Metal fusion bonding – Process – Applying or distributing fused filler
Reexamination Certificate
2002-05-24
2004-10-19
Stoner, Kiley (Department: 1725)
Metal fusion bonding
Process
Applying or distributing fused filler
C228S233200, C228S037000
Reexamination Certificate
active
06805282
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a flow soldering process for mounting a component(s) such as an electronic component(s) onto a board (or substrate) by means of a solder material, and also relates to an apparatus for such process.
BACKGROUND ART
A flow soldering process utilizing a molten solder material in the form of a wave(s) has been conventionally known as one of processes for connecting an electronic component or the like to a board in the field of production of an electronic circuit board. Such flow soldering process generally includes a flux applying step for applying flux onto a board, a preheating step for heating the board in advance, and a solder material supplying step for supplying a solder material to the board by contacting the board with a wave(s) of the solder material. Hereinafter, the conventional flow soldering process will be described with reference to the drawings.
FIG. 15
is a schematic side view of the conventional flow soldering apparatus while showing its internal construction.
FIG. 16
is a schematic view of the flow soldering apparatus of
FIG. 15
when viewing it from a cross section taken along an X′—X′ line.
At first, a board is supplied with flux by a flux supplying means (not shown) while applying the flux onto a lower surface of the board. The board is, for example, a printed circuit board onto which an electronic component such as a “through hole insertion component (or an inserted component)” (i.e. a component a part of which is inserted into a through hole, for example, a discrete component or a lead component) is to be mounted at a predetermined position according to a known manner. The flux generally contains an active ingredient such as rosin (a resin component) as well as a solvent such as isopropyl alcohol. The flux applying step for applying such flux to the board is conducted in order to improve wettability and a spreading property of the solder material on a surface of a land formed on or through the board (i.e. a portion to be supplied with the solder material) by removing an oxide film (a naturally oxidized film) which is unavoidably formed on the land. As the flux supplying means (or device), a spray fluxer for spraying the flux in the form of mist to the board, a foam fluxer for contacting the board with the flux in the form of foam or the like can be used. These flux supplying means can be situated separately from a flow soldering apparatus
60
of
FIG. 15
, though the flux supplying means can form the flow soldering apparatus
60
by integrally incorporating the flux supplying means in the flow soldering apparatus
60
.
The board
71
applied with the flux as described above is then fed into the flow soldering apparatus
60
shown in FIG.
15
through an inlet
61
thereof. The board
71
is mechanically conveyed in a direction of an arrow
62
(hereinafter referred to as a conveyance direction) inside the apparatus
60
(along the conveyance line shown as a broken line in
FIG. 15
) at a substantially constant speed. More specifically, the conveyance of the board
71
is conducted by holding the board
71
with conveyance fingers
72
a
and
72
b
at its both edge portions which locate on opposed right and left sides of the board when viewing the board towards the conveyance direction
62
as shown in FIG.
16
and by mechanically moving the conveyance fingers
72
a
and
72
b
in the conveyance direction of the arrow
62
. The conveyance fingers
72
a
and
72
b
are connected to chains
74
a
and
74
b
respectively and run around conveyer frames
73
a
and
73
b
respectively in a plane parallel to a principal plane of the board
71
. The conveyer frames
73
a
and
73
b
extend from the inlet
61
to an outlet
69
shown in FIG.
15
. The conveyer frame
73
a
is a base conveyer frame which is fixed, and the conveyer frame
73
b
is a width adjustable conveyer frame which can slide in directions being perpendicular to the conveyance direction and able to keep parallel to the fixed conveyer frame
73
a
(in other words, which directions are shown as a left and right arrow in FIG.
16
and lateral in the sheet of FIG.
16
).
The board
71
conveyed in the apparatus
60
from the inlet
61
toward the outlet
69
as described above is firstly heated by a preheater
63
locating under the conveyance line of the board, for example a far infrared heater. Such heating step is referred to as a preheating step. The preheating step is conducted for vaporizing and removing an unnecessary solvent ingredient in the flux applied onto the board
71
through the above described flux applying step so as to leave only the active ingredient on the board
71
and also for preheating the board
71
prior to supply of a solder material
64
to the board
71
so as to alleviate a heat shock of the board
71
upon contacting the board
71
with a molten solder material
64
. The preheater
63
is located under the conveyance line by generally being put on a bottom of a channel structure (or support)
76
which is open on its upside and which is connected to the fixed conveyer frame
73
a
and a fixed frame
75
at its top portions. Thus, the preheater
63
heats the board
71
from a lower side of the board
71
which is the same side to which the solder material is supplied in the following solder material supplying step.
The board
71
is subsequently conveyed above a solder material supplying means (or unit)
66
which includes a solder bath
65
. The solder bath
65
contains the solder material
64
which is in a molten state by heating beforehand. A distance “d
1
” between the preheater
63
and the solder bath
65
(i.e. a distance along the conveyance direction between them) is generally about 70 to 150 mm. When the board
71
goes over the solder material supplying means
66
, the board
71
is contacted at the lower surface of the board
71
with a primary wave
67
and a secondary wave
68
of the solder material
64
, so that the solder material
64
is supplied to the board
71
. As the solder waves
67
and
68
are shown in
FIG. 17
while enlarging them, a distance “d
2
” between the primary wave
67
and the secondary wave
68
(more specifically, a distance along the conveyance direction from a position at which a certain point of the board
71
leaves the primary wave to a position at which the certain point begins to contact with the secondary wave) is generally about 80 to 150 mm.
In this solder material supplying step, the solder material
64
which is supplied in the form of the primary wave
67
rises in an annular space between a land portion and a lead
74
of the through hole insertion component
73
from a lower side of the board
71
by the capillary phenomenon as shown in
FIG. 18
, wherein the land portion forms a wall of the through hole
72
perforated through the board
71
and the lead has been inserted through the through hole from an upper side of the board. An excess amount of the solder material
64
adhering to the lower surface to the board
71
by the primary wave is removed by subsequently contacting the solder material
64
in the form of the secondary wave
68
with the board
71
. Then, the solder material which is supplied and adheres to the board
71
solidifies with a drop in its temperature and forms a so-called “fillet” as a connection portion of the solder material.
In such solder material supplying step (or flow soldering step), the primary wave
67
is directed for sufficiently wetting a surface of the land
75
which covers the wall of the through hole
72
(as well as wetting the lead
74
of the electronic component) with the solder material and for supplying the solder material into the through hole
72
. If it is insufficient, the solder material does not rise up along the annular space between the lead
74
and the land portion which forms the wall of the through hole
72
, so that there occurs a problem of a so-called “red eye (or non-wetting)” (which is referred to as “akame” in Japanese), for example. The “red eye” is, in other words, a phenomenon i
Hibino Shunji
Kabashima Shoshi
Kawashima Yasuji
Maeda Yukio
Nakata Mikiya
McHenry Kevin
Stoner Kiley
Wenderoth , Lind & Ponack, L.L.P.
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