JPS63265452A - Semiconductor device - Google Patents

Abstract

PURPOSE:To maintain favorably the reliability of moisture resistance even through mounting with solder is carried out by heating wholly after taking moisture absorption, thereby eliminating the crack development of inner resin during its mounting by providing more than one piece of bores or notches reaching tie-bars at the surface or the rear of mold resin. CONSTITUTION:Four corners of a plate-like die pad 2 are held by tie-bars 3 and a semiconductor element 3 is mounted on an upper plane of the die pad 2. The element 3 and lead 4 are bound by bonding wires 5. The element 3 and its surroundings sealed with rectangular mold resin 6 make up a semiconductor package P. Bores 6a reaching a tie-bar 2 are respectively arranged at four positions facing to the tie-bar 2 located on the diagonal in the rear of this resin 6. When a semiconductor device is mounted at a substrate and the like by exposing the entire package P to a high temperature of 200 deg.C or more, a moisture which exists in the interface between the element 3 and the die pad 2 and evaporates is discharged outside from the bores 6a through the tie- bars 1 connecting to the die pad 2.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to semiconductor devices, particularly resin-sealed type devices for surface mounting in which a large number of devices are simultaneously mounted on a substrate, etc., and furthermore, semiconductor packages. The present invention relates to a semiconductor device that is suitable for use in large external dimensions, multiple bins, and thinness.

(Prior Art) Conventionally, the above-mentioned resin-sealed semiconductor device for surface mounting has a twelfth
As shown in Figs.
A semiconductor element 3 is mounted on the upper surface of a flat die pad 2 that supports four sides, two corners, or two sides depending on the case, and a bonding wire 5 (
After bonding as shown in FIG. 14), the semiconductor package P is generally configured by resin sealing with a molding resin 6.

At this time, the tie bar length L between the corner of the die pad 2 and the tip of the tie bar 1 had a value determined by the external dimensions of the semiconductor package P.

However, with the recent trend toward high-density packaging, thin resin sealing for surface mounting such as FP (flat package), PLCC (plastic leaded chip carrier), 5OJ (small outline J-bend package), etc. As the application of semiconductor packages progresses, when surface mounting these semiconductor packages on substrates, a method is being adopted in which the entire semiconductor package is exposed to high temperatures of 200°C or more, unlike soldering heat applied to only individual leads. It has come to the point where

Therefore, the moisture absorbed inside the mold resin 6 is
The interface between the semiconductor element 3 and the mold resin 6 and the die pad 2
At the interface between the die pad 2 and the mold resin 6, explosive vaporization occurs, and high pressure is applied to both interfaces, causing the inside of the mold resin 6 on the lower surface around the die pad 2 and around the semiconductor element 3 to evaporate, as shown in FIG. There is a problem in that cracks 7 may occur inside the mold resin 6 (not shown) on the upper surface of the holder.

This crack 7 not only impairs the appearance but also leads to a significant decrease in the moisture resistance reliability of the semiconductor element 3.

Further, as the number of pins in the semiconductor package increases, the size of the semiconductor package and the size of the semiconductor element are increasing, while the thickness of the semiconductor package is becoming thinner.

For this reason, as shown in Figures 15 and 16, the tie bar 1 that supports the Gui pad 2 has become increasingly long, and the size of the Gui pad 2 has also increased. The flow pressure P of the thermosetting resin causes a phenomenon in which the die pad 2 and the semiconductor element 3 are pushed up from their normal positions (FIG. 15) or pushed down (FIG. 16).

This phenomenon not only damages the wire bonding part due to the vertical movement of the die pad 2, but also causes the upper or lower resin layer of the semiconductor element 3 to become extremely thin, resulting in significant moisture resistance, especially after solder reflow. It also leads to deterioration of the

In order to prevent the above-mentioned cracks from occurring, for example,
-208847, a cylindrical or polygonal hole is made in the molding resin part on the back side of the semiconductor element to form an extremely thin part or a part without molding resin, and when the entire semiconductor package is heated, this internal part is heated. A method has been proposed that allows gas to escape due to the evaporation of moisture.

(Problems to be Solved by the Invention) However, in the method described in JP-A-60-208847, a hole is made in the mold resin on the back side of the semiconductor element, so the die pad on which the semiconductor element is mounted is Not only is the bottom surface exposed to the outside, but the entire semiconductor package is exposed to high temperatures, which reduces the adhesion between the molding resin and the die pad and causes it to peel off in a radial pattern, which is where corrosion begins and damages the semiconductor element. It is considered that there is a risk of having a negative impact on

Additionally, if the flux used during mounting or the processing liquid used in the post-mounting cleaning process enters through the holes, they can easily contaminate the entire back surface of the die pad, resulting in corrosion of the die pad and moisture resistance. It is thought that there are problems such as causing sexual deterioration.

Furthermore, no countermeasures have been taken against upward or downward displacement of the die pad and semiconductor element by the resin mold (hereinafter referred to as floating or sinking of the die pad).

In view of the above, the present invention eliminates the occurrence of internal resin cracks during mounting, so that there is no problem in moisture resistance reliability even when soldering is performed by heating the entire body after moisture absorption, and there is no adverse effect on semiconductor elements. In addition, it is possible to cope with the increase in the size of the package itself, and furthermore, it can eliminate the occurrence of floating or sinking of the die pad, and in this respect, it can also eliminate problems with moisture resistance reliability. The purpose is to provide.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a semiconductor device in which a semiconductor element mounted on the upper surface of a die pad supported by tie bars is sealed with a mold resin. One or more perforations or notches reaching the tie bar are provided on at least one of the back surfaces, for example, only on the back surface of the mold resin, or on both the corresponding front and back surfaces of the mold resin.

(Function) By effectively discharging moisture existing inside the mold resin, especially near the interface between the mold resin and the die pad, to the outside as steam through the perforations or notches under high temperatures during mounting. By forming this outlet in advance to prevent the occurrence of cracks due to this vapor, and by providing this perforation or notch so as to reach the tie bar, it is possible to prevent the perforation or notch from having an adverse effect on the semiconductor element. By providing the above-mentioned perforations or notches at opposite positions on the front and back surfaces of the molded resin, it is possible to prevent the tie bars from moving in the vertical direction through the perforations or notches during resin molding. By pressing and fixing the die pad, it is possible to reliably prevent the die pad from floating or sinking.

(Embodiment) FIGS. 1 and 2 show a first embodiment of the present invention, in which the four corners of a flat die pad 2 are supported by tie bars 1 extending in all directions from the corners. A semiconductor element 3 is mounted on the upper surface. This semiconductor element 3
and lead wire 4 are bonded with bonding wire 5 as shown in FIG.

This semiconductor element 3 and its surroundings are resin-sealed with a rectangular molding resin 6 to constitute a semiconductor package P.

The tie bar 2 on the diagonal line on the back side of this molded resin 6
Perforations 6a reaching this tie bar 2 are provided at four positions facing each other.

As described above, by providing the perforations 6a, when the entire semiconductor package P is exposed to high temperatures of 200° C. or higher and the semiconductor device is mounted on a substrate, etc., the holes 6a are present and evaporated, especially at the interface between the semiconductor element 3 and the die pad 2. By discharging moisture to the outside through the tie bars 1 continuous to the die pad 2 through the perforations 6a, cracks are prevented from forming inside the mold resin 6 due to the pressure of this evaporation.

In addition, cracks normally occur in an arc shape from the center of the four sides of the die pad 2 toward the corners, and are less likely to occur in the corners.
Even if this is provided, there is little risk of cracks occurring from this point.

Furthermore, by providing the perforation 6a in this manner, the distance p between the corner of the die pad 2 and the perforation 6a can be made shorter than the tie bar length determined by the external shape of the semiconductor package P, thereby preventing the occurrence of cracks. The size of the semiconductor package is set to be substantially the same as the size of the semiconductor package surrounded by the line connecting the This is to prevent the occurrence of cracks as much as possible.

The semiconductor device constructed in this way was heated to 85% at 85°C.
After leaving the semiconductor package in an accelerated atmosphere of RH until the moisture content reached a saturated state and immersing it in solder for 2 minutes at 215°C, we examined the occurrence of cracks and found that none of the 10 had any cracks. Ta. On the other hand, according to the results of experiments conducted on conventional products in the same manner as above, cracks occurred in all 10 of them.

3 and 4 show a second embodiment, and the difference from the above embodiment is that this tie bar 1 is placed at one place on the back surface of the molded resin 6 at a position opposite to the tie bar 1 on the diagonal line. The point is that a notch 6b reaching .

In this way, the entire semiconductor package P is heated to 200°C.
When exposed to the above atmosphere, the evaporated moisture inside the mold resin 6 is discharged from the notch 6b.

In addition, as mentioned above, the perforations 68 are made from the back side of the molded resin 6.
The reason why holes 6a etc. are provided is mainly to avoid spoiling the aesthetic appearance, and it is also possible to provide perforations 6a etc. from the surface of the molded resin 6.

Furthermore, it is also possible to coat the upper surface of the semiconductor element 3 with junction coating resin (JCR), polyimide, or the like to further improve the moisture resistance reliability.

FIGS. 5 and 6 show a third embodiment, in which the molded resin 6 is placed at four locations on a diagonal line facing the tie bar 1 from above and below on both the front and back surfaces, and facing each other. Holes 6g and 6a reaching the tie bar 1 are located at the positions.
'.

In this way, the perforations 6a, 6a are formed from the opposing upper and lower sides, respectively.
By providing ', the following effects are obtained in addition to the effects provided from only one of the front and back surfaces.

That is, as shown in FIG. 7, when resin molding is performed, the mold fitting 8.
The tie bar 2 fixed by the mold fitting 8.8 can be pressed and fixed from above and below by the protrusions 8a, 8a of the molded metal fitting 8.8 at an intermediate position (distance II (<L)). To surely prevent a die pad 2 and a semiconductor element 3 supported by this tie bar 1 from being pushed up or down from their normal positions due to the flow pressure of the molten thermosetting resin. Can be done.

Moreover, by reliably preventing the die pad 2 and the semiconductor element 3 from floating or sinking, the semiconductor element 3
The resin thickness on the upper or lower side of the semiconductor package can be maintained at an appropriate value, thereby making it possible to obtain good moisture resistance reliability especially after solder reflow, especially in a large and thin semiconductor package.

In this embodiment, the perforations 6a and 6a' provided on both the front and back surfaces of the mold resin 6 are formed in a tapered shape that becomes smaller as they approach the tie bar 1. It is possible to improve the quality of the molding during molding.

FIG. 8 shows a fourth embodiment, in which the die pad 2 is supported by tie bars 1 extending from the center on the left and right sides of the die pad 2, and two surfaces on the left and right opposite to the tie bars 1 are supported. Perforations 6a and 6a' reaching the tie bar 1 are provided from both the back side and at positions facing each other, respectively.

In the above embodiment, as shown in FIG. 9, by forming a large portion 1a with a large area in a part of the tie bar 1 located at a position corresponding to the perforation 6a, the tie bar 1
Since the width of the perforation 6a is generally narrow, it is possible to ensure that the perforation 6a reaches the tie bar 1 and to improve the appearance.

10 and 11 show the fifth embodiment,
Notches 6b and 6b' reaching the tie bar 1 are provided at two diagonal locations facing the tie bar '1 from above and below on both the front and back surfaces of the molded resin 6, and at positions facing each other. As mentioned above, the perforations 6a, 5a' or the notches 6b, 6b
If ' is provided at one or more places of force and from opposite positions on the front and back surfaces of the mold resin 6, the effect of preventing the die pad 2 and the semiconductor element 3 from floating or sinking can be exhibited.

Further, the upper surface of the semiconductor element 3 may be coated with polyimide or the like to further improve moisture resistance reliability.

〔Effect of the invention〕

Since the present invention has the above-described configuration, when the entire semiconductor package is exposed to a high temperature of 200°C or higher during soldering and mounting, the moisture existing inside the molding resin turns into steam and is released into the package outside. It is possible to prevent cracks from occurring due to this vapor.

Moreover, even in a large semiconductor package, the occurrence of cracks can be made substantially the same as in a small semiconductor package, depending on the position of the perforations, etc., thereby preventing the occurrence of cracks and improving reliability.

Furthermore, since the bottom surface of the die pad on which the semiconductor element is mounted is not exposed to the outside, there is no risk of corrosion. Furthermore, since there are thin tie bars extending from the perforation to the die pad, it is possible to suppress the intrusion of contaminants from the outside. Therefore, the semiconductor element will not be adversely affected by the perforation or the like.

In addition, by providing perforations or notches that reach the tie bars at opposing positions on the front and back surfaces of the mold resin, it is possible to reliably prevent vertical displacement (lifting or sinking) of the die pad and semiconductor element due to the resin mold. This has the effect of eliminating moisture-resistance reliability problems caused by this floating or sinking, especially in large and thin semiconductor packages.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 show a first embodiment of the present invention.
The figure is a sectional view taken along the line I-X in Figure 2, Figure 2 is a back view, Figures 3 and 4 show the second embodiment, and Figure 3 is a cross-sectional view of Figure 4.
-■ line sectional view, Figure 4 is a back view, Figures 5 to 7 show the third embodiment, Figure 5 is a V-V line sectional view of Figure 6,
Figure 6 is a back view (front view), Figure 7 is a sectional view of the manufacturing process, Figure 8 is a back view (front view) showing the fourth embodiment, and Figure 9 is a modification of the tie bar. Back view, No. 10
11 shows the fifth embodiment, and FIG. 10 shows the first embodiment.
Figure 1 is a cross-sectional view taken along the line X-X, Figure 11 is a back view (front view),
12 to 14 show the conventional example, FIG. 12 is a back view, FIG. 13 is a sectional view taken along the line 12+7) FIG. 15 and FIG. 16 are sectional views showing other different conventional examples. DESCRIPTION OF SYMBOLS 1... Tie bar, 2... Die pad, 3... Semiconductor element, 6... Mold resin, 6a, 6a'...
Same perforation, 6b, 6b'...same notch. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 ρ Figure 6 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 Figure 15 Figure 16 Procedure Amendment Book Showa February 1963

Claims (1)

[Scope of Claims] 1. In a semiconductor device in which a semiconductor element mounted on the upper surface of a die pad supported by tie bars is sealed with mold resin, a perforation or cut that reaches the tie bars is provided on at least one of the front or back surface of the mold resin. A semiconductor device characterized by having one or more notches. 2. The semiconductor device according to claim 1, wherein perforations or notches reaching the tie bars are provided at opposing positions on the front and back surfaces of the molding resin, respectively.