JP3330997B2 - Exposure equipment for circuit board formation - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus used for manufacturing a circuit board.

[0002]

2. Description of the Related Art In recent years, circuit boards, which are one of electronic components, have been diversified and used in many fields. This circuit board is manufactured through various processes, and one of those processes, an exposure process, is made of a polymer film on which a wiring pattern is drawn, or coated on a substrate through a glass photomask. Photoresist (photosensitive layer)
This is a step of irradiating the surface with ultraviolet rays. Therefore, the exposure step is an important step for faithfully transferring the wiring pattern of the photomask to the circuit board.

In general, an exposure method includes a projection method in which a photomask is arranged on a light source side away from a substrate and a pattern is projected onto the substrate, and a pattern in which a photomask and a photoresist, that is, a substrate are brought into close contact with each other to form a pattern on the substrate. There are two types of contact method to transfer on top,
When exposing a circuit board, it is common to use a contact method capable of irradiating a wide range of ultraviolet rays. In the case of this contact exposure method, the degree of close contact between the photomask and the substrate is an important point in order to clearly transfer the pattern of the photomask to the substrate.

Here, the procedure will be described by taking, as an example, the case of an exposure step of a flexible printed wiring board having a double-sided pattern, which is one type of circuit board. First, as a preparation before mounting a substrate and a photomask in an exposure apparatus, a circuit board forming unit is prepared. As shown in FIG. 4, the circuit board forming unit 1 has photomasks 3a, 3
b, and transparent plates 4a and 4b made of an acrylic plate called a photo tool are superimposed in this order, and the positioning pins 5 installed on the lower transparent plate 4b The masks 3a, 3b and the reference holes 6, 6,... Formed in the upper transparent plate 4a are inserted and aligned with each other.

Next, an exposure apparatus for forming a circuit board will be described with reference to FIGS. FIG. 5 and FIG.
FIG. 2 shows a structure of a portion where the circuit board forming unit 1 is mounted, that is, a so-called burning frame portion A. This grilled frame part A is
This is a portion for bringing the photomask and the substrate into close contact with each other, supporting them, and irradiating the ultraviolet rays S. As shown in FIG. 5, one side of two frame-shaped metal frames 8a and 8b having an exposure opening 7 at the center is rotatably connected by a hinge (not shown). A flexible polymer film 9 is provided on the frame 8a, and a glass plate 10 is provided on the lower frame 8b so as to seal the exposure openings 7, 7 of the frames 8a, 8b.
A packing 11 made of a rubber tube is provided on the upper surface of the glass plate 10 along the outer peripheral edge thereof. The thickness of the packing 11 is very slightly larger than the thickness of the circuit board forming unit 1. Further, exhaust holes 12, 12 are formed at two corners of the glass plate 10 corresponding to the exposure opening 7, and these exhaust holes 12, 1 are formed.
A vacuum pump 13 is connected to 2.

In order to install the circuit board forming unit 1 on the burning frame A, first, the circuit board forming unit 1 is placed on the glass plate 10 and sandwiched between a pair of frames 8a and 8b. FIG. 6 shows a state in which the circuit board forming unit 1 is sandwiched between the frames 8a and 8b. In this case, the upper and lower sides are surrounded by the polymer film 9 and the glass plate 10, and the periphery is surrounded by the packing 11. The airtight space 14 is formed, and the thickness of the packing 11 is only slightly larger than the thickness of the circuit board forming unit 1. Therefore, the polymer film 9 installed on the upper frame 8a is The state is very close to the upper surface of the substrate forming unit 1. And the space 14
Is evacuated by the evacuation pump 13. When the space 14 is in a negative pressure state, a force acts in a direction in which the volume of the space 14 is reduced, so that the flexible polymer film 9 is formed.
When the polymer film 9 is bent and comes into close contact with the circuit board forming unit 1 and further evacuation proceeds, the polymer film 9 presses the circuit board forming unit 1. Thus, the photomasks 3a and 3b inside the circuit board forming unit 1 and the substrate 2
And tightly adhere.

[0007]

However, in the conventional exposure apparatus for forming a circuit board, the portion for supporting the substrate and the photomask has the above-described structure. The ultraviolet rays S pass through the polymer film 9 of the upper frame 8a of the exposure apparatus, the transparent plate 4a of the circuit board forming unit 1, and the photomask 3a and the three layers to reach the substrate. In the exposure step, if the layer through which the ultraviolet light is transmitted is scratched or dust adheres, the ultraviolet light will be irregularly reflected or shielded by these, and a defective pattern will be formed on the substrate. It is important to eliminate the factors that cause defects. In that sense, the conventional configuration having three ultraviolet transmission layers has a problem that the defect rate of the wiring pattern is increased because there are many factors of generation of scratches and adhesion of dust. In particular, since the polymer film 9 is fixed to the exposure device, once the polymer film 9 is scratched, all the circuit boards manufactured by the exposure device are not damaged unless the polymer film 9 is replaced. There was a concern that this would have an effect.

In addition, when the ultraviolet rays S pass through the polymer film 9, the transparent plate 4a, etc., part of the energy of the ultraviolet rays S is absorbed by these transmission layers. There is also a problem that the energy of the effective ultraviolet light which contributes is attenuated.

In order to firmly adhere the photomask and the substrate, the polymer film 9 corresponding to the position of the substrate 2 must press the circuit board forming unit 1 over a wide range with a predetermined pressure. It is necessary to raise the degree of vacuum to a certain degree or more. Therefore, when the degree of vacuum is reduced for some reason, the polymer film 9 cannot uniformly press the circuit board forming unit 1 over a wide range, so that the adhesion between the photomask 3a and the substrate 2 is poor and the photomask is poor. There is a possibility that a portion where the wiring pattern is not clearly transferred to the substrate may be formed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and can reduce the factor of generating a defective pattern such as a scratch or dust in an ultraviolet light transmitting layer, and can effectively reduce exposure. It is an object of the present invention to provide an exposure apparatus for forming a circuit board, which can increase the energy of a specific ultraviolet ray and can uniformly contact a photomask and a substrate over a wide range.

[0011]

To achieve the above object, a circuit board forming exposure apparatus according to the present invention comprises a photomask and a transparent plate superposed in this order on a photosensitive layer formed on the front and back surfaces of a substrate. In a circuit board forming exposure apparatus for exposing the photosensitive layer with the circuit board forming unit sandwiched between a pair of frames, the frame corresponds to a portion where a photomask of the circuit board forming unit is disposed. An opening for exposure is formed at a position where the first and second substrate seal ridges are in airtight contact with both sides of the peripheral portion of the circuit board forming unit, and the outer peripheral portion of the circuit board forming unit is outside. And a frame sealing ridge that hermetically seals between the two frames at a position spaced apart from each other, and at least one of these frames is formed between the sealing ridges. It is formed an exhaust port for the negative pressure release space portion, wherein the transparent plate is than the outer shape of the substrate
Are also large, and at least one of these transparent plates
A groove surrounding the substrate along the outer peripheral edge of the substrate;
And a communicating portion that opens the inside of the space portion .

[0012]

According to the circuit board exposure apparatus of the present invention,
The circuit board is mounted on a pair of frames sandwiching the circuit board forming unit.
First and second substrates in contact with the peripheral edge of the substrate forming unit
Seal ridge and frame seal to seal between the frames
The closed space is formed by the ridge and this space
The periphery of the circuit board forming unit projects into the
And When the interior of the space is exhausted under negative pressure,
Through the peripheral edge of the circuit board forming unit,
Substrate, photomask, and transparent plate
Negative pressure also exists between the joining surfaces.

[0013] hand, since the both frames are formed exposure opening portion, the outer surface of both of the circuit board forming unit is open to the atmosphere, it will undergo atmospheric pressure on both the outer surface co. That is, a negative pressure is applied between the bonding surfaces of the substrate, the photomask, and the transparent plate that constitute the circuit board forming unit.
Since both outer surfaces of the circuit board forming unit are in an atmospheric pressure state, by pressing both outer surfaces of the circuit board forming unit inward each other, the substrate and the photomask sandwiched between the circuit board forming unit and Will adhere.

Further, in the exposure apparatus for forming a circuit board according to the present invention, the peripheral portion of the photomask is covered with the transparent plate, and the peripheral portion is sealed by the groove formed in the transparent plate and the communicating portion. Since the space is communicated with the space surrounded by the ridge, the peripheral portions of the substrate and the photomask can be reliably brought into the negative pressure state.

[0015]

An embodiment of the present invention will be described below with reference to FIGS. First, when performing exposure, a circuit board forming unit described below is first prepared, and this circuit board forming unit is mounted on an exposure apparatus. FIG. 3 shows a configuration of a circuit board forming unit. The circuit board forming unit 15 includes photomasks 17 a and 17 made of a polymer film on both sides of a substrate 16.
b and a transparent plate 18a, 18b made of an acrylic plate called a photo tool are stacked in this order. The transparent plates 18a and 18b are made larger than the outer shapes of the substrate 16 and the photomasks 17a and 17b, and the thicknesses of the photomasks 17a and 17b and the substrate 16 are smaller than the thicknesses of the transparent plates 18a and 18b. Since the plate thickness is quite thin, when these are overlapped, the transparent plate 18a,
The upper and lower transparent plates 18a and 18b are in contact with each other at the periphery of the transparent plates 18a and 18b.

The upper transparent plate 18a is a plate material whose upper and lower surfaces are flat. On the other hand, the lower transparent plate 18b is
As shown in FIG.
A groove 19 is formed along the outer peripheral edges of the substrate 16 and the photomasks 17a and 17b in a state where the lower transparent plate 7a and 17b are placed. An opening groove (communication portion) 20 penetrates a wall portion outside the groove toward the end face of 18b.
Are formed.

FIG. 1 and FIG. 2 show the structure of a burning frame portion of an exposure apparatus to which the circuit board forming unit is mounted. The burning frame portion B is a portion for bringing the photomask and the substrate into close contact with each other, supporting them, and irradiating the ultraviolet rays S. As shown in FIG. 1, the burning frame portion B has two sides of two frame-shaped aluminum frames 22a and 22b having an exposure opening 21 at the center, and one side thereof is rotatable by a hinge (not shown). It is connected.

On the lower surface side of the upper frame 22a, an inner packing 23 (first substrate sealing projection) made of natural rubber having excellent airtightness is formed along the periphery of the exposure opening 21 and the outer periphery. Ridge) and an outer packing 24 (frame seal ridge). In addition, a lower packing 25 (second board seal ridge) is disposed on the upper surface side of the lower frame 22b at a position facing the inner packing 23 of the upper frame 22a with the circuit board forming unit 15 interposed therebetween. A projecting wall 26 (frame seal ridge) is formed on the outermost peripheral portion. When the circuit board forming unit 15 is mounted, the inner packing 23 and the lower packing 25 are opposed to the peripheral edge of the circuit board forming unit 15 when the packings 23, 24, 25 and the protruding wall 26 are installed. The outer packing 24 and the protruding wall 26 are arranged so as to be in contact with each other outside the circuit board forming unit 15 so as to be in contact with each other. further,
One exhaust hole 27 penetrating in the thickness direction of the frame is formed between the lower packing 25 corresponding to the center of one side of the lower frame 22b and the protruding wall 26, and the exhaust hole 27 is It is connected.

In order to mount the circuit board forming unit 15 in the exposure apparatus, the circuit board forming unit 15 is mounted on the lower transparent plate 18b by the side of the lower frame 22b where the opening groove 20 is located.
So that the lower frame 2
2b placed on the lower packing 25 and the upper and lower frames 2
2a and 22b. FIG. 2 shows a state in which the circuit board forming unit 15 is sandwiched between the frames 22a and 22b. In this state, the upper and lower frames 22a and 22b and the packings 23 and 2
4, 25, and a space portion 29 sealed by the protruding wall 26 is formed. When vacuum evacuation is performed through the exhaust hole 27 opened in the space 29, the space 2
9 becomes a negative pressure state of 10 Torr or less, a groove 19 surrounding the photomasks 17a, 17b and the substrate 16 through an opening groove 20 provided in the lower transparent plate 18b of the circuit board forming unit 15, and furthermore, a transparent upper and lower part. Plate 18a,
The space between the opposing surfaces 18b is in a negative pressure state.

On the other hand, since the upper and lower frames 22a, 22b have exposure openings 21, 21, the outer surfaces of the upper and lower transparent plates 18a, 18b are open to the atmosphere, and both outer surfaces receive atmospheric pressure. ing. That is, the upper and lower transparent plates 18
a and 18b are placed in a negative pressure state, and the upper and lower transparent plates 18
Since the outer surfaces of the upper and lower transparent plates 18a and 18b are in an atmospheric pressure state, the upper and lower transparent plates 18a and 18b act so as to press each other inward, and the substrate 16 sandwiched between the upper and lower transparent plates 18a and 18b and The photomasks 17a and 17b come into close contact with each other.

According to the exposure apparatus of this embodiment, the upper and lower transparent plates 18a,
Since a sealed space 29 for forming a negative pressure state between the opposing surfaces of the transparent plates 8b is formed, the central portions of the transparent plates 18a and 18b do not need to be sealed and may be open to the atmosphere. Become. Conversely, in order for the transparent plates 18a, 18b having a negative pressure between the opposing surfaces to adhere to each other, it is necessary to keep the outer surfaces of the upper and lower transparent plates 18a, 18b at atmospheric pressure. Therefore, the upper and lower frames 22a, 2
It is no longer necessary to dispose a fixed transmission layer such as a polymer film in the case of a conventional exposure apparatus in the exposure openings 21 and 2b of the exposure device 2b. 17a.

As a result, the number of factors causing scratches and dust on the ultraviolet transmitting layer is reduced, so that the defective rate of the wiring pattern due to these factors can be reduced. In particular, the fixed transmission layer that is left installed in the exposure apparatus can be omitted, and the ultraviolet transmission layer is only a transparent plate and a photomask that can be replaced as needed each time each substrate is exposed. growing.

Further, since the portion of the ultraviolet energy absorbed by the transmissive layer is reduced by one layer, the effective energy contributing to exposure can be increased, thereby shortening the exposure time. .

In the exposure apparatus of this embodiment, only the space 29 formed along the periphery of the circuit board forming unit 15 is evacuated. The space to be evacuated is smaller than in the case of evacuating the entire space where the transparent plate surrounded by the packing is disposed. Further, the lower transparent plate 18
b of the opening groove 20 and the exhaust hole 2 of the lower frame 22b
7 are close to each other, so that the exhaust power is reduced by the upper and lower transparent plates 18a, 1a.
8b easily reaches between the opposing surfaces. Therefore, a high negative pressure state can be established between the opposing surfaces of the upper and lower transparent plates 18a and 18b in a short evacuation time. That is, a high degree of adhesion between the substrate 16 and the photomasks 17a and 17b can be obtained in a short evacuation time.

The lower transparent plate 18b is provided with a groove 19 surrounding the substrate 16 and the photomasks 17a and 17b along the outer peripheral edge thereof, and an opening groove 20 with the photomasks 17a and 17b placed thereon.
When the space 29 is evacuated to vacuum, the gap between the opposing surfaces of the upper and lower transparent plates 18a and 18b through the opening groove 20 and the groove 19 is smaller than that of the substrate 16 and the photomasks 17a and 17b. A negative pressure state is ensured from all outer peripheral parts toward the central part. Therefore, the substrate 16 and the photomasks 17a and 17b can be uniformly adhered over the entire surface.

In this embodiment, each of the seal ridges forming the space 29 sealed at the peripheral edge of the circuit board forming unit 15 is formed by three rubber packings 23, 24, 2 and 3.
5 and one protruding wall 26, but any other members that can contact each other in an airtight state may be used in various combinations. In order to evacuate the space 29, the lower frame 22 is evacuated.
Although one exhaust hole 27 is provided at the center of one side of b, the number and position of the exhaust holes may be other. Further, in order to evacuate the space between the opposing surfaces of the upper and lower transparent plates 18a and 18b, a groove 19 surrounding the substrate 16 and the photomasks 17a and 17b is formed along the outer periphery of the lower transparent plate 18b.
And the opening groove 20 are formed, but the number, shape, and position of these grooves are different as long as they can be opened in the space 29 and the space between the opposing surfaces of the transparent plates 18a and 18b can be reliably evacuated. Or of course the upper transparent plate side may be used.

[0027]

According to the exposure apparatus for forming a circuit board of the present invention, the periphery of the circuit board forming unit protrudes into a space sealed by each sealing ridge, and both the circuit board forming unit are exposed by the opening for exposure. Atmospheric pressure acts on the outer surface of the circuit board forming unit, so that the two outer surfaces of the circuit board forming unit press inward each other, so that the substrate sandwiched inside the circuit board forming unit and the photomask can be brought into close contact with each other. it can. Therefore, it is not necessary to provide a layer such as a polymer film in the case of the conventional exposure apparatus, and it is possible to reduce the number of the ultraviolet light transmitting layer by one layer. As a result, the defect rate of the wiring pattern due to these factors can be reduced.

Further, since the amount of ultraviolet energy absorbed by the transmission layer is reduced by one layer, the effective energy contributing to exposure can be increased, and the exposure time can be shortened. .

Also, since the sealing ridge is used to seal the circuit board forming unit so as to surround only the peripheral edge, the space to be evacuated is reduced, and the circuit board forming unit is directly enlarged via the exposure opening. Since the atmospheric pressure is applied, the adhesion force does not depend on the characteristics of the polymer film as in the related art, and the circuit board forming unit, that is, the substrate and the photomask can always be stably adhered. .

Further, the outer peripheral edge of the substrate is reliably brought into a negative pressure state by the groove of the transparent plate surrounding the substrate and the communicating portion for opening the groove into the space. Therefore, the pressure between the opposing surfaces of the upper and lower transparent plates surely goes into a negative pressure state from all the outer peripheral edges of the substrate toward the center thereof. Thus, an effect of transferring the wiring pattern of the photomask to the substrate clearly can be achieved.

[Brief description of the drawings]

FIG. 1 is a perspective view showing one embodiment of an exposure apparatus for forming a circuit board of the present invention.

FIG. 2 is a cross-sectional view taken along line CC of FIG. 1 in a state where a circuit board forming unit is mounted on the apparatus of the embodiment.

FIG. 3 is a perspective view showing one embodiment of a circuit board forming unit of the present invention.

FIG. 4 is a side view illustrating a configuration of a circuit board forming unit.

FIG. 5 is a perspective view showing an example of a conventional exposure apparatus for forming a circuit board.

FIG. 6 is a cross-sectional view taken along line DD of FIG. 5 in a state where the circuit board forming unit is mounted on the apparatus of the same example.

[Explanation of symbols]

15: circuit board forming unit, 16: board, 17a, 1
7b: photomask, 18a: upper transparent plate, 18b: lower transparent plate, 19: groove, 20: open groove (communication part), 21:
Exposure opening, 22a: Upper frame, 22b: Lower frame, 23: Inner packing (first substrate seal ridge), 24: Outer packing (frame seal ridge),
25 ... lower packing (second substrate seal ridge), 26
... projecting wall (frame seal ridge), 27 ... exhaust hole, 2
9 ... space

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G03F ^7/ 20-7/24 G03F 9/00-9/02

Claims (1)

(57) [Claims] A photomask (17a, 17b) and a transparent plate (18) are provided on a photosensitive layer formed on the front and back surfaces of a substrate (16).
a, 18b) are superposed in this order, and a circuit board forming unit (15) is sandwiched between a pair of frames (22a, 22b). An exposure opening (21) is formed at a position corresponding to a portion where a photomask is disposed on the circuit board forming unit, and the first and second airtight contacts are made on both sides of a peripheral portion of the circuit board forming unit. A second board seal ridge (23, 25); and a frame seal ridge (24, 26) for hermetically sealing the two frames at a position outwardly separated from the peripheral edge of the circuit board forming unit. is provided, and at least one is of the frames, the being each sealed space formed between the ridges (29) in a negative pressure exhaust to the exhaust port (27) is formed, wherein Transparent plate (18a, 18b), the
These transparent plates are formed larger than the outer shape of the substrate (16).
At least one of these substrates along the outer edge of the substrate
And a groove (19) surrounding the space (29).
An exposure apparatus for forming a circuit board, wherein a communication part (20) for opening is formed .