JP2924856B2 - Semiconductor device mounting method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for mounting a semiconductor device, and more particularly to an improvement in applying a solder cream for connecting a lead of the semiconductor device to a terminal provided on a printed circuit board or the like.

[0002]

2. Description of the Related Art Conventionally, when a semiconductor device is mounted on a printed circuit board or the like, the lead of the semiconductor device is inserted into a through hole provided in a terminal of the printed circuit board or the like and soldered. , From requests for thinning, etc.
2. Description of the Related Art A surface mounting method in which a semiconductor device is mounted on a surface of a printed circuit board or the like and leads are directly connected to terminals is increasing.

[0003] In particular, recently, the field of manufacturing according to the specifications of the customer is expanding, and with the increase in the number of I / O terminals due to the high functionality, semiconductor devices tend to have more and more leads. For example, in a semiconductor device having an outer shape of 28 mm × 28 mm and a thickness of 3.6 mm, a device having 160 leads, a width of each lead being about 300 μm, and an interval of about 650 μm is practically used. Must be matched to the terminal of the printed circuit board or the like to which is connected.

FIG. 6 is an enlarged view of an example of such a mounting structure, in which (a) is a front view, (b) is a side view,
(C) is a plan view. In the figure, reference numeral 1 denotes a printed board or the like, 2 denotes a terminal such as a conductive pattern formed on the surface of the printed board or the like, 11 denotes a semiconductor device mounted on the printed board or the like 1, and 12 denotes its lead. Reference numeral 3 denotes a so-called solder cream formed by bonding fine powder of solder and flux. For example, as shown in FIG. 7, a mask 7 having a window 8 matching the size and shape of the terminal 2 is used. It is printed with a squeegee (hereinafter referred to as coating).

After the solder cream 3 is applied to each terminal 2 in this manner, the semiconductor device 11 is placed on a printed circuit board 1 or the like, and the leads 12 abut on the terminals 2 respectively. For example, the leads 12 and the terminals 2 are respectively connected, and the semiconductor device 11 is mounted on a printed board 1 or the like.

[0006]

In the mounting structure of the semiconductor device as described above, the size and shape of the window 8 of the mask 7 are exactly the same as the size and shape of the terminal 2.
On the other hand, since the width and the interval of the terminals 2 are becoming increasingly narrower, when applying the solder cream using the mask 7,
As shown in FIG. 8, a so-called solder bridge 4 in which the solder cream 3 bridges adjacent terminals 2 is likely to occur.
When the solder bridge 4 occurs, since it is manually removed, the appearance inspection and the repair of the solder cream 3 take much time and labor, and the repair of the solder cream 3 causes secondary defects. May occur.

When the lead 12 is connected to the terminal 2 by a reflow device, as shown in FIG. 9, the solder does not have a skirt at the outer end portion 5 and the solder is hardly seen from the outside (inside). 6, it was difficult to judge the quality of soldering by visual inspection.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and the solder cream is not drawn into the lead at the time of reflow. Another object of the present invention is to obtain a surface mounting structure of a semiconductor device which also facilitates the above.

[0009]

According to a method of mounting a semiconductor device of the present invention, a solder cream is applied to a surface of a plurality of terminals provided on a substrate, and then the reflow is performed to re-flow the plurality of terminals and the semiconductor device. In the semiconductor device mounting method for connecting a plurality of leads, the solder cream is applied to each of the plurality of terminals such that a side closer to a tip of the lead is larger than a side closer to the semiconductor package. It is characterized by applying cream.

[0010]

[0011]

[0012]

[0013]

By applying the solder cream so that the side closer to the tip of the lead is larger than the side closer to the semiconductor package, the solder is prevented from being drawn into the lead after reflow. As a result, the solder is concentrated on the tip of the lead and the skirt is widened, so that the state of soldering from the outside can be easily observed. This makes it easier to inspect the appearance of soldering and makes it easier to remove solder bridges

[0014]

[0015]

FIG. 1 is a plan view of an embodiment of the present invention. In this embodiment, the application length l of the solder cream 3
₁ is l ≠ l with respect to the length l of the terminal 2 and its width W ₁
Is set to W ₁ <W with respect to the width W of the terminal. 0.6~0.9W the width _{W 1} of the solder cream 3 in the embodiment
And

[0016] FIG. 5 is obtained by testing the adhesion strength graph showing the relationship between adhesion strength, giving a tensile force to the lead 12 connected to the terminal 2 of the width W ₁ and the lead 12 of the solder cream 3 . As is clear from the figure, W ₁ / W is 1
Up to 0.7 has an adhesion strength of 6 kg / mm ² or more.
6 is about 4 kg / mm ² , but 0.5 is 2 kg / mm 2
It suddenly drops to ² . Therefore, it was found that if W ₁ / W was in the range of approximately 0.6 to 0.9, the device could be put to practical use without losing reliability.

When the solder creams 3 were printed using a mask having a window of W ₁ / W of 0.5 to 1.0, the occurrence of the solder bridges 4 was almost as shown in Table 1.

[0018]

[Table 1]

FIG. 2 shows another embodiment of the present invention.
(A) In the embodiment of the figure, the width W of the solder cream 3 is shown.₁Is the end
Same as the width W of the child 2 and W ₁≠ W, but semi-conductive
At the end on the side on which the body device 11 is placed (hereinafter referred to as the inside)
Is not coated with solder cream 3 and is on the other side
) Protrudes from terminal 2 and applies solder cream 2
It is a thing. In other words, the terminal 2 has almost the same length and the same length.
Shift solder cream 3 of the same width outward with respect to terminal 2
And applied.

[0020] In the embodiment, the length l ₂ of the terminal 2 of the portion not coated with the solder cream 3, a length l ₃ of the solder cream third portion which extends from the terminal 2, the terminal 2 with respect to the length l Each was set to 0.1 to 0.41. In this case, it is not necessary to set l ₂ = l ₃ and can be changed as appropriate.

(B) In the embodiment shown in the figure, the solder cream 3 having substantially the same width as the terminal 2 is divided into three in the longitudinal direction (3a, 3a).
3b, 3c) and apply the solder creams 3a, 3b, 3c at appropriate intervals,
Protruding from the terminal 2 and applied. In the above embodiment, the case where the solder cream 3 is divided into three is described, but the solder cream 3 may be divided into two or four or more.

In the embodiment shown in FIG. 2C, the solder cream 3 is applied so that the inner side is narrower than the width of the terminal 2 and the outer side is wider and protrudes outward. (C) shows the solder cream 3 of the embodiment shown in FIG.

In the embodiment shown in FIGS. 2A to 2D, a small amount of the solder cream 3 is applied on the inside and a large amount of the solder cream is applied on the outside. Therefore, as shown in FIG. Is hardly drawn inward, and the tip can be fully pulled down.

[0024] variously changed result of the experiment the length l ₂ of the portion not coated with the inside of the solder cream 3 are shown in Table 2.

[0025]

[Table 2]

FIG. 3 is a plan view of still another embodiment of the present invention. FIG. 3 (a) shows an embodiment combining the embodiments of FIGS. 1 and 2 (a), and FIG. 3 (b) shows an embodiment of FIG. 1 is a combination of the embodiments of FIGS. 1 and 2 (b). According to these embodiments, not only the occurrence of solder bridges when the solder cream 3 is applied but also the inside of the solder cream during reflow can be prevented. Can be prevented from being pulled in.

As is apparent from the above description, the embodiment of Figure 1 by setting the relationship between the width W ₁ of creams 3 and solder width W of the terminal 2 to W> W ₁ ≧ 0.6 W, solder Since the generation of the solder bridge 4 when the cream 3 is applied can be prevented, the method is implemented when the semiconductor device 11 is mounted on a printed circuit board 1 having a narrow terminal interval.
Especially effective.

The embodiment of FIG.
Is almost the same as the width of the terminal 2. However, since the amount of the solder cream 3 applied is small on the inside and large on the outside, the solder cream 3 is not drawn into the inside at the time of reflow. The hem can be pulled sufficiently.
Therefore, the embodiment is particularly effective when the terminal interval is relatively wide.

Furthermore, the embodiment of Figure 3, the relationship between the width _{W 1} of creams 3 and solder width W of the terminal 2 W> _{W 1} ≧
At the same time, the solder cream 3 was applied to the inside at a small amount and the outside was increased, so that the solder cream 3 was applied not only to prevent the occurrence of solder bridges but also to prevent the solder cream 3 from being applied at the time of reflow. Can be prevented from being pulled into the outer end, and the hem can be pulled sufficiently at the outer end. Therefore, the present embodiment is extremely effective when implemented when a semiconductor device is mounted on a printed circuit board or the like having terminals of various sizes and shapes.

[0030]

As is clear from the above description, according to the present invention, since the amount of solder cream applied is small on the inside and large on the outside, the solder cream does not draw in during reflow, and the appearance of the soldered state does not occur. Make inspection easier,
A surface mounting structure of a semiconductor device that also facilitates removal of a solder bridge can be obtained.

Therefore, it is not necessary to take much time for removing the solder bridge, and the inspection of the adhesion state of the solder cream can be easily performed.

[Brief description of the drawings]

1A to 1D are plan views of an embodiment of the present invention.

FIGS. 2A to 2D are plan views of an embodiment of the present invention.

FIGS. 3A and 3B are plan views of an embodiment of the present invention.

FIG. 4 is an explanatory diagram of the operation.

FIG. 5 is a diagram showing the relationship between the width of the solder cream and the width of the terminal according to the present invention and the relationship between the width and the adhesion strength.

FIG. 6 is a view for explaining a surface mounting structure, and FIG.
Is a front view, (b) is a side view, and (C) is a plan view.

FIG. 7 is a perspective view showing a relationship between a terminal and a mask.

FIG. 8 is a plan view showing a state in which a solder bridge is generated.

FIG. 9 is a side view showing a state after the conventional reflow.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Printed circuit board etc. 2 ... Terminal 3 ... Solder cream 4 ... Solder bridge 6 ... Retraction 7 ... Mask 8 ... Window 11 ... Semiconductor device 12 ... Lead

Claims (2)

(57) [Claims] 1. A method of mounting a semiconductor device, comprising: applying solder cream to a surface of a plurality of terminals provided on a substrate; and reflowing the solder cream to connect the plurality of terminals to a plurality of leads of the semiconductor device. A method of mounting a semiconductor device, comprising: applying the solder cream to each of the plurality of terminals such that an amount of application of the solder cream is larger on a side closer to a tip of the lead than on a side closer to a package of the semiconductor. . 2. A method of mounting a semiconductor device, comprising applying solder cream to surfaces of a plurality of terminals provided on a substrate and then reflowing the plurality of terminals and a plurality of leads of the semiconductor device. Each of the plurality of terminals, the width of the solder cream applied to the side near the tip of the lead, the width of the solder cream is wider than the width of the solder cream applied to the side near the semiconductor package, A method for mounting a semiconductor device, comprising applying a cream.