JP2007311428A - Plating method, and mask plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To plate a print pattern 221 formed on a substrate 210 with a cream solder 250. <P>SOLUTION: The plating method is used to plate an annular plating area to be solder-plated in a print pattern 221 formed on the surface of a substrate 210 with a cream solder. The method includes a masking step to overlay on the substrate 210 a mask plate 240 that is provided with an outer mask pattern for masking the outside of the plating area, an inner mask pattern for masking the inside of the plating area, and a bridge part 247 connecting the outer mask pattern and the inner mask pattern together; a filling step to fill window parts 241 and 243 formed between the outer mask pattern and the inner mask pattern, in the mask plate 240 with the cream solder 250; and a melting step to melt the cream solder 250 by rising the temperature of the substrate 210 wherein the cream solder 250 is applied. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a plating method and a mask plate. More specifically, the present invention relates to a method for plating an annular printed pattern formed on a printed board with cream solder, and a mask plate used therefor.

  A printed circuit board that forms a device's electrical circuit by mounting multiple elements is a substrate formed by impregnating a base material such as paper or glass fiber cloth with a non-conductive resin such as phenol resin, epoxy resin, or fluorine resin. And a printed pattern formed on the surface thereof by a conductive material such as copper foil. Further, a printed circuit board supplied to form a specific circuit is shipped in a state where a region other than a region where components are mounted by soldering is covered with a resin such as a solder resist. This prevents a short circuit of the print pattern due to the solder and prevents oxidation of the metal foil forming the print pattern. Even in a region where no solder resist is applied for the purpose of mounting components, the surface of the printed pattern is often covered with solder. This solder plating prevents the copper foil exposed in the atmosphere from being deteriorated by oxidation or the like.

  The solder plating as described above is formed of a specific solder material called a solder leveler. Since this type of solder material has good wettability with respect to the printed pattern in the molten state and high fluidity, all of the copper foil exposed on the printed board could be plated with solder. However, since the use of lead-containing solder has been restricted, it has become impossible to obtain a solder with high performance as a leveler.

  Therefore, a material called cream solder is used instead of the solder leveler. Cream solder is a paste obtained by kneading a powdered solder material with a flux. When applied to a printed circuit board and heated, the flux component volatilizes to form a solder layer. However, the performance as a leveler does not reach that of a solder leveler, and the melting temperature is high when lead is not contained.

  Furthermore, since cream solder contains a large amount of volatile components, in order to form a solder plating layer having a desired thickness, it must be applied to the printed circuit board considerably thickly. For this reason, it apply | coats using the jig | tool called a mask board etc. which were formed with the metal etc. That is, the mask plate is a plate that is the same as or larger than the substrate, and a through hole is formed in a region where the cream solder is to be applied. With such a mask plate overlaid on the substrate, a sufficient amount of cream solder is placed on the mask plate, and the squeegee is used to push the cream solder into the through hole and scrape excess solder that has not been filled into the hole. take. Thus, cream solder is applied to a desired area on the surface of the printed circuit board. Next, after removing the mask plate, the printed circuit board is heated to melt the cream solder and develop it on the printed pattern. Thus, the printed pattern on the substrate is plated with solder.

JP 2001-251029 A

  By the way, there may be a region where the printed pattern is exposed from the solder resist on the printed circuit board even if the component is not mounted by soldering. For example, as described in Patent Document 1, this is an annular region formed around a screw hole through which a screw for fixing the printed circuit board itself to a chassis, a case or the like is inserted. Such a printed pattern is used to electrically couple the printed pattern on the substrate to the chassis via screws.

  However, since the annular pattern formed around the screw hole as described above has a screw hole formed inside thereof, solder plating with cream solder cannot be performed by the method using the mask plate. . That is, if cream solder is applied in a state where the periphery of the annular pattern is masked, a large amount of cream solder enters the screw holes. Therefore, not only a good plating layer is not formed, but the solder may block a part of the screw hole or may flow to the back surface. Therefore, when solder plating is performed using cream solder, the solder printing of the annular printed pattern is omitted.

  However, as described above, in the state where the copper foil of the printed pattern is exposed to the atmosphere, even after the screw is attached, the oxidation proceeds from the slightly exposed copper foil, and between the screw and the printed pattern. A continuity failure may occur. In addition, since the thin copper foil forming the printed pattern has almost no elasticity, when the substrate material is thinned due to a change in diameter, a gap is generated under the screw, and the oxidation of the copper foil further proceeds. There was a bug. In view of this, a technique has been sought for solder plating that uses a cream solder and that also has an annular printed pattern including screw holes.

  Therefore, in order to solve the above problems, as a first embodiment of the present invention, there is provided a plating method for plating an annular plating region to be solder-plated in a printed pattern formed on a surface of a substrate by a conductor with cream solder. A mask procedure for superimposing an outer mask pattern for masking the outer side of the plating region, an inner mask pattern for masking the inner side of the plating region, and a mask plate having a bridge part for mutually coupling the outer mask pattern and the inner mask pattern on the substrate And a filling procedure for filling the window portion formed between the outer mask pattern and the inner mask pattern with cream solder on the mask plate, and a melting procedure for melting the cream solder by heating the substrate loaded with the cream solder. A plating method is provided. As a result, solder plating can be performed using cream solder even on the annular print pattern formed on the substrate.

  According to one embodiment, in the plating method, the width of the bridge portion is substantially equal to the thickness of the mask plate. As a result, an appropriate amount of cream solder can be applied onto the printed pattern so that the molten solder spreads over and over in the region masked by the bridge portion when the mask plate is placed.

  According to another embodiment, in the plating method, the inner mask pattern masks the opening of the through hole formed through the substrate. Thereby, it is prevented that cream solder is filled in through holes such as screw holes formed in the substrate, and solder printing can be performed on the annular printed pattern using cream solder.

  Further, as a second embodiment of the present invention, the printed pattern formed on the surface of the substrate by the conductor has a window corresponding to the plating area to be solder-plated, and the solder is applied to the window in a state of being superimposed on the substrate. This is a mask plate used when cream solder is applied to the plating area by filling, and is arranged inside the plating area and has a width substantially equal to the thickness of the mask plate and connects different mask patterns to each other. A mask plate having a bridge portion is provided. As a result, solder plating can be performed on the annular printed pattern on the substrate using cream solder. In addition, when the mask plate is placed, an appropriate amount of cream solder can be applied on the printed pattern so that the molten solder spreads over and over in the area masked by the bridge portion.

  Also, the above summary of the invention does not enumerate all the necessary features of the present invention, and sub-combinations of these feature groups can also be the invention.

  Hereinafter, the present invention will be described through embodiments of the invention. However, the following embodiments do not limit the invention according to the scope of claims, and all combinations of features described in the embodiments are included. It is not necessarily essential for the solution of the invention.

  FIG. 1 is a partial perspective view showing a state 110 before processing of a substrate 210 loaded with a printed pattern 221 to be solder plated. As shown in the figure, a plurality of printed patterns 221, 222, 224, 226, and 228 formed of a copper foil 220 are disposed on a substrate 210 formed of an insulating material. Of these print patterns 221, 222, 224, 226, 228, the print patterns 221, 222, 226 are combined to form a large pattern. A screw hole 212 that penetrates the substrate 210 is formed inside the large pattern formed by the print patterns 221, 222, and 226.

  FIG. 2 is a partial perspective view showing a state 120 in which the surface of the substrate 210 shown in FIG. The solder resist 230 is a material that itself has insulating properties and low air permeability, and is formed on the surface of the substrate 210 by printing. In the solder resist 230, a part of the surface of the print patterns 221, 222, 224, 226, 228 formed by the copper foil 220 and the print patterns 221, 222, 224, 226, 228 are not formed on the surface of the substrate 210. Covering the area.

  However, windows 221, 222, 224, 226, and 228 are formed in regions where electrical connections are formed, and a part of the print patterns 221, 222, 224, 226, and 228 formed by the copper foil 220 is exposed. is doing. Of these print patterns 221, 222, 224, 226, and 228, the small and square print patterns 222, 224, 226, and 228 serve as regions for soldering connection terminals of elements to be described later. In addition, the circular and large print pattern 221 is an area where the head of the screw 266 inserted through the screw hole 212 contacts to fix the substrate 210. The copper foil 220 exposed inside these window portions 231, 232, 234, 236, and 238 becomes a target of solder plating.

  FIG. 3 is a partial perspective view showing a state 130 immediately before the mask plate 240 is overlaid on the substrate 210 shown in FIG. As shown in the figure, the mask plate 240 has window portions 242, 244, 246 and 248 having shapes corresponding to the copper foil 220 exposed inside the window portions 232, 234, 236 and 238 of the solder resist 230. Further, window portions 241 and 243 corresponding to the printed pattern 221 around the screw hole 212 of the substrate 210 are also provided.

  Further, the mask plate 240 has a circular screw hole sealing portion 245 that seals the screw holes 212 of the substrate 210 inside the window portions 241 and 243. In the mask plate 240, the outer peripheral areas of the window portions 241 and 243 cover the surface of the solder resist 230 as an outer mask pattern. Further, the screw hole sealing portion 245 covers the screw hole 212 from above as an inner mask pattern. Accordingly, substantially annular window portions 241 and 243 are formed between these mask patterns. Further, the screw hole sealing portion 245 is coupled to the inner surfaces of the window portions 241 and 243 by a pair of bridge portions 247. Therefore, the screw hole sealing portion 245 can be handled integrally with other portions of the mask plate 240.

  As a material of the mask plate 240, any plate material can be used as long as it is a thin plate with little deformation. However, in view of durability for reuse, a stainless steel plate can be preferably exemplified. Further, the window portions 241, 242, 243, 244, 246, 248 can be formed by laser processing.

  FIG. 4 is a partial perspective view showing a state 140 in which the mask plate 240 is superimposed on the substrate 210. As shown in the figure, the mask plate 240 is in close contact with the substrate 210 from above. The board 210 is slightly uneven due to the copper foil 220 and the solder resist 230 loaded on the board 210. However, since the cream solder 250 described later has a high viscosity, it can be considered that the cream solder 250 is substantially in close contact.

  Note that the small printed patterns 222, 224, 226, and 228 are exposed over substantially the front surface inside the window portions 242, 244, 246, and 248 having the same shape. On the other hand, a part of the circular printed pattern 221 formed around the screw hole 212 is covered with the bridge portion 247 of the mask plate 240. However, as will be described later, the area covered with the bridge portion 247 is also finally subjected to solder plating.

  FIG. 5 is a partial perspective view showing a state 150 in which the window portions 241, 242, 244, 246 and 248 of the mask plate 240 are filled with cream solder 250. As a work procedure, a sufficient amount of cream solder 250 is placed on the mask plate 240, and then the surface of the mask plate 240 is rubbed with a tool such as a squeegee, so that the mask plate 240 is formed as shown in FIG. The inside of the windows 241, 242, 244, 246 and 248 can be filled with cream solder 250. Excess cream solder 250 is scraped off from the surface of mask plate 240.

  FIG. 6 is a partial perspective view showing a state 160 in which the mask plate 240 is removed from the substrate 210 shown in FIG. As shown in the figure, when the mask plate 240 is removed, the cream solder 250 rises inside the windows 231, 232, 234, 236, and 238 of the solder resist 230. However, the cream solder 250 in the region corresponding to the bridge portion 247 of the mask plate 240 is missing around the screw hole 212.

  FIG. 7 is a partial cross-sectional view showing the shape of the cream solder 250 around the screw hole 212 in the cross section including the arrow S shown in FIG. 6 in the state 160 shown in FIG. As shown in the figure, the cream solder 250 is not placed on the surface of the copper foil 220 in the region where the bridge portion 247 of the mask plate 240 was present. Therefore, in this state 160, a part of the surface of the copper foil 220 is exposed.

  FIG. 8 is a partial perspective view showing a state 170 in which the substrate 210 shown in FIG. As shown in the figure, the cream solder 250 is once melted inside the windows 231, 232, 234, 236, and 238 by being heated in the reflow process to form a solder plating layer 252. Here, also inside the window portion 231, the solder plating layer 252 is formed over the front surface.

  FIG. 9 is a partial cross-sectional view showing the shape of the solder plating layer 252 formed around the screw hole 212 in the state 170 shown in FIG. As shown in the figure, the solder plating layer 252 is also formed in the region where the copper foil 220 is exposed in the state 160 shown in FIG. That is, the melted solder paste 250 spreads on the surface of the copper foil 220 having high wettability with respect to the melted cream solder 250 and covers a part of the copper foil 220 exposed for the bridge portion 247. Is formed.

  However, if the exposed region of the copper foil 220 formed by the bridge portion 247 is too wide in the window 231, the cream solder 250 is insufficient and a region where the solder plating layer 252 is not formed remains. Therefore, the width of the bridge portion 247 is preferably set to be approximately the thickness of the mask plate 240.

  FIG. 10 is a partial perspective view showing the state 100 of the substrate 210 covered with the solder resist 230 and the solder plating layer 252 and its application. As shown in the figure, the insides of the window portions 231, 232, 234, 236, and 238 of the solder resist 230 are all covered with a solder plating layer 252. Therefore, chips 262, 252 and the like of various elements can be satisfactorily soldered to the print patterns 222, 224, 226, 228. Also in the printed pattern 221 around the screw hole 212, the surface of the copper foil 220 is covered with the solder plating layer 252. Therefore, not only a good electrical connection between the head of the screw 266 and the printed pattern 221 is obtained, but also the oxidation of the copper foil 220 in this region can be effectively prevented.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above-described embodiment. It is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

It is a fragmentary perspective view which shows the state 110 before starting a plating process. 2 is a partial perspective view showing a state 120 in which the surface of a substrate 210 shown in FIG. 1 is partially covered with a solder resist 230. FIG. FIG. 3 is a partial perspective view showing a state 130 before a mask plate 240 is overlaid on a substrate 210 shown in FIG. 2. It is a fragmentary perspective view which shows the state 140 which accumulated the mask board 240 on the board | substrate 210. FIG. FIG. 6 is a partial perspective view showing a state 150 in which cream solder 250 is filled in window portions 241, 242, 244, 246, and 248 of a mask plate 240. FIG. 6 is a partial perspective view showing a state 160 in which a mask plate 240 is removed from the substrate 210 shown in FIG. 5. FIG. 7 is a partial cross-sectional view showing the shape of cream solder 250 around the screw hole 212 in the state 160 shown in FIG. 6. FIG. 6 is a partial perspective view showing a state 170 in which the substrate 210 shown in FIG. 5 is subjected to reflow processing. FIG. 9 is a partial cross-sectional view showing the shape of a solder plating layer 252 formed around the screw hole 212 in the state 170 shown in FIG. 8. It is the fragmentary perspective view which shows the state 100 of the board | substrate 210 coat | covered with the soldering resist 230 and the solder plating layer 252, and its use.

Explanation of symbols

  100, 110, 120, 130, 140, 150, 160, 170 state, 210 substrate, 212 screw hole, 220 copper foil, 221, 222, 224, 226, 228 print pattern, 230 solder resist, 231, 232, 234, 236, 238, 241, 242, 243, 244, 246, 248 Window, 240 Mask plate, 245 Screw hole sealing part, 247 Bridge part, 250 Cream solder, 252 Solder plating layer, 262, 264 Chip, 266 Screw

Claims (4)

A plating method for plating an annular plating region to be soldered in a printed pattern formed on the surface of a substrate by a conductor with cream solder,
A mask plate having an outer mask pattern for masking the outer side of the plating region, an inner mask pattern for masking the inner side of the plating region, and a bridge portion for mutually connecting the outer mask pattern and the inner mask pattern; A mask procedure to overlay on,
A filling procedure for filling a window formed between the outer mask pattern and the inner mask pattern with cream solder in the mask plate;
And a melting procedure for melting the cream solder by raising the temperature of the substrate loaded with the cream solder.   The plating method according to claim 1, wherein a width of the bridge portion is substantially equal to a thickness of the mask plate.   The plating method according to claim 1, wherein the inner mask pattern masks an opening of a through hole formed through the substrate.   The printed pattern formed on the surface of the substrate by the conductor has a window portion corresponding to the plating region to be solder-plated, and the cream region is creamed by filling the window portion with cream solder while being superimposed on the substrate. A mask plate for use in applying solder, the mask plate having a bridge portion disposed inside the plating region, having a width substantially equal to the thickness of the mask plate, and coupling different mask patterns to each other.

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