JP2007287868A - Printed wiring board, and method of manufacturing printed wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printed wiring board that is equipped with interconnections, whose routing is minimally carried out, which is suitable for high-density mounting, and excellent noise-resistant properties, and to provide its manufacturing method. <P>SOLUTION: The printed circuit board with a base board of resin is provided with through-holes whose inner walls are covered with conductors and pads to which the conductor terminals of parts mounted on the surface of the printed wiring board are connected. The pad is configured in such a manner that the through-hole is arranged within its region, the through-hole is filled up with a prescribed filler, and the end of the filler located at the surface of the printed wiring board is covered with the pad of a conductor. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a structure of a printed wiring board, and more particularly to a printed wiring board in which a through hole filled with a filler is disposed in a pad of a surface-mounted component to be mounted and a method for manufacturing the printed wiring board.

  In portable electronic devices such as cellular phones, portable music players, and PDAs (Personal Digital Assistants), it is common to mount surface-mounted components on a multilayer printed wiring board for miniaturization. In particular, electronic circuits have recently become larger and more complicated, and high-density mounting technology for printed wiring boards has become important.

  Along with the increase in the density of printed wiring boards, the drive voltage has been lowered, and countermeasures against noise have become important. As countermeasures against noise, a bypass capacitor is inserted between the power supply (VCC) and ground (GMD) of the digital IC. However, in mounting high-density, low-voltage printed wiring boards, bypass capacitors are more than ever. It is required to pay attention to the placement and wiring.

  FIG. 4 shows a conventional structure in which a bypass capacitor is mounted on a multilayer printed wiring board. 4A shows an example in which a multilayer printed wiring board 100 has conductor layers of signal layers 101 and 102 on the substrate surface, and signal layers 103, ground layers 104, and power supply layers 105 as inner layers. The IC 300 as a mounting component forms pads 140 and 150 by the conductive foil of the signal layer 101 on the surface of the printed wiring board 100, and the metal balls 310 and 320 as terminals of the IC 300 are formed by the pads 140 and 150 and the solder 400. Connected.

  Here, the surface of the printed wiring board 100 on which the IC 300 is mounted is referred to as a component surface, and the opposite surface is referred to as a back surface here. A bypass capacitor 200 is mounted on the back surface. The bypass capacitor 200 is a chip capacitor, and both ends form a terminal portion chased by solder, and the terminal portion is connected to pads 160 and 170 formed on the back surface by solder. The pad 160 is connected to the ground layer 104, and the pad 170 is connected to the power supply layer 105 through the through holes 110 and 120, respectively. Further, the pad 140 of the IC 300 described above is also connected to the power supply layer 105 (that is, the metal ball 310 is a power supply terminal of the IC 300), and the bypass capacitor 200 does not allow noise from the power supply to the IC 300 to flow into the IC 300. It works to drain to the ground.

  The component surface and back surface of FIG. 4A are each coated with a solder resist 180. The solder resist 180 is for preventing the solder from flowing to a portion other than the pad when connecting by solder.

FIG. 4B shows a printed wiring board pattern when FIG. 4A is viewed from the component side. The pads 140 and 150 that connect the IC 300 and the through holes 110, 120, and 130, and the wiring pattern 190 that connects the pads and the through holes are shown. The portions other than the pattern and the through hole are covered with a solder resist 180. FIG. 4C shows a pattern of the printed wiring board when FIG. 4A is viewed from the back side.
As shown in FIGS. 4A to 4C, the through holes 110-130 are formed separately from the pads 140-170 of the mounting components, and are connected by a wiring pattern 190 therebetween. The through-hole 110 and the through-hole 120 connected to the power supply layer and the ground layer are provided with a power supply terminal and a ground terminal pad (a power supply terminal pad 140 of the IC 300, a bypass capacitor) in order to reduce wiring as much as possible. 200 power supply terminal pad 170 and bypass capacitor 200 ground terminal pad 160 are formed in the vicinity. The reason why the through hole is not formed in the pad is that when the mounting component is soldered to the pad, the solder flows into the through hole, and a sufficient amount of solder for connection may not be ensured.

A through hole of a printed wiring board using a resin such as glass epoxy as a substrate generally covers an inner wall with plating, and the inside is hollow as shown in FIG. However, in the case of a ceramic substrate, it is difficult to connect the layers by plating because it is desired to reduce the hole diameter, and the via hole is used in the via hole (since the ceramic substrate is laminated and sintered with a sheet having holes, the via hole is used). In many cases, it is filled with a conductive material, and the connection between the layers is made with the conductive filler. However, it has been reported that in a printed wiring board other than a ceramic substrate, a conductive material is filled in a through hole. According to this report, printed wiring boards based on paper are filled with silver paste in the through hole and cured to prevent thermal expansion in the thickness direction and shrinkage due to moisture absorption, thereby improving the connection reliability of the through hole. (For example, Patent Document 1).
Japanese Patent Laid-Open No. 54-097778

  As described above, it is common to form the pads and through-holes for connecting the mounted components separately, and connect them with a wiring pattern between them. This is because the solder may flow into the through hole when connecting the mounted components, and a sufficient amount of solder for connection may not be obtained.

  For this reason, in a printed wiring board that requires high-density mounting, there is a problem in that the pads and the through holes are formed separately from the viewpoint of space efficiency of the printed wiring board. For this reason, the length of the wiring is increased, which increases resistance due to the wiring and makes it vulnerable to noise. In particular, the bypass capacitor is disposed near the power supply pin of the IC and is required to be connected to the power supply and ground at a short distance. If this requirement is not satisfied, there is a risk that the circuit will not function normally in a medium or large-scale circuit with an IC signal speed of 100 Mbp or more.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a printed wiring board that integrates a pad and a through hole to minimize wiring routing, is suitable for high-density mounting, and has excellent noise resistance, and a method for manufacturing the same. .

The printed wiring board and the manufacturing method thereof according to the present invention are configured as follows.
(1) 1st invention 1st invention arrange | positions the through hole which filled the inside with the filler in the pad formed in the printed wiring board.

  This printed wiring board is made of resin, and has a through hole whose inner wall is covered with a conductor, and a pad for connecting a terminal of a mounted component formed of a conductor on the surface of the printed wiring board. The pad has a through hole in the pad area, the inside of the through hole is filled with a predetermined filling material, and a conductor that forms the pad at the opening portion of the surface of the printed wiring board of the filling material. It is covered with.

  The pad is used for solder-connecting a surface-mounted component to a printed wiring board. For example, a copper foil, which is a conductor on the surface of the printed wiring board, is formed into a circular or square shape by etching. The through hole is a hole penetrating the printed wiring board from the front surface to the back surface, and the through hole is formed by, for example, a drill. The inner wall is covered with a copper metal conductor by plating, and the conductor on the inner wall is connected to the inner layer conductor as necessary.

According to the first invention, even if there is a through hole in the pad, the inside of the through hole is filled with the filling, and the surface portion of the printed wiring board of the filling is covered with the pad conductor. Even in the solder bonding of mounted components, a highly reliable connection is possible without the solder flowing into the through hole as in the prior art.
(2) Second invention The second invention is characterized in that the filler filled in the through hole is an insulator or a conductor.

According to the second invention, if the filler is an insulator, it can be filled with a low-cost material, and if the filler is a conductor, a conductor circuit having a low conductor resistance can be formed.
(3) Third Invention The third invention is a method for manufacturing a printed wiring board according to the first invention.

  According to the first invention, a printed wiring board having a connection structure suitable for high-density mounting can be provided. Moreover, the printed wiring board excellent in noise resistance can be provided.

  According to the second invention, if the filler is an insulator, a printed wiring board suitable for high-density mounting can be provided at a low cost, and if the filler is a conductor, it is suitable for high-density mounting having a low-resistance conductor circuit. Printed wiring boards can be provided.

  According to the third aspect of the invention, it is possible to provide a method for manufacturing a printed wiring board that has the same effect as the first aspect and is excellent in noise resistance.

  An embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 is a diagram for explaining an embodiment of the first invention, and shows an example of a printed wiring board 1000 when the conventional printed wiring board 100 explained in FIG. 4 is replaced by the method of the present invention. In FIG. 1, only the symbols different from those shown in FIG. 4 are given symbols, and those without symbols are the same as those in FIG. FIGS. 1A to 1C correspond to FIGS. 4A to 4C, respectively.

  In FIG. 1A, a through hole 1100 corresponds to the through hole 110 in FIG. 4A, and a pad 1600 of the bypass capacitor 200 corresponds to the through hole 1600 in FIG. The through hole 1100 is inherent in the pad 1600. Further, the through hole 1200 is inherent in the pad 1700 and the pad 1710. As shown in the enlarged view of FIG. 1A, the structure is filled with a filling 1210, and the surface portion of the printed wiring board 1000 of the filling 1210 is covered with a pad 1710. ing. Therefore, the solder 400 that connects the terminals of the IC 300 does not flow into the through hole 1200.

  FIG. 1B shows an example viewed from the component side, and shows pads 1610, 1710, and 1320, and through holes 1100, 1200, and 1300 are formed on the back surfaces thereof (through holes are indicated by dotted lines). ). FIG. 1C shows an example when viewed from the back side, and the pads 1600 and 1700 have through holes 1100 and 1200 formed on the back side.

  FIG. 2 is a diagram for explaining an example in which space saving can be achieved by the first invention. FIG. 2A shows an example of a printed wiring board according to the prior art. Pads and through-holes are individually formed, and a wiring pattern is connected between them. On the other hand, as shown in FIG. 2B, in the present invention, a through hole is formed in the pad. Therefore, as shown in the lower diagram of FIG. That is, a dotted rectangular space shown in the lower diagram of FIG. 2B is created.

  Next, the manufacturing process of the printed wiring board by this invention is demonstrated using FIG. FIG. 3A shows a material to be laminated, and shows an example in which a prepreg 510 and a copper foil 520 are laminated from both sides of a copper-clad laminate 500. In this example, for example, the copper foil 520 on the surface of the printed wiring board is used as the signal layer (two layers), and the copper foil of the copper-clad laminate 500 as the inner layer is used as the power supply layer and the ground layer. In the copper-clad laminate 500, the power supply layer and ground layer conductor patterns are formed by etching or the like. In FIG. 2B, the materials shown in FIG. 1A are laminated and bonded by hot pressing. In FIG. 4C, a hole is formed in the bonded substrate to form a through hole with a drill, and the whole is plated as shown in FIG. Thereby, plating is performed including the perforated inner wall. Subsequently, in FIG. 4E, the resin is filled in the through hole for plating after plating. The resin is, for example, an epoxy resin. After the resin is filled, plating is performed again ((f) in the figure). As a result, the resin filled in the opening of the hole is also plated ((f) in the figure). After plating is performed, a pattern of a conductor circuit for pads and wiring is formed on the surface of the printed wiring board by etching or the like (FIG. 5G). Thereafter, the solder resist 180 is coated by, for example, silk printing to complete a printed wiring board ((h) in the figure).

  With the above, a printed wiring board having a through hole filled with a filler in the pad of the present invention can be manufactured. This example is merely an example of manufacturing, and a printed wiring board having a through hole in the pad of the present invention may be manufactured by other methods.

  Further, here, the resin is filled in the through hole, but a conductive paste such as a silver paste may be filled and cured. In this way, the resistance value of the through hole can be lowered. In such a case, the conductor by plating can be made unnecessary on the inner wall of the through hole.

It is a structural example of the printed wiring board by 1st invention. It is a space-saving example by 1st invention. It is an example of the manufacturing method of the printed wiring board by 3rd invention. It is a structural example of the conventional printed wiring board.

Explanation of symbols

100 Printed wiring board 101 Signal layer (surface layer)
102 Signal layer (surface layer)
103 Signal layer (inner layer)
104 Ground layer (inner layer)
105 Power supply layer (inner layer)
110 Through hole 120 Through hole 130 Through hole 140 Pad (for IC-power supply terminal)
150 pads (for IC-signal terminals)
160 Pad (Bypass capacitor for ground terminal)
170 Pad (Bypass capacitor for power supply terminal)
180 Solder resist 190 Wiring pattern 200 Bypass capacitor 300 IC
310 Metal ball (IC power supply terminal)
320 Metal ball (IC signal terminal)
400 Solder 500 Copper-clad laminate 510 Prepreg 520 Copper foil 530 Drill hole 540 Copper plating 550 Resin (insulator)
560 Copper plating 570 Pad 1000 Printed wiring board 1100 Through hole 1200 Through hole 1210 Filling 1300 Through hole 1310 Land for through hole 1320 Pad (for IC-signal terminal)
1600 pad (for bypass capacitor-ground terminal)
1610 Land for through hole 1700 Pad (Bypass capacitor for power supply terminal)
1710 Pad (for IC-power supply terminal)

Claims (3)

A printed wiring board based on resin,
The printed wiring board has a through hole whose inner wall is covered with a conductor, and a pad for connecting a terminal of a mounting component formed with the conductor on the surface of the printed wiring board,
The pad has the through hole disposed in the pad, the inside of the through hole is filled with a predetermined filling, and the opening of the printed wiring board of the filling is covered with the pad.
A printed wiring board characterized by that. The printed wiring board according to claim 1, wherein the filler is an insulator or a conductor. A method of manufacturing a printed wiring board based on a resin,
Open a hole that penetrates the laminated substrate of the printed wiring board, cover the inner wall of the hole with a conductor to form a through hole,
Fill the inside of the through hole with a filler,
A pad for forming a conductor film on the surface of the printed wiring board including the filling of the through hole exposed on the surface of the printed wiring board, and connecting a terminal of a mounting component having the through hole from the conductor film Forming,
A printed wiring board manufacturing method characterized by the above.

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