Electricity: conductors and insulators – Boxes and housings – Hermetic sealed envelope type
Reexamination Certificate
2003-02-14
2003-11-04
Ngo, Hung V. (Department: 2831)
Electricity: conductors and insulators
Boxes and housings
Hermetic sealed envelope type
C174S050510
Reexamination Certificate
active
06642449
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an electronic component having an electrode conductor formed of a photosensitive conductive paste and a non-photosensitive conductive paste, which are formed on an element, and a method for manufacturing the electronic component, and more particularly to an electronic component comprising an electrode conductor that is suitable for a chip inductor, an LC filter, a dielectric filter, and a non-reciprocal circuit element (circulator, isolator), and a manufacturing method for manufacturing this electronic component.
A conductive pattern for an electronic component is required to be fine and highly reliable. For example, recently, the portable telephones have advanced for higher frequency, and a number of leadless parts that have excellent frequency characteristics have been employed. In particular, for the electrode portions, it is demanded that the fine patterns as precise as in units of micron are produced stably at high yield. At the same time, the strength to withstand severe environments including high temperatures, vibrations, and humidity is required with high reliability.
Regarding the pattern precision, in the package for a chip inductor, a ceramic substrate, a ceramic multi-layer substrate or a semiconductor, for example, it is already required that the pattern precision, the pitch size or the line-and-space of an electrode conductor may be as small as 30 &mgr;m to 50 &mgr;m or below, because the current requirements for smaller size and higher frequency can not be met with the sizes of 100 &mgr;m to 150 &mgr;m as conventionally employed.
The mounting pattern or the electrode of mounted portion is demanded to be stronger and more highly reliable, because of the miniaturization. Further, the recent lead free trend causes the soldering temperatures to be raised, and there is a requirement for the heat-resisting electrode to withstand the high temperatures.
To form an electrode or a conductor pattern on the surface, a thick film printing method using the conductive paste is generally used, because the vacuum deposition involves a smaller film thickness of conductor, and the lower productivity. Employing a screen and a squeeze, a silver paste is printed on a ceramic element to form a conductor pattern. Thereafter, a drying process is undergone, and the conductor pattern is sintered at a temperature from about 450° C. to 1000° C., whereby an electrode conductor is formed.
With the above screen printing method, there are a variety of dimensional dispersion factors to form the fine conductive patterns at high precision and stably, including (1) positional precision of screen, (2) positional precision of jig, (3) exudation of paste, (4) blurred printing, (5) degradation of screen, and (6) degradation of squeeze. Due to such an influence, the ultimate electrical characteristic (e.g., the inductance for a chip inductor, or the filter characteristic for a dielectric filter) may be affected. Consequently, it was obliged to make the trimming using a router which took a lot of steps with the filter to obtain good products.
In particular, in the case where there are irregularities or through holes such as an electrode on the end face of a chip element or a dielectric filter, it is not possible to solve the problems only by the screen printing of conductive paste. As a specific example, a dielectric filter having a fine conductor pattern formed on one side of the through hole in the dielectric block will be described below.
In the case where the pattern printing is made on the dielectric block of the dielectric filter as above constituted, a plurality of dielectric blocks are arranged on a jig at a time in consideration of the productivity, and then the screen printing is made using the conductive paste.
FIGS. 17A
to
17
E show a pattern printing process with the conventional screen printing.
FIG. 17A
shows a step of arranging the dielectric blocks
1
on a printing jig
2
. The dielectric blocks
1
are arranged on the jig
2
having a plurality of cavities
3
.
FIG. 17B
shows a cross section of the jig
2
, in which the dielectric blocks
1
provided in the cavities
3
are arranged at a fixed spacing.
FIG. 17C
shows a step of printing a conductive paste
4
, in which the conductive paste
4
is printed in a pattern
8
by a squeeze
6
, using a printing screen
5
with a predetermined pattern.
However, the screen
5
has originally no distortion as shown in
FIG. 17D
, but the screen
5
may be distorted as shown in
FIG. 17E
by repeating this operation. The reason is that in the case where the dielectric blocks
1
are arranged on the jig
2
as shown in
FIG. 17C
, it is necessary to withstand a printing pressure only with the printing screen
5
at a portion of the spacing &Dgr;W on either side of the jig
2
. Consequently, the printing screen
5
is loaded, and stretched, so that the positional precision is significantly worse.
On the contrary, since the screen printing is limited in respect of fineness, it has been examined in recent years that an electrode conductor of a predetermined pattern is produced through an exposure and development process (photo lithography process) using a photosensitive conductive paste (conductive paste having photo sensitivity).
In a production method employing such photosensitive conductive paste, the fine conductor pattern can be produced, but the following problems remain.
(1) Particularly, the screen printing has a drawback that a mesh mark produces a pinhole defect. Regarding this point, means for enhancing the flowability of photosensitive conductive paste was proposed in JP-A-10-112216.
(2) If a thick film is formed at a time, it takes not only considerable time to make exposure, but also the pattern precision is degraded. Therefore, it may be difficult to obtain a film thickness required for the electrode conductor of electronic component at a time. For example, in the case of an electrode conductor in the soldered portion, if the conductor is Ag, the amount (thickness) of conductor melting into the eutectic solder is 2.5 &mgr;m at 250° C., and 5 &mgr;m at 280° C. On the other hand, the photosensitive conductive paste is applied normally in a thickness of 10 to 20 &mgr;m to make the treatment at high precision and an exposure time to increase the productivity. In this case, after sintering, the conductive paste has a thickness of about 5 to 10 &mgr;m. Accordingly, with an Ag thickness of 5 &mgr;m, the conductor Ag is exhausted at 280° C. in one second.
(3) It is difficult to make exposure for the portion perpendicular to the light, particularly, the though hole with a large aspect ratio. It is difficult to form the through hole.
(4) The photosensitive conductive paste is often inferior to the non-sensitive conductive paste (conductive paste having no photosensitivity) available at present in the respects of conductivity or film thickness. Hence, it is difficult to obtain the photosensitive conductive paste having conductivity and film thickness comparable to those of the non-photosensitive conductive paste, or cheaper in the costs.
In this way, in the case where the electrode conductor is formed using the photosensitive conductive paste, there are a number of items that have not been solved yet.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an electronic component capable of not only enhancing the pattern printing precision which was the conventional problem, but also forming a pattern and an electrode in a predetermined film thickness suitable for the location where the electronic component is employed, and further forming the electrode in the portion with a high aspect ratio, and a method for manufacturing the electronic component.
Other objects and new features of the present invention will be more apparent when reading the following embodiments.
According to first aspect of the present invention, there is provided an electronic component comprising: a first electrode conductor section formed of the non-photosensitive conductive paste on
Gotoh Masashi
Tashiro Kouji
Ngo Hung V.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
TDK Corporation
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