JPH01129425A - Manufacture of semiconductor package - Google Patents

Abstract

PURPOSE:To obtain an excellent semiconductor package without push-in operation by positioning a substrate, in which a semiconductor element loaded on the surface is coated previously with a resin sealing medium, onto a liquefied resin sealing medium admitted into a case made of, a metal, an opening of which is directed upward, from the semiconductor-element loading surface side and leaving the substrate to stand and curing the resin sealing medium. CONSTITUTION:A substrate 1 in which a semiconductor element 2 loaded on the surface is covered previously with a resin sealing medium 5 is placed onto a liquefied resin sealing medium 5 in a case 8 made of a metal, an opening of which is directed upward, from the loading surface side and left to stand, thus sinking the substrate into the sealing medium, then creeping the resin sealing medium 5 from the loading surface side to the end face side. The substrate is left to stand, and is not turned upside down and the resin sealing medium is cured under the state. 40-70wt.% fillers are included and not more than 25wt.% particles, mean particle size of which extends over 13mum or less and size distribution of which extends over 4mum or less, and not less than 25wt.% particles, size distribution of which extends over 15-30mum, are contained in the composition of the resin sealing medium, which has fluidity when the medium is left to stand at room temperature and hardly flows on heating curing.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a method for manufacturing a semiconductor puff cage [Background Art] Conventionally, in order to seal a semiconductor element that requires a large number of pins,
A PGA (pin grid array) type puff cage is used. Most PGAs are hermetically sealed using ceramics, in contrast to DIPs (dual in-line packages), which are mostly resin-sealed. This increases the cost and prevents the widespread use of PGA type packages.

In recent years, plastic PG has been developed using printed wiring board processing.
A type package is proposed. This type can be expected to significantly reduce costs compared to the hermetically sealed type made of ceramic.

FIGS. 2(a) and 2(t)l show the semiconductor element 2 mounted on the substrate 1 and wire-bonded to the electric path 3 formed on the surface of the substrate 1. 4 is a bonding wire. By sealing this semiconductor element 2 with resin, it can be used as a component. As shown in Fig. 3, the most preferable resin sealing structure is one in which the entire space between the M case 8 and the board 1 is filled with the resin sealant 5 without any gaps; It is being

The reason is that this package is superior to other packages in the following points.

■ The interface between the resin sealing material and the substrate, which is a path for moisture to enter, is long from the package surface to the internal semiconductor element, and the metal case does not allow moisture to pass through, so it has excellent moisture resistance.

■ Components with consistent dimensions can be obtained, and the appearance after mounting on a wiring board is good.

■ Since the metal case is on the surface, it is easy to mark the surface.

■ Plastic PGA packages without a metal case go through an electroplating process, so the conductors are exposed on the end faces of the package, and static electricity countermeasures are required when handling them. However, in the structure shown in Figure 3, the end face insulation is It is well maintained and is easy to handle as a component.

A method for manufacturing a semiconductor package with this structure is, for example, as shown in FIGS. 4(a) to 4(d), in which a semiconductor element 2 mounted on the surface of a substrate 1 is covered in advance with a resin sealing material 5. On the other hand, gold Ws placed with the opening facing upward
A liquid resin encapsulant 5 is placed in the J case 8, and the substrate 1 is pushed into the resin encapsulant 5 from its semiconductor element mounting surface side to be integrated, and then hardened. By this method, a highly reliable semiconductor package that does not contain bubbles can be obtained.

However, it has been found that the above method for manufacturing a semiconductor package has the following problems. In this manufacturing method, as shown in FIG. 4(C), it is necessary to apply pressure P to the substrate 1 and push it into the resin sealing material 5 in the metal case 8. However, if the pushing method is weak, the resin sealing material may not wrap around the end surface of the substrate 1, as shown in FIG. 5(a), and the end surface of the substrate 1 may not be sealed, resulting in poor reliability. This is the cause of variation. On the other hand, if the pressure is stronger, Figure 5 (
As shown in b), the resin sealing material 5 flows too much and gets entangled around the pins 7 on the back side of the board 1, and as shown in FIG. If it becomes dirty, the appearance will be poor, although there is no problem in terms of reliability.

To prevent this, pressure P
A very high level of skill is required to delicately adjust the size of the image and the amount of time it is added. Moreover, pressing takes time and is not suitable for industrial production. Furthermore, since the fluidity of the liquid resin sealant is not uniform, it is necessary to delicately adjust the pressure and time each time the resin sealant is changed, making mechanization difficult.

[Purpose of the invention]

In view of the above, an object of the present invention is to provide a method for manufacturing a semiconductor puff cage with high industrial productivity.

[Disclosure of the invention]

In order to achieve the above-mentioned object, the present invention includes a substrate having a semiconductor element mounted on its surface, which is covered with a metal case from the side on which the semiconductor element is mounted, while maintaining a desired distance from the case. To obtain a semiconductor package in which the semiconductor element is sealed by filling with a resin encapsulant, a substrate on which the semiconductor element mounted on the surface is previously covered with the resin encapsulant is placed on the semiconductor element mounting surface. From the side
Gold with the opening facing upward]F The gist of the present invention is a method for manufacturing a semiconductor buff cage, which is characterized in that the liquid resin encapsulant is cured in that state after being wrapped around the semiconductor buff cage.

Hereinafter, the present invention will be explained in detail with reference to the drawings showing embodiments thereof.

FIGS. 1(a) to 1(d) show one embodiment of the method for manufacturing a semiconductor package according to the present invention in the order of steps. That is, as shown in FIG.
It is placed on top of the liquid resin sealing material 5 inside and left to integrate. By doing this, high-level skills are not required during integration, and the time required for the operator to check the flow of the liquid resin sealing material is also eliminated, increasing productivity. It is also possible to mechanize the work. If the resin sealing material is cured in that state without being turned upside down after being left as it is, a semiconductor puff cage with a good appearance can be obtained. This semiconductor package has the above-mentioned advantages (1) to (2). This example shows the fabrication of a plastic PGA. 7 is a bottle protruding from the back side of the semiconductor element mounting surface of the substrate 1.

Here, the reason why the board is placed on top of the resin encapsulant inside the metal case is to allow the board on which the semiconductor element is mounted to sink into the resin encapsulant due to its weight. . Since it is not forced to sink, air bubbles are less likely to form. If the resin is cured immediately after being placed, the viscosity of the resin will increase, leaving a portion that is not filled with the resin sealant, resulting in incomplete sealing.

By the way, if the fluidity of the resin sealing material inside the metal case is extremely poor, the substrate may not sink halfway, resulting in incomplete sealing. On the other hand, if the fluidity of the resin encapsulant is too good (that is, if the viscosity is too low), the resin encapsulant may flow out to the back surface of the substrate or overflow from the edge of the metal case. In order to prevent these inconveniences, it is preferable to select a resin sealing material with appropriate fluidity to be placed in the metal case. According to the inventors' study, the appropriate range of fluidity is very wide and varies slightly depending on the weight, material, thickness of the board on which the semiconductor element is mounted, and the taper state of the opening edge of the gold mud case, but it is within 20,000 yen. cP~
A viscosity of about 200,000 cP is appropriate. If it is below this range, the resin sealant may flow too much, and if it exceeds this range, the substrate may not sink sufficiently.

By placing the substrate on the resin sealing material and leaving it, the board sinks into the resin sealing material under its own weight including the semiconductor elements mounted thereon. Then, the resin sealing material 5 does not sink until it hits the bottom, that is, the metal case, and the resin sealing material 5 is released from the semiconductor element mounting surface side of the substrate 1 as shown in FIGS. 1(C) to FD). It goes around to the end face side, and the board 1 stops sinking at a certain distance from the metal case 8.

This stopping of subduction is thought to be due to the following reasons. When the substrate is placed on the resin encapsulant, the weight of the substrate and the mounted semiconductor elements is concentrated on a portion of the resin encapsulant, creating a pressure sufficient to cause the resin encapsulant to flow. In the state shown in FIG. 1(C) or (d), the weight is applied to the resin sealing material on average, so the pressure is not large enough to cause flow, and the pressure is not large enough to cause flow, and the end surface of the board and the case are Since the clearance is relatively small, a large resistance occurs when the resin sealant flows through this portion. Furthermore, even if the resin sealant rises from between the end face of the board and the edge of the case opening, its surface tension prevents it from flowing out to the back of the board or overflowing from the edge of the case opening.

If the resin sealant is heated and cured after being left as it is, there is a risk that the resin sealant may flow out to the back surface of the substrate or overflow from the edge of the case opening due to a decrease in viscosity due to heating or air currents during heating.

Such a problem can be avoided by impairing the fluidity of the resin sealing material, for example, by imparting thixotropy.

-i method of imparting thixotropy is to add ultrafine particles such as Aerosil (ultrafine silicic acid anhydride commercially available under the name "Aerosil"), or to add a swollen gel such as an organic bentonite compound. The method is to add a substance that has a chemical structure. However, since all of these methods involve an increase in viscosity, the fluidity when left in a room becomes extremely poor, which may prevent the substrate from sinking due to its own weight. This is because a method was used to impart thixotropy in the original sense, in which the viscosity when standing still is significantly higher than the viscosity when flowing and pressurized. Therefore, a fluidity control method that increases the so-called thixotropic index (relative value of viscosity dependence on rotational speed) is not preferred for this invention.

From this point of view, the inventors investigated the composition of a resin sealant that has fluidity when left at room temperature and has little flow when cured by heating. As a result, the resin encapsulant covers the filler by 4
It contains 0 to 70% by weight, and the average particle size of this filler is 1
If the particle size is 3 μm or less and the particle size distribution is 25% by weight or less of particles less than 4 μm and 25% by weight or more of particles of 15 to 30 μm, this resin encapsulant can be used as a liquid resin encapsulant used in the present invention. I found something favorable. 4 fillers
If it is less than 9% by weight, the coefficient of linear expansion of the cured product may be large and reliability may deteriorate, and the viscosity of the liquid resin sealant may be too low and may easily flow out of the metal case. If it exceeds 70% by weight, the viscosity becomes too high and the substrate may not sink into the substrate sufficiently, resulting in insufficient filling. Also,
If the average particle size of the filler is larger than 13 μm, the above fluidity control effect may not be obtained. If the particle size distribution is outside the above range, the fluidity control effect described above may not be obtained. In other words, the resin encapsulant used in this 'A' Ming contains an average particle size of 13 μm or less, a relatively wide particle size distribution up to about 30 μm, and very few -5 extremely fine particles. This is a preferable form of the filler.

Note that the preferable viscosity of the liquid resin sealing material varies depending on the weight of the substrate including the mounted semiconductor elements, the shape of the metal case, etc., and therefore the preferable range of the amount of the filler may also vary. According to the inventors' investigation, 89 pins, 1
．． For a 0 inch thick substrate, 45-5 sffxff1% was preferred.

The type of filler is not particularly limited, but fused silica is preferred. This is because fused silica has the advantages of a low coefficient of linear expansion and low impurity ions, and is suitable for use as a sealing material for semiconductor devices.

The resin encapsulant that covers the semiconductor element mounted on the substrate surface and the resin encapsulant placed in the metal case may be the same (or may be different. In any case, It is preferable to use a semiconductor encapsulation grade that has low impurity ions, low moisture absorption, and high reliability.Covering the semiconductor element with a resin encapsulation material in advance in this way is useful when the substrate is encapsulated with a liquid resin. Air bubbles remain around the element when it sinks into the material (
This is to ensure that The resin encapsulant that covers the semiconductor element in advance may be left unheated.
It may also be gelled. Moreover, the frame 13 for preventing flow may or may not be provided.

Cavity 1 in which a semiconductor element is placed on the substrate surface
It is not necessary to mount it on the bottom of 2, and it may be mounted on a flat substrate surface. In addition, as shown in FIG. 4(a), the semiconductor element 5 and the element 2 are placed in the recess 12 and the frame 13.
In order to prevent air bubbles from remaining inside the semiconductor elements 2, as shown in Fig. (It is preferable.

When the substrate is placed on the liquid resin sealing material in the metal case and left undisturbed, this is done, for example, at room temperature. This temperature is preferably between a temperature at which the liquid resin encapsulant does not freeze and a temperature at which curing of the liquid resin encapsulant does not progress in a short period of time, from -5°C to It is best to carry out at a temperature of about 40°C. There is no particular limit to the leaving time, but
It is preferable to select the viscosity of the resin sealing material in the metal case so that the standing time is about 3 minutes to 10 minutes.

The resin component of the resin sealant is preferably a system containing a compound having a plurality of epoxy groups, such as an epoxy resin, but is not limited thereto. In addition to the resin component and the filler, other components may be blended into the resin sealing material as necessary. The resin may be one-component, two-component, or any other type of sealing resin.The resin sealing material is not limited to one that is cured by heating, but may be one that is cured by other means.

The metal case used in the present invention may be made of any material, such as iron, aluminum, copper, etc., as long as it can maintain its shape and has appropriate strength. In particular, it is desirable to have no water vapor permeability at all. Moreover, from the viewpoint of rust prevention and insulation, it is preferable that the surface be subjected to insulation treatment such as oxidation treatment or painting.

The substrate used in this invention is also not particularly limited, for example,
A substrate obtained by impregnating a fibrous base material with a resin (resin composition) such as a glass epoxy substrate, a substrate made of a sheet of resin (resin composition), and other substrates are used.

The bonding between the electric path formed on the surface of the saw plate and the semiconductor element is not limited to wire bonding, but may be performed by other bonding methods. The electric path is made of copper, for example, but may be made of other conductors.

As shown in FIGS. 1(a) to 1d, it is preferable to attach a metal foil 6 to the back side of the semiconductor element mounting surface of the substrate 1, since moisture absorption through the substrate 1 can be reduced. Furthermore, if the resin sealing material covering the semiconductor element is gelled, the work will be easier.

Examples and comparative examples will be shown below, but the invention is not limited to the following examples.

(Examples 1 to 3) Figure 4 (al-Figure 4 (td-=C14'S L
The work was carried out in the order of FU ta) - -> Fig. 1 1) 1) - Fig. 1 (C1 to d).

88-bin semiconductor element mounting board (thickness 1.0 ***,
After covering the periphery of the element with a resin sealing material having the composition shown in Table 1,
It was heated at 0° C. for 30 minutes to form a gel. Put 1.1 g of liquid resin encapsulant having the composition shown in Table 1 into a metal lift, place the substrate from the semiconductor element mounting surface side onto the resin encapsulant in the metal lid, and leave it for 10 minutes at room temperature. Leave it for a minute.

The state was observed after being left at room temperature for 10 minutes, and the results were shown in Figure 1 (b).
) is "insufficient filling", the state between the state shown in Fig. 1 (C) and the state shown in Fig. 1 +d> is "good", and the state shown in Fig. 1 (C) is "good".
Those that reached the state shown in Figures (b) or (C) were judged to have "excessive flow", and the results are shown in Table 1.

The number of samples was 20 in each case. Room temperature is 25℃
Met.

After being left at room temperature, final curing was performed at 100°C for 1 hour and at 160°C for 3 hours. The state after curing was also judged in the same manner as above, and the results are shown in Table 1.

(Comparative Examples 1 to 5) The operations were carried out in the order of Fig. 4(a) - Fig. 4(b) - Fig. 4(C).

8-day bottle semiconductor element mounting board (rg, mi L Q 1m
, 31mm x 31mm, glass epoxy substrate),
The peripheral area of the device was covered with a resin sealing material having the composition shown in Table 1, and then heated at 100° C. for 30 minutes to form a gel. Gold i! l
i! Put 1.1 g of a liquid resin encapsulant having the composition shown in Table 1 into the J-lift, place the substrate on the resin encapsulant in the metal lid from the semiconductor element mounting surface side, and place the substrate on the resin encapsulant in the metal lid. C)
As shown in Table 1, the pressure shown in Table 1 was applied from the back of the substrate to push the substrate into the resin sealant. The pressing pressure and time at this time were as shown in Table 1.

After this pressing, final curing was performed in the same manner as in Example 1.

Each state after indentation and after final curing was observed and evaluated in the same manner as in Example 1, and the results are shown in Table 1.

Table 1 also shows the viscosity at room temperature of each resin sealing material used in Examples and Comparative Examples.

The compounds used in the Examples and Comparative Examples were as follows.

Epoxy resin: Bisphenol A epoxy resin (YD-8125) manufactured by Tobu Kasei ■ Hardening agent A: Methylhexahydrophthalic anhydride (B-650) manufactured by Dainippon Ink Chemical Industry @ Hardening agent B...・Compound represented by the following formula of Dainippon Ink Chemical Industry @ Crack (B-
4400) Accelerator: diazabicycloundecene (D B U) octylate (SA102) manufactured by Sun-Abro Camping agent: γ-glycidoxypropyltrimethoxysilane (A manufactured by Nippon Unicar) -187) Pigment: Carbon black (M
A 100) Filler C: Fused silica manufactured by Denki Kagaku Kogyo H (FS-
74) Filler D: Fused silica for Taramori formal wear (AS-1) Note that the particle size distribution and average particle diameter of fillers C and D are as follows.
It was as shown in the table. Measurement of particle size distribution of fillers is
This was carried out using a Microtrac particle size analyzer manufactured by Nikkiso@.

Table 2 As shown in Table 1, in each comparative example, the working time per piece was longer than in the example, and good products could not be obtained unless the pushing pressure and time were delicately adjusted. On the other hand, in each of the examples, the working time per piece was short and the pressing work was not required, so the work was easy.However, in the comparative example, the appearance was different after pressing and after curing. This is because the pushing pressure remained.

〔Effect of the invention〕

As described above, the method for manufacturing a semiconductor pancage according to the present invention is such that a substrate, on which a semiconductor element mounted on the surface is covered in advance with a resin sealing material, is opened from the semiconductor element mounting surface side with the opening facing upward. The liquid resin encapsulant is placed on top of the liquid resin encapsulant placed in the metal case of the substrate, and the liquid resin encapsulant is passed from the semiconductor element mounting surface side of the substrate to the end surface side. Since the liquid resin encapsulant is cured in this state, it is possible to obtain a semiconductor package with a good appearance without performing a pushing operation to submerge the semiconductor element mounting board into the resin encapsulant. This eliminates the need to delicately adjust the amount of pressure and the time to apply it.
Workability is greatly improved, and work efficiency (productivity) is greatly improved.

[Brief explanation of the drawing]

1(a) to dl are schematic sectional views showing one embodiment of the semiconductor package manufacturing method according to the present invention in the order of steps, FIG. 2(a) is a perspective view of a semiconductor element mounting board, and FIG. bl is its cross-sectional view, and Figure 3 is 1 of the plastic PGA.
FIG. 4 (al to d) is a schematic sectional view showing an example of a conventional manufacturing method in the order of steps, and FIG. 5 (a) to C) are plastic PGAs with poor appearance.
FIG. 1...Substrate 2...Semiconductor element 5...Resin sealing material 8...Metal case Representative Patent attorney Takehiko Matsumoto Figure 3

Claims (2)

[Claims] (1) A substrate with a semiconductor element mounted on its surface is covered with a metal case from the semiconductor element mounting surface side with a desired distance from the case, and the space is filled with a resin sealing material. In order to obtain a semiconductor package in which the semiconductor element is sealed, a substrate on which the semiconductor element mounted on the surface is previously covered with a resin sealing material is prepared from the semiconductor element mounting surface side with the opening facing upward. After placing the liquid resin encapsulant on top of the liquid resin encapsulant placed in a metal case containing the substrate, the liquid resin encapsulant is passed from the semiconductor element mounting surface side of the substrate to the end surface side. A method for manufacturing a semiconductor package, comprising curing the liquid resin encapsulant in that state. (2) The resin sealing material placed inside the metal case covers the filling material 4
The filler contains 0 to 70% by weight and has an average particle size of 1
2. The method of manufacturing a semiconductor package according to claim 1, wherein the amount of particles is 3 μm or less and the particle size distribution is 25 m% or less of particles with a particle size distribution of less than 4 μm, and 25% by weight or more of particles with a particle size of 15 to 30 μm.