JPH07838B2 - Method and apparatus for electrodeposition coating of photosensitive resin - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method and an apparatus for electrodeposition coating of a photosensitive resin, which is carried out as one step of an etching method for double-sided and multilayer printed wiring boards having through holes. Is.

[Prior Art] Conventionally, there is an electrodeposition coating process of a photosensitive resin in a method for etching a double-sided printed wiring board having through holes.

In this electrodeposition coating process, an insulating substrate such as a copper-clad laminated plate in which both front and back surfaces including through holes are coated with a conductive layer such as copper plating is used. In this case, the insulating substrate is immersed in a photosensitive resin solution in the electrodeposition tank, and in this state, a direct current is applied to the electrodeposition tank to apply the photosensitive resin to both the front and back surfaces including the through holes of the insulating substrate. The electrode coating is applied. After the electrodeposition coating process, the conductive layer of the insulating substrate is etched to form a double-sided printed wiring board.

[Problems to be Solved by the Invention] In the conventional electrodeposition coating process of the photosensitive resin, as described above, since the insulating substrate is simply immersed in the photosensitive resin solution,
If the through hole of the insulating substrate is a small diameter through hole of 0.5 mm or less, air may be trapped inside the small diameter through hole, or the photosensitive resin solution may not be filled into the small diameter through hole due to the surface tension or viscosity of the photosensitive resin solution. It was easy to complete, and it was difficult to coat the inner wall of the small-sized through hole with a coating film of a photosensitive resin uniformly by electrodeposition.
As a result, in the etching step performed after the electrodeposition coating, the inner wall of the through hole where the coating film of the photosensitive resin is not formed is corroded by the etching solution, which causes a fatal defect such as disconnection or defect of the inner wall of the through hole. was there.

This invention has been made to solve the above problems, and even if the through hole of the insulating substrate has a small diameter of 0.5 mm or less, it is possible to completely fill the small diameter through hole with the photosensitive resin solution. It is an object of the present invention to provide a method and apparatus for electrodeposition coating of a photosensitive resin, which is capable of uniformly electrodepositing a coating film of the photosensitive resin on both front and back surfaces of an insulating substrate including through holes in this state.

[Means for Solving Problems] A method and apparatus for electrodeposition coating a photosensitive resin according to the present invention is a photosensitive resin solution in which an insulating substrate having through holes and having both front and back surfaces covered with conductive layers is first dipped. After directly applying vibration, the insulating substrate is then immersed in another photosensitive resin solution which is isolated from the photosensitive resin solution, and current is applied to the conductive layer of the insulating substrate in the immersed state. It is configured in.

[Operation] In the method and apparatus for electrodeposition coating of photosensitive resin according to the present invention, the photosensitive resin solution in which the insulating substrate is first immersed is directly vibrated, the photosensitive resin solution vibrates and the insulating substrate resonates. By doing so, even if the through hole of the insulating substrate has a small diameter, the photosensitive resin solution is surely infiltrated into the through hole. Therefore, the trap air in the through hole can be expelled and removed by the vibrating photosensitive resin solution as described above, whereby the photosensitive resin solution ideally adheres to the through hole. Then, the insulating substrate is transferred and immersed in another photosensitive resin solution, and in the immersed state, by applying a current to the conductive layer of the insulating substrate, the front and back surfaces of the conductive layer including through holes of the insulating substrate are The coating film of the photosensitive resin solution is uniformly electrodeposited.

Here, the photosensitive resin solution in which the insulating substrate is first immersed is stored in an ultrasonic bath provided with an ultrasonic oscillator, and
The insulating resin drawn out from the photosensitive resin solution in the ultrasonic bath is then immersed.The photosensitive resin solution for electrodeposition is housed in the electrodeposition layer equipped with current applying means to isolate each photosensitive resin solution. Therefore, it is possible to fully operate the ultrasonic oscillator, which allows the step of infiltrating and contacting the photosensitive resin solution into the through hole of the insulating substrate (filling step),
The subsequent current application step (electrodeposition step) can be repeated at the same time. That is, while the insulating substrate pulled up from the photosensitive resin solution in the ultrasonic bath is immersed in the photosensitive resin solution in the next electrodeposition bath and current is applied, Subsequent insulating substrates can be immersed in the resin solution, which improves its processing efficiency.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, 1 is an insulating substrate, 2 is an ultrasonic tank, 3 is an electrodeposition tank isolated from the ultrasonic tank 2, and 4 is the ultrasonic tank 2 described above.
And a photosensitive resin solution 5 housed in each of the electrodeposition tanks 3, and 5 are stainless cathodes arranged in the electrodeposition tank 3 and immersed in the photosensitive resin solution 4 in the electrodeposition tank 3. A plate, 6 is an ultrasonic oscillator provided in the ultrasonic bath 2, and the ultrasonic oscillator 6 directly vibrates the photosensitive resin solution 4 in the ultrasonic bath 2. . Reference numeral 7 denotes an integrated processing tank (tank) including the ultrasonic tank 2 and the electrodeposition tank 3, and 8 and 9 are electrically connected to the conductive layer portion of the insulating substrate 1 and the cathode plate 5+, It is a means for applying a current.

The insulating substrate 1 has a through hole 10 as shown in FIG.
And a through-hole printed wiring board having both sides including the through-hole 10 and covered with a conductive layer 11 such as copper plating. The through-hole 10 is formed to have a hole diameter of, for example, 0.5 mm or less.

Next, the operation will be described.

First, when the insulating substrate 1 is first immersed in the photosensitive resin solution 4 in the ultrasonic bath 2 and the ultrasonic oscillator 6 is operated in the immersion state, ultrasonic vibration is generated in the photosensitive resin solution 4. When applied, the insulating substrate 1 resonates. As a result, the air trapped in the through hole 10 of the insulating substrate 1 is expelled and removed, and the photosensitive resin solution 4 ideally infiltrates and adheres into the through hole 10.

Next, the insulating substrate 1 is pulled up from the ultrasonic bath 2, and the insulating substrate 1 is moved to the next step.
Immersed in, and in the immersed state, current applying means 8,9
Thus, a direct current is applied with the conductive layers 11 on both front and back surfaces 1a and 1b of the insulating substrate 1 as positive electrodes and the cathode plate 5 made of stainless steel as a cathode. Then, as shown in FIG. 3, the conductive layer 11 is formed in the small-sized through hole 10 of the insulating substrate 1 and on both the front and back surfaces 1a and 1b.
A coating film 4a of a photosensitive resin is uniformly electrodeposited on the surface of the.

At the time of electrodeposition coating in the electrodeposition tank 3 as described above, by immersing a new insulating substrate 1 following in the photosensitive resin solution 4 in the ultrasonic tank 2 in the previous stage, A series of steps with the electrodeposition tank 3 can be continuously and repeatedly performed without interruption.

In the above examples, the electrodeposition coating method using the insulating substrate 1 side as the positive electrode was shown, but electrodeposition using the photosensitive resin solution deposited on the insulating substrate 1 side as the negative electrode (cathode) side A coating method may be used, and the same effect can be obtained even in this case.

[Effects of the Invention] As described above, according to the present invention, since the vibration is directly applied to the photosensitive resin solution in which the insulating substrate is first dipped, the vibration of the photosensitive resin solution and the resonance of the insulating substrate are caused. By this, trap air in the through hole of the insulating substrate can be expelled, and the photosensitive resin solution can be surely infiltrated and adhered into the through hole in place of the trap air.

Moreover, the insulating substrate after the photosensitive resin solution is attached to the through holes as described above is transferred and immersed in another photosensitive resin solution, and in the immersed state, a current is applied to the conductive layer of the insulating substrate. Therefore, the coating film of the photosensitive resin can be uniformly electrodeposited on both the front and back surfaces of the conductive layer including the through holes of the insulating substrate.

In particular, in the present invention, the photosensitive resin solution in the first stage is first dipped in the insulating substrate to give vibration, and the photosensitive resin solution in the latter stage is immersed in the photosensitive resin solution after the immersion in the next electrodeposition coating. Since the resin solution is isolated, the step of infiltrating and contacting the photosensitive resin solution into the through holes of the insulating substrate (filling step) and the subsequent current application step (electrodeposition step) can be simultaneously repeated. That is, while the insulating substrate pulled up from the photosensitive resin solution in the ultrasonic bath is immersed in the photosensitive resin solution in the next electrodeposition bath and current is applied, The subsequent insulating substrate can be dipped in the resin solution, which has the effect of significantly improving the processing efficiency.

Therefore, it is possible to prevent the inner wall of the through hole, the damage, etc. during the etching of the conductive layer of the insulating substrate performed after the electrodeposition coating of the photosensitive resin as described above, and the processing accuracy and reliability of the double-sided and the multilayer printed wiring board having the through hole. In addition to improving the property, it is possible to promote the reduction of the diameter of the through-holes, so that the density of the wiring pattern of the through-hole printed wiring board can be increased.

[Brief description of drawings]

FIG. 1 is a sectional view showing a method and apparatus for electrodeposition of a photosensitive resin according to an embodiment of the present invention, FIG. 2 is a partially enlarged sectional view of an insulating substrate before electrodeposition coating, and FIG. 3 is electrodeposition coating. It is a partially expanded sectional view of a later insulating substrate. 1: Insulation board, 1a, 1b: Both sides of insulation board, 2: Ultrasonic bath,
3: Electrodeposition tank, 4: Photosensitive resin solution, 4a: Electrodeposition coating film, 6: Ultrasonic oscillator, 8, 9: Current applying means, 10: Through hole, 11: Conductive layer.

Claims (4)

[Claims] 1. A photosensitive resin comprising a through hole, the front and back surfaces of which include the through hole are coated with conductive layers. In the electrodeposition coating method, the photosensitive resin solution in which the insulating substrate is first dipped is directly vibrated, and the photosensitive resin solution is shaken to bring the photosensitive resin solution into the entire through hole so as to come into contact therewith. After that, the insulating substrate is transferred and immersed in another photosensitive resin solution which is separated from the photosensitive resin solution, and in the immersed state, a current is applied to the conductive layer of the insulating substrate to form the conductive layer. 2. A method of electrodeposition coating a photosensitive resin, comprising forming a coating film of the above-mentioned photosensitive resin solution on both the front and back sides of the above. 2. The electrodeposition coating method for a photosensitive resin according to claim 1, wherein the vibration applied to the photosensitive resin solution is ultrasonic vibration. 3. A photosensitive resin having a through hole, wherein a front surface and a back surface of the conductive substrate of the insulating substrate having the front surface and the back surface including the through hole are coated with a conductive resin. In the electrodeposition coating apparatus, an ultrasonic bath containing the photosensitive resin solution in which the insulating substrate is first dipped and provided with an ultrasonic oscillator, and the photosensitive resin solution isolated from the ultrasonic bath. Is an electrodeposition tank containing another photosensitive resin solution, and an electric current is applied to the conductive layer of the insulating substrate immersed in the photosensitive resin solution in the electrodeposition tank to form the conductive layer containing the through holes. An electrodeposition coating apparatus for a photosensitive resin, comprising current applying means for electrodeposition coating the above-mentioned photosensitive resin solution on both front and back surfaces. 4. The photosensitive resin electrodeposition coating apparatus according to claim 3, wherein the ultrasonic bath and the electrodeposition bath are formed as partitions in one processing bath.