JPS60138096A - Plating method - Google Patents

Abstract

PURPOSE:To decrease fluctuation in the concn. of metallic ion in a plating liquid and to obtain satisfactory plating while eliminating roughness is the stage of performing electroplating by using insoluble anodes by passing the plating liquid through a filter machine and circulating the liquid between a plating cell and another cell for dissolving a metallic compd. CONSTITUTION:The concn. of the metallic ion in a plating liquid 12 decreases gradually if a material 13 to be plated is electroplated by using insoluble anodes 11, 11 in a plating cell 1. The concn. of the metallic ion or the rate of plating deposition is continuously or intermittently measured in this case. For example, the quantity of electricity is detected with a watthour meter 16 and a signal is emitted to a tank 18 for measuring and supplying a metallic compd. from a control device 17 at every attainment of the preset prescribed electric quantity value so that the metallic compd. is added to a vessel 2 for dissolving the metallic compd. The plating liquid is circulated through the cell 1 the tank 2 a filter machine 8 the cell 1 by the signal from the device 17 at the same time or upon lapse of prescribed time and the circulation of the plating liquid is stopped after the time enough for the thorough dissolution of the metallic compd. added to the liquid.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electroplating method using an insoluble anode, and more specifically to a method of performing electroplating while maintaining the amount of metal ions in a plating solution within a predetermined range.

As is well known, in electroplating, metal ions in the plating solution are reduced and precipitated as gold maple on the object to be plated, which is the cathode. Therefore, as plating progresses, the concentration of metal ions in the plating solution decreases. However, when using a soluble anode made of the same metal as the metal ions in the plating solution, the soluble anode electrochemically dissolves and replenishes the metal ions in the plating solution, resulting in Even as plating progresses, the metal ion concentration in the plating solution does not change significantly. However, depending on the type of electroplating, an insoluble anode may be used, but since an insoluble anode cannot dissolve and supply the metal ions necessary to the plating solution, the metal ions in the plating solution decrease as plating progresses. To go.

Therefore, it is necessary to replenish the missing metal ions in the plating solution as a metal salt or the like.

Conventionally, chromium plating is typically known as electroplating using an insoluble anode, but chromium plating is usually applied as thin as 0.2 to 0.3μ, and therefore Since the amount of decrease in metal ion concentration was small, it was sufficient to replenish the necessary chemicals before or after plating work started. Of course, in the case of hard chrome plating, it is plated to a thickness of several microns to several tens of microns, but in this case, the amount of material to be plated is generally reduced in proportion to the amount of plating liquid. Therefore, even in the case of hard chrome plating, the amount of decrease in metal io/a degree is small, and it is sufficient to replenish chemicals before and after plating work.

However, soluble anodes have traditionally been used in copper plating, nickel plating, etc., but as mentioned above, soluble anodes dissolve and decrease as plating progresses, so they must be replaced with appropriate anodes. There must be. In this case, if the plating tank or plating equipment was complex or large, it would be very troublesome to replace the heavy anode material, so insoluble anodes were also used for these platings. It is desirable to adopt a method that eliminates the trouble of replacing the anode and replenishes the consumed metal content in the plating solution by replenishing chemicals. Furthermore, when using a soluble anode, the shape of the anode gradually changes as the soluble anode melts, but this also changes the flow direction of the current toward the object to be plated. Variations in the plating film thickness are likely to occur when the shape changes. In particular, when plating on grid/grid wiring boards or through-hole plating, variations in plating film thickness can cause problems with product reliability, so it is important to reduce variations in plating film thickness. Therefore, by using an insoluble anode, the current flow is always the same by eliminating changes in the shape of the anode, thereby reducing the plating film thickness due to changes in the shape of the anode. Although it is desirable to eliminate variations, the present inventors have found that when performing plating such as copper plating and nickel plating using an insoluble anode, the consumption of gold ions in the plating solution is large. Since the amount of gold ions decreases significantly as plating progresses, it becomes necessary to replenish the metal ions consumed during plating.

In this case, if relatively highly soluble chloride or sulfate is used as the metal compound to be replenished, chloride ions and sulfate ions may accumulate in the plating solution, which may impede plating. As the metal compound for replenishing, it is preferable to use oxides, hydroxides, etc. so that anions are not accumulated. However, these metal compounds generally have poor solubility and require a certain amount of time to dissolve in the plating solution. For this reason, if metal compounds such as oxides and hydroxides are directly added to the plating solution in the plating tank during plating work, the undissolved metal compounds will adhere to the surface of the plated object and cause problems such as roughness. In order to avoid this, the plating operation must be stopped until the metal compound is completely dissolved when the metal compound is added.

In view of the above circumstances, the present inventors have investigated a method for plating with as little variation in metal ion concentration in the plating solution as possible when performing electroplating using an insoluble anode. A plating tank and a metal compound dissolving tank are provided separately, and these tanks are connected to each other so that the plating solution can circulate therebetween.

The metal ion concentration or the amount of plating precipitation in the plating solution is measured continuously or intermittently, and when the measured amount reaches a predetermined set value, a predetermined amount is added to the plating solution in the metal compound dissolution tank. Added gold nugget compound.

By dissolving the plating solution and supplying the plating solution to the plating tank through a filter, it is possible to reduce fluctuations in the metal ion concentration in the plating solution and eliminate roughness, thereby achieving good plating. This has led to the present invention.

The present invention will be explained in more detail below with reference to the drawings.

In the plating method of the present invention, a plating cypress in which an insoluble anode is disposed and a metal compound dissolving tank are connected to each other so that a plating solution can be circulated, and the object to be plated is electroplated in the plating tank. , the gold ion concentration or the amount of plating precipitation in the plating solution is measured continuously or intermittently, and when the measured amount reaches a predetermined set value, a gold nugget compound is added to the plating solution in the metal compound dissolution tank. It is characterized in that a predetermined amount is added and dissolved, and the plating solution is supplied into the plating tank through a filter.

The type of plating to which the method of the present invention is applied is not necessarily limited, but it is preferably employed when performing copper plating such as copper sulfate plating, nickel plating, etc.

The insoluble anode may be selected depending on the type of plating solution, etc.; for example, carbon, platinum, platinum-plated titanium,
Lead, lead alloys, etc. may be used.

According to the present invention, by using an insoluble anode, 1
il) There is almost no need to replace the electrodes, so it is suitable when using a large plating tank where it is inconvenient to put in and take out the anode, and it is suitable for plating when installing an automatic plating line. It is possible to reduce the burden of having to consider the scaffolding when laying out the entire amount of anode from the phase, and it is possible to freely lay out the automatic plating line in a variety of ways. Furthermore, it is possible to eliminate variations in the plating film thickness due to changes in the shape of the anode, so it can be suitably used for plating printed wiring boards.

The drawing shows an example of an apparatus for carrying out the method of the present invention. In the drawing, 1 is a plating tank having a plating water tank 1a and an overflow tank 1b, 2 is a metal compound dissolution tank, and the overflow tank 1b is a plating tank. 1a and the metal compound vIJ dissolving tank 2 are in communication with each other through a drawn pipe 5 in which a bo/g 3 and a valve 4 are interposed, respectively, and this dissolving tank 2 is connected to the bo/g 6. The pulp 7j communicates with the plating water tank 1a of the plating tank 1 through a return pipe 9 in which a pulp filter 8 is successively inserted. In the plating water tank 1a, an insoluble anode 11.11 suspended from an anode busbar 10.10 is immersed in the plating solution 12, and an object to be plated 13 is suspended from a cathode busbar 14.
It is designed to be immersed in a plating solution 12. Furthermore,
An anode busbar 10.10 and a cathode busbar 14 are connected to the anode and cathode of a power supply (rectifier) 15 installed outside the plating tank 1, respectively, and a coulometer 16 is connected to this power supply 15. Measure the amount of air on the coulometer 16 (
Current x time) is detected, and a control device 17 connected to this coulometer 16 issues a signal when a predetermined value of electricity is reached. Also, dissolving metal compounds? A metal compound metering and supplying tank 18 is arranged above &2. Note that 19 in Figure 1 is a stirrer.

When carrying out the method of the present invention using this device.

Plating is performed by immersing the object to be plated 13 in the plating solution 12 in the main plating tank 1a, but since an insoluble anode is used as the anode, the concentration of metal ions in the plating solution 12 gradually decreases. . In this case, since the device is equipped with a coulometer 16 to detect the amount of electricity, it is set in advance.

To explain this point in more detail, 1. For example, in copper sulfate plating, the current efficiency is almost 100%, and even if the current efficiency is not 100%, in the case of ordinary electroplating, the current efficiency is almost constant. Therefore, by detecting the amount of electricity during plating, the amount of metal deposited by plating can be detected.

Therefore, the amount of metal ions consumed in the plating solution is detected. Therefore, each time a predetermined electricity quantity value (and therefore a metal ion consumption value) is reached, the metal compound metering tank 18 is sent to the control device 17.
A signal is given to the plating liquid in the metal compound dissolving tank 2 to add a certain amount of the metal compound from the supply tank 18 to the plating solution in the metal compound dissolving tank 2, and the stirrer 19 is operated to dissolve the metal compound. In this case, the amount of replenishment of the metal compound is a constant amount corresponding to the amount of metal deposition (-metal ion consumption) calculated from the preset electricity value. Then, at the same time as the addition of the metal compound from the supply tank 18 or after a predetermined period of time, the controller 17 sends a message to each valve 3, 6 and each valve 4.
．． 7 and the filter 8 to operate them;
The plating solution 12 in the plating tank 1 is transferred to its overflow tank 1.
Pull out the pipe from b5. Dissolving tank 2. Return pipe9. Plating water tank 1
After a predetermined period of time (sufficient time for the metal compound added to the melting tank 2 to be completely dissolved), the control device 17 sends the
, valves 4, 7. When the operation of the filter 8 is stopped, the pulps 4 and 7 are kept in an open state.

The operation and stop of the filter 8 may be controlled by a signal from the control device 17, and the metal compound is added to the filtration tank 2 while the filter 8 is stopped.

It may also be dissolved.

Therefore, according to the above-mentioned replenishment method, the replenishment amount of the metal compound is the amount of metal deposition calculated from the preset amount of electricity,
Therefore, since the amount corresponds to the amount of metal ions consumed in the plating solution 12, the metal ion concentration in the plating solution returns to the original concentration before consumption by replenishing this metal compound. The decrease in metal ion concentration is reliably compensated for, and plating defects due to a decrease in metal ion concentration are reliably prevented.

In addition, when replenishing metal compounds, metal oxides, metal hydroxides, etc. are preferable as the metal compound in order to prevent the accumulation of anions in the plating solution, but these compounds are extremely soluble. bad. However, in the present invention, as is clear from the embodiment shown in FIG.
Separately, a gold PA (hypothecide dissolving tank 2) is provided, a metal compound is added to this dissolution tank 2, and the metal compound is dissolved therein. Since the plating solution is returned to the plating wooden barrel 1a through the filter 8, even if undissolved metal compounds are present in the plating solution, these undissolved components are filtered through the filter 8. It is not captured and mixed into the plating solution in the metal water tank 1a, and therefore metal compounds with poor solubility such as oxides and hydroxides can be effectively used for replenishment. Even if a metal compound with poor solubility is replenished during plating, the undissolved content will not mix into the plating solution in the plating wooden barrel 1a, so the deposited plating film will not be rough, and the plating will be smooth. In addition, the undissolved portion of the metal compound captured during the vEi process gradually dissolves as the plating solution passes through the filter, so the added DO All of the metal compounds deposited will be dissolved, ensuring that the planned amount of replenishment will take place.

Note that the method described above uses a coulometer to detect the amount of gold ion consumption in the plating solution by detecting the amount of electricity, but the method for detecting the amount of metal ion consumption is not limited to the above method. One example is when the total area of the object to be plated is constant and the current sensitivity is also constant.

A timer may be used to replenish the metal ion compound at predetermined time intervals, or an automatic analyzer may be used to measure the metal ion concentration in the plating solution, and if the measured concentration value is less than the set concentration, The above-mentioned replenishment may also be performed. Furthermore, the pump and pulp by the control device 7-, ,
,! Jfk's work is not limited to the above method.

EXAMPLES Hereinafter, the present invention will be specifically explained using examples, but the present invention is not limited to the following examples.

(Example) Plating solution composition: Cu5O, 5H202209'/13H280,60
PI3 Plating solution volume: 120OA Plating tank 10001 Dissolution tank 1007? Circulatory system 1001 Plating solution temperature = 25°C Anode: Platinum-plated titanium mesh, flow rate: 100OA Copper compound for replenishing copper ions: Copper oxide (CUO, purity 98%) Using the device shown in the figure under the above conditions, Total electrolysis amount 50000A
Electrolysis of H was performed. Oxidized steel was replenished every 100 OAH, and the dissolved state of copper oxide was checked by chemically analyzing the composition of the plating solution. In this case, ioo.

Theoretically, the copper ions consumed in the electrolysis of A) 1 are 1.184
Kf is used, and the amount of copper oxide supplied is 1 corresponding to this theoretical amount.
, 5 confusion.

First, oxidized steel was added to the melting tank at the same time as electrolysis started, and melting was performed by stirring. A signal (coulometer) was transmitted to the filter by electrolysis at 500 AH, and the filter was started to start circulating the plating solution. In addition.

Bonog and pulp were kept in working condition during plating. after that,
Further, the filter was stopped by electrolysis at 500 AH, and copper oxide was again added to the dissolving tank to perform dissolution. During this cycle, replenishment of monochrome steel was continued, and the plating solution was analyzed every 5 cycles to obtain the results shown in Table 1. As can be seen from the table, the above replenishment method allows plating to be carried out with extremely little change in the composition of the copper silosulfate plating solution.

As explained above, according to the present invention, a plating tank in which an insoluble anode is disposed and a metal compound dissolving tank are connected to each other so that the plating solution can be circulated, and the plating tank is plated in the plating tank. thing? I- While electroplating, the concentration of metal ions in the plating solution or the amount of plating precipitation is measured continuously or intermittently, and when the measured amount reaches a predetermined set value, the plating in the metal compound dissolution tank is determined. A predetermined amount of a metal compound is added to the plating solution and the metal compound is bath-dissolved, and during plating, the poorly understood metal compound can be replenished without any problem, and fluctuations in the metal ion concentration in the plating solution can be minimized. , and can perform good plating without roughness.

[Brief explanation of drawings]

The drawing is a schematic diagram showing an example of a plating apparatus used for carrying out the present invention. 1... Plating tank, 2... Metal compound dissolution tank, 8...
-Filter, 15...electrodeposition meter, 18...control device. Applicant Uemura Kogyo Co., Ltd. Agent Patent Attorney Takashi Kojima

Claims (1)

[Claims] 1. Connect a plating tank in which an insoluble anode is installed and a gold maple compound dissolution tank so that the plating solution can circulate between them, and electroplate the object to be plated in the plating tank, while also dissolving the plating solution in the plating solution. The metal ion concentration or the amount of plating precipitation is measured continuously or intermittently, and when the measured amount reaches a predetermined set value, a predetermined amount of the metal compound is added to the plating solution in the metal compound dissolution tank and dissolved. . A plating method, characterized in that the plating solution is supplied into the plating tank through a filter.