JP4700396B2 - Printed circuit board plating method - Google Patents

Description

  The present invention relates to a method for plating a printed circuit board, and in particular, when through-hole conductive plating of a printed circuit board used in an electronic device is performed with a panel plating rack, the printed circuit board edge is equalized while the plating thickness in the product is equalized. The present invention relates to a method for plating a printed circuit board that prevents plating from adhering to a portion and prevents various problems caused by scattering of plated copper powder from the edge of the printed circuit board.

  When through-hole conductive plating of printed circuit boards used in electronic equipment is performed by panel plating, a substrate that has been subjected to conductive treatment in advance is held by a conductive rack to form a cathode, and the inside of the bath filled with plating solution It is carried out by immersing and energizing the anode in the center between the anodes installed at both ends.

  As the rack used at this time, an upper connection arm is attached to the upper ends of one and the other linear members, a lower connection arm is attached to the lower ends, and a long hole for adjusting the length is provided in each connection arm. A configuration is known in which a rack portion is formed by bolting, and a groove for holding a printed circuit board is formed in each linear member (see, for example, Patent Document 1).

  In general, in the case of panel plating, the periphery of the printed circuit board end tends to be thicker than the vicinity of the center. As shown in FIG. 7, the printed circuit board 53, which is a cathode immersed in the plating tank 51, receives a current almost uniformly from the anode 52 facing the central portion, whereas the peripheral portion is from the periphery. Therefore, the current density distribution is high in the peripheral portion of the printed circuit board 53 and the plating tends to adhere thickly.

  As a countermeasure, it has been shown that a net-like shielding plate made of a metal wire is inserted between the anode and the substrate to equalize the current density distribution (see, for example, Patent Document 2). In addition, there is known an apparatus for making the plating thickness of a printed circuit board uniform by using a box-type shielding plate having a large number of through holes (for example, see Patent Document 3).

On the other hand, there is known a plating method using a shielding plate in which a plurality of regions having different hole diameters and arrangement densities are set so that the current density in the central portion of the printed circuit board and the current density in the peripheral portion are uniform. (For example, refer to Patent Document 4). Furthermore, the structure which provided the shielding board in the holder (rack) is also known (for example, refer patent document 5).
Japanese Utility Model Publication No. 61-182071 Japanese Patent Laid-Open No. 50-50236 Japanese Utility Model Publication No. 56-21485 JP 2002-54000 A JP 2002-161398 A

  As described above, the variation in the plating thickness on the surface of the printed circuit board has been improved by providing the shielding plate. However, the plating thickness adhering to the side surface of the printed board cannot be improved because a sneak current is received from the surroundings even if a shielding plate is provided. For example, as shown in FIG. 8, when the printed circuit board 60 is mounted on a rack in three stages, the portion 61 surrounded by a broken line (the portion painted in black) 61 is thickly plated on the side surfaces of the upper and lower printed circuit boards 60. . FIG. 9 is a cross-sectional photograph of the printed circuit board end portion 61 side portion, and it can be clearly seen that the plating is thickly attached around the periphery.

  Since the plating thickness on the surface of the printed circuit board is not so uneven, it does not interfere with the etching of the product itself when forming a pattern, but the side surface of the printed circuit board and its surroundings are shown in the photograph in FIG. As shown, etching residue occurs in the 61a portion. As shown in the 61b portion of the photograph in FIG. 11, when this etching residue is peeled off, it becomes a conductive contaminant.For example, if the contaminant is involved in the subsequent solder resist layer forming step, a short circuit failure will occur. Various problems will arise. Conventionally, only the variation of the plating thickness on the surface of the printed circuit board has been emphasized, but such a problem due to scattering of the etching residue should not be overlooked.

  Although it is conceivable to mask the printed circuit board edge to prevent plating on the side surface of the printed circuit board edge, an additional process increases to mask the printed circuit board edge. Become. In addition, there is an adverse effect that the plating is thick around the masked portion. Therefore, a plating method is required in which the side surface of the end portion of the printed circuit board is mostly masked, and the current density increases sequentially as it reaches the periphery.

  Therefore, the present invention prevents plating adhesion to the printed circuit board end while equalizing the plating thickness in the product when performing through-hole conduction plating of the printed circuit board used in the electronic device with the panel plating rack, It aims at providing the plating method of the printed circuit board which prevents the various malfunction by the plating copper powder scattering from the printed circuit board edge part.

  The present invention has been proposed in order to achieve the above-mentioned object, and the invention according to claim 1 is characterized in that a pair of conductive vertical frames are fixed with a horizontal frame, and the vertical frame is used as a cathode. In the method for plating a printed circuit board using a panel plating rack that is immersed in a plating solution while holding the printed circuit board so that the printed circuit board is sandwiched between the vertical frames by feeding the printed circuit board, above and below the panel plating rack, Provided is a method for plating a printed circuit board, comprising: mounting a shield made of an insulating material having a cross-sectional shape combining a V shape and a square shape to sandwich the printed circuit board.

  According to this configuration, the shields mounted on the upper and lower sides of the panel plating rack reduce current reception and prevent excessive plating from adhering. The shield has a cross-sectional shape that combines a V shape and a square shape that sandwich the printed circuit board, so that it does not receive a sneak current from the surroundings, and the current density is approximately near the center and the edge of the printed circuit board. It becomes uniform.

  According to a second aspect of the present invention, a plate-shaped shield having an opening for equalizing the plating thickness is attached to the vertical frame of the panel plating rack so as to be opened and closed when the printed board is attached or detached. The printed circuit board plating method according to claim 1, wherein the printed circuit board plating rack is provided.

  According to this configuration, the plate-like shield provided in the vertical frame of the panel plating rack is opened on both sides, and the printed board is inserted into the V-shaped groove portion of the lower shield. Then, the plate shield is closed, and the upper shield is inserted into the printed board with the V-shaped groove portion facing downward, and the printed board is fixed to the panel plating rack.

  In the present invention, as described above, the plating thickness of the printed circuit board is equalized by the plate-shaped shielding object having the opening, and the side surface of the printed circuit board end portion and the periphery thereof are formed by the upper and lower shielding objects combining the V shape and the rectangular shape. Masking prevents plating adhesion and prevents various problems due to plating copper powder scattering from the edge of the printed circuit board.

  Hereinafter, the method for plating a printed circuit board according to the present invention will be described with reference to preferred examples. When performing through-hole conductive plating of printed circuit boards used in electronic equipment with a panel plating rack, the plating thickness on the printed circuit board is prevented from being adhered while the plating thickness in the product is equalized. For the purpose of preventing various problems caused by scattered copper powder, a shield made of an insulating material having a cross-sectional shape combining a V shape and a square shape sandwiching the printed circuit board is mounted on the top and bottom of the rack for panel plating. In addition, a plate-like shielding object having an opening for equalizing the plating thickness is attached to the vertical frame of the panel plating rack so that it can be opened and closed when the printed circuit board is attached and detached.

  FIG. 1 is a front view of a panel plating rack used in the plating method of the present invention. A main member of the panel plating rack (hereinafter simply referred to as a rack) 10 is a vertical frame 11 made of a pair of left and right conductive members. 11 and horizontal frames 12 and 12 which are attached to the upper and lower sides of the vertical frames 11 and 11 and maintain the left and right intervals. The vertical frames 11 and 11 sandwich the both sides of the printed circuit boards 13 and 13. It is formed so as to be immersed in the plating solution while being held and to supply power to the printed circuit boards 13, 13... As a cathode.

  A plate-like shield 14 is attached to each of the vertical frames 11 so as to be openable and closable in the left-right direction. 14 a and 14 b are formed, and an opening 14 c is provided in the middle of the plate-like shield 14. In addition, holes 14d, 14d,... The plate-like shield 14 is mounted on the front and rear surfaces (front side and back side of the drawing) of the rack 10 so as to be opened and closed in the left-right direction.

  And inside the said plate-shaped shielding object 14, the shielding objects 15a and 15b are installed in the up-and-down position of the said rack 10, respectively. 2 is a photograph of the shielding object 15b installed at the lower part of the rack 10, FIG. 3 is a photograph of a side surface of the shielding object 15b, and FIG. 4 is an explanatory view showing a cross-sectional shape of the shielding object.

  As shown in FIGS. 2 to 4, the shields 15a and 15b are made of an insulating material having a cross-sectional shape combining a V-shape and a square, and when the printed circuit board 13 is sandwiched between the grooves of the shields 15a and 15b, In the section c, most of the side surface of the printed circuit board and its periphery are masked to suppress plating. Furthermore, the V-shaped section b forms a shape in which the current density increases sequentially as it goes around.

  In order to apply plating to a more uniform thickness as a whole, the dimensions of each part of the shields 15a and 15b are preferably a: 20 mm, b: 50 mm, c: 20 mm, and d: 40 mm. However, a dimensional change of about ± 10% is allowed. Note that the dimension of the e portion may be arbitrarily set according to the size of the printed circuit board 13. The upper shield 15a is installed so that the groove is downward or movable so that the groove is downward, and the lower shield 15b is installed so that the groove is upward.

  When performing the plating process of the printed circuit board 13 with the rack 10, as shown in FIG. 1, the plate-like shields 14, 14 attached to the rack 10 are opened on both sides, and both ends of one printed circuit board 13. Is sandwiched between the left and right vertical frames 11, 11, and the lower end of the printed circuit board 13 is inserted into the groove of the shield 15 b installed at the lower part of the rack 10 and fixed by positioning means (not shown). Thereafter, the remaining two printed circuit boards 13 and 13 are sequentially stacked on top of the lower printed circuit board 13 and are sandwiched between the left and right vertical frames 11 and 11 and fixed by positioning means.

  Then, after closing the left and right plate-like shields 14, 14, the shield 15 a installed at the top of the rack 10 is closed downward, and the groove of the shield 15 a is inserted into the upper end of the upper printed board 13. Fix it.

  Thus, the plurality of printed circuit boards 13 are held on the rack 10 and shielded by the plate-shaped shielding object 14, and the printed circuit board 13 is covered by the upper and lower shielding objects 15 a and 15 b installed inside the plate-shaped shielding object 14. By shielding the end side surface, the current density is substantially uniform in the vicinity of the central portion of the printed circuit board and the periphery of the end portion.

  FIG. 5 is a cross-sectional photograph of the end portion of the printed circuit board plated using the shields 15a and 15b. Compared with the cross-sectional photograph of the printed board subjected to the conventional plating method shown in FIG. It can be seen that the plating thickness at the end is reduced.

  FIG. 6 is a diagram comparing the plating thickness distribution when there is no shield and the plating thickness distribution when the shield of the present invention is used. Compared to the conventional plating method shown in FIG. In the plating method of this invention shown to (2), it turns out that the plating thickness of the printed circuit board edge part is thin, and the whole plating thickness distribution is made more uniform. Thus, the effectiveness of the plating method of the present invention in which shielding objects are arranged above and below the rack was confirmed.

  It should be noted that the present invention can be variously modified without departing from the spirit of the present invention, and the present invention naturally extends to the modified ones.

The front view of the rack for panel plating used for the plating method of this invention. The photograph of the shield installed in the lower part of the rack shown in FIG. The photograph of the side of the shield shown in FIG. Explanatory drawing which shows the cross-sectional shape of the shield shown in FIG. The cross-sectional photograph of the printed circuit board edge part which performed the plating method of this invention. The figure which compared the plating thickness distribution of the plating method of this invention, and the conventional plating method. Explanatory drawing which shows the malfunction of the conventional plating method. Explanatory drawing which shows the malfunction of the conventional plating method. The cross-sectional photograph of the printed circuit board edge part which performed the conventional plating method. An explanatory photograph showing a defect of a conventional plating method. An explanatory photograph showing a defect of a conventional plating method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Panel plating rack 11 Vertical frame 12 Horizontal frame 13 Printed circuit board 14 Plate-shaped shielding object 14a Extension part 14b Extension part 14c Opening part 14d Hole 15a Shielding object 15b Shielding object

Claims (2)

A pair of conductive vertical frames are fixed with a horizontal frame held apart, and the vertical frame is immersed in the plating solution while feeding the printed circuit board as a cathode and sandwiching the printed circuit board between the vertical frames. In the plating method of the printed circuit board that uses the rack for panel plating,
A printed circuit board plating method, wherein shielding members made of an insulating material having a cross-sectional shape combining a V-shape and a square shape sandwiching the printed circuit board are mounted above and below the panel plating rack. The vertical frame of the panel plating rack is a panel plating rack in which a plate-like shield having an opening for equalizing the plating thickness is attached so that it can be opened and closed when the printed board is attached or detached. The method for plating a printed circuit board according to claim 1.