JP2823661B2 - Low temperature sealing method for semiconductor package - Google Patents

Description

The present invention relates to a low-temperature sealing method for a semiconductor package.

(Prior Art) Conventionally, semiconductor packages are shown in FIGS. 1 (a) and 1 (b).
The lead shown in Fig. 1 has a structure in which the lead is sandwiched by a glass-based sealing material, and sealing is completed at this part. There is a type 2 that seals at a part. The structure of type 1 is to apply a glass sealing material to the base and cap of the package, calcinate, fix the leads to the base, bond the semiconductor, perform wire bonding, put the cap on It is put into a furnace and sealed at a temperature at which the glass-based sealing material flows sufficiently. As a type 1 glass-based sealing material, a glass composition for sealing as disclosed in JP-A-55-5554 and JP-A-57-102874 is used. These glass-based sealing materials are added with a considerable amount of ceramic powder to satisfy large sealing strength, high insulation, low dielectric constant, chemical durability and safety, and the fluidity of glass is impaired. In order to obtain the necessary fluidity for sealing, the sealing temperature must be high (410-430 ° C.). In order to reduce the sealing temperature of these glass-based sealing materials, glass to which a monovalent metal oxide such as halogen or alkali metal is added has been studied. However, glass-based sealing containing glass to which these components are added is included. The material cannot meet the above-mentioned required properties and cannot be used. When pressure is applied to the structure of the type 1, the lead portion is deformed, which causes a problem such as cutting of a bonding wire. Due to the above restrictions, there was a problem that the sealing temperature could not be lowered in the type 1 structure. In the type 2 structure, the leads were fixed with another glass-based sealing material or material. The low dielectric constant and, in some cases, the chemical durability are not so important, and a sealing material containing low-temperature glass containing fluorine is generally used. Although it is possible to seal at lower temperature (about 400 ° C) than Type 1, it is only used for special purpose semiconductors because of the complicated structure and process and high cost compared to Type 1. Absent.

(Problems to be Solved by the Invention) In recent years, the degree of integration of semiconductors has been dramatically increased, and with the miniaturization of circuits, circuit components in semiconductors are prevented from being diffused due to the sealing temperature during sealing. Therefore, low temperature (380-400
C). Further, for more general use, a lower cost package structure and a sealing method are desired.

(Means for Solving the Problems) The present invention solves the above-mentioned problems and responds to the recent demand for improvement in the degree of integration of semiconductors, and uses a fixing sealing material for a base for joining semiconductor chips. A method of sealing a package in which a lead is fixed, a second sealing material is fixed to a cap, and the base and the cap are brought into contact with each other and heated and sealed, wherein the fixing sealing material is a crystallized glass type sealing. A sealing material having a bonding material or softening point higher than the sealing temperature of the second sealing material, and applying heat to the sealing portion while applying pressure to the sealing portion when sealing the base and the cap; A low-temperature sealing method is provided.

The sealing method of the present invention is basically applied to a type 1 package having the structure shown in FIG. 1 (a) or (b).

First, a glass-based fixing material for fixing the lead (2) is applied to the base (1) of the type 1 package 1, and the second glass-type sealing material used for sealing is applied to the cap (3). Apply and calcine and bake at a temperature above the glass transition point. Thereafter, the temperature of the lead fixing glass-based sealing material on the base side is increased, and the lead is fixed at a temperature at which the lead is fixed. Next, the semiconductor chip is bonded to the package, and after a wire bonding process with the lead, the cap coated with the glass sealing material to be sealed is brought into contact with the base, and pressure is applied to the sealing portion to soften the glass. Heat at a temperature above the point.

The present invention, in the above process, using a glass-based sealing material for fixing the lead, using a glass-based sealing material for sealing in the sealing step and to fix the lead before sealing, The present invention relates to a method of performing pressure bonding, and does not limit a step before or after these processes or a step between these processes.

The temperature at which the glass-based sealing material is calcined must be between the glass softening point and slightly higher than the sealing temperature (up to 20-30 ° C) in order to increase the bonding strength between the glass-based sealing material and the package. No. As the fixing sealing material and the second sealing material, usually, a single glass or a mixture of a glass powder and a ceramic powder is used, and in particular, a lead-based glass is widely used as the glass. Although the composition and properties of these glass or the sealing composition are not limited, the fixing sealing material for fixing the lead is not preferable when the glass component is softened at the time of sealing and the lead is remarkably moved. Use a glass component that is almost the same as or higher than the sealing temperature, or use a glass-based sealing material that crystallizes at the time of fixing the lead or after fixing and is hard to soften and flow at the time of sealing (crystallized glass sealing material). ).

The composition and characteristics of the second sealing material are not limited as long as the sealing material can be used for sealing a package having a type 1 structure.

Other package materials and lead materials are not particularly limited as long as they can be used for the package having the type 1 structure.

Pressure during sealing is essentially required at least while the second sealing material flows sufficiently at the given pressure and temperature.

Specifically, the pressure is preferably in the range of ^{20 to} 3000 g / cm ² . If the pressure is less than 20 g / cm ² , the adhesive strength is undesirably reduced, and if it is more than 3000 g / cm ² , the glass protrudes, which is not preferred.

The pressurizing time is preferably 1 to 20 minutes. If the pressing time is less than 1 minute, the adhesive strength is reduced, and if the pressing time is more than 20 minutes, the productivity is undesirably reduced.

In the present invention, the use of the glass-based sealing material for fixing the lead is such that the glass is softened and flows in the subsequent pressure bonding step.
This is to prevent the lead from moving. Also, the present inventor:
The bonding strength between the fixing glass-based sealing material and the second glass-based sealing material is large, and the bonding shape between them is more reliable than the bonding between the glass-based sealing material and the package material, and is broken by pressure concentration. Was found to be a shape that is unlikely to occur.
Further, the temperature suitable for sealing of no pressurization is in the vicinity pour point of the glass (glass viscosity at 10 ⁵ poise), it can be lowered and pressurized to around the softening point (glass viscosity at 10 ^7.6 poise) As a result, they have found that highly reliable sealing can be achieved even with pressure sealing near the softening point.

 Next, examples of the present invention will be described.

16 pin LS consisting of alumina package and 42Ni lead, usually called sardip
I package is used, and the fixing sealing material is crystallized glass (PbO 80wt%, B ₂ O
_{3 10wt%, ZnO 8wt%,} SiO 2 1wt%, as Al ₂ O ₃ in a glass consisting of 1 wt% those containing cordierite 20 wt%) using, and a second likewise cerdip sealing material generally those used _{(PbO 80wt%, B 2 O} 3 10wt%,
_{ZnO 3wt%, SiO 2 1wt%} , Al 2 O 3 1wt%, Bi 2 O 3 5wt% glass cordierite 10 wt% consisting of tin compounds 15 wt%
Containing). Table 1 shows the properties of these glasses.
Shown in

Each of the glass powders was mixed with a vehicle comprising an organic binder and an organic solvent, and then paste-formed, followed by screen printing to apply a fixing sealing material to a package base and a cap to apply a second sealing material. The coating thickness at this time is about
0.4 mm. The package after application was treated at 400 ° C. for 10 minutes to remove the organic binder and baked on the package. A lead was mounted on a fixing sealing material of a base on a heater block at 510 ° C., and crystallization was performed at 490 ° C. Next, the base and the cap were combined, a pressure weight was placed thereon, and heat sealing was performed at a predetermined temperature for 10 minutes.

For comparison, a base and a cap each having a second sealing material and a base and a cap each having a fixing sealing material were prepared. The steps up to the lead attachment are the same as those described above, except that the sealing is unloaded, and the second sealing material (glass type) is 410 ° C. and the fixing sealing material (glass type) is 490 ° C. In each
Treated for 10 minutes.

Due to the sealing process, no extreme deformation or movement of the lead was observed. The appearance of the sealing part by crimping is 340
° C., until weight 1500 g / cm ² is not much different from no weighting, the weighted 1500 g / cm ² in good appearance is not obtained at 330 ° C..

In order to examine the package performance, the above samples were subjected to a shear strength test by shearing and a US Army standard (MI
L) Temperature cycle test based on -883C 1010.6 (-65
100 ° C. liquid to 150 ° C. liquid) for 100 cycles. Table 2 shows the results. The shear strength is the average strength of 20 samples. In the temperature cycle test, after the cycle was performed, package leaks due to cracks and the like were examined by a He leak test, and 10 ^-8 cc / sec or more was determined to be out, and the number of outs / the number tested was shown in the table.

In the same table, those which are not pressurized are also shown as comparative examples.

When the sealing temperature is lowered, the weight needs to be increased. The sealing temperature is close to the strength when only the second sealing material is used, and is higher than the strength when only the fixing sealing material is used. The reason is considered that the expansion of the fixing sealing material is lower than that of the second sealing material, and the fixing sealing material alone is weak. However, after the pressure sealing, a compressive stress is applied to the fixing sealing material. Can be The sealing strength hardly decreases until 360 ° C, and slightly decreases at 350 ° C. Although it decreases considerably near the softening point of the second sealing material, it is not a value that cannot be used for sealing the package yet, and the cycle test has few defects.

As shown in the examples, by using a glass-based sealing material for fixing the lead and a second glass-based sealing material, and sealing by pressing, the sealing temperature is significantly lower than in the case of no pressure, Sealing is possible even at temperatures near the softening point. Further, this method can be applied to a conventionally used glass-based sealing material for a package, and does not require a change in the package structure.

(Effects of the Invention) According to the present invention, a more reliable package can be sealed at a lower temperature than before.

[Brief description of the drawings]

 FIG. 1 is a perspective view of a package. 1 Base 2 Lead 3 Cap

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-60-182749 (JP, A) JP-A-63-110754 (JP, A) JP-A-1-231355 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) H01L 23/02 H01L 23/10

Claims (1)

(57) [Claims] A lead is fixed to a base to which a semiconductor chip is bonded by using a fixing sealing material, and a second is fixed to a cap.
A method of sealing a package in which a sealing material is fixed, and a base and a cap are brought into contact with each other to heat and seal the package, wherein the fixing sealing material is a crystallized glass-based sealing material or the softening point is the second sealing material. A low-temperature sealing method for a semiconductor package in which a sealing material is higher than a sealing temperature of a sealing material and is heated and sealed while applying pressure to a sealing portion when sealing a base and a cap.