Metal working – Barrier layer or semiconductor device making – Barrier layer device making
Reexamination Certificate
2000-11-15
2002-07-23
Nguyen, Ha Tran (Department: 2812)
Metal working
Barrier layer or semiconductor device making
Barrier layer device making
C029S025010, C029S025020, C361S535000, C264S272150, C264S272180
Reexamination Certificate
active
06423104
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a tantalum solid electrolytic capacitor and, in particular but not exclusively, to a method of and an apparatus for manufacturing tantalum solid electrolytic chip capacitors for use in various electronic appliances.
2. Description of the Related Art
Recently, with a tendency to reduce the weight and size, with a tendency to enhance the performance, and with the development of a packaging technique, the number of electronic appliances that are formed into chips is rapidly increasing. Also, in the field of solid electrolytic capacitors, with a tendency to reduce the size and increase the capacity, the number of the solid electrolytic capacitors that are formed into chips is increasing. However, a further reduction in size and a further increase in capacity are demanded.
FIG. 9
depicts a conventional tantalum solid electrolytic chip capacitor, while
FIGS. 10A and 10B
depict an essential portion of a tantalum solid electrolytic capacitor made by a conventional manufacturing method after assemblage.
In these figures, reference numeral
20
denotes a capacitor element, which is a sintered porous body formed of powder of tantalum metal, one of valve action metals. An anode lead
21
made of a tantalum wire is partially embedded in and extends outwardly from the porous body. A dielectric oxide layer
22
is formed on a portion of the anode lead
21
and over the entire surface of the porous body by anodizing. An electrolyte layer
23
such as manganese dioxide or the like is formed on the surface of the dielectric oxide layer
22
, and a cathode layer
24
is further formed on the electrolyte layer
23
. The cathode layer
24
includes a carbon layer and a silver paste layer laminated one upon another by dipping. Reference numeral
25
denotes a Teflon-made insulating plate mounted on the anode lead
21
to prevent an electrolyte from reaching and adhering to the anode lead
21
during formation of the electrolyte layer
23
. Reference numeral
26
denotes an anode terminal, which is connected to the anode lead
21
by welding and is bent after formation of a sheathing resin
28
(explained later). Reference numeral
27
denotes a cathode terminal electrically connected to the cathode layer
24
of the capacitor element
20
via a thermosetting conductive adhesive
29
made of epoxy resin, which is cured by a hot-air circulating dryer. The cathode terminal
27
is bent after the molding of the sheathing resin
28
. The sheathing resin
28
is covered over the entire capacitor element
20
by molding.
In the conventional tantalum solid electrolytic capacitor of the above-described construction, the conductive adhesive
29
used to connect the cathode terminal
27
to the cathode layer
24
of the capacitor element
20
is cured by the hot-air circulating dryer during batch processing, wherein the conductive adhesive
29
is allowed by stand for 90 minutes in an atmosphere of 180±5° C. Accordingly, as much time as about 6 hours is required from the start of assembling to the end of curing the adhesive, including the time required for increasing the temperature of a product from when the product is introduced into the hot-air circulating dryer to when it reaches 180±5° C., the A curing time of 90 minutes, and the annealing or slow cooling time up to when the product is taken out at room temperature. According to this manufacturing method, the conductive adhesive
29
is first discharged on the cathode terminal
27
, and the capacitor element
20
is then placed on the conductive adhesive
29
. Thereafter, the capacitor element
20
is temporarily fixed by connecting the anode lead
21
to the anode terminal
26
, and the curing is carried out using the hot-air circulating dryer. Thus, the capacitor element
20
is merely placed on the conductive adhesive
29
, which in turn comes to have a thickness of about 100 &mgr;m to about 500 &mgr;m, resulting in an increase in apparent resistant of the conductive adhesive itself.
Furthermore, as shown in
FIG. 10B
, it is likely that air is drawn into an interface between the capacitor element
20
and the conductive adhesive
29
to create air bubble portions
30
. The presence of the air bubble portions
30
increase the connection resistance, deteriorating the electric characteristics (tan &dgr;/1 KHz or ESR/100 KHz) required for capacitor.
SUMMARY OF THE INVENTION
The present invention has been developed to overcome the above-described disadvantages.
It is accordingly an objective of the present invention to provide a method of and an apparatus for stably manufacturing tantalum solid electrolytic capacitors that are superior in electric characteristics (tan &dgr;/1 KHz or ESR/100 KHZ).
Another objective of the present invention is to provide the method and apparatus of the above-described type that are superior in productivity.
In accomplishing the above and other objectives, the method according to the present invention comprises: preparing a length of metallic lead frame having a plurality of anode terminals and a plurality of cathode terminals; coating the plurality of cathode terminals with a thermosetting conductive adhesive; placing cathode layers of a plurality of capacitor elements on the conductive adhesive; placing anode leads extending outwardly from the plurality of capacitor elements on the plurality of anode terminals, respectively; joining the anode leads to the plurality of anode terminals, respectively, by welding; applying a pressure to the plurality of capacitor elements so that a portion of the conductive adhesive is squeezed out of one surface of each of the plurality of capacitor elements to a neighboring side surface thereof; joining the plurality of cathode terminals to the plurality of capacitor elements, respectively, by heat-curing the conductive adhesive; and covering the plurality of capacitor elements with a sheathing resin.
According to the above-described method, the pressure applied to the capacitor elements moves a portion of the conductive adhesive to the neighboring side surface of each capacitor element, thereby causing the conductive adhesive layer to have a reduced thickness. As a result, the resistance of the conductive adhesive in the thickness direction reduces considerably, and the adhesion properties between the surface of the cathode layer of the capacitor element and the surface of the cathode terminal are improved. Unlike the conventional method, air bubbles are not produced and, hence, the electric characteristics (tan &dgr;/1 KHz or ESR/100 KHz) are improved. Moreover, the use of an adhesive that cures within a short time enables successive curing within the manufacturing apparatus, compared with the conventional batch processing by the use of a hot-air circulating dryer, thus enhancing the productivity.
Preferably, the pressure applied to the plurality of capacitor elements ranges from 2 kg/cm
2
to 9.5 kg/cm
2
in terms of leakage current.
Advantageously, an epoxy-based adhesive is used for the conductive adhesive, and the conductive adhesive has a thickness smaller than 100 &mgr;m after the application of the pressure. The use of the epoxy-based adhesive enables curing within a very short time and enhances the productivity, and the reduced thickness of the conductive adhesive reduces the resistance of the conductive adhesive.
On the other hand, the apparatus according to the present invention includes a lower mold having an upper surface, on which a length of metallic lead frame having a plurality of anode terminals and a plurality of cathode terminals is to be placed, an upper mold mounted on the lower mold having a lower surface spaced from the upper surface of the lower mold, and a heater mounted in the lower mold. The plurality of anode terminals are joined to respective anode leads extending outwardly from a plurality of capacitor elements, and the plurality of cathode terminals are coated with a thermosetting conductive adhesive, on which cathode layers of the plurality of
Kawakita Nario
Masuda Yoji
Ogino Masakuni
Omori Minoru
Tomita Osamu
Matsushita Electric - Industrial Co., Ltd.
Nguyen Ha Tran
Wenderoth , Lind & Ponack, L.L.P.
LandOfFree
Method of and apparatus for manufacturing tantalum solid... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of and apparatus for manufacturing tantalum solid..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of and apparatus for manufacturing tantalum solid... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2873066