JPH0313590A - Partial plating method - Google Patents

Abstract

PURPOSE:To excellently plate the minute spot of a material at high speed by opposing the exposed tip of an acicular electrode having an insulating sheath to the lower surface of the material close to the lower surface and injecting a plating soln. onto the spot to be plated from the nozzle. CONSTITUTION:A plate 1 to be plated such as an IC lead frame is held through a receiving member 2 having an opening 31 and a mask 2 having an opening 21 with a specified region 13 exposed to the lower surface. Meanwhile, plural acicular electrodes 5 are arranged in the nozzle 4 through a mounting member 51. The electrode 5 is covered with the insulating sheath 53, and only the tip of a conductor 52 is exposed and opposed to the spot 14 of the plate 1 to be plated close to the spot. The plating soln. 41 is injected toward the region 13 from the injection port 42 of the nozzle 4, and the conductor 52 is dipped in the jet. Under such conditions, plating is carried out with the plate 1 as a cathode and the conductor as an anode. The plural minute spots on the region 13 of the plate 1 are excellently plated at high speed.

Description

[Detailed Description of the Invention] [Summary] Relating to a method for manufacturing lead frames of electronic components, etc. - Particularly regarding partial plating methods such as gold plating, the present invention relates to a method for manufacturing lead frames of electronic components, etc., in which a good portion is applied to a plurality of minute spots on an object to be plated at high speed. The purpose of this method is to apply minute spot plating to multiple locations within a predetermined area of an object to be plated. A plurality of needle-shaped electrodes provided in the nozzle are arranged facing each other near the spot plating area of the object to be plated, and the conductor is plated. The plating solution is injected from the nozzle toward the predetermined region while being immersed in a jet of solution.

[Industrial application field]

The present invention relates to a method of manufacturing a lead frame of an electronic component, and more particularly to a method of performing partial plating at a high speed on a plurality of minute portions within a predetermined area of an object to be plated.

In lead frames of electronic components and contacts of connectors, precious metal plating such as gold is applied to the parts where lead wires are bonded and the parts used as contacts, but the area that requires this plating is approximately the same as that of the entire object to be plated. Since it is minute compared to the area, it is possible to apply partial plating to a predetermined thickness only on this portion, which is extremely effective in reducing costs.

[Conventional technology]

FIG. 4 is a diagram showing an IC lead frame to which the present invention is directed.

An object to be plated 1 such as an IC lead frame has an island part 11 in the center on which a semiconductor chip is mounted, and a plurality of lead pins 12 extending radially outward around the island part 11. , gold plating is applied to a predetermined region 13 including the center-side tip of the lead pin 12. The conventional partial plating method for selectively plating a predetermined area is as shown in FIG. The plating mask 2 is placed on the support member 3 having the window portion 31, and the object 1 to be plated is placed 5i12X thereon so that the predetermined area 13 is exposed to the lower side through the opening 21 of the plating mask. Then, the object 1 to be plated is pressed from above with a pressing member (not shown) to bring it into close contact with the plating mask 2, and the plating solution 22 is sprayed upward onto the lower surface of the object 1 from a nozzle 21 made of a platinum layer or the like which also serves as a plating anode. By doing so, partial plating was applied only to the predetermined area 13.

According to this method, not only the tip of the lead pin 12 but also the island portion 11 is plated with the same thickness.

However, recently, it has become possible to mount semiconductor chips using conductive adhesive instead of using glue bonding, so there is no need for gold plating on the island part.
Gold plating is required, and all that is required is a minute portion of the tip of the lead pin where wire bonding for connection to the semiconductor chip is made, and the diameter of the lead pin tip at the desired position is 1+
A method of applying gold plating only to minute spots of ni or less is attracting attention.

As a plating method for this purpose, a plating solution is sprayed from a common nozzle using a plating mask with a plurality of minute openings only in the portion corresponding to the desired plating portion of the tip of each glued pin. , a method has been proposed in which spot-like minute plating is performed only on a desired portion of the tip of a lead pin. (For example, see Japanese Patent Application Laid-Open No. 60-39193)
FIG. 6 is an enlarged cross-sectional view of the main part of the plating mask in this case. On the upper surface of the plating mask 2, recesses 22 for accommodating the widths of the individual lead pins 12 are formed corresponding to the arrangement of the lead pins. At the position corresponding to the desired part,
A minute opening 23 approximately equal to the desired spot plating diameter passes through the top and bottom. Then, while the object to be plated is pressed against the recess 22 of the mask 2 by the holding member 15, the plating solution 41 is injected from a common nozzle to a desired portion of the lead pin 12 through the minute opening 23 to perform spot plating.

[Problem to be solved by the invention]

In this case, the desired plating area is extremely small, about less than IM, and the area of the opening of the mask is correspondingly small, which is smaller than the thickness of the mask, so the plating solution is injected into a deep small hole with the upper end closed. As a result, the plating solution sprayed from the nozzle stagnates inside the opening, making it difficult to recycle the plating solution.

As a result, the metabolism of the plating solution becomes inactive, and the metal ion concentration decreases slowly in the stagnant plating solution, making it impossible to increase the current density, resulting in problems such as low plating speed and poor mass productivity. Ta.

That is, if the opening is made small by mask plating, the supply of fresh plating solution containing metal ions at a predetermined concentration becomes insufficient, making it impossible to perform good plating at high speed.

The present invention was created in view of the above problems, and an object of the present invention is to provide a partial plating method that performs good plating at high speed on a plurality of minute spots on an object to be plated.

[Means to solve the problem]

The above problem lies in the method of applying minute spot plating to multiple locations within a predetermined area of the object to be plated, in which the predetermined area of the object to be plated is exposed to the lower surface through an opening in a plating mask, and is not covered with an insulating coating. A plurality of needle-shaped electrodes provided in the nozzle are arranged facing each other in close proximity to the spot plating area of the wave-plated object, and the conductor is exposed to a jet of plating solution. This problem is solved by the partial plating method of the present invention, characterized in that the plating solution is sprayed from the nozzle toward the predetermined region while immersing it in water.

[Effect]

An electric field concentration occurs between the tip of the needle-shaped electrode and the surface of the object to be plated, and the plating current flows in a concentrated manner in the part of the object to be plated that faces the electrodes, so that the plating area can be limited to a spot. The plating solution is then sprayed at high speed onto the object to be plated in large quantities through a relatively large-area mask opening that masks a predetermined area, so metal ions are sufficiently replenished, increasing the plating speed. can do.

〔Example〕

The present invention will be described in detail below with reference to the accompanying drawings.

Fig. 1 is a schematic cross-sectional view of the main part of an apparatus for carrying out the method of the present invention, Fig. 2 is a cross-sectional view showing details of the needle-shaped electrode, and Fig. 3 is the concept of continuous partial plating using the needle-shaped electrode. It is a diagram. Note that the same reference numerals represent the same objects throughout the plan.

First, a method of implementing the present invention will be explained using the apparatus configuration shown in FIG.

In the figure, 1 is a plate-shaped object to be plated such as an IC lead frame, 2 is a plating mask, 3 is a support member, 4 is a nozzle,
5 is a plurality of needle electrodes. The mask 2 is made of an elastic member such as silicone rubber, and has a relatively wide predetermined area 13 that includes all of the plurality of spot plating areas 14 on the lower surface of the object to be plated 1.
An opening 21 is formed in a portion corresponding to , and a receiver in which an opening 31 is similarly formed is placed on the upper surface of the member 3. The top surface of the object 1 to be plated is pressed by a pressing means (not shown), and it comes into close contact with the plating mask 2, and through the opening 21,
It is set so as to be exposed below the predetermined area 13.

The nozzle 4 is a pipe-shaped member made of an insulating material, and has a spout 42 that is slightly smaller than the opening 21 of the plating mask open at the upper end, and is provided below the opening 21 of the plating mask, and is connected to a liquid feeding means (not shown). Plating solution 41 that has been pressure-fed by
A predetermined area 13 of the object to be plated 1 through the mask opening 21
inject at high speed.

Reference numeral 5 designates a plurality of needle-like electrodes, the tips of which protrude from the nozzle nozzle 42 and are installed inside the nozzle 4. Electrode attachments made of an insulating material are erected on a member 51.

The needle electrode 5 is a conductor 5 made of a corrosion-resistant metal such as platinum wire.
The conductor 52 is surrounded by an insulating coating 53 so that only the upper end of the conductor 2 is exposed, and the tip of the exposed conductor 52 is placed so as to approach and face the spot plating compatible area 14 of the object to be plated. The lower end of the conductor 52 is connected to a power supply member 54 buried inside the electrode mounting member 51 .

Figure 2 shows an example of a needle-shaped electrode, and (a) in the figure uses a platinum rod with a thin tip as the conductor 52, and a chemical-resistant insulating coating 53 is applied around the area other than the tip. in,
It has a structure in which the electric conductor itself supports the force of standing up. Also figure (
In b), a thin platinum wire is passed through an insulating coating 52 made of hollow conical resin as a conductor 52, and tI! In Figure 0 (c), where the A edge member is a structural member, an insulating coating 53 is applied to the conductor 54 as in Figure (a), but
The conductor of the platinum layer has a hollow pipe shape, and an optical fiber 55 is passed through the center of the pipe, so that a laser beam 55 can be irradiated from the tip of the optical fiber 55. By using this electrode, plating can be performed while irradiating the desired part of the object to be plated with laser light, and the laser light activates the electrolytic action, further improving the metal plating deposition rate. .

In the apparatus with the above configuration, the + side of the plating power source is connected to the needle electrode 5,
When the - side is connected to the object 1 to be plated and the plating solution 41 is jetted from the nozzle 4, the plating solution 41 is sprayed onto a relatively wide predetermined area 13 of the object to be plated through the wide opening 21 of the plating mask 2. The plating solution 41 does not fall around the jet flow and stagnate inside the opening 21 of the plating mask due to reflux.

Since only the tip of the conductor 52 of the needle electrode exposed in the liquid near the surface of the object 1 to be plated serves as an anode, the plating current between the object 1 to be plated and the object 1 acting as a cathode is transmitted to the tip of the electrode. A plating film 15 (indicated by a dotted line) is obtained which is thick only in this part and thin in the other parts. In this case, the entire predetermined area other than the desired spot area is also immersed in the jet of plating solution, but since no electric field is concentrated by the electrodes, almost no plating current flows and only a thin plating film is deposited.

Note that using the needle-shaped electrode described above, it is also possible to continuously perform spot plating in minute areas at a predetermined pitch on a continuous strip-shaped object to be plated. FIG. 3 schematically shows this example, in which needle electrodes 5 (described above in FIG. 2) are arranged radially around the rotating electrode installation disk 61 so that the tips thereof are at the predetermined pitch P. The needle electrode 5 is placed in the plating solution so that the tip of the needle electrode 5 approaches the desired spot plating position (pitch P) of the strip-shaped object 62 to be plated. Then, a shielding plate 63 made of an insulating material is used to shield the plating current so that most of the plating current flows between the needle-like electrode that is close to the object to be plated among the plurality of needle-like electrodes and the object to be plated. Then, the conveyance sprocket 64 and the electrode installation disk 61 are rotated in synchronism so that the tip speed V of the needle-like electrode 5 is equal to the conveyance speed V of the object to be plated 62, so that the connected object to be plated 62 Spot-like partial plating 65 can be performed at a predetermined pitch P.

〔Effect of the invention〕

As explained above, according to the method of the present invention, the plating current is concentrated on the microscopic surface facing the needle electrode, and the plating area is limited to a spot, and the plating solution is supplied to the entire predetermined area at high speed. Therefore, even if the current density is increased, a good plating film can be obtained, and high-speed spot plating can be realized.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of the main parts of an apparatus for carrying out the method of the present invention, FIG. 2 is a cross-sectional view showing details of a needle-like electrode, and FIG. A conceptual diagram of continuous partial plating, Fig. 4 is a diagram of the object to be plated which is the target of the present invention, Fig. 5 is a diagram showing a conventional mask type partial plating method, and Fig. 6 is a mask used for spot plating. This is a cross-sectional view of . In the figure, 1.-Object to be plated (ICIJ-de frame), 12-
・Lead pin, 13--Predetermined area, 15--
Plating film, 2...Plating mask, 21
・-opening, 3--receiver is member, 4--nozzle, 41--plating solution, 5--acicular electrode, 51--electrode mounting member, 52--conductor,
53.--insulating coating. 3) Honzenshuo n direction activity Σ truth town suu △men exhibition Wf) f1q term 戎 dark surface diagram Figure 1 (a) Circle 41 rod shape (b) Piercing hole (Ri 9)? 4 + 4 large nitrogen jf) details (field and T cross section m Fig. 4 + north -f,, ← se? Used 1 i excess damage P Niigo Sun Moon Bore 4 skin plating with 4 small holes Diagram

Claims (1)

[Claims] A method of applying minute spot plating to multiple locations within a predetermined area (13) of an object (1) to be plated, the method comprising:
) in the opening (2) of the plating mask (2).
A plurality of needle-shaped electrodes (52) provided in the nozzle (4) are exposed on the lower surface through the nozzle (4) and covered with an insulating coating (53), with the conductor (52) exposed only at the tip. ) are placed close to and facing the spot plating area (14) of the object to be plated (1), and the conductor (51) is placed in a plating solution (41).
) A partial plating method characterized in that a plating solution (41) is injected from the nozzle (4) toward the predetermined region (13) while being immersed in a jet stream.