JPH0588669B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a steel plate that has excellent adhesion to an insulating layer and punching properties and is suitable for iron-based printed circuit boards that do not require a masking film. (Prior Art) In recent years, iron-based printed circuit boards based on steel plates have been used as they have excellent heat dissipation properties and mechanical strength, and as magnetic paths for small motors. However, in the case of iron-based printed circuit boards, copper foil is attached after forming an insulating layer, and when etching with chemicals or soldering is performed to form a circuit on the copper foil, there may be problems between the insulating layer and the steel plate. There were problems such as peeling, the insulating layer peeling off by about 2 to 3 mm from the edges during cutting or pressing, and burrs on the steel plate during cutting.
In addition, there were problems with the rust resistance of the steel plate on the opposite side to the surface on which the copper foil was applied, and also with the rust resistance of the cut end face of the steel plate. On the other hand, Japanese Patent Application Laid-open No. 142939/1983 proposes a steel plate suitable for printed circuit boards for small precision motors. This content is achieved by plating the surface of steel plates (including silicon steel plates) with one or more of Sn, Zn, Ni, Cr, Cu, and Al at a rate of 5 to 150 g/ ^m2 . Insulation with the steel plate when an insulating layer (approximately 100μ) of epoxy resin or the like is applied to the steel plate, copper foil is pasted on top of it, etched to the desired wiring condition, and various parts are soldered to the copper foil wiring locations. In addition to improving the adhesion with the layer,
This means improved rust resistance. On the other hand, on the other side on which the copper foil is not laminated, the plating layer is corroded by the etching solution during etching. For this reason, an etching-resistant film called a masking film is usually applied, and after the etching process, the masking film is removed for reasons such as insufficient heat resistance during soldering and inhibiting the heat dissipation of the printed circuit board. It is being said. As the above-mentioned masking film, vinyl chloride film with adhesive, polyester film, and polyolefin film are conventionally known. (Problems to be Solved by the Invention) However, the above proposals still have unresolved problems such as peeling of the edges of the insulating layer during cutting or pressing, and burrs of the steel plate during cutting. Sometimes there was a problem in that it was necessary to apply and remove a masking film (after etching was completed). The present invention improves the above-mentioned drawbacks by providing an organic resin layer that has excellent adhesion with the insulating layer, excellent punching properties, and excellent etching resistance on the back surface, and is suitable for iron-based printed circuit boards that do not require a masking film. The purpose of this project is to provide steel sheets with high quality. (Means for Solving the Problems) The present invention has Cr on both sides of a steel plate 1 as shown in FIG.
A plating layer 2 of a specific amount of one or more types selected from Cu, Ni, Zn, and Sn is formed, a specific amount of chromate layer 3 is formed on both sides of the plating layer 2, and furthermore, a plating layer 2 of a specific amount is formed on both sides of the plating layer 2. Organic coating layers 4 and 5, each of which has a dispersible acrylic modified epoxy resin as its main component, are formed to have the required thickness. In manufacturing a printed circuit board using the steel sheet of the present invention, an insulating layer 6 and a copper foil 7 are formed on one side as shown in the figure. The steel plate 1 preferably has a thickness of 0.2 to 2 mm,
If the plate thickness is less than 0.2mm, heat dissipation will not be sufficient;
In the above, when used as a magnetic path for a small motor,
Good motor characteristics cannot be obtained. Regarding the composition of the steel plate, ordinary steel is sufficient if only heat dissipation and mechanical strength are required, but when used as a magnetic path for a small motor, 0.5 It is preferable to use a silicon steel plate containing ~3.5% silicon. Plating layer 2 formed on both sides of these steel plates 1
is a plating amount of 0.5 to 5 g/m ² (one side) of one or more selected from Cr, Ni, Zn, and Sn, and the chromate layer 3 on top is 10 g/m 2 (one side) of Cr, Ni, Zn, and Sn. The amount of chromate is ~80 mg/m ² (one side). Furthermore, on the surface on which the insulating layer and copper foil are laminated, an organic coating layer 4 of 0.5 to 10 g/m ² mainly composed of water-dispersible acrylic modified epoxy resin is provided,
On the other hand, on the side where the edge layer and copper foil are not laminated, 3 to 10
This steel plate is suitable for iron-based printed circuit boards, which must have an organic coating layer 5 containing water-dispersible acrylic-modified epoxy resin as a main component at a rate of g/m ² . The reason for the limitation will be explained in detail below. First, for the plating layer 2, Cr, Cu, Ni, Zn, and Sn are selected as plating metals, and 0.5 to 5 g/m ² of one or more selected from these are selected.
(One side) To be plated. If the plating amount is less than 0.5 g/m ² , good adhesion cannot be obtained even under normal conditions, and rust resistance is also insufficient. On the other hand, if it is 5 g/m ² or more, not only the manufacturing cost is high but also the adhesion with the insulating layer after soldering is poor. The plating layer 2 in this case includes single-layer plating, multi-layer plating, single-layer plating, or alloying treatment after multi-layer plating. As for the chromate treatment layer 3 applied to these surfaces, the composition of the treatment liquid, treatment method, etc. are not particularly limited in the present invention, but in order to obtain a stable chromate coating in a short time, CrO ₃ −H ₂ So ₄ , _CrO3 −HCl,
A bath prepared by adding an anion to chromic anhydride such as CrO ₃ -HF in an amount of 1 to 3% of the amount of CrO ₃ as necessary is suitable. Further, the treatment method may be an electrolytic method or a dipping method. These metallic chromium equivalents are 10 to 80 mg/m ²
(One side) Chromate treatment. If the amount of chromate is less than 10mg/ ^m2 , there is almost no effect of improving adhesion even in normal conditions, and if it is ^more than 80mg/m2, the strength of the chromate layer is insufficient, resulting in cohesive failure in the chromate coating layer and deterioration of adhesion. This is not desirable. Next, regarding the organic coating layers 4 and 5, the organic polymer compound used to form these organic coating layers 4 and 5 is characterized by being a water-dispersible acrylic-modified epoxy resin. Alternatively, a resin containing silica sol, alumina, titanium oxide, a silane coupling agent, etc. may be used. The water-dispersible acrylic epoxy resin is applied by a conventional method such as roll coating or spraying, and then dried by heating with hot air, induction heating, or the like. When a predetermined amount of the organic coating layer 4 containing an organic polymer compound as the main component is formed on the surface on which the insulating layer 6 and the copper foil 7 are to be formed, the insulating layer and the copper foil are formed in the manufacturing process of the printed circuit board, and after etching. We have found that peeling due to poor adhesion between the steel plate and the insulating layer during punching can be prevented, that burrs on the steel plate are reduced, and that the solder heat resistance (heat resistant peel strength) does not deteriorate when soldering is performed after punching. In this case, if the amount is less than 0.5 g/m ² , the purpose will not be achieved, and the effect of improving the peeling of the insulating layer during punching and the burrs of the steel plate during punching and cutting will be small. On the other hand, if it exceeds 10 g/m ² , there is a tendency for the solder heat resistance (heat resistant peel strength) to deteriorate, and it is also economically disadvantageous. More preferably it is 5 g/m ² or less. Next, the organic coating layer 5 not only improves the rust resistance of the plated surface after it is incorporated into a component as a printed circuit board, but also prevents the base metal base material or the plated layer from dissolving during etching, eliminating the need for a masking film. However, a circuit can be formed by etching the copper foil laminated surface on the opposite side. Generally used masking films are made of vinyl chloride, polyester resin, etc., but the quality of these resins deteriorates due to heat during soldering, and the film is generally thick, so It has poor heat dissipation properties, so it is removed after etching. This work is complicated and economically problematic. The product of the present invention has an organic coating layer 5 on the back surface that has an etching resistance of 10 g/m ² or less, has excellent heat resistance, and has a thickness that does not cause problems in heat dissipation.
Therefore, there is no need to apply an etching-resistant film, and of course there is no need to remove the film, making it possible to create a printed circuit board extremely easily. In this case, the coating amount should be 3 to 10 g/ ^m2 ; less than 3 g/ ^m2 will result in insufficient etching resistance, and ^more than 10 g/m2 will be economically disadvantageous. . Next, the reason for limiting the resin composition will be described. First of all, water dispersibility was selected, and this is because the purpose of the present invention is to form an organic coating in-line in a galvanizing line, and the resin can be cured in a short time (using organic solvents). This is because it can be dried and baked at high temperatures because it does not use epoxy resin, and if painting on a separate line is considered, it is also possible to use general epoxy resins that use organic solvents. However, an important objective of the present invention is to economically supply iron-based printed circuit boards, and the present invention is limited to water-dispersible acrylic-modified epoxy resins. Next, the reason why the type of organic resin was limited to acrylic modified epoxy resin will be described. In order to make an epoxy resin water-dispersible, it is generally necessary to copolymerize it with a compound having a carboxylic acid group or an amino group, and various resins have been proposed. The present inventors believe that resins containing acrylic groups and epoxy groups have excellent properties such as heat resistance, etching resistance, and punching properties.
It was found that the desired performance could be obtained. The reason why we limited ourselves to water-dispersible acrylic epoxy resins is that in recent years, the requirements regarding the heat resistance of printed circuit boards have become stricter year by year, and water-dispersible acrylic resins, acrylic-modified olefin resins, polyurethane resins, etc., have severe heat resistance. This is because it is insufficient to meet sexual needs. Of course, for less demanding heat-resistant applications, other resins than acrylic-modified epoxy resins can be used. FIG. 2 shows an example of the resin structure. 0.5 to 5 g/m 2 of one or more selected from Cr, Cu, Ni, Zn, and Sn on both sides of the steel plate ^.
(one side) is plated, and then both sides are treated with chromate treatment of 10 to 80 mg/m ² (one side) in terms of metal chromium, and then an organic coating whose main component is water-dispersible acrylic-modified epoxy resin. One side (copper foil/
According to a steel plate with a structure characterized by coating 0.5 to 10 g/m ² on the insulating layer side and 3 to 10 g/m ² on the opposite side, there is no need to apply or remove a masking film. , it becomes possible to manufacture iron-based printed circuit boards with excellent adhesion between the insulating layer and the steel plate. (Example) Example 1 Ordinary low carbon cold rolled steel plate (plate thickness 0.5mm) or
A silicon steel plate (plate thickness 0.5 mm) containing 2.0% silicon was treated in the following process. First, as a pretreatment, electrolytic degreasing was carried out using a 3% caustic soda solution (liquid temperature: 40° C.) at 2 A/dm ² ×2 seconds. Next, the surface of the steel plate was ground with a commercially available abrasive-containing grinding brush (trade name: Sangrid), and then electrolytically pickled with a 5% sulfuric acid solution (liquid temperature: 20°C) at 2 A/dm ² ×1 second. Using this steel plate 1, under the following conditions, 1 to 6 are
The plating layer 2 was formed by Zn plating, Cu plating for Nos. 7 to 12, Ni plating for Nos. 13 to 18, and Sn plating after Ni plating for Nos. 19 to 24. Plating condition 1 Zn plating: ZnSO ₄ 7H ₂ O 200g/, H ₂ SO ₄ 15g/,
D _K (current density) 50A/dm ² , bath temperature 50℃ 2 Cu plating: Cu ₂ P ₂ O ₇ 2H _{2 O} 80g/, NH ₄ OH 1g/, K ₂
P ₂ O ₇ 300g/, KNO ₃ 8g/, PH8~9,
D _K (current density) 8A/dm ² , bath temperature 50℃ 3 Ni plating: NiSO ₄ 6H ₂ O 250g/, H ₂ SO ₄ 15g/,
D _K (current density) 8A/dm ² , bath temperature 50℃ 4 Sn plating: Phenolsulfonic acid 200g/, Sn ²⁺ 30
g/, D _K (current density) 15 A/dm ² , bath temperature 40° C. Thereafter, an electrolytic treatment was performed as a chromate treatment to form a chromate layer 3. The chromate treatment conditions were CrO ₃ −H ₂ SO ₄ bath (CrO ₃ 50g/, H ₂
Treatment was performed using SO ₄ (0.5 g/) at D _K (current density) of 30 A/dm ² (bath temperature: 50° C.). A water-dispersible acrylic-modified epoxy resin obtained by copolymerizing 20% methyl methacrylate, 70% epoxy resin, and 10% phenol resin on the surface of these chromate-treated steel sheets was applied.
0.1, 0.5, 1.0, 3.0, and 10 g/m ² were coated and dried to form organic coating layers 4 and 5, thereby obtaining a steel plate suitable for printed circuit boards. On top of that, a glass epoxy resin prepreg (thickness: 100 μm) was layered as the insulating layer 6, and then copper foil was layered as the metal foil layer 7 ^.
A printed circuit board was produced by applying pressure for 20 minutes and then heating at 170°C for 2 hours under pressure. Tables 1 (1) and (2) show the evaluation of iron-based printed circuit boards manufactured under various conditions.

【table】

[Table] Normal peel strength... After storage at room temperature for 24 hours, evaluated according to the method for measuring peel strength of JIS C 6481 Heat resistant peel strength... After storage at room temperature for 24 hours, put in a solder bath at 260℃ for 30 minutes
After floating for a second, cool to room temperature and JISC
Evaluated according to the method for measuring peel strength of 6481. Peeling condition during shearing... Peeling condition of adhesive layer after being stored at room temperature for 24 hours and punched out with a press ○: Good with no peeling of the coating △: Insulation Partial peeling at the layer and metal interface ×: Peeling at the insulating layer and metal interface Condition of burrs during shearing... After storing at room temperature for 24 hours, observe the burrs after punching with the same mold using a microscope ○: No burrs Good if less than 30μ ×: Bad if burr is 30μ or more Etching resistance evaluation… Appearance observation after immersion in 37% ferric chloride solution at 70°C for 5 minutes ○: Surface is the same as before immersion ×: Corrosion marks on the surface (Effects of the Invention) As described above, the steel sheet of the present invention not only has excellent adhesion with the insulating layer and rust resistance, but also has excellent insulation properties especially when cutting or pressing printed circuit boards. The organic coating layer 5 has excellent peeling resistance, does not require a masking film during etching, and can be used as a substitute for a masking film. There is no need to remove it, and you can solder and assemble parts as is.

[Brief explanation of the drawing]

FIG. 1 is a schematic block diagram of the present invention, and FIG. 2 is a structural example of a water-dispersible acrylic-modified epoxy resin.

Claims (1)

[Claims] 1 Both sides of a steel plate are plated with 0.5 to 5 g/m ² (one side) of one or more selected from Cr, Cu, Ni, Zn, and Sn, and then both sides are plated with metal chromium equivalent.
10~80mg/ ^m2 (one side) chromate treatment,
Furthermore, an organic coating mainly composed of water-dispersible acrylic modified epoxy resin is applied on one side (copper foil/insulating layer side) at a rate of 0.5 to 10 g/m 2 and on the other side, an organic coating of 0.5 to 10 g/m ² is applied on the other side.
A steel plate for iron-based printed circuit boards, characterized by being coated with ~10g/ ^m2 .