JP2019067788A - Heat dissipating metal piece material for printed wiring board and manufacturing method of printed wiring board using the same - Google Patents

Abstract

To provide a printed wiring board and a manufacturing method thereof in which no crack occurs in an insulating substrate or an electronic component is not inclined when the electronic component is mounted even in the case of adopting a press-in method as means for disposing and fixing a metal piece in a metal piece accommodation hole.SOLUTION: There are provided a heat dissipating metal piece material for a printed wiring board including a cylindrical body having a plurality of projections on the outer peripheral wall and a manufacturing method for a printed wiring board using the same.SELECTED DRAWING: Figure 1

Description

  INDUSTRIAL APPLICABILITY The present invention is used for a printed wiring board which transfers heat generated from an electronic component to a heat radiating body disposed on the side opposite to the electronic component mounting side surface by a metal piece disposed immediately below the electronic component. The present invention relates to a heat dissipating metal piece material and a method of manufacturing a printed wiring board using the heat dissipating metal piece material.

  As a means to efficiently dissipate the heat generated from electronic components (for example, surface mount electronic components that generate a large amount of heat such as “FET” and “MOSFET”) to the outside, directly under the electronic components mounted on the printed wiring board Conventionally, a method of providing a plurality of thermal vias consisting of through plating through holes and radiating the heat to the outside through a heat dissipating member (a heat dissipating pattern or a heat sink) disposed on the back side of the printed wiring board is generally used conventionally. It has

However, as the heat generation from electronic parts has become much larger than conventional products due to the advancement of higher functionality and higher performance of equipment, thermal vias consisting of through plating through holes are processed It has become impossible (i.e., it has become impossible to carry out the heat dissipation process to operate the electronic components properly).
Therefore, in recent years, means for embedding a metal piece having a large heat capacity (for example, “copper piece”) in place of the thermal via has been studied and reported (for example, see Patent Document 1).

Using the schematic cross-sectional process drawing shown in FIG. 6 for the production example of the printed wiring board in which the “metal piece” is embedded (here, the production example for “intermediate substrate pw2” at the stage before forming the wiring pattern) Explain.
As shown in FIG. 6A, first, the conductor layer 2c is formed on the electronic component mounting side surface A and the heat radiating body arrangement side surface B, and the metal piece accommodation hole 3 for arranging and fixing the metal piece 55 later is The formed insulating substrate 1 is prepared, and then the insulating substrate 1 is placed on the jig 14. Thereafter, a cylindrical metal piece material 55 a having a diameter longer than the height H of the metal piece accommodation hole 3 and shorter than the hole diameter D of the metal piece accommodation hole 3 is inserted into the metal piece accommodation hole 3. insert.

  Next, a load is applied to the electronic component connection side exposed surface 66a of the metal piece material 55a protruding from the metal piece accommodation hole 3 with the press pin 15, and the metal piece material 55a is plastically deformed, as shown in FIG. An intermediate substrate pw2 in which the metal pieces 55 shown in FIG. 2 are disposed and fixed in the metal piece receiving hole 3 is obtained. In addition, the code | symbol 77a shown in the figure shows the thermal radiation body connection side exposed surface of the metal piece raw material 55a. The metal piece 55 disposed and fixed in the metal piece accommodation hole 3 is connected to the electronic component through the normal solder on the electronic component connection side exposed surface 66 and the thermally conductive resin on the heat radiator connection side exposed surface 77 It is connected to the heat sink via

By the way, the above-mentioned method of arranging and fixing the metal piece 55 in the metal piece accommodation hole 3 by plastically deforming the metal piece material 55a is called “press-in method” in the printed wiring board industry and is widely adopted. It is a method of construction. By pressing in the metal piece 55, the metal piece 55 spreads in the horizontal direction with respect to the metal piece accommodation hole 3, and the metal piece 55 is fitted and fixed to the metal piece accommodation hole 3 in order to push and spread the metal piece accommodation hole 3. Ru.
However, as shown in FIG. 7, plastic deformation of the metal piece material 55a is deformed into a so-called “barrel shape” in which the central portion C of the metal piece 55 (one-dot chain line in FIG. 7) bulges in the direction of arrow a. Therefore, there is a problem that the crack 16 (see FIG. 6B) is easily generated in the insulating substrate 1.

  In addition, the metal piece 55 is such that the electronic component connection side exposed surface 66 on the side loaded with the press pin 15 can not be completely filled in most cases and protrudes from the metal piece accommodation hole 3 and tilts when mounting the electronic component It is known that there is a problem. Usually, when the protrusion amount from the metal accommodation hole 3 of the electronic component connection side exposed surface 66 of the metal piece 55 exceeds 50 micrometers, it will become an obstruction for electronic component mounting. The reason why the protrusion of the electronic component connection side exposed surface of the metal piece becomes large is because the hole diameter of the metal piece accommodation hole and the plate thickness variation of the insulating substrate are large, for example, about 50 μm in hole diameter and about 100 μm in plate thickness. The volume in the metal piece receiving hole may be easily changed. Therefore, a difference between the volume of the metal piece and the volume in the metal piece receiving hole is likely to occur. The volume of one of the metal pieces is very stable because both the diameter and the thickness have a processing accuracy of 30 μm or less.

  In the conventional cylindrical metal piece material 55a shown in FIG. 6, the metal piece 55 is in surface contact circumferentially with the inner wall of the metal piece accommodation hole 3 when pressed in, so the metal piece accommodation hole 3 It was not possible to absorb the variation of the internal volume, and it was not possible to control the protrusion of the metal piece 55 from the metal piece accommodation hole 3 and the generation of the crack in the insulating substrate 1.

  Furthermore, when the metal piece 55 is embedded in the metal piece accommodation hole 3, the electronic component connection side exposed surface 66 and the heat sink connection side exposed surface 77 of the metal piece 55 disposed and fixed in the metal piece accommodation hole 3 are metal piece accommodation holes Although it becomes a substantially flat surface with the outer surface 22 of the conductor layer 2c around 3 but a substantially flat surface, the print after embedding the metal piece 55 due to the lack of hold in the metal piece accommodation hole 3 There is also a concern that metal pieces may fall during the manufacturing process of the wiring board or when mounting the electronic component.

JP, 2010-263003, A

  The present invention has been made in view of the conventional problems and actual conditions as described above, and the crack in the insulating substrate is obtained even when the "press-in method" is adopted as a means for arranging and fixing the metal piece in the metal piece receiving hole. It is an object of the present invention to provide a method of manufacturing a printed wiring board in which the electronic component does not tilt when the electronic component is mounted.

  The inventor of the present invention has conducted various studies to solve the above problems, and as a result, using a metal piece material consisting of a cylindrical body having a plurality of protrusions on the outer peripheral wall, this is used as a metal piece storage hole The present invention has been completed by finding that the placement and fixation within the interior gives extremely good results.

  That is, the present invention solves the above-mentioned subject by the heat dissipation metal piece material for printed wiring boards which consists of a cylindrical object which has a plurality of projection parts in the perimeter wall.

  Further, according to the present invention, there is provided a printed wiring board which transfers heat generated from an electronic component to a heat radiating body disposed on the side opposite to the electronic component mounting side surface by a metal piece disposed immediately below the electronic component. At least a step of forming a metal piece accommodation hole in an insulating substrate, a length higher than the height of the metal piece accommodation hole, and a diameter shorter than the hole diameter of the metal piece accommodation hole Inserting a metal piece material consisting of a cylindrical body having a plurality of projections into the metal piece accommodation hole, applying a load to the electronic component connection side exposed surface of the metal piece material, and plastically deformed by the load And a step of disposing and fixing the metal piece in the metal piece accommodation hole. The method for manufacturing a printed wiring board according to the present invention solves the above-mentioned problems.

  According to the present invention, since a metal piece material consisting of a cylindrical body having a plurality of projections on the outer peripheral wall is used, the "press-fit method" is used as a means for arranging and fixing metal pieces in metal piece accommodation holes penetrating the insulating substrate. Even in the case where the metal piece material is plastically deformed, the deformed portion can be released to the recess between the protrusions which is a gap with the inner wall of the metal piece accommodation hole, so that a crack occurs in the insulating substrate, It can prevent that a metal piece protrudes beyond 50 micrometers from a metal piece accommodation hole. In addition, the metal piece can be held with appropriate strength in the metal piece accommodation hole. Therefore, it is possible to obtain a printed wiring board which has no influence on the mounting of the electronic component and has no concern of dropping of the metal piece.

The principal part enlarged plan view of the heat dissipation metal piece material of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS The schematic sectional drawing of the printed circuit board using this invention printed wiring board. (A)-(b) is a general | schematic cross-section process drawing which shows the manufacture example of this invention printed wiring board. (C)-(e) is a schematic sectional process drawing following FIG. (F)-(g) are the schematic cross-section process drawing following FIG. BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic cross-section process drawing for demonstrating the manufacture example of the printed wiring board (intermediate substrate) by the conventional "press-fit system", (a) is a schematic cross section which showed the state which inserted the metal piece raw material in the metal piece accommodation hole. The figure, (b), the schematic sectional view which showed the state which arranged and fixed the metal piece which made the metal piece raw material plastically deformed in the metal piece accommodation hole. The principal part expanded sectional view of the metal piece arrange | positioned and fixed in the metal piece accommodation hole by a "press-fit system."

In FIG. 1, 5 a is a heat dissipating metal piece material, and is formed of a cylindrical body having a plurality of protrusions 10 on the outer peripheral wall.
The number and size of the protrusions 10 on the outer peripheral wall are not particularly limited, but as shown in FIG. 1, the exposed surface 6 a of the metal piece material 5 a from the exposed surface 6 a of the metal piece material 5 a It is preferable that it is a convex line portion in the direction of Moreover, it is preferable to be provided at equal intervals on the outer peripheral wall.
The heat dissipation metal piece material 5a has a length (for example, 1.1 to 1.8 mm) higher than the height H of the metal piece accommodation hole in which it is embedded in a plastically deformed metal piece state and a hole diameter D of the metal piece accommodation hole It has a short diameter (for example, 4.7 to 5.7 mm). In addition, the diameter of the metal piece raw material 5a is a diameter including the projection part 10 of an outer peripheral wall.
Such heat-dissipating metal piece material 5a can be prepared by a header method for manufacturing a desired shape and size by cutting a metal rod such as copper to a required volume and pressing it into a mold. it can.

Subsequently, an embodiment of a printed wiring board using the above-mentioned heat radiating metal piece material 5a of the present invention will be described with reference to FIG. For convenience of explanation, the description will be made with the one before the placement and fixing of the metal piece in the metal piece accommodation hole as the "insulating substrate" and the one after the placement and fixing as the "printed wiring board".
Further, in the description of placing and fixing the metal piece in the metal piece accommodation hole, the terms "electronic component mounting surface side open end" and "heat radiating body disposed surface side open end" appear. The "edge" does not mean only the open end of the "metal piece accommodation hole" provided in the "insulation substrate", and for example, the "outer layer wiring pattern 2" and the "solder resist 12" shown in FIG. When it exists between the open end of the "metal piece accommodation hole 3" and the "electronic component 17" or the "heat radiator 20", it is formed by the "outer layer wiring pattern 2" or the "solder resist 12" Means open end. In the case where the “outer layer wiring pattern 2” or the “solder resist 12” does not exist between the opening end of the “metal piece accommodation hole 3” and the “electronic component 17” or the “heat radiator 20”, the “opening "The end" is an open end of the "metal piece accommodation hole" provided in the "insulating substrate".

  In FIG. 2, PW is a printed wiring board, and the insulating substrate 1 in which the wiring pattern 2 is formed on the electronic component mounting side surface A and the heat radiating body arrangement side surface B, the insulating substrate 1 is penetrated, and the electronic component 17 is Protect the metal piece accommodation hole 3 formed at the position immediately below the mounting, the metal piece 5 disposed and fixed in the metal piece accommodation hole 3, and the wiring pattern 2 formed excluding a part of the area And a solder resist 12 for the purpose.

  Although the electronic component mounting side surface A and the heat sink arrangement side surface B are described in the above description, the printed wiring board may be interchanged as the electronic component mounting side surface B and the heat sink arrangement side surface A.

In the printed wiring board PW, the upper surface of the metal piece 5 disposed and fixed in the metal piece accommodation hole 3, that is, the electronic component connection side exposed surface 6 is an open end of the metal piece accommodation hole 3 on the electronic component mounting surface side. It is located at a height within 50 μm from position 8A. In FIG. 2, the position 8 A of the opening end on the electronic component mounting surface side is the position of the outer surface 22 of the wiring pattern 2 formed on the electronic component mounting side surface A in the insulating substrate 1. The side exposed surface 6 and the outer surface 22 of the wiring pattern 2 are in a substantially flush position. If the exposed surface 6 on the electronic component connection side of the metal piece 5 is positioned at a height within 50 μm from the position 8A of the open end on the electronic component mounting surface side of the metal piece accommodation hole 3, the electronic component 17 is mounted when the electronic component 17 is mounted. It is possible to prevent tilting.
On the other hand, the lower surface of the metal piece 5, that is, the exposed surface 7 on the heat sink connection side is substantially flush with the outer surface 22 of the wiring pattern 2 formed on the heat sink disposition side surface B of the insulating substrate 1.

  Further, the metal piece 5 is disposed and fixed in the metal piece accommodation hole 3 with a holding force of 30 N or more. The holding power of the metal piece, also called punch strength, can be measured by a universal tester. When the metal piece 5 is pressed into the metal piece accommodation hole 3, the plastic deformation portion spreads in the recess between the protrusions 10 of the heat dissipating metal piece material 5 a, and the stress is dispersed to push the metal piece accommodation hole 3 apart. The metal piece 5 is disposed and fixed in the metal piece receiving hole 3 with a high holding force. If the holding power of the metal piece 5 in the metal piece accommodation hole 3 is 30 N or more, metal is produced during the manufacturing process of the printed wiring board or when processing with a board having a plurality of printed wiring boards faced, especially when mounting electronic components. There is no concern that the pieces will loosen, rattle, or fall.

  Then, the electronic component 17 is mounted on the electronic component mounting side surface A of the printed wiring board PW via the solder 19, and the radiator 20 is arranged on the radiator arrangement side surface B via the thermally conductive resin 21. A printed circuit board PC is configured. In FIG. 2, reference numeral 18 denotes a terminal drawn from the electronic component 17 and connected to the mounting pad 2 a via the solder 19.

  Subsequently, a method of manufacturing the printed wiring board PW will be described with reference to FIGS. 3 and 4.

  First, as shown in FIG. 3A, the insulating substrate 1 in which the metal foil 2b is laminated on the front and back surfaces is prepared, and a desired position of the insulating substrate 1 is drilled, punched, laser processed, etc. The metal piece accommodation hole 3 (for example, the cutting diameter is φ 5.0 to 6.0 mm) shown in 3 (b) is perforated.

As a material of the insulating substrate 1, a material obtained by impregnating a reinforcing fiber such as glass cloth generally used with a thermosetting resin such as an epoxy resin can be preferably used in view of heat resistance, versatility and cost. Moreover, as a metal foil, a common copper foil can be preferably used in terms of conductivity, processability, and cost.
With regard to the thickness of the insulating substrate 1, although the thickness can not be generally shown, the overall thickness is, for example, about 1.0 to 1.6 mm, regardless of whether it is a single layer or a multilayer. . Moreover, regarding the thickness of metal foil, a thing about 18-35 micrometers is generally used.

  Next, as shown in FIG. 4C, the insulating substrate 1 in which the metal piece accommodation hole 3 is formed is subjected to electroless plating (for example, electroless copper plating) and electrolytic plating (for example, By sequentially performing electrolytic copper plating treatment, a plating film 4 (for example, a copper plating film having a thickness of about 25 μm) is deposited on the entire insulating substrate 1 including the metal piece accommodation holes 3.

  Subsequently, the annealed metal piece material 5a is prepared. The metal piece material 5a has a length higher than the height H of the metal piece accommodation hole 3 and a diameter shorter than the hole diameter D of the metal piece accommodation hole 3 as shown in FIG. It consists of a cylindrical body which has the projection part 10 of this.

Next, although it is a process of arranging metal piece material 5a in metal piece accommodation hole 3, it can carry out by a "press fit method". That is, after the insulating substrate 1 on which the plating film 4 is deposited is placed on the jig 14, the metal piece material 5a is inserted into the metal piece accommodation hole 3 (see FIG. 4D), and then the metal A load is applied to the electronic component connection side exposed surface 6a of the piece material 5a with the press pin 15, and the metal piece material 5a is plastically deformed to form the metal piece 5 in the metal piece accommodation hole 3 shown in FIG. To obtain an intermediate substrate pw1 on which the arrangement is fixed.
The diameters on the electronic component connection side exposed surface 6 side and the heat sink connection side exposed surface 7 side of the metal piece after press-fitting are the same spread (diameter) as the hole diameter.

In the present invention, even in the case of adopting the "press-in method", since a deformed portion when the metal piece material 5a is plastically deformed can be released to the concave portion between the protrusions 10, as shown in FIG. The stress in the arrow a direction concentrated in the vicinity of the central portion of the insulating substrate 1 can be dispersed in the arrows b and c. As a result, the occurrence of the crack 16 (see FIG. 6B) in the insulating substrate 1 can be suppressed.
Further, since the concave portions between the protrusions 10 absorb the deformed portion when the metal piece material 5 a is plastically deformed, the electronic component connection side exposed surface 6 of the metal piece 5 is the electronic component mounting surface side opening of the metal piece accommodation hole 3 The metal piece 5 can be embedded in the metal piece receiving hole 3 so as to be positioned at a height within 50 μm from the end position 8A, and the electronic component 17 can be prevented from being inclined when the electronic component 17 is mounted. it can. In addition, since the metal piece accommodation hole 3 is appropriately spread by dispersion of stress and the holding force of the metal piece 5 in the metal piece accommodation hole 3 becomes high as 30 N or more, the manufacturing process of the printed wiring board or the printed wiring board When processing with a board having a plurality of faces, particularly when mounting electronic components, the metal pieces can be prevented from loosening, rattling and falling.
When the projection 10 on the outer peripheral wall is a ridge in the vertical direction, when the metal piece 5 is press-fitted into the metal piece accommodation hole 3, the projection 10 corresponds to the inner wall 3 a of the metal piece accommodation hole 3. Because of the line contact, the pressure for disposing and fixing the metal piece 5 may be smaller than in the prior art.

Further, in the present invention, the thickness variation of the insulating substrate 1 is measured in advance at several places in the substrate surface, and the volume of the metal piece material 5a is formed into the thickest portion. Although the degree of absorption of the plastically deformed portion of the metal piece material 5a at the recesses between the protrusions 10 differs if the volume is made close to the volume in 3, it is easy regardless of the thick and thin portions. In addition, the metal piece 5 can be arranged and fixed so that the electronic component connection side exposed surface 6 of the metal piece 5 has a protrusion amount in a range that does not affect the mounting of the electronic component 17.
Furthermore, if the volume in all the metal piece accommodation holes 3 formed in the insulating substrate 1 is measured and the metal piece material 5a of the volume according to the volume is inserted, the volume of the metal piece and the metal piece accommodation Since the difference in volume in the hole is small, the accuracy is high (for example, the metal piece 5 is dropped due to the lack of hold in the metal piece accommodation hole 3 or the area reduction of the electronic component connection side exposed surface 6 of the metal piece 5). Printed wiring board).

  Next, the jig 14 is removed, and the conductor layer 2c laminated on the electronic component mounting side surface A and the heat radiating body arrangement side surface B of the insulating substrate 1 is exposed to the well-known photoetching process (photosensitive etching resist film on the conductor layer) Is laminated, and an etching resist pattern is formed by exposure and development processing, and then the conductor layer exposed from the etching resist pattern is removed by etching processing, as shown in FIG. Mounting pads on the electronic component mounting side surface A and the heat radiating body arrangement side surface B of the insulating substrate 1 by applying the wiring pattern forming method of forming a desired wiring pattern by peeling off the etching resist pattern A solder resist for forming a wiring pattern 2 including 2a and then protecting the wiring pattern 2 Printed wiring board PW in which metal piece 5 is arranged and fixed in metal piece accommodation hole 3 shown in FIG. 5 (g) by forming 2 in a form in which a part of wiring pattern 2 and mounting pad 2a are exposed. Get

  Although the present invention has been described using the form of a double-sided printed wiring board in which a conductor layer (a layer to be the wiring pattern 2 later) is formed on the front and back surfaces of a single-layer insulating substrate 1, the insulating substrate The present invention can also be used in the form of a single-sided printed wiring board in which a conductor layer is provided only on one side of 1 or a multilayer printed wiring board in which a plurality of insulating substrates 1 and conductor layers are alternately stacked. Although the plating film 4 is formed on the inner wall of the metal piece housing hole 3 as described above, the plating film may not be provided as in the configuration of the prior art shown in FIG. It is.

1: Insulating substrate 2: Wiring pattern 2a: Mounting pad 2b: Metal foil 2c: Conductor layer 22: Outer surface 3: Metal piece accommodation hole 3a: Metal piece accommodation hole inner wall 4: Plating film 5, 55: Metal piece 5a, 55a: metal piece material 6, 6a, 66, 66a: electronic component connection side exposed surface 7, 7a, 77, 77a: heat sink connection side exposed surface 8A: electronic component mounting surface side open end position 8B: heat sink arrangement surface Side open end position 10: protrusion 12: solder resist 14: jig 15: press pin 16: crack 17: electronic component (heat generation component)
18: terminal 19: solder 20: heat sink 21: heat conductive resin A: electronic component mounting side surface B: heat sink disposed side surface C: central portion of metal piece PW: printed wiring board pw1, pw2: intermediate board PC: printed circuit substrate

Claims (7)

  What is claimed is: 1. A heat dissipating metal piece material for a printed wiring board, comprising: a cylindrical body having a plurality of protrusions on an outer peripheral wall.   The heat dissipation metal piece material for a printed wiring board according to claim 1, wherein the projection is a ridge in the longitudinal direction.   The heat dissipation metal piece material for a printed wiring board according to claim 1 or 2, wherein the protrusions are provided on the outer peripheral wall at equal intervals.   The printed wiring board characterized by the metal piece raw material of any one of Claims 1-3 being embed | buried in the metal piece accommodation hole in the metal piece state by which plastic deformation was carried out.   A method of manufacturing a printed wiring board, which transfers heat generated from an electronic component to a heat radiating body disposed on the side opposite to the side surface on which the electronic component is mounted, by a metal piece disposed directly below the electronic component, At least a step of forming a metal piece receiving hole in the insulating substrate, a length higher than the height of the metal piece receiving hole, and a diameter shorter than the hole diameter of the metal piece receiving hole, and a plurality of protrusions on the outer peripheral wall And inserting a load into the exposed surface on the electronic component connection side of the metal piece material, and storing the metal piece plastically deformed by the load. And a step of disposing and fixing in the hole.   The method of manufacturing a printed wiring board according to claim 5, wherein the projection is a ridge in the longitudinal direction.   7. The method for manufacturing a printed wiring board according to claim 5, wherein the projections are provided on the outer peripheral wall at equal intervals.