JPH0634440B2 - 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 in which aluminum wiring and copper wiring coexist.

(Prior Art) Conventionally, as a printed wiring board, a copper wiring formed on an insulating substrate has been the mainstream. However, recently, with the high density mounting of electronic components, printed wiring boards with aluminum wiring and copper wiring formed on the same substrate can be connected by wire bonding of semiconductor bare chips and soldering of other electronic components. Therefore, it came to be noticed and manufactured.

However, as a conventional method for manufacturing a 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 performed. It was previously taken. However, recently, there are many cases where an etching resist ink which is cured by ultraviolet rays is introduced into this etching resist because of high productivity of a printed wiring board.

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, as a manufacturing process of a printed wiring board having aluminum wiring and copper wiring, resist formation, aluminum etching, copper etching, resist removal, resist formation, aluminum etching,
There is resist removal.

Since a strong alkali is used for etching aluminum here, the above-mentioned alkali-removable ink cannot be used. Therefore, a solvent-removable heat-drying type etching resist ink has been usually used.

However, the solvent-removable, heat-drying type etching resist ink that has been conventionally used as an etching resist for this step and steps contains a solvent, and the solvent in this ink evaporates during printing, which causes the screen plate The ink viscosity above rises and the width of the printed wiring changes, and in the more significant case, the ink dries during printing, so transfer defects due to clogging of the screen and abnormal stretching of the screen occur. However, this has been a cause of defective 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 of them are copper etching resist inks, the alkali removal type is the mainstream and requires alkali resistance in the above process. It cannot be used as an etching resist for aluminum.

In addition to this, UV curable resist inks for plating have been developed, but since the chemical resistance is emphasized, the cured inks are highly crosslinked, and even if they can be removed with methylene chloride, they are the most common. 1,1,1-
It has the drawback that it cannot be removed with trichloroethane.

(Problems to be Solved by the Invention) The present invention could not be achieved by using such a heat-drying type etching resist ink and a conventional ultraviolet-curable ink.
Provided is a method for manufacturing a printed wiring board having aluminum wiring and copper wiring.

As a result of intensive investigations by the present inventors in view of the above drawbacks, the cured resist ink has excellent acid resistance and alkali resistance, and by using an ultraviolet curable etching resist ink that can be removed with 1,1,1-trichloroethane, The inventors have invented a method for manufacturing a printed wiring board having aluminum wiring and copper wiring, which has excellent productivity and few defects.

(Means for Solving the Problems) 1. On a surface of an aluminum foil of a printed wiring board on which an aluminum / copper composite foil is laminated 1) A step of screen-printing an acid-resistant and alkali-resistant ultraviolet-curable etching resist ink 2 Next, after the resist ink is cured with ultraviolet rays, the aluminum / copper composite foil is etched. 3) The etching resist ink cured product is removed with a chlorine-containing organic solvent having two carbon atoms as a main component to remove wiring. Step of forming pattern 4) Step of screen-printing an alkali-resistant ultraviolet curable etching resist ink on an arbitrary portion on the wiring pattern formed in steps 1) to 3) 5) Then, curing the resist ink with ultraviolet rays After that, a process of selectively etching the aluminum foil on the wiring pattern with a strong alkaline etching liquid (6) A method for producing a printed wiring board, which further comprises at least 6 steps of removing the cured product of the etching resist ink with a chlorine-containing organic solvent having two carbon atoms as a main component.

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 according to the present invention, a printed wiring board on which aluminum / copper composite foil is laminated is used. Examples of this aluminum / copper composite foil are a cladding foil of aluminum foil and copper foil, a foil in which copper is plated on the aluminum foil, and a foil in which dissimilar metal plating is applied between the aluminum foil and the copper plating foil. .

As a substrate material for bonding 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, and as necessary. The composite foil is bonded with an adhesive.

Further, as the substrate material, there are metal materials such as aluminum, iron, and stainless steel, and for the printed wiring in which the composite foil is laminated by joining the above-mentioned composite foil with an adhesive such as an epoxy resin while maintaining insulation. The substrate can be made.

Next, the first step referred to in the present invention is to screen print an acid- and alkali-resistant ultraviolet-curable etching resist on the aluminum foil surface of the printed wiring board described above. Further, it is preferable that the surface of 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 acid-resistant and alkali-resistant UV-curable etching resist ink used in this step is such that the cured resist resists the strong alkaline etching liquid used in the etching of aluminum foil, and the strong acid copper etching after the aluminum etching. The resist hardened by the liquid resists, and the resist after being exposed to the aluminum etching liquid and the copper etching liquid is often used industrially and has low toxicity.
It needs to be removable with 1,1-trichloroethane.

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 acid esters, etc.) and talc, etc. There are inorganic fillers, and further, those containing at least four components of a photosensitizer as main components.

Next, in the second step referred to in the present invention, the resist ink is cured with ultraviolet rays, and then the aluminum foil is etched into a wiring pattern with a strongly alkaline etching liquid, and the resist is further removed without removing the resist. This is a step of etching a copper foil other than the aluminum wiring with a selective etching agent that etches only copper.

The ultraviolet curing in this step can be performed 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 metal halide lamp. The lamp is selected according to the absorption wavelength of the photosensitizer contained in the ultraviolet curable etching ink.

In addition, the etching of the aluminum foil in this step is carried out by adding various additives to an aqueous solution of an inorganic strong alkaline compound such as caustic soda and caustic potash. It is in.

The concentration of this strongly alkaline inorganic compound is 5 to 30% by weight. The etching liquid is usually 40 ° to 70 ° C. in order to reduce the viscosity of the liquid to facilitate spraying during etching and to increase the etching speed.
Used by heating to. If the concentration of the strongly alkaline inorganic compound is less than 5% by weight, the etching speed is slow even when heated, and if it exceeds 30% by weight, the liquid becomes highly viscous even if heated and uniform spraying becomes difficult.

Next, without etching the aluminum foil used in this step,
As a selective etching agent for selectively etching only the copper foil, a sulfuric acid-hydrogen peroxide type etching agent or an aqueous solution of persulfate of ammonium persulfate or sodium persulfate is used.

The third step of the present invention is to remove the resist ink by cleaning the etching resist-attached substrate after the second step with a chlorine-containing organic solvent whose main component is 2 carbon atoms. It is in. Here, the chlorine-containing organic solvent having two carbon atoms means 1,1,1-trichloroethane,
Such as trichlorethylene and tetrachloroethylene,
From the point of toxicity, 1,1,1-trichloroethane is preferable.

The fourth step of the present invention is a step of screen-printing an ultraviolet-curable etching resist ink having at least alkali resistance on the wiring pattern formed in steps 1-3. The UV-curable etching resist ink used here can be the acid-resistant / alkali-resistant UV-curable etching resist ink used in the process as it is, or the alkali-resistant type UV-curable etching resist ink. Good.

In the fifth step of the present invention, after the resist ink is cured by ultraviolet rays, the aluminum foil of the wiring pattern is selectively etched in a pattern form as necessary with the strongly alkaline aluminum etching liquid used in the second step. is there. Through this step, the copper foil is formed in a pattern, and the copper wiring portion that can be used for the soldering portion is formed.

Further, the sixth step of the present invention is to remove the etching resist ink with a chlorine-containing organic solvent having two carbon atoms as a main component, which is the same resist removal step as the third step of the present invention. .

The printed wiring board in the present invention is usually subjected to mechanical processing such as solder register formation and press punching as post processing.

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

Example 1 The size shown in FIG. 1 is 200 × 200 mm and the thickness is 1.0 mm.
For a printed wiring in which a composite foil of 40 μm aluminum foil 4 and 10 μm copper foil 3 is bonded on the aluminum plate 1 through an epoxy resin insulating layer 2 having a thickness of 80 μm with the surface of the aluminum foil 4 facing up. 200 substrates were used.

First, the aluminum on the back surface of the substrate was protected by a film 5 with an adhesive so as not to be attacked by the etching liquid (Fig. 1).
After degreasing the aluminum foil 4 surface with an alkaline degreasing agent, 200 sheets were continuously printed by an automatic printing machine using acid- and alkali-resistant acrylic UV-curable etching resist ink 6 (FIG. 2). The screen plate used for this printing was a polyester screen of 300 mesh, and the pattern used was four L-shaped wirings with the same line width and line spacing of 50 μm each thickened by 50 μm. It is arranged in 10 rows and 10 columns in a size of × 200 mm (the maximum line width is 300 μm). The increase in ink viscosity was about 10% after printing 200 sheets. (Hereinafter, what is in the process of forming a circuit on a printed wiring board and finally forming a printed wiring board is called a board.) The printed board has a conveyor speed of 4.0 m / mm immediately, It 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. A line width with a design width of 250 μm was measured for every 50th sheet, and it was within a range of 270 μm ± 15 μm, and stable printing was achieved.

Next, a strong alkaline aqueous solution containing 20% by weight of caustic soda and the like was added to 6 UV-cured etching resist-coated 6 substrates.
After spraying for 2 minutes at 0 ° C., the aluminum foil 4 of the composite foil was etched in a pattern to obtain an aluminum wiring 8 (FIG. 3). Then, the substrate was washed with water and dried, and then 20% by volume of sulfuric acid, which is a selective etching agent for copper, and 10% by volume of PermaEtchi (trade name of Ebara Densan Co., Ltd., containing 5% by weight of hydrogen peroxide) were mixed. The copper wiring 7 was obtained by spray etching with an etching liquid at 54 ° C. for 1 minute, followed by washing with water and drying (FIG. 4).

Then, the etching resist 6 was peeled off by spraying 1,1,1-trichloroethane at room temperature, which is the third step of the present invention (FIG. 5). Microscopic inspection of the obtained wiring having a wiring width of 250 μm of the aluminum wiring 8 showed no harmful traces of resist peeling during etching, and no resist remained on the wiring.

Next, as a fourth step, the finished aluminum wiring 8 is formed.
Using the same screen plate, the same wiring pattern, and the same UV-curable etching resist ink 6 as above, the etching resist ink 6 was continuously printed on 200 substrates so that the wiring patterns were partially orthogonal (FIG. 6). .

The printed substrate was immediately passed through an ultraviolet curing device to cure the resist ink 6. The cured resist ink 6 is
As a result of inspection with a microscope, no harmful disconnection or bleeding was found in the resist-in 6 in the portion orthogonal to the aluminum wiring 8 having a thickness of 40 μm.

Next, the UV-cured substrate with the etching resist 6 is treated with a strong alkaline aqueous solution containing 20% by weight of caustic soda and the like.
The aluminum wiring 8 of the composite foil was etched in a pattern by spraying at 2 ° C. for 2 minutes (FIG. 7). After that, the substrate was washed with water and dried, and 1,1,1-trichloroethane was sprayed at room temperature to remove the etching resist 6 (eighth embodiment).
Figure).

Microscopic examination of the finally obtained mixed wiring consisting of the aluminum wiring 8 and the copper wiring 7 with a wiring width of 250 μm showed no harmful resist peeling during etching, and no resist remained on the wiring.

Comparative Example 1 Using the same printed wiring board as in Example 1, MR-500 (manufactured by Asahi Kaken Co., Ltd.) having strong alkali resistance with a heat-drying type resist ink was used as the first step for screen printing. When 200 sheets were continuously printed in the same manner as in Example 1, ink was poorly discharged in printing up to the 10th sheet. Further, although good printing was achieved on the 50th to 100th sheets, 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 aluminum and copper under the same conditions as in Example 1 and removing the resist with 1,1,1-trichloroethane, no abnormal resist peeling during etching was found.

Next, the same process as in the fourth step of Example 1 was carried out by using an ultraviolet curing type etching resist ink as a heat drying type resist ink M.
R-500 (manufactured by Asahi Kaken Co., Ltd.) was used. As a result, an increase in the viscosity of the ink was observed as in the first step, and partial blurring was observed in the printed wiring pattern of the resist ink. Then, as a fifth step, the aluminum foil is etched in the same manner as in Example 1, and 1,1,1-
The resist was removed with trichloroethane. The part where the resist was faint was etched with an aluminum foil, resulting in a defective printed wiring board.

(Effects of the Invention) As described above, the present invention is a printed wiring board having an aluminum wiring and a copper wiring, which uses an ultraviolet curing type etching resist ink whose cured film has acid resistance and alkali resistance and solubility in a special solvent. And has high productivity and reliability.

[Brief description of drawings]

1 to 8 are schematic views for explaining the manufacturing process of the printed wiring board in Example 1, FIGS. 1 to 5 are partially enlarged cross-sectional views, and FIGS. 6 to 8 are partial views. It is an enlarged plan view. Reference numeral 1 ... Aluminum plate 2 ... Insulating layer 3 ... Copper foil 4 ... Aluminum foil 5 ... Protective film 6 ... Etching resist ink 7 ... Copper wiring 8 ... Aluminum wiring

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP 61-284991 (JP, A) JP 55-30840 (JP, A) JP 61-276394 (JP, A) JP 54- 122878 (JP, A) Japanese Patent Sho 47-33642 (JP, B1)

Claims (2)

[Claims] 1. A step of screen-printing an acid-resistant and alkali-resistant ultraviolet-curable etching resist ink on an aluminum foil surface of a printed wiring board on which an aluminum / copper composite foil is laminated. Step of etching aluminum / copper composite foil after being cured with ultraviolet rays 3) Step of removing the etching resist ink cured material with a chlorine-containing organic solvent having two carbon atoms as a main component to form a wiring pattern 4 ) Screen-printing an alkali-resistant UV-curable etching resist ink on an arbitrary portion on the wiring pattern formed in steps 1) to 3) 5) Next, after the resist ink is cured with ultraviolet rays, it is strongly alkaline. Selective etching of aluminum foil on the wiring pattern with the etching solution of 6) And at least 6 steps of removing the etching resist ink cured product with a chlorine-containing organic solvent having 2 carbon atoms. 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.