JP2009076727A - Printed wiring board, electronic equipment using the same, and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printed wiring board which can prevent disconnection of a wiring pattern even when lead-free solder is used and is reliable, electronic equipment using the same, and a manufacturing method thereof. <P>SOLUTION: Disclosed is the printed wiring board 1 characterized in that a land 3 provided to a through hole 2 comprises a plurality of conductive layers. As a concrete example, the plurality of conductive layers comprise a first conductive layer 31 formed at an extension portion of the wiring pattern 5 and connected to the wiring pattern 5, and a second conductive layer 32 formed on a top surface side of the first conductive layer 31 and electrically and physically connected to the first conductive layer 31 at an end on the side of the through hole 2. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a printed wiring board used for an electronic device, an electronic device using the printed wiring board, and a manufacturing method thereof.

  When circuit components are inserted and soldered into through-holes of conventional general printed wiring boards, when Sn-Pb eutectic solder is used, normal solder joints are obtained, whereas lead-free solder is used. When used, a phenomenon called so-called land peeling, in which the land rises, frequently occurs. When land peeling occurs, the wiring pattern connected to the land also rises, and the wiring pattern is easily disconnected. Thus, the disconnection of the wiring pattern due to the land peeling significantly reduces the reliability of the electronic device using the printed wiring board. As a countermeasure for preventing such land peeling, it has been proposed to prevent land peeling by covering a land with a solder resist (see, for example, Patent Document 1).

Japanese Patent No. 3686861 (first page, FIG. 1)

  In the prior art as described above, there is a problem that the solder fillet formed on the land becomes small by covering the land with the solder resist, and there is a concern that the bonding reliability of the soldered portion is lowered.

  The present invention has been made to solve the above-described problems of the prior art, and does not reduce the fillet, and even when lead-free solder is used, the wiring pattern can be prevented from being disconnected with high reliability. It is an object to provide a printed wiring board, an electronic device using the printed wiring board, and a manufacturing method thereof.

The printed wiring board according to the present invention is characterized in that a land provided in a through hole is composed of a plurality of conductive layers.
In the electronic device according to the present invention, the lead wire of the circuit component is inserted into the through hole of the printed wiring board, and connected and fixed by solder.
The method for manufacturing a printed wiring board according to the present invention includes a step of providing a through hole for forming a through hole in a base material, and a first conductor straddling the inner wall of the through hole and the surface of the base material. A step of forming, a step of selectively removing the first conductor by photolithography to form a first conductive layer and a wiring pattern constituting the land, a surface of the base material, and the first conductive layer. And a step of forming an insulating layer on the wiring pattern, a step of forming a second conductor straddling the inner wall of the through hole and the insulating layer, and the second conductor by photolithography. And a step of forming a second conductive layer that constitutes the land by selectively removing.

  In the printed wiring board of the present invention, since the land provided in the through hole is formed in the plurality of conductive layers, when the lead wire of the circuit component is inserted into the through hole and soldered with lead-free solder, Only the uppermost conductive layer constituting the layer is peeled off, and the conductive layer under the land constituting the land is maintained in connection with the wiring pattern, thereby preventing the wiring pattern from being disconnected. In addition, since it is not necessary to cover a part of the uppermost conductive layer constituting the land with the solder resist, the fillet shape is not reduced.

  In the method for manufacturing a printed wiring board of the present invention, a land including a plurality of conductive layers having a first conductive layer and a second conductive layer can be easily provided in a through hole by a combination of general processes. it can. In addition, among the plurality of conductive layers constituting the land provided in the through hole, only the uppermost second conductive layer is formed so as to be easily peeled off, thereby preventing the lower first conductive layer from being peeled off. There is an effect that a highly reliable printed wiring board in which disconnection of the pattern is prevented can be obtained.

Embodiment 1 FIG.
1 to 3 are diagrams for explaining a printed wiring board according to Embodiment 1 of the present invention, an electronic device using the printed wiring board, and a method for manufacturing the printed wiring board. FIG. 1 schematically illustrates a through-hole portion of the printed wiring board. FIG. 2 is an explanatory view showing the manufacturing method of the printed wiring board shown in FIG. 1 in the order of steps, and FIG. It is sectional drawing which shows typically the through-hole part of the electronic device connected and fixed with the solder. In FIG. 1, in a printed wiring board 1 of the present invention, a land 3 provided in a through hole 2 is formed by a plurality of conductive layers. In the first embodiment, the plurality of conductive layers constituting the land 3 are formed in an extension portion of the wiring pattern 5 provided on the substrate 4, and the first conductive layer 31 connected to the wiring pattern 5 is formed. And the second conductive layer 32 formed on the surface side of the first conductive layer 31 and electrically and physically connected to the first conductive layer 31 at the end on the through hole 2 side. It has become.

  In the first embodiment, the insulating layer 6 formed by thermally curing the solder resist is interposed between the two conductive layers of the first conductive layer 31 and the second conductive layer 32. The insulating layer 6 is integrally provided across the surface of the substrate 4 and the wiring pattern 5. A solder resist 7 is provided on the insulating layer 6 except for the land 3. A predetermined number of the lands 3 are provided at predetermined positions on the printed wiring board 1, and each of the lands 3 is formed symmetrically on the front surface (for example, the upper side in the figure) and the back surface of the substrate 4. It is formed integrally with a conductor provided on the wall surface.

  Next, a method for manufacturing the printed wiring board 1 according to the first embodiment will be described with reference to FIGS. First, a through hole 20 having a diameter of 0.9 mm is formed in a predetermined position of a base material 4 (FIG. 2A) in which a glass cloth is impregnated with an epoxy resin by a drill or the like. Electroless copper plating and electrolytic plating are performed on the inner wall of the hole 20 and the surface of the substrate 2 to form the first conductor 81 composed of the electroless copper plating layer 81a and the electrolytic plating layer 81b (FIG. 2B). . Next, the first conductor 81 is etched by coating with a patterning resist, and the first conductive layer having a diameter of 1.3 mm constituting the wiring pattern 5 and the land 3 connected by the extension of the wiring pattern 5. 31 is formed (FIG. 2C).

  Subsequently, a solder resist is printed on the surface of the substrate 4, the first conductive layer 31, and the wiring pattern 5, and thermally cured to form the insulating layer 6 (FIG. 2D). Further, electroless copper plating and electrolytic plating are performed on the inner wall of the through hole 20 and the insulating layer 6 made of solder resist to form a second conductor 82 made of the electroless copper plating layer 82a and the electrolytic plating layer 82b (see FIG. FIG. 2 (e)). Further, the second conductor 82 is etched by coating with a patterning resist to form the second conductive layer 32 having a diameter of 1.3 mm constituting the land 3 (FIG. 2F). Finally, the solder resist 7 is printed and applied, exposed, developed, and thermally cured to obtain the printed wiring board 1 according to the first embodiment of the present invention (FIG. 2 (g)).

  Further, a lead wire of a circuit component (insertion component) not shown in detail is inserted into the through hole 2 of the printed wiring board 1 obtained by the manufacturing method of the first embodiment as described above, and immersed in molten solder. The electronic device was obtained by soldering by a so-called flow soldering process. The solder composition at this time was lead-free solder (Sn-3.0Ag-0.5Cu solder), the solder melt temperature was 250 ° C., and the conveyor speed was 1.0 m / min. In addition, a standard RMA type flux was used.

  A through hole portion of a printed wiring board in the electronic device manufactured as described above is schematically shown in FIG. In the figure, a lead wire 9 of a circuit component is inserted into a through hole 2 and connected and fixed by lead-free solder 10. In a conventional printed wiring board with a single land, the portion corresponding to the vicinity of the boundary between the wiring pattern 5 indicated by the arrow A and the land 3 is peeled off and turned up, and the wiring pattern 5 is disconnected. In the first embodiment of the invention, as shown in the drawing, peeling is observed between the second conductive layer 32 and the insulating layer 6 made of solder resist, and the wiring pattern 5 and the first connected to the wiring pattern 5 are observed. The conductive layer 31 was not peeled off at all, and therefore no disconnection occurred.

  In the printed wiring board obtained by the above manufacturing method, the surface between the upper surface side of the insulating layer 6 and the second conductive layer 32 is not subjected to surface roughening by a normal chemical polishing, and the insulating layer 6 The surface roughness of 6 is 1 μm or less. This is because the adhesiveness between the second conductive layer 32 and the insulating layer 6 is intentionally lowered by not performing surface roughening, and the second conductive layer 6 is positively stripped. is there. The present invention is particularly effective when the length L (FIG. 1) from the end portion on the through hole 2 side to the outer peripheral end portion of the land 3 is 0.8 mm or less. This is because, when the length L from the end of the through hole 2 to the outer periphery of the land 3 is longer than 0.8 mm, the adhesion between the land 3 and the base material is increased, so that the land peeling does not occur in the conventional printed wiring board. On the other hand, when the thickness is 0.8 mm or less, it is easy to peel off.

  FIG. 3 obtained using lead-free solder (Sn-3.0Ag-0.5Cu solder) for the printed wiring board obtained by the manufacturing method of the first embodiment and a conventional printed wiring board as a comparative example. A temperature cycle test of −40 ° C. (30 min) ⇔ + 125 ° C. (30 min) is performed up to 500 cycles (cyc) on the electronic device substantially the same as that shown in FIG. The presence or absence of disconnection was confirmed. The results of this verification are shown in Table 1. In addition, the numerical value in the same table | surface is the number of disconnection generation / the number of evaluation wiring. In the conventional printed wiring board shown as a comparative example, the disconnection of the wiring pattern is seen at the time of the temperature cycle test 100 cyc, and the ratio thereafter increases, whereas in the printed wiring board 1 of the first embodiment, the temperature In the cycle test 500 cyc, no disconnection of the wiring pattern was observed.

  In the first embodiment, the case where a base material in which a glass cloth is impregnated with an epoxy resin is used as the base material 4 is not limited to the above, but an insulating material, for example, Any known substrate such as a substrate obtained by impregnating a paper substrate, a polyester substrate, or the like with a resin material such as an epoxy resin or a phenol resin can be used without any particular limitation. Moreover, although the case of a double-sided substrate has been described, the present invention is not limited to this, and a multilayer substrate or the like may be used. Furthermore, although the case where Sn-Ag-Cu solder was used as the lead-free solder has been described, the present invention is not limited to this including the composition. For example, Sn-Cu solder, Sn-Ag solder, Any known lead-free solder such as Sn—Zn solder and Sn—Sb solder can be used without any particular limitation.

  As described above, in the printed wiring board according to Embodiment 1 of the present invention, the land 3 provided in the through hole 2 is formed by a plurality of conductive layers, and the plurality of conductive layers are formed on the wiring pattern 5. A first conductive layer 31 formed in the extension portion and connected to the wiring pattern, and formed on the surface side of the first conductive layer 31, and at the end portion on the through hole 2 side, the first conductive layer 31 The second conductive layer 32 is electrically and physically connected to each other. According to the first embodiment, when a lead wire of an arbitrary electronic component is inserted into the through hole 2 of the land 3 and connected and fixed with lead-free solder, the extension of the wiring pattern 5 is not connected. The first conductive layer 32 is peeled between the second conductive layer 32 and the insulating layer 6 made of solder resist, and the first conductive layer 31 connected at the extension of the wiring pattern 5 is prevented from peeling. The effect that the disconnection of the wiring pattern 5 connected to the layer 31 can be prevented is obtained.

  The first conductive layer 31 and the second conductive layer 32 are electrically and physically (mechanically) connected only on the through hole 2 side of the land 3, and only the lower first conductive layer 31 has the wiring pattern 5. Since the second conductive layer 32 and the insulating layer 6 are easily connected to each other, the first conductive layer 31 connected to the extended portion of the wiring pattern 5 is prevented from being peeled off. Thus, disconnection of the wiring pattern 5 can be prevented. Further, the insulating layer 6 made of a solder resist interposed between the first conductive layer 31 and the second conductive layer 32 causes the first conductive layer 32 to peel off only, and is connected to the wiring pattern 5. This contributes to prevention of peeling of the conductive layer 31.

In addition, the surface of the insulating layer 6 is not subjected to surface roughening by chemical polishing that is normally performed, and the surface roughness is 1 μm or less. Peeling is easily generated between the layer 32 and the insulating layer 6, preventing the first conductive layer 31 connected to the wiring pattern 5 from being peeled, and effectively preventing the wiring pattern 5 from being disconnected. Moreover, even if the length of the land 3 from the end of the through hole 2 to the outer periphery of the land 3 is as small as 0.8 mm or less, the first conductive layer 31 connected to the wiring pattern 5 is peeled off. By preventing this, it is possible to provide a highly reliable printed wiring board that prevents the wiring pattern 5 from being disconnected.
Further, in the electronic apparatus (not shown) using the printed wiring board according to the first embodiment, the wiring pattern 5 is disconnected due to the use of the printed wiring board having the above-described specific configuration and effect. The effect that it is prevented and reliability is improved is obtained.

  Further, in the method for manufacturing a printed wiring board according to the first embodiment, the step of forming the through hole 20 in the base material 4 and the formation of the first conductor 81 across the inner wall of the through hole 20 and the surface of the base material 4 A step of selectively removing the first conductor 81 by photolithography to form the first conductive layer 31 and the wiring pattern 5, a surface of the substrate 20, the first conductive layer 31, and A step of forming the insulating layer 6 on the wiring pattern 5, a step of forming the second conductor 82 across the inner wall of the through hole 20 and the insulating layer 6, and the second conductor 82 by photolithography. And the step of forming the second conductive layer 32 by selectively removing the lands 3, the lands 3 provided in the through holes 2 are formed in a plurality of conductive layers, and a plurality of lands constituting the lands are formed. Of the conductive layers, the uppermost second conductive layer Only 2 is formed easily removed, there is an effect that the first conductive layer 31 a high printed circuit board disconnection reliability which prevents the wiring pattern 5 by preventing the release of the lower layer is obtained.

Embodiment 2. FIG.
FIG. 4 is an explanatory view showing the printed wiring board manufacturing method according to the second embodiment of the present invention in the order of steps. Note that the same reference numerals denote the same or corresponding parts throughout the drawings. In the second embodiment, a base material 4A made of a so-called copper-clad laminate provided with copper foil 42 on the front and back of a substrate 41 in which a glass cloth similar to that of the first embodiment is impregnated with an epoxy resin (FIG. 4A). ) Is used. First, a through hole 20 having a diameter of 0.9 mm is formed in a predetermined portion of the base material 4A with a drill or the like (FIG. 4B). Next, electroless copper plating and electrolytic plating are performed on the inner wall of the through hole 20 and the surface of the copper foil 42 to form the first conductor 81 composed of the electroless copper plating layer 81a and the electrolytic plating layer 81b (FIG. 4). (C)). Subsequently, the first conductive body 81 is etched by coating with a patterning resist to form the wiring pattern 5 and the first conductive layer 31 having a diameter of 1.3 mm connected by an extension of the wiring pattern 5 ( FIG. 4 (d)).

  Further, the insulating layer 6 is formed by printing and applying a solder resist on the surface of the substrate 41, the first conductive layer 31 and the wiring pattern 5, and thermosetting (FIG. 4E). Further, electroless copper plating and electrolytic plating are performed on the inner wall of the through-hole 20 and the insulating layer 6 made of solder resist to form a second conductor 82 made of the electroless copper plating layer 82a and the electrolytic plating layer 82b. (FIG. 4 (f)). Further, the second conductor 82 is etched by coating with a patterning resist to form a second conductive layer 32 having a diameter of 1.3 mm (FIG. 4G). Finally, the solder resist 7 is printed and applied, exposed, developed, and thermally cured to obtain a printed wiring board 1A according to the second embodiment of the present invention (FIG. 4 (h)).

  The printed wiring board 1A obtained as described above is the same as the first embodiment except that the land 3 provided in the through hole 2 is the same as in the first embodiment except that the base material 4A made of a copper-clad laminate is used. The conductive layer 31 and the second conductive layer 32 are composed of a plurality of conductive layers, and the same effect can be obtained by the same operation as in the first embodiment.

  Needless to say, the sizes and shapes of the through holes 2 and the lands 3 shown in the first and second embodiments are merely examples, and are not limited to those illustrated. In addition, although the insulating layer 6 made of a solder resist is provided between the first conductive layer 31 and the second conductive layer 32, the insulating layer 6 may be replaced with another. In short, the second conductive layer 32 can be easily peeled off from the first conductive layer 31, and other materials can be used as long as they have the same function as the solder resist. Of course, various modifications and changes can be made within the scope of the present invention.

Sectional drawing which shows typically the through-hole part of the printed wiring board which concerns on Embodiment 1 of this invention. Explanatory drawing which shows the manufacturing method of the printed wiring board shown in FIG. 1 in order of a process. Sectional drawing which shows typically the through-hole part of the electronic device which inserted the lead wire of the circuit component in the through-hole of the printed wiring board shown in FIG. 1, and was connected and fixed with the lead-free solder. Explanatory drawing which shows the manufacturing method of the printed wiring board by Embodiment 2 of this invention in order of a process.

Explanation of symbols

  1, 1A printed wiring board, 2 through hole, 3 land, 31 first conductive layer, 32 second conductive layer, 4 base material, 4A base material (copper-clad laminate), 41 substrate, 42 copper foil, 5 Wiring pattern, 6 insulating layer, 7 solder resist, 81 first conductor, 82 second conductor, 9 lead wire, 10 lead-free solder, 20 through hole.

Claims (9)

  A printed wiring board, wherein a land provided in a through hole is composed of a plurality of conductive layers.   The plurality of conductive layers are formed on an extension portion of the wiring pattern and connected to the wiring pattern, and are formed on the surface side of the first conductive layer. The printed wiring board according to claim 1, comprising a second conductive layer electrically and physically connected to the first conductive layer.   The printed wiring board according to claim 1, wherein an insulating layer is interposed between the plurality of conductive layers.   The printed wiring board according to claim 3, wherein the insulating layer has a surface roughness of 1 μm or less.   5. The print according to claim 1, wherein a dimension from an end portion of the through hole to an outer end portion of the uppermost conductive layer constituting the land is 0.8 mm or less. 6. Wiring board.   6. An electronic device, wherein a lead wire of a circuit component is inserted into the through hole of the printed wiring board according to any one of claims 1 to 5, and connected and fixed by solder.   The electronic device according to claim 6, wherein the solder is lead-free solder.   A step of providing a through hole for forming a through-hole in the substrate, a step of forming a first conductor across the inner wall of the through hole and the surface of the substrate, and the first by photolithography Forming a first conductive layer and a wiring pattern for selectively removing a conductor to form a land, and forming an insulating layer on the substrate surface, the first conductive layer, and the wiring pattern; A step of forming a second conductor across the inner wall of the through-hole and the insulating layer, and the land is formed by selectively removing the second conductor by photolithography. And a step of forming a second conductive layer.   The method for producing a printed wiring board according to claim 8, wherein a copper clad laminate having copper foil on the front surface and the back surface is used as the substrate.

Images