JP3368828B2 - Electroless plating equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electroless plating apparatus capable of arbitrarily controlling a plating film thickness. 2. Description of the Related Art Many device manufacturers are actively developing packages using a tape carrier as a substrate. In recent years, with the progress of miniaturization and high density of packages, the wiring processing pitch of TAB tape carriers has been increasingly miniaturized. For this reason, it has become difficult to make all the patterns conductive for performing electrolytic plating on the tape carrier and to cut off the conductive leads in the final step. Therefore, establishment of an electroless plating technique that does not require conductive wiring is desired. [0003] There are various requirements for the film thickness in the plating process, and the plating apparatus must be able to cope with the change in the film thickness. For example, when performing bonding to a gold (Au) / nickel (Ni) plating film, the tape material itself is soft in gold wire bonding performed to a TAB tape carrier, so a hard nickel (Ni) base film of 5 μm or more is required. In gang bonding, gold (Au) needs to have a certain thickness, but it is better that the Ni base film is thin. [0004] In electrolytic plating, plating is formed with a film thickness proportional to the current density. Therefore, the plating film thickness can be easily controlled by changing the current density. On the other hand, in electroless plating, the deposition rate changes depending on the temperature of the plating solution (plating solution temperature), so that the plating film thickness can be controlled by adjusting the plating solution temperature. For example, when phosphorus (P) is used as the reducing agent, the electroless Ni plating needs to be performed at a liquid temperature of about 90 ° C. This is because no chemical reaction occurs at 70 ° C. or lower, and plating does not precipitate. That is, in order to obtain a sound plating film by electroless plating, it is necessary to perform plating at a certain optimum temperature. FIG. 4 is an explanatory view of a conventional electroless plating apparatus. 21 is a material delivery device, 23 is a pretreatment tank, 24 is a Ni-P plating tank, 25 is an Au plating tank, 26 is a post-treatment tank, and 22 is a material winding device. The plating method using this apparatus is called a reel-to-reel method. The material to be plated, such as a tape carrier, is delivered from a material delivery device 21 and is subjected to a pre-plating process in a pretreatment tank 23. Then, a predetermined plating film is applied through the Ni-P plating tank 24 and the Au plating tank 25. After that, it passes through a post-treatment tank 26, and is subjected to a drying process and the like. [0007] In order to obtain a Ni-P plating film having a uniform thickness, it is necessary to keep the temperature of the plating solution constant at 90 ° C.
Then, it is necessary to perform plating treatment in each plating tank for a time set in proportion to the film thickness so that a predetermined film thickness is obtained. Therefore, depending on the material delivery speed,
In order to obtain a predetermined film thickness, the material must be immersed in the plating bath at a constant temperature for a necessary time, and the length of a specific plating bath must be set so that the material is immersed in the plating bath for a necessary time. is necessary. [0008] The conventional electroless plating apparatus has the following problems. As described above, the control of the plating film thickness in electroless plating is performed by the plating solution temperature. In the case of plating that emphasizes the characteristics of the resulting plating film, the plating layer is divided into several layers, and the temperature of the solution is raised only in the plating tank that causes the plating reaction. Therefore, it is necessary to circulate the liquid and control the film thickness. However, in this method, since the plating solution in each tank is completely divided, a device for controlling the pH, Ni concentration, reducing agent concentration, temperature, etc. of the plating solution is required for each tank. Reasonably, the apparatus is complicated and expensive, and is not practical. Accordingly, an object of the present invention is to solve the above-mentioned drawbacks of the prior art and to obtain an arbitrary plating film thickness without changing the temperature of the plating solution and the length of the plating bath.
It is to provide a simple and low-cost electroless plating apparatus. In order to achieve the above object, the present invention provides a plating tank, a reservoir tank for storing a plating solution, and a step of transferring the plating solution from the reservoir tank to the plating tank. In the electroless plating apparatus including a circulating pump, the plating bath is configured such that the plating solution is heated and
A plurality of tanks that are kept warm and tanks where the plating solution is not heated
And the reservoir tank is
A plating solution that is heated and kept warm and a plating solution that is not heated
Electroless configuration separated by removable shield
A plating apparatus is provided. FIG. 1 is an explanatory view showing a first embodiment of an electroless plating apparatus according to the present invention. 1 is a first plating tank, 2 is a second plating tank, 3 is a third plating tank, 4 is a first pump, 5 is a second pump, 6 is a third pump, 7 is a removable shielding plate, and 8 is plating An automatic liquid management device, 9 is a reservoir tank, 10 is a heating / heating plating solution, 11 is a non-heating plating solution, and an arrow penetrating the first plating tank 1, the second plating tank 2, and the third plating tank 3. Indicates a transport direction of a material such as a carrier tape material. The arrows on each pump and each plating tank indicate the flow of the plating solution. As described above, a problem of the conventional plating apparatus is that the material must be bathed in the plating tank at a constant optimum solution temperature and for a plating time corresponding to a desired film thickness. Was. Therefore, a plurality of sets (n sets: n is an integer) were prepared with one plating tank and one pump as one set, and the whole was connected to one reservoir tank 9. In the first embodiment shown in FIG. 1, n is set to 3, and the reservoir tank 9 is divided into two portions so as to reserve the heating / heating plating solution 10 and the non-heating plating solution 11.
It was divided by a removable shielding plate 7. In this state, the heating / warming plating solution 10 is circulated from the first pump 4 to the first plating tank 1. The unheated plating solution 11 is circulated through the second plating tank 2 and the third plating tank 3 by the second pump 5 and the third pump 6. By doing so, it can be divided into a plating tank in which the plating reaction proceeds and a plating tank in which the plating reaction is not performed. Unlike the case of the electroless plating apparatus in which the reservoir tank 9 is completely divided into n tanks, the plating solution automatic management device 8 for managing the composition, pH, and temperature of the components in the plating solution includes one set in the reservoir tank 9. Just install it. Therefore, cost reduction and simplification of the device can be achieved. When the temperature is to be increased, since n is 3, either the first plating tank 1 or both the first and second plating tanks, and all of the first to third plating tanks, The plating solution whose temperature always rises is controlled by the plating solution automatic management device 8. That is, the plating bath for raising the temperature always includes the first plating bath 1 and the plating solution automatic management device 8 is configured to be adjacent to the first plating bath 1. FIG. 2 is an explanatory view showing a second embodiment of the electroless plating apparatus of the present invention, and FIG. 3 is an explanatory view showing a third embodiment of the electroless plating apparatus of the present invention. The difference from the first embodiment is that in the second embodiment, the plating bath for raising the temperature is both the first plating bath and the second plating bath, and in the third embodiment, the plating bath for raising the temperature is from the first to the second. It is a three plating tank. The temperature of the plating solution is determined by the desired plating film thickness, the length of the tank for raising the temperature, and the material conveying speed. The temperature of the bath in which the plating is not performed is room temperature. By performing electroless plating in this state, plating can be deposited only in the plating bath where the temperature is raised, and no plating reaction occurs in the bath where the temperature is not raised, but the plating solution is circulated. Drying of the material can be prevented. The reason why the material is prevented from drying is to prevent the surface of the film from being oxidized and inactivated when another plating film is applied on the plating film. A plurality of sets of one plating tank and one pump are prepared as one set, and the whole is connected to one reservoir tank 9 so that a plating tank for raising the temperature and a plating tank for not raising the temperature can be provided. In the electroless plating process in the reel-to-reel system, the plating time can be controlled without changing the length of the plating tank. That is, it is possible to perform electroless plating with an arbitrary plating film thickness while keeping the plating solution temperature at the optimum temperature. Hereinafter, the results of the first to third embodiments will be described. An electroless Ni-P plating film was applied to a copper alloy lead frame material. The total length of the plating tank and the material transfer speed are 6 μm in the thickness of the conventional one-tank type electroless plating equipment.
The same as when m was obtained. That is, the thickness is 2 μm if plating in one tank, 4 μm if plating in two tanks, and 6 μm if plating in three tanks. In the first embodiment, the temperature of the Ni plating solution in the first plating tank 1 is 90 ° C., the temperature of the plating solution in the second plating tank 2 and the third plating tank 3 is room temperature (25 ° C.), and the plating film thickness is 2 μm.
The plating was performed with a target of m. In the second embodiment, the plating temperature of the first plating tank 1 and the second plating tank 2 was 90 ° C., the liquid temperature of the third plating tank 3 was 25 ° C., and plating was performed with a target of 4 μm. In the third embodiment, plating was performed at a target of 6 μm, with all the liquid temperatures in the first to third plating tanks being 90 ° C. Table 1 shows the results. [Table 1] In Table 1, the first conventional example is a single-tank type electroless plating in which the total length of the plating tank is the same as the tank length of the electroless plating apparatus shown in the first to third embodiments of the present invention. In this apparatus, the plating solution temperature was set to 73 ° C. in order to set the target plating film thickness to 2 μm. In the second conventional example, the plating solution temperature is set to 84 ° C. in order to set the target plating film thickness to 4 μm. The reference example is a case in which the plating solution temperature is 90 ° C. in the above-described one-tank type plating apparatus. In each of the first to third embodiments, it can be seen that the plating film thickness is in accordance with the target value. on the other hand,
As can be seen from the results of the first conventional example and the second conventional example,
In the case of the single-tank type plating apparatus, a film thickness almost as expected was obtained by controlling the temperature, but the P content was greatly different. From this, the electroless plating apparatus of the present invention was able to accurately control the plating film thickness and obtain a plating film with a low P content. In the first to third embodiments, the number of tanks is set to 3 (n = 3) for simplicity. However, by further increasing the number of n, an arbitrary film thickness can be obtained with higher accuracy. It is possible. In addition, although the example applied to the Ni plating tank was described,
The apparatus of the present invention is also useful as a method for controlling the thickness of Au plating. According to the electroless plating apparatus of the present invention, n sets of one plating tank and one pump are prepared as one set, and the whole is connected to one reservoir tank. Is divided by a removable shielding plate, and the following effects are exhibited by providing a plating tank for increasing the solution temperature and a plating tank for not increasing the solution temperature. (1) An arbitrary plating film thickness can be obtained without changing the total length of the plating tank and the plating solution temperature. (2) Drying of the plating film surface, which causes inactivation of the film surface, is prevented. (3) Regardless of the thickness of the plated film produced, the characteristics of the plated film are equal to or better than those obtained by the conventional apparatus. (4) One set of a plating solution automatic management device for automatically managing the composition, pH, Ni concentration, reducing agent concentration and temperature of the plating solution is sufficient.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory view showing a first embodiment of an electroless plating apparatus according to the present invention. FIG. 2 is an explanatory view showing a second embodiment of the electroless plating apparatus of the present invention. FIG. 3 is an explanatory view showing a third embodiment of the electroless plating apparatus of the present invention. FIG. 4 is an explanatory view of a conventional electroless plating apparatus. [Description of Signs] 1 First plating tank 2 Second plating tank 3 Third plating tank 4 First pump 5 Second pump 6 Third pump 7 Shielding plate 8 Automatic plating solution management device 9 Reservoir tank 10 Heating / heating plating solution 11 Non-heating plating solution 21 Material delivery device 22 Material take-up device 23 Pretreatment tank 24 Ni-P plating tank 25 Au plating tank 26 Post-treatment tank

Continuation of the front page (56) References JP-A-61-15979 (JP, A) JP-A-6-88246 (JP, A) JP-A-57-140870 (JP, A) JP-A-11-323566 (JP, A) , A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C23C 18/31

Claims (1)

(57) [Claim 1] Electroless plating comprising a plating tank, a reservoir tank for storing a plating solution, and a pump for circulating the plating solution from the reservoir tank to the plating tank. In the apparatus, the plating bath is heated and heated by the plating solution.
A plurality of tanks that are kept warm and tanks where the plating solution is not heated
And the reservoir tank is provided with a plating solution to be heated and kept warm.
Unheated plating solution with removable shield
An electroless plating apparatus having a separate configuration .