JP2563118B2 - Copper or copper alloy material for flexible printed circuit board and manufacturing method thereof - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a copper or copper alloy material for a flexible circuit board and a method for producing the same, and particularly, to improve etching properties, flexibility, etc. suitable for such applications. And a method for producing the same.

[Prior Art] With the remarkable progress of ICs and LSIs, the development of circuit boards on which these elements are mounted has been extensively and rapidly advanced.

As described above, the main purpose of the circuit board is to interconnect the elements mounted on it, but other low dielectric constant insulators, electrical characteristics such as low resistance conductors, mechanical characteristics such as flexibility or rigidity, Heat transfer characteristics, reliability, economy, etc. are required.

Such circuit boards are roughly classified into resin boards, ceramic boards, and metal boards. The ceramic substrate has been developed for hybrid ICs, the resin substrate has been developed for printed circuits, and the metal substrate is located between them.

Among such substrates, the resin substrate is a resin substrate such as epoxy, phenol, or polyimide, or a composite substrate of these and other materials such as paper and glass, laminated with copper foil, and integrated with an adhesive or heat and pressure. It was formed by.

Flexible circuit (print) of the above resin boards
The substrate is a substrate obtained by laminating a rolled copper foil having a flexibility of about 10 to 60 μm on a flexible resin such as polyimide, and is used in a wide range of electronic devices.

On the circuit board laminated with the above copper foil, a fine wiring pattern having a line width and a line interval of about 100 μm is formed by etching.

And for high density, the above line width and line spacing are 50μ.
The m pattern is also being considered.

In the flexible printed circuit board, copper and copper alloy materials are adhered to a resin, and this is further etched to form a wiring pattern.

Further, such a material for a flexible printed circuit board is rolled by a roll that has been dull processed by a method such as shot blasting or liquid honing, and is supplied with a certain surface roughness. Further, in recent years, a method using electric discharge machining has been considered as a new dull machining method.

[Problems to be Solved by the Invention] In the above-mentioned circuit board, since the line interval of the wiring pattern is becoming narrower, it is required that the circuit board has good etching property and a fine circuit can be accurately manufactured. . In order to improve this etching property, it is necessary to make it within a proper range.
If the surface roughness is not within the proper range, the resist film will be partially peeled off and an appropriate etching shape will not be created. Conversely, if the surface is too closely adhered, it cannot be removed with a strong alkali after etching. There was a problem.

Further, as its name implies, the flexible printed circuit board is different from the conventional printed circuit board in that it is bent and installed in a device or used as a movable part. Breakage of flexible printed circuit boards has become an important issue as electronic devices have become smaller and higher in density. Therefore,
There has been a strong demand for a flexible printed circuit board having better flexibility.

Further, the method of rolling a dull-processed roll of a flexible printed circuit board material by a method such as shot blasting or liquid honing has the following problems.

First, dull rolls that have been dull-processed by shot blasting or liquid honing are extremely worn out, and materials with a plate thickness of 0.01 to 0.06 mm, such as flexible printed circuit board materials, can be used for 1 t.
When rolled more than on (10,000 m in length), the surface roughness at the front and rear ends of the coil is significantly different.

Therefore, it is inevitable that the front end has a large roughness and the rear end has a small size.

Secondly, the rolls produced by these methods have sharp dullness (roughness), and therefore the material surface is scraped during the dull rolling, and metal powder adheres to the material surface as stains. Sometimes it makes a fine indentation. This is difficult to remove sufficiently even after degreasing, which causes unevenness in manufacturing the flexible printed circuit board.

Thirdly, the dull-finished surface of the material produced by these methods is likely to have a sharp convex portion like the roll, which scrapes rubber rolls in the degreasing and resist coating steps and causes new stains. .

Further, it has been found that it has a sharp convexo-concave pattern and becomes a source of generation of fine classics at the time of bending, resulting in a marked decrease in flexibility.

Furthermore, it is difficult to produce a surface having a fine enough roughness suitable for a flexible printed circuit board by the electric discharge machining.

The present invention has been made in view of the above problems, as a flexible printed circuit board copper or copper alloy material,
It is intended to provide a material having improved etching property and flexibility.

[Means for Solving Problems] In the present invention, the surface roughness is Ra 0.2 to 1.0 μm, R _max 1.0 to 5.0.
In the final cold rolling process and copper or copper alloy material for flexible printed circuit boards, the surface roughness of the material is Ra 0.2 ~ by using a rolling roll surface-dulled by laser processing. 1.0 μm, R _max 1.0
The method for producing a copper or copper alloy material for a flexible printed circuit board is characterized by setting the thickness to 5.0 μm.

The surface roughness of the copper or alloy material for the circuit board has a great influence on the resist adhesion as described above. Surface roughness is 0.
If it is less than 2 μm, the adhesion of the resist is weakened, causing defects such as resist flow and unevenness. Also Ra
Is more than 1.0 μm, the adhesive strength of the resist is also strong, which causes poor development and poor peeling after etching, and also causes the edge surface to be rough. Therefore, it is necessary to control Ra to 0.2 to 1.0 μm.

However, it is not possible to obtain an appropriate material for a flexible printed circuit board only by the above definition of Ra.

That is, when R _max is less than 1.0 μm, the adhesive force of the resist becomes weak and uneven etching occurs. Also, R
_{When max} is larger than 5.0 μm, it is a thin plate, so that the influence on the plate thickness fluctuation becomes large, which causes the plate thickness fluctuation of the circuit board itself and tends to cause non-uniform stress concentration, which causes a decrease in flexibility. Become. Therefore, R _max is 1.0 to 5.0 μ
It is necessary to control to m.

A material having such a surface roughness can be obtained by performing final cold rolling with a rolling roll subjected to surface dull processing by laser processing. The reason is as follows.

When a rolling roll subjected to surface dull processing by laser processing is used, the size, depth, distribution, etc. of the craters can be freely controlled by the laser beam, and smooth unevenness can be formed. Therefore, the surface of the material rolled using such a roll also has a smooth convex portion, and the flexibility and the etching property are significantly improved, and
Control of Ra and R _max is also extremely easy.

FIG. 1 is an exaggerated drawing of one of the craters formed on the surface of the roll R. The ridge P protruding from the roll surface is shown.

FIG. 2 shows the surface of the material when it is rolled by the roll shown in FIG. The top view of the crater is shown in the upper part of the figure. The cross-section curve for this roll is shown below, showing the material surface formed by this roll.

 Next, the method of processing the dull of the rolling roll will be described.

FIG. 5 shows a working situation in which a rolling roll is dull processed by a laser processing method. The laser beam generated in the laser beam generating and directing device L is directed to the laser beam conduit 1.

The rolling roll R to be dulled is rotatably supported by the roll supporting device 4. One of the roll shafts (right side here) is joined to a drive shaft 9 from a rotary drive device (not shown). A contraction tube 2 is provided at the tip of the beam conducting tube 1 via an expansion joint or in a nested manner.
Further, a laser focusing device 3 is attached to the tip thereof, and converges the laser beam having passed through the conducting tube 1 and the expansion tube 2 so as to focus on the surface of the rolling roll R. The laser focusing device 3 is supported by the support arm 5. The support arm 5 is movable along the length of the roll over the entire length by an appropriate moving mechanism. Here, the moving mechanism is shown as composed of the carrier 6 carrying the supporting arm, the screw rod 7 for moving the carrier 6 and the drive motor M, but any other moving mechanism such as a slide system or a self-propelled system is adopted. Of course you can. According to the movement of the supporting arm, the laser focusing device is provided with the chopper 8 in the longitudinal direction of the roll and along the entire length of the roll,
It is rotatable and linearly movable in the longitudinal direction of the roll at a speed synchronized with the supporting arm. The laser beam reaches the roll surface through a slit formed around the chopper 8.

Therefore, various surface roughness and morphology can be easily adjusted by setting the roll rotation speed, the moving speed of the supporting arm (and hence the laser focusing device) and the chopper, the chopper rotation speed, the size of the chopper slit, and by adjusting the laser output. Can be created.

When the laser beam focused on the surface of the rolling roll is irradiated, melting of the material in the circular portion centered on the focal point occurs, and when it expands, metal vapor is ejected from the center, and then a crater-shaped circular hole. Occurs. It should be noted that the annular ridge P is generated in a controlled manner along the peripheral edge of the circular hole. This ridge can be used for dulling the surface of the material for a flexible printed circuit board.

This crater dull-processed on the roll by laser processing is reproducibly generated on the entire roll, and the size and depth of the crater and its distribution arrangement pattern can be freely controlled. Fig. 3 shows the surface roughness profile of the material for flexible printed circuit boards dull-processed by laser processing, and Fig. 4 shows the surface roughness profile of the material rolled by the conventional liquid honing dull roll.
The liquid honing type has a sharp convex portion on the surface, whereas the laser processing type has a smooth surface form.

Therefore, the laser-processed dull skin is
There is no problem such as stains due to adhesion of metal powder or stains of resist solution due to scraping of a rubber roll.

Further, in the present invention, after the final cold rolling by such a rolling roll, the shape is corrected if necessary. This shape correction can be performed using an appropriate correction means such as a roller leveler, a tension leveler, and a tension roller leveler.

[Example] Dull rolls having various surface morphologies were produced by adjusting the number of rotations of the chopper, the number of rotations of the roll, and the laser beam output using the apparatus shown in FIG.

A roll dull-processed by conventional liquid honing was also combined with these rolls, and copper or copper alloy for flexible printed circuit boards was rolled to a thickness of 0.035 mm.
The surface roughness Ra and R _max after rolling were measured, and a flexible printed circuit was manufactured by the steps of degreasing, resist coating-exposure / development-etching perforation-resist removal, and the uneven quality of the flexyl printed circuit was investigated.

Flexibility complies with JIS P8115, and the number of breaks was investigated using a MIT massage fatigue tester under the conditions of a bending angle of 135 °, a bending radius of 0.8 mm, and a load of 1.5 kg.

 The results are shown in Table 1.

In Table 1, Ra and R _max comply with the definitions and measurement methods defined in JIS and the like, and are as follows.

Ra: It is called center line average roughness, and a portion of measurement length 1 is extracted from the roughness curve in the direction of the center line, the center line of this extracted portion is taken as the X axis, and the direction of longitudinal magnification is taken as the Y axis. When a curve is represented by y = f (x), the value obtained by the following formula is represented by micrometers (μm).

Ra = 1 / l∫ ₀ ¹ | f (x) | dx R _max ; It is called the maximum height, and the extracted part is two straight lines parallel to the average line of the part (extracted part) extracted from the section curve by the reference length. When sandwiched, the distance between these two straight lines is measured in the direction of the longitudinal magnification of the sectional curve, and the value is expressed in units of micrometers (μm).

As is clear from Table 1, in Examples 1 to 4 of the present invention, since the surface roughness was controlled to a certain region by the rolling roll that was dull processed by the laser, it was possible to obtain a good mask without unevenness. .

On the other hand, Comparative Examples 1 and 2 are also examples of laser dull, but in Comparative Example 1, resist flow occurred during the etching process because Ra and R _max were too small, which impaired the uneven quality. Further, in Comparative Example 2, since Ra and R _max were too large, the resist could not be removed completely in the resist removing step after etching, and gas holes became uneven, resulting in poor quality.

Further, since the surface roughness is too rough, the flexibility is deteriorated.

Comparative examples 3 and 4 are examples of liquid honing,
Due to the sharp convex portion of the surface, scraps from the rubber roll soiled the resist solution, and the poor adhesion of the resist due to poor degreasing resulted in poor unevenness.

Also, the flexibility is deteriorated due to the acute-angled irregularities on the surface.

[Advantages of the Invention] The present invention improves etching properties and flexibility as described above, increases reliability, and is sufficiently adaptable to miniaturization as a flexible printed circuit board.

It is highly promising that such a board will increase the packaging density of ICs, LSIs, etc., and that electronic equipment using this will be further developed into new applications and functions.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a dulling crater formed by a laser method, and FIG. 2 is an explanatory diagram showing the upper surface of the crater, a cross-sectional contour, and a dulling contour generated in a material for a flexible printed circuit board in association with each other. The figure shows the surface roughness profile of the material rolled by laser processing dull roll, No. 4
The figure is a surface profile rolled on a conventional liquid honing dull roll. FIG. 5 is a perspective view showing a partial cross section of an example of an apparatus for dulling a rolling roll by a laser method. L ... Laser beam generating and directing device, 1 ... Beam conducting tube, 2 ... Telescopic tube, 3 ... Laser focusing device, 4 ... Roll support device, 5 ... Support arm,
6 ... Carrier, 7 ... Screw rod, 8 ... Chopper, 9 ... Drive shaft, M ... Motor, P ... Raised, R ...
…roll.

Claims (3)

(57) [Claims] 1. Surface roughness Ra 0.2-1.0 μm, R _max 1.0-5.0
A copper or copper alloy material for flexible printed circuit boards characterized by having a thickness of μm. 2. The final cold rolling step is characterized in that the surface roughness of the material is Ra 0.2 to 1.0 μm and R _max 1.0 to 5.0 μm by using a rolling roll surface-dulled by laser processing. A method for manufacturing a copper or copper alloy material for a flexible printed circuit board. 3. The method for producing a copper or copper alloy material for a flexible printed circuit board according to claim 2, wherein shape correction is performed after the final cold rolling.