JP2016189400A - Method of manufacturing multilayer printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a multilayer printed wiring board capable of exhibiting good solder wettability in a through hole.SOLUTION: A method of manufacturing a multilayer printed wiring board forms a through hole in a laminated board, forms a metal film projecting in the radial direction of the through hole on the circumference thereof, forms a conductive portion by making a pin penetrate through the through hole, thereby causing plastic deformation of the metal film so as to cover the inner peripheral surface of the through hole, fuses solder on the laminated board surface, and then spreads the solder along the conductive portion and fills the through hole with the solder.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for manufacturing a multilayer printed wiring board in which a plurality of circuit boards are laminated.

  Patent Document 1 discloses a method for manufacturing a multilayer printed wiring board. In the manufacturing method described in Patent Document 1, via holes reaching the circuit pattern from the printed wiring surface to the insulating base material are formed in the insulating base material by the perforation pins, and at the same time, the interlayer connection portion is plastically deformed to reach the interlayer terminal portion through the via hole. A cylindrical portion is formed. After forming the cylindrical portion, the via hole is filled with a conductive material having fluidity.

  In the mounting substrate described in Patent Document 2, a copper foil film that connects the pattern wirings formed on both ends of the through hole is formed on the inner peripheral surface of the through hole. Cream solder is filled and solidified in the internal space of the through hole.

  Patent Document 3 describes a method for manufacturing a multilayer ceramic electronic component. In the manufacturing method described in Patent Literature 3, when a through hole is formed in a ceramic green sheet, punching is performed so as to cover a part of a region where the surface conductor film is formed on the ceramic green sheet. Thereby, the surface conductor film is deformed so as to extend to the inner peripheral surface of the through hole.

  Patent Document 4 describes a method of manufacturing a multilayer printed board having a through hole that electrically connects a plurality of conductive pattern layers through a conductive member formed on an inner wall surface. Lead pins of lead components are inserted into the through holes and soldered with solder.

Japanese Patent Laid-Open No. 2002-076665 JP 2004-022729 A JP 2004-165343 A JP 2002-246718 A

  With the downsizing, thinning, and high functionality of electronic devices, there is an increasing demand for higher density of electronic components mounted on the printed wiring board and higher functionality of the printed wiring board. In order to satisfy this requirement, multilayer printed wiring boards with built-in components in which electronic components such as chip capacitors and chip resistors are embedded in the substrate have been developed.

  In a multilayer printed wiring board with a built-in component, a prepreg is used as an interlayer material containing the component. In the component-embedded multilayer printed wiring board, the prepreg is thick due to the structure in which the component is built, and the land portion provided with the through hole of each circuit board is separated. For this reason, when the lead component is mounted in the through hole by solder, there is a problem that heat is not transmitted to the lower circuit board and the solder does not spread well in the through hole.

  In Patent Document 1, since the copper plating layer serving as the interlayer connection portion is extended simultaneously with the formation of the via hole, the waste of the substrate generated when the via hole is formed inhibits the copper plating layer from extending. For this reason, the interlayer connection portion cannot be formed on the inner wall surface of the via hole so as to reach the lower-layer interlayer terminal portion, and the conductor material may not sufficiently spread along the interlayer connection portion.

  The present invention has been made against the background of the above problems, and an object of the present invention is to provide a method for manufacturing a multilayer printed wiring board capable of exhibiting good solder wettability in a through hole. That is.

  In the method for manufacturing a multilayer printed wiring board according to the embodiment, a through hole is formed in a multilayer substrate, a metal film projecting in a radial direction of the through hole is formed at a periphery of the through hole, and a pin is passed through the through hole. By causing the metal film to plastically deform so as to cover the inner peripheral surface of the through hole, a conductive portion is formed, the solder is melted on the surface of the laminated substrate, and the solder is spread along the conductive portion. Fill through hole.

  According to the embodiment, it is possible to provide a method for manufacturing a multilayer printed wiring board capable of expressing good solder wettability in a through hole.

It is a perspective view which shows the structural example of the multilayer printed wiring board which concerns on embodiment. It is sectional drawing which shows the structural example of the multilayer printed wiring board which concerns on embodiment. 6 is a manufacturing process cross-sectional view illustrating the method for manufacturing the multilayer printed wiring board according to Embodiment 1. FIG. 6 is a manufacturing process cross-sectional view illustrating the method for manufacturing the multilayer printed wiring board according to Embodiment 1. FIG. 6 is a manufacturing process cross-sectional view illustrating the method for manufacturing the multilayer printed wiring board according to Embodiment 1. FIG. 6 is a manufacturing process cross-sectional view illustrating the method for manufacturing the multilayer printed wiring board according to Embodiment 1. FIG. 5 is a manufacturing process cross-sectional view illustrating a method for manufacturing a multilayer printed wiring board according to Embodiment 2. FIG. 5 is a manufacturing process cross-sectional view illustrating a method for manufacturing a multilayer printed wiring board according to Embodiment 2. FIG. It is manufacturing process sectional drawing explaining the manufacturing method of the multilayer printed wiring board which concerns on a comparative example.

  Hereinafter, embodiments will be described with reference to the drawings. In the following drawings, components having the same action are denoted by the same reference numerals. In addition, the dimensional relationship in each figure does not reflect the actual dimensional relationship.

  With reference to FIG. 1, 2, the structure of the multilayer printed circuit board 10 concerning embodiment is demonstrated. FIG. 1 is a perspective view showing a configuration example of a multilayer printed wiring board according to the embodiment, and FIG. 2 is a cross-sectional view. As shown in FIGS. 1 and 2, the multilayer printed circuit board 10 includes a multilayer substrate 11, an electronic component 12, and a prepreg 13.

  As shown in FIG. 2, the laminated substrate 11 has a structure in which a plurality of substrates are laminated via a prepreg 13. Here, an example is shown in which three substrates, a first substrate 11a, a second substrate 11b, and a third substrate 11c, are stacked. In FIG. 1, the illustration of the second substrate 11b and the third substrate 11c disposed on the upper layer of the first substrate 11a is omitted for the sake of explanation.

  In the example of the multilayer printed circuit board 10 shown in FIG. 2, the prepreg 13 is disposed on the first substrate 11 a on which the electronic component 12 is mounted so as to cover the electronic component 12. On the upper layer of the prepreg 13, the second substrate 11b is disposed. A third substrate 11c is disposed on the second substrate 11b via a prepreg 13. That is, the multilayer printed circuit board 10 is a component built-in printed wiring board.

  Examples of the electronic component 12 include passive elements such as chip resistors and chip capacitors, and active elements such as ICs. Although not shown here, circuit patterns are formed on the substrates 11a to 11c. The circuit patterns on the substrates 11a to 11c are electrically connected by conductive portions in through holes (not shown in FIGS. 1 and 2).

  As the prepreg 13, for example, a glass cloth impregnated with an epoxy resin can be used. When using the prepreg 13 including a glass cloth, in order to prevent damage to the built-in electronic component, a portion where the electronic component 12 of the prepreg 13 is disposed is cut out and laminated as shown in FIG.

  On the other hand, a prepreg 13 that does not include a glass cloth may be used. For example, an epoxy resin or the like filled with a filler such as silica can be used. Since the prepreg that does not contain glass cloth melts when given heat is applied, it can be laminated without applying pressure to the electronic component 12. Hereinafter, a method for manufacturing such a multilayer printed circuit board 10 will be described.

Embodiment 1
3 to 6 are manufacturing process cross-sectional views illustrating a method for manufacturing a multilayer printed wiring board according to Embodiment 1. FIG. Here, of the manufacturing process of the multilayer printed circuit board 10, the process from the through hole 14 forming process to the process of mounting the lead component 16 will be described. Note that conventional manufacturing processes can be appropriately applied to other manufacturing processes of the multilayer printed board 10.

  As shown in FIG. 3, first, a through hole 14 penetrating the multilayer substrate 11 is formed in the multilayer substrate 11 in which the substrates 11 a to 11 c are stacked. The through hole 14 is formed in a region where the land portion 15 of each of the substrates 11a to 11c is provided.

  And the metal film which protruded toward the radial direction inner side of the said through hole 14 is formed in the land part 15 of the periphery of the through hole 14 by electroless plating. The metal film is formed in a direction perpendicular to the extending direction of the through hole 14. As a result, the thickness of the land portion 15 increases in a direction perpendicular to the extending direction of the through hole 14. For this reason, the diameter of the through hole 14 after the metal film is formed is smaller than that of the through hole 14 formed in the previous step.

  Thereafter, as shown in FIG. 4, the pin 20 having a diameter larger than the diameter of the through hole 14 after the metal film is formed is penetrated into the through hole 14. As a result, the metal film can be stretched by the pins 20 and plastically deformed so as to cover the inner peripheral surface of the through hole 14. The metal film only needs to be formed on the upper third substrate 11c and the second substrate 11b, and need not be formed on the first substrate 11a.

  FIG. 5 shows a state where the pin 20 is removed. As shown in FIG. 5, the deformed upper layer land portion 15 physically contacts the lower layer land portion 15. The metal film in the through hole 14 serves as a conductive portion that connects the circuit patterns of the substrates constituting the multilayer printed board 10.

  Thereafter, as shown in FIG. 6, the lead component 16 is soldered. In the soldering step, the thread solder 22 is melted using the soldering iron 21 on the surface of the multilayer substrate 11. The melted molten solder 23 spreads along the conductive portion and fills the through hole 14.

  Here, a comparative example in which the land portions 15 of the substrates 11a to 11c are separated will be described with reference to FIG. FIG. 9 shows a soldering process of the multilayer printed wiring board according to the comparative example. As shown in FIG. 9, when soldering is performed in the comparative example, the land portions 15 of the substrates 11a to 11c are separated from each other, so that heat is not transmitted to the lower first substrate 11a and second substrate 11b. For this reason, the molten solder 23 does not spread well in the through hole 14, and a defect may occur.

  On the other hand, in the first embodiment, the upper metal film is in physical contact with the lower land 15. For this reason, the heat conduction to the lower first substrate 11a and second substrate 11b is improved. As a result, it is possible to exhibit good solder wettability in the through hole 14 and improve the quality of the soldered product.

  In the above example, the metal film is formed by electroless plating, but the present invention is not limited to this. For example, it is possible to form a metal film on the land portion 15 by vapor deposition to increase the thickness of the land portion 15 in the radial direction of the through hole 14. In this case, after forming the through holes 14 in the second substrate 11b and the third substrate 11c, a metal film is formed by vapor deposition. Then, the first substrate 11a, the second substrate 11b, and the third substrate 11c are stacked to form the stacked substrate 11. Thereafter, the conductive portion can be formed by penetrating the pin 20 having a diameter larger than the diameter of the through hole 14 of the second substrate 11b and the third substrate 11c.

Embodiment 2
7 and 8 are manufacturing process cross-sectional views illustrating a method for manufacturing a multilayer printed wiring board according to the second embodiment. Here, of the manufacturing process of the multilayer printed circuit board 10, the process from the through hole 14 forming process to the process of forming the conductive portion will be described.

  As shown in FIG. 7, first, through holes 14 are formed in the land portions 15 of the first substrate 11a, the second substrate 11b, and the third substrate 11c. The through hole 14 is formed so as to penetrate the first substrate 11a disposed in the lowermost layer. On the other hand, in the 2nd board | substrate 11b and the 3rd board | substrate 11c arrange | positioned on the upper layer of the 1st board | substrate 11a, the through-hole 14 makes the copper foil 18 used as the circuit pattern formed in the upper surface of the 2nd board | substrate 11b and the 3rd board | substrate 11c. Do not penetrate. For this reason, the copper foil 18 remains on the upper surfaces of the second substrate 11b and the third substrate 11c.

  As shown in FIG. 7, the copper foil 18 has a larger area than the land portion 15 and is disposed so as to cover the land portion 15. Accordingly, the copper foil 18 becomes a metal film protruding from the peripheral edge of the through hole 14 toward the radially outer side of the through hole 14 on the second substrate 11b and the third substrate 11c. And each board | substrate 11a-11c is laminated | stacked through the prepreg 13, and it is set as the laminated substrate 11. FIG.

  Thereafter, as shown in FIG. 8, the pin 20 is passed through the through hole 14 from above the copper foil 18. As a result, the copper foil 18 is stretched by the pin 20 and plastically deformed so as to cover the inner peripheral surface of the through hole 14. The deformed upper copper foil 18 physically contacts the lower land 15. The copper foil 18 in the through hole 14 serves as a conductive portion that connects the circuit patterns of the substrates constituting the multilayer printed circuit board 10. Thereafter, as in the first embodiment, the lead component 16 is soldered.

  Thus, according to Embodiment 2, it becomes possible to connect each board | substrate 11a-11c with a highly conductive metal film. Thereby, the heat conduction to the lower first substrate 11a and the second substrate 11b is improved, and it is possible to develop good solder wettability in the through hole 14.

  Note that the present invention is not limited to the above-described embodiment, and can be changed as appropriate without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 10 Multilayer printed circuit board 11 Laminated board 11a 1st board | substrate 11b 2nd board | substrate 11c 3rd board | substrate 12 Electronic component 13 Prepreg 14 Through hole 15 Land part 16 Lead component 17 Lead pin 18 Copper foil 20 Pin 21 Soldering iron 22 Yarn solder 23 Molten solder

Claims (1)

Through holes are formed in the multilayer substrate,
Form a metal film protruding in the radial direction of the through hole on the periphery of the through hole,
By passing a pin through the through-hole, the metal film is plastically deformed so as to cover the inner peripheral surface of the through-hole, thereby forming a conduction portion.
Melting the solder on the surface of the laminated substrate, spreading the solder along the conductive portion, and filling the through holes;
A method for producing a multilayer printed wiring board.

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