Wireworking – Crimping
Reexamination Certificate
2000-11-27
2002-08-20
Larson, Lowell A. (Department: 3725)
Wireworking
Crimping
Reexamination Certificate
active
06435222
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and apparatus for manufacturing electronic parts, each of which comprises a lead frame and an electronic element, for example, a quartz resonator mounted thereon, and each being entirely molded using a sealing resin. More particularly, the present invention relates to the bending of leads of the electronic part in the manufacture thereof.
2. Background Art
FIGS. 6A and 6B
are a perspective view of a quartz oscillator and an explanatory drawing of leads of the quartz oscillator respectively. The quartz oscillator
1
comprises a resin mold section
2
with a built-in electronic element and leads
3
projecting therefrom. The resin mold section
2
has recesses
2
a
formed in a bottom portion thereof for housing tip sides of the leads
3
. The leads
3
are bent toward the bottom portion in such a manner as to enclose a side of the resin mold section
2
, and have their tip portions housed in the recesses
2
a
. By folding the leads
3
toward the bottom portion of the resin mold section
2
in the above manner, the height H of the quartz oscillator
1
, including the resin mold section
2
and the leads
3
, is reduced to lessen the thickness and size of the quartz oscillator. The leads
3
are molded by means of three bending operations using progressive press dies.
FIG. 7
shows how the leads are bent during each bending operation. The letter “a” denotes a state prior to bending, and “b” shows that the first bending operation has bent a root portion of each of the leads
3
upward while bending a tip portion thereof downward. The letter “c” shows that the second bending operation has bent the root portion downward. Finally, the third bending operation bends the tip portion of the lead
3
toward the bottom portion to form it as shown in FIG.
6
B.
FIG. 8
shows a pressing section (stage) for a second bending operation. This second bending stage comprises a die
11
, a stripper plate
12
, and a punch
13
. The press bending operation is carried out by lowering the punch
13
while the leads
3
of the quartz oscillator
1
placed on the die
11
are fixedly pressed on the die
11
by means of the stripper plate
12
.
In the second bending stage, a space at which the leads
3
are pressed between the stripper plate
12
and the die
11
(identified by “d” in the drawings) is small, thereby preventing the product from being sufficiently fixed. Thus, although the base portion of the lead
3
must be bent at an edge position of the die
11
, the lead
3
is actually bent at a root thereof with respect to the resin mold section
2
. If the third bending operation is performed in this state, a crevice C occurs in the root of the lead
3
with respect to the resin mold section
2
as shown in FIG.
9
. In addition, if the lead is bent at the root in this manner, the height H of the entire quartz oscillator
1
increases and fails to meet a required quality.
FIG. 10
shows a pressing section (stage) for a third bending operation. The third bending stage employs a cam mechanism for avoiding spring back of the leads
3
. The cam mechanism comprises cam drivers
21
provided on a punch plate side and cam levers
22
rotatably supported and provided on a die plate side. When the cam drivers
21
are lowered, tips of the cam drivers
21
engage with the cam levers
22
to rotationally move the cam levers
22
inward to bend the leads
3
inward.
The cam mechanism of the above described third bending stage avoids the spring back of the leads
3
but creates the following problems when electronic parts are mass-produced:
(1) The shapes of parts of the cam mechanism are so complicated that maintenance operations cannot be easily performed. The shapes of the cam levers
22
and the lever holders
23
are complicated, and in particular, the cam lever
22
cannot be easily shaped, so that fine adjustments are often required during replacement of these parts.
(2) Cam lever shafts
25
are thin (they are forced to be thin due to mechanical restraints) and weak. Further the shafts
25
are easily worn away because the shaft move freely and the cam levers
22
have a narrow and fixed rotational movement range. When the cam lever shafts
25
are worn away, the cam levers
22
may shift from their correct positions, resulting in inappropriate bending.
(3) The cam mechanism (the cam levers) is located on a lower die set side, so that scraps from the resin mold (package) fall into and interfere with the cam mechanism to affect bending accuracy. For example, scraps may be caught in the cam mechanism and may not fall further downward, so that one of the cam levers
22
is stopped at the position shown in the right of FIG.
10
and is prevented from rotational movement. Alternatively, if a large scrap is present in a portion A in
FIG. 10
, the corresponding cam lever
22
cannot be rotationally moved to a final position, thereby preventing the lead
3
from being bent to a predetermined position. The resin mold in this state is fed to the next step, where problems occur that the parts may be destroyed or the dies may be damaged.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method and apparatus for manufacturing electronic parts so as to allow their leads to be accurately bent.
It is another object of the present invention to provide the method and apparatus for manufacturing electronic parts to enable easy maintenance operations.
In a method for manufacturing at least one electronic part according to one aspect of the present invention, each electronic part includes a resin mold section with a built-in electronic element and leads projecting therefrom. The method comprises a first step of forming a V-shaped groove near a root of each of the leads and a second step of pressing a tip side of each lead to bend that lead downward near the V-shaped groove. According to the present invention, since the V-shaped groove is formed near the root of each lead during the first step, a bending position for the second step is set at the position of the V-shaped groove, thereby enabling bending at an appropriate position. In addition, a tip side of the lead is pressed during the second step, so that stress exerted on the root of the lead can be lessened to prevent occurrence of a crevice.
According to another aspect of the invention, the V-shaped groove is formed to have a depth between about one-third and about one-half of a board thickness of the lead. The strength of the recess in the lead is thus retained.
According to another aspect of the invention, in the second step, the lead is bent so as not to close the V-shaped groove. Since the lead is bent at the second step so as not to close the V-shaped groove, a bending portion is set at the position of the V-shaped groove during subsequent bending steps, thereby enabling bending at an appropriate position.
In a method for manufacturing at least one electronic part according to another aspect of the present invention, each electronic part includes a resin mold section with a built-in electronic element and leads projecting therefrom. The method comprises a first step of bending a first portion of each lead to form a first bent portion, a second step of bending a second portion, which is different from the first portion, of each lead to form a second bent portion, and a third step of pressing each lead from obliquely above to bend the lead in such a manner that a tip portion of the lead having the first and second bent portions is located at a bottom portion of the resin mold section. Since the lead is pressed from obliquely above and bent in such a manner that a tip portion of the lead having the first and second bent portions is located at a bottom portion of the resin mold section, an angle &agr; in
FIG. 6B
is secured and the tip of the lead is accurately bent toward a bottom portion of the electronic part.
According to another aspect of the invention, the first bent portion is formed while the lead is simultaneously inclined upward.
Kanbe Eiji
Sato Keiichi
Urushido Hideomi
Gabrik Michael T.
Larson Lowell A.
Seiko Epson Corporation
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