Substrate for mounting electronic part

Details Substrate for mounting electronic part Substrate for mounting electronic part

1999-06-10

2001-05-08

Sough, Hyung Sub (Department: 2841)

Electricity: conductors and insulators

Conduits, cables or conductors

Preformed panel circuit arrangement

C174S265000, C174S267000, C257S734000, C361S772000, C439S046000, C439S083000, C439S084000

Reexamination Certificate

active

06229101

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a substrate for mounting an electronic part, allowing a conductive pin to be inserted and secured in a through hole firmly, a method for producing such substrate and the conductive pin and particularly, to a structure of the conductive pin.
2. Description of the Related Arts
Referring to
FIGS. 16 and 17
, a conventional substrate
9
for mounting an electronic part is composed of an insulating substrate
90
, a recessed space
95
in a center of the insulating substrate
90
where an electronic part is mounted and a frame-like dam
98
formed around the periphery of the recessed space
95
. Reference numerals
93
and
94
designate a conductive circuit and a land, respectively.
A head
921
of a conductive pin
92
is inserted into a through hole
91
so that the head
921
is electrically connected to a plating layer
911
coated with an inner wall of the through hole
91
. The conductive pin
92
is provided with a collar
922
and a leg
923
. The conductive pin
92
inserted into each corner of the insulating substrate
90
is further provided with a lower collar
924
.
Referring to
FIG. 17
, the head
921
of the conductive pin
92
is bonded to the through hole
91
by soldering of a solder
8
in order to reinforce the electric bonding and further to provide mechanical strength between the conductive pin
92
and the through hole
91
.
The soldering is executed by using a reflow method as shown in FIG.
17
. That is, the solder
8
melted into a molten state is supplied in the direction opposite to the insertion of the conductive pin
92
.
More specifically, as shown in
FIG. 18
, the head
921
of the conductive pin
92
is inserted into the through hole
91
of the insulating substrate
90
, on which a solder paste
81
formed of solder particles, flux or the like is placed and then heated for melting. The molten solder
8
flows into a solder gap defined by the through hole
91
and the head
921
for bonding therebetween (See FIG.
17
).
The above-described substrate
90
for mounting an electronic part is of a face down type, in which the conductive pin is inserted from the same surface where the recessed space
95
for mounting an electronic part is formed.
In the above conventional art, the smaller the diameter of the head
921
of the conductive pin
92
becomes, the easier the head
921
can be inserted into the through hole
91
. In case the diameter of the head
921
is too small, the conductive pin
92
is likely to fall out from the through hole
91
in the middle of the soldering process. While in case the diameter of the head
921
is too large for tight fitting, the conductive pin
92
cannot be fully inserted, failing to have the collar
922
abutted on the land
94
, or an inner wall of the through hole
91
might be cracked or the plating layer coated with the inner wall surface of the through hole
91
might be peeled off because of strong pressure exerted to the inner wall during insertion.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a substrate for mounting an electronic part, a producing method thereof and a conductive pin, by which the conductive pin can be inserted and secured firmly without damaging a through hole.
The present invention is realized by a substrate for mounting an electronic part comprising an insulating substrate provided with a conductive circuit, a through hole formed in the insulating substrate and a conductive pin having a leg and a head inserted into the through hole. The head of the conductive pin is provided with a plurality of projections at its side wall, each projecting radially in 4 or more directions. The projections form a plurality of projection pairs, each projection of which is extending in an opposite direction from an axial center of the head. The projection pairs include a primary projection pair having the largest length and a secondary projection pair having the next largest length. The length of the primary projection pair is equal to or more than an inside diameter of the through hole. The length of the secondary projection pair is less than the inside diameter of the through hole.


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