JP3417809B2 - Plating method, plating apparatus and lead frame manufacturing method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plating method and a plating apparatus for plating a strip-shaped frame, and a lead frame manufacturing method including a plating step in the manufacturing process.

[0002]

2. Description of the Related Art Conventionally, when a strip-shaped frame is plated, a plating tank 4 having an anode 40 is provided as shown in FIG.
First, a method has been used in which the strip-shaped frame 42 is transported while being in contact with the cathode 44 to which power is supplied from the power supply unit 43, and plating is performed.

[0003]

However, when plating is performed with a constant current and transport speed, when either the front end or the rear end of the strip-shaped frame is in the plating tank, Since the strip frame area is smaller, the current density flowing in the strip frame is higher,
As the current density becomes higher, the plating thickness becomes thicker.Therefore, when the plating area is small, the longer the plating time is, the thicker the plating thickness becomes. The closer the ends of the strip frame are to the end, the higher the current density becomes. However, there is a problem that the plating time becomes longer and the plating thickness becomes thicker, resulting in a difference in the plating thickness between the front end portion and the rear end portion of the strip-shaped frame and other portions.

Further, when the area of the strip-shaped frame in the plating tank at the time of loading the strip-shaped frame and when discharging the strip-shaped frame is extremely small, the current density is remarkably increased, which causes a burn defect.

The present invention has been made in view of the above problems, and it is possible to reduce the difference between the plating thickness of the front end and the rear end of the strip-shaped frame and the plating thickness of other portions, and to prevent burn defects. An object of the present invention is to provide a plating method, a plating apparatus, and a lead frame manufacturing method that can be performed.

[0006]

A plating method according to the present invention is a plating method in which a strip-shaped frame to be conveyed is continuously plated using a plurality of plating tanks. And an electrode connected to a different power supply unit near the strip frame discharge port, and one power supply unit via the electrode to the strip frame of the plating tank in which the front end or the rear end of the strip frame exists. Power is supplied from the plurality of power supply units via electrodes to the strip-shaped frame of the plating tank in which strip-shaped frames other than the front end and the rear end are present to perform plating. .

Further, the strip-shaped frame has an unnecessary portion on at least one of the front end portion and the rear end portion.

In the plating tank, the length of the strip-shaped frame in the carrying direction is shorter than that of the unnecessary portion.

Next, the plating apparatus according to the present invention is a plating apparatus for continuously plating a strip-shaped frame using a plurality of plating tanks while transporting the strip-shaped frame. It has a plurality of cathodes provided near the mouth and near the strip frame outlet and connected to different power supply units, and an anode provided in the plating tank and connected to the plurality of power supply units.

Further, the anode is connected in parallel with a plurality of power supply units.

In the plating tank in which the leading end portion or the trailing end portion of the strip-shaped frame exists, the strip-shaped frame is supplied with power from one power supply unit to perform plating, and strips other than the leading end portion and the trailing end portion are stripped. In the plating tank in which the strip-shaped frame is present, the strip-shaped frame is supplied with power from a plurality of power supply units to perform plating.

A method of manufacturing a lead frame according to the present invention is a method of manufacturing a lead frame in which a base material of a lead frame to be conveyed is continuously plated by using a plurality of plating tanks. An electrode connected to a different power supply unit is provided near the mouth and near the strip frame outlet, and one power supply unit is provided through the electrode to the base material of the plating tank in which the front end or the rear end of the base material exists. Is used to perform plating, and plating is performed by supplying power from a plurality of power supply units to the base material of the plating tank in which the base material other than the front end portion and the rear end portion exists via electrodes.

Here, the plating is palladium plating.

[0014]

[0015]

[0016]

Embodiments of the present invention will be described below.
A detailed description will be given with reference to the drawings.

As shown in FIG. 1, the plating apparatus according to the embodiment of the present invention comprises a plurality of plating tanks 1 for plating the same metal, and the strip-shaped frame 2 to be plated has a final end and a rear end. Is formed with an unnecessary portion 3 that does not include a product portion, and the length of the plating region of each plating tank in the transport direction is greater than the length of the strip-shaped frame 2 in the transport direction of the non-product portion 3. It's getting shorter.

In the plating method of the present embodiment, the strip-shaped frame 2 is conveyed by a feed roll, and plating is successively performed in each plating tank 1 to form a plating layer on the strip-shaped frame 2.

According to this embodiment, since the plating tank is divided into a plurality of parts, the length of each plating tank in the feeding direction can be shortened, and the strip-shaped frame end portion is formed in the plating area of the plating tank. When only one of them is present, that is, when the plating area is small, the area of the strip-shaped frame 2 to be plated becomes small, so that the current density can be made different due to the difference in the plating area, and the range in which the difference in the plating thickness can be made is short. can do.

Further, since the length of the plating region in the transport direction is shorter than the length of the unnecessary portion 3 in the transport direction, which does not include the final product portion at the leading end and the rear end of the strip-shaped frame 2. As the final product does not have the part where the plating thickness is different, it does not affect the product.

If the length of the plating tank 1 in the conveying direction is shortened, the plating time and the plating thickness are made the same.
In order to increase the current density, the current must be increased, which may cause burn defects.However, since a plurality of plating tanks are provided and plating is performed in a plurality of steps in this embodiment, the current Can be made small and such a problem does not occur.

As shown in FIG. 2, the plating apparatus according to another embodiment of the present invention is a constant current source, and a first rectifier 11 and a second rectifier 12 that output the same amount of current are provided as independent power supply units. It is provided as a plating tank 13
The first cathode 14 to which power is supplied from the first rectifier 11.
And a second cathode 15 to which electric power is supplied from the second rectifier 12 are installed at the strip frame inlet and the strip frame outlet, respectively, and the anode of each rectifier is the anode 16 and the anode 17 in the plating tank. It is connected.

The strip-shaped frame 18 to be plated
Is transported by the transport roll 19, contacts the first cathode 14 at the strip frame inlet and contacts the second cathode 15 at the strip frame outlet, and is continuously plated while being transported. It

Next, in the plating method of this embodiment, first,
As shown in FIG.
The strip-shaped frame 18 is brought into contact with the first cathode 14 at the strip-shaped frame loading port, and the tip of the strip-shaped frame 18 is loaded into the plating tank 13.

At this time, the strip frame 18 contacts only the first cathode 14, and the current is supplied only from the first rectifier 11.

Next, as shown in FIG. 3, the strip-shaped frame 1
8 is further conveyed, comes into contact with the second cathode 15 at the strip-shaped frame outlet, and penetrates the plating tank 13.

At this time, the strip-shaped frame 18 contacts the first cathode 14 and the second cathode 15, and the current is supplied from the first rectifier 11 and the second rectifier 12.

Next, as shown in FIG. 4, the strip-shaped frame 1
8 is further conveyed and the rear end of the strip-shaped frame 18 is put into the plating tank 13.

At this time, the strip-shaped frame 18 contacts only the second cathode 15, and the current is supplied only from the second rectifier 12.

Next, the strip-shaped frame 18 is further conveyed, the rear end of the strip-shaped frame 18 is discharged from the strip-shaped frame discharge port, and the plating is completed.

According to the above embodiment, when only one of the ends of the strip-shaped frame 18 is in the plating tank 13, that is, when the plating area in the plating tank 13 is small, only one cathode is brought into contact. However, current is supplied from only one rectifier, but the strip-shaped frame 18 is used for the plating tank 13
Only when it penetrates, that is, when the plating area in the plating tank 13 is maximum, the two cathodes come into contact with each other, and current is supplied from the two rectifiers.

Therefore, the first rectifier 11 and the second rectifier 1
Assuming that the amounts of currents output from 2 are equal, when the plating area in the plating tank 13 is small, only half the current flows when the plating area in the plating tank 13 is maximum. The difference in current density between the maximum area and the small plating area can be reduced, and the difference in plating thickness between the leading end of the strip frame 8 and the rear end of the strip frame 18 and other portions can be reduced. You can

Further, when trying to obtain the same plating thickness as in the conventional apparatus, the current of each rectifier can be lowered if other conditions such as the feed rate and the concentration of the plating solution are the same. The current that flows when the frame 18 is charged and when the strip-shaped frame 18 is discharged becomes low, and the current that flows when the plating area is extremely small becomes low, so that it is possible to prevent the current density from becoming extremely high, and prevent burn defects. be able to.

[0034]

EXAMPLES Examples of using the present invention in a step of electrolytically plating palladium on the entire surface of a lead frame in a method for manufacturing a lead frame used for a semiconductor device will be described below.
A detailed description will be given with reference to the drawings.

First, a lead frame having a predetermined shape is formed by press working or etching, and palladium is plated on the entire surface of the lead frame by a plating process of continuously plating while transporting to complete the lead frame.

As shown in FIG. 5, the plating apparatus used in the plating process of the present embodiment has a first rectifier 21 of the same current amount,
The second rectifier 22 and the third rectifier 23 are provided as independent power supply units, the frame inlet of the plating tank 24 is provided with the first cathode 25 to which the current is supplied from the first rectifier 21, and the first plating is performed. A second cathode 27 is provided between the frame outlet of the bath 24 and the frame inlet of the second plating bath 26, and the third cathode 2 is provided at the frame outlet of the second plating bath 26.
8 is provided, and the anode 29 in each plating tank and the anode of each rectifier are connected in parallel.

Then, in the present embodiment, the lead frame 30 is conveyed by the feed roll 31, and the first cathode 2
5, the second cathode 27 and the third cathode 28 are sequentially contacted, and the plating is continuously performed while being transported in each plating tank.

Next, in the plating method of this embodiment, first, as shown in FIG.
0 is conveyed, comes into contact with the first cathode 25, and the tip of the lead frame 30 is put into the first plating tank 24.

At this time, the lead frame 30 contacts only the first cathode 25, and the current is supplied only from the first rectifier 21.

Next, as shown in FIG. 6, the lead frame 3
0 is further conveyed, comes into contact with the second cathode 27, and the leading end of the lead frame 30 is put into the second plating tank 26.

At this time, the lead frame 30 contacts the first cathode 25 and the second cathode 27, and the current is supplied from the first rectifier 21 and the second rectifier 22.

Next, as shown in FIG. 7, the lead frame 30
Is further conveyed, comes into contact with the third cathode 28, and penetrates the second plating tank 26.

At this time, the lead frame 30 contacts the first cathode 25, the second cathode 27 and the third cathode 28, and the first frame 25
Current is supplied from the rectifier 21, the second rectifier 22, and the third rectifier 23.

Next, as shown in FIG. 8, the lead frame 3
0 is further transported, and the rear end of the lead frame 30 is the first
It is put into the plating tank 24.

At this time, the lead frame 30 comes into contact with the second cathode 27 and the third cathode 28, and current is supplied from the second rectifier 22 and the third rectifier 23.

Next, as shown in FIG. 9, the lead frame 3
0 is further conveyed, and the rear end of the lead frame 30 is in the second position.
It is put into the plating tank 26.

At this time, the lead frame 30 contacts only the third cathode 28, and the current is supplied only from the third rectifier 23.

Next, the lead frame 30 is further conveyed, the rear end of the lead frame 30 is discharged from the second plating tank 26, and the plating is completed.

According to the above embodiments, the lead frame 3
When the front end is in the first plating tank 24 and the rear end of the lead frame 30 is in the second plating tank 26, that is, when the plating area is small, the lead frame 30 is 1
Only the two cathodes are in contact and the current is supplied only from one rectifier, but the frame is the first plating tank 24 and the second plating tank.
When passing through the plating tank 26, that is, when the plating area is maximum, current is supplied from the three rectifiers.

Therefore, the first rectifier 21 and the second rectifier 22
And the amount of current output from the third rectifier 23 is equal, when the plating area is small, only 1/3 times the current is supplied as compared to when the plating area is maximum,
The difference between the current density when the plating area is small and the current density when the plating area is maximum can be further reduced,
It is possible to further reduce the difference in plating thickness between the leading end portion of the lead frame 30 and the trailing end portion of the lead frame 30 and other portions.

Further, when trying to obtain the same plating thickness as in the conventional example, if the other conditions such as the feed rate and the concentration of the plating solution are the same, the current amount of each rectifier is further increased than the current amount of the rectifier of the conventional example. Since the current can be made smaller, the current flowing when the lead frame 30 is charged and when the lead frame 30 is discharged is further reduced, so that the current flowing when the plating area is extremely small is further reduced and the current density is prevented from becoming extremely high. As a result, the effect of preventing burn defects can be enhanced.

If a plurality of plating baths are used as in this embodiment, the length of each plating bath in the transport direction can be shortened when the feed rate, the plating solution concentration, and other conditions are the same. When the plating surface is small, the area to be plated can be reduced, and the range in the transport direction where the plating thickness is different can be reduced.

In the present embodiment, the three cathodes supplied with electric power from the rectifiers independent of the two plating baths were used. However, if the number of each cathode is further increased, the length of each plating bath in the transport direction is shortened. Therefore, it is possible to further reduce the range in which the plating thickness is different.

Further, if the number of plating baths through which the frame penetrates at once and the number of independent cathodes that come into contact with each other in the frame input portion and the frame discharge portion of the plating bath are increased, the flow into the frame when the plating area is small. Since the current can be made smaller than the current flowing through the frame when the plating area is maximum, the difference in current density can be further reduced and the difference in plating thickness can be further reduced.

Further, in the explanatory view of this embodiment, the distance between the plating tanks is wide, but this is for the purpose of facilitating the explanation, and the distance is actually extremely short.
The shorter the size, the smaller the device, and the more plating tanks that can penetrate at one time.

In addition, in this embodiment, one space is provided between each plating tank.
Although two cathodes are arranged, if the distance between the plating tanks is long, two cathodes may be provided between the plating tanks, and each cathode may be installed near the frame inlet and the frame outlet.

[0057]

According to the method of the present invention in which plating is performed a plurality of times, the length of each plating tank in the feed direction can be shortened, and when the frame end is in the plating area of the plating tank, that is, plating is performed. When the area is small, the length in the feeding direction to be plated becomes short, so that the current density can be made different due to the difference in the plating area, and the range where the difference in the plating thickness can be made can be shortened.

According to the plating method in which the length of the plating area of the plating device in the transport direction is shorter than the length of the unnecessary portions of the front end and the rear end of the frame in the transport direction, there is a difference in the plating thickness. Since it is not the final product, it does not affect the product.

Further, even if the plating area of the plating tank is made small, the required plating thickness can be obtained without changing the transfer speed without increasing the current, due to the structure of performing plating in a plurality of plating steps. Therefore, problems such as defective coloring do not occur.

Further, when the plating area in the plating tank is small, the current density when the plating area is large and when the plating area is small is set by the plating method in which a lower current is passed than when the plating area in the plating tank is maximum. Can be reduced, and the difference in plating thickness between the frame front end and the frame rear end and other portions can be reduced.

Further, in the vicinity of the frame inlet and the frame outlet of the plating tank, the cathode is supplied with electric power from an independent power supply unit and the frame is brought into contact with each other to cause an electric current to flow from the cathode to the frame. When the frame area of is small, it contacts only one of the cathodes, and power is not supplied to the plating tank from the power supply unit that supplies power to the cathode that is not in contact with the frame, so the current density can be reduced with a simple configuration. The difference can be reduced, and the difference in plating thickness due to the difference in current density can be reduced.

Further, since the current amount of each power supply unit can be made small, the current flowing when the plating area is extremely small can be made small and the current density can be prevented from being remarkably increased. Can be prevented.

If a plurality of plating tanks provided with cathodes to which power is respectively supplied from independent power supply units are provided near the frame inlet and the frame outlet, the length of each plating tank in the transport direction can be increased. Since it can be shortened, it is possible to reduce the range in which the difference in plating thickness appears.

When the frame penetrates a plurality of plating tanks, the cathodes of the frame inlet and the frame outlet of each plating tank, each of which is supplied with power from a different power supply unit, supply current to the frame. The current flowing structure allows the current flowing in the frame when the plating area is small to be smaller than the current flowing in the frame when the plating area is maximum, so that the difference in current density can be further reduced. The effect of reducing the difference in plating thickness can be further enhanced.

[Brief description of drawings]

FIG. 1 is a diagram showing a plating apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a plating apparatus and a plating process according to an embodiment of the present invention.

FIG. 3 is a diagram showing a plating process according to an embodiment of the present invention.

FIG. 4 is a diagram showing a plating process according to an embodiment of the present invention.

FIG. 5 is a diagram showing a plating apparatus and a plating process according to an embodiment of the present invention.

FIG. 6 is a diagram showing a plating process according to an embodiment of the present invention.

FIG. 7 is a diagram showing a plating process according to an embodiment of the present invention.

FIG. 8 is a diagram showing a plating process according to an embodiment of the present invention.

FIG. 9 is a diagram showing a plating process according to an embodiment of the present invention.

FIG. 10 is a diagram showing a conventional plating apparatus.

[Explanation of symbols]

1 plating tank 2 frames 3 unnecessary parts 11 First rectifier 12 Second rectifier 13 plating tank 14 First cathode 15 Second cathode 16 Anode 17 Anode 18 frames 19 Feed roll 21 First Rectifier 22 Second rectifier 23 Third Rectifier 24 1st plating tank 25 First cathode 26 Second plating tank 27 Second cathode 28 Third cathode 29 Anode 30 lead frame 31 Feed roll 40 anode 41 plating tank 42 frames 43 Power supply unit 44 cathode

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP 63-103095 (JP, A) JP 63-11693 (JP, A) JP 10-226899 (JP, A) JP 10- 226897 (JP, A) JP-A-1-287299 (JP, A) JP-A-1-172590 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C25D 7/00 C25D 7 / 06 C25D 7/12 H01L 23/50

Claims (7)

(57) [Claims] 1. A plating method for continuously plating a conveyed strip-shaped frame using a plurality of plating tanks, wherein a strip frame inlet and a strip frame outlet on the outside of the plating tank are different from each other. An electrode connected to a power supply unit is provided, and plating is performed by supplying power from one power supply unit via the electrode to the strip-shaped frame of the plating tank in which the leading end or the rear end of the strip-shaped frame exists. And performing plating by supplying power from a plurality of power supply units to the strip-shaped frame of the plating tank in which strip-shaped frames other than the front end portion and the rear end portion are present via the electrodes. And the plating method. 2. The strip frame has an unnecessary portion on at least one of the front end portion and the rear end portion, and the plating bath has a length in the carrying direction of the strip frame shorter than the unnecessary portion. The plating method according to claim 1, wherein: 3. A plating device for continuously plating a strip-shaped frame using a plurality of plating baths while transporting the strip-shaped frame, wherein a strip frame inlet near the strip frame and a strip frame outlet outside the plating bath. A plating apparatus comprising: a plurality of cathodes provided in the vicinity and connected to different power supply units, and an anode provided in the plating tank and connected to the plurality of power supply units. 4. The plating apparatus according to claim 3, wherein the anode is connected in parallel with a plurality of the power supply units. 5. The plating tank in which the front end or the rear end of the strip-shaped frame is present performs plating by supplying power to the strip-shaped frame from one power supply unit, The plating apparatus according to claim 3 or 4, wherein the plating tank in which the strip-shaped frame other than the end portion is present performs plating by supplying power to the strip-shaped frame from a plurality of power supply units. 6. A method of manufacturing a lead frame in which a base material of a lead frame to be conveyed is continuously plated by using a plurality of plating tanks, wherein a strip frame inlet and a strip frame outlet outside the plating tank are provided. Electrodes are provided in the vicinity, each of which is connected to a different power supply unit, and power is supplied from one power supply unit to the base material of the plating tank in which the front end portion or the rear end portion of the base material exists through the electrode. Plating is performed, and the plating is performed by supplying power from a plurality of power supply units to the base material of the plating tank having the base material other than the front end portion and the rear end portion through the electrodes. And a method for manufacturing a lead frame. 7. The method of manufacturing a lead frame according to claim 6, wherein the plating is palladium plating.