JP2007134407A - Circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a substrate structure where a screw and ground of a substrate screw stop are securely conducted in a substrate fixing part, and slack of the screw is prevented. <P>SOLUTION: Solder piling up 7a is made on a ground pattern 3 at a periphery of a fitting hole for substrate fixing screw insertion 6 by cream solder printing, and a through-hole 2 is formed below it. Since solder flows into the through-hole 2, the screw stop becomes flat at the time of reflow, and the ground pattern 3 on the substrate is securely conducted by bringing the screw 1 into contact with solder at the time of screw stop, and a stable circuit operation is provided. Since the screw stop does not swell by solder, a larger contact area of the substrate 5 and the screw 1 is provided, and slack of the screw 1 is prevented. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a circuit board structure for preventing grounding of a circuit board fixing portion and loosening of screws.

  A circuit board of an electronic device is manufactured by being laminated through a process such as plating or etching on a board having a copper foil in close contact with the surface. Each layer of the substrates is connected by a through hole in which a conductor film is formed by plating inside the hole. The manufactured substrate has a resist opening in the component mounting portion, but in order to prevent oxidation of the copper foil in the opening, the copper foil exposed portion is subjected to solder plating, gold plating, or heat-resistant preflux surface treatment. For component mounting, a method is used in which cream solder paste is printed on a soldering portion, a necessary amount of solder is supplied in advance, and then soldered by heating and melting it with a heat source.

The board on which the electronic component is mounted in this manner is fixed to the casing of the electronic device with screws. The structure of the conventional mounting part is shown in FIG. A substrate fixing hole 6 for screwing is provided in the substrate 5, and a ground pattern 3 of a circuit board is formed around the substrate fixing hole. The case 4 to be fixed is made of metal, and the substrate and the electronic device case have the same potential via screws by screwing.
JP 2001-251029

  However, there is an insulator on the surface of the copper foil of the substrate that has been prefluxed as a surface treatment, and when the screw is tightened as it is, a part of the insulator is scraped off by the screw, but it is completely removed. Therefore, the contact between the screw and the ground pattern may be insufficient. In view of this, there has been proposed a method of depositing solder on the screw fixing portion. (For example, refer to Patent Document 1) However, in this method, when the solder cannot be sufficiently crushed during screw tightening, the contact area between the screw and the solder pile is reduced, and further, if the electronic device is subjected to vibration or shock after mounting the board, There is a possibility that the solder will be crushed and a gap will be formed between the board and the screw head, and the screw will loosen. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to propose a substrate structure that reliably connects a screw and a ground of a substrate screw fixing portion at a substrate fixing portion and prevents loosening of the screw.

  According to the first aspect of the present invention, the fixing portion that requires electrical grounding of the circuit board has a ground pattern around the mounting hole of the circuit board into which the board fixing screw is inserted. A plurality of holes are provided, a resist opening is formed on the through hole, and a solder pile is formed on the resist opening.

  The invention according to claim 2 of the present invention is characterized in that a solder pile on the through hole is arranged at a position where it can come into contact with the board fixing screw.

  The invention according to claim 3 of the present invention is characterized in that a resist opening diameter of the through hole portion is larger than a hole diameter of the through hole.

  The invention according to claim 4 of the present invention is characterized in that a plurality of the through holes are arranged at equal intervals in the circumferential direction on the outer periphery of the mounting hole.

  The invention according to claim 5 of the present invention is characterized in that the positions of the through hole and the solder pile on the circuit board are the same coordinates.

  According to the sixth aspect of the present invention, the through hole is formed as a through through hole or SVH (surface via hole).

  The invention according to claim 7 of the present invention is characterized in that the solder piles are provided on both the component surface and the solder surface.

  Soldering by cream solder printing is performed on the ground pattern around the mounting hole for inserting the board fixing screw. A through hole is provided below it. Solder flows into the through hole during reflow and the screw stopper becomes flat. When the screw is screwed, the screw and the solder contact each other, so that the screw and the ground pattern on the board can be reliably connected to obtain stable circuit operation. Can do. Further, since the screw fixing portion is not raised by the solder, a large contact area between the substrate and the screw can be obtained, and the screw can be prevented from loosening.

  Next, details of the present invention will be described in accordance with the description of the embodiments.

  FIG. 1 is a cross-sectional perspective view of a circuit board according to the present invention. As shown in FIG. 1, 1 is a board fixing screw, 2 is a through hole, 3 is a ground pattern, 4 is an electronic device casing to which the board is attached, 5 is a circuit board, and 6 is a board for screwing. Reference numeral 7a denotes a solder pile on the side in contact with the screw head, 7b a solder pile on the side in contact with the housing 4, 8 a resist on the substrate surface, and 9 a ground layer inside the circuit board. A ground pattern 3 of the circuit board 5 is formed around the board mounting hole 6. The holes 6 for screw insertion are not plated on the side surfaces. The exposed portion of the ground pattern 3 is prefluxed. A through hole 2 is formed on the ground pattern 3. The through hole 2 has a conductor film formed on the inner wall and is connected to the ground layer of the circuit board. As shown in FIG. 2, a plurality of through holes 2 are arranged at equal intervals in the circumferential direction of the screw mounting holes 6, and the resist openings in the hole portions of the through holes 2 are set larger than the hole diameter of the through holes 2. Yes. The through hole 2 is also provided on the housing 4 side.

  The solder piles 7a and 7b are performed by a cream solder printing process. A printing plate opening is provided at a location corresponding to the through hole 2. A printing plate on which a cream solder paste is placed is overlaid on the circuit board 5, the spatula is moved while pressing the solder paste with a spatula, and passes through the printing plate opening. As a result, the solder paste is supplied onto the substrate. Since the amount of solder paste supplied is determined by the size of the opening and the thickness of the printing plate, the size of the opening is adjusted by the diameter of the through hole 2. As a result, an optimal solder paste is applied to the through hole 2.

  FIG. 3 is a cross-sectional view showing the structure of the mounting portion of the circuit board before screwing. When cream solder printing is performed and heating by reflow is performed, the solder on the through hole 2 melts and flows into the through hole 2 to form shapes as shown in FIGS. 7a and 7b. The inside of the through hole 2 is filled with solder, and the surface of the substrate rises in a mountain shape due to surface tension. At this time, the amount of solder paste is adjusted so that the solder does not rise too much. By doing so, the substrate becomes flat with the solder piles being crushed by the screws 1. Since the resist opening at the hole of the through hole 2 is set larger than the hole diameter, the solder pile is in close contact with the ground pattern 3, and even if crushed with a screw, the solder does not come off from the copper foil and the solder bump and ground pattern are surely Will be in contact. The size of the resist opening on the through hole does not necessarily need to be larger than the hole diameter of the through hole, but it is desirable that the resist opening be larger in order to increase the adhesion with the solder. Since the inside of the through hole is filled with solder in a state where solder is applied and reflowed, the connection to the ground layer can be made stronger than a normal through hole.

  FIG. 1 shows the substrate screwed. The solder pile 7a is crushed by screwing, and the board and the screw head are brought into close contact with each other. Since the height of the resist 8 on the substrate surface is equal to the height of the solder 7 and the contact area between the screw head and the circuit board 5 is maximized, the screw 1 is not loosened. The solder pattern 7b provided on the housing 4 side can also strongly connect the ground pattern 3 of the substrate and the housing 4 by crushing the solder with the housing 4. At this time, since the housing 4 and the substrate 5 can be brought into contact with each other on the surface, they do not loosen.

Sectional drawing which shows the attachment part structure of the circuit board based on this invention The perspective view which shows the attachment part structure of the circuit board based on this invention Sectional drawing which shows the attachment part structure before screwing of the circuit board which concerns on this invention Sectional view showing a conventional circuit board mounting structure

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Board fixing screw 2 Through hole 3 Ground pattern 4 Electronic equipment housing 5 Circuit board 6 Screw insertion hole 7a Solder pile on the side where the screw head contacts
7b Solder pile on the side where the casing 4 contacts 8 Resist on the board surface 9 Ground layer inside the circuit board

Claims (7)

  In a fixing portion that requires electrical grounding of the circuit board, the circuit board has a ground pattern around the mounting hole of the circuit board into which the board fixing screw is inserted, a plurality of through holes are provided in the ground pattern, and a resist is formed on the through hole. A circuit board having an opening, and having a solder pile in the resist opening.   The circuit board according to claim 1, wherein a solder pile on the through hole is disposed at a position where the solder pile can come into contact with the board fixing screw.   The circuit board according to claim 1, wherein a resist opening diameter of the through hole portion is larger than a hole diameter of the through hole.   The circuit board according to claim 1, wherein a plurality of the through holes are arranged at equal intervals in the circumferential direction on the outer periphery of the mounting hole.   The circuit board according to any one of claims 1 to 4, wherein the positions of the through holes and the solder piles on the circuit board have the same coordinates.   6. The circuit board according to claim 1, wherein the through hole is formed by a through through hole or SVH (surface via hole).   The circuit board according to claim 1, wherein the solder piles are provided on both a component surface and a solder surface.

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