JPS61271890A - Substrate for formation of electric circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a substrate for forming an electric circuit.

[Conventional technology]

Most conventional electric circuit boards have been constructed using organic material IIi layer plates.

[Problem that the invention seeks to solve]

The electric circuit forming board constructed using this organic material laminate has the following problems.

(1) The mechanical strength of the board itself is low, making it impossible to mount heavy components.

(2) It cannot be bent and can only be used in flat form.

(3)! Since the grain body has no electromagnetic shielding effect, if electromagnetic shielding was required, it was necessary to provide a shielding effect separately.

(4) Due to poor heat dissipation, reliability is lacking when components that generate a large amount of heat are mounted.

(5) Dimensional changes in the substrate are large due to changes in temperature and humidity.

The object of the present invention is to solve the above-mentioned problems associated with electric circuit forming substrates made of organic material laminates.

[Means to solve the problem]

In the electric circuit forming board of the present invention, a phosphate film or a chromate film is coated on the front and back surfaces of a steel plate via a film having a sacrificial corrosion protection effect on the steel plate, and the phosphate film or chromate film is It is characterized in that a metal conductor layer is provided on the outside with an electrically insulating layer interposed therebetween.

The metal body layer is provided on one or both of the front side and the back side of the steel plate, but in the second invention, a metal conductor layer is provided on one side of the steel plate, and a resin film is provided on the other side. It is characterized by having the following.

In the above, the material having a sacrificial corrosion-preventing effect may be any metal film that has a strong ionization tendency with respect to the steel sheet, such as a zinc film. A zinc film can be formed by galvanizing a steel plate.

Good flatness is generally required for a completed electrical circuit forming board. This is because strict relative positional accuracy of parts including motors and other mechanical parts is required. In order to obtain this good level of flatness, processing of the steel plate, heat treatment,
In addition to the steel plate core material, the yield strength is 27kg.
F/■■2 or more and 45 kgf/mm" or less is desirable, and optimally 30 kgf/layer 2 or more and 40 kgf/layer 2 or less is selected.

In the second invention, the resin film provided on the outside of the phosphorus salt film or chromate film has the purpose of imparting etching resistance, and from this point of view, the resin film may be phenol-based, melamine-based, epoxy-based, or phthalic acid-based. , polyester, aromatic polyamide, polyamideimide, polyimide, polyphenylene oxide, polyphenylene sulfide, polysulfone, triazine, polybenzimidazole, silicon, and fluorine resins. It is desirable to have the above configuration.

[Effect]

Hereinafter, according to the circuit board for forming an electric circuit of IN+, as shown in FIG.

(1) It has strong mechanical strength and can be used to mount heavy parts.

(2) Since it can be bent, it can be used not only in a flat shape but also in a bent shape.

(3) Since the substrate itself has an electromagnetic shielding effect, there is no need to provide a separate shielding member.

(4) Since it has good thermal conductivity, it has good heat dissipation, so it is possible to mount components that generate a lot of heat, and it is also possible to improve reliability.

(5) Dimensional changes can be reduced even with changes in temperature and humidity.

It has the following effects. Furthermore, in addition to the above, there are also the following effects. That is, (6) the electric circuit forming substrate is processed into a required shape by cutting, press punching, etc. Therefore, like this invention,
In a substrate using a steel plate as a core material, the steel plate is exposed at the cut or punched end face, and there is a risk of corrosion in a normal environment. In this regard, in the electric circuit forming substrate of the present invention, since a film having a sacrificial corrosion prevention effect is provided on the front and back surfaces of the steel plate, corrosion of the exposed end surface can be prevented. Incidentally, the thicker the sacrificial corrosion-preventing film, the greater the corrosion-preventing effect, but from an economic standpoint, the thickness is determined by taking into account the required degree of corrosion resistance and the ratio to the thickness of the steel plate.

(7) The electrical insulating layer has a structure in which the film having sacrificial corrosion protection (for example, zinc 1t1) is formed on the outside, and the adhesive strength between the two is a problem. When an electrical insulating layer is bonded to the zinc layer through an adhesive, the initial adhesive strength is low, and the adhesive strength deteriorates over time due to the reaction between the zinc and the adhesive. Since the acid salt film or chromate film is provided on the outside of the sacrificial corrosion-protective layer, the activation of zinc and other sacrificial corrosion-protective layers can be suppressed, and the adhesive strength of the electrical insulating layer can be stably improved. .

In addition to the above-mentioned effects (1) to (7), the second invention has the following effects. (8) When etching a metal conductor layer, if the steel plate on the side where the metal conductor layer is not provided is exposed, it will be corroded by the etching solution, reducing the rigidity of the board and damaging its appearance. In the invention of point 2, the resin film is provided, which causes problems such as defects and deterioration of the etching solution, so that the above-mentioned problems can be solved. However, this resin film is required to have properties that are not affected by the etching solution. Also, with this type of board, before parts are mounted,
For example, heat resistance is required because it goes through many heating steps such as solder reflow treatment at 230° C. for 1 minute. From this point of view, the various resin films described above are preferred.

〔Example〕

Embodiments of the present invention will be described below with reference to the accompanying drawings.

1 to 3 are embodiments of the ptSl invention. That is, in FIG. 1, a galvanized film 2.2 is formed on the front and back surfaces of a steel plate l, and a phosphate film S (or chromate film 3.3 is coated on the outside of the zinc plating 112.2). , an electrical insulation 1) 5 is provided on the outside of the phosphate film 3 on the -E side via an adhesive layer 4, and a metal conductor layer 6 is provided on the outside of the electrical insulation layer 5.A metal conductor that becomes a zero circuit. To provide layers.

After pasting conductive foil such as copper foil over the entire electrical insulating layer 5, a circuit pattern is formed by etching, or a circuit pattern is directly formed on the electrical insulating layer 5-A by electroless copper plating. However, in the illustrated embodiment, a metal conductor is attached to the electrically insulating layer 5 via the adhesive layer 4! fI6
is provided, and the metal conductor layer 6 is etched to form a circuit.

In the above, the electrically insulating layer 5 and the adhesive layer 4.7 can be a Jt-type layer, and as shown in FIG. A metal conductor layer 6 can be provided via 8.

It should be noted that the phosphate film 3 (same as the chromate film) on the lower surface cannot protect the zinc plating film 2 during the kneeching process for the metal conductor foil.

For this reason, the galvanized film 2 is attacked, and then the steel plate 1 is attacked, resulting in problems such as decreased rigidity as a substrate, poor appearance, and deterioration of the etching solution.

Therefore, when etching the metal conductor layer 6, as in the embodiment shown in FIG.
It is effective to cover with a protective film 8 such as a vinyl chloride resin film. If this protection 1i8 does not have heat resistance, it will not be able to withstand heat treatment and will be peeled off before the heating process, but if it has heat resistance, it can be used as a product as is.

In the above, the phosphate coating $3 was used to stably improve the adhesive strength between the galvanized layer 2 and the electrical insulating layer 5, but a comparison of the adhesive strengths is shown in Table 1. I asked for it as a film.

Comparing the phosphate coating shown in Table 1 and the chromate coating that replaces it, the phosphate coating has superior adhesive strength. but,
Since the phosphate film is crystalline and contains crystal water, the crystal water flies off when the metal conductor layer 6 is bonded and hardens, and this is blocked by the metal conductor layer 6, resulting in extremely fine "bulges" on the surface. Sometimes. In order to prevent this "blurring", it is necessary to take measures such as blowing off the crystal water before adhering the metal conductor layer 6, and taking this point into consideration, a chromate film is preferable.

The phosphate film or chromate film prevents rust from forming on the galvanized layer during the manufacturing process, and also eliminates the need for a degreasing process when adhering the electrical insulating layer 5, since rust preventive oil can be omitted. It also provides benefits.

The electrical circuit board obtained as described above is generally required to have good flatness. In particular, a board integrated with an audio equipment chassis has various parts housed in a narrow space, and requires strict relative positional accuracy between parts such as motors and mechanical parts. degree is required.

For example, a VTR chassis usually has a dimension of 100 to 300 square meters, but the product must have a distortion height of 100 p - flatness. However, the manufacturing process of the chassis is as shown in the example of FIG. 8, and includes many factors that cause distortion. Inserting leveling correction in the middle would make management easier, but currently the
The limit is to manage it to the extent of the terminal intestine. Furthermore, the internal stress of the steel plate is released due to the heating in the subsequent / By focusing on the relationship between heat and thermal strain, we found that thermal strain can be reduced by increasing the yield strength of the steel plate. FIG. 6 shows the relationship between the yield strength of a steel plate and the amount of thermal strain during solder reflow treatment. The amount of thermal distortion is 200 x 200 (about 53 measurement points on the surface of the chassis plate) is plotted. The results revealed that thermal strain decreases as the yield strength of the steel plate increases. However, if the yield strength becomes too high, the workability of the steel plate will decrease, and it will also be difficult to correct the flatness in the middle, so the amount of distortion after pressing will tend to increase, and the overall distortion of the product will decrease. There is also a risk that the amount may actually increase. Figure 7 plots the yield strength of the steel plate and the maximum strain of the final product. As a result, the yield strength is 27 kgf/am2 or more - b45 kgf as the range in which the amount of strain can be suppressed to 100 #L or less.
/mm2 or more F, preferably 30kgf/mm2 or more -14
It can be seen that it is better to select a steel plate with a resistance of 0 kgf/mm2 or less.

FIGS. 4 and 5 show an embodiment of the second invention. That is, in FIG. 4, a galvanized S film 2.2 is formed on the front and back surfaces of a steel plate l, and a phosphate film l1l (or chromate film) 3.3 is formed on the outside of the galvanized film 2.2. is coated, and an electrical insulating layer 5 is provided on the outside of the upper phosphate skin @ 3 via an adhesive layer 4, and a metal conductor layer 6 is provided on the outside of the electrical insulation 1) 5. , Apply a resin coating to the outside of the phosphate coating 3 on the lower surface by painting or using a film adhesive method! 19 is the setting. This embodiment differs from the embodiment of the first invention in that a resin skin 1P19 is provided. The conductor circuit can be formed either by etching or by forming the circuit directly on the electrical insulating layer -F by electroless steel plating or the like. Also, regarding the electrical insulating layer 5, as shown in FIG. 5, the electrical insulating layer 5 and adhesive R4 are used in common.
It is also possible to use the adhesive layer 7 with insulating properties.

There are many possible procedures for coating the resin film 9, providing the electrical insulating layer 5, and the metal conductor layer 6. There is a method of bonding the resin film 9 to the other surface of the steel plate l. The resin coating [9 may be applied after the metal conductor layer 6 and the electrical insulation layer 5 are attached, but the metal conductor layer 6 and the electrical insulation layer 1 on the steel plate 1! Since bonding of j'5 is generally carried out by thermocompression bonding, it is often not possible to increase the area of one bonding due to equipment considerations, and therefore the resin skin s9 is also coated in small areas. Taking this into consideration, it is better to cover the resin skin s9 continuously over a medium-large area, or even in the form of a band, in advance, which improves productivity and is also advantageous in terms of cost.

Even in the case of this example, good movability is required;
The steel plate l has a yield strength of 27 kg4/m layer 2 or more fH4
5kgf/sm2 or less, preferably 30kgf/am”
As in the above embodiment, it is preferable to select a material with a weight of 40 kgf/m2 or less.

The examples have been described above, and next, a specific manufacturing example will be shown. The manufacturing process of the product was performed according to FIG. 8, and an electric circuit board integrated with a chassis having the structure shown in Table 2 was obtained.

Table 2 The above structure corresponds to the embodiment of FIG. 3 of the first invention and the embodiment of FIG. 4 of the second invention. The number next to the item name of the component represents the code in the figure.

Adhesion of polyimide film and electrolytic steel foil to core material is as follows:
A double-sided adhesive polyimide film and electrolytic steel foil are layered on a core material coated with a resin film on one side, and approximately 100 sheets of the core material are sequentially applied so that the resin film of the next core material is in contact with the core material. They were stacked and heated while being pressurized at a pressure of about 40 kgf/cm2. At this time, if the electrolytic copper foil had a resin coating inside, it would cause a serious problem in the subsequent electrical circuit formation process, but since melamine crosslinked polyester resin is stable at high temperatures, no resin coating occurred. Also, during etching, the steel plate was not attacked except for the end face of the core material. There was no practical problem by cutting and removing the end surface that had been eroded by the etching solution. The resin film was not damaged during various other heating steps.

Table 3 shows the characteristics of the electrical circuit board thus obtained.

The adhesion strength between the galvanized layer and the polyamide film (electrical insulation layer) bonded via the chromate film and adhesive is at a satisfactory level, and the heat distortion during solder reflow treatment is as small as 21p■, making the final product excellent. The amount of distortion was also suppressed to less than Bagm and 100F. In addition, sufficiently satisfactory values for electrical properties were obtained.

〔Effect of the invention〕

As explained above, according to the present invention, since a steel plate is used as the core material, a board for forming an electric circuit is provided which has high mechanical strength, excellent additivity, magnetic shielding properties, heat dissipation properties, and dimensional stability. It is effective in providing the following.

Further, since a film having a sacrificial corrosion-preventing effect on the steel plate is provided on the front and back surfaces of the steel plate serving as the core material, there is an effect of preventing corrosion of the end face of the substrate. Furthermore, the adhesive strength of the electrical insulating layer is also high and has the effect of stabilizing it.

In the second invention, since a resin film is further provided on the side where the metal conductor foil is not provided, etching of the metal conductor foil can be easily performed.
This has the effect of providing a substrate for forming an electric circuit.

[Brief explanation of drawings]

1 to 3 are enlarged sectional views of the embodiment of the first invention,
Figures 4 and 5 are enlarged sectional views of the embodiment of the second invention, Figure 6 is a graph showing the relationship between the yield strength of a steel plate and the amount of thermal strain, and Figure 7 is a graph showing the relationship between the yield strength and the amount of thermal strain of the steel plate. FIG. 8 is a graph showing the relationship between strain and strain, and is a diagram showing a specific manufacturing process. l... Steel plate, 2... Zinc plating film, 3... Phosphate film or chromate film, 4... Adhesive, 5...
... Electrical insulating layer, 6... Metal conductor layer, 7... Electrical insulating layer/adhesive, 8... Back surface protective S film, 9... Resin film. Figure 6 Figure 7 11t1 Large size

Claims (1)

[Scope of Claims] 1) A phosphate film or a chromate film is coated on the front and back surfaces of the steel plate via a film that has a sacrificial corrosion protection effect on the steel plate, and the outside of the phosphate film or chromate film is 1. A substrate for forming an electric circuit, characterized in that a metal conductor layer is provided with an electric insulating layer interposed therebetween. 2) The electric circuit forming substrate according to claim 1, wherein the film having sacrificial corrosion protection is a galvanized film. 3) The steel plate has a yield strength of 27 kgf/mm^2 or more45
A substrate for forming an electric circuit according to claim 1, which has a thickness of kgf/mm^2 or less. 4) The surface of the steel plate is coated with a phosphate film or chromate film via a film that has a sacrificial corrosion protection effect on the steel plate, and an electrically insulating layer is coated on the outside of one of the phosphate films or chromate film. A metal conductor layer is provided,
A board for forming an electric circuit, characterized in that a resin film is provided on the outside of the other phosphate film or chromate film. 5) A substrate for forming an electric circuit according to claim 4, wherein the film having a sacrificial corrosion prevention effect is a galvanized film. 6) The steel plate has a yield strength of 27 kgf/mm^2 or more45
The electric circuit forming substrate according to claim 4, wherein the electric circuit is less than kgf/mm^2. 7) Resin coatings include phenol, melamine, epoxy, phthalic acid, polyester, aromatic polyamide, polyamideimide, polyimide, polyphenylene oxide, polyphenylene sulfide, polysulfone, triazine, and polyester. The electric circuit forming substrate according to claim 4, which is made of one or more of benzimidazole-based, silicon-based, and fluorine-based resins.