Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
2001-10-25
2003-08-26
Arbes, Carl J. (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S566300, C029S741000, C029S739000, C029S825000
Reexamination Certificate
active
06609295
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an apparatus for mounting electronic components with leads onto a circuit board substrate by inserting the leads of the electronic components in corresponding holes in the circuit board substrate, and further to a method and device for detecting the attachment of electronic component with leads to the circuit board substrate.
BACKGROUND ART
Mounting of an electronic component with leads onto a circuit board substrate is generally achieved by an action for fixing leads of the electronic component
20
to the circuit board
22
as shown in FIG.
9
. Leads
21
of the electronic component
20
are inserted into corresponding holes
29
formed in the circuit board
22
. A clinch means comprising a clinch lever
25
and a clinch bed
26
is moved to below the holes
29
in which leads
21
have been inserted. The tip of the lead
21
which has pierced through the circuit board
22
to the backside thereof is cut to a predetermined length by the clinch lever
25
moving toward the clinch bed
26
. The lead
21
is clinched against and fixed to the circuit board
22
by further movement of the clinch lever
25
.
A piezoelectric element
1
is attached to the clinch lever
25
for detecting stress-strain which is generated in the clinch lever
25
at the time of cutting and clinching the lead
21
. From the stress-strain amount detected by the piezoelectric element
1
, it is detected whether the electronic component
20
has correctly been mounted onto the circuit board
22
. If the leads have not been inserted or pierced through the holes
29
, or have been bent when being inserted into the holes, the clinch lever
25
accordingly receives less load. On the other hand, if the leads are properly inserted in the holes, the clinch lever
25
receives a great load upon cutting and clinching the leads, whereupon the piezoelectric element
1
detects large stress-strain. Therefore, the detected stress-strain of the clinch lever reflects the quality of the attachment of the electronic component
20
to the circuit board, and thereby it is detected whether the electronic component has been mounted in a favorable condition. For this purpose, the piezoelectric element
1
is connected to an insertion detecting circuit shown in FIG.
10
.
Referring to
FIG. 10
, the stress-strain that is generated in the clinch lever
25
is detected by the piezoelectric element
1
, and an electric signal proportional to the amount of detected stress-strain is amplified by a differential amplifier
32
. A &pgr; filter
33
is provided for cutting high frequency component from the electric signal sent from the differential amplifier
32
so as to remove noise components mixed at the piezoelectric element
1
. The electric signal from which noise components have been removed is amplified by a variable gain amplifier
34
, so that it is compared by a voltage comparator
35
with a threshold which is a reference for judging whether the leads
21
of the electronic component
20
have properly been inserted in corresponding holes. The voltage comparator
35
is a circuit designed for comparison of an inputted voltage with a reference voltage (threshold). The threshold as the reference voltage can be preliminarily set, so that the voltage inputted from the variable gain amplifier
34
is compared therewith, and when the inputted voltage is greater than the threshold, the voltage comparator
35
changes its output voltage accordingly. With this change in voltage outputted from the voltage comparator
35
as a trigger, a monostable multivibrator
36
outputs a pulse, which is in turn inputted into the electronic component mounting apparatus from an output terminal
38
via a transistor
37
. The apparatus thereby judges whether the electronic component with leads has correctly been fixed on the substrate.
There is now remarkable diversity in electronic components and component with leads is no exception. Therefore, diameter and material of the leads, and shearing stress necessary to cut the leads also come in many varieties. In the conventional insertion detecting circuit described above, however, the threshold for judgement by the voltage comparator
35
is set to a constant voltage. Upon changes to the diameter, material, or shearing stress of the leads, the stress-strain that occurs in the clinch lever
25
changes as well as the amount of stress-strain detected by the piezoelectric element
1
. Accordingly, the judgement by the voltage comparator
35
was sometimes incorrect. Misjudgment also occurred in the cases such as when the clinch lever
25
, clinch bed
26
, or the piezoelectric element
1
was replaced, when the shape of the clinch lever
25
or clinch bed
26
varied, or when the piezoelectric element
1
having characteristics suitable for one type of apparatus was applied to a different type of apparatus.
In order to deal with such problems, it was necessary to change the preset threshold voltage in the voltage comparator
35
, or to effect gain adjustment of the variable gain amplifier
34
. However, such operation for changing the settings was not easy, and it is not realistic to change the settings of the circuit in accordance with changes in the stress-strain detected by the piezoelectric element
1
. Not to mention, if the diameter, material, or shearing stress of leads on an identical electronic component differs, such could hardly be dealt with.
An object of the present invention is to provide a method and device capable of correctly judging whether an electronic component with leads has properly been fixed on a circuit board substrate with its leads being inserted in corresponding holes in the circuit board substrate.
DISCLOSURE OF THE INVENTION
In order to achieve the above objects, the present invention provides a method of mounting an electronic component with leads on a substrate, wherein the leads of the electronic component are inserted into corresponding holes formed in the substrate, and clinched with a clinch means so that the electronic component is fixed on the substrate, characterized by comprising the steps of:
selecting a standard reference value for determining whether or not the leads of the electronic component have been inserted in the holes, said standard reference value being selected based on values representative of characteristic features of the electronic component with leads such as diameter, material, or shearing stress of lead;
detecting stress-strain generated in said clinch means; and
comparing a detected stress-strain with the selected standard reference value, whereby it is determined whether or not the electronic component with leads has been mounted to the substrate.
The apparatus for mounting an electronic component with leads on a substrate, according to the present invention, comprises an insertion head for inserting the leads of the electronic component into corresponding holes formed in the substrate, a clinch means for clinching the leads that are inserted into the corresponding holes for mounting the electronic component to the substrate, a detecting means for detecting stress-strain generated in the clinch means, and a judging means for determining whether or not the electronic component with leads has been mounted on the substrate based on a detected result obtained by the detecting means, and is characterized in that:
the judging means includes a plurality of threshold values that are preset therein, and comprises a threshold output means that is capable of selectively outputting one of these threshold values as a standard reference value for detecting the attachment of the electronic component to the substrate, a threshold selecting means for selecting one of the threshold values in accordance with the type of electronic component with leads which is to be mounted to the substrate, and an insertion detecting section which compares a detected result obtained by the detecting means with the selected threshold.
The present invention further provides a method of detecting the attachment of an electronic c
Koyama Toshiyuki
Taniguchi Satoshi
Arbes Carl J.
Greenblum & Bernstein P.LC.
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