JP2004335657A - Land pattern for surface mount of footprint electrode chip components, front side mounted method, buffer substrate, and electronic omponents - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent tilting of a chip component in the case of solder packaging of a footprint electrode chip component of a light receiving element or the like on a substrate side, and further maintain highly efficient property of the chip components. <P>SOLUTION: A land pattern 40 for surface mount is formed in top view of a buffer substrate 30 to which a footprint electrode 11 of the footprint electrode chip component 10 is joined with soldering. The land pattern 40 is constituted of lands 41 which are plurally divided and arranged in the longitudinal direction of the footprint electrode 11. After the footprint electrode 11 of the footprint electrode chip component 10 is soldered to the land pattern 40 for surface mount, a terminal electrode 31 of the buffer substrate 30 is soldered to a substrate. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a surface mounting land pattern for surface mounting a bottom electrode chip component such as a light receiving element (optical sensor chip component) on a substrate, a surface mounting method using the land pattern, a buffer substrate, and an electronic component. It is.
[0002]
[Prior art]
FIG. 8 is a mounting connection state diagram showing a general mounting connection of a two-terminal chip component (conventional square chip component) having external electrodes at both ends to a land pattern on a circuit board. The external electrodes 2 formed on both ends of the chip are integrally formed with five surfaces including an end surface and a peripheral surface thereof, and Sn plating or solder plating is formed on the surface. The external electrodes 2 are mounted on the lands 4 of the substrate 3 and connected to the lands 4 by soldering. At this time, the lands 4 were designed to be equal to or larger than the external electrodes 2, and the chip component 1 was connected to the circuit board 3 by forming solder fillets 5 each having the external electrodes 2 and the lands 4 on one side. .
[0003]
However, since the land 4 of the circuit board 3 is designed to be larger than the chip component 1, the distance between adjacent chips cannot be designed to be small, and a high-density mounting board cannot be designed.
[0004]
In recent years, components having external electrodes provided only on the bottom surface of the chip, such as bottom electrode chip components, have emerged, and flip chips (semiconductor chips) having bump-shaped terminal electrodes on the bottom surface are known.
[0005]
Furthermore, the bottom electrode chip component such as a light receiving element has a rectangular parallelepiped rectangular chip shape, has a bottom electrode of two terminals on the bottom surface as an external electrode, and has an external electrode surface only on the bottom surface, and electrodes on the top, side, and end surfaces. It has no surface, and unlike the flip chip, the bottom electrode is a flat surface.
[0006]
The following Patent Documents 1 and 2 show soldering structures of chip components having external electrodes (side electrodes) at both ends.
[0007]
[Patent Document 1] JP-A-3-77394 [Patent Document 2] JP-A-5-21260
Patent Document 1 shows a structure in which a soldering pad is divided by a solder resist. However, this does not solve the problem of mounting the bottom electrode chip component such as the light receiving element on the substrate surface (for example, a problem such as occurrence of inclination).
[0009]
Patent Document 2 discloses a method in which a solder forming surface is formed in a bottom surface region of an external electrode formed at both ends of a chip component, and a periphery thereof is used as a solder exclusion surface, so that a solder fillet is not formed. This aims at high-density mounting. Again, this does not solve the problem of mounting the bottom electrode chip component such as a light receiving element on the substrate surface.
[Problems to be solved by the invention]
The present invention is directed to mounting a bottom electrode chip component such as a light receiving element having a flat bottom electrode as described above. The following presents problems in mounting the bottom electrode chip component. State.
[0011]
Assignment 1
The distance between adjacent components can be reduced by the bottom electrode chip component, and the light receiving surface can be increased for the chip component (light receiving element) that detects light, and the cost is low, but the flat bottom electrode without bumps etc. is formed on the bottom electrode. When mounted on a circuit board as in the past, the bottom electrode chip component having the above is easily connected to the circuit board in an inclined state. If it is a light receiving element for detecting light, it is inevitable that it affects the chip functional characteristics.
[0012]
The reason why the bottom electrode chip component is easily mounted in an inclined state will be described with reference to FIG. 9A is a bottom view of a bottom electrode chip component having two terminals, and FIG. 9B is a side view of FIG. 9A as viewed from the direction indicated by the arrow A. FIG. Is shown. Unlike the conventional chip components having external electrodes at both ends as shown in these figures, the connection portion with the circuit board is located only on the bottom surface of the chip component, and there is no solder fillet or the like on the side surface for holding the chip component ( (Not formed).
[0013]
FIG. 9C is a plan view showing the shape and arrangement of a conventional land 21 on the circuit board 20 on which the bottom electrode chip component 10 is mounted, and FIG. It is explanatory drawing (side view) at the time of mounting the electrode chip component 10, and from these figures, the printing area of the flat bottom electrode 11 of the bottom electrode chip component 10, the land 21 of the circuit board 20, and the solder paste 22 is conventionally shown. It turns out that they are equivalent.
[0014]
Then, after the bottom electrode chip component 10 is placed on the circuit board surface, the circuit board 20 and the bottom electrode chip component 10 are connected and fixed by passing through a reflow furnace, as shown in FIG. 2, the bottom electrode chip component 10 is connected to the circuit board 20 at an angle. This is because the solder tends to agglomerate to the center of the land 21 due to the surface tension of the solder paste 22 in the molten state. The larger the amount of solder paste with respect to the land area, the more likely it is to be hemispherical. Accordingly, as shown in FIG. 9 (E), the bottom electrode chip component 10 has poor parallelism during reflow, and is connected to the substrate surface at an angle.
[0015]
Assignment 2
In the case of the bottom electrode structure, the bending resistance tends to be weaker than that of the normal side electrode structure, and there is a problem that it cannot withstand excessive bending stress. That is, the bonding strength in the shear test after bending the substrate after mounting the substrate with solder is low.
[0016]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION In view of the foregoing, it is a first object of the present invention to prevent the occurrence of tilt of a chip component when soldering and mounting the bottom electrode chip component on a substrate side, and to maintain high functional characteristics of the chip component. An object of the present invention is to provide a land pattern for surface mounting of a bottom electrode chip component, a surface mounting method, a buffer substrate, and an electronic component.
[0017]
A second object of the present invention is to provide a surface mounting method for a bottom electrode chip component, which can improve the shortage of component bending stress after soldering and mounting the bottom electrode chip component on a substrate side and can secure a stable bonding force. It is to provide a board and an electronic component.
[0018]
Other objects and novel features of the present invention will be clarified in embodiments described later.
[0019]
[Means for Solving the Problems]
In order to achieve the above object, a land pattern for surface mounting of a bottom electrode chip component according to the first aspect of the present invention is formed on an upper surface of a substrate to which a bottom electrode of the bottom electrode chip component is joined by soldering. And a land that is divided into a plurality of lands in the longitudinal direction of the bottom electrode.
[0020]
The land pattern for surface mounting of the bottom electrode chip component according to the invention of claim 2 of the present application is characterized in that, in claim 1, a gap between the plurality of divided lands is 0.2 mm or more. .
[0021]
A land pattern for surface mounting of a bottom electrode chip component according to a third aspect of the present invention is characterized in that, in the first or second aspect, the lands are interconnected by a narrow connecting portion.
[0022]
In the land pattern for surface mounting of the bottom electrode chip component according to the invention of claim 4 of the present application, in claim 1, 2, or 3, the land has a shape not protruding from the contour of the bottom electrode chip component. I have.
[0023]
According to a fifth aspect of the present invention, there is provided a method for surface mounting a bottom electrode chip component, comprising using the substrate having the land pattern for surface mounting according to any one of the first, second, third or fourth aspect, It is characterized by being soldered to the mounting land pattern.
[0024]
A surface mounting method of a bottom electrode chip component according to the invention of claim 6 of the present application uses a buffer substrate having the surface mounting land pattern of claim 1, 2, 3 or 4 and having terminal electrodes on the side surfaces. After soldering the bottom electrode of the component to the land pattern for surface mounting, the terminal electrode of the buffer board is soldered to the circuit board.
[0025]
The buffer board according to the invention of claim 7 of the present application is characterized in that it has the surface mounting land pattern of claim 1, 2, 3, or 4 on the upper surface and has terminal electrodes on the side surfaces.
[0026]
The buffer substrate according to the invention of claim 8 of the present application is characterized in that, in claim 7, the terminal electrode has a divided through hole structure penetrating from the upper surface to the lower surface.
[0027]
The electronic component according to the invention of claim 9 of the present application is characterized in that the bottom electrode of the bottom electrode chip component is joined to the surface mounting land pattern on the upper surface of the buffer substrate of claim 7 or 8 by soldering.
[0028]
An electronic component according to a tenth aspect of the present invention is the electronic component according to the ninth aspect, wherein the bottom electrode chip component is a light receiving element, and an inclination of a light receiving surface of the light receiving element with respect to an upper surface of the buffer substrate is within 5 °. Features.
[0029]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of a land pattern for surface mounting of a bottom electrode chip component, a surface mounting method, a buffer substrate, and an electronic component according to the present invention will be described with reference to the drawings.
[0030]
FIGS. 1 to 3 show an embodiment of the present invention, showing a land pattern for surface mounting of a bottom electrode chip component, a surface mounting method and a buffer substrate using the same, and an electronic component using the buffer substrate. In these figures, 10 is a two-terminal bottom electrode chip component such as a light receiving element, 30 is a buffer substrate (interposer) provided with required electrodes on an insulating plate such as a resin, and the bottom electrode chip component 10 is shown in FIG. As shown in (A) and (B), the flat bottom electrode 11 has two terminals.
[0031]
On the upper surface of the buffer substrate 30 to which the bottom electrode 11 of the bottom electrode chip component 10 is joined by soldering, a surface mounting land pattern 40 of the bottom electrode chip component is formed as shown in FIGS. The land pattern 40 serves both as an electrical connection with the bottom electrode 11 on the chip component side and for reinforcing the chip connection, and corresponds to each bottom electrode 11 in the longitudinal direction (X direction in FIG. 1). It is composed of a plurality of (two in the illustrated case) conductor lands 41 which are divided and arranged. In this manner, by designing the land pattern shape and arrangement in which the land 41 is divided and arranged, and the solder paste printing area (corresponding to the land area), the amount of solder paste per land can be reduced, and the thickness can be suppressed. Consideration is given to the parallelism by supporting at two places with respect to one side of the bottom electrode (so as to prevent chip component inclination from occurring).
[0032]
The gap between the lands 41 divided into a plurality of pieces is 0.2 mm or more, which is an interval at which the solder can be clearly separated and formed. Further, in order to achieve high-density mounting and to prevent displacement during solder reflow, the land 41 has a shape and an arrangement which does not protrude from the contour of the bottom electrode chip component 10 (does not protrude from the contour of the bottom electrode 11). Is even more preferred).
[0033]
As shown in FIGS. 2C and 2D, a terminal electrode 31 having a divided through-hole structure penetrating from the upper surface to the lower surface of the substrate 30 is formed on the side surface of the buffer substrate 30. The terminal electrodes 31 partially extend to both ends of the bottom surface of the buffer substrate 30 as shown in FIG. Although not shown, one terminal electrode 31 is connected to a land 41 on one side with a predetermined wiring pattern, and the other terminal electrode 31 is connected to a land 41 on the other side with a predetermined wiring pattern.
[0034]
As a configuration of the bottom electrode chip component 10 and the buffer substrate 30 for surface mounting the same as described above, a land pattern 40 composed of a plurality of conductor lands 41 arranged in the longitudinal direction corresponding to each bottom electrode 11 is provided. Then, the solder paste is printed on the substrate and passed through a reflow furnace to connect the land pattern 40 on the buffer substrate 30 side and the bottom electrode 11 of the bottom electrode chip component 10. At this time, since the solder 45 is separately formed for each land 41, after the reflow, the bottom electrode chip component 10 is mounted while being kept parallel to the buffer substrate 30, as shown in FIG. . Thereby, the electronic component 50 in which the bottom electrode chip component 10 is integrated with the buffer substrate 30 is obtained as shown in FIG.
[0035]
The electronic component 50 can be surface-mounted by soldering using the terminal electrodes 31 of the buffer substrate 30 as a chip component having normal side electrodes on land patterns of various circuit boards. At this time, a solder fillet is formed on the terminal electrode 31 having a divided through-hole structure provided on the side surface of the buffer substrate 30 and the conductor land on the circuit substrate side, and is connected on the side surface of the buffer substrate. Therefore, the bending stress received from the circuit board concentrates on the fillet forming portion between the circuit board and the buffer board 30, and the influence on the chip component 10 on the buffer board is reduced.
[0036]
Here, the mechanism of parallel fixation by the side surface divided through hole structure will be additionally described. Usually, the solder paste removes an oxide film at the solder connection portion by the flux, and makes the solder easily wet and spread. Therefore, the flux of the solder paste printed on the circuit board removes the oxide film from the bottom portion of the buffer substrate 30 and the through-hole portion on the side surface, and the solder spreads to each. When the solder is melted, it gradually wets up the through-holes on the side surfaces, but when it is hardened, a force acts in the direction of shrinkage (a force acts to unite). This is called a surface tension action. At this time, a downward force acts on the solder in the side surface divided through-hole portion so as to form a single mass by the surface tension action between the solder on the bottom portion and the solder on the bottom portion. It will be connected in parallel by sinking into the upper solder. This phenomenon is similar to the formation of a fillet such as a normal chip capacitor (two-pole terminal).
[0037]
FIG. 4 shows a modified example of the land pattern 40 formed on the upper surface of the buffer substrate 30. FIG. 4A shows a substantially C-shaped land 41 which is divided into a plurality of parts in the longitudinal direction of the bottom electrode. (B), each land 41 has an elliptical or elliptical shape, FIG. (C) shows each land 41 is circular, and (D) shows a bottom electrode. The rectangular subdivision type land pattern which has the land 41 divided | segmented into two or more in the longitudinal direction and also into two or more in the short direction is shown. Also in this rectangular subdivision type land pattern, the slit width used for division is 0.2 mm or more. In any case, the bottom electrode chip component can be surface-mounted while maintaining parallelism with the buffer substrate.
[0038]
According to the present embodiment, the upper surface of the bottom electrode chip component and the upper surface of the circuit board are maintained by maintaining the parallelism between the bottom electrode chip component 10 and the buffer substrate 30 and maintaining the parallelism between the buffer substrate 30 and the circuit substrate. Can be maintained in parallel, so that when the chip component 10 is a light receiving element, the inclination of the chip component is reduced, so that the spectral sensitivity change rate can be reduced and the function characteristics can be set to be excellent.
[0039]
FIG. 5 is a graph showing the relationship between the spectral sensitivity and the inclination after mounting the component on the mounting board when the bottom electrode chip component is a light receiving element. However, the inclination angle is an angle formed by the upper surface (light receiving surface) of the chip component with respect to the mounting substrate surface, and is 0 ° when both are parallel. The spectral sensitivity gradually decreases at an inclination of about 10 ° or more in the measured value, but attenuates at 5 ° or more in the calculated value. Therefore, it is necessary to suppress the inclination to 5 ° or less from the product variation and the calculated value on the desk (specified in the mounting specification of the light receiving element).
[0040]
FIG. 6 shows inclination measurement data after the bottom electrode chip component 10 is mounted on a substrate on which a land pattern for surface mounting is formed. However, Samples A and B are examples of an embodiment using a substrate having a divided land pattern having the shape shown in FIG. 4A. Sample A is soldered by eutectic solder, and Sample B is soldered by lead-free solder. Samples C and D are comparative examples using a substrate having a general non-divided land pattern shown in FIG. 9C. Sample C is eutectic solder, and sample D is lead-free solder. Are respectively shown. However, the number of samples was 10 each.
[0041]
It can be seen from the tilt measurement data of FIG. 6 that in the divided land patterns according to the embodiment, the tilt could all be suppressed to 5 ° or less in the eutectic solder. Even with lead-free solder having a large surface tension, it can be suppressed to about 5 ° (clearing the tilt value of the light-receiving element mounting specification). On the other hand, in the comparative example using the undivided land pattern, the inclination is much larger than 5 °.
[0042]
Therefore, when the bottom electrode chip component 10 is a light receiving element, the split land pattern of the present embodiment has an effect of surface mounting without attenuation of the spectral sensitivity due to the inclination, and by suppressing the inclination to 5 ° or less, Light receiving efficiency can be improved. Also, it has been confirmed that the inclination can be further reduced by increasing the number of divisions.
[0043]
FIG. 7 shows comparison data of a bending strength test of the electronic component (the bottom electrode chip component 10 mounted on the buffer substrate 30) according to the present embodiment with a conventional product (without the buffer substrate). Several parts were surface-mounted and connected to a 100 mm × 40 mm mounting board by soldering, and a force of 50 N was applied for 5 seconds to apply a bending stress to the mounting board (however, a pin tip for applying bending stress was applied). The radius of curvature was 10 mm, and the pushing speed was 0.5 mm / sec.). Thereafter, the shear strength (N) was determined by plotting the shear strength of the electronic component at each distance from the bending stress application point (however, the shear strength was measured by fixing the mounting board and mounting the mounting board against the buffer board). By applying a force from the probe in a direction parallel to.
[0044]
It can be seen that the conventional product without the buffer substrate deteriorates to a standard value of about 5N near the point where the bending stress is applied, against the initial shear strength of 60N.
[0045]
On the other hand, it can be seen that the electronic component according to the present embodiment in which the bottom electrode chip component is mounted on the buffer substrate can maintain the strength without deterioration even in the vicinity of the bending stress application point at the initial about 40 N (bottom electrode Insufficient bending stress of the joints at the joint is improved.) Here, the initial value of the decrease in the shear strength is due to the fact that the connection area between the bottom electrode chip component and the buffer board is slightly reduced due to the division of the land, but there is no problem since the standard value 5N is sufficiently satisfied. .
[0046]
Therefore, by maintaining the component orientation in parallel with the land pattern shown in the present embodiment, an electronic component mounting machine can automatically mount the component on a circuit board and can also invent a component structure that improves bending stress.
[0047]
The land pattern for surface mounting may be formed by dividing the conductor pattern itself to form a land. However, a solder resist (resin paste) or the like may be formed on a conductor formed in the same area as the bottom electrode of the bottom electrode chip component. The land may be formed by dividing the shape and size on the surface.
[0048]
Although the embodiments of the present invention have been described above, it will be obvious to those skilled in the art that the present invention is not limited to the embodiments and various modifications and changes can be made within the scope of the claims.
[0049]
【The invention's effect】
As described above, the land pattern for surface mounting of the bottom electrode chip component according to the present invention is composed of lands that are divided into a plurality of pieces in the longitudinal direction of the bottom electrode of the bottom electrode chip component and are arranged after solder reflow. Of the bottom electrode chip component with respect to the substrate can be prevented, and the bottom electrode chip component can be surface-mounted on the substrate while maintaining the parallelism between the bottom electrode chip component and the substrate.
[0050]
Also, the surface mounting method of the bottom electrode chip component according to the present invention includes the step of surface mounting the bottom electrode chip component on a substrate using the surface mounting land pattern including the plurality of divided lands. Thus, the occurrence of the inclination can be prevented.
[0051]
By using the land pattern for surface mounting and the surface mounting method using the land pattern, when the bottom electrode chip component is a light receiving element, the inclination failure is reduced and the yield is improved in the product of the light receiving element mounted substrate. Can be.
[0052]
Further, a buffer board having the surface mounting land pattern composed of the plurality of divided lands and having side terminal electrodes is used, and the bottom electrode chip component is mounted on the circuit board via the buffer board. Thus, the bottom electrode chip component can be converted into the structure of the side electrode chip, so that the same bonding strength as that of the side electrode chip component can be secured.
[0053]
If the structure of the electronic component is such that the bottom electrode of the bottom electrode chip component is joined to the surface mounting land pattern on the top surface of the buffer substrate by soldering, the bottom substrate electrode chip component is provided because the buffer substrate has side terminal electrodes. Can be mounted on the circuit pattern for the side electrode chip.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view showing a land pattern for surface mounting of a bottom electrode chip component, a surface mounting method and a buffer substrate using the same, and an electronic component using the buffer substrate, according to an embodiment of the present invention. .
2 (A) is a plan view, FIG. 2 (B) is a front view, FIG. 2 (C) is a bottom view, FIG. 2 (D) is a side view, and FIG. (E) is a side sectional view.
FIG. 3 is a plan view showing an example of a land pattern for surface mounting according to the embodiment.
FIG. 4 is a plan view showing a modified example of a surface mounting land pattern that can be used in the embodiment.
FIG. 5 shows the relationship between the spectral sensitivity when the bottom electrode chip component is a light receiving element (optical sensor chip component) and the angle after mounting the component (the angle is 0 ° when the top surface of the chip component and the substrate surface are parallel). It is a graph.
FIG. 6 shows a case in which a bottom electrode chip component is mounted on a substrate on which a surface mounting land pattern having a divided configuration shown in FIG. 4A is formed, and a conventional case in which a bottom electrode chip component is mounted on an undivided land pattern. 5 is a graph showing the respective tilt measurement data.
FIG. 7 is a graph comparing the results of measuring the component shear strength after applying a bending stress to the mounted circuit board in the case of the present embodiment using the buffer substrate and in the case of the conventional product not using the buffer substrate.
FIG. 8 is a front view showing a mounting connection state of a general two-terminal chip component having external electrodes at both ends.
9A and 9B are bottom electrode chip components of two terminals such as a light receiving element, wherein FIG. 9A is a bottom view, FIG. 9B is a view of the bottom electrode as viewed from an arrow A, and FIG. A plan view of a conventional land pattern for surface mounting, (D) is an exploded side view when a bottom electrode chip component is surface-mounted on the conventional land pattern, and (E) is a bottom electrode chip component on the conventional land pattern. It is a side view which shows the inclination state at the time of mounting by solder reflow.
[Explanation of symbols]
1, 10 Chip component 2 External electrode 3, 20 Circuit board 4, 21, 41 Land 5 Fillet 11 Bottom electrode 22 Solder paste 30 Buffer board 31 Terminal electrode 40 Land pattern 45 Solder 50 Electronic component

Claims (10)

In the land pattern for surface mounting of the bottom electrode chip component formed on the upper surface of the substrate to which the bottom electrode of the bottom electrode chip component is joined by soldering,
A land pattern for surface mounting of a bottom electrode chip component, comprising lands divided into a plurality of parts in a longitudinal direction of the bottom electrode. The land pattern for surface mounting of a bottom electrode chip component according to claim 1, wherein a gap between the plurality of divided lands is 0.2 mm or more. The land pattern for surface mounting of a bottom electrode chip component according to claim 1 or 2, wherein the lands are connected to each other by a narrow connecting portion. The land pattern for surface mounting of a bottom electrode chip component according to claim 1, wherein the land has a shape not protruding from an outline of the bottom electrode chip component. 5. A bottom electrode chip component, wherein the bottom electrode of the bottom electrode chip component is soldered to the land pattern for surface mounting using the substrate having the land pattern for surface mounting according to claim 1, 2, 3, or 4. Surface mounting method. After soldering the bottom electrode of the bottom electrode chip component to the surface mounting land pattern using a buffer substrate having the surface mounting land pattern of claim 1, 2, 3, or 4 and having a terminal electrode on a side surface, A surface mounting method for a bottom electrode chip component, wherein a terminal electrode of the buffer board is soldered to a circuit board. 5. A buffer substrate having the land pattern for surface mounting according to claim 1, 2, 3, or 4 on an upper surface and terminal electrodes on side surfaces. The buffer substrate according to claim 7, wherein the terminal electrode has a divided through-hole structure penetrating from the upper surface to the lower surface. An electronic component, wherein the bottom electrode of the bottom electrode chip component is joined to the land pattern for surface mounting on the top surface of the buffer substrate according to claim 7 by soldering. 10. The electronic component according to claim 9, wherein the bottom electrode chip component is a light receiving element, and an inclination of a light receiving surface of the light receiving element with respect to an upper surface of the buffer substrate is within 5 degrees.

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