JP2013098445A - Printed wiring board and induction heating cooker equipped with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printed wiring board which does not cause detachment of a copper plating layer 7 on an internal surface of a through hole 4a in a high-temperature soldering process, and provide an induction heating cooker equipped with the printed wiring board.SOLUTION: A printed wiring board comprises: a substrate 2 in which a through hole 5a is provided; and a plating layer 7 covering an internal wall of the through hole 5a and at least a part of a land part 6 provided on the substrate 2 connected to the internal wall, and having a boring on which a base material of the covered substrate is exposed. An induction heating cooker has the printed wiring board 1a.

Description

  The present invention relates to a printed wiring board, and more particularly to a printed wiring board having a through hole with excellent reliability and an induction heating cooker including the printed wiring board.

  The through hole of the printed wiring board is formed with a copper plating layer on the inner wall surface in order to make a through hole in the board having the front surface wiring and the back surface wiring, and to ensure conduction between the land of the front surface wiring and the land of the back surface wiring. It is a thing. A lead such as an electronic component is inserted into the through hole and filled with solder such as lead-free solder, and the electronic component is mounted on the printed wiring board.

  In this mounting process, a so-called flow soldering method is used in which a printed wiring board temporarily attached with electronic components or the like is passed through a solder tank containing heated and melted solder. In the flow soldering method, the lower surface of a printed wiring board is immersed in molten high-temperature solder, the solder is sucked into the through hole, and the solder is filled into the through hole.

  However, with this flow soldering method, the printed wiring board is exposed to high temperatures, so the copper plating layer on the inner wall surface of the through hole, the land of the through hole formed of copper foil on the surface of the printed wiring board, and the like peel off. there is a possibility. Therefore, the copper plating layer on the inner wall surface of the through hole is required to have high reliability for preventing peeling at a high temperature.

  Therefore, a step structure is formed on the inner wall surface of the through hole so that the copper plating layer on the inner wall surface of the through hole is not peeled off by being exposed to a high temperature such as when soldering by flow soldering method. A method for increasing the contact area of the copper plating layer and increasing the adhesion is proposed (for example, Patent Document 1).

JP 2010-258048 A

  However, in the conventional printed wiring board described above, when the printed wiring board is exposed to a high temperature during flow soldering, for example, from an organic-inorganic composite material made of glass fiber and epoxy resin, or a base material of a substrate such as a ceramic material. The gas such as water vapor and organic solvent that is released has a problem in that the adhesion between the base material of the substrate and the plating layer is reduced, and the plating layer is peeled off.

  The present invention has been made to solve the above-described problem, and is a printed wiring having a highly reliable through hole that can prevent peeling of a plating layer even when exposed to a high temperature during flow soldering or the like. An object is to obtain a plate and a dielectric heating cooker provided with the plate.

  The printed wiring board of the present invention covers a substrate provided with a through-hole, and an inner wall portion of the through-hole and at least a part of a land portion provided on the substrate connected to the inner wall portion. And a plating layer having perforations through which the substrate is exposed.

  When exposed to high temperatures during flow soldering, etc., the water vapor generated from the inside of the base material of the substrate constituting the printed wiring board, organic solvent gas, etc. from the perforations provided in the copper plating layer on the inner wall surface of the through hole Since it can be released, it is possible to prevent peeling of the plating layer without increasing the internal pressure at the interface between the base material of the substrate constituting the printed wiring board and the plating layer.

In the manufacturing process of the printed wiring board of Embodiment 1, it is a cross-sectional schematic diagram of the through hole before forming a perforation in the copper plating layer of the printed wiring board. In the manufacturing process of the printed wiring board of Embodiment 1, it is an upper surface schematic diagram of the through hole by which perforation was formed in the copper plating layer. In the manufacturing process of the printed wiring board of Embodiment 1, it is a cross-sectional schematic diagram of the through hole in which the perforation was formed in the copper plating layer. It is a cross-sectional schematic diagram of the through hole after performing flow soldering with respect to the printed wiring board of Embodiment 1. FIG. FIG. 5 is a schematic cross-sectional view of a through hole of a printed wiring board according to Embodiment 2 (a perforated portion is substantially circular). It is a cross-sectional schematic diagram of another through hole of the printed wiring board of Embodiment 2 (the perforated portion is elliptical).

  In the description of the embodiments and the respective drawings, the portions denoted by the same reference numerals indicate the same or corresponding portions.

Embodiment 1 FIG.
A manufacturing process and a configuration of a printed wiring board having a through hole will be described with reference to FIGS. FIG. 1 is a schematic cross-sectional view of a through hole before a perforation is formed in a copper plating layer of a printed wiring board in the manufacturing process of the printed wiring board. FIG. 2 is a manufacturing process of the printed wiring board 1a of the first embodiment. FIG. 3 is a schematic cross-sectional view of a through hole in which a perforation is formed in the copper plating layer in the manufacturing process of the printed wiring board 1a of the first embodiment. ing.

  In addition, in this Embodiment, the printed wiring board 1a used for an induction heating cooking appliance is demonstrated as an example. On the printed wiring board 1a used in the induction heating cooker, it is necessary to mount components such as an electrolytic capacitor required to pass a large current. In order to secure a large allowable current value at the mounting part of such a component, a large circular or oval (rounded rectangular) through hole is used. In the printed wiring board 1a of the present embodiment, as shown in FIG. 2, a case where the through hole 4a has an oval shape will be described as an example. However, depending on the mounting form such as arrangement with other components, etc. Needless to say, the shape of the through hole may be set.

  FIG. 1 is a schematic cross-sectional view of the through hole 4a of the printed wiring board 1a used in the induction heating cooker before the perforation is formed in the copper plating layer 7. FIG. First, an oval through hole 5a having a major axis of 5 mm and a minor axis of 1 mm and penetrating both sides is opened on a substrate 2 on which copper foils 3 to be printed wirings are formed on both sides using a punching method. The substrate 2 has a thickness of 1 mm, for example, and is made of an organic-inorganic composite material whose base material is made of glass fiber and epoxy resin. The cross-sectional schematic diagram of FIG. 1 shows a cross-sectional schematic diagram in the minor axis direction. Next, using an electroless copper plating method, a copper plating layer 7 is formed on the inner wall surface of the oval through hole 5a and the entire surface of the substrate 2 on the copper foil. Next, wiring patterns are formed on both surfaces of the substrate 2 using a photolithography method. A land portion 6 is formed as a part of the wiring pattern around the through hole 5a penetrating the substrate 2.

  Next, an ultraviolet curable solder resist is applied to the entire surface of the substrate 2 and pre-cured, and then unnecessary portions are removed using a photolithography method. As a result, the solder resist layer 8 is formed in the part not to be soldered, and the printed wiring board 1a having the oval through hole 4a is obtained. As described above, the through hole 4 a is configured by the through hole 5 a, the land portion 6, and the copper plating layer 7 that covers the inner wall surface of the through hole 5 a and the land portion 6.

  The substrate 2 provided with the oval through-holes 4a obtained by the steps so far is attached to a drill device capable of minute position adjustment. Next, as shown in FIG. 2, a substrate having a diameter of 0.3 mm is set by using a drill device as a center position 10 of the substrate perforation 9 at a position moved 0.1 mm from the inner wall surface of the through hole 4 a toward the outer side of the through hole 4 a. Perforations 9 are opened in a direction perpendicular to the printed wiring board 1a. The substrate perforations 9 are continuous perforations from the front surface to the back surface of the substrate 2.

  FIG. 2 is a schematic top view of an oval through hole 4a in which the substrate perforations 9 are opened. FIG. 3 is a schematic cross-sectional view taken along the line AA in FIG. As shown in FIGS. 2 and 3, the substrate perforation 9 has a structure continuously connected to the through hole 4a. Further, as shown in FIG. 3, the inner wall surface of the substrate perforation 9 has a section of the substrate exposed, in other words, an organic-inorganic composite material that is a base material of the substrate 2 is exposed. That is, the base material of the board | substrate 2 is exposed by forming the board | substrate perforation 9 continuous from the one surface of the board | substrate 2 to the other surface in the copper plating layer 7 of the inner wall face of the through hole 4a.

  FIG. 4 is a schematic cross-sectional view showing a state after soldering is performed on the printed wiring board 1a of the first embodiment. Using the printed wiring board 1a for an induction heating cooker having the oval through hole 4a obtained in the present embodiment, the lead 12 portion of the electrolytic capacitor is passed through the through hole 4a, and the lead-free solder bath at 255 ° C. The soldering is performed by dipping for 5 seconds and filling the through hole 4a with the solder 13.

  When a normal printed wiring board different from the printed wiring board 1a of the first embodiment is immersed in a high-temperature solder bath, water vapor and organic solvent gas are generated from the base material of the substrate 2 constituting the printed wiring board. The water vapor and gas are also generated from the inner wall surface of the through-hole 4a, accumulate between the base material of the substrate 2 and the copper plating layer 7, and the copper plating layer 7 swells.

  When the generated water vapor and gas are small, the bulge of the copper plating layer 7 is small and not a big problem. However, when the temperature of the solder bath is high and the generated water vapor and gas are large, the copper plating layer 7 swells greatly, and the substrate The copper plating layer 7 peels from the base material 2.

  Therefore, as in the present embodiment, the substrate perforation 9 is formed beside the through hole 4a, and the portion where the base material of the substrate 2 of the printed wiring board 1a is exposed is provided. It is discharged to the outside, and the copper plating layer 7 does not bulge and does not peel off.

  As schematically shown in FIG. 4, the printed wiring board 1a of the present embodiment can be soldered satisfactorily, and the copper plating layer 7 is peeled off from the inner wall surface of the through hole 4a even when exposed to high temperatures. Not good quality.

  In the present embodiment, the shape of the through hole 4a is oval. However, the shape of the through hole is not particularly limited, and is circular or elliptical depending on the shape of the lead 12 of the electronic component to be inserted and soldered. A through hole such as a rectangle can be used.

  In the present embodiment, the size of the through hole 4a is 1 mm short diameter and 5 mm long diameter, and the diameter of the substrate perforation 9 located beside the through hole 4a is 0.3 mm. The size of the through hole 4a and the substrate perforation 9 and the positional relationship thereof are positions where the substrate perforation 9 forms a perforation at least in the copper plating layer 7 on the inner wall surface of the through hole 4a and the base material of the substrate 2 is exposed. It is necessary that the through hole 4a and the substrate perforation 9 are not separated and separated. In other words, the center position 10 of the substrate perforation 9 needs to be a position that is not separated from the inner wall surface of the through hole 4a to the outside of the through hole 4a than the radius of the substrate perforation 9. The size of the through hole 4a and the substrate perforation 9 can be set in consideration of the size of the lead 12 of the electronic component to be mounted and the like within a range satisfying the positional relationship.

  In the present embodiment, one substrate perforation 9 is formed beside the through hole 4a, but the same effect can be obtained even if a plurality of substrate perforations 9 are formed. However, when the substrate perforation 9 is formed, the area of the copper plating layer 7 on the inner wall surface of the through hole 4a is reduced, and the electrical conductivity between the mounted electronic component and the wiring pattern formed on the printed wiring board 1 is not good. It will be enough. Therefore, it is necessary that at least 20% of the copper plating layer 7 on the inner wall surface of the through hole 4a remains due to the substrate perforation 9.

  Moreover, in this Embodiment, although the thickness of the board | substrate 2 was 1 mm, this thickness is not specifically limited, If it is the normal board | substrate 2, it can be used. For example, if the thickness is at least 0.2 mm or more and 5 mm or less, the same effect as this embodiment can be obtained.

Embodiment 2. FIG.
In the present embodiment, the same substrate 2 as in the first embodiment is used. Further, configurations, manufacturing processes, and the like that are not particularly limited use the same configurations and manufacturing processes as those in the first embodiment. In the present embodiment, a perforation is formed in the copper plating layer 7 on the inner wall surface of the through hole 4b. The perforation formed in the present embodiment is distinguished from the substrate perforation 9 in the first embodiment. Called 11a and 11b.

  The printed wiring boards 1b and 1c of the through holes 4b of the present embodiment will be described with reference to FIGS. FIG. 5 is a schematic cross-sectional view of the through hole 4b of the printed wiring board 1b of the second embodiment (the inner wall perforation 11a portion is substantially circular), and FIG. 6 is a cross-sectional view of the through hole 4b of the printed wiring board 1c of the second embodiment. It is a schematic diagram (the inner wall perforation 11b portion is elliptical).

  In the present embodiment, a case where a circular through hole 4b having a diameter of 3 mm is formed in the substrate 2 is described as an example. Next, the substrate 2 provided with the circular through-hole 4b is attached to a drilling device capable of minute position adjustment and capable of drilling from an oblique direction. Using a drill with a diameter of 0.2 mm, an inner wall perforation 11a is formed on the copper plating layer 7 on the inner wall surface of the through hole 4b of the printed wiring board at an angle of 30 ° from the vertical direction as shown in FIG.

  Five inner wall perforations 11a are formed so as to be substantially evenly distributed over the entire copper plating layer 7 on the inner wall surface of the through hole 4b so that the inner wall perforations 11a do not contact each other.

  Using the printed wiring board 1b having the through hole 4b obtained here, the lead 12 portion of the electronic component is passed through the through hole 4b and immersed in a lead-free solder bath at 255 ° C. for 5 seconds for soldering. When the printed wiring board 1b is immersed in a high-temperature solder bath, water vapor and organic solvent gas generated from the base material of the substrate 2 of the printed wiring board 1b are discharged to the outside through the inner wall perforations 11a of the copper plating layer 7, The copper plating layer 7 does not swell or peel off, and the printed wiring board 1b having good characteristics can be obtained.

  In the present embodiment, the drill is inserted into the through hole 4b at an angle of 30 ° from the vertical direction, and the inner wall perforation 11a is formed in the copper plating layer 7 on the inner wall surface. However, this angle is not particularly limited. Thus, any angle can be used as long as it does not damage the portion other than the portion where the inner wall perforation 11a of the copper plating layer 7 is formed.

  Further, in the present embodiment, five inner wall perforations 11a are formed in the copper plating layer 7. However, the number of inner wall perforations 11a is not particularly limited, and one or more inner wall perforations 11a may be used. Can be used. Furthermore, in the present embodiment, the inner wall perforations 11a are uniformly formed on the entire surface of the copper plating layer 7 so that the inner wall perforations 11a do not contact each other, but the distribution of the inner wall perforations 11a is particularly limited. Instead, the inner wall perforations 11a in contact with each other can achieve the object of the present invention.

  However, when the number of inner wall perforations 11a is too large, the area of the copper plating layer 7 is reduced, and the electrical conductivity between the lead 12 of the electronic component and the wiring pattern of the printed wiring board 1b becomes insufficient. It is necessary that at least 20% or more of the copper plating layer 7 on the inner wall surface remains.

  The shape of the inner wall perforation formed on the inner wall surface of the through hole 4b is not particularly limited, and may be an arbitrary shape such as the elliptical inner wall perforation 11b shown in FIG. 6 in addition to the substantially circular shape shown in FIG. be able to. In order to form the elliptical internal perforation 11b shown in FIG. 6 to obtain the printed wiring board 1c, for example, the drill may be perforated while changing the drill entry angle.

  In the present embodiment, the inner wall perforations 11a and 11b are formed by using a drill. However, the method of forming the inner wall perforations 11a and 11b is not limited to this, and the copper plating layer on the inner wall surface of the through hole 4b. 7 can be used as long as the inner wall perforations 11a and 11b can be formed. For example, in addition to a drill, a method using a laser processing machine can also be applied.

  Within the scope of the present invention, the present invention can be freely combined with each other, or can be appropriately modified or omitted.

  DESCRIPTION OF SYMBOLS 1a Printed wiring board, 1b Printed wiring board, 1c Printed wiring board, 2 Substrate, 3 Copper foil, 4a Through hole, 4b Through hole, 5a Through hole, 5b Through hole, 6 Land part, 7 Copper plating layer, 8 Solder resist Layer, 9 substrate drilling, 10 substrate drilling center position, 11a inner wall drilling, 11b inner wall drilling, 12 lead, 13 solder.

Claims (6)

A substrate provided with a through hole;
A plating layer having a perforation that covers an inner wall portion of the through-hole and at least a part of a land portion provided on the substrate connected to the inner wall portion and exposes the covered base material of the substrate; ,
A printed wiring board comprising: The printed wiring board according to claim 1, wherein the plated layer has perforations continuous from one surface of the substrate to the other surface. The printed wiring board according to claim 1, wherein the plated layer has a perforation at a position covering an inner wall portion of the through hole in the plated layer. The printed wiring board according to claim 1, wherein the substrate is provided with an oval through hole. The printed wiring board according to any one of claims 1 to 3, wherein the substrate is provided with a circular through hole.   An induction heating cooker comprising the printed wiring board according to any one of claims 1 to 5.

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