Special receptacle or package – With moisture absorbent
Reexamination Certificate
2001-04-30
2002-09-03
Fidei, David T. (Department: 3728)
Special receptacle or package
With moisture absorbent
C206S720000
Reexamination Certificate
active
06443298
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a technique for preventing peel of a package interface and crack when a surface package type semiconductor package is mounted to a packaging substrate such as a printed circuit board.
In surface mount package type semiconductor packages such as a small outline package (SOP), a squad flat package (QFP), a plastic leaded chip carrier (PLCC), and the like, the size and thickness of the packages are more and more reduced in order to cope with the increase in the size of a semiconductor chip stored in the package and package strength tends to decrease.
Therefore, it has become difficult to produce a thin resin molded IC having high reliability.
Incidentally, mention can be made of “IC PACKAGING TECHNIQUE”, published by Kogyo Chosakai K. K., Jan. 15, 1980, pp. 135-156, as a prior art reference describing surface package type semiconductor packages.
Furthermore, as disclosed in Japanese Patent Laid-Open No. 178877/1986 by Otsuka et al. (Aug. 11, 1986), a proposal has been made to put a desiccant into a magazine or to seal a conveying tray in a bag of a vinyl sheet or the like.
SUMMARY OF THE INVENTION
When examining packaging reliability and strength of these thin type packages, the inventors of the present invention have found out that when heat is applied to the package when surface-mounting the package to a mounting substrate such as a printed circuit board such as at the time of solder reflow, a moisture that has entered the package causes drastic volume expansion and peel of the package interface and crack develops.
To cope with this problem, it has been customary to bake the package at 125° C., for example, for a period as long as 16 to 24 hours before solder reflow, but this method is believed inefficient because a furnace for baking must be prepared and particularly because baking must be made for the long period.
As a result of examination of the origin of the moisture causing the cracking described above, the inventors of the invention have clarified that the moisture in the air enters the package during the period from transfer molding of a chip component by a resin to solder reflow and is likely caused to dew.
Though the Otsuka et al. method described already provides a considerable effect, the problem cannot be solved completely by this method in view of the recent product situation where the thickness and size of the packages are reduced more and more to store greater chips and of the severe environment where the products are shipped by airplanes.
It is therefore an object of the present invention to provide a technique which prevents interface peeling and cracking of a surface mount package type package.
It is another object of the present invention to provide a highly reliable high density packaging technique.
It is still another object of the present invention to provide an efficient solder reflow technique.
It is still another object of the present invention to provide an effective shipment method of electronic components.
It is a further object of the present invention to provide an effective preservation method of semiconductor devices sealed by a thin resin package.
It is still another object of the present invention to provide high freedom for the conditions of executing an assembly process.
It is still another object of the present invention to provide an assembly process which will be suitable for surface mount package.
It is still another object of the present invention to provide an efficient surface mount type packaging technique.
It is still another object of the present invention to improve moisture-proofness of resin-molded ICs, or the like.
It is still another object of the present invention to provide a packaging technique of resin-molded ICs or the like which will be suitable for automatic packaging.
It is still another object of the present invention to provide a preservation method of ICs, components, electronic devices, and the like, which have high moisture-proofness and do not require baking even when stored for a long period.
It is still another object of the present invention to provide a packaging method of electronic components such as ICs which can easily discriminate the existence of pin-holes.
It is still another object of the present invention to provide a moisture-proofing package technique of ICs or the like which does not need a large space requirement.
It is still another object of the present invention to provide a moisture-proofing packaging technique of ICs or the like which can easily judge the degree of hygroscopicity of ICs or the like.
It is still another object of-the present invention to provide a moisture-proofing bag having a display portion for displaying the degree of hygroscopicity of ICs or the like.
It is still another object of the present invention to provide a package member for surface package type packages which can easily represent the degree of hygroscopicity of ICs or the like.
It is still another object of the present invention to provide an efficient surface mounting method of resin-molded ICs or the like.
It is still another object of the present invention to provide an assembly process which will be suitable for resin-molded electronic components storing therein integrated circuits having a large chip size.
It is still another object of the present invention to provide a shipment method of electronic devices such as resin-molded ICs which will-be suitable for the shipment of the electronic devices by air planes.
It is still another object of the present invention to provide a moisture-proofing packaging technique of resin-molded ICs or the like which does not undergo dewing even at low temperatures.
It is still another object of the present invention to provide a technique which can confirm the state of hygroscopicity of a moisture-proofing package inside the package from the outside thereof.
These and other objects and novel features of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.
Among the inventions disclosed herein, a typical example is as follows.
In the present invention, a surface mount package type package stored in a magazine is put into an interior box, the interior box is then placed into a transparent resin bag using, as the base, a polyester having moisture permeability of up to 2.0/m
2
·24 hrs, for example, and having a surface intrinsic resistance of 10
6
Ohms on the outside and up to 10
11
Ohms on the inner side, and the open portion of the bag is heat-sealed after removing the air. Furthermore, a desiccant such as silica gel is put into the interior box.
According to this arrangement described above, the surface mount package type package is stored in the interior box and the moisture-proofing bag outside the box and sealed completely by deaeration and heat seal and is free from the influences of external moisture. Therefore, the interface peel and crack of the package do not occur even after solder reflow without the need of the troublesome baking operation. Particularly because the polyester having moisture permeability of up to 2.0 g/m
2
·24 hours is used as the base of the resin bag in the present invention, moisture-proofness is high and heat seal is possible so that the effect of checking intrusion of the external air is high. The surface intrinsic resistance of the bag is up to 10
11
ohms on its inner surface and up to 10
6
ohms on its outer surface in order to prevent any charge. Furthermore, silica gel is placed between the magazine and the wall surface of the interior box in the present invention in order to absorb the moisture so that the surface package type package is not much affected by the external moisture.
Still another example of the inventions disclosed herein is as follows.
Namely, the present invention provides a transparent moisture-proofing packaging bag for moisture-proofing and packaging an electronic component, which bag is equipped with a moisture indicator for detecting the degree of hygroscopicity inside
Kitamura Wahei
Murakami Gen
Nishi Kunihiko
Antonelli Terry Stout & Kraus LLP
Fidei David T.
Hitachi , Ltd.
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