JPS596920B2 - Multi-method partial plating equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a practical multi-plating system that simultaneously processes multiple parts of an object to be plated, each having an extremely fine plating area, and maintains the plating uniformly in each part. The present invention relates to a partial plating device of the method.

In recent years, partial plating, in which only specific parts of a member to be plated are plated, has been regarded as important in terms of functionality and resource saving, and is indispensable especially in the electronic industry sector. As is well known, in integrated circuit elements, various semiconductor elements, miniaturized electronic components for mounting on printed circuit boards, display elements, highly integrated printed circuit boards, etc., resistance and reactance at each terminal, contact point, or electrode point are It is important to suppress unnecessary voltage drops, power losses, noise generation, changes in circuit time constants, and effects on other circuits.

For this reason, in each of the electronic components and printed circuit boards mentioned above, metals with high conductivity are used at specific locations such as electrodes, terminals, and contacts.
For example, it is necessary to use precious metals such as gold (At), platinum (pt), silver (Ag), rhodium (Rn), etc., but since these are extremely expensive materials, The plating process is performed using a partial plating method that allows plating only the necessary parts and requires only a small amount of plating base material.

This general partial plating means includes a plating liquid injection nozzle,
It has a mask that surrounds a specific part of the member to be plated, and this plating liquid spray nozzle and the member to be plated are used as electrodes.
The flux of gold layer ions in the plating solution is the sum of migration due to the electric field, diffusion due to concentration changes near the electrode, and convective movement proportional to the flux of the plating solution. Concentration changes will suppress the reaction rate and worsen current efficiency.

Therefore, the above-mentioned known means had the following defects.

(1) After the plating liquid collides with the surface to be plated, it is difficult to control the flux, so the wetted area of the plating liquid spreads to the area larger than the opening area of the mask, and only the tiny area that is truly needed is covered. It is difficult to plate accurately.

(2) The amount of metal ions supplied in the plating solution is low;
Since the current density is low, on the order of 20 to 30 A/Dm°, the plating process takes a long time, and the current fluctuations during the plating process are large, so that the plating thickness tends to be non-uniform.

(3) Even if plating is performed while masking according to the shape of the part to be plated, it is difficult to control the flow rate of the plating liquid, and there is also a limit to the distance adjustment between the nozzle and the part to be plated. Halation easily occurs, plating spots and plating boundaries sag, and the plating base material is also consumed more than necessary.

(4) When changing masks depending on the type of parts to be plated, the work of changing the mask is difficult, and it takes time to adjust the installation of nozzles, masks, etc., so it takes a long time to set up, and work efficiency is poor. It is not suitable for small-scale production.

(5) When performing continuous partial plating processing on a long private plating member such as a hoop material, the nozzle/mask system is also integrated into a multi-system along with the plating liquid supply control system, but when integrated into a multi-system, Variations in the distance between the part to be plated and the nozzle, as well as variations in the flow rate, flow rate, and intake/exhaust volume of the plating solution, are likely to occur, and these adjustments are difficult, making quality control of the plating quality of the plated product difficult. , which becomes a major obstacle in mass production.

(6) Since the plating time is long as mentioned above, the plating device as a whole becomes larger and the control system becomes more complicated, which increases equipment costs, increases the installation area, and makes maintenance troublesome. This becomes a big problem when constructing a new facility, expanding or renovating it, or relocating it.

(7) Coupled with equipment costs, yield deterioration due to variations in plating quality, operational personnel for process control and quality control,
Running costs are high because it requires man-hours, extra jigs, inspection equipment, etc.

On the other hand, the current carrying capacity of the above-mentioned electronic components is usually several μ.
Since the value is about A ~ number + MA, for example, a diameter of 11!711 or less and a thickness of several microns is sufficient for precious metal plating on the contact part, and a conductive part with a minute width, such as the lead frame of an integrated circuit element, is sufficient. If a large number of terminals are arranged in close proximity, it is sufficient to gold plate the terminals with a diameter of about 0.2 mm and a thickness of about 1 μm. In this way, only a small amount of partial plating is required, but with the partial plating method used in the United States, due to the problems mentioned above, the amount of expensive precious metal consumed is more than necessary, and the plating quality and precision are poor, and Since it lacked mass productivity, it was a major hindrance to the mass production of inexpensive products.

In view of the above-mentioned problems, we first decided to apply for patent application No. 1007 of 1972.
No. 72 (Japanese Unexamined Patent Publication No. 56-102590), ``Method and apparatus for plating small areas'' has been provided, which has made it possible to perform partial plating with high precision and high quality.

This will be explained below with reference to FIG.

A nozzle 2 for spraying pressurized plating liquid is detachably fixed to a jacket tube 5 having a chamber 3 having a predetermined capacity and a discharge tube 4 communicating with the chamber 3.

Further, a mask 7 in which a through hole 6 through which the tip of the nozzle 2 is exposed is detachably fixed to the top of the mantle tube 5, and a member 8 to be plated is attached to this mask 7 during the plating process. If they are placed so that they are in contact and are not plated,
The nozzle 2 is connected to the pole of a DC power source, and the member 8 to be plated is also connected to the pole. Further, the nozzle 2 is attached to a nozzle holder 911C provided at the bottom of the mantle tube 5 so as to be able to rise and fall freely.
The height of the nozzle 2 is adjusted by adjusting the nozzle holder 9. When melting metal or the like on the surface of the member 8 to be plated, that is, when reverse plating, the polarity of the DC power source may be reversed. A ventilation path 10 communicating with the outside air is formed in the mask 7, and when compressed gas (air or inert gas) is introduced, this ventilation path 10 is connected to external piping (not shown). Additionally, the exhaust pipe 4 communicates with an exhaust pump (not shown). In the plating device 1 described above, during the plating process, a negative pressure is created in the chamber 13 or the exhaust pipe 4 by driving the exhaust pump, and when DC power is applied, outside air or heat is discharged from the ventilation path 10. Pressurized gas is allowed to flow in, and plating liquid is injected from the nozzle 2. This plating liquid collides with the member to be plated 8 through the columnar mask 7 whose thickness approximates the inner diameter of the nozzle 2, but at this time, metal is deposited on the member to be plated 8, and the metal is deposited in the through hole 6. Corresponding partial plating is performed.

In addition, since the outside air or force gas flowing in from the ventilation path 10 is concentrated in the vicinity of the through hole 6 and flows into the chamber 13, diffusion of the plating liquid is prevented and the degree of concentration on the member 8 to be plated is reduced. Since the current density also increases, the plating quality improves and becomes stable.

Further, since the discharge pipe 4 to the chamber 13 are under negative pressure and outside air or pressurized gas flows in from the ventilation path 10, the plating liquid injected from the nozzle 2 is forcibly removed immediately after being used.

Therefore, the joint surface between the mask 7 and the member to be plated 8 gets wet and prevents the plating liquid from seeping into the outside, so that halation can be prevented.

On the other hand, since there is always a fresh liquid phase at the boundary between the part to be plated (solid phase j and the plating liquid (liquid phase)), the thickness of the diffusion layer that tends to occur at this boundary becomes extremely thin and the ion concentration becomes uniform. This is equivalent to forming an electrolyte column formed only by the electric resistivity inherent in the plating solution, and the current value is stabilized at a steady state, so the metal deposition rate is also stabilized and high-quality plating can be obtained.

As described above, the plating device 1 that is the basis of the present invention is extremely effective, but when it is made into a multi-system, another problem arises. For example, when plating minute parts of each inner lead of an IC lead frame, it is necessary to process multiple parts at the same time in order to greatly increase the plating work efficiency. If a large number of lead wires are arranged to correspond to the objects to be plated, the gap between the inner leads, which are the objects to be plated, will be narrow. It is impossible to arrange the nozzles corresponding to each target because the outer tube becomes a hindrance.

Therefore, a mask in which a large number of through holes are drilled individually corresponding to the objects to be plated is attached to a relatively large outer tube, the inside of this outer tube is brought into a negative pressure state, and each through hole is opened. It is contemplated to arrange a number of nozzles in a row corresponding to the holes and to connect the ends of the nozzles to a single plating liquid feed pipe.

However, there are subtle differences in piping capacity and impedance of each nozzle and the plating liquid supply pipe that communicates with it, and uneven fluid resistance due to the machining accuracy of each nozzle and connections...
. . . etc., the flow rate and flow rate of the plating liquid from each nozzle vary, making it difficult to perform uniform plating at each point, resulting in a decrease in yield.

In addition, when adjusting the distance between the nozzle and the object to be plated (distance between poles), when using the above-mentioned plating device, the nozzles are arranged close to each other and the elevating rock is attached to each, so the entire device is However, it is difficult to adjust each nozzle individually, and it is necessary to compromise on an average adjustment range for each nozzle. Therefore, when processing in mass production, there is a problem that it is difficult to efficiently perform high-precision and high-quality plating processing.

Furthermore, if the nozzles are arranged close to each other, the plating liquid streams injected from the nozzles interfere with each other, resulting in uneven plating current density distribution.

In other words, the center flow velocity of the injected plating liquid flow is higher than the outer circumferential flow velocity, so the plating liquid flow tends to expand at the outer circumference. The shape of the column is easily deformed, the plating liquid concentration becomes uneven, and the plating current density distribution becomes uneven.

On the other hand, if the plating device is used as is, there is no control function for the plating liquid flow once injected from the nozzle, so the above state cannot be regulated.

In the plating device, an outside air introduction groove is formed near the through hole of the mask, but the outside air flowing in through the groove only stirs the plating liquid, and it is impossible to control the state of the plating liquid flow. be. The present invention has been made in view of the above-mentioned problems, and is a multi-method partial plating method that can improve mass productivity without impairing the effectiveness of the basic invention, even when multi-systems are used. The aim is to provide the equipment. That is, the main object of the present invention is to form a sealed space around the object to be plated using a mask, and to spray the plating liquid inside the space to plate only a specific part. By supplying gas from the outside in the tangential direction of The purpose of the present invention is to provide a multi-type partial plating device that corrects for A special pedestal for the mask body, which has a long groove that introduces the
The plating quality is highly stabilized by having multiple nozzles arranged facing each other, and by polishing the top surface of the nozzles and adjusting the distance between the electrodes to suppress current fluctuations in each nozzle. It is possible to accurately adjust each nozzle and maintain the same state.

Next, an embodiment of the present invention will be described with reference to FIG. 2 and subsequent figures. The mask 10 is composed of a plurality of members, including a mask body 11 and a pedestal 12. The mask body 11 is formed of a thin plate of ceramic or the like, and has a large number of parts according to the plating pattern of the member to be plated. A through hole 13 is bored, and a conical countersink 14 is formed on the back side of the through hole 13 (on the nozzle side to be described later).

The pedestal 12 is for fixing the mask body 11, and is made of a relatively thick material such as stainless steel plate or ceramic in the shape of a flat plate. In addition, a hole 15 having a larger diameter than this is bored.

A plurality of long grooves 16 are bored in the tangential direction of each hole 15, and communicate with the outside air or a pressurized gas supply path (not shown). Set according to the type and object.

That is, the cross-sectional area of the long groove 16 is adjusted by polishing to control the flow rate and flow rate of the outside air or high-pressure gas, and the couple force exerted by the outside air or high-pressure gas on the plating liquid column.

As a result, the jetted plating liquid flow becomes a swirling flow and is formed into a beam shape with almost no expansion.

This makes it possible to maintain a state in which the plating liquid flows do not interfere with each other. This increases the high-speed stirring effect of the plating liquid on the surface to be plated and the efficiency of removing the plating liquid after use, and prevents infiltration to the outside at the joint surface between the member to be plated and the mask body 11. The effect can be increased.

Therefore, adjusting the cross-sectional area of the long groove 16 is an important means for the present invention.

Yes, the means for adjusting the cross-sectional area of the long groove 16 is not limited to polishing, and may be varied by using other means such as an intervening means such as a spacer (not shown). It is also set appropriately according to the plating target.

The pedestal 12 and the mask body 11 are bonded together using an epoxy resin adhesive or the like to form the mask 10.

On the other hand, the nozzle part 17 that injects the plating liquid is connected to the outer tube 18.
The through hole 13 is removably fixed in the chamber 19 of the base 20 and is integrally formed of a metal such as platinum.
An injection port 21 corresponding to the above is bored.

A discharge port 22 is communicated with the chamber 19.

The mask 10 is detachably fixed to the opening of the mantle tube 18, and if necessary, guide holes 23 and guide pins 24 are provided in the mask 10 and the mantle tube 18, and accurate positioning is achieved by fitting them together. It may be possible to do so.

Next, the operation will be explained based on the above configuration.

First, the upper surface of the base 20 of the nozzle section 17 is cut and polished by a predetermined amount for each injection port 21 in advance to finely adjust the distance to the member to be plated (interelectrode distance'). Incidentally, in the case of conventional static bath plating, as shown in Fig. 4, the plating current 1 and the energization time t vary exponentially, but when the distance l between the electrodes is varied as in this example, , this becomes the parameter, and the distance between the electrodes is 1, 1', 17...
A plating current characteristic of a predetermined level corresponding to (l''kl'kl...) can be obtained.

(See Figure 5) As mentioned above, since the variation in the flow rate of the plating liquid at each injection port 21 is minute, the amount to be polished as described above is also minute, so such adjustment work is easy. can.

Furthermore, the adjustment accuracy is considerably high since the difference in flow velocity is absorbed by the difference in height of the injection port 21. Now, exclusion port 22
, the inside of the chamber 19 is brought into a negative pressure state, and each injection port 2 is
1 supplies the plating liquid, and the long groove 1611C supplies outside air, pressurized air, inert gas, etc., respectively.

First, a couple acts on the outer circumferential surface of the plating liquid flow injected from each injection port 21 to the workpiece to be plated through the hole 15 or the through hole 13 due to the gas flowing in from the long groove 16, and the outer circumference The flow becomes a columnar swirling flow and becomes a beam shape in which diffusion is prevented. This enables more accurate spraying to the through holes 13 than simply preventing the plating solution from spreading, as in the case of the basic invention.

The plating liquid that has collided with the member to be plated in this way is then forcibly removed from the removal port 22 by negative pressure.
The plating liquid hardly wets any other parts of the mask body 11, and the leakage of the plating liquid to the outside is almost completely suppressed to prevent halation, and accurate partial plating on a minute area is possible. In addition, since the height of each injection port 21 is adjusted in advance, even if there is a difference in flow velocity at each injection port 21 due to flow path impedance, etc., this can be compensated for by the distance between the electrodes and a constant current can be maintained. As a result, metal deposition takes place under
Coupled with the action of applying a couple to the plating liquid column, the cross section of the plating layer becomes mesa-shaped, and a high-quality plating with a uniform thickness can be produced in a very short time.

Therefore, plating with a uniform thickness is possible even on very small areas with very close spacing, and according to the experimental results obtained by the present inventor, the spacing is 0.611r! ! l and diameter 0.21r
! It was also determined from microscopic photographs that plating of 11 small circular parts was possible on a mass production basis, and that a mesa-shaped plating layer with a plating thickness of 1 μm was produced.

In this way, it is possible to apply the truly necessary amount of plating to the lead frames of integrated circuit devices such as ICs and LSIs on a mass production basis, which greatly reduces the consumption of expensive precious metals. I can agree with you. However, when performing the above-mentioned plating on a lead frame such as an IC, in order to simultaneously process a large number of fine parts to be plated that are close to each other, holes 13 in the mask body 11 are formed in correspondence with the parts to be plated.
It is important to strictly control the positional relationship of the nozzle portions 17 and the processing accuracy of each.

Also, when plating using such a multi-method,
It is necessary to monitor whether the plating processing is being performed accurately and reliably in a large number of plating processing sections.

Therefore, the master 10 requires precision machining, as well as resistance to plating liquid and electrical insulation.

Generally, plastic products are used for partial plating masks, but in this embodiment, the above-mentioned through holes 13 are bored in a ceramic plate to provide a high degree of processing precision and a high degree of durability. It is possible to carry out a very large amount of highly accurate multi-point partial plating, such as on lead frames of ICs, etc., and to maintain a high level of plating quality. In addition, as shown in FIG. 6, a mask body 11' according to another embodiment includes a metal plate 31 having corrosion resistance, such as a stainless steel plate, in which a through hole 13' corresponding to the object to be plated is drilled in advance. However, the outer surface of the metal plate 31, including the inner peripheral surface of the through hole 13', may be coated with a coating material 32 having the same performance as ceramic. On the other hand, the nozzle section 17 for spraying the plating solution is used as an anode during the plating process and also as an electrode terminal for monitoring, so in this embodiment, as described above, an insoluble material is used. A base 20 made of metal, for example, platinum, is provided with a fine injection port 21.
In the case of a multi-system, a large number of the bases 20 are installed in series, and an insulator (not shown) is interposed between each base.

As another embodiment, as shown in FIG. 7, a necessary number of injection ports 2V are drilled in advance at predetermined intervals or positions in a block 41 formed of an insulating material such as ceramic, and the injection ports 2V are After metallizing the inner peripheral surface of the opening 2V and predetermined locations on both the upper and lower opening ends, platinum is applied by electroless plating to form the anode portion 42. This polishes the opening of the upper injection port 21/, which can prevent the inside and opening of the injection port 21' from being immersed in the plating liquid, and adjusts the distance between the electrodes and the member to be plated. The anode section 42 of can be used as a detection electrode during monitoring.

As mentioned above, in the case of the multi-method, each injection port 21, 21
It is extremely important to fine-tune the distance between the electrodes by polishing each time to maintain the quality of the plating, but it has high precision polishing power, high durability, and good insulation properties. Since the main material is ceramic, it can be said to be superior in terms of practicality and cost compared to those processed into platinum blocks. In this way, in the multi-nozzle section 17, it is possible to electrically install a monitor (not shown) for each injection port 21, 21', so that plating liquid can be applied to any one of the large number of injection ports 21, 2V. Even if a plating failure occurs due to the plating liquid not being injected or the plating liquid flow rate or flow velocity changing, it can be reliably detected. Of course, the present invention is not limited to the above-mentioned embodiments, and the arrangement of the nozzle portion, through holes, etc., the form and cross-sectional shape of the long grooves, the material shape of each element, etc. may be changed within the technical scope. can also be changed.

As described above, according to the present invention, the flow velocity of the plating solution in the nozzle part is absorbed by the distance between the electrodes, the plating target area is set by the mask body, and the plating liquid column is prevented from accidentally entering the plating liquid column by the pedestal fixed to the mask body. Since the above-mentioned members are designed to apply force and are detachable and replaceable depending on the object to be plated, the following effects are achieved. (1
) Accurate plating can be performed on areas that are close to each other at minute intervals and on extremely small areas.

(2) Since the flux of the plating liquid becomes beam-shaped and the flow rate is stable, there is no current fluctuation even with a plating liquid of low current density, and high-quality plating with uniform plating thickness can be achieved. (3)
Regardless of the size of the object to be plated, it is possible to prevent halation at the plating boundary, so even many minute objects to be plated in extremely close proximity can be plated with sharp images.

(4) It is extremely easy to replace and set the mask and nozzle corresponding to the object to be plated, and the workability including the setup process is excellent.

(5) In addition to being able to continuously plate many parts at the same time, there is no change in adjustment even during the mass production process, so plated products of stable quality can always be obtained in large quantities, and the plating process cost can be greatly reduced. (6) Since the entire device including the mask and nozzle can be downsized, the installation cost of the device is low and maintenance is easy.

(7) Since the yield of plated products is greatly improved and no special process control or quality control is required, running costs are also low.

(8) In a multi-system, differences in the flow rate of plating liquid from individual nozzles are compensated for by fine adjustment of the distance between the electrodes, resulting in extremely high-quality plating for a large number of objects and eliminating individual variations. Can be processed.

(9) Since the plating layer has a mesa-shaped cross section and can be plated in an extremely small area, it is particularly suitable for partial plating of integrated circuit elements, etc., and reduces the amount of consumption of precious metals that are the plating base material. Together with the effects mentioned above, it is possible to save resources and significantly reduce plating processing costs.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional front view of main parts showing the configuration of a plating device according to a known invention that is the basis of the present invention, and FIG. 2 is an exploded perspective view showing a multi-type partial plating device according to an embodiment of the present invention. FIG. 3 is a longitudinal sectional front view of the same. Furthermore, Fig. 4 is a characteristic diagram showing the correlation between plating current and energization time in conventional static bath plating, and Fig. 5 is a characteristic diagram showing the correlation between plating current and energization time in the micro-part plating device according to the present invention, and between electrodes. FIG. 6 is a longitudinal sectional view of a main part of a mask main body according to another embodiment, and FIG. 7 is a perspective view of a nozzle section according to another embodiment. 10...Mask, 11...Mask body, 12. ．． ．． ...
Pedestal, 13... Transparent 15... Hole,
16...Long groove, 17...Nozzle part, 1
8... Mantle pipe, 19... Chamber one,
20...Base 21...Injection port,
22... Exclusion port.

Claims (1)

[Scope of Claims] 1. A mask body in which a through hole is formed corresponding to the plated object, a hole corresponding to the through hole and a hole tangentially communicating with the hole and having a variable cross-sectional area and/or shape. A pedestal with a flexible long groove is fixed to the pedestal in a removable manner, and a mantle tube is connected to the pedestal to form a sealed space.The inside of the sealed space is made to have a negative pressure and the plating solution is expelled in a gas-liquid mixed state. an arbitrary number of injection ports whose terminal ends communicate with the plating liquid supply pipe are formed corresponding to the holes, and the upper end surface of each injection port can be individually cut and polished. A multi-type partial plating device with a nozzle section. 2. The multi-system partial plating apparatus according to claim 1, wherein the mask main body is a ceramic plate with through holes corresponding to the objects to be plated. 3. The main body of the mask is characterized by having a through hole corresponding to the plated object formed in a corrosion-resistant metal plate such as stainless steel, and coating the outer surface with ceramic or a coating material having properties equivalent to this. A multi-system partial plating apparatus according to claim 1. 4. The multi-method partial plating according to any one of claims 1 to 3, wherein the nozzle part has an injection port formed in a base made of an insoluble material such as platinum. Device. 5. Claim No. 5, characterized in that the nozzle part is formed by drilling an injection port into a block made of an insulating material such as ceramic, metallizing the surface thereof, and then plating with an insoluble material such as platinum. The multi-method partial plating apparatus described in any one of items 1 to 3.