Note: Descriptions are shown in the official language in which they were submitted.
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?.E- 3 71 PATENT
PRESS-FIT CONNECTION PIN
1 FIELD OF THE INVENTION:
The invention concerns a connection pin for
insertion into a through-metallized bore in a printed
circuit board.
BACKGROUND OF THE INVENTION:
Connection pins of the press-fit kind are known
for what is referred to as the solder-free connection
procedure. In a known connection pin (German patent
specification No. 2,937,883) the pxess-in portion is
~0 cylindrical and the introduction portion is conicalO That
means that the outside diameter of that known connection pin
increases to its full dimension without a transition in the
plane between the introduction and the pr~ss-in portions.
That further means that, when the connection pin is pressed
into the bore in a printed circuit board, the connection pin
suddenly enlarges the bore as soon as its press-in portion
reaches the upper edge of the bore. The compacting effect
on the material of the printed circuit board, which occurs
in that situation, does not cause any further risk. It
~0 happens, howev~r, that the metallization of the bore may be
scraped off and fine cuttings or slivers formed. Some time
afterwards, such slivers may come out of the bore and give
rise to unacceptable short-circuits. There is also the
danger of the conductive layers or conductor tracks in a
`25 multi-layer printed circuit board being deformed. The
recess which is provided in the known connection pin in the
press-in portion thereof does not in any way alter that
situation. It enhances the resiliency of the press-in
portion and permits the limhs deining same to move towards
each other when the press-in portion is pressed into the
bore. However, it does not have any influence on the
resiliency of the connection pin in the plane thereof
between the introduction and the press-in portions. The
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1 connection pin remains stiff there. In a further known
connection pin ~U.S. Patent No. 4,776,807) the press-in
portion has three protrusions which are spaced around its
periphery. As a result it no longer bears against the
inside of the bore, with the entire periphery of the press-
in portion, but only along three vertical extending lines.
The risk of cuttings being ~ormed and the danger of
excessiv~ deformation of the material of the printed circuit
board may still occur.
SUMMARY OF THE INVENTION:
Taking that state of the art as its basic starting
point, the invention is based on the problem of designing a
connection pin so that, when it is pushed into a printed
circuit board, cuttings are not scraped off the
metallization of the bore, nor is the material of the
printed circuit board excessively deformed. In a connection
pin of the kind set forth in the openin~ part of this
specification, in accordance with the invention, the
solution to that problem is achieved in that the press-in
portion is preferably of an outside diameter which slightly
decreases conically in a downward direction. At the lower
end of the press-in portion there is a transition region to
the introduction portion. The transition region has a first
portion of decreasing outside diameter, an adjoining second
portion of constant outside diameter, and an adjoining third
portion of a diameter which decreases to the outside
diameter of the introduction portion. The result oE such
configuration of the press-in portion is that, when the
press-in portion is pushed into the printed circuit board,
the material thereof is only gradually compressed and thus
uniformly deformed. In that way the inner layers and
conductor tracks of multi-layer printed circuit boards tend
not to be damaged. The same purpose is served by the
transition region bet~een the introduction and the press-in
portions. With its three portions with first an increasing
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1 outside diameter, then a uniform outside diameter and
finally an increasing outside diameter, as viewed in the
direction from the introduction up to the press-in portion,
it further provides that, after initial compacting, during
the insertion o~ the second portion with a uniform outside
diameter, the material of the printed circuit board settles
and experiences further compacting only upon insertion of
the further portion with an outside diameter which again
increases. Such gradual expansion of the bore of the
printed circuit board also means that the metallization
thereof is treated carefully. The metallization is
gradually pressed radially outwardly into the material of
the printed circuit board, without cuttings being formed in
that situation. That means that the material surrounding
the bore, and the metallization thereof, are only compacted
when the COnneGtiOn pin is pressed into position, without
being deformed or forming cuttings.
The outside diameter of the press-in portion
desirably has a conicity of 0.5. The press-in portion
itself is of C-shaped cross-section. The ends of the limbs
of the C-shape, which embrace the recess, are rounded of~.
Desirably they are rounded off both on their inward and on
their outward sides. That avoids excessive pressing
pressures which could occur at ends which converge in a
point~ That arrangement likewise prevents cuttings from
being scraped off the metallization upon a rotary movement
of the connection pin.
The limbs of the C-shape are of a wall thickness
which increases towards their ends. In that axrangement the
inward and outward sides of the ends of the limbs of the C-
shape both desirably e~tend slightly outwardly with an
increase in wall thickness. That means that the C-shape is
narrower and is thus particularly flexible in its central
region between its two limbs. That enhances the resiliency
of the press-in portion when it is pushed into the printed
circuit board.
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1 BRIEF DESCRIPTION OF THE DRAWINGS:
The invention will now be described in further
detail by way of the example of the embodiment illustrated
in the drawing in which:
Figure 1 is a perspective view of ~he cOnneCtiOD
pin.
Figure 2 is a view in longitudinal section of part
of the connection pin r taken along section line II - II in
Fig. 1.
Figure 3 is a side view of the lower xegion of the
connection pin of FigO 2.
Figure 4 is a view in longitudinal section showing
the lower region of the connection pin inserted into a part
of a printed circuit board.
Figure 5 is a view in cross-section taken along
section line V - V in Fig. 4.
Figure 6 is a view in cross-section tak~n along
section line VI - VI in Fig. 4.
Figure 7 is a view in cross-section taken along
section line VII - VII in Fig. 4.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS:
Figure 1 shows the connection pin with its
connection portion 12, its press-in portion 14 and a
transition region 16 comprising first, second and third
portions 1~, 20 and 22, and with its introduction portion
24. The introduction portion 24 is divided into a square
portion 26 and a tip 28. A recess 30 is disposed within the
press-in portion 14, recess 30 having an upper portion 32
and a lower portion 34. The shape of those two portions 32
and 34 corresponds to the shape of the outside walls
enclosing them.
As illustrated, the press-in portion 14 is of
substantially C-shape. The two limbs of the C-shape are
identified by~reference numeral 36 in Figs. 5 through 7.
The ends 38 thereof have rounded configurations 40 at their
outward sides and rounded configurations 42 at their inward
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1 sides. The printed circuit board, into the numerous bores
in which connection pins are pressed, is seen in part in
Figs. 4 through 7 and is identified by reference numeral 44.
The bore for receiving the connection pin 12 is identified
by reference numeral 46. Metallization 48 is provided on
the inside wall thereof. The press-in portion 14 does not
bear a~ainst the metallization 48 or the bore 46 with the
whole of its outside wall, but only at some locations. The
contact points are identified by reference numeral 50.
The connection pin is made from a square starting
metallic material with a cross-section of for example 1 mm~.
In the final condition the outside diameter of the press-in
portion 14 is more than the inside diameter of a bore 46.
The connection pins may be urged into the
lS metallized bores in a printed circuit board by a robot under
the control of a computer, with a force of about 10 kg.
Firstly, the tip 28 and then the square portion 26 pass into
the bore 46. The latter is still not touched. In the
further movement of the connection pin, the third portion 22
then encounters, with its diameter which increases in an
upward direction, the top edge of the bore 46. The bore 46
is gradually enlarged in the further movement of the
connection pin. The second portion 20 then passes with its
uniform diameter into the boxe 46. In further movement, the
material of the printed circuit board can settle and is not
subjected to further deformation. Finally, the first
portion 18 passes with its diameter which increases again,
into the bore 46. The bore 46 is further enlarged. When
the upper end of the first portion 18 reaches the upper edge
of the bore 46, the speed at which the latter is enlarged
has reached a maximum. In Eurther movement of the
connection pin the press-in portion 14 passes into the bore
46. The conicity of 0.5 of the outside wall thereof is
below the conicity of the first portion 18. Therefore, when
3S the press-in portion 14 is passed into the bore 46, the bore
2 ~ 3
o
l is enlarged over a longer period of time, but to a lesser
degree per unit of time. That means ~hat the material of
the printed circuit board including the conductor tracks or
conductive layers disposed therein is neither damaged nor
irregularly deformed. When the press-in portion 14 is
pressed into the bore 46, the limbs 36 of the C-shape also
move towards each other. That also provides careful
- treatment for the material of the printed circuit board 44
and the metallization 4~.
- Figures 4 through 7 show how the press-in portion
14 bears against the inside o~ the bore 46 or the
metallization 48 thereof. As a result of the thickening at
the ends 38 of the limbs 36 of the C-shape and the resulting
relative weakening in the central region which joins the
limbs, the press-in portion 14 contracts radially inwardly
approximately at the halfway position in the height of the
bore 46. Figure 4 shows this condition. The press-in
portion 14 bears against the metallization 48 of the bore 4~
only a short distance below the upper edge and a short
distance above the lower edge of the bore. Figur~ 4 also
shows this condition. The press-in portion 14 is
constricted at its center. That phenomenon is referred to
as a guitar effect. In the two planes in which the press-
in portion 14 bears against the metallization 4~, there is
no line contact but only point contact. Figure 4 and in
particular Figures 5 and 7 show this situation. The press-
in portion 14 only bears against the metallization 46 at
three contact points 50. At the halfway position in terms
of the height of the bore 46, because of the guitar effect,
it even bears against the metallization 48 only at two
contact points 50. That is clearly shown in ~igure 6.
However, the contact of the press-in portion 14 at three
respective contact points 50 in a lower plane and an upper
plane respectively is sufficient for the entire connection
pin to be held in the bore 46 in such a way that it cannot
tilt or turn~ In that respect it is to be noted that the
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1 two ends 38 of the limbs 36 are urged constantly outwardly
against the metallization 48 as a result of the resiliency
of the press-in portion 14.
The true scope of the invention is set forth in
the claims appended hereto.
