Electric heating – Heating devices – Combined with container – enclosure – or support for material...
Reexamination Certificate
2001-04-13
2003-07-29
Dunn, Tom (Department: 1725)
Electric heating
Heating devices
Combined with container, enclosure, or support for material...
C219S388000, C219S390000, C228S042000, C228S219000, C432S008000, C432S059000, C432S120000
Reexamination Certificate
active
06600137
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a heating apparatus and heating method for hardening an object to be heated located on an object to be bonded (bonding base object) or, for example, a bonding material for bonding an electronic component to the bonding base object, or more specifically for performing, for example, heating of a solder for solder-bonding, hardening of an electronic component fixing use thermosetting adhesive, or hardening of an encapsulation resin of an electronic component (IC chip, etc.), for example, in a process such as a process for mounting an electronic component onto a bonding base object (object to be bonded) such as a circuit board, a component, or a wafer via a bonding material, a process for bonding a board for interposer in a wafer state to a wafer via a bonding material such as a solder bump, or a process for forming a bonding material such as a bump for mounting a component in a state in which no component is mounted.
BACKGROUND ART
In recent years, a technique for mounting an electronic component on a circuit board requires multilayered circuit board, finer mounting density, dual-side mounting, and so on, while there is a growing demand for reducing the consumption power of the apparatus from the point of view of global environment.
Conventionally, in a reflow apparatus for soldering an electronic component onto a circuit board, there has been a heating apparatus that uses heating by a gas heated to a specified temperature, heating by radiant heat of infrared rays or the like, or a combination of them. However, the heating apparatus principally provides heat transfer by the gas heated to a specified temperature, and a variety of methods for circulating the heated gas are devised according to the conventional reflow method and reflow apparatus.
However, fabrication cannot be performed until reaching a specified temperature when a reduction in consumption power is considered. Therefore, it is required to achieve a reduction in consumption power in the operative stage of fabrication and achieve a reduction in consumption power in the inoperative stage of fabrication.
As a prior art example relevant to the method of circulating the heated gas, the method disclosed in Japanese Unexamined Patent Publication No. 6-61640 will be described with reference to
FIG. 10
,
FIG. 11
,
FIG. 12
, and FIG.
13
.
The conventional reflow apparatus has a conveyance section
90
b
for conveying a circuit board
90
a
from an entrance to an exit, a preheating chamber
90
f
, a reflow heating chamber
90
h
, an air circulation path
90
c
in which air is circulated by a sirocco fan
90
d
, and an air heating device
90
e
provided for each air circulation path
90
c
. It is to be noted that the preheating chamber
90
f
and the reflow heating chamber
90
h
are collectively referred to as a furnace section.
The circuit board
90
a
receives thereon a printed solder paste, receives an electronic component mounted on the printed solder paste, and is conveyed through the reflow apparatus by the conveyance section
90
b
. In each air circulation path
90
c
, each sirocco fan
90
d
circulates a specified amount of air, and the air heating device
90
e
heats the specified amount of circulating air to a specified temperature. Through the above-mentioned processes, the circuit board
90
a
conveyed to the conveyance section
90
b
is heated by receiving on its upper surface the circulating air heated to the respective specified temperatures of the preheating chambers
90
f
and the reflow heating chambers
90
h
arranged from the entrance toward the exit. The board is preheated to a specified temperature in the preheating chambers
90
f
, then heated in a reflow manner to a specified temperature for reflow soldering in the reflow heating chambers
90
h
, and finally cooled by receiving cooling air in a cooling chamber
90
g.
However, in the aforementioned prior art construction, as shown in
FIG. 12
, a flow rate Q
1
of the circulating air heated to the respective temperatures of the chambers is constant regardless of the operating state of the apparatus as to, for example, whether the temperature inside the apparatus is in a stable state (state in which a READY signal that is a loading enable signal is ON) at a specified temperature or in an adjusting state (state in which the READY signal that is the loading enable signal is OFF) as well as the presence or absence of a board inside the apparatus. This becomes a factor for increasing and consuming a time for the attainment of the stable state inside the furnace and consumption power.
FIG.
12
and
FIG. 13
show timing charts of the operation of the apparatus to the attainment of the stable state inside the furnace. It is assumed that the heating chamber has the specified temperatures of a low setting temperature and a high setting temperature of t
1
and t
2
, respectively, and t
1
<t
2
. If the atmospheric temperature inside the heating chamber is changed from the low temperature t
1
to the high temperature t
2
by changing the specified setting temperature of the heating chamber from the low temperature t
1
to the high temperature t
2
as shown in
FIG. 12
, then the furnace wall temperature of wall surfaces (heat insulator of, for example, calcium silicate) that constitute the heating chamber reaches the high temperature t
2
later than the atmospheric temperature inside the heating chamber due to the influence of the thermal capacity and the rate of heat transfer. Conversely, if the atmospheric temperature inside the heating chamber is changed from the high temperature t
2
to the low temperature t
1
by changing the specified setting temperature of the heating chamber from the high temperature t
2
to the low temperature t
1
as shown in
FIG. 13
, then the furnace wall temperature of the wall surfaces that constitute the heating chamber also reaches the low temperature t
1
later than the atmospheric temperature is inside the heating chamber due to the influence of the rate of heat transfer.
If a circuit board is heated immediately after the atmospheric temperature inside the heating chamber has reached the specified temperature, then there occurs a large difference in heating temperature by comparison with the stabilized stage since the furnace wall temperature is not stabilized, causing variations in quality. Therefore, by providing a time for stabilizing the furnace wall temperature (for example, after a lapse of a specified time (about 30 minutes to 45 minutes) by a timer after the atmospheric temperature has reached the specified temperature in FIG.
12
and
FIG. 13
) and forming an output of a loading enable signal of the circuit board into the apparatus (i.e., by turning on the READY signal that is the loading enable signal), the variations in quality of the circuit boards are restrained. However, according to this method, the time required for the furnace wall temperature to reach the specified temperature is long, and the time necessary from the temperature setting change to the enabling of heating is long, also causing an increase in consumption power during the time.
Furthermore, when the apparatus is in a heatable condition, the specified amount of heated air, which is required for maintaining the temperature of the atmosphere inside the furnace constant even when no circuit board exists inside the apparatus and controlling the variations in heating temperature of each circuit board when the circuit board is loaded, is circulated, and therefore, consumption power at the time when no circuit board is loaded in the apparatus is increased.
As shown in
FIG. 33
, a general conveyance section
90
b
is constructed of a fixed rail section
90
i
and a movable rail section
90
j
. The movable rail section
90
j
, which is supported in engagement by a screw
90
k
via a nut
90
l
by the rotation of a motor
90
w
and made slidable in a direction in which the movable rail section comes close to or away from the fixed rail section
90
i
, can cope with the width dimension (for example, 50 t
Abe Toshihiro
Matsumoto Kuniyo
Nagafuku Nobuyasu
Nonomura Masaru
Sasaki Takashi
Edmondson L.
Matsushita Electric - Industrial Co., Ltd.
Wenderoth , Lind & Ponack, L.L.P.
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