JP6066476B2 - Solder paste application structure - Google Patents

Description

  The present invention relates to a solder paste coating structure.

  Conventionally, when a surface mounting electronic component (for example, a ceramic capacitor or the like) having a pair of electrodes is mounted on a substrate as in Patent Document 1, for example, first, a pair of lands formed on the mounting surface of the substrate is used. After solder paste is applied to the entire (solder land) by printing or the like, the electronic component is arranged on the substrate so that each electrode of the electronic component is in contact with the solder paste on each land. Then, an electronic component is soldered (joined) to a board | substrate by implementing a reflow process.

  Patent Document 1 discloses a configuration in which a recessed portion is formed in the planar contour of each land, and a pair of lands are arranged so that the recessed portions are positioned in opposite directions. We are trying to improve. The self-alignment effect means that the surface tension of the molten solder is obtained by melting the solder paste in the reflow process even if the electronic components are slightly displaced from the pair of lands in a state where the electronic components are arranged on the substrate. As a result, the position of the electronic component is corrected by being pulled.

JP 2003-234567 A

  However, in the above conventional configuration, for example, as shown in FIGS. 8 and 9, when the electronic component 2 is soldered to the substrate 4 in the reflow process, the molten solder is scattered between the pair of lands 105 and 105. The molten solder thus left remains on the substrate 4 as “solder balls 100” between the pair of lands 105, 105. In particular, when the pair of lands 105, 105 and the solder paste 101 applied thereto are formed in a rectangular shape in plan view as shown in the illustrated example, and the sides of the pair of solder pastes 101, 101 are opposed to each other, Since the amount of molten solder scattered between the pair of lands 105, 105 increases, the solder balls 100 may be coupled between the pair of lands 105, 105, and the pair of lands 105, 105 may be electrically connected by the solder. There is.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a solder paste application structure capable of suppressing the generation of solder balls without impairing the self-alignment effect in the reflow process.

In order to solve this problem, the solder paste application structure of the present invention is a solder paste application structure in which a solder paste is applied to a pair of lands formed at intervals on a mounting surface of a substrate. The planar outline of the solder paste has a recess that is recessed inwardly from the periphery of the solder paste, the recesses of a pair of solder pastes face each other, and the application surface of the land to which the solder paste is applied is in the recess. surrounded by the solder paste have a draining flowing upon melting, the said inflow region of the pair of the land, recess recessed in a direction away from each other from the portions facing each other of the peripheral edge of the pair of the land And a protrusion protruding in a direction approaching each other from the bottom of the recess .

  In the solder paste application structure, an inflow groove that is recessed from the land application surface in the thickness direction of the land and extends in the arrangement direction of the pair of lands is formed in the inflow region of the land. And preferred.

Further, in the coating structure of the solder paste, it may be located at a bottom portion and a spacing of the recess portion of the bottom portion and the land of the recess of the solder paste.

  Further, in the solder paste application structure, the planar contour of the pair of solder pastes has a straight portion extending in a direction orthogonal to the arrangement direction of the pair of lands along the mounting surface from both side portions of the recess. Good.

  In the solder paste application structure, the corners of the planar contour of each solder paste may be rounded.

  According to the present invention, it is possible to suppress the generation of solder balls without impairing the self-alignment effect in the reflow process.

It is a schematic plan view which shows the application structure of the solder paste which concerns on 1st embodiment of this invention. It is BB arrow sectional drawing of FIG. It is CC sectional view taken on the line of FIG. It is a schematic plan view explaining the self-alignment effect obtained in the application structure of the solder paste shown in FIGS. It is a schematic sectional drawing which shows the state which soldered the electronic component to the board | substrate using the application structure of the solder paste shown in FIGS. The application structure of the solder paste which concerns on 2nd embodiment of this invention is shown, (a) is a schematic plan view, (b) is a perspective view of the land shown to (a). It is a schematic plan view which shows the application structure of the solder paste which concerns on 3rd embodiment of this invention. It is a schematic plan view which shows an example of the conventional solder paste structure. It is DD sectional view taken on the line of FIG.

[First embodiment]
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
As shown in FIGS. 1 to 3, the application structure of the solder paste 1 according to this embodiment is for mounting an electronic component 2 for surface mounting (for example, a ceramic capacitor) having electrodes 3 </ b> A and 3 </ b> B on both ends to a substrate 4. The structure is such that a solder paste 1 (1A, 1B) is applied to a pair of lands 5A, 5B formed on the mounting surface 4a of the substrate 4 at intervals.
In the present embodiment, each land 5A, 5B is formed in a rectangular shape in plan view. Further, one side of the pair of lands 5A and 5B in plan view opposes to be parallel to each other.

Solder paste 1A, 1B is applied to the application surface 6 of each land 5A, 5B. And the planar outline of each solder paste 1A, 1B has the recessed part 7 recessed inside from the periphery of solder paste 1A, 1B. The recesses 7 of the pair of solder pastes 1A and 1B face each other.
In the present embodiment, the solder pastes 1A and 1B are formed in a rectangular shape in plan view, and the concave portion 7 described above is formed in a central portion of one side of the solder pastes 1A and 1B in plan view. In other words, in this embodiment, the planar contours of the solder pastes 1A and 1B are arranged in the arrangement direction (X-axis direction) of the pair of lands 5A and 5B along the mounting surface 4a of the substrate 4 from both sides of the recess 7. It has a linear portion 8 extending in a direction orthogonal to each other (the width direction of each land 5A, 5B and the Y-axis direction).

Moreover, in this embodiment, the corner | angular part of the planar outline of solder paste 1A, 1B is rounded. In the illustrated example, the four corners of the solder pastes 1A and 1B that are rectangular in plan view, the corners of the recess 7 and the straight portion 8, and the corners in the recess 7 are rounded. .
Furthermore, in this embodiment, each side of the solder pastes 1A and 1B formed in a rectangular shape in plan view is parallel to each side of the lands 5A and 5B.
As described above, in a state where the solder pastes 1A and 1B are applied to the application surfaces 6 of the lands 5A and 5B, the application surfaces 6 of the lands 5A and 5B are surrounded by the recesses 7 of the solder pastes 1A and 1B. It has an inflow region 6a that flows when the pastes 1A and 1B are melted.

When the electronic component 2 is mounted on the substrate 4 by using the solder paste 1 coating structure configured as described above, a pair of electrodes of the electronic component 2 is used as shown in FIGS. After the electronic component 2 is arranged on the substrate 4 so that 3A and 3B are in contact with the pair of solder pastes 1A and 1B, a reflow process for melting the solder pastes 1A and 1B may be performed.
In the reflow process, each molten solder paste 1A, 1B (molten solder) flows into the inflow region 6a of the application surface 6 of each land 5A, 5B. Further, in the reflow process, the molten solder wets and spreads on the lower surfaces 9a and side surfaces 9b of the electrodes 3A and 3B. Therefore, when cooled after the reflow process, for example, as shown in FIG. 5, the lower surfaces 9a and side surfaces of the electrodes 3A and 3B 9b is joined to each land 5A, 5B via each solder fillet 10A, 10B.

Hereinafter, the operation of the mounting method described above will be described more specifically.
In a state where the electronic component 2 is arranged on the substrate 4, for example, as shown in FIGS. 1 to 3, the electronic component 2 is in a correct position with respect to the pair of solder pastes 1A and 1B (position where the electronic component 2 is to be mounted). Are disposed on the recess 7 (inflow region 6a) of each solder paste 1A, 1B. Thereafter, when the reflow process is performed, the molten solder flows into the inflow regions 6a of the lands 5A and 5B, and therefore, the solder fillets 10A and 10B are interposed between the lower surfaces 9a of the electrodes 3A and 3B of the electronic component 2 and the lands 5A and 5B. 10B can be formed satisfactorily (see FIG. 5).

  Further, as shown in FIG. 5, as the solder fillets 10A and 10B are well formed between the electrodes 3A and 3B and the lands 5A and 5B of the electronic component 2, the electrodes 3A and 3B and the lands The surfaces of the solder fillets 10A and 10B exposed to the outside between 5A and 5B exhibit shapes (back fillets 11A and 11B) that are curved inwardly of the solder fillets 10A and 10B due to surface tension. By forming the back fillets 11A and 11B, the bonding strength between the electrodes 3A and 3B and the lands 5A and 5B by the solder fillets 10A and 10B is improved.

  Further, in the coating structure of the present embodiment, in a state where the electronic component 2 is arranged on the substrate 4, for example, as shown in FIG. 4, the electronic component 2 has a pair of lands 5A and a pair of lands 5A and 1B. Even when the 5B array direction (X-axis direction) and the lands 5A and 5B are displaced in the width direction (Y-axis direction), the pair of electrodes 3A and 3B can be brought into contact with the pair of lands 5A and 5B. Therefore, in the reflow process, the molten solder flows into the inflow regions 6a of the lands 5A and 5B (for example, flows in the directions indicated by the arrows A1 and A2), so that a self-alignment effect can be obtained and the electronic component 2 is placed in the correct position ( (See FIG. 1).

In particular, in the coating structure of the present embodiment, the molten solder flows into the inflow region 6a of each land 5A, 5B in the reflow process, whereby a strong flow toward the inner side in the width direction (Y-axis direction) of each land 5A, 5B (see FIG. 4), the self-alignment effect in the width direction (Y-axis direction) of each land 5A, 5B can be improved.
Even if the electronic component 2 is shifted as described above, the solder fillets 10A and 10B are satisfactorily formed between the electrodes 3A and 3B and the lands 5A and 5B of the electronic component 2 as described above. (See FIG. 5).

And in the application structure of the solder paste 1 of this embodiment, since each solder paste 1A, 1B has the recessed part 7, since the quantity of the part which mutually opposes among a pair of solder paste 1A, 1B decreases, it reflows. The amount of molten solder scattered between the pair of lands 5A and 5B in the process can be suppressed. That is, the generation of solder balls (see FIGS. 8 and 9) between the pair of lands 5A and 5B can be suppressed, and the pair of lands 5A and 5B can be prevented from being electrically connected by solder.
From the above, according to the application structure of the solder paste 1 of this embodiment, the generation of solder balls can be suppressed without impairing the self-alignment effect in the reflow process.

  In addition, according to the coating structure of the present embodiment, the planar contour of each solder paste 1A, 1B has the straight portion 8 extending from both sides of the recess 7 in the width direction (Y-axis direction) of each land 5A, 5B. Even when the amount of displacement of the pair of electrodes 3A, 3B in the Y-axis direction with respect to the pair of solder pastes 1A, 1B is large with the electronic component 2 disposed on the substrate 4, the electrodes 3A, 3B are securely attached to the solder. It can be made to contact paste 1A, 1B. That is, the self-alignment effect can be more reliably obtained as compared with the case where there is no straight portion 8 (for example, when the concave portion 7 is formed in a solder paste having a circular shape in plan view).

Further, in the coating structure of the present embodiment, the solder paste 1 having rounded corners is formed on the lands 5A and 5B. Therefore, the solder paste 1 can be obtained with high accuracy even by screen printing. It can be formed on the lands 5A and 5B.
More specifically, when the solder paste 1 is formed on each land 5A, 5B by screen printing, a mask (not shown) having an opening corresponding to the planar view shape of the solder paste 1 is formed on the substrate 4. The solder paste 1 is applied so as to fill the opening of the mask, and finally the mask is peeled off from the substrate 4.
Here, when the corner of the solder paste 1 (the corner of the mask opening) is sharp, when the mask is peeled off from the substrate 4, a part of the solder paste 1 remains at the corner of the mask opening. Therefore, the shape of the solder paste 1 on each land 5A, 5B is impaired. On the other hand, in this embodiment, since the corner of the solder paste 1 (corner of the mask opening) is rounded, the solder paste 1 is applied to the corner of the mask opening when the mask is peeled off from the substrate 4. Since it can prevent remaining, the shape of the solder paste 1 can be maintained with high accuracy.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIG.
In this embodiment, compared with the coating structure of the first embodiment, only the shape of the land is different, and the other configurations are the same as those of the first embodiment. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

As shown in FIG. 6, in the coating structure of this embodiment, as in the first embodiment, each land 15A, 15B is formed in a rectangular shape in plan view, and one side of the pair of lands 15A, 15B is parallel to each other. Opposite to. Also, the solder pastes 1A and 1B having the recesses 7 are formed on the lands 15A and 15B, whereby the application surface 16 of the lands 15A and 15B is surrounded by the recesses 7 of the solder pastes 1A and 1B. Thus, the solder paste 1A, 1B has an inflow region 16a that flows when melted.
In this embodiment, the inflow regions of the lands 15A and 15B are recessed from the coating surface 16 of the lands 15A and 15B in the thickness direction (Z-axis negative direction) of the lands 15A and 15B and the pair of lands 15A and 15B. An inflow groove 17 extending in the arrangement direction (X-axis direction) is formed.

In the example shown in the drawing, the end of the inflow groove 17 in the extending direction (X-axis direction) is open in a portion (one side) of the lands 15A and 15B facing each other. It does not have to be.
Moreover, the planar view shape of the inflow groove | channel 17 is not restricted to the example of illustration, For example, the planar outline of the inflow groove | channel 17 may be made into the shape which follows the recessed part 7 of solder paste 1A, 1B. In other words, the inflow groove 17 may be formed in the entire inflow region 16a of each land 15A, 15B, for example.

When the electronic component 2 is mounted on the substrate 4 using the coating structure of the present embodiment configured as described above, the electronic component 2 is arranged on the substrate 4 as in the first embodiment. Then, a reflow process for melting the solder pastes 1A and 1B may be performed.
In the reflow process, the molten solder flows into the inflow regions of the lands 15A and 15B and further flows into the inflow grooves 17, so that the flow toward the inner side in the width direction (Y-axis direction) of the lands 15A and 15B is further promoted. Is done. The molten solder that has flowed into the inflow groove 17 flows toward the opening side of the recess 7 (inside the pair of lands 15A and 15B) in the extending direction of the inflow groove 17 (X-axis direction).

  Therefore, according to the coating structure of the present embodiment, not only the same effects as in the first embodiment can be obtained, but also the self-alignment effect can be further improved. Also, the solder fillets 10A and 10B (see FIG. 5) between the electrodes 3A and 3B of the electronic component 2 and the lands 15A and 15B can be formed more satisfactorily.

[Third embodiment]
Next, a third embodiment of the present invention will be described with reference to FIG.
In this embodiment, as compared with the coating structure of the first and second embodiments, only the shape of the land is different, and the other configurations are the same as those of the first embodiment. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

As shown in FIG. 7, in the coating structure of the present embodiment, solder pastes 1A and 1B similar to those of the first embodiment are formed on the coating surface 26 of the lands 25A and 25B. 25B has an inflow region 26a that flows when the solder paste 1A, 1B is melted by being surrounded by the recess 7 of the solder paste 1A, 1B.
In the present embodiment, in the inflow regions 26a of the pair of lands 25A and 25B, the recessed portions 27 that are recessed in the direction away from each other along the mounting surface 4a are formed in the facing portions 26a. Protrusions 28 that protrude from the bottom toward each other are formed.

  Furthermore, in the present embodiment, the pair of lands 25A and 25B are formed in a rectangular shape in plan view, and the recessed portion 27 is recessed from the central portion of one side facing each other so as to be parallel to each other in the pair of lands 25A and 25B. Is formed. That is, the shape of the planar contour of the lands 25A and 25B of the present embodiment excluding the protruding portion 28 is a similar shape that is slightly larger than the planar contour of the solder pastes 1A and 1B having the recesses 7. However, the recess 27 is preferably formed such that the bottom of the recess 7 and the bottom of the recess 27 are positioned at an interval as shown in FIG.

Further, the tip of the protruding portion 28 in the protruding direction may be positioned so as to protrude outward from the opening of the recessed portion 27, for example, but is positioned so as to coincide with the opening of the recessed portion 27 as shown in FIG. Or located inside the opening of the recess 27.
In addition, as shown in FIG. 7, the configuration in which the tip in the protruding direction of the protruding portion 28 is positioned so as to coincide with the opening of the recessed portion 27 forms two recessed portions 29 recessed inward from the peripheral edges of the lands 25A and 25B. It is equal to the configuration. In this case, the portions of the lands 25A and 25B located between the two recesses 29 and 29 correspond to the protrusions 28 described above.

When the electronic component 2 is mounted on the substrate 4 using the coating structure of the present embodiment configured as described above, the electronic component 2 is arranged on the substrate 4 as in the first embodiment. Then, a reflow process for melting the solder pastes 1A and 1B may be performed. In the reflow process, the molten solder flows into the inflow regions 26a of the lands 25A and 25B, and further flows in the protruding direction of the protrusions 28 (inside the pair of lands 25A and 25B).
Therefore, according to the coating structure of the present embodiment, not only the same effects as in the first embodiment can be obtained, but also the self-alignment effect of the electronic component 2 can be further improved. Also, the solder fillets 10A and 10B (see FIG. 5) between the electrodes 3A and 3B of the electronic component 2 and the lands 25A and 25B can be formed more satisfactorily.

  Further, in the coating structure of the present embodiment, the bottom of the recess 7 of each solder paste 1A, 1B and the bottom of the recess 27 of each land 25A, 25B are positioned at an interval so that molten solder can be used in the reflow process. A sufficient size of the inflow region 26a can be secured. For this reason, it is possible to obtain a sufficient flow of the molten solder toward the inside in the width direction (Y-axis direction) of each land 15A, 15B. Therefore, even if the depressions 27 and the protrusions 28 are formed in the lands 15A and 15B, the self-alignment effect in the width direction (Y-axis direction) of the lands 15A and 15B can be improved.

  The configuration of the third embodiment described above can also be applied to the configuration of the second embodiment described above. For example, the inflow groove 17 of the second embodiment shown in FIG. 6 may be formed in the protrusion 28 shown in FIG.

Although the details of the present invention have been described above by the embodiments, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.
For example, the planar view shape of each solder paste 1A, 1B is not limited to that of the above embodiment, and may be formed in an arbitrary planar view shape such as a circle or a triangle as long as it has at least the concave portion 7. In particular, the opposite parts (outer parts of the pair of solder pastes 1A and 1B) of the planar outlines of the solder pastes 1A and 1B are formed by the electronic component 2 in a pair of lands 5A and 5B (15A, 15B, 25A, As long as the amount of the solder pastes 1A and 1B is adjusted so that the phenomenon of rising (Manhattan phenomenon, tombstone phenomenon) does not occur on one side of 25B), the shape may be arbitrary.

  However, when the improvement of the self-alignment effect is particularly taken into consideration, it is preferable that the planar outlines of the solder pastes 1A and 1B have linear portions 8 extending in the Y-axis direction from both side portions of the recess 7 as in the above embodiment. .

Further, the shape of each land 5A, 5B (15A, 15B, 25A, 25B) in plan view is not limited to that of the above embodiment, as in the case of the solder pastes 1A, 1B, and may be any arbitrary shape such as a circle or a triangle. It may be formed in a plan view shape.
Further, the lands 5A, 5B (15A, 15B, 25A, 25B) and the solder pastes 1A, 1B are not limited to being formed in a plan view shape similar to each other as in the above-described embodiment. May be formed.

1, 1A, 1B Solder paste 2 Electronic component 3A, 3B Electrode 4 Substrate 4a Mounting surface 5A, 5B, 15A, 15B, 25A, 25B Land 6, 16, 26 Application surface 6a, 16a, 26a Inflow region 7 Recess 17 Inflow groove 27 Indentation 28 Projection

Claims (5)

A solder paste application structure in which a solder paste is applied to each of a pair of lands formed at intervals on a mounting surface of a substrate,
The planar contour of each solder paste has a recess recessed inward from the periphery of the solder paste, and the recesses of the pair of solder pastes face each other,
The coated surface of the land solder paste is applied is, the solder paste is surrounded by the recess have a draining flowing upon melting,
The inflow regions of the pair of lands are formed with recesses that are recessed in the direction away from each other of the peripheral edges of the pair of lands, and project in a direction approaching each other from the bottom of the recesses. A structure for applying a solder paste, characterized in that a protrusion is formed .   2. The inflow region of the land is formed with an inflow groove that is recessed in the thickness direction of the land from the application surface of the land and extends in the arrangement direction of the pair of lands. Solder paste application structure. Coating the structure of the solder paste according to claim 1 or claim 2, characterized in that the bottom portion of the recess portion of the land and the bottom of the recess of the solder paste is located at an interval.   The planar outline of the pair of solder pastes has straight portions extending in a direction orthogonal to the arrangement direction of the pair of lands along the mounting surface from both side portions of the recess. Item 4. The solder paste application structure according to any one of Items 3 to 4.   5. The solder paste application structure according to claim 1, wherein corners of the planar outline of each solder paste are rounded. 6.

Images