JPH03194995A - Method and apparatus for reflowing on both side surfaces - Google Patents

Abstract

PURPOSE:To prevent a recesslike deformation of a circuit board and to smoothly mount a component on a secondary surface similarly to a primary surface by executing a primary reflow by holding the board to become planar from its rear surface and executing a secondary reflow by holding the board at its end. CONSTITUTION:A circuit board is so held by a primary surface conveyor 9 having a flat part 11 in a primary reflow as to hold to become planar from its rear surface to prevent recesslike deformation of the board. Only both ends of the board are held by protrusions 12 at both ends of a secondary surface conveyor 10 in a secondary reflow to smoothly perform the secondary reflow without adverse influence to the primary surface.

Description

Detailed Description of the Invention [Field of Application in Industry A] The present invention relates to a method and apparatus for reflow soldering on both sides of an electronic circuit board in mounting the board, and particularly relates to a method and apparatus for holding the board. It is related to.

[Prior Art] Conventionally, in double-sided reflow, for example, as shown in FIG. 5, an end portion of a circuit board 2 on which electrical components 3 are mounted is held by a transport section 1, and reflow is performed. Both the primary reflow and the secondary reflow were normally performed by the same method. This was to avoid adversely affecting the primary surface having the electrical components 3 already mounted thereon during the secondary reflow.

[Problem to be solved by the invention] Normally, reflow is performed at a temperature of 200 to 260 t, 10 to
This is done by holding for 30 seconds. It is known that under such temperatures, the circuit board 2 of the electronic circuit softens and, together with the weight of the mounted electrical components 3, deforms into a concave shape as shown in FIG. Now, 120mm x 12
Taking the glue flow of a 0mm x 0.4mmt Gala Evo board as an example, this board is 2.5mm to 3mm thick by primary reflow as shown in Figure 5. It has been observed that it deforms into a concave shape below 0 mm. Further, as shown in FIG. 7, the perforations 6 of the board dividing grooves provided at the center of the electronic circuit board section 4 and near the board ends 5 are made larger than the concave shape shown in FIG. There is. That is, in the conventional technology, it becomes difficult to print solder paste on the secondary surface, making it difficult to mount with a mounter, and furthermore, the circuit board 2 is deformed during printing and mounting, and the circuit board 2 is not soldered to the primary surface. There were problems such as damage to electrical parts 3 and the like.

The present invention aims to solve the above problems. In other words, the present invention can prevent the circuit board from deforming into a concave shape, and as a result, component mounting on the secondary surface can be prevented.
It is an object of the present invention to provide a double-sided reflow method and an apparatus therefor that can be smoothly performed in the same way as for the primary surface.

[Means for Solving the Problems] In order to achieve the above object, the double-sided reflow method of the present invention provides a circuit board that is soldered by double-sided reflow, and in the first reflow, the circuit board is soldered from the back side into a planar shape. The second reflow was carried out by holding the circuit board at its edges. Further, the double-sided reflow apparatus of the present invention includes a primary surface transport section and a secondary surface transport section that transport circuit boards to be soldered by double-sided reflow, and the primary surface transport section includes , a means for holding the circuit board in a planar shape from the back side, and a means for holding the circuit board at an end in the secondary surface transfer section.

[Function] According to the present invention, by holding the circuit board flat from the back side during the primary surface adhesive flow, it is possible to prevent the circuit board from deforming into a concave shape. Therefore, components can be mounted on the secondary surface as smoothly as on the primary surface. In the secondary surface gluing flow, as usual, be careful not to touch the parts mounted on the primary surface.
Reflow is performed by holding the edge of the circuit board.

[Embodiment] FIG. 1 shows a first embodiment of the present invention, that is, it shows a conveying section of a double-sided reflow apparatus.

In FIG. 1, numeral 9 denotes a primary surface conveying section, which is composed of a flat surface section 11. As shown in FIG. Reference numeral 10 denotes a secondary surface conveying section, which has protrusions 12 only at both ends.

Therefore, in the primary reflow, the circuit board (not shown) is transported by the primary surface transport section 9 having the flat surface section 11.
Since the circuit board is held flat from the back side, the circuit board is prevented from being deformed into a concave shape. In addition, in the secondary reflow, only both ends of the circuit board are held by the protrusions 12 at both ends of the secondary surface transfer unit IO, so the secondary reflow is smooth without adversely affecting the primary surface. It will be held in

FIG. 2 shows the operating sequence of the apparatus shown in FIG.

Usually, a reflow apparatus has a circuit board transport section 7 and an air transport section 8 (interval), as shown in FIG. 8, and the interval between the circuit boards to be reflowed is sufficiently larger than the size of the circuit boards. However, as shown in FIG.
There is no problem in implementing the combination of the secondary surface transport section 10 and the transport section 10 for the secondary surface.

FIG. 3 shows a transport section of a double-sided reflow apparatus according to a second embodiment of the present invention.

In this second embodiment, the primary surface conveying section 9 has a large number of horizontal bars 13, and the secondary surface conveying section 10 is the same as that shown in FIG.

FIG. 4 shows a conveying section of a double-sided reflow apparatus according to a third embodiment of the present invention.

In this third embodiment, the primary surface conveying section 9 has a large number of wires 14, and the secondary surface conveying section 10 is the same as that shown in FIG.

In addition, in FIG. 3, a horizontal bar 13 is provided in the primary surface conveying section 9,
In FIG. 4, wires 14 are provided in the primary surface transfer section 9, and although these are not flat plates, they serve to hold the circuit board in a flat shape from the back side.

[Effects of the Invention] As explained above, according to the present invention, by holding the circuit board flat from the back side during the primary surface adhesive flow, it is possible to prevent the circuit board from deforming into a concave shape. Become. Therefore, not only can higher density and higher yield be expected on the secondary surface, but also the mounting quality on the primary surface can be improved. Furthermore, soldering on the secondary surface eliminates solder displacement and deterioration of the land.

[Brief explanation of drawings]

Fig. 1 is a perspective view showing a first embodiment of the device of the present invention, Fig. 2 is an explanatory diagram of the operating sequence of the device of Fig. 1, and Fig. 3 shows a second embodiment of the device of the present invention. FIG. 4 is a perspective view showing the third embodiment, FIG. 5 is a perspective view showing an example of the conventional technique, and FIG. 6 shows the state of deformation of the circuit board by the method shown in FIG. 7 is a plan view showing an example of a conventional circuit board, and FIG. 8 is an overall view of the reflow apparatus. 1...Transportation section 2...Circuit board 3...
Electrical parts 4...Electronic circuit board part 5...
Board end 6... Perforation 7... Board transfer section 8... Air transfer section 9... Primary surface transfer section
10...Conveyance part for secondary surface 11...Plane part
12...Protrusion 13...Horizontal bar 14...
Wire Figure 1 Figure 2 Figure 5 Figure 6 Figure 7 Figure 3

Claims (1)

[Claims] 1. In a circuit board to be soldered by double-sided reflow, the circuit board is held flat from the back side in the first reflow, and the circuit board is held flat in the second reflow. A double-sided reflow method characterized by holding at the edges. 2. A primary surface transporting section and a secondary surface transporting section are provided for transporting a circuit board to be soldered by double-sided reflow, and the primary surface transporting section is provided with a circuit board that is soldered from the back surface to a flat surface. A double-sided reflow apparatus, characterized in that the secondary surface transfer section has means for holding the circuit board at an end thereof.