JPH0521951A - Copper foil for copper-clad laminate - Google Patents

Abstract

PURPOSE:To enable strength and reliability when mounting electronic parts whose lengths are reduced and capacities are increased on a copper-clad laminate. CONSTITUTION:A copper foil 2 is joined to an insulation plate 3, thus forming a copper-clad laminate 1. A non-joined surface with the insulation plate 3 of the copper foil 2 is roughened. The copper foil is roughened by forming fine recessed and projecting portions on a drum surface at a raw foil production process and then performing transfer from the drum surface or by performing soft etching of the raw foil surface. The copper foil has fine recessed and projecting portions due to roughening and its surface area is increased, thus enabling the copper foil to be suited for a high-density mounting of electronic parts.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copper clad laminate, which is a base plate of a printed wiring board, and a copper foil laminated on an insulating layer.

[0002]

2. Description of the Related Art A printed wiring board is manufactured by subjecting a copper clad laminate to various treatments such as photosensitive ink application, circuit pattern exposure, development, etching, and solder resist application. It is mounted by bringing leads into contact with the joint land and soldering. The copper-clad laminate, which is the base plate for this printed wiring board, is formed by thermocompression bonding a copper foil to an insulating plate made of bakelite or glass epoxy resin, or by bonding a copper foil to an insulating plate made of paper phenol. There is. The copper foil of such a copper clad laminate is manufactured by dissolving high-purity electric wire scrap in sulfuric acid to form a copper ion solution and electrolyzing the copper ion solution. During electrolysis, a drum whose surface was adjusted to Ra = 0.43 μm was used as a cathode, and while this drum was rotated in a copper ion solution, metallic copper was electrodeposited on the surface and the electrodeposited copper foil was removed from the drum. Roll-shaped green foil is formed by continuously peeling. Then, the raw foil is laminated on an insulating plate such that the surface on the peeling side is the non-bonding surface and the surface on the opposite side is the bonding surface to form a copper clad laminate. In this lamination, copper oxide is adhered to the bonding surface of the copper foil to secure the adhesiveness with the insulating plate. FIG. 5 shows the copper clad laminate manufactured in this way, and the surface (non-bonding surface) of the copper foil 51 on the substrate 52 is Ra.
Is a uniform surface of about 0.43 μm.

[0003]

By the way, as electronic components mounted on a printed wiring board, chip components tend to be more numerous than discrete components, and the ratio of surface-mounted chip components is also large. There is. On the other hand, in recent years, the chip parts have been made smaller and larger in capacity, and along with this, the joint lands and circuits of the printed wiring board for mounting and electrically connecting these chip parts have become smaller. However, the surface of the copper foil of the copper clad laminate, which is the original plate of the conventional printed wiring board, is a uniform surface, and the surface area of the bonding land and the circuit per unit area cannot be made constant or more. For this reason, the mounting strength and connection strength of electronic parts are limited, and the reliability of these parts is reduced.

The present invention has been made in consideration of the above circumstances, and a printed wiring board that can be mounted and connected with reliable strength even for an electronic component having a short size and a large capacity. It is an object of the present invention to provide a copper foil for a copper-clad laminate for the purpose.

[0005]

The copper foil for copper-clad laminate of the present invention is characterized in that the non-bonding surface with the insulating plate is roughened to form fine irregularities.

By forming fine irregularities on the surface of the copper foil as described above, the surface area of the bonding land formed by the subsequent processing is increased, so that the mounting strength and connection strength of the electronic component can be increased. It is possible and reliability is improved.

In this case, fine irregularities may be formed on the surface of the drum during the raw foil manufacturing process, and the irregularities may be transferred during the production of the raw foil, whereby the irregularities can be formed simultaneously with the production of the copper foil. it can.

Further, the surface of the green foil may be soft-etched to form the unevenness, and in this case, the adjustment and management of the unevenness are facilitated.

[0009]

[Embodiment 1] FIG. 2 shows a manufacturing process of a copper foil according to an embodiment of the present invention. As the copper raw material 21, an electric wire scrap having a purity similar to that of electrolytic copper is used, and the copper raw material 21 is dissolved in sulfuric acid to be ionized to form a copper sulfate solution 22.
The drum 23 is immersed in this copper sulfate solution 22 as a cathode. A copper plate, a lead plate, a titanium plate or the like is used for the anode 24,
Electrolysis is performed while rotating the drum 23, and metal copper is electrodeposited on the surface of the drum 23. The copper foil 25 attached to the surface of the drum 23 is continuously peeled off as the drum 23 rotates. FIG. 3 shows the drum 23, on the surface 23a of which fine irregularities are formed. This unevenness is formed by etching or polishing the drum surface, and Ra = 0.5.
The depth or height is about 1.0 μm. Therefore, at least the surface (the surface on the drum side) of the copper foil 25 electrodeposited on the surface 23a of the drum 23 has the same degree (R
Fine irregularities (a = 0.5 to 1.0 μm) are transferred.
The copper foil thus peeled off from the drum 23 becomes a roll-shaped raw foil 26, which is sequentially drawn out from the roll state and treated. In FIG. 2, 27 is a treatment tank, which is formed by connecting a plurality of tanks in series. By passing through each tank, adhesion of copper oxide for maintaining the adhesive strength with the insulating plate and heat resistance of the surface Adhesion of a barrier layer for application, rust preventive film treatment, etc. are performed. The copper foil 25 that has passed through the treatment tank 27 passes through the adhesive application roller 29, the adhesive 28 is applied to the back surface thereof, and then dried by the dryer 30. Then, the cutter 31 cuts the sheet-shaped copper foil 2. The surface of the copper foil 2 which is not joined to the insulating plate is roughened and has fine irregularities. The adhesive applied to the back surface of the copper foil 2 makes it an insulating plate such as bakelite, glass epoxy resin or paper phenol. The copper clad laminate is manufactured by laminating the copper clad laminates.

FIG. 1 shows this copper-clad laminate 1, in which a copper foil 2 is laminated and integrated on the upper surface of a substrate 3. Fine irregularities are formed on the surface of the copper foil 2, and in this state, the photosensitive ink is applied to the surface of the copper foil 2, the circuit pattern is exposed, developed, etched, and solder resist is applied. The printed wiring board is manufactured.

FIG. 4 shows a printed wiring board 4, on which a bonding land 5 made of copper foil, a circuit 6, and a solder resist 7 are formed on a substrate 3. An electronic component (not shown) such as an IC is mounted on the bonding land 5, while a lead of the electronic component is connected to the circuit 6. The mounting and connection are performed by soldering, but the surface area of the bonding land 5 and the circuit 6 is increased because the surface of the bonding land 5 and the circuit 6 has fine irregularities. For this reason, the bonding strength at the time of soldering is dramatically improved, and highly reliable mounting can be performed. Moreover, since the surface area due to the unevenness can be increased, the size can be reduced, so that a high-density circuit can be obtained. Therefore, it is possible to obtain sufficient reliability even for a circuit having a very small width of 100 μm, and it is possible to cope with high density of electronic components. Furthermore, the adhesion of the ink for the pattern resist or the solder resist of the printed wiring board is increased, so that high performance can be achieved.

In the above-mentioned embodiment, the fine irregularities on the copper foil were transferred from the surface of the drum in the raw foil process, but in the present invention, the copper foil after the raw foil process is roughened by a soft etching treatment to be fine. Unevenness can be formed on the surface of the copper foil. The following formulations A and B are etching agents that can be used in this soft etching, respectively.

[0013] Prescription A   Sulfuric acid with a concentration of 98% (W / W) 100 cc / l   Sodium persulfate or ammonium persulfate 120-90 g / l   Residue in 1 liter of water Prescription B   Sulfuric acid with a concentration of 98% (W / W) 8-16 cc / l   Hydrogen peroxide 6-12 cc / l   Residue in 1 liter of water

The surface of the copper foil can be roughened by immersing the copper foil in the etching agent having such a formulation for 15 to 30 seconds, and Ra = 0.3 to 1.0 on the entire surface of the copper foil.
It can be formed with fine asperities of μm. The soft etching is performed on the copper foil before the treatment process. In the surface roughening of the copper foil by such soft etching, by adjusting the prescription of the etching agent, the immersion time, etc. in addition to the action of the above-mentioned example,
Since it is possible to form irregularities of any size, there is an advantage that roughening can be performed according to the purpose.

[0015]

According to the present invention, since the surface area is increased by roughening the surface of the copper foil for forming the bonding land and the circuit to form fine irregularities, the reliability of the mounting of electronic parts is improved and It can also be applied to mounting high-density electronic components.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a copper clad laminate in which the copper foil of the present invention is laminated.

FIG. 2 is an explanatory view of a manufacturing process of the copper foil of the present invention.

FIG. 3 is a perspective view of a drum for producing a raw copper foil.

FIG. 4 is a cross-sectional view of a printed wiring board manufactured from the copper clad laminate of the present invention.

FIG. 5 is a sectional view of a conventional copper-clad laminate.

[Explanation of symbols]

1 Copper clad laminate 2 copper foil 3 substrates 4 printed wiring board

Claims (3)

[Claims] 1. A copper foil to be laminated on an insulating plate, wherein a non-bonding surface to the insulating plate is roughened to form fine irregularities, and a copper foil for a copper-clad laminated plate. 2. The copper foil for copper-clad laminate according to claim 1, wherein the irregularities are transferred from the drum surface by forming fine irregularities on the drum surface in the raw foil manufacturing process. 3. The copper foil for a copper-clad laminate according to claim 1, wherein the unevenness is formed by soft etching the surface of the green foil.