Method for manufacturing chip-like electronic parts

Electronic parts are stuck into holes provided in an elongated retainer sheet and thereby retained. The retainer sheet as a transfer medium for the electronic parts is made to pass through a plating bath, a cleaning and drying section, an electrical characteristic measuring section, and a takeout section in turn. This allows the electronic parts 1 to be subjected to a plating process on their external electrodes, an electrical characteristic measuring process, and a taping process in a continuous manner. As a result, reduction in the number of handling manhours in the individual processes as well as space saving can be realized, while productivity can be improved.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a method for manufacturing chip-like 
electronic parts and, more particularly, to such a method in which a 
plating process on external electrodes and various processes required to 
succeed can be continuously carried out. 
2. Description of the Prior Art 
FIGS. 5(A) and 5(B) show a monolithic capacitor as an example of a 
chip-like electronic part 1. The monolithic capacitor has a structure in 
which external electrodes 4, 4 are provided at both ends of a ceramic 
device 3 having a plurality of internal electrodes 2 in such a way that 
the external electrodes 4, 4 conduct with the internal electrodes 2. 
The external electrodes 4, 4 each comprise an inside electrode 5 provided 
by printing or applying a paste such as Ag--Pd, Ag, or Cu to an end of the 
ceramic device 3 and plating the paste, and a plated layer 6 provided on 
the surface of the inside electrode with Ni, Sn, solder, or the like for 
preventing the electrodes from aggression during soldering onto the 
printed circuit board and for improvement in solderability. 
In manufacturing the monolithic capacitor, formation of the inside 
electrode 5 at the end of the ceramic device 3 is followed by a plating 
process on the inside electrode 5, a plate drying process, a measurement 
process for measuring electrical characteristics such as electrostatic 
capacity and insulation resistance, and a taping process, in this order. 
The plating process has conventionally been implemented by using a barrel 
bath 7, as shown in FIG. 6, into which chip-like monolithic devices and 
steel balls are accommodated in a certain quantity. The barrel bath 7 is 
rotated in a plating bath, whereby a plating layer is deposited on the 
surface of the inside electrode. 
The electrical characteristic measuring process has been carried out 
hitherto in the following manner. A rotary table 8 as shown in FIG. 7(A) 
is provided with a round hole 9 slightly larger than the diagonal size of 
the device 3 at regular intervals. The electronic part 1 is inserted into 
this round hole 9 while it is kept in a fixed position by a bowl-type 
feeder and a linear feeder. Then the rotary table 8 is rotated, causing a 
stationary terminal 10 and a movable terminal 11 to move in the direction 
of arrow a, as shown in FIG. 7(B), so that the external electrodes 4, 4 
are brought into contact with the two terminals 10 and 11. In this state, 
electrostatic capacity, withstand voltage, insulation resistance, and 
other electrical characteristics are measured. 
In this measuring process, the rotary table 8 rotates at high speed, and 
the productive ability of this measuring apparatus is normally not less 
than 400 pcs/min. To match the high speed operation, the travel of the 
movable terminal 11 is approximately 0.5 mm. Therefore, between the 
electronic part 1 inserted into the rotary table 8 and each of the 
terminals 10, 11, there is only a clearance as small as approximately 0.1 
mm, so that the electronic part 1 rotates in contact with the terminals 
10, 11 while the rotary table 8 rotates. 
In the above-described conventional plating process, devices 3 would be 
stirred so as to collide with one another during the rotation of the 
barrel bath 7. As a result, chips and cracks would occur to the devices 3, 
and besides the plating layer could not be formed at uniform thickness for 
the individual accommodated devices, disadvantageously. 
Also, since the conventional measuring apparatus requires the electronic 
part 1 to be fed in a certain position, such a bowl-type parts feeder 12 
as shown in FIG. 8 is used. When the parts feeder 12 is used, the same 
electronic parts move and slide within the bowl many times, causing the 
external electrodes 4 to be dirtied. These deposits and scratches could 
cause the measurement of electrostatic capacity to result in false values 
of capacity. This in turn may adversely affect the measurement of 
insulation resistance, causing the insulation resistance to lower during 
the measurement. 
Further, in the measuring apparatus, the external electrodes 4 rotate in 
contact with the terminals 10, 11 while the rotary table 8 rotates. As a 
result, impulses due to press contact of the terminals 10, 11 may cause 
scratches to develop to the two external electrodes 4, 4 of the devices 3, 
or contact with the corners of the terminals 10, 11 may cause chips and 
cracks to develop to the devices 3. 
SUMMARY OF THE INVENTION 
Accordingly, to solve these and other problems, it is an object of the 
present invention to provide a method for manufacturing chip-like 
electronic parts, by which uniform plating film thickness can be obtained 
for external electrodes, processes subsequent to formation of the external 
electrodes can be implemented continuously, electrical. characteristics 
can be measured with high accuracy, and by which chips and cracks can be 
prevented from occurring in the devices. 
To solve the above-described problems, the present invention provides a 
method for manufacturing chip-like electronic parts, in which, while 
chip-like electronic parts are held by a retainer sheet, a plating process 
on the chip-like electronic parts and the subsequent processes are carried 
out continuously. 
More specifically, while chip-like electronic parts are held by the 
retainer sheet, the electronic parts are made to pass through the plating 
bath with the retainer sheet used as a transfer medium, whereby the 
plating process on the external electrodes is accomplished. Then the 
retainer sheet is moved as it is, through which the drying process, the 
electrical characteristic measuring process, and the taping process are 
implemented, continuously.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Hereinbelow, an embodiment of the present invention is described with 
reference to FIGS. 1 through 4 of the accompanying drawings. 
As shown in FIGS. 1 to 3, a retainer sheet 21 to be used as a transfer 
medium for chip-like electronic parts 1 is in the form of an elongated 
continuous strip. To retain the chip-like electronic part 1, the retainer 
sheet 21 is provided with a large number of holes 22 slightly smaller than 
the diagonal size of a device 3 or, in the case of a cylindrical device 3, 
than its outside diameter. 
The shape of these holes 22 may be circular, rectangular, hexagonal, or any 
other capable of retaining and fixing the chip-like electronic part 1. 
Also, the material of the retainer sheet 21 may be either metal or 
synthetic resin film. In order that the retainer sheet 21 is used as a 
transfer medium for the plating process and the electrical characteristic 
measuring process, insulating rubber or synthetic resin film is preferably 
used as the material. 
FIG. 1 shows a manufacturing process in which the plating process on the 
electronic part 1 and the subsequent processes are continuously carried 
out by using the elongated retainer sheet 21. On the way of a travel line 
along which the rolled retainer sheet 21 is fed from a take-off reel 23 to 
a take-up reel 24, there are provided an insert section 25 for the 
electronic part 1, a plating bath 26, a cleaning and drying section 27, an 
electrical characteristic measuring section 28, and a takeout section 29 
along the direction of the travel of the retainer sheet 21. 
The retainer sheet 21 is provided with a large number of holes 22 as shown 
in FIG. 2. Into these holes 22, the chip-like electronic parts 1 are 
inserted at the insert section 25. 
The chip-like electronic parts 1 are retained in such a position, as shown 
in FIG. 3, that an electronic part 1 vertically penetrate through the hole 
22 with the inside electrodes 5, 5 positioned upside and downside. 
The retainer sheet 21 that has retained the electronic parts 1 in the holes 
22 at the insert section 25 is traveled to pass through the plating bath 
26, where the electronic parts 1 are immersed in and passed through the 
plating solution. Thus, a plating layer is formed on the surface of the 
inside electrodes 5, 5, whereby external electrodes 4, 4 are formed. 
The electronic parts 1 pass through the plating solution, while being 
retained by the retainer sheet 21 as shown in FIG. 3. Therefore, a plating 
layer of uniform thickness can be formed. 
The electronic parts 1 that have passed through the plating bath 26 then 
pass through the cleaning and drying section 27, where the plating layer 
is dried so that external electrodes 4, 4 are finished. Subsequently, the 
electronic parts 1 go on to the electrical characteristic measuring 
section 28. 
For measurement of electrical characteristics of the electronic parts 1 at 
the electrical characteristic measuring section 28, the electronic parts 1 
retained as stuck into the holes 22 with the external electrodes 4, 4 
positioned at upper and lower surfaces of the retainer sheet 21 can be 
measured for withstand voltage simultaneously by a group of electronic 
parts 1 while, for example, a plurality of electronic parts 1 arrayed in a 
row are pinched by upper and lower terminals. Further, the electronic 
parts 1 can be measured for electrostatic capacity by scanning. 
In this case, since a plurality of parts are simultaneously measured, the 
measuring terminals can be slowed in speed to come into contact with the 
external electrodes 4, 4 at both sides of the electronic parts 1. This 
allows impulses due to the contact to be reduced substantially. As a 
result, there is no possibility that scratches on the external electrodes 
4, 4 or cracks and chips of the devices 3 may take place. 
The electronic parts 1 over the electrical characteristic measurement go on 
to the takeout section 29, where they are withdrawn from the retainer 
sheet 21. The retainer sheet 21 is rolled up by the take-up reel 24. 
At the takeout section 29, the electronic parts 1 are retained in the 
retainer sheet 21. Therefore, they may be taken out as they are, and can 
be subjected to the taping process in which the electronic parts 1 are 
packaged with packaging tape, continuously. 
It is noted that although the retainer sheet 21 has been exemplified by a 
continuous elongated carrier sheet in the present embodiment, yet another 
retainer sheet 21 stretched within a frame 31 and provided with a hole 22 
may instead be used as the transfer medium as shown in FIG. 4. 
As shown above, according to the present invention, chip-like electronic 
parts are retained in holes provided in the retainer sheet, in which state 
the plating process on the external electrodes and the subsequent 
processes are performed continuously. Accordingly, it becomes possible to 
continuously perform the treatment processes on the electronic parts, so 
that improvement in productivity and space saving can be realized. 
Further, by the transfer of electronic parts by the retainer sheet, it 
becomes possible to reduce the number of handling manhours for the 
individual processes and to change the processing method. Besides, 
scratches and adhesion of dirt on the external electrodes, which would be 
involved in the use of the conventional bowl-type feeder, can be 
eliminated, so that any insulation resistance faults can be prevented in 
the electrical characteristic measuring process. Moreover, the possibility 
of occurrence of cracks and chips of the devices during the electrical 
characteristic measuring process can be reduced to a substantial extent.