JPH0492459A - Resin sealing type semiconductor device - Google Patents

Abstract

PURPOSE:To lighten thermal stress by a method wherein a body constitution part is sealed by a first sealing resin material, this first sealing resin material is made to be covered with a second sealing resin material and a coefficient of linear expansion of the second sealing resin material is smaller set up than a coefficient of linear expansion of the first sealing resin material. CONSTITUTION:For instance, in the case where the packaging final shape is not to be changed, it is necessary to design to maintain the thickness of the package to some extent. Now, in the case where a double mold construction is adopted, thickness of a first sealing resin material 16 is thinly constituted to near a molding limit and later to be molded to the thickness required by a resin with a second sealing resin material 17. At this time, when material selection is performed so that a linear expansion coefficient alpha2 of the second sealing resin material 17 may become smaller at least than a linear expansion coefficient alpha1 of the first sealing resin material 16, so far as a resin cross section A of a single mold and the sum A' of a cross section 1 of the first sealing resin material 16 and a cross section A2 of the second sealing resin material 17 of the double mold are equal, thermal stress generated in the interface between a semiconductor element 11 and resin can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application j This invention is directed to sealing a main body component including a semiconductor element and a terminal lead-out mechanism of the semiconductor element with a first sealing resin, and further sealing this with a second sealing resin. The present invention relates to a resin-sealed semiconductor device that is sealed with a sealing resin.

[Prior Art] A semiconductor device in which a main body component including a semiconductor element is sealed with a first sealing resin, and the first sealing resin body is further sealed with a second sealing resin. For example, as a structure aiming at improving moisture resistance, JP-A-63-42
This method is disclosed in Japanese Patent Application Laid-open No. 151 or Japanese Patent Application Laid-Open No. 64-37043. Furthermore, as shown in Japanese Patent Application Laid-Open No. 64-91498, it has been considered to surround the connector housing with a second sealing resin body on the outer periphery to improve its functionality.

However, by further sealing the first sealing resin body with a second sealing resin body, it is impossible to increase the thermal stress generated due to cold stress. A peeling phenomenon may occur between the resin and the resin stopper. This results in deterioration in moisture resistance, further deterioration in functionality, and problems in reliability.

Also, as shown in Japanese Patent Application Laid-Open No. 1-309357,
It has been considered that the first sealing resin body is made of a soft resin material with a low elastic modulus.

However, in this case, a heat sink made of, for example, aluminum cannot be integrally constructed, and the thermal conductivity of the first sealing resin body also deteriorates. Therefore, there is a loss of function due to heat generation in the semiconductor chip portion, which causes a decrease in reliability.

[Problem to be solved by the invention] This invention was made in view of the above points, and the first problem is
Even if the structure is double-sealed with a sealing resin body and a second sealing resin body, the semiconductor element sealed with the first sealing resin body and the first sealing resin body It is an object of the present invention to provide a resin-sealed semiconductor device in which thermal stress generated during the process is effectively alleviated, and moisture resistance and reliability are reliably improved.

[Means for Solving the Problems] A resin-sealed semiconductor device according to the present invention includes a semiconductor element,
The main body component including other terminal lead-out mechanisms is sealed with a first sealing resin body, and the first sealing resin body is covered with a second sealing resin body, The linear expansion coefficient α2 of the second sealing resin body is set smaller than the linear expansion coefficient αl of the first sealing resin body.

[Function] In a resin-sealed semiconductor device configured in this way,
Since the degree of contraction of the second sealing resin body that occurs during cooling is smaller than the degree of contraction that occurs in the first sealing resin body, the effect of the second sealing resin body during cooling , the compressive stress of the first sealing resin body is relaxed. Therefore, thermal stress generated between the semiconductor element sealed by the first sealing resin body and the first sealing resin body is effectively reduced. therefore,
The peeling phenomenon that occurs between the first sealing resin and the semiconductor element is suppressed, and reliability is significantly improved.

[Embodiments of the invention] Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows its cross-sectional structure, and the semiconductor element 11 is constructed using, for example, silicon as a base material. The lead 14 is made of a conductive material such as 42 alloy as a base material.
The lead 14 and the lead-out terminal portion of the semiconductor element 11 are connected to a bonding wire 1 made of Ag1Au, Cu, etc.
Connected by 5. Although the lead 14 is not shown in detail, it is used for connection between this semiconductor device and the outside of this semiconductor device.

Here, the frame 12 on which the semiconductor element 11 is mounted and the leads 14 are usually formed as a lead frame by pressing, photoetching, etc. from a single plate.

The main body components of the semiconductor device including the semiconductor element 11, leads 14, bonding wires 15, etc. are sealed with a first sealing resin body 1B made of epoxy resin or the like, and each of the main body components The components are fixed by this first sealing resin body 16.

This first sealing resin body 6 is further provided with a second sealing resin body 17 made of thermoplastic resin such as PPS or PBT, or thermosetting resin such as epoxy or silicone.
It is sealed and fixed by.

Here, protruding bands 18 are formed around the upper and lower surfaces of the first sealing resin body 16 so as to surround them, as shown in FIG. 2(A). The protruding band 18 is formed when the first sealing resin body 16 is molded when sealing the main body component of the t-J semiconductor device.

The protruding band 18 may be formed only on one surface of the first sealing resin body 16, or may be formed continuously over the entire circumference as shown in FIG. 2(B). There is no need to form it.

The second sealing resin body 17 is connected to the first sealing resin body 1.
It is molded so that the protruding band 18 formed at 6 is embedded, so that the first and second sealing resin bodies 16 and 17 are integrally joined.

In such a semiconductor device, the thermal expansion coefficient α2 of the second sealing resin body 17 is equal to the thermal expansion coefficient α1 of the first sealing resin body 1B.
is set smaller than.

When the resin-sealed semiconductor device is cooled from a high temperature state, the difference in linear expansion coefficient between the semiconductor element 11 and the resin constituting the first sealing resin body 16 causes the semiconductor element 11 and the first
Thermal stress is generated at the interface of the sealing resin body 16. This thermal stress causes separation of the interface between the semiconductor element 11 and the first sealing resin body 16, shortens the life of the bonding wire 15, and causes passivation cracks.

The thermal stress generated at the interface in this way can be summarized as follows based on the relationship between the linear expansion coefficient α1 of the first sealing resin body 16 and the linear expansion coefficient α2 of the second sealing resin body 17. Become.

FIG. 3 shows a model of the semiconductor device shown in FIG. 1 with a three-layer structure, in which the cross-sectional area of each layer is shown as AX, the Young's modulus as E X , and the X-ray expansion coefficient as α8.

In this model, the semiconductor element 11, the first and second sealing resin bodies 16 and 17 when a temperature change of ΔT is applied
The thermal stress generated in σs1σ1 and σ
2, it is expressed by the following determinant.

The stress σS applied to the semiconductor element 11 is determined as follows.

as = K (C+E2 A2 ((22-al)
1 Therefore, the linear expansion coefficient α2 of the second sealing resin 17 is “
By setting al>α21, σS can be made small.

The fourth factor shows the relationship between the linear expansion coefficient α2 of the second sealing resin body 17 and thermal stress. What this figure means is that by reducing the coefficient of linear expansion α2 of the second encapsulating resin body 17, the thermal stress generated at the interface between the semiconductor element 11 and the first encapsulating resin body 16 is reduced. This is something that can be done.

That is, in the conventional example, the thermal stress generated at the interface between the semiconductor element and the first sealing resin body during cooling is σ2csσ1
(Points C and 1 in the figure) However, if the configuration shown in the example is used, the linear expansion coefficient α2 of the second sealing resin body 170 is set to the linear expansion coefficient α2 of the first sealing resin body 16. By making the rate smaller than α1, the generated thermal stress can be reduced to σ2b (point b in the figure).
can be reduced to Furthermore, in a structure that is not sealed by the second sealing resin body 17, the thermal stress σ0 (point O in the figure) generated at the interface between the semiconductor element 11 and the first sealing resin body 15 during cooling is , the linear expansion coefficient α2 of the second sealing resin body 17 can be reduced to σ2a (point a in the figure).

Here, the thermal stress σ0 when the second sealing resin body 17 is not present
The result is as follows.

ao = K fc + E2 A2 (α2-at) l
Since A2-0, ao -KC -EI Al (al -as) Next, when there is a second sealing resin body ]7, finding the linear expansion coefficient a'o that becomes σO is as follows. become.

(EI Al +E2 A2) (al -as
) +E2 A2 (cro -crl)Convert the above formula to a
The solution for o (and the following.

When the second resin encapsulant 17 is not present, the frame cut surface is exposed, and the moisture resistance decreases due to moisture infiltration from this end surface.
By performing double sealing with the first sealing resin body 16 and the second sealing resin body 17, the end face of the frame 12 is covered, and moisture resistance can be improved.

Furthermore, by making the linear expansion coefficient α2 of the second sealing resin body 17 smaller than the linear expansion coefficient a1 of the N1 sealing resin body 1B, the effect of reducing thermal stress is exhibited in the following cases. be done.

First of all, if the final shape of the package is not changed, it is necessary to design the package to maintain a certain thickness in order to maintain its mechanical strength or ensure moisture resistance. Therefore, when a double mold structure is adopted, the thickness of the first sealing resin body 16 is reduced to near the molding limit, and then the thickness of the second sealing resin body 17 is reduced to the thickness required for the design. Shape. At this time, if the material is selected so that the linear expansion coefficient α2 of the second sealing resin body 17 is smaller than the linear expansion coefficient αI of the first sealing resin body 16, the cross-sectional area of the resin of the single mold is A. , the cross-sectional area At of the double molded first sealing resin body 16 and the second sealing resin body 1
As long as the sum A' (-AI+A2) of 7 and the cross-sectional area A2 is equal, the thermal stress generated at the interface between the semiconductor element II and the resin can be reduced.

Second, when the package becomes larger due to molding of the second sealing resin body 17, if the package has a shape with a margin of thickness considering the molding limit as in the first case, the second sealing resin body 17 Expansion of the size by molding the sealing resin body 17,
This can be compensated for by reducing the noise of the first sealing resin body 16. However, the first sealing resin body 1
6 is reduced to near the forming limit, the second
It is inevitable that the sealing resin body 17 increases the size. Therefore, by selecting a material with a linear expansion coefficient α2 of the second sealing resin body 17 that is smaller than α0 mentioned above, even if the package is enlarged, the thermal stress will be lower than that of a single molded package. It is also possible to reduce the

In terms of material properties, thermal stress can be reduced if such a relationship is satisfied. However, in order to further enhance this thermal stress reduction effect, the protruding band 18 is formed at least on the edge of the upper surface or the edge of the lower surface of the first sealing resin body I6. Sealing resin body 16 and second sealing resin body 1
By making the anchor effect at the interface of layer 7 exerted, the effect of the − layer can be expected.

In order to improve the adhesion or adhesion between the first sealing resin body 16 and the second sealing resin body 17, in the previous embodiments, the projecting band 1B is attached to the first sealing resin body 16. was formed on the surface of However, this structure can be selected arbitrarily; for example, as shown in FIG.
may be formed. Further, as shown in (B) of the figure, a recess 182 is formed in the center portion of the upper surface or lower surface of the first sealing resin body IB, and (C)
As shown in the figure, the protruding band 18 and the groove 181 may be formed in combination.

The protruding band 18, full 181, and recess 18 formed in this way
2 is formed when the first sealing resin body 1B is integrally molded, and after the first sealing resin body 16 is molded, the first sealing resin body 16 is removed by cutting, adhesive, etc. It is also possible to provide fixing means on the surface. For example, as shown in FIG. 6(D), an adhesive 183 is applied to the surface of the first sealing resin body 16, and the adhesive 183 connects the first sealing resin body 16 and the second sealing resin body. Improves adhesion with 17. Also (E)
As shown in the figure, unevenness 18 is formed on the surface of the first sealing resin body 16.
4, and the unevenness 184 forms the second
The first sealing resin body 17 may be effectively adhered to the first sealing resin body 16.

When the second sealing resin body 17 is formed of thermoplastic resin, generally for the purpose of improving the strength of the resin itself,
Contains filler such as glass fiber. The filler is oriented along the flow of the resin during molding, and therefore a phenomenon occurs in which the coefficient of linear expansion is different in the flow direction (orientation direction) of the resin and in the direction perpendicular thereto.

Here, if the coefficient of linear expansion in the orientation direction is α211 and the coefficient of linear expansion in the direction perpendicular to this is α21, then α211<al
” and “α21<α1”, the structure of the first embodiment shown in FIG. The objective can be achieved by making the cross-sectional area A1 of the plane perpendicular to the orientation direction smaller than the cross-sectional area All in the orientation direction, as shown in FIG.

In this figure, the thermal stress generated at α21 and AI is σ
b, and the thermal stress generated at α211 and All is σ
C, which is smaller than the thermal stress σa generated in the conventional structure.

Here, σa1σb1σC are each expressed by the following equations.

(All-A2, Al-KA2) By designing the cross-sectional area A1 in the direction perpendicular to the orientation direction to be twice the cross-sectional area All in the orientation direction, thermal stress can be lowered compared to the conventional one.

ac<aa (,',(!211 <al from ac
-cya <O)X I(1-4C)Es As(α1
−α5)−K(EIA1+E2A2+EsAs)×(α
21-α1) -C[Es As(al-as)-K((EI Al
+E2 A2((221-aL)+Es As(α21
-al)) ] ≧0 Therefore, σO≧σb FIGS. 8 to 13 respectively show examples that take these points into consideration. A depression 40 is formed in at least the upper surface or the lower surface of the sealing resin body 17, and the cross-sectional area All in the orientation direction is made larger than the cross-sectional area AI perpendicular to the orientation direction. Here, the diagram (D) in each figure shows the directionality of the linear expansion coefficient, and the length of the arrow represents the magnitude of the absolute value.

FIG. 9 shows an open portion 41 in one direction of the second sealing resin body 16.
is formed to release the thermal stress generated by the coefficient of linear expansion α2I in the direction perpendicular to the orientation direction. Furthermore, FIG. 10 shows a configuration in which at least one slit 42 is formed along the orientation direction of the second sealing resin body 17, and the heat generated by the linear expansion coefficient α21 in the direction perpendicular to the orientation direction is I'm trying to release stress.

In the example shown in FIG. 11, the open portion 43 is formed by combining the examples shown in FIGS. 8 and 9. In FIG. 12, a slit-like opening 44 is formed in the second sealing resin body 17, which is a combination of the example shown in FIG. 8 and the example shown in FIG.

In the example shown in FIG. 13, at least one protrusion 45 is formed on at least the upper surface or the lower surface of the first sealing resin body 16 in a direction perpendicular to the orientation direction, and An anchor effect is activated, and the anchor effect is prevented from acting in a direction perpendicular to the orientation direction.

This protrusion 45 may have a groove.

Although various modified examples have been shown above, it is of course not limited to the examples shown here, and at least one of the second sealing resin bodies 17
By making the linear expansion coefficient in two specific directions (orientation direction, etc.) smaller than the linear expansion coefficient of the first sealing resin body 18, damage to the semiconductor element 11 portion can be reliably prevented. Structures such as grooves and protrusions formed to enhance the effect can also be constructed by combining various examples shown so far. Furthermore, if there is anisotropy in the coefficient of linear expansion, this can be dealt with by appropriately combining the structures shown in the embodiments.

[Effects of the Invention] As described above, according to the resin-sealed semiconductor device according to the present invention, the shape of the first sealing resin body is devised, and the second
By devising the shape and material of the first encapsulating resin body, the thermal stress generated between the main body structure including the semiconductor element embedded therein and the first encapsulating resin body can be alleviated. , the reliability of this semiconductor device is effectively improved.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional configuration diagram illustrating a resin-sealed semiconductor device according to an embodiment of the present invention, and FIG. 2 (A) and (B)
are diagrams showing the appearance of the first sealing resin body of this example, Figure 3' is a diagram showing a model for explaining thermal stress, and Figure 4 is a diagram showing the state of thermal stress explained by this model. 5 is a diagram showing a model of the semiconductor device shown in the example, FIGS. 6A to 6E are diagrams each showing an example of the cross-sectional structure of the semiconductor device, and FIG. Figures 8 to 13, which illustrate the effect on the cross-sectional area of the sealing resin body in No. 2, respectively show still other embodiments of the present invention, in which (A) is a plan view and (B) is a plan view. and (C) are cross-sectional views taken along line b-b and line c-c in figure (A), respectively;
(D) is a diagram showing the directionality of linear expansion coefficient. 11... Semiconductor element, 12... Frame, 14...
・Lead, 15...Bonding wire, 16...
First sealing resin body, 17...Second sealing resin body, 18...Protruding band, groove,...Four parts,...Adhesive,...Irregularities, 40...Indentations , L 43. 44...opening part, 42...slit.

Claims (7)

[Claims] (1) A first sealing resin body that integrally seals the main body components including the semiconductor element, leads, and bonding wires that connect these two, and the outer peripheral part of this first sealing resin body. a second formed to cover at least a portion of the
a sealing resin body, and the first and second sealing resin bodies are arranged such that a linear expansion coefficient of the second sealing resin body is smaller than a linear expansion coefficient of the first sealing resin body. 1. A resin-sealed semiconductor device characterized in that a molded resin body is selected from the following. (2) The resin sealing according to claim 1, wherein an uneven shape is formed on at least one surface of the first sealing resin body, and the first sealing resin body is bonded to the second sealing resin body at the uneven portion. type semiconductor device. (3) A first sealing resin body that integrally seals the main body components including the semiconductor element, leads, and bonding wires that connect these two, and the outer peripheral part of this first sealing resin body. a second formed to cover at least a portion of the
a sealing resin body, the coefficient of linear expansion of the second sealing resin body in a specified direction corresponding to the direction in which the fibers are arranged is higher than that of the first sealing resin body. the first and second
1. A resin-sealed semiconductor device characterized in that a molded resin body is selected from the following. (4) The resin-sealed semiconductor according to claim 3, wherein the cross-sectional area of the second sealing resin body in a direction perpendicular to the specified direction is set larger than the cross-sectional area along the specified direction. Device. (5) An opening through which the first sealing resin body is exposed is formed in at least one direction perpendicular to the specified direction of the second sealing resin body. Resin-sealed semiconductor device. (6) forming a groove in which the first sealing resin body is exposed along the specified direction of the second sealing resin body; 4. The resin-sealed semiconductor device according to claim 3, wherein the resin-sealed semiconductor device is divided into parts. (7) The uneven shape formed on the first resin sealing body is
4. The resin-sealed semiconductor device according to claim 3, wherein the resin-sealed semiconductor device is formed to extend in a direction perpendicular to the specified direction.