JP2006287060A - Circuit board and soldering structure of chip component - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a generation of a solder ball due to a stuck-out soldering paste 33 formed by sticking out the surplus soldering paste 33 to a chip component 15 when the electrode 16 of the chip component 15 is soldered up to a land 22 of a circuit substrate 20. <P>SOLUTION: A printing position of a solder resist 23 around the land 22 on the circuit board 20 is contrived, the solder resist is prevented from contacting with the tip edge and the side edge of the land side of the opposite side of the land 22, and solder leading-in grooves 27 and 28 are continuously formed in a U shape. The soldering paste 33 stuck-out from the land 22 toward the land side of the opposite side is led in the solder leading-in groove 27, and the soldering paste 33 stuck-out toward the side direction is led in the solder leading-in groove 28. A good soldering fillet 34 is formed by the wall 30 of the end edge of the solder resist 23 formed at a position opposing the electrode 16 of the chip component 15 of the land 22. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a soldering structure for a circuit board and a chip component, and more particularly to a circuit board having lands for soldering electrodes at both ends of the chip component, and a soldering structure for the chip component to the circuit board.

  In accordance with the demand for downsizing of electronic circuit devices, surface mount type chip components tend to be widely used instead of leaded components. FIG. 5 shows a mounting structure of such a chip component 1 to the circuit board 2. The chip component 1 has a substantially rectangular parallelepiped outer casing, and includes electrodes 3 at both ends in the length direction or the axial direction. Such an electrode 3 is soldered to a land 4 formed by etching a copper foil on the circuit board 2. Note that portions other than the land 4 of the circuit board 2 are covered with a film made of the solder resist 5.

  The positional relationship between the land 4 and the solder resist 5 on the conventional circuit board 2 is shown in FIG. That is, the entire edge of the peripheral edge of the land 4 is covered with the solder resist 5. According to such a structure of the land 4 of the conventional circuit board 2, there is a possibility that a solder ball is formed by excess solder. If the solder balls move freely in the device after forming an erroneous wiring or being detached, they cause a short circuit between electrodes or circuit patterns. Therefore, when the chip component 1 is soldered to the land 4 of the circuit board 2, it is necessary to prevent the solder balls 7 from being generated.

  A conventional solder ball generation mechanism is shown in FIG. 7, for example. A predetermined amount of solder paste 6 made of cream solder is applied onto the lands 4. Thereafter, the chip component 2 is mounted, and the electrode 3 is brought into contact with the solder paste 6. When reflow is performed in this state, the solder powder particles in the solder paste 6 are melted, and a part of the solder flows toward the opposite electrode side on the lower surface of the chip component 1. Such excessive solder protrudes to the side of the chip component 1 and becomes a solder ball 7 when solidified in this state.

  Further, as shown in FIG. 8, there is a case where a solder ball is formed by being pushed out to the side by the solder paste 6 inserted into the lower side of the chip component 1. That is, when the electrode 3 of the chip component 1 is placed on the solder paste 6 applied to the land 4 and a pressing force is applied, the cream-like solder paste 6 is extruded sideways, and the extruded solder When this is melted and solidified in this state, the solder ball 7 is obtained. If such a solder ball 7 rolls freely in the equipment as described above, it causes a short circuit accident.

  In Japanese Patent Application Laid-Open No. 2004-207287, in the soldering land, the solder resist formation structure between the land portion covered by the chip component to be mounted and the land portion not covered by the chip component to be mounted is changed. In the soldering land, the solder resist is removed only on the side where the chip component to be mounted covers, so that the solder that protrudes from the soldering land can easily return to the soldering land during reflow heating, and the solder during reflow heating There is disclosed a soldering land that suppresses the generation of solder balls that occur during soldering.

According to such a configuration, it is possible to prevent excessive solder that has flowed so as to penetrate into the lower surface of the chip component 1 from flowing out further to the side and forming solder balls. However, this configuration extends so that the solder resist completely overlaps on both sides of the land, so that there is no way to absorb the solder that has flowed directly to the side of the land. Therefore, solder balls cannot be completely prevented.
JP 2004-207287 A JP 2004-111605 A

  SUMMARY OF THE INVENTION An object of the present invention is to provide a circuit board and a chip component soldering structure that prevent the generation of solder balls caused by excess solder paste protruding from the side of the chip component.

  Another problem of the present invention is a circuit that can reliably absorb the excess solder not only when the excess solder flows out in the direction of the opposite land but also when it flows out to the side. It is to provide a soldering structure for a substrate and a chip component.

  Still another object of the present invention is to provide a circuit that prevents solder paste extruded around a chip component from forming a solder ball and adhering to the side surface of the chip component during reflow heating using the solder paste. It is to provide a soldering structure for a substrate and a chip component.

  Still another object of the present invention is to provide a circuit board and a chip component soldering structure that prevent occurrence of a short circuit accident due to solder balls accompanying soldering of the chip component.

  Still another object of the present invention is to provide a soldering structure for a circuit board and a chip part in which a good fillet is formed so that an electrode of the chip part can be correctly soldered to a land of the circuit board.

  The above-described problems and other problems of the present invention will be clarified by the technical idea and embodiments of the present invention described below.

The main invention of the present application is a circuit board having lands for soldering electrodes at both ends of a chip component.
From the edge facing the land on the opposite side of the land to the side edge, the solder introduction groove is formed in a substantially U shape,
The present invention relates to a circuit board characterized in that a wall portion facing an end face of an electrode of the chip component is formed in the vicinity of an edge farthest from the land opposite to the land.

  Here, the solder introduction groove is formed by forming a solder resist apart from an end edge and a side edge facing the opposite land of the land, and the land edge and the side edge and the solder resist It may be a groove formed of a recess formed between the end edge of each other. The wall portion is an edge of a solder resist formed on the land so as to face an end surface of the electrode of the chip component, and has a height corresponding to the thickness of the solder resist. Good. Further, the width of the land may be substantially equal to the width of the electrode of the chip component.

The main invention related to the soldering structure is the chip component soldering structure in which the electrodes on both ends of the chip component are respectively soldered to lands on the circuit board.
From the edge on the center side of the chip part to the side edge of the land, the solder introduction groove is formed in a substantially U shape, and the molten excess solder is drawn into the solder introduction groove,
A chip part, wherein a wall part is formed on the land so as to face an end face of the electrode of the chip part, and a solder fillet is formed by molten solder so as to extend from the wall part to the end face of the electrode. This relates to the soldering structure.

  Here, a width of the solder introduction groove may be in a range of 30 to 100 μm. The depth of the solder introduction groove may be in the range of 10 to 100 μm. Moreover, the height of the said wall part may exist in the range of 10-100 micrometers.

  In a preferred embodiment of the present invention, in a land for soldering a surface mount type chip component on a printed wiring board by reflow heating, a solder resist is applied so that the lower portion and the lateral portion of the chip component do not cover the land. It is related with the soldering land which forms. Here, it is preferable that the soldering land has a substantially rectangular shape and is substantially the same as the width of the chip component.

  According to the above aspect, when the chip component is mounted and the solder paste is melted by reflow heating, the solder enters between the land and the solder resist, so the solder paste is pushed out to the side surface of the chip component. Disappears. That is, since there is no solder paste to be extruded, no solder balls are generated on the side surfaces of the chip component. Furthermore, for the same reason, the solder paste is not extruded on the side surface side of the chip component, so that the width dimension of the chip component and the width dimension of the land can be made substantially the same, and for high density mounting. It becomes effective as a soldering land.

  The main invention of the present application is a circuit board having lands for soldering electrodes on both ends of a chip component, and a solder introduction groove is formed in a substantially U-shape from the edge opposite to the land on the opposite side of the land to the side edge. In addition, a wall portion facing the end face of the electrode of the chip component is formed in the vicinity of the edge farthest from the land on the opposite side of the land.

  Therefore, according to such a circuit board, the solder paste that has flowed out in the direction of the land on the opposite side of the chip component is introduced into a solder introduction groove formed at an edge facing the land on the opposite side of the land. Further, the solder paste protruding to the side of the chip component is guided to the side solder introduction groove. A good solder fillet is formed by the wall and the end face of the electrode.

  The main invention related to the soldering structure is a chip component soldering structure in which electrodes at both ends of a chip component are respectively soldered to lands on a circuit board, from the edge of the land on the center side to the side edge of the chip component. The solder introduction groove is formed in a substantially U shape, and the melted excess solder is drawn into the solder introduction groove, and a wall is formed on the land so as to face the end face of the electrode of the chip component. A solder fillet is formed by molten solder along the end face of the electrode.

  Therefore, according to such a soldering structure of the chip component, the solder paste protruding to the center side and the side of the chip component is drawn into the solder introduction grooves formed in the corresponding directions to prevent the formation of solder balls. . Further, a good solder fillet is formed along the end face of the electrode by the wall portion formed on the land and the end face of the electrode.

  The present invention will be described below with reference to embodiments shown in the drawings. FIG. 1 shows an outline of the present embodiment. Here, a chip component 15 is mounted on a circuit board 20. The chip component 15 has a rectangular parallelepiped outer shape, and electrodes 16 are formed at both ends. Such a chip component 15 is mounted on a land connected to the conductor pattern 21 of the circuit board 20, and the electrodes 16 at both ends of the chip component 15 are soldered to the lands 22. The land 22 has a substantially rectangular shape. Further, the surface of the circuit board 20 except the land 22 is covered with a solder resist 23.

  In particular, the relationship between the solder resist 23 and the land 22 is shown in FIG. That is, the solder resist 23 does not extend so as to overlap the entire area of the peripheral portion of the land 22, and in particular, in the peripheral portion facing the land on the opposite side of the land 22, the land 22 is formed around the solder resist 23. There is a gap between them, and this gap constitutes a solder introduction groove 27. Also, the solder resist 23 does not extend on both sides of the land 22, and solder introduction grooves 28 are formed. A wall portion 30 is formed by the edge of the solder resist 23 in the vicinity of the edge farthest from the land on the opposite side of the land 22. That is, a substantially vertical wall portion 30 is formed on the land 22 by the end face of the solder resist 23 extending so as to overlap from the conductor pattern 21 side. Further, as is apparent from FIG. 2B in particular, the dimension in the width direction of the land 22 is almost the same as the dimension of the electrode 16 of the chip component 15 here.

  The parts used here include the following types of parts. The unit of the electrode size of this component is mm.

0603 type parts electrode size 0.15 × 0.3
1005 type parts, electrode size 0.25 x 0.5
1608 type parts electrode size 0.4 × 0.8
2012 type parts electrode size 0.5 × 1.25
3216 type part electrode size 0.6 × 1.6
3225 type part electrode size 1.4 × 2.5
Type 4532 parts Electrode size 1.4 × 3.2
The land 22 on the circuit board 20 has a thickness of 43 ± 7 μm, for example, when the thickness of the copper foil is 18 μm. On the other hand, when the thickness of the copper foil is 12 μm, the land 22 has a thickness of 37 ± 7 μm. Further, the size of the land 22, that is, the size of the portion not covered with the solder resist, is equal in width to the width of the electrode 16 of the chip component 15, and the dimension in the length direction is the length of the electrode 16 of the chip component 15. It may be a value that is larger by 0.1 mm on the outside and on the inside than the dimension in the direction.

  Next, the thickness of the solder resist 23 which is a main factor for determining the depth of the solder introduction grooves 27 and 28 is, for example, 15 to 20 μm at the portion covered with the copper foil, and about the portion not covered with the copper foil. A value of 20-25 μm is preferred. Here, when the thickness of the solder resist 23 is increased, the depth of the solder introducing grooves 27 and 28 is increased, and when the thickness of the solder resist 23 is decreased, the thickness of the solder introducing grooves 27 and 28 is decreased. The height of the wall portion 30 is determined by the thickness of the solder resist 23 on the land 22. That is, the dimensions in the height direction of the solder introduction grooves 27 and 28 and the wall portion 30 are determined by the thickness of the solder resist 23.

  The width dimension of the solder introduction grooves 27 and 28 is preferably in the range of 30 to 100 μm. If the width is 30 μm or less, the capacity for accommodating excess solder in the solder introduction grooves 27 and 28 is reduced, or the effect is almost lost. On the other hand, when the width of the solder introduction grooves 27 and 28 is larger than 100 μm, the space on the surface of the circuit board 20 is created by the solder introduction grooves 27 and 28, thereby reducing the mounting density of components.

  FIG. 3 shows a mechanism for preventing the generation of solder balls by the solder introduction groove 27 formed in a portion facing the land on the opposite side of the land 22 in particular. Here, the solder paste 33 is first applied onto the lands 22. The chip component 15 is mounted thereon, and the electrode 16 is adhered to the solder paste 33. When introduced into the reflow furnace in this state, the solder in the solder paste 33 is melted, whereby the electrode 16 of the chip component 15 is soldered to the land 22. The solder melted at this time flows along the lower side of the chip component 15 to the opposite land 22 side. However, the flowing solder is drawn into the solder introduction groove 27 provided at the tip side portion of the land 22. Therefore, the solder paste 33 and the molten solder do not flow out to the side of the chip component 15, thereby preventing the generation of solder balls.

  As is clear from FIG. 3, the land 22 and the electrode 16 of the chip component 15 are particularly formed by the end face of the electrode 16 of the chip component 15 and the wall portion 30 formed by the edge of the solder resist 23 of the land 22. A good solder fillet 34 is formed between them. Therefore, this enables high quality soldering.

  FIG. 4 shows the operation of drawing the solder paste 33 or molten solder that has flowed out to the side of the land 22 of the circuit board 20. Again, the solder paste 33 is applied on the lands 22 of the circuit board 20, and the chip component 15 is mounted thereon, and the electrodes 16 are adhered to the solder paste 33. In such a state, when the circuit board 20 is introduced into the reflow furnace, the solder in the solder paste 33 is melted. The solder melted here flows to the side of the land 22 along the lower side of the chip component 15. However, solder introduction grooves 28 are formed on both sides of the land 22, and the molten solder that has flowed to the sides can be drawn in by the solder introduction grooves 28. Accordingly, it is possible to prevent molten solder from flowing out to the side of the chip component 15 and generating solder balls.

  As described above, the present embodiment is characterized by the shape of the soldering land 22 on the circuit board 20, and in the position corresponding to the lower part and the lateral part of the chip part 15, particularly the solder. The solder introduction grooves 27 and 28 are formed at these positions where the resist 23 is not covered and the solder resist 23 is not covered.

  Therefore, when such a soldering land 22 for the chip component 15 is used, when the chip component 15 is mounted and the solder paste 33 is melted by reflow heating, the solder introduction groove 27 in the gap between the land 22 and the solder resist 23 is formed. Since excessive solder enters, the solder paste 33 is not extruded onto the side surface of the chip component 15. Therefore, the solder paste 33 does not exist on the side, and no solder ball is generated on the side surface of the chip component 15.

  Further, even if the solder paste is directly extruded to the side of the chip component 15, the solder paste is drawn into the side solder introduction groove 28, and therefore, the solder paste may be extruded to the side of the chip component 15. This prevents the generation of solder balls.

  Such a configuration of the lands 22 on the circuit board 20 can be dealt with by simply changing the screen printing range of the solder resist 23 and changing the shape of the screen printing plate. In addition, when apply | coating a soldering resist by the spray coat method, it can respond by changing the pattern shape of a mask. Therefore, even if the solder introduction grooves 27 and 28 are formed, the extra steps are not increased and the cost is not increased. Further, in the structure of the present embodiment, since the solder paste 33 is not extruded to the side of the chip component 15 in particular, the dimensions in the width direction of the land 22 are set in the same direction as the electrodes 16 of the chip component 15 as shown in FIG. 2B. The dimension can be almost the same as the dimension. That is, the size of the land 22 in the width direction on the circuit board 20 can be minimized, which leads to effective use of the space on the circuit board 20 and enables high-density mounting.

  Although the present invention has been described above with reference to the illustrated embodiments, the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the technical idea of the invention included in the present application. For example, various changes can be made to the dimensions of the chip component 15 in the above embodiment, the dimensions of the lands 22 on the circuit board 20, or their specific shapes. Also, various changes can be made to the width and depth of the solder introduction grooves 27 and 28 formed by printing the solder resist 23 from the periphery of the land 22 in accordance with the purpose. Similarly, the design of the height of the wall portion 30 can be changed in accordance with the purpose.

  The present invention can be used for assembling an electronic circuit device by mounting chip components on a circuit board.

It is a principal part disassembled perspective view which shows mounting of the chip components with respect to a circuit board. It is a top view which shows arrangement | positioning of the land on a circuit board. It is sectional drawing of the axial direction of the chip component which shows the mechanism of generation | occurrence | production of a solder ball. It is sectional drawing of the width direction of the chip component which shows the mechanism of prevention of generation | occurrence | production of a solder ball. It is principal part sectional drawing which shows mounting of the chip component with respect to the conventional circuit board. It is a top view which shows arrangement | positioning of the land on the circuit board. It is sectional drawing of the axial direction of the chip component which shows the mechanism of generation | occurrence | production of the solder ball on the conventional circuit board. It is sectional drawing of the width direction of the chip component which shows the mechanism of generation | occurrence | production of the solder ball on the conventional circuit board.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Chip component, 2 ... Circuit board, 3 ... Electrode, 4 ... Land, 5 ... Solder resist, 6 ... Solder paste, 7 ... Solder ball, 8 ... Solder, 15 ... Chip component, 16 ... Electrode, 20 ... Circuit board 21 ... conductor pattern, 22 ... land, 23 ... solder resist, 27, 28 ... solder introduction groove, 30 ... wall, 33 ... solder paste, 34 ... solder fillet, 35 ... solder

Claims (8)

In a circuit board having lands for soldering electrodes at both ends of a chip component,
From the edge facing the land on the opposite side of the land to the side edge, the solder introduction groove is formed in a substantially U shape,
A circuit board, wherein a wall portion facing an end face of the electrode of the chip component is formed in the vicinity of the edge farthest from the land opposite to the land.   The solder introduction groove is formed by forming a solder resist apart from an edge and a side edge opposite to the land on the opposite side of the land, and an edge of the land and an edge of the solder resist The circuit board according to claim 1, wherein the circuit board is a groove formed of a concave portion formed therebetween.   The wall portion is an edge of a solder resist formed on the land so as to face an end surface of an electrode of the chip component, and has a height corresponding to the thickness of the solder resist. The circuit board according to claim 1.   The circuit board according to claim 1, wherein a width of the land is substantially equal to a width of an electrode of the chip component. In the chip component soldering structure in which the electrodes on both ends of the chip component are respectively soldered to lands on the circuit board,
From the edge on the center side of the chip part to the side edge of the land, the solder introduction groove is formed in a substantially U shape, and the molten excess solder is drawn into the solder introduction groove,
A chip part, wherein a wall part is formed on the land so as to face an end face of the electrode of the chip part, and a solder fillet is formed by molten solder so as to extend from the wall part to the end face of the electrode. Soldering structure.   6. The chip part soldering structure according to claim 5, wherein a width of the solder introduction groove is in a range of 30 to 100 [mu] m.   6. The chip component soldering structure according to claim 5, wherein a depth of the solder introduction groove is in a range of 10 to 100 [mu] m. 6. The chip part soldering structure according to claim 5, wherein a height of the wall portion is in a range of 10 to 100 [mu] m.

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