JPH0634439B2 - Method for manufacturing printed wiring board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention uses an ultraviolet-curable etching resist,
The present invention relates to a method for manufacturing a printed wiring board having aluminum wiring.

(Prior Art) Conventionally, as a printed wiring board, conventionally, a copper wiring formed on an insulating substrate is mainstream. However, recently, with the high density mounting of electronic parts, a printed wiring board having aluminum wiring or having aluminum wiring and copper wiring formed on the same substrate has attracted attention because it can be connected by wire bonding of semiconductor chips. , Has come to be manufactured.

And as a method for manufacturing a conventional printed wiring board having copper wiring, a method of forming a heat-drying type etching resist on a copper clad laminate by screen printing, performing etching of copper, and then removing the etching resist is a method. Had been taken. However, in recent years, the etching resist ink in which the etching resist is cured by ultraviolet rays is often introduced to increase the productivity of printed wiring boards. Further, these heat-drying type and ultraviolet ray-curing type etching resists have conventionally been mainly solvent-removing type, but recently alkali-removing type ink is often adopted from the viewpoint of low running cost and pollution prevention. I'm running.

On the other hand, in a printed wiring board having this aluminum pattern, since a strong alkali is used for etching aluminum, this type of alkali removal type ink cannot be used. Therefore, a solvent-removable heat-drying type etching resist ink has been usually used.

However, the solvent-drying type heat-drying type etching resist ink that has been used as an aluminum etching resist contains a solvent, and the solvent in this ink evaporates during printing, resulting in an ink viscosity on the screen plate. The width of the printed wiring may rise and the width of the printed wiring may change. In more significant cases, the ink dries during printing, resulting in transfer defects due to clogging of the screen, abnormal screen elongation, etc. However, this has been a cause of poor printing.

Since it is necessary to suppress the evaporation of the solvent in the ink, the solvent in the ink is replaced with a high boiling point solvent, but it is necessary to raise the drying temperature and lengthen the drying time, which lowers the productivity. There was a drawback.

Ultraviolet curing type etching resist inks have been developed for the purpose of solving these various drawbacks, but since all are copper etching resist inks, alkali removal type is the mainstream, and alkali-resistant aluminum is required. It could not be used as an etching resist.

In addition to this, an ultraviolet curable resist ink for plating has been developed, but since the chemical resistance is emphasized, the cured ink is highly crosslinked, and even if it can be removed with methylene chloride, it is the most Commonly used 1,1,1
-It has the drawback that it cannot be removed with trichloroethane.

(Problems to be Solved by the Invention) The present invention has been unsuccessful in using such a heat-drying type etching resist ink and a conventional UV-curable ink.
The present invention provides a method for producing a printed wiring board having aluminum wirings. As a result of intensive investigations by the present inventors in view of the above-mentioned drawbacks, the cured resist ink has excellent alkali resistance and 1,1,1-trichloroethane. The inventors have invented a method for producing a printed wiring board having aluminum wiring, which is excellent in productivity and has few defects, by using an ultraviolet-curable etching resist ink that can be removed by.

(Means for Solving the Problems) 1. On the aluminum foil surface of a printed wiring board on which an aluminum foil or an aluminum / copper composite foil is laminated, 1) a step of screen-printing at least an alkali-resistant ultraviolet-curable etching resist ink 2) Next, after the resist ink is cured with ultraviolet rays, a step of etching the aluminum foil in a pattern with a strong alkaline etching solution 3) Further, with a chlorine-containing organic solvent having two carbon atoms as a main component, A method for manufacturing a printed wiring board, comprising at least three steps of removing a resist ink cured product.

Next, the method for manufacturing a printed wiring board of the present invention will be described in more detail.

In order to form the aluminum wiring pattern according to the present invention, a printed wiring board on which aluminum foil or aluminum / copper composite foil is laminated is used. An example of this aluminum / copper composite foil is a cladding foil of aluminum foil and copper foil, a foil in which copper is plated on the aluminum foil, or a foil in which a dissimilar metal plating is applied between the aluminum foil and the copper plating foil. is there.

As a substrate material for joining these composite foils, there are organic materials such as phenol resin, epoxy resin, polyimide resin, polyester resin, or composite materials in which glass fibers or fillers are filled in these organic materials. Bonding to the composite foil with an adhesive.

Further, as the substrate material, there are metal materials such as aluminum, iron, and stainless steel, and a printed wiring board in which composite foils are laminated by bonding the composite foils with an adhesive such as an epoxy while maintaining insulation Can be made.

Next, the first step referred to in the present invention is to screen-print at least an alkali-resistant ultraviolet-curable etching resist on the aluminum foil surface of the above-mentioned printed wiring board. Further, it is preferable that the aluminum foil surface is subjected to a surface treatment by degreasing, buffing or the like prior to the screen printing in order to secure the adhesion reliability with the etching resist. The degreasing method may be alkali degreasing, acid degreasing, or solvent degreasing, which is usually used when degreasing an aluminum surface.

The at least alkali-resistant ultraviolet-curable etching resist used in this step may be any type of alkali resistance or acid resistance and alkali resistance,
The hardened resist can withstand a strong alkaline etching solution used for etching aluminum foil, and the hardened resist is often used industrially and can be removed with 1,1,1-trichloroethane, which has low toxicity. Will be needed.

Examples of UV-curable etching resist inks that can be used for this purpose include monofunctional oligoester acrylates (for example, Etc. Here, n is usually 1 to 3, but is not particularly limited. Also, those having an alkyl substituent in the benzene nucleus can be used. ) And 1,1,1-trichloroethane-soluble and acid- and alkali-resistant oligomers or polymers (for example, methyl methacrylate oligomers, alkyd resins, copolymers of styrene and acrylic ester, etc.) and talc, etc. There are inorganic fillers, and further, those containing at least four components of a photosensitizer as main components.

Next, the second step referred to in the present invention is a step of curing the resist ink with ultraviolet rays and thereafter etching the aluminum foil into a wiring pattern with a strongly alkaline etching liquid. The ultraviolet curing in this step can be carried out in a commercially available ultraviolet irradiation furnace equipped with an ultraviolet lamp such as a high pressure mercury lamp, an ultrahigh pressure mercury lamp, and a Haltal halide lamp. The lamp is selected according to the absorption wavelength of the photosensitizer contained in the ultraviolet curable etching ink.

Further, the etching of the aluminum foil in this step is performed by adding various additives to an aqueous solution of an inorganic strong alkaline compound such as caustic soda and caustic potash. To be an agent. The concentration of this strongly alkaline inorganic compound is 5 to 30% by weight. The etching liquid is usually heated to 40 ° to 70 ° C. for the purpose of decreasing the viscosity of the liquid to facilitate spraying during etching and increasing the etching speed. If the concentration of this strongly alkaline inorganic compound is less than 5% by weight, the etching speed is slow even if heated, and if it exceeds 30% by weight, the liquid has a high viscosity even if heated and it is difficult to spray uniformly. Become.

Further, the third step in the present invention is the substrate before the etching resist is removed after the second step (hereinafter, the circuit is formed on the printed wiring board, and finally the printed wiring board is formed. What is in the process of is called a substrate)
The main purpose is to remove the resist ink by washing with a chlorine-containing organic solvent having a main component of 2 carbon atoms. Here, the chlorine-containing organic solvent having two carbon atoms means 1,1,1
-Trichloroethane, trichloroethylene, tetrachloroethylene and the like, and 1,1,1-trichloroethane is preferable from the viewpoint of toxicity.

In the method for manufacturing a printed wiring board according to the present invention,
It is necessary to include at least the above three steps, but as the subsequent steps, for example, when an aluminum foil-clad substrate is used, there is formation of a soldering portion by copper plating,
When the aluminum / copper composite foil-clad substrate is used, a step of forming a copper etching resist and then selectively etching only copper with an aqueous solution of ammonium persulfate or a sulfuric acid-hydrogen peroxide type etching agent to form a pattern can be mentioned.
In addition, the formation of the solder resist is usually performed as a post process in many cases.

(Example) Next, the Example of this invention is described.

Example 1 A composite foil of 40 μm aluminum and 10 μm copper was placed on an aluminum plate having a size of 200 × 200 mm and a thickness of 1.0 mm with an epoxy-based insulating layer having a thickness of 80 μm on the aluminum side. 200 printed wiring boards that were joined together were used.

First, the aluminum on the back surface of the substrate was protected by a polymer film with an adhesive so that the etching liquid was not attacked. After degreasing the aluminum foil surface with an alkali degreasing agent, 200 sheets were continuously printed with an automatic printing machine using an acid- and alkali-resistant acrylic UV-curable etching resist ink. The screen plate used for this printing was a 300 mesh polyester screen, and the pattern used was a minimum line width of 50 μm, which was thickened by 50 μm, and four L-shaped wires with the same line width and spacing were 200 × 200 mm. Arranged in 10 rows and 10 columns (maximum line width is 300μ
m). The increase in ink viscosity was about 10% after printing 200 sheets.

The printed substrate had a conveyor speed of 4.0 m / min immediately and was put into an ultraviolet irradiation device equipped with a high pressure mercury lamp of 80 W3 and cured. The time required from printing to resist curing was 40 minutes.

As a result of inspecting the substrate on which the resist was cured with a microscope, the resolution of the pattern was very good, and 150 μm lines could be resolved. Moreover, there were no defects such as clogging of the screen. When the line width of the design width of 250 μm was measured for every 50th sheet, it was within the range of 270 μm ± 15 μm, and stable printing was achieved.

Then, a UV-cured substrate with an etching resist was sprayed with a strongly alkaline aqueous solution containing 20% by weight of caustic soda for 2 minutes at 60 ° C. to etch the aluminum foil of the composite foil in a pattern. Then, the substrate was washed with water and dried, and 1,1,1-trichloroethane was sprayed at room temperature to remove the etching resist.

Microscopic inspection of the finally obtained aluminum wiring showed no harmful resist peeling during etching, and no resist remained on the wiring.

Example 2 Using the same screen plate, the same wiring pattern, and the same UV-curable etching resist ink as used in Example 1 on the aluminum wiring completed in Example 1, the wiring patterns were made to be partially orthogonal to each other. The etching resist ink was continuously printed on 200 substrates.

The printed substrate was passed through an ultraviolet curing device in the same manner as in Example 1 to cure the resist ink. As a result of inspecting the cured resist ink with a microscope, no harmful disconnection or (FIG. 1) or bleeding (FIG. 2) was found in the resist ink in the portion orthogonal to the aluminum wiring having a thickness of 40 μm.

Next, a substrate with an etching resist that has been ultraviolet-cured is treated with sulfuric acid 2
Spray etching was performed at 54 ° C. for 1 minute with an etching agent consisting of 0% by volume and 12% by volume of PermaEtchi (trade name of Ebara Densan Co., Ltd .: containing 50% by volume of hydrogen peroxide as a main component). Then, the substrate was washed with water and dried, and 1,1,1-trichloroethane was sprayed at room temperature to remove the etching resist.

Microscopic inspection of the finally obtained mixed wiring consisting of aluminum wiring and copper wiring showed no harmful stripping of the resist during etching, and no resist remained on the wiring.

Comparative Example 1 Using the same printed wiring board as in Example 1, screen-printing was carried out using MR-500 (manufactured by Asahi Kaken Co., Ltd.) having a strong alkali resistance with a heat-drying type resist ink.
When 200 sheets were continuously printed in the same manner as above, the ink did not come out well in the printing up to the 10th sheet. 50 to 10
Good printing was achieved on the 0th sheet, but ink fading started to appear on the 100th and subsequent sheets. The increase in the viscosity of the ink after printing was about 200%.

Next, after drying with a blast dryer for 10 minutes at 110 ° C., the printed wiring was inspected with a microscope. As a result, the wiring width that could be resolved even with a well printed board was 200 μm minimum, and with other boards, ink There was a lot of fading, and some wirings were broken on bad boards.

The time required from printing to drying was 60 minutes, but in the actual manufacture of printed wiring boards, if ink fading occurs, it will not be a product, so stop printing
Since the plate is wiped with a solvent, the working time is significantly increased and the productivity is reduced.

In the inspection after etching under the same conditions as in Example 1, no abnormal resist peeling occurred during etching.

(Effect of the invention) As described above, the present invention is a method for producing an aluminum wiring using a UV-curable etching resist ink in which a cured film has alkali resistance and solubility in a special solvent,
It has both high productivity and high reliability.

[Brief description of drawings]

FIG. 1 is a partially enlarged cross-sectional view of a printed wiring board for explaining harmful wiring disconnection in the second embodiment. Also, FIG. 2 is a partially enlarged plan view showing harmful bleeding of the etching resist ink printed on the step portion in the same manner as in the second embodiment. Reference numeral 1 ... Aluminum plate 2 ... Insulation layer 3 ... Copper foil 4 ... Aluminum wiring 5 ... Resist ink 6 ... Breakage due to etching 7 ... Bleed portion

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-59-33894 (JP, A) JP-A-61-284991 (JP, A) JP-A-55-30840 (JP, A) JP-A-61- 276394 (JP, A) JP 54-122878 (JP, A) JP 47-33642 (JP, B1)

Claims (3)

[Claims] 1. A step of screen-printing at least an alkali-resistant ultraviolet-curable etching resist ink on an aluminum foil surface of a printed wiring board on which an aluminum foil or an aluminum / copper composite foil is laminated. Step of etching the aluminum foil in a pattern with a strong alkaline etching solution after it is cured with ultraviolet rays 3) Further, the resist ink cured product is removed with a chlorine-containing organic solvent having two carbon atoms as a main component A method for manufacturing a printed wiring board, which comprises at least three steps. 2. The method for manufacturing a printed wiring board according to claim 1, wherein the printed wiring board is laminated on at least one main surface of the metal plate with an insulating layer interposed therebetween. 3. The ultraviolet curable etching resist ink cured product is resistant to an etching solution containing 5 to 30% by weight of caustic soda as a main component and can be removed with 1,1,1-trichloroethane. The method for manufacturing a printed wiring board according to item 1.