JPH0413440B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a control method for performing electroplating under appropriate current and voltage control. Prior art and its problems In electroplating, controlling current and voltage according to the surface area of the object to be plated is important for the characteristics of the plating bath and the accuracy of the plating film thickness. For this reason, in the past, the surface area of the object to be plated was roughly determined by visual inspection, or the surface area was calculated from a developed view of the surface of the object to be plated. However, visual inspection is less accurate;
In the case of using exploded drawings, the production is troublesome, and even with this method, it is difficult to obtain sufficient accuracy. In particular, it takes a great deal of effort to determine the areas of various types of plating regions, such as plating of circuit patterns including through-holes on printed circuit boards. In addition, when plating printed circuit boards, after masking a predetermined area of primary copper formed by electroless plating, the printed circuit board is immersed in an activation bath, and then copper plating as secondary copper and solder plating are performed. However, since the stage where these secondary copper and solder platings are applied is approximately 80% or more of the manufacturing process, defects in these platings result in a large amount of waste in terms of manufacturing costs. This will occur. Therefore, in printed circuit boards, there is a particularly strong need to accurately determine the surface area of the region to be plated and to perform appropriate current and voltage control based on this. In addition, in order to more appropriately control the plating current and voltage, it is necessary to determine the area of the plating area that extends not only to the object to be plated but also to the support that is immersed in the plating solution together with the object to be plated. This makes it even more difficult to accurately grasp the area to be plated. The present invention solves these problems of the prior art,
It is an object of the present invention to provide a method for controlling current and voltage in electroplating, which can accurately determine the area of a region to be plated and apply appropriate plating current and voltage based on this. Means for Solving the Problems The object of the present invention is to provide a detection tank containing the same treatment liquid as the plating tank separately from the plating tank in the plating process, and to install a positive and negative electrode plate of a predetermined area in the detection tank. is inserted and energized, the voltage or current value under the set value of current or voltage is used as the reference value, and both the set value and reference value are placed between the object to be plated in the plating tank and the anode. A value of the area of the region to be plated of the object to be plated or a value corresponding to the area based on a comparison of the voltage value or current value at this time and the other of the two values. This is achieved by a method of controlling current and voltage in electric plating, which is characterized by determining the value and applying plating current and voltage according to the value. Embodiments Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The figure schematically shows a part of the printed circuit board plating processing apparatus as viewed from above. Reference numeral 10 denotes a plating tank, and anode carbon plates 11 arranged on both sides of the plating tank are supported and electrically connected to a bus bar (metal conductive band) 12, and the bus bar is connected to the anode of a rectifier 40. has been done. A large number of printed circuit boards that have been subjected to electroless copper plating, masking for a predetermined pattern, and activation of the surface to be masked are arranged and supported in a plane on a support 13, and immersed in the center of the plating bath. Each printed circuit board is connected to the cathode of a rectifier 40 via a support 13 and a busbar 14 suspending the support. Reference numeral 20 denotes a detection tank, and carbon plates 21 as anodes are suspended from busbars 22 on both sides of the detection tank, and are connected to the anode of a rectifier 50 for the detection tank through the busbars. A conductive standard plate 23 of a predetermined area is immersed in the center of the detection tank, and is connected to the cathode of a rectifier 50 through a bus bar 24 that supports it. The standard plate 23 may be as small as about 5 to 20 dm ² , and in this example, it is made of copper, which is the same as the area to be plated on the printed circuit board. It is desirable that the carbon plate 21 in the detection tank has the same or larger area than the standard plate 23. In this example, the carbon plate 21 and the standard plate 23 in the detection tank are positioned so that the distance between their facing surfaces is the same as the distance between the surface of the carbon plate 11 in the plating tank and the surface of the printed circuit board. has been done. The rectifiers 40 and 50 are each connected to a control section 60. Further, in this example, the plating tank 10 and the detection tank 20 are connected through a pipe 70, and the pipe is provided with a pump 71 and a filter (not shown) to circulate the plating liquid between the two tanks 10 and 20. and are kept in substantially the same condition. In this set state, a constant voltage of a set value (Va) is applied from the rectifier 50 to both electrodes in the detection tank 20, and the current value at that time is stored in the control unit 60 as a reference value (Ib). . This current value is 1d
Approximately 1A per ^m2 is sufficient. Next, the rectifier 40 supplies power to both electrodes in the plating tank 10 with the same voltage (reference value, Vc) as this voltage value, and the current value at this time is input to the control unit 60 as a detected value (Id).
However, the voltage value applied to the plating tank here is the voltage value applied exceeding the resistance voltage value until current flows between both electrodes. The control unit 60 compares the input reference value (Ib) and detected value (Id), and calculates the area (Sa) of the area to be plated in the plating tank from the ratio and the area (So) of the standard plate 23. do.
This calculation is basically performed based on the following formula. Sa=So×(Ib/Id) Next, based on this calculated value, the control unit 60 outputs a control signal to the rectifier 40 so that the rectifier 40 generates an appropriate voltage according to the area of the region to be plated. As a result, the printed circuit board in the plating tank 10 is plated at an appropriate voltage. The above is an explanation of the case of voltage control, but it is of course possible to perform the method of the present invention based on current control, in which a predetermined current is generated in both electrodes in the detection tank and the voltage at that time is used as a reference value. The control unit 60 uses a voltage having the same value as the reference value as a reference value, and uses the current value when applied to both electrodes in the plating tank as a detected value.
You can also enter each. Furthermore, the relationship between the set value and reference value of the current/voltage in the detection tank and the reference value and detected value of the current/voltage in the plating tank can be combined as appropriate. become.

[Table] In the case of and, the ratio of the area of the electrode plate in the detection tank to the area of the plating area in the plating tank is relatively small (for example, 1:1 to
In 5), the area of the plating area can be determined more accurately, whereas in the case of and, the ratio of these is relatively large (for example, 1:6 to 30).
As a result, the volume of the detection tank can be reduced, which is economical. This seems to be due to the following reasons. The relationship between the voltage value and current value mentioned above is that the voltage during plating is used not only as the voltage required for plating itself but also as the water decomposition voltage.
Due to various effects such as the anode becoming nonconductive as plating progresses and the additive concentration of the plating solution changing, an accurate correspondence is not always guaranteed. In the case of and, by understanding the voltage applied to the plating tank as a reference value as the voltage applied beyond the resistance voltage value until current flows between both electrodes, the effects of the above-mentioned effects can be reduced to some extent. Since the problem can be solved, it can also be applied to a relatively large plating tank in which the various effects are large. On the other hand, in the case of and, since the voltage value measured as the detected value includes the influence of the above-mentioned factors, it is necessary to take this into consideration when handling the voltage value. In this case, the smaller the difference between the electrode area in the detection tank and the area of the plating area in the plating tank, the easier it is to understand the value to be corrected. Therefore, by reducing the ratio of both areas and taking the correction value into consideration, the target area value can be accurately determined. The plating tank can also serve as an activation tank for the objects to be plated in the non-energized state,
In this case, it is possible to grasp the concentration change of the processing liquid in the activation tank from the reference value obtained from the detection tank in the same state as the tank, and adjust the concentration and adjust the plating current and voltage according to the concentration. can be done. The appropriate size of the detection tank varies depending on the overall size of the object to be plated at one time, but it is usually suitable for the area to be plated that is about 1/10 to 1/20 of the object to be plated. It only needs to be large enough to conduct electricity. The plating tank and the detection tank do not need to communicate with each other as long as each plating solution is managed to maintain a constant state. By making the distance between both electrode plates in the detection tank equal to the distance between both electrodes in the plating tank as in the example, it becomes easy to calculate the area of the plating area. Even if the distance between the electrodes is different,
Based on the distance between each electrode, the current in the detection tank
Using the voltage value as a reference, it is possible to grasp the relative correspondence between the current and voltage values in the plating tank for different objects to be plated, and when current and voltage control is performed based on this, it is not always possible to determine the relationship between these two electrodes. It is not necessary that the distances be the same. In this case, control is performed based on relative values corresponding to various areas without determining the actual area of the area to be plated. In addition, when control is performed based on the relative area ratio between various objects to be plated in the plating tank, the material of the standard plate in the detection tank and the area to be plated in the plating tank are The material does not necessarily have to be the same as the material. Furthermore, in the case of such relative control, it is not necessary to set the reference value to the same value as the set value or reference value described above; for example, the reference current value may be set to 1/2 of the reference current value. , it is also possible to use a value multiplied by a certain ratio. Effects of the Invention According to the present invention, the area of the region to be plated in the plating tank or the value corresponding to the area is determined by the current/voltage between the plating tank and the electrode in the detection tank provided separately, and the current/voltage. Since it is determined through the current and voltage applied between the electrodes in the plating tank, it can be determined accurately without the hassle of creating a development diagram of the object to be plated. Even if it is necessary to consider the plating area of the support for the plated object, it is necessary to determine the appropriate current and voltage based on the accurate understanding of the area of the plated area. can be controlled.

[Brief explanation of drawings]

The figure is a plan view schematically showing a part of the plating device used in the method of the present invention. 10... plating tank, 11... carbon plate (anode plate), 13... support, 20... detection tank, 21
...Carbon plate (anode plate), 23...Standard plate, 4
0, 50... Rectifier, 60... Control unit, 70...
Pipe, 71...pump.

Claims (1)

[Claims] 1. A detection tank containing the same treatment liquid as the plating tank is provided separately from the plating tank in the plating process,
Insert a positive and negative electrode plate of a predetermined area into the detection tank and energize it, and use the voltage or current value under the set value of current or voltage as a reference value, and the object to be plated in the plating tank.
A current or voltage corresponding to one of the set value and the reference value is generated between the anode and the object to be plated based on a comparison between the voltage value or current value at this time and the other of the two values. 1. A method of controlling current and voltage in electroplating, characterized in that a value of the area of a region to be plated or a value corresponding to the area is determined, and a plating current and voltage are applied according to the value. 2. The object to be plated is a printed circuit board, and the distance between the positive and negative electrode surfaces inserted into the detection tank;
2. The control method according to claim 1, wherein the distances from the printed circuit board surface to the anode surface are substantially equal. 3. The control method according to claim 1 or 2, wherein the detection tank and the plating tank are communicated with each other by a communication path so that the state of the processing liquid is substantially the same.