JPH04360561A - Semiconductor package and its formation - Google Patents

Abstract

PURPOSE:To prevent the misalignment of a resin package and height fluctuation of leads when the package is mounted on a printed circuit board by making the bottom of the package manufactured in a resin sealing process flat. CONSTITUTION:The bottom of a resin package 5 manufactured in a resin sealing process is made flat by removing the bottom 8a of the package 5 by grinding. As a result, the misalignment of the semiconductor package caused by defective temporary fixing and defective soldering caused by the height fluctuation among leads 3 can be prevented in a process for mounting the package on a printed wiring board 7. In addition, semispheric projections 11 which support the package 5 together with each lead 3 are provided on the bottom of the package 5. Therefore, when the projections 11 come into contact with the board 7 at the time of mounting the package 5 on the board 7, a fixed clearance is formed between the bottom of the package 5 and substrate 7 and the height of the package is fixed to a prescribed value after mounting.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor package in which a semiconductor element is sealed with resin, and a method for forming the semiconductor package.

0002

[Prior Art] Semiconductor packages include insertion type semiconductors that are mounted on a printed wiring board by inserting leads into sockets on the printed wiring board or by inserting leads into through holes on the printed wiring board. 2. Description of the Related Art There are two types of semiconductor packages: semiconductor packages, and surface-mount semiconductor packages that are directly mounted on the surface of a printed wiring board by soldering.

Surface-mount semiconductor packages were developed to realize high-density mounting on printed wiring boards, and for example, the Mitsubishi Semiconductor Data Book IC Package Edition (Mitsubishi Electric Corporation, February 1989 issue) )P. 1
Classified as shown in -5. Among these, resin-sealed semiconductor packages have two
There are two types: a two-sided type with one lead extraction surface and a four-sided type with four lead extraction surfaces in one resin package, but both have a cross-sectional structure as shown in Figure 17. There is.

In FIG. 17, 1 is a semiconductor element, 2 is a gold wire for connecting the semiconductor element 1 and a lead 3, 3 is a lead for connecting the printed wiring board 7 and the semiconductor element 1, and 4 is a gold wire for connecting the semiconductor element 1 and the lead 3.
5 is a die pad that supports the semiconductor element 1, and 5 is a resin package that seals the semiconductor element 1. d indicates the distance between the resin package 5 and the printed wiring board 7.

Such a semiconductor package is described, for example, in Electronic Materials (December 1989 issue), P. The semiconductor element 1 is manufactured by sealing the semiconductor element 1 with a sealing resin using a molding apparatus as shown in 41. Resin sealing is, for example, 1
It is carried out at a high temperature of 75°C. Therefore, semiconductor element 1
and the difference in linear expansion coefficient between the encapsulating resin and the vertical asymmetry in the cross-sectional structure of the semiconductor package (see Figure 17).
As a result, upon cooling to room temperature, a downward warp as shown in FIG. 18(a) or an upward warp as shown in FIG. 18(b) occurs.

By the way, the semiconductor package shown in FIG. 17 has a structure in which the position of the lead 3 in contact with the printed wiring board 7 is lower than the bottom surface of the resin package 5, and a distance d is provided between the lead 3 and the printed wiring board 7. It becomes. Further, the structure is such that the leads 3 support the resin package 5. Therefore, when the semiconductor package is mounted on the printed wiring board 7, the bottom surface thereof does not come into contact with the printed wiring board 7. Therefore, in a semiconductor package having such a structure, even if some warpage occurs, it does not cause much problem during mounting.

Further, the semiconductor package is usually fixed to the printed wiring board 7 by soldering. Surface-mount semiconductor packages are often soldered by reflow soldering. In reflow soldering, an appropriate amount of solder is supplied to the joint in advance, and
This is a method of soldering by melting and solidifying the solder using an external heat source.

When soldering the semiconductor package to the printed wiring board 7 by reflow soldering,
After placing the semiconductor package at a predetermined position on the printed wiring board 7, it is necessary to temporarily fix the semiconductor package to prevent it from shifting until it is completely fixed to the printed wiring board 7 by soldering. be. Temporary fixing can be done using, for example, the latest surface mount technology (published by Kogyo Chosenkai Co., Ltd., June 1986) P. 24
7-P. 250, using adhesives or by utilizing the tackiness of solder paste.

In the semiconductor package having the structure shown in FIG. 17, after the semiconductor package is placed in a predetermined position on the printed wiring board 7, it is fixed with an ultraviolet curing adhesive or the like while applying a load. It is possible to set the height of the mounted semiconductor package to a predetermined value. That is, since the distance between the bottom surface of the resin package 5 and the printed wiring board 7 is determined by the distance d, the coating thickness of the adhesive is naturally determined even if there is some variation in the amount of adhesive. Therefore, the height of the semiconductor package is maintained at a predetermined value. Further, even when a temporary fixing method using the adhesiveness of solder paste is adopted, there is no particular problem in mounting.

However, recently, the above literature (electronic materials 1
As mentioned in the December 989 issue), the thin package,
For example, TSOP (Thin Small Outline)
e Package) and TCP (Tape Carri
er Package) are adopted, and their thickness is 1
mm or less. In such a semiconductor package, the resin package 5 and the printed wiring board 7
There is no room to provide a distance d between the two. Moreover, T.C.
When the thickness of the leads 3 is about several tens of micrometers as in P, the rigidity of the leads 3 is low, making it difficult for the leads 3 to support the weight of the semiconductor package. As a result, the structure of the semiconductor package is such that the bottom surface of the resin package 5 directly contacts the printed wiring board 7 during mounting.

In such a thin semiconductor package, if it is warped as shown in FIG. 18, temporary fixing cannot be performed properly. Furthermore, the semiconductor package may be misaligned until the soldering is completed. Furthermore, even if the semiconductor package is not warped at the time of temporary fixing, the semiconductor package may be deformed due to the temperature rise associated with soldering. In that case, warping will still occur during soldering, and the leads 3 will be soldered with uneven heights.

[0012] Furthermore, in recent thin semiconductor packages, the number of leads 3 has increased to several hundred, and there is a remarkable tendency to increase the number of pins. Furthermore, the lead spacing has become narrower to several hundred micrometers. Accordingly, the width of the solder pads formed on the printed wiring board 7 and the spacing between the pads are also becoming narrower. As a result, the problem of solder bridging makes it difficult to supply solder paste by screen printing. Also, the amount of solder that can be supplied to each solder pad is
It's getting less.

Furthermore, since the dimensions of the semiconductor element 1 are increasing year by year, the weight of the semiconductor package is also increasing. For the above reasons, temporary fixing using the adhesiveness of solder paste is becoming increasingly difficult.

Furthermore, when mounting a semiconductor package with a large number of pins, accurate positioning with respect to the printed wiring board 7 is required. Furthermore, it is also required that positional deviations do not occur due to mechanical vibrations or impacts after positioning. In order to meet these demands, a temporary fixing method for semiconductor packages using a temporary fixing adhesive has recently become mainstream.

When temporarily fixing a thin semiconductor package to the printed wiring board 7, the amount of adhesive applied needs to be set according to the size and shape of the semiconductor package, but if the amount is less than the appropriate amount, the package will not be fixed. does not fulfill its role. On the other hand, if there is too much adhesive, the adhesive will flow out to the parts to be soldered, causing problems with soldering and making it impossible to obtain a good electrical connection.

Furthermore, since it is not possible to use the distance d for temporary fixing, the thickness of the adhesive is adjusted by the load applied to the semiconductor package. If the load is too large, a large amount of adhesive will protrude from the bottom of the package, resulting in a thinner adhesive. Conversely, if the load is too small, the adhesive will become thicker.

Therefore, in order to maintain the height of the semiconductor package mounted on the printed wiring board 7 at a predetermined value, it is necessary to finely control the thickness of the adhesive.

[0018]

[Problems to be Solved by the Invention] Since the conventional semiconductor package is constructed as described above and is mounted on the printed wiring board 7 as described above, especially in the case of a thin package, There was a problem in that temporary fixing and soldering could not be performed well due to the warpage. This warping of the semiconductor package must be eliminated as it causes various other problems, but as the dimensions of the semiconductor element 1 tend to increase year by year, these problems will become more and more prominent in the future. It is expected that

Furthermore, in the case of a thin semiconductor package, since the resin package 5 comes into direct contact with the printed wiring board 7, it is difficult to control the amount and thickness of the adhesive used when temporarily bonding. Therefore, there was a problem that the heights of the semiconductor packages mounted on the printed wiring board 7 were not the same. Particularly, in products such as IC cards that have strict thickness restrictions, there has been a problem in that it is extremely difficult to accurately mount a semiconductor package within a limited space.

The present invention has been made to solve the above-mentioned problems, and provides a semiconductor package and such a semiconductor package that can prevent defects in temporary fixing and variations in lead height during mounting. The purpose of this invention is to obtain a method for forming a transparent semiconductor package.

[0021] Also, when temporarily fixing using adhesive,
An object of the present invention is to obtain a semiconductor package in which the thickness of the adhesive can be made constant without controlling the amount of adhesive applied or the load applied to the semiconductor package, and a method for forming a semiconductor package that can provide such a semiconductor package.

[0022]

[Means for Solving the Problems] A method for forming a semiconductor package according to the invention as set forth in claim 1 includes: after completion of resin sealing,
This method includes a step of flattening the bottom surface of the resin package by grinding.

The semiconductor package according to the second aspect of the invention has a flat metal plate or ceramic plate attached to the bottom of the resin package so that one surface is exposed.

The semiconductor package according to the third aspect of the invention has a structure in which a plurality of protrusions are provided on the bottom surface of the resin package.

The semiconductor package according to the fourth aspect of the present invention has a structure in which the bottom surface of the resin package has a recess and a groove leading from the recess to the end of the resin package.

[0026]

The step of flattening the resin package according to the first aspect of the invention provides a semiconductor package whose bottom surface is flattened, that is, a semiconductor package that does not cause positional displacement during mounting or lead height variation.

The bottom surface of the semiconductor package according to the second aspect of the present invention is formed of the surface of a flat metal plate or ceramic plate, thereby preventing positional deviations and variations in lead height during mounting.

In the third aspect of the invention, the protrusion on the bottom surface of the semiconductor package prevents displacement during mounting and absorbs deformation even if the semiconductor package is deformed during soldering.

The recesses and grooves on the bottom surface of the semiconductor package in the invention as claimed in claim 4 improve the positional stability of the semiconductor package during temporary fixing, and also restrict the outflow direction of the adhesive to prevent the adhesive from reaching the leads. Prevents adhesion.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, 8a and 8b are parts to be removed by mechanical grinding, and the other parts are denoted by the same reference numerals and are the same as those shown in FIG. 17.

In this case, parts 8a and 8b of the semiconductor package as shown in FIG. 18 manufactured through the resin sealing process are removed by grinding, and the bottom surface of the resin package 5 as shown in FIG. This results in a flattened semiconductor package. Therefore, in the process of mounting on the printed wiring board 7, misalignment of the semiconductor package due to poor temporary fixing and poor soldering due to variations in the height of each lead 3 can be prevented.

In the above embodiment, the bottom surface of the resin package 5 is ground after the resin sealing process, but as shown in FIG. 10 may be arranged. In this case, the semiconductor package is formed such that the bottom surface of the metal plate or ceramic plate 10 having a flat bottom surface is exposed at the bottom of the resin package 5. Metal plate or ceramic plate 10 so arranged
is embedded in the resin package 5 in the resin sealing process.

Further, as shown in FIG. 3, the die pad 4 on which the semiconductor element 1 is mounted may be made thick so that the bottom surface of the die pad 4 is exposed at the bottom of the resin package 5.

FIGS. 4 and 5 are plan views (viewed from the bottom) of semiconductor packages according to other embodiments of the present invention. The one shown in FIG. 4 is of four-sided type, and the one shown in FIG. 5 is of two-sided type. In the figure, 11 is a hemispherical projection provided on the bottom surface of the resin package 5. Such protrusions 11 are integrally formed when the resin package 5 is molded in the resin sealing process. Further, FIG. 6 is a cross-sectional view taken along the line A-A of the structure shown in FIG. 4 or FIG. 5, and in the figure,
12 indicates an adhesive for temporary fixing.

FIG. 6(a) shows the case where the semiconductor package is bent downward, and FIG. 6(b) shows the case where the semiconductor package is bent upward. In either case, the protrusion 11
is the printed wiring board 7 before the bottom of the resin package 5.
Since it is in contact with the surface, the adverse effects caused by warping are prevented during mounting. That is, the adhesive 12 allows the semiconductor package to be temporarily attached to the printed wiring board without any problem.

Furthermore, even if the semiconductor package obtained in the resin sealing process is not warped and can be temporarily attached without any problems, the high temperature atmosphere during the soldering process may cause damage to the semiconductor package.
As already mentioned, the semiconductor package may be thermally deformed. When the semiconductor package warps due to thermal deformation, when the solder melts and then solidifies in that state (the solidification temperature of eutectic solder is 183°C), the heights of the leads 3 will be uneven and soldered. I have already mentioned that there is a possibility that However, in this case, the protrusion 11 on the bottom surface of the resin package 5 acts to keep the height of each lead 3 constant. Therefore, there is no need to pay attention to deformation of the semiconductor package due to heat.

Note that in the above embodiment, the hemispherical protrusion 11
7 and 8, a total of four of these are provided at the four corners of the rectangular bottom of the semiconductor package. It may be. Or as shown in Figure 9,
A total of six may be provided.

Furthermore, in the above embodiment, the resin package 5
Although the protrusion 11 has been described as being integrally molded when molding, the hemispherical protrusion is manufactured in a process different from the resin sealing process, and is adhered to a predetermined position on the bottom surface of the resin package 5. You can do it like this.

In the above embodiment, the hemispherical protrusion 1
Although the case where 1 is arranged has been described, the protrusion may have a conical shape, a triangular pyramid shape, or a polygonal pyramid shape,
In those cases as well, the same effects as in the above embodiments can be achieved.

FIG. 10 is a sectional view showing a semiconductor package according to still another embodiment of the present invention. In the figure,
21 is a cylindrical projection provided on the bottom surface of the resin package 5. Such a protrusion 21 is integrally formed when the resin package 5 is molded. Alternatively, this can be realized by bonding a separately manufactured cylindrical protrusion to the resin package 5.

FIGS. 11 and 12 are plan views of the semiconductor package shown in FIG. 10. The one shown in FIG. 11 is of two-sided type, and the one shown in FIG. 12 is of four-sided type. In each figure, the right side of the center line is a view viewed from the bottom, and the left side is a view viewed from the top.

In this case, the protrusion 21 and each lead 3 shown in FIG. 4 support the semiconductor package. Therefore, when mounting the semiconductor package on the printed wiring board 7, the protrusions 21
When the resin package 5 contacts the printed wiring board 7, a gap at a constant interval is formed between the bottom surface of the resin package 5 and the printed wiring board 7. Therefore, the height of the semiconductor package at the time of mounting is determined to a predetermined value without finely adjusting the load on the semiconductor package or the amount of adhesive 12 applied.

In the above embodiment, a semiconductor package was described in which four cylindrical protrusions 21 were provided. However, if the semiconductor package can be stably temporarily fixed, the protrusions 2
The number of 1's may be 4 or more. Further, the protrusion 21 is
It may be in the shape of a triangular prism or other polygonal prism, and the same effect as in the above embodiment can be achieved even when such a shape is provided.

[0044] In the above embodiment, a case was explained in which a cylindrical projection 21 was provided, but a beam-shaped spacer 22 may also be provided as shown in FIGS. 13 and 14. Such a spacer 22 is integrally formed when the resin package 5 is molded. Alternatively, this can be achieved by bonding a separately manufactured spacer to the resin package 5. In addition,
In FIGS. 13 and 14, the right side of the center line is a view viewed from the bottom of the semiconductor package, and the left side is a view viewed from the top. In addition, A- of the one shown in FIG. 13 or FIG.
The A cross section is also as shown in FIG.

Even when the semiconductor package has such a structure, the bottom surface of the resin package 5 and the printed wiring board 7
A gap at a constant interval is formed between the two. Furthermore, Figure 1
3, in the case of a two-sided semiconductor package, the adhesive 12 can flow out from the two sides (openings) where the leads 3 are not provided. Further, as shown in FIG. 14, in the case of a four-sided semiconductor package, the adhesive 12 can flow out from the four corners (openings) of the rectangle. Therefore, when more than the appropriate amount of adhesive 12 is supplied, the adhesive 12 flows out from these openings, so that the adhesive 12 of the lead 3 is prevented from adhering.

In each of the above embodiments, the case where a protrusion is provided on the bottom surface of the resin package 5 has been described, but as shown in FIGS. 15 and 16, the bottom surface of the resin package 5 is recessed and the resin The surface may have grooves communicating with two sides or four corners of the package 5. Such recesses 23 and grooves 24 are formed when the resin package 5 is molded. In addition, FIGS. 15 and 16
In the figure, the right side of the center line is a view viewed from the bottom of the semiconductor package, and the left side is a view viewed from the top.

When the semiconductor package has such a structure, the bottom surface of the semiconductor package and the printed wiring board 7
are in direct contact over a wide area. Moreover, since the adhesive 12 accumulates in the recess 23, stable temporary fixing can be achieved using a small amount of the adhesive 12.

As shown in FIG. 15, in the case of a two-sided semiconductor package, the adhesive 12 can flow through the grooves 24 from the two sides where the leads 3 are not provided. Further, as shown in FIG. 16, in the case of a four-sided semiconductor package, the adhesive 12 can flow through the grooves 24 and flow out from the four corners of the quadrilateral. Therefore, in this case as well, when the adhesive 12 is supplied in an amount larger than the appropriate amount, the adhesive 12 flows out from these openings, so that the adhesive 12 of the lead 3 is prevented from adhering.

[0049]

As described above, according to the invention as set forth in claim 1, the method for forming a semiconductor package is a method that includes the step of flattening the bottom surface of the resin package created in the resin sealing step. Therefore, it is possible to obtain a semiconductor package that does not cause misalignment or variation in lead height when mounted on a printed wiring board.

According to the second aspect of the invention, since the semiconductor package has a structure in which the flat surface of the metal plate or ceramic plate is exposed at the bottom of the resin package, mounting on a printed wiring board is easy. This has the effect of making it possible to perform surface mounting while preventing positional deviations and variations in lead height.

According to the third aspect of the invention, since the semiconductor package has a structure in which the protrusion is provided on the bottom surface of the resin package, the process of resin sealing and soldering can be easily performed.
Even if the semiconductor package warps, it is possible to obtain a package in which the warp does not adversely affect temporary fixing or soldering.

According to the fourth aspect of the present invention, the semiconductor package has a concave portion on the bottom surface of the resin package and a groove leading from the concave portion to the end of the resin package, so that it is easy to use when temporarily fixing the semiconductor package. This has the effect that it can be temporarily fixed to a printed wiring board stably using less adhesive, and can prevent the adhesive from adhering to the leads.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a semiconductor package obtained using a semiconductor package forming method according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a semiconductor package according to an embodiment of the present invention.

FIG. 3 is a sectional view showing a semiconductor package according to another embodiment of the invention.

FIG. 4 is a plan view showing a four-sided semiconductor package according to still another embodiment of the present invention.

FIG. 5 is a plan view showing the same two-sided semiconductor package.

FIG. 6 is a sectional view taken along line AA of the device shown in FIG. 4 or 5;

FIG. 7 is a plan view showing a four-sided semiconductor package according to still another embodiment of the present invention.

FIG. 8 is a plan view showing the same two-sided semiconductor package.

FIG. 9 is a plan view showing a semiconductor package having six protrusions having two sides.

FIG. 10 is a sectional view showing a semiconductor package according to still another embodiment of the present invention.

FIG. 11 is a plan view showing the same two-sided semiconductor package.

FIG. 12 is a plan view showing a similar four-sided semiconductor package.

FIG. 13 is a plan view showing a two-sided semiconductor package according to still another embodiment of the present invention.

FIG. 14 is a plan view showing a similar four-sided semiconductor package.

FIG. 15 is a plan view showing a two-sided semiconductor package according to still another embodiment of the present invention.

FIG. 16 is a plan view showing a similar four-sided semiconductor package.

FIG. 17 is a cross-sectional view showing a conventional semiconductor package.

FIG. 18 is an explanatory diagram showing how the package warps.

[Explanation of symbols]

1 Semiconductor element 2 Gold wire 3 Lead 4 Die pad 5 Resin package 7 Printed wiring board 8a Part removed by grinding process 8b Part removed by grinding process 10 Metal plate or ceramic plate 11 Hemispherical protrusion 12 Adhesive 21 Cylindrical shape protrusion 22 spacer 23 recess 24 groove

Claims (4)

[Claims] 1. A method for forming a semiconductor package, in which a semiconductor element is sealed in a resin package, and after the sealing is completed, the bottom surface of the resin package is flattened by grinding. 2. A semiconductor package in which a semiconductor element is sealed in a resin package, characterized by having a flat metal plate or ceramic plate attached to the bottom of the resin package with one surface exposed. semiconductor package. 3. In a semiconductor package in which a semiconductor element is sealed in a resin package, the resin package comprises:
A semiconductor package characterized by having a plurality of protrusions on its bottom surface. 4. In a semiconductor package in which a semiconductor element is sealed in a resin package, the resin package comprises:
A semiconductor package characterized in that the bottom surface thereof has a recess and a groove leading from the recess to an end of the resin package.