JPH11289150A - Manufacture of printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the manufacturing cost of a printed wiring board, by saving the copper resource which comes to nothing, in such a way that the recess of a recessed circuit pattern formed on the surface of a base material is filled up with a mixture of permanent magnet powder and a liquid resin, the mixture is heated after the magnet powder is oriented in the direction of axis of magnetization in a magnetic field, then, nickel particles are scattered on the pattern and oriented in a magnetic field, and the nickel particles are transferred to a substrate and plated with copper. SOLUTION: After a recessed circuit pattern is formed on a base material 1 by using a positive film, the recess of the pattern is filled up with a mixture 2 of an epoxy-based adhesive and permanent magnet powder composed of barium ferrite, and the mixture 2 is hardened in a magnetic field provided with heating plates on the top side and bottom side. Then, nickel particles are evenly scattered on the surface of the hardened mixture 2 after removing deposits and coating the surface with a mold release agent and oriented in a magnetic field in accordance with the pattern. Thereafter, the oriented nickel particles are transferred to a half-dried glass epoxy substrate, by putting the base material 1 on the substrate after the surfaces of the particles are coated with an adhesive composed of an epoxy resin. Finally, a printed board carrying a pattern having a plated thickness of 25 μm is obtained by electroless plating the nickel particles with copper after washing the particles with water.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention aims to provide a method of manufacturing a printed wiring board which is capable of forming a fine pattern efficiently at low cost and energy saving, particularly in the manufacture of a printed wiring board. .

[0002]

2. Description of the Related Art Conventionally, a method of manufacturing a printed wiring board which is most frequently employed is a method called a subtractive method.
A pattern is formed on the substrate to which the thin copper foil is adhered by photoresist or screen printing, and the parts other than the pattern are removed by etching using a copper etchant, and then the etching resist is dissolved and removed to form a pattern. Is going. In addition, there is a method called an additive method in which a catalyst-containing base material with an adhesive layer is used, a portion other than the circuit is covered with a permanent mask, and a circuit is formed by electroless copper plating. Further, in some cases, a method of forming a pattern by a screen printing method using a conductive silver paste is also used.

[0003]

In the subtractive method, which is the most widely used method for manufacturing a printed wiring board, most parts other than the pattern circuit of the copper foil adhered to the substrate are removed by etching. Therefore, a large waste of resources is generated. In addition, a circuit for forming a pattern requires a clean room having a special air conditioning facility, and further requires a photoresist coating facility, an exposure facility, a developing facility, and the like. The additive method requires the preparation of a special catalyst-containing base material, which requires an expensive permanent mask resist that can withstand the highly alkaline plating solution of the electroless copper plating solution, which is expensive. The method of forming a pattern by screen printing using a conductive silver paste is very simple, but the formation of a fine pattern is difficult and the reliability is also difficult. It has not been adopted for electronic devices. The present invention has been made in consideration of these points, and has been made in order to provide a method for manufacturing a printed wiring board which is energy-saving, low-cost, and highly reliable.

[0004]

In the method for manufacturing a printed wiring board according to the present invention, first, a base material to be a motherboard is prepared. The material may be either metal or non-metallic material,
In order to facilitate the contact transfer in the post-process, a material having a thickness of about 0.1 mm to 0.5 mm is preferable. On top of this, using photoresist method, machining method, screen printing method, etc.
A concave pattern of a necessary circuit pattern is formed. For forming a fine pattern, it is preferable to form a pattern using a photoresist. When a photoresist is used, it is desirable that the ratio between the thickness of the photoresist and the pattern width of the circuit, that is, the so-called aspect ratio is 1: 1 or more. Next, barium ferrite, strontium ferrite having a particle size of 0.5 to 3.0 μm, or a permanent magnet powder of a mixture thereof is mixed with a liquid resin or rubber.
Usually, an epoxy resin adhesive is used for the liquid resin. The mixing ratio is preferably 5% to 10% by weight of the magnetic powder. Embedding is performed by using a squeegee or the like in the concave portion of the circuit in which the mixture of the magnetic powder and the resin is formed. After embedding, this is put in the magnetic field of an electromagnet or a permanent magnet to arrange the magnetic powder mixed with the resin in the direction of the magnetization axis. Heating may be performed during the treatment with a magnetic field to accelerate the curing of the resin. When the resin mixed with the magnetic powder is hardened, the surface is wrapped to remove the mixture adhering to portions other than the concave pattern portion. Using this as a mold, a mold release agent such as Teflon resin is applied to the surface of the mold, and then the particle size is 5 μm to 10 μm.
Then, m nickel particles are sprayed, and a magnetic field arrangement is performed so that the nickel particles become the same as the circuit pattern of the mold. At this time, the shape of the nickel particles is preferably not star-shaped but star-shaped. This is very effective for improving the adhesion to the base material and improving the adhesion during the transfer of the adhesion to the printed circuit board in a later step. Next, the substrate to be a printed wiring board coated with a thin adhesive is brought into close contact with a mold having a magnetic field arrangement, and the nickel powder having the magnetic field arrangement is transferred. It is preferable to use a heat-resistant epoxy resin-based adhesive as the adhesive applied to the substrate. When the resin fixing the transferred nickel particles is completely cured, the process then enters the electroless copper plating process. Before plating, the surface of the Rickel particles is activated using sulfuric acid or the like, and then the electroless copper plating is performed. Plating is performed in the solution. Electroless copper plating is 20μm ~ 25μm
Until the thickness is Also, as a pretreatment for the nickel particles to be transferred, by mixing and drying the nickel particles mixed with a 1% to 5% solution of palladium chloride in a magnetic field, the deposition rate of the chemical copper plating is more than doubled. I have confirmed that. By adopting this manufacturing method, copper resources wasted by etching can be saved, and there is no need for a special treatment such as a catalyst treatment on the base material, and there is no need for an expensive alkali-resistant mask film. Costs are reduced, resulting in resource and energy saving processes.

[0005]

In the printed wiring board obtained by the present invention,
The formed pattern has excellent adhesion strength, and has a tensile strength of 2 kg / cm or more. The pattern created by the photoresist method has 50 lines / spaces.
A circuit of μm / 50 μm was formed. A finer circuit pattern can be formed by selecting a photoresist and employing an X-ray exposure and development method. As an application of the mold according to the manufacturing method of the present invention, not only a method of manufacturing a printed wiring board but also a pattern for printing is formed with the mold of the present invention, and then printed with an ink containing a magnetic substance powder such as nickel. The magnetic material in the ink protrudes in the vertical direction to form a three-dimensional image. By using a permanent magnet for the inspection point, application to a jig for detecting a short circuit or disconnection of a wiring board can be considered.

[0006]

Example 1 Three 50 μm dry film photoresists were stacked on a 0.2 mm thick iron plate, and a circuit pattern of 100 μm / 100 μm in line / space was exposed and developed using a positive film. , A concave circuit pattern was formed. A curing agent is mixed in a ratio of 1 to 1 using an epoxy adhesive, and a particle size of 0.5 μm to
Barium ferrite permanent magnet powder of 3 μm was weighed and mixed in an amount of 10% by weight of an epoxy resin adhesive, and embedded in the recess of the circuit pattern using a squeegee. This was sandwiched between electrodes of an electromagnet having a heating plate on the upper and lower sides, and a current was applied to generate a magnetic field, and a magnetic field treatment was performed while heating the temperature to 50 ° C. After confirming that the epoxy resin has completely cured, remove it from the electromagnet and remove the surface from the electromagnet using a water-resistant paper No. 600 to remove any extraneous matter adhering to other than the circuit and smooth the surface. Was polished. Next, a Teflon resin as a release agent is coated thereon and cured, and then the average particle size is 10 μm.
The nickel particles of m were spread evenly over the surface using a 325th sieve, and a magnetic field arrangement was performed according to the circuit pattern while applying light vibration. This is coated with an epoxy resin adhesive whose surface has been subjected to viscosity adjustment, which is the object to be transferred, and is overlaid with a 1.6 mm-thick glass epoxy material substrate in a semi-dry state, at a pressure of 0.5 kg / c.
The transfer was performed by applying a pressure of m ² . After the epoxy resin adhesive on the glass epoxy material is completely cured, the surface of the transferred nickel particles is activated by immersing in a 10% sulfuric acid solution, washing with water, and transferring to an electroless copper plating solution.
The printed circuit board having a pattern having a plating thickness of 25 μm was obtained by plating for a time.

[0007]

By adopting the manufacturing method of the present invention, the number of manufacturing steps of the printed wiring board is reduced to 1/3 or less, and the manufacturing cost can be greatly reduced. Since no photoresist is used in the manufacturing process of the printed wiring board, there is no need for a clean room. Therefore, expensive photoresist necessary for the photo process, equipment for exposing and developing the photoresist, and equipment for pattern etching are naturally required. However, there is a great advantage that capital investment for manufacturing a printed wiring board can be minimized.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a mold in which permanent magnet powder is embedded in a circuit pattern to form a magnetic field arrangement type.

FIG. 2 is a cross-sectional view of a printed circuit board on which a magnetic substance powder has been closely transferred and plated with a circuit pattern.

[Explanation of symbols]

 1. 1. Permanent magnet pattern type motherboard 2. Permanent magnet mixture embedded in the circuit 3. Non-magnetic insulator layer 4. printed circuit board Adhesive layer 6. 6. Magnetic substance powder that has been closely transferred Circuit plating layer

Claims (1)

[Claims] 1. A required circuit concave pattern is formed on a mother board by using a photoresist method, a machining method, a printing method, and the like, and a mixture of a permanent magnet powder and a resin or rubber is formed in the formed concave part. The magnetic material that has been embedded, treated with a magnetic field, and cured is used as a mold, and magnetic material powder is sprayed on the surface and magnetic field arrangement is performed. A method for producing a printed wiring board obtained by performing electroless plating or electroplating using powder as a catalyst.