JPH034055Y2 - - Google Patents

Description

[Detailed description of the invention] A. Field of industrial application The present invention relates to a printed circuit board heating device, for example,
This invention relates to printed circuit board heating devices for thick film integrated circuits used in various electrical equipment, home appliances, etc.

B. Prior art Thick film integrated circuits are suitable for mass production because they can easily automate production, and are inexpensive because they require less equipment costs.Furthermore, compared to thin film integrated circuits, it is easier to change circuit patterns, making it possible to produce a wide variety of products in small quantities. Because it has various advantages such as being suitable for use in various applications, it is widely used mainly in electrical equipment, home appliances, and the like.

The thick film integrated circuit (hereinafter sometimes simply referred to as a thick film circuit) is manufactured as follows. That is, various thick film pastes (thick film resistor paste, thick film conductor paste, etc.) are manufactured by mixing powders of metals, metal oxides, glass, etc. with organic binders, solvents, etc., and these thick film pastes are applied to ceramic substrates. A predetermined circuit pattern is formed by screen printing at a predetermined position on the top, and after drying, it is fired at 500°C to 1000°C.

Recently, in order to spatially increase the degree of circuit integration in the thick-film circuits mentioned above, thick-film circuits are increasingly being provided on both sides of a ceramic substrate (since then, thick-film circuits have been installed on both sides of the substrate). Those provided on both sides are called double-sided thick film circuits, and those provided only on one side are called single-sided thick film circuits.)

In order to bake such thick film circuits, a board on which a predetermined circuit pattern has been formed by printing thick film paste (hereinafter referred to as a printed board) is placed on a mesh belt conveyor and transported into a heating furnace. , heat treatment is performed under predetermined temperature and time conditions.
However, since the above baking is performed at a high temperature of 500℃ to 1000℃, the contact area between the printed circuit board and the mesh belt conveyor must be made as small as possible.
Naturally, it is also necessary to prevent the part of the printed circuit board where the thick film paste is printed (hereinafter referred to as the printed part) from coming into direct contact with the mesh belt conveyor. For the above reasons, a method as shown in FIG. 9 or FIG. 10 has been conventionally used.

FIG. 9a is a plan view showing the double-sided printed circuit board 2 placed on a tray 15 having four through holes 15a, and FIG. 9b is a sectional view taken along the line bb in FIG. 9a. .

A double-sided printed circuit board 2 is placed on each of the four through holes 15a of a metal tray 15 placed on a mesh belt conveyor 3. A portion 2a on which thick film paste is not printed (hereinafter referred to as a non-printed portion) is provided in advance on the peripheral edge of the printing board 2, and a portion 2a on which thick film paste is not printed is provided on the peripheral edge 15b surrounding the through hole 15a of the tray 15. Non-printing part 2a of printed circuit board 2
is placed. As a result, the printing section 2b provided on the printed circuit board 2 does not come into direct contact with the mesh belt conveyor 3 etc. during heating and conveyance.
It is heated from above and through the through hole 15a under predetermined conditions and fired.

FIG. 10a is a plan view showing a state in which the double-sided printed circuit board 2 is supported by the mesh belt 18 provided with chevron-shaped convex portions 16 and 17 in advance, and FIG. FIG.

The metal protrusions 16 and 17 are each fixed at a predetermined position on the mesh belt 18 by welding. In the drawing, the protrusion 16 on the right side and the protrusion 17 on the left side are provided facing each other, and two adjacent protrusions 16 and two protrusions 1 opposite to each other are provided.
7 and one printed circuit board 2 is supported. At this time, the opposing distance p between the convex parts 16 and 17 is made slightly smaller than the length q of the printed circuit board 2, and the printed circuit board is supported by placing one side 2a of the printed circuit board 2 at the end of the convex part 16. The other side 2b facing this is placed on the inclined surface 17a of the convex portion 17. Even with this method, the printed portion provided on the substrate 2 does not come into direct contact with the mesh belt conveyor 18 or the like during heating and conveyance.

As a result of study, the present inventor found that the above-mentioned method has the following problems.

(1) When using the tray 15 shown in FIG. 9, supply and align the tray 15 to a predetermined position on the mesh belt conveyor 3,
After the heating treatment is completed, operations such as returning the tray 15 to a predetermined position and aligning the tray 15 are required. Moreover, when firing double-sided printed circuit boards,
A peripheral portion 15b surrounding the hole 15a of the tray 15
It is necessary to place the non-printing part 2a of the printed circuit board 2 on top of the tray 15 so that the printing part 2b and the tray 15 do not come into contact with each other. Special consideration is required for positioning and the like when placing 2 on the tray 15.

For these reasons, separate auxiliary equipment is required, and the automatic control of the process is also complicated, resulting in high costs for automating the heating device and ultimately requiring a large investment in equipment.

(2) As shown in Figure 10, the convex part 1 of the mountain part
When using a mesh belt 18 provided with mesh belts 6 and 17, it is necessary to weld and fix a large number of metal protrusions to predetermined positions of a commonly used standard mesh belt 3. however,
The wires that make up the convex parts and the mesh belt have a small diameter, so the welding area is small, and welding work is technically difficult and has low reliability. Many problems occurred due to defects. Moreover,
If the protrusions are used for a long period of time, they will deform and oxidize, and will no longer function normally, causing trouble, so maintenance costs are required to avoid this.

(3) Since both the tray and the protrusion are made of metal, an oxide film will form when heated. When a tray is used, the tray and the printed circuit board come into direct contact, so that an oxide film adheres to the printed circuit board, degrading quality, and the oxide film scatters, adversely affecting the printing section. Moreover, the relatively large contact area was also a problem.

In addition, when using a convex part, the convex part and the printed circuit board,
Because the printed circuit board and the mesh belt conveyor are both in direct contact, problems similar to those described above have arisen.

Furthermore, in any of the above cases, undesirable oxide film dust is generated due to the sliding of the contact area between the printing board and the metal during conveyance by the mesh belt conveyor and during heating, and is agitated by convection in the furnace, causing the printing to deteriorate. It adheres to the printed parts of the circuit board and has an adverse effect. However, since the trays and convex parts of the mesh belt conveyor are in contact with or are located very close to the printed circuit board, care must be taken to prevent the oxide film generated during heating from contaminating the printed circuit board during the next heat treatment. Although it is necessary to remove the oxide film by cleaning, it is extremely difficult to remove the oxide film almost completely.

In addition, as a method other than the above, there is
There is one described in Publication No. 260191. The gist is that sub-mesh belts with finer meshes are attached at intervals on a mesh belt conveyor to form convex parts, and the non-printed part formed on one side of the double-sided printed board is placed directly on the mesh belt conveyor. Another non-printing part formed on the other side opposite to one side is placed on the sub-mesh belt, which is a convex part, so that the printing part on the lower surface of the double-sided printing board does not come into contact with the mesh belt.

However, according to this method, since the surface area of the submesh belt is extremely large compared to, for example, a chevron-shaped convex portion, an extremely large amount of oxide film is generated during heating, and moreover, the oxide film is in contact with the printed circuit board. Therefore, the problems already mentioned in (3), such as adhesion of the oxide film to the printed circuit board, scattering to the printed area, and generation of dust from the oxide film due to sliding, become even worse. Moreover, since the mesh is fine and a large amount of oxide film is generated, cleaning is time-consuming. Furthermore, since the sub-mesh belt with a fine mesh is woven and fixed at various locations on the spiral wire of the mesh belt of the main body, it is time-consuming and expensive.

Of course, the above applies not only to the firing of double-sided thick film circuits but also to the firing of single-sided thick film circuits.

A printed circuit board heating device that solves the above problems has not yet been proposed or known.

C. Purpose of the invention The purpose of the invention is to improve quality by eliminating negative effects such as adhesion of metal oxide films to printed circuit boards;
The process is easy to automate and does not require any incidental equipment.
Another object of the present invention is to provide a printed circuit board heating device that is easy to manufacture, highly reliable, and durable for long-term use.

D. Structure of the invention The present invention is configured such that a printed circuit board placed on a mesh belt conveyor is inserted into a heating furnace to heat the printed circuit board, and the printed circuit board is placed on the mesh belt conveyor. A plurality of small ceramic pieces to be placed so as not to touch each other are attached to the mesh belt conveyor at predetermined intervals, and the plurality of small ceramic pieces are arranged at a distance from each other so as to place each printed circuit board. This relates to a printed circuit board heating device.

E. Examples The present invention will be specifically explained below using examples.

FIG. 2 shows a printed circuit board mounting device attached to a mesh belt conveyor, in which FIG. 2A is a front view and FIG. 2B is a plan view.

The printed circuit board mounting device 1 is made of alumina (quartz or other ceramics are also possible), and has a truncated conical mounting portion 1d on the upper side of the disc-shaped main body 1c, and a disc-shaped locking portion on the lower side. 1a, which together constitute the printed circuit board mounting tool 1. An annular groove 1b is provided in the portion of the locking portion 1a that contacts the main body 1c.
is provided. In the figure, 1e is an outer peripheral inclined surface of the mounting portion 1d.

FIG. 1 shows a mesh belt conveyor, with FIG. 1A being an enlarged partial plan view and FIG. 1B being an enlarged partial schematic side view.

The mesh belt 3 is made up of tension bone wires 3b stretched at a constant distance from each other, and a spiral wire 3a wound in a flat spiral shape at a constant pitch between the tension bone wires. It is a commonly used type.

The printed circuit board mounting tool 1 is fitted into the mesh belt 3 in the following manner.

The diameter d ₁ of the locking part 1a of the printed circuit board mounting tool 1 is slightly larger than the width l of the gap 3c of the spiral wire 3a, and the diameter d ₂ of the annular groove 1b is larger than the width l of the gap 3c. It has also been made slightly smaller. For example, l=
When the diameter is 9.4 mm, the diameter d ₂ of the annular groove 1b is 0.6 mm smaller than l, and the outer diameter d ₁ of the locking portion 1a is 10 mm.

When the locking portion 1a of the printed circuit board mounting tool 1 is pressed against the gap 3c of the spiral wire 3a of the mesh belt 3 and a slight force is applied, the outer diameter d ₁ of the locking portion 1a changes to the gap 3c of the wire 3a. Since the wire 3a is slightly larger than the width l, the wire 3a is elastically deformed, and the gap 3c is temporarily expanded to the left and right in the drawing, and as a result, the locking part 1a of the printed circuit board mounting tool 1 becomes As shown, it is inserted into the mesh belt 3 through the gap 3c. When the annular groove 1b of the locking part 1a comes to the position of the wire 3a, the wire 3a, which had been elastically deformed, returns to its original position, fits into the annular groove 3b, and pinches it from the left and right to position the printed circuit board 1. be done. At this time, as mentioned above, the diameter of the annular groove 1b
Since d ₂ is 0.6 mm smaller than the width l of the gap 3c, the printed circuit board mounting tool 1 can be properly positioned with a slight play, and the diameter d ₁ of the locking part 1a
Since the width l of the gap 3c is slightly larger than the width l of the gap 3c, the printed circuit board mounting tool 1 does not come off the mesh belt 3 when the mesh belt conveyor 3 is driven, and the mesh belt 3
This does not prevent the pulley from curving to follow the outer circumference of the pulley. Further, by twisting and pulling the substrate mounting tool 1, it can be removed at any time.

FIG. 3a shows the mesh belt 3 being fitted into the
A plan view showing a state in which a double-sided printed circuit board 2 is placed on the attached printed circuit board mounting tool 1, and FIG.

In addition, the mesh belt conveyor 3 shown in FIGS. 3, 9, and 10, as well as FIGS. 6 and 8 described below.
In each case, the structure in FIG. 1 is simply shown by replacing it with a number of straight lines that are orthogonal to each other.

Three printed circuit board mounting devices 1 were installed in a row at regular intervals perpendicular to the traveling direction of the mesh belt conveyor 3 shown by the arrow, and these were repeatedly installed in the horizontal direction in the drawing. The attachment method is as described above, and in FIG. 3B, the locking portion 1a and the annular groove 1b of the printed circuit board mounting tool 1 are omitted from illustration.

The printed circuit board mounting devices 1 are arranged in two rows, that is, in a set of six, and support two printed circuit boards 2. The distance r between the mounting portions 1d of adjacent printed circuit board mounting tools 1 is made slightly smaller than the length q of the printed circuit board 2 supported thereby. The non-printing part 2a on one side 2c side of is brought into contact with the base of the placing part 1d, and the other side 2d facing this is brought into contact with the inclined surface 1 of the placing part 1d.
Place it on top of e. In this way, the printed circuit board 2 is supported without coming into contact with the mesh belt 3 and separated from it at a constant distance.

FIG. 4 is a schematic cross-sectional view showing the printed circuit board heating device 4. FIG.

The printed circuit board heating device 4 consists of a tunnel-shaped box-shaped heating furnace 5 and a mesh belt conveyor 3.

The inner wall of the heating furnace 5, except for the opening 5a, is covered with a heat insulating material 7, and inside the heating furnace 5 are provided above and below the mesh belt conveyor 3 in order to heat and bake both sides of the printed circuit board at the same time. , a planar infrared heater 6 is provided.

The mesh belt conveyor 3 has an endless shape and includes two pulleys 8 and a driving rotor 1.
0 and 2 driven pulleys 9. The conveyor 3 is driven by driving a drive rotor 10 with an electric motor 11.

As shown in FIG. 3, a large number of substrate mounting tools 1 are fitted and attached to the mesh belt conveyor 3 at predetermined positions. The double-sided printed circuit board 2 that has undergone the drying process is supported by the printed circuit board mount 1 as described above, and heated at 850°C to 900°C while being isolated from metal such as the conveyor 3 at a predetermined distance.
The thick film circuit is continuously charged into a tunnel-shaped box-shaped heating furnace 5 that is heated to ℃, and both sides are simultaneously heated by infrared heaters 6 installed above and below the furnace, the thick film circuit undergoes a firing process, and is discharged outside the furnace. be done.

Note that the driven pulley 9, which is in contact with the surface of the mesh belt conveyor 3, has a cutout groove (not shown) formed in the part through which the printed circuit board mounting tool 1 should pass; It fits into the groove, and also passes through the notched groove when the conveyor 3 is being driven.

The printed circuit board heating device as described above provides the following effects.

(1) Since the printed circuit board 2 is supported by a plurality of ceramic printed circuit board mounting tools 1, the printed circuit board 2 does not come into contact with metal, and the printed circuit board 2 and the mesh belt 3 are free from oxidation and generation. They are separated at a predetermined distance via a dust-free ceramic printed circuit board holder 1.

Therefore, during heat treatment, the oxide film forms on the printed substrate 2.
There is no possibility that the printed circuit board 2 and metal (conveyor, tray, etc.) No undesirable oxide film dust is generated due to sliding.

This significantly improves the quality of thick film circuits, prevents performance degradation, and improves product yield.

(2) Since no tray is used, the complicated process described in the prior art section is not required, the device can be easily automated, and separate incidental equipment is not required, resulting in low capital investment costs.

(3) Since the metal protrusion for supporting the printed circuit board is not attached to the mesh belt by welding or other methods, there are problems such as technical difficulties due to the small welding area, low reliability, and troubles due to poor welding. It doesn't happen. Furthermore, ceramics are extremely resistant to oxidation, abrasion, deformation, etc., so their functionality remains unchanged even after long-term use. There is no need.

(4) Unlike special methods of making mesh belts, such as attaching a metal protrusion to a mesh belt by welding or attaching a fine-mesh sub-mesh belt to the mesh belt of the main body, pre-prepared printing on a standard mesh belt Equipment costs are low because all you have to do is fit and install the board holder.

For the reasons described in (2) to (4) above, production costs can be significantly reduced.

(5) As shown in FIG. 1, the printed circuit board mounting tool 1 has a locking part 1a and an annular groove 1b, and
As shown in the figure, simply insert the tip 1a into the mesh belt and insert the helical wire into the annular groove 1.
b can be fixed, it is extremely easy to attach the printed circuit board mounting tool 1 to the mesh belt.

Further, as described above, the printed circuit board mounting tool 1 is properly positioned on the mesh belt conveyor with a slight play, and there is no misalignment. 3, the printed circuit board mounting tool 1 will not come off and the operation will not be adversely affected.

(6) As mentioned above, the printed circuit board mounting device can be attached and detached with a simple operation, so the mounting position on the mesh belt conveyor can be easily changed according to the dimensions of the printed circuit board to be fired. . Therefore, printed circuit boards of various sizes can be fired using the same device and the same mesh belt conveyor.

Note that only the driven pulley 9 shown in FIG. 4 may be replaced in accordance with the change in the mounting position of the printed circuit board mounting tool.

(7) As shown in Figure 1, printed circuit board mounting tool 1
A truncated conical mounting portion 1d having an inclined surface 1e is provided at the top, and as shown in FIG. 3, the printed board 2 is supported at an angle, so that the contact area between the printed board and the printed board mounting tool is It is small, allows for a wide printing section, and is stable in support, so that the printing section will not be affected by the printing board shifting laterally when a conveyor is driven.

FIG. 5 is a front view showing another printed circuit board mounting tool.

The printed circuit board mounting device 12 is made of ceramics, and a conical mounting portion 12d with a slightly rounded top 12e is provided on the upper side of the disc-shaped main body 12c, and a disc-shaped connector is provided on the lower side. A stop portion 12a is provided, and these parts together constitute the printed circuit board mounting tool 12. An annular groove 12b is provided in a portion of the locking portion 12a that contacts the main body 12c.

FIG. 6 is a sectional view showing a state in which the single-sided printed board 20 is placed on the printed board mounting tool 12 which is fitted and attached to the mesh belt 3. As shown in FIG.

The printed circuit board mounting tool 12 has a locking portion 12a and an annular groove 12b, as described above in detail using FIG.
It is attached to the mesh belt 3 by. The unprinted back surface 20a of the single-sided printed circuit board 20 is placed on the top 12e of the conical placement portion 12d,
As a result, the single-sided printed circuit board 20 is placed on the printed circuit board mounting tool 1.
2 and thus mesh belt 3
separated at regular intervals.

Even with this method, the effects (1) to (7) described above can almost be achieved. Note that a double-sided printed circuit board 2 may be supported instead of the single-sided printed circuit board 20, and in this case, the non-printed portion of the printed circuit board 2 is placed on the top 12e of the conical mounting portion 12d. Good.

FIG. 7 is a front view showing still another printed circuit board mounting tool 13.

The printed circuit board mounting tool 13 is made of ceramics, and has a conical shape whose slope becomes gentler as it approaches the hem.
A disc-shaped locking portion 13a is provided on the lower side of c, and an annular groove 13b is provided in the portion of the locking portion 13a that comes into contact with the main body 13c. It consists of In the figure, 13d is the outer peripheral inclined surface of the main body 13c.

FIG. 8 is a sectional view showing a state in which the double-sided printed circuit board 2 is placed on the printed circuit board mounting tool 13 that is fitted and attached to the mesh belt 3. As shown in FIG.

The printed circuit board holder 13 is attached to the mesh belt 3 by the locking portion 13a and the annular groove 13b, as described in detail above. A non-printing portion provided at the peripheral edge of the printed circuit board 2 is placed in contact with the outer circumferential inclined surface 13d of the main body 13c, so that the printed circuit board 2 is supported substantially horizontally on the printed circuit board mounting tool 13. and is separated from the mesh belt 3 at a constant distance. Main body 13c of printed circuit board mounting tool 13
The printed circuit board 2 has a conical shape with a gentle slope toward the bottom, so that the printed circuit board 2 remains almost horizontal and does not tilt excessively even during transportation or when external vibrations are applied to the device. do not have.

This method also achieves the effects (1) to (7) described above.

Note that the embodiments of the present invention are not limited to those described above, and various modifications can be made according to the technical idea of the present invention.

In the above-mentioned embodiment, the printed circuit board mounting tool (a small ceramic piece) was provided with a locking portion and an annular groove to be detachably attached to the mesh belt conveyor, but it could also be attached by other appropriate means. Also good. For example, the printed circuit board holder may be attached to the mesh belt with a locking wire. Further, the connecting portion of the printed circuit board mounting device may be mushroom-shaped, or may be shaped like a pair of doglegs or a fishhook. Further, the printed circuit board mounting device is not limited to one that is detachable, and may be fixed by, for example, a mesh belt with a locking portion woven into it.

The shape and structure of the printed circuit board mounting tool can also be changed as appropriate. For example, it does not necessarily have to be integrated, and may be a combination of two or more parts.

The shape, weaving method, etc. of the mesh belt used in the present invention may vary, and the shape, structure, attachment method, etc. of the printed circuit board mounting device may be selected accordingly. The structure of the heating furnace may also vary. The shape of the printed circuit board may be varied, and the method of supporting the printed circuit board, the number of printed circuit boards required for support, etc. may also be changed.

The ceramics used in the present invention are non-metallic inorganic solid materials, such as alumina and quartz, that are generally produced by heat treatment.

F. Effects of the Invention As explained above, the present invention involves attaching a plurality of ceramic pieces to a mesh belt conveyor at predetermined intervals, and separating each printed circuit board to be heated from each other so as not to touch the mesh belt conveyor. Since it is placed on the small piece, the following effects can be achieved.

(1) The printed circuit board is reliably separated from the mesh belt conveyor, and since there are no metal parts that touch or are located very close to the printed circuit board, metal oxides will not come into contact with the printed circuit board during heating. ,
Contamination of printed circuit boards with metal oxides is prevented,
Both quality and yield are high.

(2) The above-mentioned small pieces are made of ceramics, which are chemically stable and have excellent heat resistance and abrasion resistance, so they will not oxidize and react with the printed circuit board.
There is no need to perform cleaning to remove the oxide film, which improves labor productivity, and it can withstand repeated use over a long period of time, greatly improving the durability of the printed circuit board heating device.

(3) Since a standard mesh belt conveyor can be used without using a complicated and special conveyor, the initial cost is low, no trouble occurs during use, and maintenance costs are low. In addition, there is no need to use a tray, so there is no need for troublesome positioning of the printed circuit board on the tray or troublesome cleaning of the tray, and there is no need for incidental equipment for returning the tray, making automation easy.

[Brief explanation of the drawing]

Figures 1 to 8 show an embodiment of the present invention, in which Figure 1 shows a mesh belt conveyor, Figure a is an enlarged partial plan view, Figure b is an enlarged partial schematic side view, Figure 2 shows a printed circuit board mounting tool, Figure a is an enlarged front view, Figure b is an enlarged plan view, Figure 3 shows a mesh belt conveyor on which printed circuit boards are placed, Figure A is a plan view. Figure, b of the same figure is b- of the same figure a.
4 is a cross-sectional view of the printed circuit board heating device, FIG. 5 is an enlarged front view of another printed circuit board mounting device, and FIG. 6 is the printed circuit board mounting device of FIG. 5. 7 is an enlarged front view of another printed circuit board mounting device, and FIG. 8 is the printed circuit board mounting device shown in FIG. 7. FIG. 2 is a cross-sectional view showing a state in which a printed circuit board is placed on a mesh belt conveyor using a mesh belt conveyor. 9 and 10 show conventional examples.
Figures a and 10a are plan views showing the printed circuit board placed on the mesh belt conveyor, and figure 9.
Figure b is a sectional view taken along line bb in Figure 9a,
FIG. 0b is a sectional view taken along the line b-Xb in FIG. 10a. In addition, in the symbols shown in the drawings, 1, 1
2, 13...Printed board mounting tool, 1a, 12a, 1
3a... Locking part, 1b, 12b, 13b... Annular groove, 1c, 12c... Main body, 1d, 12d, 13
c... mounting section, 2, 20... printed circuit board, 3... mesh belt conveyor, 4... printed board heating device, 5... heating furnace.

Claims (1)

[Scope of utility model registration request] The printed circuit board placed on the mesh belt conveyor is inserted into a heating furnace to heat the printed circuit board, and the plurality of printed circuit boards are placed so as not to touch the mesh belt conveyor. A printed circuit board heating device, wherein small pieces of ceramic are attached to the mesh belt conveyor at predetermined intervals, and a plurality of the small pieces of ceramic are arranged at a distance from each other so as to place each printed circuit board.