JPS63296295A - Furnace for thermosetting adhesive for fixing chip component - Google Patents

Abstract

PURPOSE:To create a temperature difference between the upper and lower surfaces of a printed board and realize a high mounting density of chip components by a method wherein hot air is returned to a heater part by a hood plate and a hot air guide plate and staying heat is discharged to the outside by a mesh belt. CONSTITUTION:A fan 10 is driven to blow hot air of a heater 9 against the upper surface of a printed board 18 which is placed on an endless chain-belt 7 and conveyed to heat respective components to a predetermined temperature. The excessive air is returned to a hot air passage through the space between the skirt of a hood plate 8 and the edge of the printed board 18 by a guide plate 4 and, at the same time, heat staying below the printed board substrate 21 is brought out by a mesh belt 15 which is circulated to the direction opposite to that of the endless chain-belt 7 so that the lower surface temperature of the printed board substrate 21 is always maintained lower than the upper surface temperature. With this constitution, the adhesive of chip components 16 can be subjected to a thermal curing process while discrete components 17 and chip components 16 are mounted.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a thermosetting furnace for fixing adhesives for chip components on printed circuit boards used in various electronic devices.

<Conventional technology> Conventionally, when mounting chip components and discrete components onto a printed circuit board, there is first a process of applying a thermosetting adhesive to the required portions to attach the chip components to one side, that is, the top surface of the printed circuit board, and then The process involves attaching each chip component to a predetermined position (in this case, it is only lightly adhesively attached), and then passing it through a thermosetting oven at a constant temperature to harden the adhesive and form the chip. A step of fixing the components, a step of flipping the printed circuit board upside down to mount the discrete component, a step of inserting the terminal of the discrete component into the board and mounting it, and a step of attaching the terminal of the discrete component to the wiring pattern of the printed circuit board. The process consists of a soldering process, and the work is carried out in the order mentioned above.

Therefore, the chip component 16 or 16' is attached to one side (or both sides) of the printed circuit board 21, and the discrete component 17 is attached to the other side.
Moreover, the terminals 19 of the discrete component 17 are clinched (the protruding ends of the terminals are bent) between them and the chip component 16 on the back side.

<Point J to be solved by the invention> In the above conventional example, it is not possible to control the temperature differently on the upper and lower surfaces of the printed circuit board, so the chip component 16 or 1
The discrete component 17 cannot be protected from heat damage unless the terminal 19 of the discrete component 17 is inserted into the printed circuit board 21, transferred to a solder bath, and soldered after the terminal 19 of the discrete component 17 is installed and solidified by heating. Ta.

From the above, when mounting the discrete component 17, as shown in FIG. 5, between the terminal 19 of the discrete component 17 and the chip components 18.
The operating gap a, a of the tool is required to clinch the insertion end of the terminal 19, and if the chip components 16', 16' are installed on both sides of the discrete component 17, the discrete component 17 and chip parts 1 on both sides
6' and 16', an insertion gap of 20 degrees 20 for the component holder is required.

Therefore, in the conventional example described above, although the number of steps is small, high-density mounting of chip components and discrete components is impossible, which limits miniaturization.

When a discrete component is installed, if the terminal gap of the component does not exactly match the mounting hole of the printed circuit board 21, the printed circuit board is likely to warp due to the restoring stress of the pitch between the terminals, and it must be corrected. Since the soldering process is carried out as is, high-quality products cannot be obtained and yields are poor.

SUMMARY OF THE INVENTION The present invention addresses the above-mentioned drawbacks of the prior art and aims to provide a thermosetting furnace that is of high quality and enables high-density component mounting.

Measures to solve the problems〉 An endless chain belt for transporting unprocessed parts installed inside the furnace body with a heat-insulated exterior, a mesh belt circulating in the opposite direction to the endless chain belt, and a mesh belt above the endless chain belt. A hot air hood plate provided along the endless chain belt, a heater provided between the hood plate and the furnace body, an air blower installed on the top of the hood plate, and a hot air guide provided below the mesh belt. It consists of a board.

By rotating the blower device, the hot air generated by the heater installed between the hood plate and the furnace body is turned into hot air, which moves from the top of the hood plate, through the hood plate thickness, and then directly below it at a constant speed. The hot air guide plate heats each component on the top of the printed circuit board to a certain temperature while passing the afterflow between the hem of the hood board and the edge of the printed circuit board. The heat that remains in the space under the printed circuit board is immediately returned to the hot air passage between the hood plate and the furnace body, and the mesh belt is circulated inside and outside the furnace in the opposite direction to the printed circuit board. is carried outside by the mesh belt, and the temperature of the bottom surface of the printed circuit board is always kept lower than the temperature of the top surface.

<Examples> The present invention will be described in detail below using examples shown in the drawings.

As shown in Figures 1 to 3, the stainless steel exterior plate 2
A box-shaped furnace body 1 is formed by interposing a heat insulating material 3 between the inner panel 2' and the inner plate 2', and two strips of horizontally installed straddles from one side wall of the furnace body 1 to the other side wall. A pair of endless chain bands 7, 7 are guided on the guide rail 6.6, and the chain bands 7, 7
The inlet 11 and the outlet 1 on both side walls of the furnace body 1
It is horizontally stretched so that it can be pulled out and circulated outside the furnace main body 1 through 2.

Both ends of the printed board 18 to be processed are placed and held between the endless chain belts 7 and 7, and are conveyed continuously in one direction. A mesh belt 15 is stretched parallel to the chain belt 7 and circulates from outside the furnace to inside the furnace in a direction different from the circulation direction of the chain belt, and above the endless chain belt 7.7. is provided with a hood plate 8 extending along the direction of movement of the chain belt 7.7, and the hood plate 8 is provided between the side walls 1'1' of the furnace body 1 and the ceiling 1. It has a shape that surrounds the space above the endless chain belt with a constant gap, and the hem part is opened just above the outer side between the endless chain belts 7 and 7.

Further, on the upper part of the hood plate 8, fan motors 10', 10', .
Fans 10, 10, .

A plurality of fin heaters 9.9 are installed in the ventilation path formed between 1° and far infrared heaters 13, 13 near the entrance of the endless chain band 7.7 in the hood plate 8.
... are installed to form a path for hot air to circulate through the inside and outside of the hood plate 8.

As shown in FIGS. 2 and 3, below the endless chain band 7.7, there is a flat surface 41 with a width approximately corresponding to the center of the printed board 18, and on both sides of the flat surface 41, an upward direction is formed. 4. Inclined surface formed by bending. The hot air guide plate 4 consisting of the chain bands 7, 7
A wind cooling chamber is formed in the lower part of the furnace body 1 by providing the hot air guide plate 4 along the extension direction of the furnace body 1, and the lower surface of the hot air guide plate 4 is arranged in a continuous or fragmented direction from the inlet 11 to the outlet 12 of the furnace body 1. One or more rows of straightening fins 4', 4', . 5. , ... to the exhaust port 52.5 provided near the inlet for the outside air introduced by the fan 5', 5°.
The air is discharged to the outside through exhaust fans 5'', 5'', etc. through □.

In addition, in the above configuration, the temperature inside the furnace is displayed by a digital display, and the temperature inside the furnace is adjusted by a temperature sensor and a temperature control circuit.
3.14 shows the exhaust duct.

Next, to describe a series of operations of the curing furnace, as a pre-processing step in the curing furnace, first, the printed circuit board 21 is
Terminals 19.1 of discrete components 17.17...
9 is inserted, the insertion ends of the terminals 19 and 19 are expanded and bent to form a mounting state (not shown), and then the printed circuit board 21 is turned upside down. That is, in this state, the discrete components 17, 17... are positioned below the substrate 21, and the chip components 16, 16... are fixed at predetermined positions on the upper surface of the substrate 21. After applying the adhesive, place the chip parts on each.

That is, after temporarily installing the discrete components, the chip components are left still, and the printed board 18 in this state is placed between the endless chain bands 7 and 7 in the thermosetting furnace of the present invention, and the arrows shown in FIG. Convey at a constant speed in the direction.

In the thermosetting furnace of the present invention, the heater 9°9...
The fan 10 guides the hot air heated at the section .
Chip parts 16, 16, .
The adhesive applied to fix the chip components 16, 16, etc. is cured by heat, thereby fixing the chip components 16, 16, .

At this point, the current wind blowing onto the printed board 18 is blocked by the printed board 18 and turned to the side, flows out to both sides through the hem of the hood board 8, and is directed upward at the inclined surface 42 of the guide board 4. It is reflected and becomes hot air through the fin heaters 9, 9, .

In the transport section of the printed board 18, the printed board 18 is
In addition, the airflow is blocked by the guide plate 4 and circulates inside and outside the hood plate 8, while the outside air taken in from the intake hole 51 at the bottom of the guide plate passes through the gap between the guide plate 4 and the bottom part 12 to the exhaust holes 52, 5□. A cold air circulation path is formed in which the air is discharged into the atmosphere.

Therefore, the lower surface of the printed board 18
to block the hot air from the fan 10, and to suppress the temperature rise on the lower surface of the printed board by removing residual heat remaining between the printed board and the guide plate 4 through the circulation of the mesh belt 15, and to suppress the temperature rise on the bottom surface of the printed board. Since the temperature rise is suppressed by constantly exchanging the air between the guide plate 4 and the printed board 18 with outside air, the temperature of the overhead area surrounded by the guide plate 4 and the printed board 18 is kept lower than the temperature above the printed board 18. It will be done. That is, the upper side of the printed board 18 is heated to about 150°C, while the lower side is maintained at 80 to 100°C. Therefore, as shown in FIG.
... is placed below the substrate 21, the temperature is increased to 150°C.
(It is ideally desirable for the discrete component 17 to be 80° C. or lower).

In this way, while the discrete components 17, 17... are temporarily installed, the chip components 16゜1 can be removed without thermal damage.
Exposing only the mounting surface of 6... to a high temperature of 150°C,
The adhesive is heated and cured to complete mounting of the chip component.

After that, the printed board 18 is taken out of the thermosetting furnace of the present invention,
In the next step, the terminals 19, 19 of the discrete component are further inverted (so that the terminals 19, 19 are on the lower side), and the terminals 19, 19 of the discrete component and the pattern wiring of the printed circuit board 21 are soldered using a solder bath device.

In addition, a far-infrared heater 13 is provided near the entrance 11 side of the furnace body 1 in order to improve the rise in temperature, and thereby the desired temperature difference between the top and bottom surfaces of the printed board 18 can be quickly achieved. It is configured to allow
It also makes it possible to adjust the temperature difference.

<Effects of the Invention> The present invention is configured as described above, and by making it possible to create a temperature difference between the top and bottom surfaces of the printed board, it is possible to maintain the temperature difference between the top and bottom surfaces of the printed board, even when the discrete components and chi-knob components are attached. It is now possible to heat-cure the adhesive for chip components, which eliminates the issue of mounting order and allows discrete components to be mounted first, allowing for high-density mounting of chip components and miniaturization of electronic devices. It can be promoted even more.

Furthermore, since the discrete components are mounted before the chip components are mounted, the clinching work of the terminals becomes easier and automation becomes easier.

Since the printed circuit board passes through the thermosetting furnace with the discrete components attached, the warpage of the printed circuit board caused by mounting the discrete components is corrected by heat, improving the yield of the product. In addition, since the mesh belt circulates in the opposite direction to the endless chain belt, even if the printed board should fall off from the chain belt, it will be carried out to the entrance side, and although it has a simple structure, work efficiency is significantly improved. It has many excellent effects, including the ability to improve

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of the main parts of the thermosetting furnace of the present invention, and FIG.
3 is an enlarged cutaway sectional view of the main part of FIG. 2, FIG. 4 is a side view showing an example of a printed board that can be processed by the thermosetting furnace of the present invention, and FIG. 1 is a side view of a printed board showing a conventional example. 1... Furnace body, 4... Guide plate 7...
Endless chain band, 8...Hood plate 9...Heater, 10...Fan 15...Mesh belt, 18...Printed board applicant Osaka Asahi Chemical Co., Ltd. 1J3"+= 115 Figure @ 4 Figure

Claims (1)

[Claims] Inside the heat-insulated furnace body, there is an endless chain belt for sequentially conveying printed boards from one side to the other, and a mesh belt below it that circulates parallel to the endless chain belt in the opposite direction to the endless chain belt. At the same time, a hood plate is provided in the upper space along the endless chain belt, a hot air guide plate is provided oppositely below the mesh belt, and a heater is interposed between the hood plate and the furnace main body. The hot air heated by the heater section is guided downward from the top of the hood board through the inside by a fan attached to the top of the hood board, and while being blown onto the printed board, the bottom of the hood board and the edge of the printed board are 1. A thermosetting furnace for fixing an adhesive for chip parts, characterized in that an airflow is generated that returns to the heater section through a space between the heater section and the heater section.