JP2653905B2 - Printed circuit board manufacturing method and electronic component mounting method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

The present invention relates to a method of manufacturing a printed circuit board having a wiring pattern that can be mounted on both front and back surfaces and a method of mounting electronic components using the same, and particularly to a method of manufacturing a printed circuit board suitable for high-density mounting and an electronic device using the same. The present invention relates to a component mounting method.

[Prior art]

In a conventional printed circuit board for double-sided mounting, as a general method of connecting a wiring pattern, as shown in a sectional view of FIG. 6, a wiring pattern 1a provided on both sides of the substrate 1 by through holes 3 is electrically connected. It has a structure to connect to. In mounting electronic components, those having leads 5a, such as lead components 5, are inserted into through holes and soldered to the substrate by, for example, solder reflow. In addition, a chip component having no leads (also called an imposition component) such as a semiconductor LSI 6
As for (2), the connection terminal 6a of the chip component is connected to the soldering land 7 of the wiring pattern on the surface of the substrate by the paste solder 8. A chip in which metal plating is applied to the surface of an insulator made of the same material as the base material 2 in advance or a conductive paste is embedded in the periphery or the lower through hole where the chip component 6 is mounted. is there. As a printed wiring board of this type, for example, JP-B-61-35720 is cited.

[Problems to be solved by the invention]

As described above, when mounting components on a printed circuit board, lead components and chip components are often mounted in a mixed manner, and as the mounting density increases, the number of through holes provided in the printed circuit board increases. As a result, the area of the through hole occupying the wiring pattern also increased, which hindered the mounting of chip components. That is,
The chip component has its connection terminals 6a connected to the soldering lands 7 of the wiring pattern on the surface of the board by paste solder 8, but if this through-hole exists immediately below the connection, this through-hole is buried with a conductor and stable there. It is necessary to form a secure connection. As this embedding method, none of the conventional embedding methods of embedding a metal-plated chip on the surface of an insulator or embedding a conductive paste has been practical. That is, in the former, the higher the density, the more difficult it becomes to embed the chip. In the latter, as shown in the left terminal 6a of FIG. There was a problem that occurred. In any of the above methods, the connection of the chip component 6 is
Only the connecting portion is spot-shaped by the conductive paste, and the solderability of the connecting portion is not considered. Accordingly, an object of the present invention is to solve these conventional problems, and a first object of the present invention is to provide a through-hole so that lead components and chip components can be mixed and mounted at a high density. Of the printed circuit board on which the chip parts can be soldered by forming soldering lands on the through-holes of the buried traces as well as other wiring patterns. A second object of the present invention is to provide a method of mounting an electronic component using a substrate obtained by the method of manufacturing a printed circuit board.

[Means for Solving the Problems]

The first object of the present invention is (1). A step of preparing a substrate in which conductive foils are adhered to both surfaces of the insulating base material, a step of providing a through hole having a predetermined diameter (through hole) in the substrate, and a step of applying a plating catalyst at least in the through hole; Performing an electroless plating process on the entire surface of the substrate including the inside of the through-hole to form a first plating film; and filling a predetermined specific through-hole in the through-hole with a conductive material. Forming a second plating film by plating the entire surface of the substrate including the inside of the through hole (through hole not filled with the conductive material), and the entire surface of the through hole opening and the trace of the through hole filled with the conductive material. Forming a resist pattern for forming a wiring pattern connected to the land, respectively, and using the resist pattern as a mask. Achieved by a method for manufacturing a printed circuit board comprising a step of selectively etching a conductive foil on which the plating film is laminated to form the lands and the wiring pattern, and a step of removing the resist mask. Is done. More preferably, (2). Instead of laminating the conductor foil on both sides of the insulating base as described in (1) above, applying an adhesive to the surface of the insulating base to improve the adhesion between the plating film formed in a later step and the base. This is achieved by a method of manufacturing a printed circuit board, which comprises a step of preparing a processed board. In other words, this manufacturing method differs from that of the above (1) in that instead of using a substrate in which conductor foil is adhered to both surfaces of an insulating base material, the method also serves as a conductor plating process in through holes of the insulating base material. The point is that a conductor plating layer is formed as a pair on both surfaces. (3). The plating treatment in the step of forming the second plating film according to the above (1) or (2) may be either an electrolytic plating treatment or an electroless plating treatment. When a substrate is used, electroless plating is practical. In the case of using a substrate on which no conductor foil is bonded, electrolytic deposition is faster and more practical if electrolytic plating is performed in order to secure a required thickness as a wiring conductor. Still preferably, (4). After the step of removing the resist mask according to any one of the above (1) to (3), a step of forming a solder resist on the entire surface of the substrate except for lands and through holes required for component connection is added. This is achieved by a method for manufacturing a printed circuit board. As the conductive material, for example, a conductive paste such as a silver paste or a copper paste is practical because of easy filling into the through holes. In addition, as a filling method, printing is easy and desirable. As the conductor foil, a copper foil that is commonly used, and as a plating treatment, an electroless copper plating treatment,
Alternatively, electrolytic copper plating is practical and preferable. Furthermore, as the solder resist, a commercially available heat-resistant resin such as an epoxy resin or a polyimide is used. The second object of the present invention is: (5). Following the method of manufacturing a printed circuit board according to any one of (1) to (4), a lead of a lead component is provided in the through hole, and a surface is provided on a land of the trace of the through hole filled with the conductive material. This is achieved by a method of mounting an electronic component in which lead components and imposition components are mixedly mounted, including a process of mounting and arranging components to be mounted and connecting them by soldering. And preferably, (7). It is desirable that the step of soldering the components is a process of dividing the connection of the imposed components and the connection of the lead components into two stages by using solders having different melting points, and performing a solder connection. That is, the connection solder of the imposed component is connected earlier than the lead component as having a higher melting point than that of the lead component, or vice versa, but the former is practically preferable.

[Action]

The embedding of a conductive material into a specific through-hole according to the present invention may be performed by embedding the through-hole in the substrate immediately after plating, or by embedding the entire surface of the substrate (including the inner wall of the penetrating through-hole). For example, there are two methods of embedding after forming a copper plating film by electroless plating. Of course, after embedding this conductive material, a plating film is always formed by electroless plating on the entire surface of the substrate including the inner wall of the through hole that penetrates. In the trace of the through hole in which the conductive material is embedded, a land of the plating film (which becomes a connection electrode of the imposition chip) is formed. Therefore, the lands are formed in the same wiring pattern forming process as the lands formed in the regions where the through holes are not formed, and are formed of the same copper plating film, so that the connectivity of components is good. That is, the connection of the imposition components is performed at the plating film land. Since the conductive material embedded in the through hole has a structure sealed by the plated film land, there is no danger of flowing out at the time of solder connection or sinking in the through hole to cause a connection failure. Furthermore, the formation of the plating film for the land formation and the formation of the land pattern by selective etching thereafter are performed by plating both surfaces of the substrate including the inner wall of the through hole,
Since this step is performed in a series of steps for forming a wiring pattern necessary for the plating film, there is no need to provide a special step.

【Example】

Hereinafter, an embodiment of the present invention will be described with reference to the process diagrams shown in the drawings. Example 1 FIG. 1 shows a method of forming a first layer copper plating film 10a in a through hole 3 in the same manner as a conventional method of manufacturing a printed circuit board, and then placing a conductive material 9 in a predetermined through hole 3. FIG. 2 is a cross-sectional view of a main part of the substrate, showing a configuration in which a wiring pattern 1a including lands 7 is formed on both surfaces of the substrate 1 by selective embedding, followed by forming a second-layer plated copper film 10b and then performing selective etching. Hereinafter, a more specific description will be given with reference to the process diagram of FIG. FIG. 2 shows a state of manufacturing according to a well-known subtractive method of manufacturing a printed circuit board. FIG. 2 (a) shows a process of preparing a board having copper on both sides of an insulating base material 2. (B) is a through-hole forming step of providing a through-hole 3 with a drill, and (c) is a step of applying electroless copper plating after applying a plating catalyst such as palladium to the entire surface of the substrate including the inside of the through-hole. A step of forming a first-layer copper plating film 10a, FIG. 4D shows a step of embedding a conductive material (eg, silver paste or copper paste) 9 in a specific through hole 3 by printing, and FIG. A step of forming a second-layer copper plating film 10b by applying a second electroless copper plating, and FIG. 6F shows a step of forming a resist pattern 12 for forming a wiring pattern 1a including the lands 7; Process, FIG. The resist pattern 12 a copper layer is selectively etched as a mask, a step of forming a wiring pattern 1a including land 7 illustrates respectively. As described above, the basic printed circuit board manufacturing process is completed in the above steps, but it is preferable to continue to the next step. FIG. 3H shows that after removing the resist pattern 12, the lands 7 (including the through holes 3) necessary for connection are removed.
A step of coating the substrate surface with a known solder resist 13 will be described. Thus, the manufacturing process of the printed circuit board according to the present embodiment is completed. Next, following this manufacturing process, a mounting process of mounting electronic components on the obtained substrate 1 and soldering the same will be described. FIG. 2I shows a step of mounting an LSI chip as the surface mount component 6 and connecting the connection terminals 6 a thereof to the lands 7 formed with the through holes buried in the conductive material by solder reflow. (J) further mounts a lead component 5 and
5A and 5B respectively show steps of inserting 5a into the through-hole and making a solder connection. The solder used had a higher melting point than that of the lead component 5 and that of the surface mount component 6 so that the connection of the surface mount component 6 was not impaired when the lead component 5 was connected. In this way, the surface mount component 6 and the lead component 5 are mixedly mounted, and a printed board suitable for high-density mounting can be manufactured. Embodiment 2 FIG. 3 shows an example in which a printed circuit board is manufactured according to a well-known additive method instead of the subtractive method shown in FIG. FIG. 4A shows a step of preparing an adhesive-coated substrate which has been subjected to a base treatment so that a plating film formed in a later plating step on the insulating base material 2 is firmly adhered to the substrate. Is a through-hole forming step of providing a through-hole 3 with a drill (same as FIG. 2), and FIG. 2C is a diagram showing an electroless copper plating after applying a plating catalyst such as palladium to the entire surface of the substrate including the inside of the through-hole. Forming a first-layer copper plating film 10a by applying the same method (same as in FIG. 2). FIG. 2 (d) shows a conductive material (silver paste, copper paste, etc.) 9 in a specific through hole 3. (FIG. 2E) is a second plating step. In this case, a sufficient thickness of copper plating required as a wiring conductor by electrolytic plating is used. The process of forming the film 10b, hereinafter, from FIG. Are omitted since they are the same as those in FIG. In this way, a printed circuit board suitable for high-density mounting could be manufactured as in the case of the first embodiment. Example 3 FIG. 4 shows a manufacturing method similar to that of FIG.
In FIG. 3 (c), a step of forming a first copper plating film 10a by applying electroless copper plating after applying a plating catalyst such as palladium to the entire surface of the substrate including the inside of the through hole (second step) In the specific through hole 3 shown in FIG. 4D, a conductive material (such as silver paste or copper paste) 9
2 is a cross-sectional view of a main part in the case where the order of the step of embedding by printing is the same as that of FIG. In this case, the plating film 10a is formed on the entire surface of the substrate including the inside of the through hole after the conductive material 9 is embedded, although not shown in the drawing. The wiring pattern 1a including the land 7 is formed on the plating film 10a. FIG. 5 shows that the surface-mounted component 6 and the lead component 5 are mixedly mounted on the substrate having the structure shown in FIG. 4 in the same process as in FIGS. 2 (i) and 2 (j) of the first embodiment. , Implemented. A printed circuit board suitable for high-density mounting could be manufactured in the same manner as in any of the above embodiments.

【The invention's effect】

As described in detail above, according to the present invention, surface mount components and lead components can be mixedly mounted at a high density. In other words, in the method of manufacturing a printed circuit board, even if many through holes are provided for high-density mounting,
The through-holes in the connection area required for surface mounting can be easily formed as buried electrode connection lands with conductors. In mounting, especially when mounting surface mount components, the lands formed by embedding through holes are made of a plated film, so that the solder connection of the components is good, and highly reliable mounting is realized. Now you can do it. Specifically, by performing these two plating treatments, first, the plating and the conductive material in the through hole by the first plating and the conductive material filled in the specific through hole are performed. In addition, the overall plating including the traces of the through holes (second plating) also has the effect of preventing the filled conductive material from being deteriorated by subsequent moisture absorption, oxidation, corrosion, and the like. Further, these two plating treatments also contribute as a secondary effect to the improvement of the strength of through holes for inserting components that are exposed to solder during mounting or come into contact with lead wires.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a printed circuit board according to an embodiment of the present invention, FIG. 2 is a cross-sectional perspective view showing one process drawing, FIG. FIG. 5 is a cross-sectional view of a printed circuit board showing another embodiment, FIG. 5 is a mounting cross-sectional view showing another embodiment of the same, and FIG. 6 is a cross-sectional view of components of a conventional printed circuit board. <Explanation of reference numerals> 1 ... board, 1a ... wiring pattern, 2 ... insulating base material, 3 ... through hole, 4 ... solder, 5 ... lead component, 6 ... mounting component (chip component) , 7: soldering land, 8: paste solder, 9: conductive material, 10: plated copper, 11: connection hole, 12: resist pattern, 13: solder resist.

Continuation of the front page (56) References JP-A-1-266794 (JP, A) JP-A-2-196494 (JP, A) JP-A-1-160082 (JP, A) JP-A 64-26876 (JP) , U)

Claims (6)

(57) [Claims] 1. A step of preparing a substrate in which conductive foil is adhered to both surfaces of an insulating base material, a step of providing a through hole having a predetermined diameter in the substrate, and a step of providing a plating catalyst in at least the through hole. Applying, electroless plating the entire surface of the substrate including the inside of the through-hole to form a first plating film, and filling a predetermined specific through-hole in the through-hole with a conductive material. A step of performing a plating process on the entire surface of the substrate including the inside of the remaining through hole to form a second plating film; and forming a land on the entire surface of the through hole opening and the trace of the through hole filled with the conductive material. Forming a resist pattern for forming a wiring pattern connected to the land; and laminating the plating film using the resist pattern as a mask. The selectively etching the conductive foil, wherein the lands and the step of forming the wiring pattern, the resist mask step and the printed circuit board manufacturing method comprising a to remove. 2. An adhesive coating process for improving the adhesion between a plating film formed on a surface of an insulating substrate and a substrate in a subsequent step, instead of laminating a conductor foil on both surfaces of the insulating substrate. 2. The method for manufacturing a printed circuit board according to claim 1, comprising a step of preparing a board subjected to the above. 3. The method for manufacturing a printed circuit board according to claim 2, wherein the plating in the step of forming the second plating film is electrolytic plating or electroless plating. 4. The method according to claim 1, further comprising, after the step of removing the resist mask, a step of forming a solder resist on the entire surface of the substrate except on lands and through holes. Manufacturing method of printed circuit board. 5. A method for manufacturing a printed circuit board according to claim 1, wherein a lead of a lead component is provided on the land of the trace of the through hole filled with a conductive material. Is a mounting method of an electronic component in which lead components and imposition components are mixed, including a process of mounting and arranging imposition components and soldering each. 6. The electronic device according to claim 5, wherein the step of soldering the components is a process in which the connection of the imposed components and the connection of the lead components are divided into two stages by using solders having different melting points, and soldered. Component mounting method.