JPH0936527A - Electronic component, manufacture of electronic component and soldering of board and electronic component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inhibit the generation of a solder bridge due to the shift of printing of a solder paste at the time of packaging of an electronic component, protrusion of the solder paste or the like by a method wherein partial protrusions are provided on the bonding surface of an electrode. SOLUTION: An electronic component 6 is a surface packaging component, such as an SOP and a QFP, and is provided with gas winged lead terminals 4. A protrusion 8 of a diameter smaller than the width of the terminals 4 is provided on one part of each bonding surface of these lead terminals 4. In the soldered terminals 4, the protrusions 8 of the terminals 4 are made contact with a board electrode 2, whereby as gaps of a constant height are respectively formed between the terminals 4 and the electrode 2, solders 3 are respectively held in the gaps to bond the terminals 4 to the electrode 2. Accordingly, the thickness of the solders 3, which bond the terminals 4 to the electrode 2, becomes constant and an irregularity in the bonding strength of the solders is decreased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic component, a method for manufacturing the electronic component, a substrate, and a soldering method for the electronic component. More specifically, the present invention is mainly characterized by a technique for soldering an electrode of an electronic component to an electrode of a substrate.

[0002]

2. Description of the Related Art Various mounting methods are used for mounting electronic components on a printed wiring board. For example, FIG.
As shown in FIG. 1A, after a solder paste 3a is screen-printed on a substrate electrode 2 provided on a substrate 1 such as a printed wiring board, a substrate coated with the solder paste 3a as shown in FIG. 1B. The lead terminal 4 of the electronic component is placed on the electrode 2 and temporarily fixed, and the lead terminal 4 of the electronic component is reflowed by reflowing the solder paste 3a.
Soldered to.

[0003]

However, in the electronic component thus soldered, as shown in FIG.
As shown in (b) and FIG. 3 (c), a solder bridge 5 may occur between adjacent soldering portions.

The main causes of the solder bridge 5 may be defective printing and protrusion of the solder paste during mounting.

Of these, a printing defect is a printing defect such as a printing shift as shown in FIG. 2A when the solder paste 3a is printed on the substrate electrode 2.
As shown in (b), the solder 3 protruding between the substrate electrodes 2 when the solder paste 3a is melted becomes a solder bridge 5. In particular, in consideration of the fact that the board electrodes 2 have a narrower pitch in recent years due to the increase in the number of pins of electronic parts and the miniaturization of wiring, the solder bridge 5 caused by this printing failure is always printed with misalignment. It is difficult to achieve good print quality, and printability will continue to deteriorate.

Next, the protrusion of the solder paste 3a during mounting means the solder paste 3a as shown in FIG. 3 (a).
Is printed correctly, but if the solder paste 3a is applied too thickly on the substrate electrode 2 or if too much pressure is applied when mounting an electronic component, the pressure applied to the lead terminals 4 may cause the problem shown in FIG. As shown in FIG. 3, the solder paste 3a protrudes from between the substrate electrode 2 and the lead terminal 4, and in this case as well, the melted solder 3 is connected to each other and the solder paste 3a is connected.
The solder bridge 5 is formed as shown in (c). In order to prevent such a protrusion of the solder paste 3a, the condition (pressure condition) when mounting the electronic component is adjusted, but the solder paste 3a and the lead terminal 4 are mounted at the time of mounting.
Since it is necessary to closely adhere to each other, a certain mounting pressure is required, and it is quite difficult to prevent the solder paste 3a from protruding during mounting.

The present invention has been made in view of the above-mentioned drawbacks of the conventional examples. In the invention described in claims 1 to 7, the solder paste at the time of mounting is provided by providing protrusions on the bonding surfaces of the electrodes. Another object of the present invention is to provide an electronic component capable of suppressing the occurrence of a solder bridge due to misregistration of printing, the protrusion of solder paste, or the like.

According to the eighth to tenth aspects of the present invention, the protrusions that do not melt during soldering are provided on the electrodes, so that the solder paste is misprinted during mounting or the solder paste is squeezed out to cause solder bridges. It is to provide a substrate capable of suppressing the above.

The invention described in claims 11 to 13 is to provide a method for manufacturing the electronic component described in claim 1.

A fourteenth aspect of the present invention is to provide a method for soldering the electronic component according to the first aspect to a substrate.

A fifteenth aspect of the present invention is to provide a method for soldering an electronic component to the board according to the eighth aspect.

[0012]

An electronic component according to a first aspect of the present invention is characterized in that a partial projection is provided on a bonding surface of an electrode.

When such a protrusion is provided on the bonding surface of the electrode of the electronic component, as in the method of soldering an electronic component according to claim 14, the electrode is attached after the solder is attached to the surface of the electrode of the substrate. It is possible to bring the electrode of the electronic component and the electrode of the substrate to face each other by bringing the protrusion of the electronic component having a partial protrusion on the joint surface thereof into contact with the electrode of the substrate, and to melt and then cure the solder.

Therefore, when the electrode of the electronic component is overlaid on the electrode of the substrate, a gap having a constant height is formed between the two electrodes by the projection, and the solder is held in the gap to join the two electrodes together. Therefore, the thickness of the solder joining the electrodes is constant, and the variation in the joining strength is reduced.

Further, when the solder paste is melted and the electrodes are joined together, the gap between the electrodes is kept constant by the projections, so that the molten solder is not pushed out by the mounting pressure of the electronic component, It is possible to prevent a solder bridge from being generated between adjacent electrodes.

Further, even if a solder bridge occurs between the adjacent electrodes, the melted solder is absorbed in the gap between the electrodes, so that the solder bridge is absorbed and broken between the opposing electrodes, and the solder bridge is broken. To be removed.

According to a second aspect of the present invention, in the electronic component according to the first aspect, the protrusion is smaller than the width of the electrode.

If the protrusion is made smaller than the width of the electrode, the solder melted by the protrusion is not obstructed from spreading to the entire joint surface of the electrode of the electronic component, and the entire joint surface can be wetted so that the soldering strength is high. And reliability can be improved.

According to a third aspect of the present invention, in the electronic component according to the first or second aspect, the electrodes are lead terminals.

As the electrode of the electronic component, for example, one using a lead terminal as in the embodiment can be mentioned, but the invention is not limited to the lead terminal and a leadless electrode may be used.

According to a fourth aspect of the present invention, in the electronic component according to the first or second aspect, a plurality of the protrusions are provided at one joint of the electrode.

By providing a plurality of protrusions, the electrode of the electronic component can be brought into stable contact with the electrode of the substrate.

According to a fifth aspect of the present invention, in the electronic component according to the first or second aspect, the protrusion is a press-molded portion.

A method of manufacturing an electronic component according to claim 11 is
A method for manufacturing the electronic component according to claim 1, wherein a protrusion is partially provided on the bonding surface of the electrode by performing press working.

The sixth aspect of the present invention is characterized in that the protrusion is made of a conductor.

A method of manufacturing an electronic component according to a twelfth aspect,
The method for manufacturing an electronic component according to claim 1, wherein a protrusion is provided on the bonding surface of the electrode by depositing a conductive material on the bonding surface of the electrode.

According to a seventh aspect of the present invention, in the electronic component according to the first or second aspect, the protrusion is formed of an insulator.

A method of manufacturing an electronic component according to a thirteenth aspect,
The method for manufacturing an electronic component according to claim 1, wherein a protrusion is provided on the bonding surface of the electrode by depositing an insulating material on the bonding surface of the electrode.

The protrusion may be a press-molded portion formed by pressing an electrode as described in claim 5.
It may be made of a conductor (for example, metal plating other than solder) as described in (1) or may be made of an insulator (for example, resin or resist) as described in claim 7. However, the method of forming the protrusions, the material, and the like are not particularly limited as long as they have a melting temperature higher than the soldering temperature.

The substrate of the present invention according to claim 8 is characterized in that projections which are not melted during soldering are provided on the electrodes of the substrate.

Here, the fact that the solder does not melt at the time of soldering means that it has a melting temperature higher than the melting temperature of the solder to be used.

When such a protrusion is provided on the electrode of the substrate, the solder is attached to the electrode surface of the substrate having the protrusion on the electrode, as in the method for soldering an electronic component according to claim 15. After that, the electrode of the electronic component can be brought into contact with the protrusion of the substrate so that the electrode of the electronic component and the electrode of the substrate face each other, and the solder can be melted and then cured.

Therefore, when the electrode of the electronic component is superposed on the electrode of the substrate, a gap having a constant height is formed between the two electrodes by the projection, and the solder is held in the gap to join the two electrodes together. Therefore, the thickness of the solder joining the electrodes is constant, and the variation in the joining strength is reduced.

When the solder paste is melted and the electrodes are joined together, the gap between the two electrodes is kept constant by the protrusions, so that the molten solder is not pushed out by the mounting pressure of the electronic component. It is possible to prevent a solder bridge from being generated between adjacent electrodes.

Further, even if a solder bridge occurs between the adjacent electrodes, the melted solder is absorbed in the gap between the electrodes, so that the solder bridge is absorbed between the opposing electrodes and broken, and the solder bridge is broken. To be removed.

According to a ninth aspect of the present invention, in the substrate according to the eighth aspect, the protrusion is smaller than the width of the electrode.

If the projections are made smaller than the width of the electrodes, the projections do not prevent the molten solder from spreading over the entire bonding surface of the electrodes of the substrate, and the entire bonding surface can be wetted to improve the soldering strength. The reliability can be improved.

A tenth aspect of the present invention is characterized in that, in the substrate according to the eighth or ninth aspect, a plurality of the protrusions are provided at one joint of the electrode.

By providing a plurality of protrusions, the electrodes of the substrate can be brought into stable contact with the electrodes of the electronic component.

[0040]

FIG. 4 is a front view showing an electronic component 6 according to an embodiment of the present invention. This electronic component 6 is, for example, a SOP (Small outline package) or a QFP (Quad Fl).
A surface mount component such as an at package) having a gull-wing type lead terminal 4 (electrode of an electronic component).
A part of the joint surface 7 (lower surface) of the lead terminal 4 is provided with
As shown in FIG. 3, a protrusion 8 having a diameter smaller than the width of the lead terminal 4 is provided.

When mounting the electronic component 6 for surface mounting on the substrate 1 such as a printed wiring board, a solder paste is printed on the substrate electrode 2 previously formed on the surface of the substrate 1 by screen printing or the like. After that, an electronic component is placed on the substrate 1, the lead terminals 4 are superposed on the substrate electrodes 2 of the substrate 1, and the solder paste is melted by a reflow method or the like. Then, the lead terminal 4 can be soldered onto the substrate electrode 2 of the substrate 1 by hardening the molten solder 3.

In the thus soldered lead terminal 4, as shown in FIG. 6, the projection 8 of the lead terminal 4 abuts the substrate electrode 2 so that the lead terminal 4 is interposed between the lead terminal 4 and the substrate electrode 2. Since a gap having a constant height is formed, the solder 3 is held in the gap and the substrate electrode 2
And the lead terminal 4 are joined. Therefore, the thickness of the solder 3 joining the substrate electrode 2 and the lead terminal 4 becomes constant,
Variation in bonding strength is reduced.

Since the protrusion 8 is smaller than the width of the lead terminal 4, the protrusion 8 does not divide the joint surface 7 of the lead terminal 4 into two parts, and the melted solder 3 does not adhere to the joint surface of the lead terminal 4. The entire bonding surface 7 can be spread evenly over the entire bonding surface 7 and the soldering strength can be increased, so that the reliability of soldering can be improved. Further, the height of the protrusion 8 needs to be smaller than the printed film thickness of the solder paste printed on the substrate electrode 2. This is because if the height of the protrusions 8 is too large, the lead terminals 4 will not be wet with the melted solder 3 when the solder paste is melted. For example, if the lead terminal 4 has a thickness of 0.05 mm and the solder paste printed on the substrate electrode 2 has a printed film thickness of 0.15 mm, the thickness is preferably about 0.05 mm. Also, the protrusion 8 should not melt when soldered.
It is necessary that the melting temperature is higher than that of the solder 3 used.

Further, when the solder paste is melted and the lead terminal 4 is joined to the substrate electrode 2, the gap between the lead terminal 4 and the substrate electrode 2 is held at a constant height by the projection 8, so that The molten solder 3 is not extruded by the mounting pressure of the component, and the solder bridge 5 can be prevented from being generated between the adjacent substrate electrodes 2.

Further, even when the solder bridge 5 is generated between the adjacent soldering portions due to printing misalignment or the like, the lead terminal 4 is caused by the surface tension of the solder 3 when the solder is melted.
The molten solder 3 is sucked into the gap between the substrate electrode 2 and the substrate electrode 2 to remove the solder bridge 5. More specifically, when the solder bridge 5 is generated as shown in FIG. 7A, the internal pressure ΔP2 of the solder 3 at the solder bridge portion is expressed by the following equation (1) (RJ Kle
In Wassink, "Soldering in Electronics"; Nikkan Kogyo Shimbun). ΔP2 = −γ / R2 (1) Here, γ: surface tension of molten solder R2: radius of curvature of edge of solder bridge Further, as shown in FIG. 7B, between the lead terminal 4 and the substrate electrode 2. The internal pressure ΔP1 is expressed by the following equation (2) (same as “Soldering in Electronics”).
ΔP1 = −γ / R1 (2) Here, γ: surface tension of molten solder R1: radius of curvature ΔP1 and ΔP2 of the end face of the solder between the lead terminal and the substrate electrode are both negative, and the solder 3 is sucked in. However, since R1 << R2, | ΔP1 | >> | ΔP2
|, And the solder suction force between the lead terminal 4 and the substrate electrode 2 is predominantly stronger. For this reason, the solder 3 of the solder bridge 5 is connected to the lead terminal 4 and the substrate electrode 2.
It is sucked in between and the solder bridge 5 is cut and removed.

(Formation of Protrusion) FIG. 8 is a sectional view showing a method of forming the protrusion 8 on the lead terminal 4. In this lead terminal 4, when the lead terminal 4 is punched out from a hoop material or the like by a press machine, the lead terminal 4 is formed at the same time by press molding. In this way, if the projections 8 are formed by press molding,
The protrusion 8 can be formed at the same time as the lead terminal 4 is punched out, and the processing efficiency is improved.

FIG. 9 is a sectional view showing another protrusion 8 provided on the lead terminal 4. The lead terminal 4 is covered with a plating layer such as nickel plating, and the projection 8 is formed by increasing the thickness of a part of the plating film. The type of plating does not matter, but the solder 3 used
A material having a higher melting point and good wettability with the solder 3 is preferable. Although the lead terminal 4 is entirely plated in FIG. 9, only the protrusion 8 may be partially plated.

Other than the above, the projection 8 can be made of various materials and shapes. For example, although not shown, a metal protrusion 8 is brazed to the lead terminal 4, a resin, particularly a thermosetting resin protrusion 8 is attached to the surface of the lead terminal 4, a resist is applied to the surface of the lead terminal 4. Alternatively, the protrusions 8 formed by applying and baking a ceramic material may be used. However, when the protrusions 8 are formed of metal or resin,
The material needs to have a melting point higher than the melting point of the solder 3 to be used, and in the case of the projection 8 such as ceramic or thermosetting resin, the heat resistant temperature needs to be higher than the melting point of the solder 3. Further, the shape is not limited to the hemispherical projection 8 and may be a cylindrical projection 8 or a prismatic projection 8.

(Another Embodiment) FIG. 10 is a partially cutaway plan view and side view showing another embodiment of the lead terminal 4 of the electronic component. In this embodiment, a plurality of parallel lead terminals 4 are connected by a heat-resistant band-shaped film 9 such as polyimide. Therefore, it is possible to prevent the heights of the lead terminals 4 from varying and the pitches between the lead terminals 4 from varying, and the lead terminals 4 can be accurately arranged on the substrate electrode 2 when mounting an electronic component. .

(Number of Protrusions) Further, the number of the protrusions 8 is not limited to one as in the above embodiment, and a plurality of protrusions 8 may be provided on the joint surface 7 of the lead terminal 4. For example, in the lead terminal 4 shown in FIG. 11, two or three or more projections 8 are arranged in a vertical row, and in the lead terminal 4 shown in FIG. 12, two or three or more projections 8 are arranged in a horizontal row. Are arranged in. By providing a plurality of protrusions 8 in this way, the parallelism between the lead terminal 4 and the substrate electrode 2 is increased, and the soldering of the lead terminal 4 to the substrate electrode 2 is stabilized.

(Electronic Component) In the embodiment shown in FIG. 4, surface mount components such as SOP and QFP provided with gull-wing type lead terminals 4 are shown. The type and the like are not particularly limited, and can be used for general surface mount type.

For example, the electronic component 10 shown in FIG.
Is a leadless chip component, for example, a multilayer capacitor, and external electrodes 12 (electrodes of the electronic component) are formed on both ends of the electronic component body 11. As shown in FIG. 13B, a plurality of protrusions 8 are formed on the joint surface 7 (lower surface) of the external electrode 12, respectively. Then, when the chip-type electronic component 10 is placed on the substrate electrode 2, the electronic component 10 is placed on the substrate electrode 2 by the plurality of protrusions 8, and the bonding surface 7 of the external electrode and the substrate electrode 2 are A gap having a constant height (that is, a height equal to the height of the protrusion 8) is formed between the two, thereby preventing the generation of the solder bridge 5.

In addition, as shown in FIGS. 14 (a) and 14 (b),
Bare chip IC13 is TAB (Tape Automated Bondin
g) Electronic component 1 mounted on leaded film 14
5 is shown. A plurality of leads 16 (electrodes of electronic parts) provided on the film with leads for TAB 14 are connected by films 17 and 18, and the bare chip I
C13 is face down bonded to the inner end of the lead 16 (inner bonding). A protrusion 8 is provided on the bonding surface 7 of the lead 16 of the TAB leaded film 14, and a T having the bare chip IC 13 mounted thereon is formed.
When the AB leaded film 14 is mounted on the substrate 1, the projections 8 are placed on the substrate electrode 2 on which the solder paste is printed, and the leads 16 are soldered to the substrate electrode 2 by melting the solder paste ( Outer bonding). Even in such an electronic component, the solder bridge 5 can be prevented even if the pitch between the leads is reduced, and the reliability of soldering can be improved.

Although not shown, the protrusion 8 may be provided on the joint surface 7 of an electronic component such as PLCC (Plastic Leaded Chip Carrier) or SOJ having a J-bend type lead. In addition, a protrusion may be provided on a pad or the like of a leadless electronic component such as an LCC (Leadless Chip Carrier).

In the above embodiments, the protrusion 8 is provided on the bonding surface 7 of the substrate electrode 2 of the electronic component such as the lead terminal 4, but it is clear that the protrusion 8 may be provided on the substrate electrode 2 of the substrate 1. is there. For example, in the embodiment shown in FIG. 15, the lead terminals 4 are not provided with the protrusions 8 but the protrusions 8 made of a material having a melting point higher than that of the solder 3 are provided on the substrate electrodes 2 of the substrate 1.
Therefore, the protrusion 8 on the substrate electrode 2 forms a gap having a constant height between the lead terminal 4 and the substrate electrode 2, and the solder bridge 5 is prevented from being generated. However, in general, since the area or width of the substrate electrode 2 is larger than that of the joint portion of the lead terminal 4, it is easier to position the lead terminal 4 and the substrate electrode 2 by providing the protrusion 8 on the lead terminal 4. become.

The matters described regarding the projection 8 of the electronic component generally apply to the projection 8 provided on the substrate electrode 2 of the substrate 1. For example, as shown in FIG. 16 corresponding to the embodiment of FIG.
A plurality of protrusions 8 may be provided on the top.

Further, in the above description, the case where the electronic component is soldered by the reflow method has been described, but it goes without saying that the present invention is also effective when the electronic component is soldered by the flow method.

[Brief description of drawings]

1A and 1B are views showing a conventional method of soldering a lead terminal to a substrate electrode, wherein FIG. 1A is a plan view showing a substrate electrode printed with a solder paste, and FIG. 1B is soldered to the substrate electrode. FIG. 4 is a plan view showing a lead terminal that has been opened.

FIG. 2A is a plan view showing a substrate electrode in which a print displacement of a solder paste has occurred, and FIG. 2B is a plan view showing a soldering portion in which a solder bridge has occurred.

3A is a plan view showing a substrate electrode printed with a solder paste, FIG. 3B is a plan view showing a solder paste protruding from a lead terminal and a substrate electrode, and FIG. 3C is a solder having a solder bridge. It is a top view which shows an attachment part.

FIG. 4 is a front view showing an embodiment of an electronic component according to the present invention.

FIG. 5 is a perspective view showing a tip portion of a lead terminal of the electronic component of the above, which is turned upside down.

FIG. 6 is a diagram for explaining the operation of the electronic component of the above.

7 (a) and 7 (b) are explanatory views of the operation of the electronic component of the above.

FIG. 8 is an enlarged cross-sectional view showing a structure of a protrusion provided on a lead terminal.

FIG. 9 is an enlarged cross-sectional view showing the structure of another protrusion provided on the lead terminal.

10A is a plan view showing a tip portion of a lead terminal of an electronic component according to another embodiment of the present invention, and FIG. 10B is a side view thereof.

FIG. 11 is a perspective view showing an upside down end of a lead terminal of an electronic component according to still another embodiment of the present invention.

FIG. 12 is a perspective view showing an upside down end of a lead terminal of an electronic component according to still another embodiment of the present invention.

13A and 13B are respectively a side view and an upside down perspective view showing an electronic component according to still another embodiment of the present invention.

14A and 14B are respectively a schematic cross-sectional view and a plan view in a mounted state of an electronic component according to still another embodiment of the present invention.

FIG. 15 is a perspective view showing a substrate electrode and a lead terminal of a substrate according to still another embodiment of the present invention.

FIG. 16 is a perspective view showing a substrate electrode and a lead terminal of a substrate according to still another embodiment of the present invention.

[Explanation of symbols]

 1 Substrate 2 Substrate electrode 3 Solder 4 Lead terminal 5 Solder bridge 7 Bonding surface 8 Protrusion 12 External electrode of chip type electronic component 16 Lead of film with lead for TAB

Claims (15)

[Claims] 1. An electronic component, wherein a partial protrusion is provided on a bonding surface of an electrode. 2. The electronic component according to claim 1, wherein the protrusion is smaller than the width of the electrode. 3. The electrode is a lead terminal.
Or the electronic component described in 2. 4. The electronic component according to claim 1, wherein a plurality of the protrusions are provided at one joint of the electrode. 5. The electronic component according to claim 1, wherein the protrusion is a press-molded portion. 6. The electronic component according to claim 1, wherein the protrusion is made of a conductor. 7. The electronic component according to claim 1, wherein the protrusion is made of an insulator. 8. A substrate, characterized in that projections which are not melted during soldering are provided on the electrodes. 9. The substrate according to claim 8, wherein the protrusion has a width smaller than that of the electrode. 10. The substrate according to claim 8, wherein a plurality of the protrusions are provided at one joint of the electrode. 11. A method for manufacturing an electronic component according to claim 1, wherein a protrusion is provided partially on a bonding surface of the electrode by performing press working. Method. 12. A method for manufacturing an electronic component according to claim 1, wherein a protrusion is provided on the bonding surface of the electrode by attaching a conductive material to the bonding surface of the electrode. Electronic component manufacturing method. 13. The method for manufacturing the electronic component according to claim 1, wherein a protrusion is provided on the bonding surface of the electrode by adhering an insulating material to the bonding surface of the electrode. Electronic component manufacturing method. 14. After the solder is attached to the surface of the electrode of the substrate, the protrusion of the electronic component having a partial protrusion on the bonding surface of the electrode is brought into contact with the electrode of the substrate to form the electrode of the electronic component and the substrate. A soldering method for an electronic component, comprising facing an electrode, melting the solder, and then curing the solder. 15. After solder is attached to the electrode surface of a substrate having protrusions on the electrodes, the electrodes of the electronic component are brought into contact with the protrusions of the substrate so that the electrodes of the electronic component and the electrodes of the substrate face each other. A method for soldering an electronic component, characterized in that the solder is melted and then cured.