JPS62114234A - Sealing method for semiconductor - Google Patents

Abstract

PURPOSE:To seal a semiconductor with high reliability with hermetical seal sufficient in practice by pouring liquid resin sealer and then deforming it under reduced pressure. CONSTITUTION:A substrate is spot-face (dug) in the height of the silicon of a semiconductor chip 2 as semiconductor placing portions 6. A wiring pattern 5 is fed via through holes 4 to the back surface of the organic substrate 1, and led to pins 7. A sealing method includes pouring liquid resin sealer to the portion 6 and the chip 2 and then pouring resin until gold wirings 3 are completely buried. The sealing resin contains optimally liquid epoxy resin to be mixed with a curing agent, a cure accelerator or the like.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to PGA (pin grid array), LCC
It belongs to the field of sealing technology for semiconductor parts of semiconductor packages such as (leadless chip carriers).

[Background Art] Generally, in order to protect a semiconductor chip from external stresses such as temperature, humidity, and shock, the semiconductor device portion thereof is usually sealed.

As the degree of integration of semiconductor devices increases, the packaging of ICs also becomes more diverse. In general, packaging methods can be broadly classified into hermetic sealing and resin sealing. Hermetic sealing involves bonding an IC chip onto a lead frame, connecting the chip and leads with gold wire, and sealing the chip with metal, ceramic, glass, etc. while leaving a space above and below it. This is a method of filling the internal space with inert nitrogen gas or dry air and sealing it. In this method, there is almost no intrusion of moisture from the outside and the semiconductor element is protected from external stresses such as temperature and impact, so the reliability of the semiconductor element is extremely high. Furthermore, in the case of hermetic sealing, there is no problem with thermal linear expansion and the electrical insulation is good, so it was considered to be the most suitable sealing method.

On the other hand, in the case of general-purpose ICs, the shape of pancaging was mainly DIP (dual in-line package) with 16 to 24 pins, but with the increase in integration, various packaging shapes have become available. It's here. PGA, LCC, FP (flat package), etc. have also come to be used in LSI packages with many external pins, such as gate arrays. PGAs with more than 100 pins have also been developed. these are,
Since they have minute circuits and require dimensional stability, hermetic sealing using ceramic materials is often adopted.

The above-mentioned hermetic sealing using ceramics and the like requires expensive materials and takes time to mold, so there has been a demand for a simpler sealing method. The resin encapsulation is attracting attention as a encapsulation method that satisfies this demand. Resin encapsulation is a method of embedding semiconductor elements in resin. Generally, a ceramic substrate is used as the IC substrate, an epoxy resin is used as the sealant, and the semiconductor element is sealed by low-pressure transfer molding. The method has been widely adopted. Although the sealing resin is cheaper than ceramic, it has a large coefficient of linear thermal expansion, and the thermal linear expansion between the two materials will be significantly different, resulting in poor adhesion at the interface and reduced airtightness. However, this resulted in a loss of reliability.

In order to compensate for this drawback, attempts have been made to reduce thermal expansion by adding a large amount of inorganic filler such as silica to the sealing resin, but this has not resulted in fully satisfactory performance.

Under the above circumstances, it has been desired to develop a sealed body that is more economical, has better confidentiality, and is more reliable.

[Object of the Invention] It is an object of the present invention to provide a sealing method for semiconductors that is simpler than the ceramic sealing method described above, has practically sufficient airtightness, and is reliable.

[Disclosure of the Invention] This invention provides a PGA and LCC made using an organic substrate.
Provides a method for encapsulating a semiconductor part of a semiconductor package, such as the following, which uses a liquid resin encapsulant, and after injecting the same, degassing is performed under reduced pressure. It is.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be explained based on drawings showing one embodiment of the present invention.

FIG. 1 is a perspective view of a PGA with a semiconductor chip mounted thereon before sealing, and FIG. 2 is a perspective view showing the PGA of FIG. 1 sealed with resin. Examples of the first organic substrate material include, but are not limited to, glass-based epoxy resin laminates, polyimide resin laminates, paper-based phenolic resin laminates, and the like. The semiconductor mounting part 6 of the PGA package has a gold wire between the semiconductor chip 2 and the wiring pattern 5 of the substrate 1.
It is more convenient to lower the position a little in order to tie it at 3.

Therefore, make a counterbore in the substrate that is about the height of the silicon of the semiconductor chip 2, and place this counterbore in the semiconductor mounting part 6.
shall be. The wiring pattern 5 is guided to the back surface of the organic substrate 1 through the through hole 4 and is electrically connected to the pin 7. In the sealing method, a liquid resin sealant is injected into the semiconductor mounting part 6 and the semiconductor chip 2 until the gold wire 3 is completely buried.

Although the sealing resin used here is not particularly limited, a liquid epoxy resin is most suitable, and a curing agent, a curing accelerator, etc. are mixed therein as appropriate.

The epoxy resin is not intended to be particularly limited, but
Bisphenol A type etc. are used. The curing agent is preferably 2,4-dihydrazine-6-methylamino-S-)riazine (hereinafter referred to as 2.4-HT) or adipic dihydrazide, although it is not intended to be particularly limited. Most preferred is 2.4-HT. The viscosity of the epoxy resin is particularly preferably in the range of 10,000 to 500,000 CP.
It is about S.

Note that since a large number of gold wires 3 are bonded, when injecting the liquid resin sealant into the semiconductor mounting part 6,
Some air will be mixed in. Furthermore, since the sealant itself may contain air, foaming may occur during curing. When foaming occurs, the moisture resistance of the cured product deteriorates, the strength decreases, and eventually the airtightness and reliability decrease. Moreover, the surface shape deteriorates, reducing the commercial value.

Therefore, in order to eliminate foaming, it is effective to provide a defoaming step. That is, a resin-sealed PGA or the like is placed under reduced pressure to degas it. Degassing under reduced pressure is preferably carried out at room temperature, but in some cases, for example, when the sealing resin has a high viscosity and defoaming is difficult, it may be heated to an extent that does not deteriorate the performance of the sealant. The defoaming process is performed using I Tor
As a guideline, the foaming should be completely eliminated by exposing the product to a reduced pressure of R for about 30 minutes, but the degree of reduced pressure and the time are not limited. Defoaming is completed when there is almost no foaming, but it is preferable to completely defoam as much as possible.

After the semiconductor mounting portion 6 is sealed and defoamed in the manner described above, the resin is cured to obtain a resin-sealed PGA 8 as shown in FIG.

Next, in order to examine the performance of the PGA resin-sealed as described above, we conducted a PCT (Pressure Couple Test).
and THB test were conducted and the results are shown in Table 1.

For comparison, the case where degassing under reduced pressure was not performed in the resin sealing process was also investigated and is also listed in the table.

Table 1 [Effects of the invention] This invention provides a pin grid made using an organic substrate.
A method for encapsulating semiconductor parts of semiconductor packages such as arrays and leadless chip carriers, which uses a liquid resin encapsulant and is characterized by degassing under reduced pressure after injecting it, making it easy to use. , and maintains practically sufficient confidentiality, resulting in the provision of a highly reliable semiconductor package.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a PGA mounted with a semiconductor before sealing, and FIG. 2 is a perspective view of the PGA after sealing. 1...Organic substrate 2...Semiconductor 3...Gold wire 4...Through hole 5...Wiring pattern 6... - Counterbored portion 7...Pin 8...Sealing resin. Figure 1 Figure 2

Claims (1)

[Claims] (1) A method for sealing a semiconductor part of a semiconductor package such as a pin grid array or a leadless chip carrier made using an organic substrate, which uses a liquid resin sealant, and after injecting the liquid resin sealant, A semiconductor encapsulation method characterized by degassing under reduced pressure.