed circuit board according to the present invention, a wiring pattern to be printed is divided into a plurality of parts and each wiring pattern is formed on a plurality of projection reticles. A connecting part with the same land pattern is provided near the dividing boundary line of the projection reticle, and the connecting part between the leading projection reticle and the succeeding projection reticle that projects adjacent to the leading projection reticle is exposed redundantly. By doing so, each printed wiring pattern is connected in a circuit manner through a connecting portion.

Further, in the second invention, in addition to the above method, a light reduction means for reducing the exposure amount is provided at the connecting portion of the projection reticle having the same land pattern, and the overlapping exposure amount of this connecting portion is reduced. It was made almost equal to the exposure amount.

[Effect]

With this method, first, the first projection reticle is projected onto the first part of the printed circuit board for exposure, and then the second projection reticle is projected onto the second part adjacent to the first part. 1. When projection exposure is performed with the connection parts of the second reticle overlapped, the same land pattern provided at the overlapped connection parts of the first and second reticles is double exposed on the printed circuit board. The first and second wiring patterns printed on adjacent first and second portions on the printed circuit board are connected in a circuit manner through this connecting portion.

Similarly, by projecting and exposing the third, fourth... wiring patterns onto the adjacent third, fourth... portions on the printed circuit board, the first, second, third,...
A fourth circuit-connected composite wiring pattern can be obtained.

In addition, the exposure amount is doubled for the joints that are exposed overlappingly, and if the distance between the projected land patterns is extremely small, each element of the overexposed land pattern may accidentally cross each other due to light bleeding. Continuity may occur.

Such inconvenience can be easily solved by applying the second invention.

In other words, when projecting the first and second reticles, the light attenuation means provided at the overlapping connection parts reduces the single exposure amount by half, and by double exposure, the appropriate exposure amount is approximately equal to the exposure amount of other parts. It is possible to prevent accidental conduction between each element of the land pattern.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 to 6 of the accompanying drawings.

FIG. 6 schematically shows a divided projection exposure method according to the present invention, in which a projection reticle 1A having a wiring pattern 1a to be projected is opposed to a desired portion 3a of a printed circuit board 3 with a projection lens system 2 in between. , illumination light is irradiated from behind the projection reticle 1A, and the line pattern 1a is projected onto a desired portion 3a of the printed circuit board 3 for exposure.

Next, the support plate holding the projection reticle 1A is moved along the plane in the direction of arrow A, and the printed circuit board 3 is moved along the plane in the opposite direction, in the direction of arrow B. Place the reticle 1B on the printed circuit board 3 with the projection lens system 2 in between.
The wiring pattern 1b is exposed by projecting the wiring pattern 1b onto the portion 3b of the printed circuit board 3 by irradiating illumination light from behind the projection reticle 1B.

By doing this, the wiring patterns 1a and 1 are formed on the adjacent parts 3a and 3b of the printed circuit board 3.
b can be exposed by projection.

FIG. 1 shows an embodiment of the present invention, in which the entire wiring pattern 11 to be printed on the printed circuit board 3 shown in FIG. 6 is covered by the projection lens system 2 in a field size 10 shown in FIG. Corresponding wiring patterns 11a, 11b, 11c, 11d
Projection reticles 11A, 11B, 11C, and 11D are created by dividing wiring patterns 11a to 11d (see FIG. A desired wiring pattern is formed on the printed circuit board 3 by sequentially projecting it onto 3a, 3b, 3c, and 3d, exposing it, and processing it.

The division boundaries 11ab, 11bc, 11cd of each of these projection reticles 11A to 11D,
In the vicinity of 11da, these dividing boundaries 11ab~
Connecting portions 12a ₁ , 12b 1 , 12b ₂ , 12c ₁ , 12c 2 , each having the same land pattern 12ab, 12bc, _12cd , _12da perpendicular to 11da,
12d ₁ , 12d ₂ , and 12a ₂ are provided (see C in the same figure).

Therefore _{, as shown} in FIG _. By overlapping projection exposure, each land pattern 12ab, 12
bc, 12cd, 12da are each double exposed,
The respective wiring patterns formed on the respective parts 3a to 3d on the printed circuit board 3 are connected to each other via these connecting parts, and a desired synthesized wiring pattern can be obtained.

In the above embodiment, each connection part is exposed redundantly and each land pattern is given twice the exposure amount as each wiring pattern, so when the wiring pattern is properly exposed, the land pattern becomes overexposed and exposed to light. Due to the bleeding phenomenon, each element expands outward and is exposed to light.

Therefore, there is no problem if there is a certain distance between the land patterns, but if the distance becomes extremely small, adjacent land patterns may come into contact with each other and become electrically conductive.

In order to avoid this, it is necessary to provide some kind of light reduction means to reduce the amount of exposure at the connection portion of each projection reticle.

FIG. 2 shows an example of such a light attenuation means, in which filters 4A, 4B, 4C, and 4D are provided corresponding to each projection reticle 11A to 11D, and each projection reticle is attached to these filters 4A to 4D. 11
Semi-transparent parts 4a, 4b, 4c, and 4d with a transmittance of 50% are formed corresponding to the connecting parts 12a1 to _12d2 of _A to 11D, and the other parts are transparent parts with a transmittance close to 100%.

When these filters 4A to 4D are superimposed and projected onto the projection reticles 11A to 11D, each connection part 12a ₁ to 12d ₂ is exposed redundantly as shown in FIG. 3, so that other parts are not exposed. The appropriate exposure amount is almost the same as the amount of light, and accidental conduction between each element of the land pattern can be prevented without causing a light bleeding phenomenon.

Here, the semi-transparent parts 4a to 4D of the filters 4A to 4D
The transmittance of 4d does not necessarily have to be set to 50% each, but it is sufficient if it is close to 100% by overlapping exposure, such as 30% and 70% or 40% and 60%. Also, as shown in Figure 4, The transmittance may be gradually increased or decreased, and by doing so, even if the projection position is slightly shifted, the exposure amount of the connecting portion can be made appropriate over the entire area.

Furthermore, such a light attenuation section is provided by filters 4A to 4.
Although it can be easily created by locally depositing a translucent material on a part of D, the filter may be omitted and the material may be deposited on the front or back surface of the projection reticles 11A to 11D.

Strictly speaking, the exposure amount is doubled in a part of the center where all of the light reduction parts 4a to 4d overlap, but
Since this portion is an extremely small area, no land pattern is provided in this portion.

Next, FIG. 5 shows another embodiment of the present invention in which the present invention is applied to a flexible printed circuit board, which is a flexible printed circuit board. A flexible substrate 13 is stretched between a supply shaft and a take-up shaft, and can be fed in the direction of arrow B by a rotating sprocket.

The wiring pattern to be printed on the flexible substrate 13 is divided into two parts as shown in FIG. 6 to form first and second projection reticles each having a connection part, and the same process as in the previous embodiment is performed. After projecting and exposing the first projection reticle to the first portion 13a of the printed circuit board 13, the printed circuit board 13 is moved in the direction of arrow B and the second projection reticle is projected and exposed to the second region 13b. .

In this case as well, by making the feeding amount of the printed circuit board 13 slightly smaller than the horizontal length of the portion 13a, the connecting portion 1 is placed between the portions 13a and 13b.
2a can be formed, and it becomes possible to connect the first and second wiring patterns in a circuit manner through this connecting portion 12a.

Further, third, fourth, . . . wiring patterns can be further connected in the same manner.

In the above embodiment, the same land pattern is provided near the division boundary line of the projection reticle and is perpendicular to the division boundary line, but this land pattern does not necessarily need to be orthogonal to the division boundary line.

Further, all of these land patterns do not need to be the same, and it is sufficient that the overlapping land patterns are the same.

Furthermore, the density of each line of the land pattern is
It is desirable to make the density slightly coarser than the wiring pattern density in consideration of variations in the projection position of the projection reticle that comes after the front projection reticle.

〔Effect of the invention〕

As described above, in the divided projection exposure method for a printed circuit board according to the present invention, in the first invention, a wiring pattern to be printed is divided into a plurality of parts and formed on a plurality of projection reticles. We decided to provide a connecting part with the same land pattern near the dividing boundary line of the reticle, and to expose the adjacent leading and trailing projection reticle joints redundantly, so that The leading and trailing wiring patterns formed on the printed circuit board are connected in a circuit manner, and by repeating this process, an extremely large printed circuit board can be obtained.

In addition, in the second invention, since a light reduction means for reducing the exposure amount is provided at this connection portion, the overlapping exposure amount of the connection portion of the adjacent front and rear projection reticles can be reduced to the exposure amount of the other portion. Approximately equal exposure amounts can be achieved, the resolution of each element constituting the land pattern is improved, and accidental conduction is prevented.

[Brief explanation of drawings]

Figure 1 A, B, C, and D are explanatory diagrams showing the first embodiment of the present invention, Figure 2 is a plan view of a filter used in the present invention, Figure 3 is a diagram showing the transmittance of the filter, and Figure 3 is a diagram showing the transmittance of the filter. Figure 4 is a diagram showing the transmittance of other filters.
FIG. 5 is an explanatory diagram showing another embodiment of the invention, and FIG. 6 is an optical path diagram showing an outline of the divided projection exposure method according to the invention. 1A, 1B, 11A, 11B, 11C, 11D
...Projection reticle, 1a, 1b, 11a, 11
b, 11c, 11d...wiring pattern, 11ab,
11bc, 11cd, 11da...dividing boundary line, 12ab,
12bc, 12cd, 12da...land pattern, 1
2a ₁ , 12a ₂ , 12b ₁ , 12b ₂ , 12c ₁ , 12
c ₂ , 12d ₁ , 12d ₂ , 12a...Connection part, 3...Printed circuit board, 4A, 4B, 4C, 4D...Filter (light reduction means) 4a, 4b, 4c, 4d...Semi-transparent part,
13...Flexible board (printed board).

Claims (1)

[Claims] 1. A wiring pattern to be printed is divided into a plurality of parts, each wiring pattern is formed on a plurality of projection reticles, and the same land pattern is formed near the dividing boundary line of these projection reticles. By providing a connection part with a projection reticle and exposing the connection part between the front projection reticle and the rear projection reticle that projects adjacently, each printed wiring pattern can be connected to the connection part. A divided projection exposure method for a printed circuit board, characterized in that the printed circuit board is connected in a circuit manner through. 2 Divide the wiring pattern to be printed into multiple parts, form each wiring pattern on multiple projection reticles, and connect parts with the same land pattern near the division boundaries of these projection reticles. At the same time, the connecting portion is provided with a light reduction means for reducing the amount of exposure, and the connecting portion between the leading projection reticle and the rear projection reticle that projects adjacently is exposed redundantly. A divided projection exposure method for a printed circuit board, characterized in that each wiring pattern is connected in a circuit manner through the connection portion, and the overlapping exposure amount of the connection portion is made approximately equal to the exposure amount of the other portion.