JP2009026946A - Surface mounted electronic circuit unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electronic circuit unit capable of preventing a mounting defect due to a tilt of a circuit board where a pedestal member is soldered. <P>SOLUTION: The electronic circuit unit 1 is surface-mounted on a mother board 20 and used, and the height position of the circuit board 2 where an electronic component 3 is mounted to the mother board 20 is regulated on the basis of the pedestal member 8. The pedestal member 8 is formed by punching a metal plate and beveled portions 8a and 8b are provided at circumferential edges of a top surface and a reverse surface of the pedestal member 8. The one beveled portion 8a is formed as an annular inclined surface by stamping and the other beveled portion 8b is formed as sag in punching. A group of first lands 5 and a group of second lands 6 are formed on a reverse surface of the circuit board 2; and the pedestal member 8 is soldered to each first land 5, and a solder ball 9 is added to each second land 6. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electronic circuit unit in which electronic components are mounted on a circuit board provided with wiring patterns and lands, and in particular, a solder ball is disposed on the lower surface side of the circuit board to provide an upper surface of the mother board. The present invention relates to a surface-mounting electronic circuit unit that is to be mounted.

  This type of electronic circuit unit is configured so that an electronic component mounted on a circuit board is electrically connected to a mother board via a solder ball, and is widely used in electronic devices such as short-range wireless devices. A wiring pattern is formed on at least the upper surface of the circuit board of the electronic circuit unit, and electronic components mounted on the circuit board are connected to the wiring pattern. In addition, land groups connected to the wiring pattern through through-hole conductors or the like are formed on the lower surface of the circuit board, and solder balls are attached to the land groups, respectively. Then, by reflow soldering by aligning the solder ball group of the electronic circuit unit to the land group of the external circuit formed on the upper surface of the mother substrate, the electronic circuit unit of the electronic circuit unit is passed through the solder ball group solidified after melting. The electronic component is connected to the land of the external circuit.

  By the way, when this type of electronic circuit unit is placed on the mother board and reflow soldering is performed, the solder balls are melted. Therefore, on the lower surface side of the circuit board of the electronic circuit unit, a metal base member that does not melt during reflow soldering It is desirable to arrange. That is, pedestal members set to a predetermined height are arranged in advance at a plurality of locations on the lower surface side of the circuit board so that the electronic circuit unit is held in a stable posture on the mother board by these pedestal members. By doing so, the distance between the lower surface of the circuit board and the upper surface of the mother substrate can be maintained with high accuracy even during reflow soldering, so that mounting defects can be avoided and the density of the solder balls can be easily increased.

Although such a pedestal member using a metal sphere is also known, from the viewpoint of increasing the peel strength, a metal plate having a solder film formed on the surface is punched out to form a pedestal member, and this pedestal member is formed on the circuit board. Conventionally, an electronic circuit unit configured to be soldered to a predetermined land on the lower surface has been proposed (see, for example, Patent Document 1). When a plate-like pedestal member is used in this way, the upper and lower surfaces become flat surfaces, so a lot of solder is interposed between the land of the circuit board and the pedestal member, or between the mother board and the pedestal member. Thus, the peel strength of the base member can be increased.
JP 2006-237064 A (page 5-6, FIG. 1)

  However, as described above, the conventional electronic circuit unit using the pedestal member punched from the metal plate has a sag at the time of punching on the upper surface side of the pedestal member facing the land of the circuit board. Accordingly, since the distance between the land and the pedestal member is different, there is a problem that the circuit board tends to be inclined on the mother board. That is, in the manufacturing process of the electronic circuit unit, the pedestal member punched from the metal plate has a sag formed on the peripheral edge of one surface and a burr formed on the peripheral edge of the other surface, and the pedestal member distinguishes the top and bottom. Since they are supplied to the circuit board all at once by the automatic feeder, the opposing surface of the pedestal member soldered to the land of the circuit board may be a sagging surface or a burr surface. As shown in FIG. 6, when the sag surface 30a of the pedestal member 30 faces the land 32 of the circuit board 31, the solder 33 flows into the chamfered portion (upper surface peripheral edge portion). The solder layer interposed between the upper surface of the member 30 and the land 32 is thinned, so that the distance between the base member 30 and the land 32 is slightly narrowed. However, when the burr surface 30b of the pedestal member 30 faces the land 32 of the circuit board 31 as shown in FIG. 7, the solder 33 does not flow into the peripheral edge of the upper surface. The solder layer interposed between the lands 32 is thickened, and therefore the distance between the base member 30 and the lands 32 is slightly widened. Therefore, the height positions of the lower surfaces of the plurality of pedestal members 30 disposed on the lower surface side of the circuit board 31 are likely to vary. Therefore, the circuit board 31 may be inclined on the mother board, resulting in a mounting failure. was there.

  The present invention has been made in view of the actual situation of the prior art, and an object of the present invention is to provide an electronic circuit unit capable of preventing a mounting failure due to an inclination of a circuit board to which a base member is soldered. is there.

  In order to achieve the above object, according to the present invention, a wiring pattern is formed on at least an upper surface, a first land group and a second land group are formed on a lower surface, and the second land group is the wiring pattern. A circuit board electrically connected to the circuit board, electronic components mounted on the circuit board and connected to the wiring pattern, and a plurality of pedestal members formed by punching a metal plate and soldered to the first land group, A plurality of solder balls attached to the second land group, and the space between the lower surface of the circuit board and the upper surface of the mother board is defined by the pedestal member, and the solder balls are placed on the mother board. In the electronic circuit unit that is mounted by being connected to a predetermined portion, the pedestal member has chamfered portions at the periphery of the upper surface and the lower surface, and the pair of chamfered shapes The volume of the space of the space and the lower surface peripheral portion of the top rim portion which is chamfered is set to be substantially equal by.

  In this way, when the chamfered shape portions having substantially the same chamfering amount are provided on both end surfaces of the plate-like base member, the case where one end surface of the base member is soldered to the first land of the circuit board and the other In comparison with the case where the end surfaces of the first and second end surfaces are soldered together, the amount of solder flowing into the chamfered shape portion is substantially equal, so the thickness of the solder layer interposed between the first land and the end surface is also substantially equal. Therefore, even if any of the top and bottom end surfaces of the pedestal member is soldered to the first land, the distance between the pedestal member and the first land does not vary. Therefore, in an electronic circuit unit configured by arranging a plurality of such pedestal members on the lower surface side of the circuit board, the height position of the lower surface of these pedestal members does not vary, and the inclination of the circuit board on the mother board is prevented. Can be prevented.

  Since the pedestal member is formed with a sag at the periphery of one side and a burr is formed at the periphery of the other surface when it is punched from the metal plate, this sag is used as one chamfered shape portion and It is preferable to form an inclined surface on the surface by pressing so as to form the other chamfered shape portion, because a pedestal member having a desired shape can be easily produced simply by adding a pressing step.

  In the above configuration, the overall shape of the pedestal member is not particularly limited, but when the upper surface and the lower surface of the pedestal member are circular flat surfaces and the chamfered shape portion is formed in an annular shape, When a large external force such as an impact acts on the electronic circuit unit, stress is less likely to concentrate on a specific portion of the base member, which is preferable.

  According to the electronic circuit unit of the present invention, since the chamfered shape portions having substantially the same chamfering amount are provided on both top and bottom surfaces of the pedestal member formed by punching the metal plate, any one of the top and bottom end surfaces of the pedestal member is a circuit. Even if solder-bonded to the first land of the substrate, the distance between the base member and the first land does not vary. Therefore, in an electronic circuit unit configured by arranging a plurality of such pedestal members on the lower surface side of the circuit board, the height position of the lower surface of these pedestal members does not vary, and the inclination of the circuit board on the mother board is prevented. Therefore, mounting defects due to the inclination of the circuit board do not occur.

  An embodiment of the invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of a principal part showing a state where an electronic circuit unit according to an embodiment of the invention is surface-mounted, and FIG. 2 is used in the electronic circuit unit. 3 is a bottom view of the circuit board, FIG. 3 is a cross-sectional view of the main part showing a portion different from FIG. 1 of the electronic circuit unit, FIG. 4 is an explanatory view showing a procedure for producing a base member used in the electronic circuit unit, It is a perspective view of this base member.

  An electronic circuit unit 1 shown in FIG. 1 is a module in which various electronic components 3 are mounted on the upper and lower surfaces of a square circuit board 2 (see FIG. 2), and is mounted on a mother board 20 in a surface-mounted manner. It has come to be used. A wiring pattern 4 is formed on both upper and lower surfaces and an inner layer of the circuit board 2 that is a laminated substrate, and a group of electronic components 3 is connected to the wiring pattern 4. As shown in FIG. 2, on the lower surface of the circuit board 2, first lands 5 are formed at the four corners, and a large number of second lands 6 are formed along the four sides. However, the first land 5 is formed several times larger in area than the second land 6. The first land 5 is connected to the ground area of the wiring pattern 4 via a through-hole conductor (not shown), and the second land 6 is connected to the hot area of the wiring pattern 4 via the through-hole conductor 7 etc. Has been. A disk-shaped base member 8 is soldered to each of the first lands 5 group, and a solder ball 9 is attached to each of the second lands 6 group. As will be described later, the pedestal member 8 is produced by punching or pressing a metal plate 15 having a solder film formed on the surface, and the lower surface side of the pedestal member 8 is formed on the upper surface of the mother substrate 20. It is soldered to the land 21 of the earth circuit. On the other hand, the solder ball 9 is connected to a predetermined land 22 formed on the upper surface of the mother substrate 20. The plurality of electronic components 3 mounted on the circuit board 2 are covered with a shield cover 10 made of a metal plate, and the shield cover 10 is connected to the ground area of the wiring pattern 4 on the circuit board 2. It is attached. Note that a solder resist film 11 is formed on the upper and lower surfaces of the circuit board 2 on almost the entire surface except for the land forming portions.

  The electronic circuit unit 1 configured in this manner is placed at a predetermined position on the mother board 20 and reflow soldered in a state where the base member 8 and the solder ball 9 are aligned with the lands 21 and 22, respectively. Surface-mounted on the mother board 20. At this time, since the four corners of the circuit board 2 are supported by the pedestal member 8, the distance between the lower surface of the circuit board 2 and the upper surface of the mother board 20 is kept constant by the pedestal member 8 even when the solder balls 9 melt. It is. That is, the height position of the circuit board 2 placed on the mother board 20 is defined based on the base member 8. The solder 12 and 13 interposed between the base member 8 and the first land 5 or land 21 are melted and solidified, so that the base member 8 is soldered to the upper and lower lands 5 and 21. When the solder ball 9 is melted and solidified, the second land 6 is connected to the land 22 of the external circuit. Note that a solder resist film 23 is formed on the entire upper surface of the mother substrate 20 except for the land forming portion.

  The pedestal member 8 used in the electronic circuit unit 1 will be described in detail. As shown in FIGS. 1 and 5, the pedestal member 8 has chamfered portions 8a and 8b on the periphery of the upper surface and the lower surface, respectively. Yes. One chamfered shape portion 8a is formed as an annular inclined surface by press working after punching, while the other chamfered shape portion 8b is formed as a sag during punching. The volume of the space of the upper surface peripheral portion chamfered by the chamfered shape portions 8a and 8b is set to be substantially equal to the volume of the space of the lower surface peripheral portion. However, the upper surface and the lower surface of the base member 8 are not determined in advance. As shown in FIG. 1, a chamfered shape portion 8a (inclined surface) exists on the upper surface side, and a chamfered shape portion 8b (sag) on the lower surface side. In some cases, the pedestal member 8 may be soldered to the circuit board 2 in a state where the pedestal exists, or in the state where the chamfered shape portion 8b exists on the upper surface side and the chamfered shape portion 8a exists on the lower surface side as shown in FIG. The member 8 may be soldered to the circuit board 2 in some cases.

  Next, the manufacturing procedure of the base member 8 will be described with reference to FIG. The base material of the pedestal member 8 is a band-shaped metal plate 15 having a solder film formed on the surface. After forming the disk member 80 by punching the metal plate 15 into a circle with a punch 16, the disk member 80 is After returning to the punching hole 15a of the metal plate 15, it is sent to a press machine (not shown), and by pressing one side of the disk member 80 by this press machine, a base member 8 as shown in FIG. 5 is produced. . The disk member 80 obtained by punching has a burr surface 80a on one side and a sag surface 80b on the other side. However, an annular inclined surface is formed on the periphery of the burr surface 80a by subsequent pressing, and the chamfering is performed. The sag of the sag surface 80b is left as it is to form the chamfered shape part 8b. Since the shape and size of the sag of the disk member 80 are always substantially constant, it is easy to set the chamfering amount by the chamfered shape portion 8a to be substantially equal to the chamfering amount by the chamfered shape portion 8b during pressing. .

  Since the pedestal member 8 manufactured in this way is supplied to the circuit board 2 all at once by an automatic feeder without distinguishing the top and bottom, the pedestal member 8 to be soldered to the first land 5 of the circuit board 2 is used. In some cases, a chamfered shape portion 8a exists on the opposite surface (see FIG. 1), and in other cases, a chamfered shape portion 8b exists (see FIG. 3). However, regardless of which end face of the pedestal member 8 is soldered to the first land 5, the amount of solder 12 flowing into the chamfered shape portions 8a, 8b facing the first land 5 during reflow soldering is substantially the same. Therefore, the thickness of the solder layer interposed between the first land 5 and the end surface is substantially the same. Therefore, the distance between the base member 8 and the first land 5 does not vary even if any of the top and bottom end surfaces of the base member 8 is soldered to the first land 5.

  As described above, in the electronic circuit unit 1 according to this embodiment, the chamfered portions 8a and 8b having substantially the same chamfering amount are provided on both top and bottom surfaces of the base member 8 formed by punching the metal plate 15. Even if any of the top and bottom end surfaces of the base member 8 is soldered to the first land 5 of the circuit board 2, the distance between the base member 8 and the first land 5 does not vary. Therefore, in the electronic circuit unit 1 configured by disposing the pedestal members 8 at the four corners on the lower surface side of the circuit board 2, the height positions of the lower surfaces of the pedestal members 8 do not vary, so The inclination of the circuit board 2 can be prevented, so that no mounting failure due to the inclination of the circuit board 2 occurs.

  Further, in the present embodiment example, a sag formed on one surface of the base member 8 when it is punched from the metal plate 15 is used as one chamfered shape portion 8b, and the other chamfered shape portion 8a is stamped after punching. Since it is formed by processing, the base member 8 having a desired shape can be easily produced simply by adding a pressing step.

  Further, if the upper surface and the lower surface of the pedestal member 8 are flat surfaces as in this embodiment, it is easy to increase the peel strength of the pedestal member 8 by attaching a lot of solder to the flat surface. Moreover, in this embodiment, the upper and lower surfaces of the pedestal member 8 are circular and the chamfered portions 8a and 8b are formed in an annular shape, so that a large external force such as an impact acts on the electronic circuit unit 1 after mounting. Sometimes, stress is less likely to concentrate on a specific part of the base member 8, and the peel strength is further increased. However, even when the pedestal member is not in the shape of a disk, it is possible to expect substantially the same effect as in the present embodiment example by providing chamfered portions having substantially the same chamfering amount on both end surfaces of the top and bottom.

  In the embodiment described above, the pedestal members 8 are disposed at the four corners of the circuit board 2, but the number and arrangement of the pedestal members 8 can be appropriately selected according to the shape and size of the circuit board 2. . The circuit board 2 may be a single layer board, and the electronic component 3 may not be mounted on the lower surface of the circuit board 2.

It is principal part sectional drawing which shows the state which surface mounted the electronic circuit unit which concerns on the example of embodiment of this invention. It is a bottom view of the circuit board used with this electronic circuit unit. It is principal part sectional drawing which shows the site | part different from FIG. 1 of this electronic circuit unit. It is explanatory drawing which shows the preparation procedures of the base member used with this electronic circuit unit. It is a perspective view of this base member. It is explanatory drawing of the base member which concerns on a prior art example. It is explanatory drawing at the time of using the base member shown in FIG. 6 upside down.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electronic circuit unit 2 Circuit board 3 Electronic component 4 Wiring pattern 5 1st land 6 2nd land 8 Base member 8a, 8b Chamfering shape part 9 Solder ball 12 Solder 15 Metal plate 20 Mother board 80 Disc member 80a Burr surface 80b Sagging surface

Claims (3)

A circuit board in which a wiring pattern is formed on at least the upper surface, a first land group and a second land group are formed on the lower surface, and the second land group is electrically connected to the wiring pattern; and An electronic component mounted and connected to the wiring pattern; a plurality of pedestal members formed by punching a metal plate and soldered to the first land group; and a plurality of base members attached to the second land group An electronic circuit unit that includes a solder ball and is mounted by connecting the solder ball to a predetermined portion on the mother board while defining a distance between the lower surface of the circuit board and the upper surface of the mother board by the base member There,
The pedestal member has chamfered portions on the periphery of the upper surface and the lower surface, and the volume of the space of the upper surface periphery and the space of the lower surface periphery chamfered by the pair of chamfered portions is substantially equal. A surface-mounting electronic circuit unit characterized by being set to be   2. The method according to claim 1, wherein one of the pair of chamfered portions is a sag formed during the punching, and the other is an inclined surface formed by pressing after the punching. Surface mount electronic circuit unit.   3. The surface mount electronic circuit unit according to claim 1, wherein the upper surface and the lower surface of the pedestal member are circular flat surfaces, and the chamfered portion is formed in an annular shape.

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