JP4807829B2 - Manufacturing method of flat conductor for flexible flat cable - Google Patents

Description

The present invention relates to the production how flat Sumishirube body for a flexible flat cable having excellent surface properties (FFC).

Along with miniaturization and weight reduction of electronic devices and the like, the wiring materials to be mounted are also being miniaturized. For this reason, the space is limited and the flexibility is required. For example, a flexible flat cable is used in which a plurality of flat rectangular conductors are arranged in a plane and laminated from both sides with a tape-like insulator material. This flexible flat cable is connected to a printed wiring board or the like by calibrating the terminal portion, but in order to reduce contact resistance or improve solderability, the flat conductor is usually tin-based (Sn-based). Plating) or gold / nickel plating (Au / Ni plating). The Sn-based plating, Ni plating, or Au / Ni plating layer is considered to be more preferable as the surface is uniform. Such a flat conductor is usually formed by plating a copper wire having a diameter of about Φ0.5 to 1 mm, then drawing the wire to a diameter of about Φ0.1 to 0.2 mm, and further rolling the flat conductor. . Such a technique is described in Patent Document 1, for example. However, in such a manufacturing method, since the copper round wire is rolled flat, the processing strain in the material such as the copper round wire is not uniform, and a portion that deforms greatly and a portion that hardly deforms occur. It will be. Naturally, the plating layer applied thereon is also subjected to the same deformation, and the thickness of the plating layer is not uniform as a whole, and a large difference occurs depending on the location. Specifically, the plating layer is thick at the central portion of the flat conductor in contact with the rolling roll, and the portion between the central portion and both end portions tends to be thin. When the thickness of the plating layer becomes uneven in this way, the performance of the plating layer is impaired, which is not preferable. For example, in the case of Au / Ni two-layer plating, the Ni layer prevents the copper from diffusing into the Au layer as a barrier layer. However, if a thin portion occurs in the Ni layer, the copper diffuses into the Au layer. Then, the copper reaching the surface of the plating layer significantly deteriorates the corrosion resistance of the Au plating layer. Such poor corrosion resistance is undesirable because it leads to an increase in contact resistance and a decrease in solderability. In the case of an Sn-based plating layer, it is known that needle crystals called whiskers grow from a peripheral plating layer pressed against a connector terminal when fitted with a connector. Such whisker growth is not preferable because it causes a short circuit between copper wirings and leads to troubles in electronic equipment. In order to suppress the growth of this whisker, it is effective to suppress the thickness of the pure tin layer of the Sn-based plating layer to a predetermined thickness or less. On the other hand, the solder wettability is better as the plating layer is thicker. For this reason, it is desirable that the plated layer of the flat rectangular conductor after rolling is uniform. In contrast to the rolling method described above, Patent Document 2 discloses a repetitive cross rolling method in which rolling is performed by repetitively crossing one or both of the rolling rolls. And according to such a rolling method, it is supposed that the rolling log | history with the advancing direction and angle will be produced | generated to a rolling material. However, when this rolling method is simply applied to the production of a flat conductor for a flexible flat cable, the effect of making the thickness of the plating layer uniform may not be sufficient.
JP-A-8-199325 JP-A-2-274303

Therefore object of the present invention is to provide, in the plating layer after rolling to provide a preferred method for producing a uniform flat Sumishirube body for a flexible flat cable.

The problem to be solved is that the round wire conductor formed with the plating layer is rotated simultaneously with the rotation of the upper and lower rolling rolls, and the rotation axis of the upper rolling roll along the plane parallel to the rolling surface of the lower rolling roll. In the crossing direction, the maximum part of the thickness of the plating layer is obtained by rolling while repeatedly moving in a range of 50 to 429 ratio of the number of repeated movements of the lower rolling roll to the number of rotations of the upper and lower rolling rolls. This is solved by setting the ratio of the minimum part to 0.68 to 0.89 .

According to the present invention, the round wire conductor formed with the plating layer is crossed with the rotation axis of the upper rolling roll along the plane in which the rotation axis of the lower rolling roll is parallel to the rolling surface simultaneously with the rotation of the upper and lower rolling rolls. The maximum and minimum thicknesses of the plating layer are rolled by rolling in a range of 50 to 429 in the ratio of the number of repetitive motions of the lower rolling roll to the number of rotations of the upper and lower rolling rolls By using the method for manufacturing a flat conductor for FFC characterized in that the ratio to the portion is 0.68 to 0.89, the processing strain in the material such as copper round wire becomes uniform, and plating The thickness of the layer can be uniform throughout. By making the thickness of the plating layer uniform, the performance of the plating layer is not impaired. Furthermore, in the above-described method for manufacturing a rectangular conductor, the ratio of the number of repetitive motions of the lower rolling rolls to the rotational speed of the upper and lower rolling rolls is set to 50 to 429 , so that the above-described effects are more reliably generated. be able to.

The present invention is described in detail below. The manufactured flat conductor is a flat conductor for a flexible flat cable in which the plating layer of the rolled surface has a thickness ratio of more than 2/3 of the maximum portion and the minimum portion. Thus, if the thickness of the plating layer is very uniform, a flat conductor for FFC having good corrosion resistance, suppressing whisker growth, and good solderability can be obtained. Thus, to 2/3 than the thickness of the plating layer of the rolling surface as the thickness ratio of the maximum portion and minimum portion as a result of studying a method for manufacturing a flat conductor described below, to obtain When the ratio of the maximum plating layer thickness (A) to the minimum plating layer thickness (B) was examined, if the B / A value was 0.68 to 0.89 , corrosion resistance was good and whisker growth This is because it has been confirmed that a flat conductor for FFC with good solderability can be obtained. Specifically, in the case of Ni plating layer or Au / Ni two-layer plating, the Ni layer serves as a barrier layer to prevent copper from diffusing and to eliminate the problem of deteriorating corrosion resistance. In the case of the Sn-based plating layer, whisker growth could be sufficiently suppressed even when fitted with a connector. As the Sn-based plating, pure tin, tin-copper alloy (Sn-Cu), tin-bismuth alloy (Sn-Bi), tin-silver alloy (Sn-Ag), or the like is used. Furthermore, the Ni plating layer, the Au / Ni two-layer plating layer, and the Sn-based plating layer all have good solderability (solder wettability). For this reason, if the thickness of the plating layer on the rolled surface exceeds 2/3 as the ratio of the maximum part and the minimum part as in the present invention, the plating layer satisfying all the above-mentioned conditions can be obtained, and the corrosion resistance A flat rectangular conductor for FFC that does not cause an increase in contact resistance and solderability due to a decrease in whisker, suppresses whisker growth, and causes a short circuit between copper wirings and the like, thereby causing no problems in electronic equipment. be able to. Such flat conductor for FFC is produced by the production method described below.

That is, the round wire conductor on which the plating layer is formed, simultaneously with the rotation of the upper and lower rolling rolls, the rotation axis of the lower rolling roll crosses the rotation axis of the upper rolling roll along a plane parallel to the rolling surface. The ratio between the maximum part and the minimum part of the thickness of the plating layer by rolling while repeatedly moving in the range of 50 to 429 ratio of the number of repeated movements of the lower rolling roll to the number of rotations of the upper and lower rolling rolls The production method is characterized in that the ratio is set to 0.68 to 0.89 .

This will be described with reference to FIG. FIG. 1 shows an outline of the upper and lower rolling rolls, which is a main part in a manufacturing apparatus in which the lower rolling rolls repetitively move in a cross with respect to the upper rolling rolls. Indicates the axis of rotation. 3 is a lower rolling roll, and 4 is the axis of rotation. 3 ′ is a position when the lower rolling roll 3 repeatedly moves in a direction crossing the rotating shaft 2 of the upper rolling roll 1 (position indicated by the rotating shaft 4 ′ of the lower rolling roll 3 ′). That is, it is controlled so as to repeatedly move within the range indicated by ← →. The round conductor 5 is inserted into the upper and lower rolling rolls 1 and 3 from the direction of the → mark, and the upper and lower rolling rolls 1 and 3 rotate, and at the same time, the lower rolling roll 3 has its rotation axis. 4 is rolled into the rectangular conductor 6 while performing repetitive motion within the range of repetitive motion indicated by the rotating shaft 4 ′ of the lower rolling roll 3 ′ indicated by a dotted line (in this case, 2 ° 17 ′). At this time, the repetitive motion of the lower rolling roll 3 needs to be considerably faster than the rotational speed of the upper and lower rolling rolls 1 and 3. By setting it as such a rolling method, it can be set as a flat conductor with the uniform thickness of a plating layer. Moreover, although the description here demonstrated the case where a lower rolling roll repetitively moved, the thing of the structure where the upper rolling roll 1 repetitively moves may be used. According to such a rolling method, compared with the conventional method of simply rolling between upper and lower rolling rolls, the processing strain in the material of the round wire is uniform, and the plating layer is made to have its maximum and minimum portions. it can be made 2/3 than uniform as the ratio of the thickness of the parts. Thus, the uniform plating layer has no problems such as a decrease in corrosion resistance, a problem that many whiskers are generated, and a solderability (solder wettability). In addition, the diameter of the plated round wire conductor after drawing to obtain a flat conductor is usually about Φ0.1 mm to Φ0.2 mm. In addition, unevenness in the effect of uniformizing the thickness of the plating layer, which has been a problem simply by using a manufacturing apparatus in which the lower rolling roll is cross-repetitively moved with respect to the upper rolling roll, is eliminated. The mechanism for repetitively moving the lower rolling roll 3 of the rolling apparatus is usually performed by changing the rotational movement of the motor to repetitive movement by a cam.

Further, the above-described method for producing a rectangular conductor is preferably a method for producing a flat conductor for FFC in which the ratio of the number of repetitive motions of the lower rolling roll to the rotational speed of the upper and lower rolling rolls is 50 to 429. . By performing under such manufacturing conditions, the thickness of the plated layer of the obtained rectangular conductor can be surely made uniform with more than 2/3 as the ratio of the thickness between the maximum portion and the minimum portion. That is, in the rolling method described above, when the ratio of the number of repetitive motions of the lower rolling roll to the rotational speed of the upper and lower rolling rolls is 50 to 429 , the processing strain in the round wire material becomes more uniform, Also, the thickness of the plating layer becomes more uniform throughout. For this reason, the plating layer is made more uniform, the corrosion resistance is further improved, the whisker suppression effect is improved, and the solderability (solder wettability) and the like are improved.

The flat conductors for FFC obtained as described above can be used as various FFCs by arranging a plurality of flat conductors at appropriate intervals and laminating them with various plastic tapes. . Specifically, when a flat plated conductor is subjected to Ni plating layer and Au / Ni two-layer plating, the uniformly plated Ni layer serves as a barrier layer to prevent copper from diffusing into the Au layer. When the copper reaching the surface of the plating layer deteriorates the corrosion resistance of the Au plating layer, no problem occurs. Therefore, an FFC can be obtained in which contact resistance does not increase or solder wettability is lowered, and contact reliability is not impaired even when a gas corrosion test or the like is performed. Further, the connection strength (shear strength) can be increased by improving the solderability. Furthermore, by controlling the Ni plating layer to a required thickness, an FFC excellent in corrosion resistance and bending characteristics can be obtained. In addition, in the case of a rectangular conductor with a uniform Sn-based plating layer, whisker growth from the periphery of the plating layer is sufficiently suppressed when mated with a connector, causing a short circuit between the copper wiring and the like. Since there is no trouble with equipment and solderability is good, the connection strength (shear strength) can be increased. Since the thickness of the plating layer can be controlled to about 0.2 to 1.0 μm, the FFC has excellent whisker resistance and electrical contact reliability. Further, the FFC sufficiently suppresses the generation of whiskers of 50 μm or more, so that a short circuit of the wiring circuit does not occur even when the pitch between the copper wirings of the terminal portion in the FFC becomes very small.

  The effects of the present invention were confirmed by the examples and comparative examples described in Table 1. That is, a plated layer having a thickness of 10 μm of Ni or pure tin was formed on an annealed copper wire of Φ0.8 mm by electrolytic plating. This plated annealed copper wire was drawn to Φ0.12 mm by wire drawing. Using this drawn plated annealed copper wire, a manufacturing machine (Yoshida Kinen's repetitive cross rolling mill-100 type) in which the lower rolling roll crosses and reciprocates with respect to the upper rolling roll is 0.035 mm in thickness. A conductor was used. At this time, the number of rotations of the upper and lower rolling rolls and the number of repetitive motions of the lower rolling roll were varied. Note that Comparative Examples 3 and 4 are cases where rolling is performed with normal upper and lower rolling rolls.

  The cross section of the flat rectangular conductor thus obtained was mirror-polished and the maximum thickness (A) and the minimum thickness (B) of the plating layer were measured. The uniformity of the plating layer was described as the ratio of the thickness of the plating layer (B / A). Further, the ratio of the number of rotations per minute (X) of the upper and lower rolling rolls to the number of repetitive motions (Y) of the lower rolling rolls was defined as the rotation ratio (Y / X), and the results are shown in Table 1.

As is clear from Table 1, the flat conductor in which the plating layer on the rolled surface has a thickness ratio of 0.68 to 0.89 as the thickness ratio between the maximum part and the minimum part has excellent whisker resistance and corrosion resistance. I understand that. In addition, such a flat conductor has a round wire conductor formed with a plating layer and the rotation of the upper and lower rolling rolls simultaneously with the rotation axis of the lower rolling roll along the plane parallel to the rolling surface. It can be seen that this can be obtained by a method for producing a flat conductor that is rolled while being repetitively moved very fast with respect to the rotational speed of the upper rolling roll in the crossing direction. In detail, when a pure tin plating layer Ki Tsu because the ratio of the plating layer thickness (B / A) it can be seen that resistance whiskers is good at 0.68 or more. In addition, it can be seen that the above-described flat conductor can be obtained if the rotation ratio (Y / X) is 50 or more. Furthermore, as described in Examples 4 to 6, when the plating layer is Ni plating, the plating layer thickness ratio (B / A) is 0.76 or more, indicating that the corrosion resistance is good. In addition, it can be seen that the above-described flat conductor can be obtained if the rotation ratio (Y / X) is 50 or more.

  On the other hand, in the comparative example, either whisker resistance or corrosion resistance becomes a problem. That is, in the case of the pure tin plating layer of Comparative Example 1, the plating layer thickness ratio (B / A) is 0.58, which has a problem in whisker resistance, and Ni plating as in Comparative Example 2 In this case, the ratio of the plating layer thickness (B / A) becomes 0.47, and the corrosion resistance becomes a problem. Further, the rotation ratio (Y / X) at this time was 43 in all cases. Incidentally, as in Comparative Examples 3 and 4, in the case of the conventional roll rolling method in which the lower rolling roll is not repeatedly moved, since the plating layer is not uniform, the whisker resistance is poor in the pure tin plating layer, The Ni plating layer has a problem in corrosion resistance.

The flat conductor for FFC manufactured by the manufacturing method of the flat conductor according to the present invention is excellent in uniformity with the thickness of the plating layer on the rolled surface being more than 2/3 as the thickness ratio of the maximum part and the minimum part. Therefore, the FF using this is excellent in whisker resistance, corrosion resistance, and solderability, and is useful for wiring of electronic devices. Further, it can sufficiently cope with downsizing and high density.

It is drawing which shows the outline of the upper-lower rolling roll part in the manufacturing apparatus which a lower rolling roll carries out cross-repetitive movement with respect to an upper rolling roll.

DESCRIPTION OF SYMBOLS 1 Upper rolling roll 2 Rotating shaft of 1 3 Lower rolling roll 3 'Lower rolling roll 3 moved by repetitive motion 3
4 3 axis of rotation 4 '3' axis of rotation 5 Round wire conductor 6 Flat conductor

Claims (1)

At the same time as the rotation of the upper and lower rolling rolls, the round wire conductor on which the plating layer is formed moves the upper and lower rolling rolls in a direction crossing the rotation axis of the upper rolling roll along a plane parallel to the rolling surface. The ratio of the maximum portion and the minimum portion of the thickness of the plating layer is reduced to 0 by rolling while repeatedly moving within a range of 50 to 429 of the number of repeated movements of the lower rolling roll with respect to the number of rotations of the lower rolling roll. A method for producing a flat conductor for a flexible flat cable, characterized in that the thickness is .68 to 0.89.