Heating – Work chamber having heating means – Having means by which work is progressed or moved mechanically
Reexamination Certificate
2002-01-17
2003-09-16
Wilson, Gregory (Department: 3749)
Heating
Work chamber having heating means
Having means by which work is progressed or moved mechanically
C432S145000, C219S388000
Reexamination Certificate
active
06619953
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a reflow furnace for heating a carried circuit module to perform reflow soldering.
BACKGROUND ART
Hitherto, there is adopted a method of soldering that for example, when a circuit module is assembled onto a mother board, the circuit module, in which a soldering bump (for example, 95Pb5S
n
soldering and the like) is placed on a soldering portion, is disposed on the mother board, and the mother board, on which the circuit module is disposed thus, is carried into a reflow furnace which is filled with nitrogen and is maintained a temperature 500° C. or more so that a reflow soldering is performed. In this case, it often happens that there is provided such an arrangement that the mother board and the circuit module on the mother board are conveyed by a conveyance belt into a reflow furnace and are carried out from the reflow furnace as they are on the conveyance belt. In such a case, it is needed for the reflow furnace to have a carrying inlet for carrying the circuit module and the like into the reflow furnace and a carrying outlet for carrying the circuit module and the like out. In the middle of reflow soldering, exposure to oxygen makes it easy to bring about oxidation. This involves a degradation of reliability in mounting. Accordingly, in order that oxygen is hard to enter inside of the reflow furnace, height of apertures of the carrying inlet and the carrying outlet is limited to the order of 1 cm to 2 cm or so which permits a circuit module mounted with no fin to barely pass through the apertures.
On the contrary, recently, in order to increase the productivity, there is increased such a demand that an extremely high circuit module is carried into a reflow furnace to perform a reflow soldering in such a way that the assembled circuit module, on which a heat sink fin is already mounted, is mounted on a mother board. To carry the circuit module, on which a heat sink fin is mounted, into the reflow furnace and carry out the same, there is needed carrying inlet and carrying outlet of the aperture height of 5 cm to 10 cm or so. In this case, simply enlarging the aperture makes air (oxygen in air) easy to enter inside the reflow furnace owing to diffusion or the like. This involves a possibility of degradation of reliability in mounting.
This problem will be described in conjunction with drawings.
FIG. 10
is a typical illustration of a reflow furnace.
FIG. 10
shows a state that a circuit module
101
, on which a heat sink fin
102
is already mounted, is put on a mother board
100
through a soldering bump
103
. The mother board
100
in this state is put on a conveyance belt
200
travelling in an arrow A direction and is conveyed into a box-like shaped furnace
10
.
The box-like shaped furnace
10
comprises a carrying inlet
11
for carrying the mother board
100
(including the circuit modules
101
and the like) into the furnace and a carrying outlet
12
for carrying the mother board
100
out of the furnace.
The furnace
10
has a nitrogen gas supplying section
400
for supplying into the furnace nitrogen gas supplied from a nitrogen gas supplying source
300
via a gas supplying path
301
. The nitrogen gas supplying section
400
is provided with a fan
401
. The nitrogen gas supplied via the gas supplying path
301
is sent out by the fan
401
into the furnace. The nitrogen gas supplied sent out into the furnace fills the furnace and flows out of the furnace via the carrying inlet
11
and the carrying outlet
12
.
Further furnace
10
has a heater
500
in which infrared panel heaters
501
are arranged. The infrared panel heater
501
is a heat source for performing a reflow soldering, and heats the carried mother board
100
(including the circuit modules
101
and the like) to melt the soldering bump
103
.
The carrying inlet
11
and the carrying outlet
12
are provided with a fin
111
and a fin
121
on their inside walls, respectively. Those fins
111
and
121
are for preventing oxygen in air from entering from outside of a furnace in some extent.
FIG. 11
is a typical illustration showing a relation between height (H shown in
FIG. 10
) of an aperture of the carrying inlet or the carrying outlet and a state of entering of the oxygen in air.
FIG.
11
(A) shows a case where height H of an aperture is narrow. FIG.
11
(B) shows a case where height H of an aperture is wide.
Since oxygen O
2
is heavier than Nitrogen N
2
, oxygen O
2
enters a furnace in such a manner that oxygen O
2
gets under Nitrogen N
2
. As compared with a case where height H of an aperture is narrow (FIG.
11
(A)), a case where height H of an aperture is wide (FIG.
11
(B)) is associated with extremely higher possibility that oxygen O
2
enters up to the position nearer to the inside of the main frame of the furnace owing to disturbances of flow of oxygen gas in carrying in and carrying out for the mother board
100
and the like.
As measures of preventing oxygen from entering from the carrying inlet and the carrying outlet, there is considered an adoption of a shutter for selectively covering the carrying inlet and the carrying outlet. In this case, however, when the shutter opens to carry a circuit module into a reflow furnace, air (oxygen) enters the reflow furnace. Thus, there is a need to control a temperature of the reflow furnace in such a manner that a reflow soldering is performed waiting for going down of oxygen density of the reflow furnace. Thus, it takes a lot of time for the reflow soldering and there is a possibility that this will involve a degradation of productivity.
DISCLOSURE OF THE INVENTION
In view of the foregoing, it is an object of the present invention to provide a reflow furnace capable of performing reflow soldering which is high in productivity, while a mounting reliability is maintained high level, even if a height of the aperture of the carrying inlet and the carrying outlet is extensive.
To achieve the above-mentioned object, the present invention provides a first reflow furnace comprising:
a case member having a carrying inlet into which a circuit module is carried and a carrying outlet from which the circuit module is carried out;
a gas supplying section for supplying an inert gas into said case member;
a heating section for heating the circuit module carried into said case member to perform a reflow soldering; and
a nozzle for performing an operation of spraying the inert gas on a soldering portion for the circuit module carried into the case member while said nozzle is moved.
According to the first reflow furnace, there is provided the nozzle as mentioned above. Thus, even if oxygen somewhat enters the furnace from the carrying inlet or the carrying outlet to somewhat increase the oxygen density, so that the oxygen is accumulated on a soldering portion, the accumulated oxygen is blown away by an inert gas ejected from the nozzle so that the reflow soldering is performed in an atmosphere that no oxygen exists. Thus, according to the first reflow furnace; it is possible to implement a high reliability of mounting.
In the first reflow furnace according to the present invention as mentioned above, it is preferable that the first reflow furnace further comprises a sensor for measuring an oxygen density, and said nozzle is selectively operable between emission of the inert gas and stop of the inert gas, and performs said operation when the oxygen density measured by said sensor exceeds a predetermined allowance value.
In this manner, the oxygen density is measured, and the nozzle is operated only in the necessary case in accordance with the measured result. This feature makes it possible to prevent the inert gas from being used to no purpose and also to avoid waste for time necessary for blowing oxygen away.
To achieve the above-mentioned object, the present invention provides a second reflow furnace comprising:
a case member having a carrying inlet into which a circuit module is carried and a carrying outlet from which the circuit module is carried out;
a gas supplying section for supplying an inert gas
Shimizu Kouichi
Yamaoka Nobuyoshi
LandOfFree
Reflow furnace does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Reflow furnace, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Reflow furnace will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3078648