WO2008001462A1 - Mounting structure for printed board - Google Patents

Abstract

A mounting structure for a printed board, where, when the printed board on which components are mounted is fixed to a fixed structure such as a housing, mechanical stress in solder joints of components soldered on the printed substrate is mitigated and where the space of the printed board can be effectively used to adapt the board to high density mounting. The mounting structure has cushioning sections (20, 22, 24) near the vicinity of fixation holes (14) for fixing the printed board (10) to the fixed structure. The cushioning sections are formed as slits or grooves and absorb stress caused by the fixing.

Description

 Specification

 PCB mounting structure

 Technical field

 [0001] The present invention absorbs stress generated between a printed circuit board and a housing in a printed circuit board mounting structure, in particular, a structure in which the printed circuit board is fixed to a structure such as a housing with screws or the like. The present invention also relates to a printed circuit board mounting structure that can be relaxed.

 Background art

 A printed circuit board is usually fixed by reflow soldering or the like when various electronic components are mounted on the printed circuit board. When soldering, the temperature reaches the temperature at which the solder melts, so there is a difference in the coefficient of thermal expansion between the components and the printed circuit board itself, or between the resin and metal parts of the printed circuit board. Thermal stress is applied to the entire printed circuit board. As a result, the completed component mounting printed circuit board is often warped. In this way, when the printed circuit board is fixed to a fixed structure such as a housing by screwing or the like in a warped state, mechanical stress is applied to the soldered portion of the printed circuit board in order to correct the warpage of the printed circuit board. May be applied and the solder joint may be destroyed. This problem is particularly important for printed circuit boards used for portable terminals and the like that must be lightweight and downsized because the solder joints are fine.

 FIG. 1 and FIG. 2 show a conventional general printed circuit board mounting structure. Fig. 1 (a) is a plan view of a printed circuit board on which electronic components are mounted, and Fig. 1 (b) is a side view thereof. The printed circuit board 1 is made of a resin such as glass epoxy. The necessary electronic component 2 is fixedly mounted on the printed circuit board 1 with the solder 3 as described above, but the printed circuit board 1 on which the electronic component 2 is mounted is warped as shown in Fig. 1 (b). There are many cases.

[0004] With the printed circuit board 1 on which the electronic component 2 is mounted being warped, as shown in FIG. Fixed. In this way, the printed circuit board 1 is mounted with its warpage corrected, and when it is fixed to the housing 5, stress is applied to the printed circuit board 1 to correct the warpage. Therefore, as described above, mechanical stress is applied to the soldered portion 7 of the printed circuit board 1, and the solder as shown in the figure. The joint 7a may be destroyed.

 [0005] Japanese Utility Model Laid-Open No. 5-41169 is a prior art for preventing the above-described stress from occurring when a printed circuit board is fixed to a fixed structure such as a housing with screws. The purpose of this is to control the stress generated in the electronic components mounted on the board body, to prevent deterioration and destruction of the characteristics of the electronic parts, and to improve the reliability at low cost. If there is a slit extending around the screw hole from the top of the board, and the entire board is warped or the mounting part is misaligned, stresses due to deformation may occur in the part of the board body where the electronic components are mounted. It is preventing.

 [0006] In this prior art, the stress due to deformation of the printed circuit board is absorbed by the slit. The slit extends from the peripheral edge of the circuit board body to the periphery of the screwing hole, and is a screw hole for fixing the printed circuit board. If the position is near the peripheral edge of the printed circuit board, there is no particular problem. However, if it is inside the peripheral edge of the printed circuit board, such a slit cannot be provided, or the peripheral edge of the circuit board is not provided. There is a problem in the layout design of the printed circuit board because a long slit extending from the inside to the inside must be provided.

 [0007] Patent Document 1: Japanese Patent Laid-Open No. 5-041169

 Disclosure of the invention

 Problems to be solved by the invention

 [0008] As described above, when a printed circuit board on which an electronic component is mounted is fixed to a fixed structure in a warped state, stress is applied to the printed circuit board to correct the warpage, thereby soldering the printed circuit board. Mechanical stress is applied to the part, and the solder joint may be destroyed. In addition, as in Patent Document 1, when a slit extending from the peripheral edge of the board body to the periphery of the screwing hole is provided in the board body, the slit extends from the peripheral edge of the board body to the periphery of the screwing hole. If the fixed part of the printed circuit board is in the interior away from the peripheral edge, it is difficult to provide a slit, or the length and slit extending from the peripheral edge of the board to the inside must be provided. There is a problem.

Therefore, in the present invention, in order to solve the problems in the conventional printed circuit board mounting structure described above, the printed circuit board on which components are mounted is fixed to a fixed structure such as a housing by screwing or the like. In solder joints of soldered parts on printed circuit boards It is an object of the present invention to provide a printed circuit board mounting structure that can relieve mechanical stress and that can effectively use the space of the printed circuit board and is suitable for high-density mounting.

 Means for solving the problem

 In order to achieve the above object, according to the present invention, the stress associated with the fixing is absorbed in the vicinity of the periphery of the fixing hole for fixing the printed circuit board to the fixed structure. There is provided a printed circuit board mounting structure provided with a buffer portion.

 As described above, in the present invention, in a structure in which a printed circuit board on which a component is mounted is fixed to a fixed structure such as a housing by screwing or the like, stress absorption is provided near the periphery of the fixed hole on the printed circuit board. Since the buffer portion is provided, when the printed circuit board is fixed to the fixed structure, the mechanical stress generated due to the warping of the printed circuit board can be reduced. Therefore, the solder joints of the soldered parts mounted on the printed circuit board can be prevented from being damaged or damaged, and this buffering part is only in the vicinity of the fixing hole. This will not affect the space required, and can effectively use the entire component mounting area of the printed circuit board, resulting in a structure suitable for high-density mounting.

 [0012] The buffer portion is characterized by comprising one or both of a slit penetrating the printed circuit board and a non-penetrating groove. As described above, since the buffer portion is formed by a slit or groove force provided on the printed circuit board, the buffer portion is well-known by mechanical processing such as cutting of the printed circuit board iJ, drill, or chemical processing such as etching. Can be easily formed by the method

[0013] The buffer portion includes a slit, and a plurality of the slits are provided in an arc shape on a circle concentric with the fixing hole. By making the buffer part a plurality of slits, the surrounding area in the vicinity of the fixing hole can be made a uniform stress absorbing portion.

 [0014] The buffer portion includes grooves provided on both sides or one side of the printed circuit board, and the grooves are provided along a circle concentric with the fixing hole. In this case, a plurality of the grooves are provided in an arc shape. By making the buffer portion into a plurality of arc-shaped grooves, the peripheral region in the vicinity of the fixing hole can be made a uniform stress absorbing portion.

[0015] Further, the printed circuit board has one or more glass epoxy resins on both sides of the polyimide resin layer. A multilayer board in which layers are laminated, wherein the groove provided on both sides or one side of the printed board is formed by removing a portion of the glass epoxy resin layer. Thereby, the flexible polyimide resin layer of the inner layer of the printed circuit board can be effectively used as a buffer layer for absorbing stress.

 [0016] Further, the buffer portion may be a non-penetrating groove provided along a circle concentric with the fixing hole on one or both surfaces of the printed circuit board, and one or more provided in a part of the groove. It consists of a plurality of through slits. As described above, by configuring the buffer portion by combining the non-penetrating groove and the penetrating slit, the peripheral region in the vicinity of the fixing hole can be made a uniform and flexible stress absorbing portion.

 Brief Description of Drawings

 FIG. 1 shows a state before mounting of a conventional general printed circuit board mounting structure, where (a) is a plan view and (b) is a side view.

 FIG. 2 is a side view showing a state after mounting of the printed circuit board mounting structure of the conventional example.

 FIG. 3 is a plan view showing a first embodiment of a printed circuit board mounting structure according to the present invention.

 FIG. 4 shows a second embodiment of the printed circuit board mounting structure of the present invention, in which (a) is a plan view and (b) is an A_A cross-sectional view of (a).

 FIG. 5 shows a third embodiment of the printed circuit board mounting structure of the present invention, in which (a) is a plan view.

(B) is a BB sectional view of (a).

 FIG. 6 is an enlarged sectional view of a portion indicated by C in FIG. 5 (b).

 BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIGS. 3 to 5 show the embodiments of the printed circuit board mounting structure of the present invention. The printed circuit board 10 is made of a resin such as glass epoxy. The necessary electronic components 12 are fixedly mounted on the printed circuit board 1 with solder (not shown) as described above. The printed circuit board 10 is provided with a fixing hole 14 for fixing the printed circuit board 10 to a fixed structure (not shown) such as a housing.

In the first embodiment shown in FIG. 3, a plurality of slits 20 penetrating the printed circuit board 10 are provided as buffer portions near the periphery of the fixing hole 14 of the printed circuit board 10. These The through slits 20 are formed as arc-shaped slits that are concentric with the fixing hole 14 and are arranged at three equal intervals along a circumference in the vicinity of the circumference.

 Therefore, as described above, even when the printed circuit board 10 on which the electronic component 12 is mounted is warped and is fixed to a fixing structure (not shown) such as a housing in this state, these Three arcuate slits 20 serve as buffer portions, and can absorb mechanical stress accompanying the warping of the printed circuit board 10. By making the buffer part a plurality of slits, the surrounding area in the vicinity of the fixing hole can be made a uniform stress absorbing portion.

 As described above, since the arc-shaped slits 20 are arranged at three positions at equal intervals, even when the printed circuit board 10 is fixed to the housing by screwing using the fixing holes 14, A uniform buffering action can be produced around the fixing hole 14.

 FIG. 4 (a) is a plan view showing a second embodiment of the printed circuit board mounting structure of the present invention, and FIG. 4 (b) is a cross-sectional view taken along A_A in FIG. 4 (a). In the second embodiment, a groove 22 that does not penetrate the printed circuit board 10 is provided as a buffering part near the periphery of the fixing hole 14 on the mounting surface side of the electronic component 12 of the printed circuit board 10. These non-through grooves 22 are concentric with the fixing hole 14 and are arranged in an arc shape arranged at three equal intervals along the circumference in the vicinity of the circumference.

 [0024] As in the case of the first embodiment, even when the printed circuit board 10 on which the electronic component 12 is mounted is warped and is fixed to a fixed structure (not shown) such as a housing in this state, these These three arc-shaped non-penetrating grooves 22 serve as buffer parts, and can absorb mechanical stress accompanying warping of the printed circuit board 10.

 [0025] Since the arc-shaped non-through grooves 22 are arranged at three equal intervals, the printed circuit board 1 is fixed to a fixed structure such as a housing by screwing using the fixing holes 14. However, a uniform buffering action can be produced around the fixing hole 14.

 FIG. 5 (a) is a plan view showing a third embodiment of the printed circuit board mounting structure of the present invention, and FIG. 5 (b) is a sectional view taken along line BB in FIG. 5 (a). FIG. 6 is an enlarged cross-sectional view of a portion indicated by C in FIG. 5 (b).

In the third embodiment, the printed circuit board 10 is configured as a multilayer printed circuit board in which a plurality of glass epoxy resin layers 10b are laminated on both surfaces of the middle polyimide resin layer 10a. The A conductive layer 10c made of a copper pattern is formed between both surfaces of the middle polyimide resin layer 10a and the upper surface of each glass epoxy resin layer 10b, that is, between the layers.

 [0028] In the third embodiment, the non-penetrating grooves 24 are formed on both surfaces of the printed circuit board 10 and concentrically with the fixing hole 14 and along the circumference in the vicinity thereof. In the groove 24, the glass epoxy resin layer 10b is removed, leaving only the middle polyimide resin layer 10a. As a result, the flexible polyimide resin layer 10a, which is the middle layer of the printed circuit board 10, is exposed to the non-penetrating groove 24, and this portion effectively acts as a buffer layer for absorbing stress.

 [0029] Note that the non-penetrating groove 24 in the third embodiment can be formed during the process of manufacturing the multilayer rigid flexible printed circuit board 10 itself.

 [0030] The power of the embodiments of the present invention described above with reference to the accompanying drawings. The present invention is not limited to the above-described embodiments, and various forms, modifications, corrections and the like are possible within the spirit and scope of the present invention. Is possible.

 Industrial applicability

[0031] As described above, according to the present invention, the buffer part for absorbing the stress accompanying the fixing is provided near the periphery of the fixing hole for fixing the printed board to the fixed structure. Since it is installed, it can be mounted on a printed circuit board, avoiding damage and damage to the solder joints of the soldered parts, and this buffer is only near the periphery of the fixing hole. The main space of the board is not affected, and the entire component mounting area of the printed circuit board can be used effectively, resulting in a structure suitable for high-density mounting.

Claims

The scope of the claims  [1] Mounting a printed circuit board characterized in that a buffer portion for absorbing stress accompanying the fixing is provided near the periphery of the fixing hole for fixing the printed circuit board to a fixed structure. Construction.  [2] The printed circuit board mounting structure according to [1], wherein the buffer portion includes one or both of a slit penetrating the printed board and a non-penetrating groove. 3. The printed circuit board mounting structure according to claim 2, wherein the buffer portion includes a slit, and a plurality of the slits are provided in an arc shape on a circle concentric with the fixing hole. [4] The buffer section according to claim 2, wherein the buffer section includes grooves provided on both sides or one side of the printed circuit board, and the grooves are provided along a circle concentric with the fixing hole. The mounting structure of the printed circuit board.  5. The printed circuit board mounting structure according to claim 4, wherein a plurality of the grooves are provided in an arc shape.  [6] The printed board is a multilayer board in which one or a plurality of glass epoxy resin layers are laminated on both sides of the polyimide resin layer, and the groove provided on both sides or one side of the printed board is made of glass epoxy resin. 6. The printed circuit board mounting structure according to claim 4, wherein the layer portion is formed by being removed. [7] The buffer portion includes a non-penetrating groove provided along a circle concentric with the fixing hole on one side or both sides of the printed circuit board, and one or a plurality of grooves provided in a part of the groove. The printed circuit board mounting structure according to claim 2, wherein a through slit force is provided.