JPH0272656A - Sealing structure for semiconductor element - Google Patents

Abstract

PURPOSE:To maintain moisture resistance and environment resistance and to improve adhesive strength by providing a first sealing part which covers a bonding part and the entire exposed surface of a semiconductor element by using a resin characterized by excellent environment resistance, and providing a second sealing part which covers the entire outer surface of the first sealed part by using a resin characterized by excellent adhesive property with a wiring plate. CONSTITUTION:First sealing 6 is applied on bonding wires 5 and the entire exposed surface of a semiconductor element 1 together by using a resin characterized by excellent moisture resistance and environment resistance. Second sealing 8 is applied so as to cover the entire outer surface of the first sealing part 6 by using a resin characterized by adhesive strength especially with each raw material of a wiring plate 4. As a resin which is used for the first sealing 6 and is characterized by excellent moisture resistance and environment resistance, an epoxy resin whose concentration of incorporated chlorine is low and linear expansion coefficient is approximate to that of the wiring plate 4 and the like is used. Thus the moisture resistance and the environment resistance are maintained, and the fixing strength between the sealing resins and the wiring plate can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a resin sealing structure for a semiconductor element directly bonded onto a wiring board.

(Prior art) In recent years, the technology of directly mounting semiconductor elements directly onto wiring boards has become popular, especially for rigid wiring boards, with the aim of reducing the size, weight, and cost of mounted circuit components. It also tends to be applied to Wire bonding and flip-chip methods are methods for directly mounting semiconductor elements on a wiring board and establishing electrical continuity, but in either case, after bonding, protective sealing is required to prevent moisture and impurities from entering. It is common to do this. It is easiest and most economical to use resin for sealing semiconductor elements, but this resin has good moisture resistance and environmental resistance.
It is necessary to have strong adhesiveness with each material of the wiring board.

FIG. 3 shows a cross-sectional view of a conventional example of the sealing structure for a semiconductor element as described above. In the figure, a semiconductor element 1 is mounted on a wiring board 4 in which a conductive metal foil layer 3 is provided on a substrate 2 made of polyimide resin or the like, and is bonded to the conductive metal foil layer 3 with a bonding wire 5. The entire exposed surface of the semiconductor element 1 is hermetically sealed with the bonding wire 5 and the resin 6. Fig. 4 shows another conventional example, in which a guide frame 7 is used for the purpose of reducing the sealing area and alleviating adhesive interface stress due to substrate deflection, etc.
The other structure is the same as that in FIG. 3, and the same parts are indicated by the same reference numerals.

(Problem to be Solved by the Invention) The mainstream resin 6 used for encapsulating semiconductor elements as described above is a low-chlorine epoxy resin cured with an amine resin. Many of them contain various fillers, compulsions, etc., and have sufficient moisture resistance and environmental resistance.

However, the currently commonly used encapsulation resins are difficult to use, especially when polyimide resin substrates are used for wiring boards.
The adhesion strength is not sufficient, and under normal pressure or pressurized thermal environments such as heat cycle tests and pressure-couple tests, moisture infiltrates from the adhesive interface and often damages the semiconductor element. In particular, in the case of flexible printed wiring boards, if the adhesive strength is weak, the board often peels off from the adhesive interface due to deflection, warpage, etc.

If we simply focus on the adhesive strength with polyimide resin,
Polyimide-based or polyamide-based resins are known to exhibit excellent adhesive properties, but when these resins are used as direct encapsulation materials for semiconductor devices, environmental resistance may be affected due to the hygroscopicity of the resin itself. In addition to expected deterioration, many resins, such as polyimide resins in particular, have a high curing temperature, which has the disadvantage of damaging semiconductor devices.

(Means and effects for solving the problems) The present invention solves the above problems and improves the adhesive strength between a sealing resin and a wiring board when a semiconductor element is resin-sealed, and particularly improves the adhesive strength of a flexible printed wiring board. The objective is to improve environmental resistance and physical adhesion strength against bending, warping, etc. of the substrate.

That is, the entire exposed surface of the semiconductor element along with the bonding portion is covered with a resin with good environmental resistance to perform primary sealing.
Furthermore, the entire outer surface of this primary sealing is covered with a resin that has good adhesion to the wiring board material to form a sealing structure in which primary sealing is performed. In addition, when sealing semiconductor elements such as devices that use external light, a light-transmissive and environmentally resistant resin is used for the primary sealing similar to the above, and a resin with good environmental resistance is used for the secondary sealing. The sealing structure is such that the outer peripheral edge of the primary seal is annularly covered with a resin with good adhesiveness similar to that used in the secondary seal.

As mentioned above, sealing is performed by a combination of primary sealing using a resin with good environmental resistance and secondary sealing using a resin with good adhesive properties, so it has good moisture resistance and environmental resistance, and has strong adhesive strength. It is possible to have a resin-sealed structure having the following.

(Embodiment) FIGS. 1 and 2 are cross-sectional views of an embodiment of the sealing structure for a semiconductor element according to the present invention. In these figures, 1 denotes a semiconductor element as in FIG. 3 of the conventional example. , 2 is a substrate made of polyimide resin or the like, 3 is a conductive metal foil layer, 4 is a wiring board made of these, and 5 is a bonding wire.

In the embodiment shown in FIG. 1, the entire exposed surface of the semiconductor element 1 together with the bonding wires 5 is subjected to primary sealing 6 with a resin having good moisture resistance and environmental resistance, as in the conventional example shown in FIG. It has a structure in which the entire outer surface of the primary seal 6 is covered with a secondary seal 8 using a resin that has good adhesion to each material of the wiring board.

In the embodiment of FIG. 2, - a primary seal 9 is applied as in the embodiment of FIG. 1 above, and a resin similar to that of the secondary seal 8 in the embodiment of FIG. It has a structure in which the outer peripheral edge of the primary seal 9 is annularly covered and a secondary seal 10 is applied.

The resin with good moisture resistance and environmental resistance used for the primary sealing 6 in the example shown in FIG. It is composed of an amine-based material with high crosslinking efficiency, and is mixed with various fillers and coupling agents to impart thixotropic properties.

In the case of the embodiment shown in FIG. 2, the semiconductor element requires external light, and the primary sealing 9 is made of a light-transmitting resin such as silicone. In addition, the resin used for the secondary seals 8 and 10 in FIGS. 1 and 2 is a polyamide-based resin, a polyamide-epoxy-based resin, etc., which cures at a relatively low temperature as a resin with good adhesiveness to the polyimide resin of the substrate. Uses resin.

(Effects of the Invention) As the sealing structure of the semiconductor element according to the present invention, primary sealing using a resin with good moisture resistance and environmental resistance is combined with primary sealing using a resin such as polyimide resin that has good adhesiveness to a substrate. By adopting a sealed structure, moisture resistance and environmental resistance are maintained, and the adhesion strength between the sealing resin and the wiring board is improved. Especially in flexible printed wiring boards, it is possible to prevent deformation such as bending or warping of the board. Peeling and cracking of the sealing resin can be prevented.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views of an embodiment of a sealing structure for a semiconductor element according to the present invention, and FIGS. 3 and 4 are cross-sectional views of a conventional example of a sealing structure for a semiconductor element. 1: Semiconductor element, 5: Bonding wire, 6.9 Primary sealing, 8, 10: Secondary sealing.

Claims (1)

[Claims] 1. In a semiconductor element sealing structure in which a semiconductor element is directly bonded on a wiring board and its entire exposed surface is covered and sealed with a resin along with the bonding part, the sealing with the resin is durable. Primary sealing is done by covering the entire exposed surface of the semiconductor element along with the bonding part using environmentally friendly resin, and secondary sealing is done by covering the entire outside surface of the primary sealing with resin that has good adhesiveness to the wiring board. A sealing structure for a semiconductor element, characterized by comprising: 2. In a semiconductor element sealing structure in which a semiconductor element is bonded directly onto a wiring board and its entire exposed surface is covered and sealed with a resin along with the bonding part, the resin sealing is environmentally resistant and transparent. The primary sealing is performed by using a resin with good adhesiveness to cover the entire exposed surface of the semiconductor element along with the bonding part, and the outer peripheral edge of the primary sealing is covered in an annular shape with a resin that has good adhesion to the wiring board and the primary sealing. 1. A sealing structure for a semiconductor device, comprising a secondary sealing structure.