JPS5954027B2 - Laminated board for printed wiring board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a laminate for printed wiring boards having excellent soldering heat resistance and adhesion between a conductive circuit and an electrically insulating layer.

A printed wiring board is manufactured by bonding a metal foil to an electrically insulating layer, printing a desired electrical wiring circuit on the metal foil, and then removing unnecessary portions by etching.

Therefore, excellent heat resistance and adhesion are required for the adhesion performance between the metal foil and the electrical insulating layer. At the same time, since unnecessary parts of the metal foil are removed by etching to form a desired electrical wiring circuit, it is required that the etching processability and appearance after etching be good. Conventionally,
In order to meet the above requirements, a treated layer as shown below was formed on the surface of the metal foil, and then the metal foil and the electrical insulating layer were integrated to form a printed circuit laminate.

1. Formation of a roughened layer by liquid honing, polishing with sandpaper, etc. 2. Formation of a roughened layer by high current density electroplating 3.
Formation of an oxide film layer using chemicals However, method 1 cannot satisfy the required adhesion performance.

In No. 2, unevenness tends to occur during pre-treatments such as acid cleaning and degreasing before electroplating, making it difficult to obtain uniform surface wettability on the metal foil surface after roughening electroplating. That's funny.

Further, since the roughening treatment is performed at a high current density, it is difficult to form a uniformly roughened surface. 3, it is difficult to form a uniform oxide film, special equipment is required because a strong oxidizing agent is used, and printed wiring board laminates with this treatment layer are etched to completely remove the oxide film. There are problems such as difficulty in removal.

Furthermore, a method is known in which a metal tin plating layer is formed on the surface of metal foil to be bonded to the electrically insulating layer.

However, printed wiring boards manufactured using this method require soldering work to attach parts, and the melting point of metal tin is 23.
Since the temperature is 2° C., there is a problem that the metal tin plating layer melts and the metal foil circuit peels off. The present invention eliminates these problems. That is, it is a laminate for a printed wiring board in which a stannous oxide layer is formed on the surface of the gold foil that will be bonded to the electrical insulating layer in order to improve the heat resistance and adhesion between the metal foil and the electrical insulating layer. No special equipment is required to form the stannous oxide layer, and a uniform stannous oxide layer can be easily obtained. Furthermore, the stannous oxide layer can be easily removed by etching, which is extremely effective since it does not damage the appearance of the printed wiring board.

The details of the present invention will be explained with reference to the drawings.

As shown in FIG. 1, the present invention is a laminate for a printed wiring board, which has a stannous oxide layer 2 on the surface of a metal foil 1 that is bonded to an electrically insulating layer 3.

The metal foil 1 is a foil-like material having a thickness of 1 to 100 microns and made of copper, nickel, chromium, etc. or an alloy thereof. The present invention is manufactured by the following method. First, as shown in FIG. 2, a metal tin layer 4 having a thickness of 5 microns or less and having good adhesion to the metal foil 1 is formed on the metal foil 1 by conventional electroplating or chemical plating. After that, the metal tin layer 4 is oxidized to become a stannous oxide layer (Figure 3).
. However, the oxidation of metal tin progresses extremely slowly at room temperature, and the thickness of the oxidized layer is only about several tens of angstroms. Furthermore, when metallic tin is oxidized in air at a temperature of 100° C. or lower, it does not become stannous oxide, but becomes stannic oxide (SnO2), which does not easily react with acids and alkalis and has electrical conductivity. If this stannic oxide layer is formed on the surface of the metal foil, it will cause problems in the subsequent printed wiring board manufacturing process, that is, the etching process. In the present invention, by treating the gold layer foil 1 having the metal tin layer 4 in an oxygen-enriched atmosphere maintained at 100° C. or higher for several minutes, the metal tin layer 4 having a metallic tin layer 4 can be converted into gray-white stannous oxide. (SnO) layer 2.

Thereafter, the metal foil 1 having the stannous oxide layer 2 is heated and pressed onto an electrical insulating layer 3 made of a thermosetting resin such as an uncured or hardened phenolic resin, epoxy resin, unsaturated polyester resin, etc. By adhering, a laminate for printed wiring board is obtained.

In the heat-pressure bonding, heat-resistant adhesive agents such as butyral roof enol resin, acetal roof enol resin, epoxy-modified phenol resin, etc. may be used if necessary. Next, examples of the present invention will be described.

First, a rolled copper foil with a thickness of 35 microns was immersed in an acidic chemical tin plating bath to form a metal tin layer with a thickness of 0.5 microns on the rolled copper foil.

Thereafter, the rolled copper foil having the metal tin layer was placed in a 160°C furnace with oxygen adjusted to a volume fraction of 40% for 5 minutes,
The metal tin layer was replaced with a stannous oxide layer. After applying an adhesive made of acetal roof enol resin to the surface of the stannous oxide layer of the rolled copper foil having the obtained stannous oxide layer,
This was bonded to the paper base phenolic resin in an uncured state under heat and pressure to obtain a 1.6 mm thick phenolic resin copper foil-clad laminate for printed wiring boards. The properties of the obtained laminated board were as follows.

Soldering heat resistance (260℃ solder bath float) 30-40 seconds Peeling strength 18-22kg/Cm
Appearance after etching Good As mentioned above, by providing a heat-resistant stannous oxide layer on the surface of the metal foil that will be bonded to the electrical insulation layer, the adhesion between the electrical insulation layer and the metal foil was improved. . Further, the formation of the stannous oxide layer does not require any special equipment, and it is possible to easily obtain a uniform stannous oxide layer. Further, the printed wiring board laminate of the present invention has a good appearance after etching the metal foil, and has extremely great industrial value.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of a laminate for printed wiring boards of the present invention, Fig. 2 is a cross-sectional view of a metal foil on which a metal tin layer is formed, and Fig. 3 is a cross-sectional view of a metal foil formed with a stannous oxide layer used in the present invention. FIG. 1 is a metal foil, 2 is a stannous oxide layer, 3 is an electrical insulating layer, 4
is a metal tin layer.

Claims (1)

[Claims] A laminate for a printed wiring board in which a metal foil is bonded to an electrically insulating layer, wherein the surface of the metal foil that is bonded to the electrically insulating layer has a stannous oxide layer. Board.