JP2003283111A - Method for cleaning printed wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for cleaning a printed wiring board by which the quality and productivity of the board can be improved by efficiently removing residual photosensitive solder resist on the electrode terminals of the printed wiring board. <P>SOLUTION: In the method for cleaning the printed wiring board, with respect to a horizontal conveyer system for developing the photosensitive solder resist ink on the printed wiring board, an ultrasonic vibrator (6) is immersed in a cleaning bath (4) placed at the cleaning stage after the development. Cleaning water is sprayed from a spray tube (7) between the ultrasonic vibrator (6) and a substrate (12) for the printed wiring board. The sprayed cleaning water is sucked and filtered through a suction tube (8) and is circulated for cleaning. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaning a printed wiring board substrate after development of a photosensitive solder resist ink.

[0002]

2. Description of the Related Art Generally, a printed wiring board is covered with an insulating material except for electrode terminals provided for electrical connection in a conductive circuit portion formed on an insulating substrate. As these insulating materials, a thermosetting ink called a solder resist and an insulating film with an adhesive layer called a coverlay are usually used. The solder resist ink masks the screen plate in advance so that the electrode terminal portions are not printed, and the coverlay has the electrode terminal portions punched out in advance with a mold or the like. However, as electronic devices have become smaller, lighter, and more sophisticated in recent years, higher density and finer pitch are also required in the openings of the coating of the printed wiring board, and ink bleeding occurs in screen printing. ,
Since it is difficult to make a fine pitch in the die by die punching, a photosensitive solder resist ink is generally used in many cases.

The photosensitive solder resist ink is printed on the entire surface with an insulating coating material that uses both ultraviolet curing and heat curing, and is then semi-cured by a low-temperature heat treatment called precure. Is exposed to ultraviolet rays to be cured by ultraviolet rays, and the resist in the uncured portion of the electrode terminal portion is dissolved and removed by an alkaline water-soluble developer, and the remaining coated portion is post-cured by high temperature heat treatment to be completely cured. As described above, since the photomask pattern can utilize the ordinary fine line processing technique for circuit production as it is, it is possible to perform coating corresponding to high density and fineness.

However, when such a photosensitive solder resist ink is used, it is necessary to apply it to the entire surface and remove unnecessary portions, so that there are various variations in each processing step, that is, surface roughness of printed conductor circuits. Variation in resist ink, variation in coating thickness during printing, variation in temperature distribution during pre-cure, variation in exposure amount during exposure, variation in chemical concentration during development, variation in pressure distribution of developer spray, etc. This has caused variations in the properties, and has been a cause of leaving fine resist residues on the electrode terminals. These are major causes of non-precipitation of plating, poor appearance of plating, and deterioration in reliability of electrical connection, especially in a printed wiring board having high density and fine pitch fine electrodes.

When the resist residue is completely cured by post-cure, it has excellent chemical resistance and adhesiveness.
Chemical and physical removal becomes very difficult. Therefore, at present, a cleaning method has been proposed in which an ultrasonic device is provided in a developing tank or a cleaning tank after development to remove the resist residue. However, in this cleaning method, the resist residue that has been separated and floated by ultrasonic waves adheres to the printed wiring board again, and the oscillation frequency of the ultrasonic vibrator is lowered more than necessary to prevent re-adhesion, and the solder resist and conductor There were problems such as peeling and damage of the circuit.

[0006]

SUMMARY OF THE INVENTION The present invention provides a method for cleaning a printed wiring board for the purpose of efficiently removing the photosensitive solder resist residue on the electrode terminals of the printed wiring board and improving quality and productivity. To do.

[0007]

The present invention provides [1] a horizontal conveyor device for developing a photosensitive solder resist ink on a printed wiring board, wherein an ultrasonic transducer is installed in a washing water tank installed in a washing step after development. A print characterized by being soaked, sprayed with rinsing water from a spray pipe between the ultrasonic vibrator and a substrate for a printed wiring board, sucking the sprayed rinsing water from a suction pipe to filter, and then circulating washing. A method for cleaning a wiring board, [2] a method for cleaning a printed wiring board substrate according to the item [1], wherein the cleaning is performed at an oscillation frequency of the ultrasonic oscillator of 100 to 600 KHz for 10 seconds or more.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below with reference to the drawings, but the invention is not limited thereto. The developing device for the photosensitive solder resist ink used in the present invention is a horizontal conveyor, and can be applied to either sheet-fed processing or roll-to-roll processing. The treatment process of the photosensitive solder resist ink comprises a treatment tank for development, washing with water and drying. As the developing solution, a general alkaline aqueous solution may be used, and if necessary, a pickling treatment tank for alkali neutralization may be added. The water washing step is preferably a plurality of water washing steps in order to avoid contamination of the printed wiring board by bringing in a developing solution or a neutralizing solution, and a multi-bath water washing method of four or more tanks is particularly preferable. For printed wiring boards that require further cleanliness, install a washing process that performs ultrasonic cleaning in a washing process other than the final washing process so that the final process can be rinsed with ultrapure water. Is preferred.

FIG. 1 is a conceptual diagram of the ultrasonic cleaning process of the developing device. The cleaning water is stored in the sub-tank (1), pumped up to the cleaning tank (4) through the filter (3) by the circulation pump (2), the pass line (5) of the horizontal conveyor, the ultrasonic transducer for ultrasonic cleaning. (6) The spray pipe (7) and the suction pipe (8) are filled with rinsing water until they are completely immersed. In this cleaning tank, the drainage pipe (9) that returns from the bottom of the cleaning tank to the sub tank is installed so that the collected cleaning water circulates so that it overflows and returns to the sub tank, and dirt is not accumulated in the cleaning tank. It is desirable to have it. Here, the spray pipe and the suction pipe are a jet pump (10) and a jet filter (1) for filtration.
1), the ultrasonic transducer is arranged in the center of the cleaning tank, the spray pipe is installed in front of the traveling direction of the conveyor, and the suction pipe is installed in the rear of the traveling direction of the conveyor. This is preferable because the peeling efficiency is good, but
The spray pipe and the suction pipe may be arranged in reverse with respect to the traveling direction of the conveyor.

In this state, the jet pump (10) is circulated while transmitting ultrasonic waves. Cleaning water is sprayed from the nozzle of the spray pipe to the space between the ultrasonic vibrator and the printed wiring board (12). The sprayed cleaning water is
When most of the material passes between the ultrasonic transducer and the printed wiring board in the traveling direction of the conveyor, most of the material is sucked from the suction nozzle of the suction pipe, filtered, and then sprayed again and circulated. Here, the flow rate of the jet pump and the angle of the spray nozzle are adjusted so that the printed wiring board does not get caught by the conveyor or ultrasonic transducer, and that the circuit of the printed wiring board or the solder resist does not peel off. It is preferable to be able to do so.
The shape of the spray and suction nozzles is not particularly limited, but any structure such as a fan shape, a line shape, or a band shape that covers the entire surface of the solder resist of the printed wiring board and does not burden the jet pump can be used. Good.

The ultrasonic vibrator is protected by a corrosion resistant metal,
As long as the surface is smooth and can cover the entire surface of the printed wiring board, it may be used alone or divided. Considering the adverse effect on the photosensitive solder resist, which has weak adhesiveness before post-cure, the ultrasonic wave transmission frequency is 100 to 600, which is less likely to cause peeling or damage to the solder resist or the conductor circuit.
The frequency is preferably set to KHz, and in order to obtain a sufficient cleaning effect in this frequency range, the distance between the ultrasonic transducer and the printed wiring board is preferably 1 to 20 mm, and 10
A processing time of at least 2 seconds, more preferably 10 to 30 seconds is desirable. The developed printed wiring board is subjected to ultrasonic vibrations on the surface of the printed wiring board as it passes under the ultrasonic vibrator, and is also subjected to washing water in the same traveling direction. At this time, the unstable resist residue remaining on the electrode terminals of the printed wiring board is forcibly peeled off, and
It is swept away and sucked by the suction nozzle at the exit of the ultrasonic transducer.

[0012]

According to the present invention, in the cleaning process of the photosensitive solder resist ink, neither the cured resist nor the electrode terminal circuit is peeled off, and the resist residue is not redeposited. A residue can be removed by washing, and a printed wiring board using a clean and excellent photosensitive solder resist ink can be obtained.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of an ultrasonic cleaning process of a horizontal conveyor developing device of the present invention.

FIG. 2 is a conceptual diagram of an ultrasonic cleaning process of a conventional horizontal conveyor developing device.

[Explanation of symbols]

1 sub tank 2 circulation pump 3 filters 4 washing water tank 5 Conveyor pass line 6 Ultrasonic transducer 7 spray piping 8 Suction piping 9 Drainage piping 10 Jet pump 11 Jet filter 12 Printed wiring board

Claims (2)

[Claims] 1. In a horizontal conveyor device for developing a photosensitive solder resist ink on a printed wiring board, an ultrasonic vibrator is immersed in a cleaning water tank installed in a cleaning step after development, and the ultrasonic vibrator and the printed wiring are connected. A method for cleaning a printed wiring board, which comprises spraying rinse water between a board for a board and a spray pipe, sucking the sprayed rinse water through a suction pipe, filtering and then circulating cleaning. 2. The cleaning is carried out at an ultrasonic oscillator oscillation frequency of 10.
The method for cleaning a printed wiring board substrate according to claim 1, which is performed at 0 to 600 KHz for 10 seconds or more.