JP2008282916A - Printed circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printed circuit board on which solder is formed to protrude on a surface opposite to a surface on which flow soldering is carried out without carrying out reflow soldering so that the printed circuit board can be grounded to a metal plate via the solder. <P>SOLUTION: The metal plate 19 for grounding a ground pattern 12 of the printed circuit board 10 is disposed on the undersurface 21 of the printed circuit board 10 to which no electronic component is soldered. A mounting screw 18 is put through a hole 15 of the printed circuit board 10 and through a hole 23 of a metal plate 19 and is screwed into a mount body, which is not shown in a figure. As the mounting screw 18 is tightened, a protruding portion 17 of solder 16 formed by flow soldering on an upper surface 20 and protruding outward from the undersurface 21 is squeezed between the printed circuit board 10 and the metal plate 19 to crash. As a result, a contact area between the solder 16 and the metal plate 19 increases, so that the ground pattern 12 can be grounded certainly to the metal plate 19 via the solder 16. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a printed circuit board, and more particularly to a printed circuit board that is grounded using a surface that is not soldered.

  Conventionally, when a printed circuit board is connected to a metal plate such as a sheet metal frame to be grounded, an attachment screw portion for attaching the printed circuit board to an attached body is used. In order to improve the electrical connection between the ground pattern formed on the printed circuit board and the metal plate, solder protruding outward from the mounting surface of the printed circuit board is formed around the mounting screw on the ground pattern. . When the mounting screw is tightened, the solder portion is crushed and the ground pattern and the metal plate are securely grounded via the solder. This solder is formed together when an electronic component is mounted by flow soldering or reflow soldering. As a printed circuit board to be grounded via a mounting screw, one using reflow soldering is disclosed in Patent Document 1 and one using flow soldering is disclosed in Patent Document 2.

JP 2001-251029 A JP 2003-309333 A

  In the conventional printed circuit board as described above, when performing flow soldering of electronic components only on one surface and bringing the other surface and a metal plate into contact with each other via solder, It is necessary to perform reflow soldering to form the solder. However, it is uneconomical to perform reflow soldering on the other side even though there are no electronic components to solder.

  The present invention has been made to solve the above-mentioned problems, and without reflow soldering, a solder protruding on the surface opposite to the surface to be flow soldered is formed, and the solder is interposed therebetween. An object of the present invention is to provide a printed circuit board that can be grounded to a metal plate.

  In order to achieve the above object, according to the first aspect of the present invention, flow soldering of an electronic component is performed only on the first surface, a ground pattern is formed on the first surface side, and the opposite side to the first surface. A printed circuit board that contacts a grounded metal plate on the second surface side of the printed circuit board. The printed circuit board is electrically connected to the ground pattern and has a through hole that is not mounted with an electronic component. Solder is formed so as to protrude outward from the two surfaces.

  If comprised in this way, when the part in which the through-hole of the surface which does not solder is formed is made to contact a metal body in parallel mutually, the solder formed so that it may protrude first contacts.

  According to a second aspect of the present invention, in the configuration of the first aspect of the present invention, a hole for allowing a mounting screw to be fixed to the metal plate is further formed in the vicinity of the through hole.

  If comprised in this way, a mounting screw will be passed through the solder vicinity pinched | interposed into the printed circuit board and the metal plate.

  According to a third aspect of the present invention, in the configuration of the second aspect of the invention, the mounting screw is passed through the hole, and the mounting screw is tightened so that the solder sandwiched between the second surface and the metal plate is crushed. A printed circuit board is mounted on the mounted body.

  If comprised in this way, the contact area of a solder and a metal plate will expand.

  As described above, according to the first aspect of the present invention, when the portion where the through hole is formed on the surface where soldering is not performed is brought into contact with the metal body in parallel with each other, the solder formed so as to protrude first is provided. Since the contact is made, the ground pattern can be grounded to the metal body via the solder on the surface where the soldering is not performed.

  In addition to the effect of the invention described in claim 1, the invention described in claim 2 is such that the mounting screw is passed near the solder sandwiched between the printed circuit board and the metal plate. The ground pattern can be securely grounded to the metal body via the.

  According to the third aspect of the invention, in addition to the effect of the second aspect of the invention, since the contact area between the solder and the metal plate is expanded, the ground pattern can be more reliably grounded to the metal body via the solder.

  Next, embodiments of the invention will be described with reference to the drawings.

  FIG. 1 is a plan view showing a schematic configuration of a printed circuit board according to a first embodiment of the present invention, FIG. 2 is an enlarged view of a portion A shown in FIG. 1, and FIG. 3 is shown in FIG. It is a schematic sectional drawing of the III-III line.

  With reference to these drawings, the printed circuit board 10 has an upper surface 20 constituting a first surface and a lower surface 21 constituting a second surface. Also, electronic components are not mounted on the first surface, and leaded electronic components are mounted on the second surface. It should be noted that the electronic component with leads is not necessarily mounted on the second surface. The printed circuit board 10 has a rectangular shape in plan view, and ground patterns 12 each having a predetermined size and having a substantially square shape are formed at four corners of the upper surface 20. Each of the ground patterns 12 is formed with a circular hole 15 through which a mounting screw is passed. The hole 15 is for passing an attachment screw for fixing the printed circuit board 10 to a grounded metal plate or the like. A plurality of through holes 22, 22... Are formed through the printed circuit board 10 on the ground pattern 12 and around the hole 15. That is, the hole 15 is formed in the vicinity of the through holes 22. Lands 13, 13... Made of copper foil or the like are integrally formed on the inner wall surfaces of the through holes 22, 22... And the edges of the upper surface 20 and the lower surface 21 surrounding the through holes 22. Is formed. .. And the ground pattern 12 are connected. .. Are not mounted on the through holes 22, 22... Formed around the hole 15, and solder 16 is formed by flow soldering described later. The solder pattern 16 comes into contact with a grounded metal plate 19 such as a sheet metal frame disposed below the printed circuit board 10 indicated by a two-dot chain line in FIG. A portion surrounded by a two-dot chain line in FIG. 2 is a projected portion of the metal body 19 onto the lower surface 21 of the printed circuit board 10.

  Referring mainly to FIG. 3, the printed circuit board 10 includes a base material 11 impregnated with an insulating resin, and a ground pattern 12 made of a conductor such as copper foil formed on the upper surface of the base material 11. And a solder resist 14 formed on the upper surface of the ground pattern 12. The solder resist 14 is a synthetic resin film that covers the surface of the copper foil so that the solder 16 does not flow to places other than the lands 13. Is formed. On the other hand, the lands 13, 13... Are portions to which solder is to be supplied. In the printed circuit board 10, another pattern (not shown) is formed on the upper surface 20 side, and surface-mounted electronic components are not mounted on the lower surface 21. Therefore, flow soldering of electronic components is performed on the upper surface 20 side, and neither flow soldering nor reflow soldering is performed on the lower surface 21 side.

  Next, a state where flow soldering on the upper surface 20 side of the printed circuit board 10 is performed will be described.

  FIG. 4 is a diagram corresponding to FIG. 3, and is a schematic cross-sectional view showing a state where flow soldering is performed on the printed circuit board.

  Referring to FIG. 4, the flow soldering is actually performed from below, and the surface to be flow soldered is the lower surface, but the upper and lower surfaces are unified in relation to other drawings, so the upper surface 20 side is flow soldered. This will be described as a surface to be processed.

  Flow soldering is one of the industrial methods for soldering printed circuit boards in which electronic components are joined to a substrate using a solder jet. First, flux is applied to the entire upper surface 20 of the printed circuit board 10 in which electronic components (not shown) are appropriately arranged at predetermined positions. This flux application is performed in order to remove the natural oxide film and improve the wetting and spreading of the solder 16 on the surfaces of the lands 13. Next, the printed circuit board 10 is heated by a far infrared heater or the like. This is done to vaporize unnecessary solvent components of the applied flux and to mitigate thermal shock that occurs when the molten solder 16 comes into contact with the printed circuit board 10. Next, the molten solder 16 is supplied to the upper surface 20 of the printed circuit board 10. The supply of solder 16 consists of a primary jet and a secondary jet. The primary jet sufficiently wets the surface of the land 13 formed so as to cover the wall surfaces of the through holes 22, 22... With the solder 16, and the secondary jet removes the solder 16 attached to the solder resist 14 portion. Or adjusting the shape of the solder 16. At this time, the melted solder 16 supplied from the upper surface 20 side gets wet through the through holes 22, 22... From the upper surface 20 side toward the lower surface 21 by capillary action. And the mountain-shaped solder 16 which has protrusion part 17,17 ... which protruded outward from the lower surface 21 is formed. When the flow soldering is performed, the phenomenon in which the solder protrudes outward from the lower surface 21 in the through hole is limited to the through holes 22, 22... Formed at the four corners of the printed circuit board 10. This is not a phenomenon. For example, the phenomenon occurs in the same manner even in the case of a through hole formed in another part to which an electronic component is attached. In this way, flow soldering is performed.

  Next, a state where the ground pattern 12 of the printed circuit board 10 is grounded will be described.

  FIG. 5 is a diagram corresponding to FIG. 3 and is a schematic cross-sectional view showing a state in which the printed circuit board is attached to a metal plate.

  Referring to FIG. 5, the metal plate 19 for grounding the ground pattern 12 of the printed circuit board 10 is disposed on the lower surface 21 of the printed circuit board 10 to which no electronic component is soldered. The metal plate 19 is held at the same potential as the ground. The mounting screw 18 is passed through the hole 15 of the printed circuit board 10 and the hole 23 of the metal plate 19, and is screwed into a body to be mounted such as a nut. As the mounting screw 18 is tightened, the protrusion 17 of the solder 16 formed by the above-described soldering first comes into contact with the metal plate 19 and is sandwiched between the lower surface 21 of the printed circuit board 11 and the upper surface of the metal plate 19. To be crushed. In this way, the printed circuit board 10 is fixed to the metal plate 19. Here, the ground pattern 12, the lands 13, 13,..., The solder 16, and the metal plate 19 are electrically connected to each other. Further, since the solder 16 is crushed as described above, the contact area between the solder 16 and the metal plate 19 is increased. Therefore, the ground pattern 12 can be reliably grounded to the metal plate 19 via the solder 16.

  In the printed circuit board 10 as described above, the solder 16 protruding outward from the lower surface 21 is formed by the flow soldering of the upper surface 20, and therefore, the ground pattern 12 is connected to the metal body 19 through the solder 16. Can be grounded well. Although there is no electronic component to be mounted, there is no need to provide a soldering process on the lower surface 21, which is economical.

  In the above embodiment, the printed circuit board has a rectangular shape, but may have another shape as long as it can be brought into contact with the metal plate.

  Further, in the above embodiment, the ground pattern has a substantially square shape and is formed at each of the four corners of the printed circuit board, but may have other shapes and numbers depending on the position of the metal plate to be contacted. .

  Further, in the above-described embodiment, a plurality of through holes are formed in one mounting screw portion. However, only one may be used as long as the ground pattern and the metal plate can be conducted through solder.

  Furthermore, in the above embodiment, the holes for passing the mounting screws are formed at the four corners of the printed circuit board, respectively, but if the printed circuit board can be attached to the mounted body, the positions and numbers may be different. May be.

It is the top view which showed schematic structure of the printed circuit board by 1st Embodiment of this invention. It is an enlarged view of A part shown in FIG. It is a schematic sectional drawing of the III-III line shown in FIG. FIG. 4 is a schematic cross-sectional view corresponding to FIG. 3 and showing a state where flow soldering is performed on the printed circuit board. FIG. 4 is a schematic cross-sectional view corresponding to FIG. 3 and showing a state where a printed circuit board is attached to a metal plate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Printed circuit board 12 Ground pattern 15 Hole 16 Solder 18 Mounting screw 19 Metal plate 22 Through hole

Claims (3)

A metal plate in which flow soldering of an electronic component is performed only on the first surface side, a ground pattern is formed on the first surface side, and a second surface side opposite to the first surface is grounded; A printed circuit board to be contacted,
A through hole that is electrically connected to the ground pattern and does not mount the electronic component is formed,
A printed circuit board on which solder is formed so as to protrude outward from the second surface through the through hole by the flow soldering.   The printed circuit board according to claim 1, wherein a hole for passing an attachment screw for fixing to the metal plate is further formed in the vicinity of the through hole.   3. The printing according to claim 2, wherein an attachment screw is passed through the hole, and the attachment screw is tightened to attach the solder sandwiched between the second surface and the metal plate to the attached body. Circuit board.

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