JP3349222B2 - Reflow furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflow furnace used for soldering electronic components to a circuit board.

[0002]

2. Description of the Related Art FIGS. 5 and 6 show the basic structure of a conventional reflow furnace. In the figure, 11 is a furnace body, 13 is a planar heater installed above and below the furnace body 11, 15 is a furnace inlet, 17 is a furnace outlet, and 19 is a furnace traveling from the inlet 15 to the outlet 17 in the furnace. The transport chain 21 is a rail that supports and guides the transport chain 19 traveling in the furnace from below.

[0006] Usually, there are two transfer chains 19 and two rails 21 as shown in FIG. Circuit board 23 on which electronic components (not shown) are mounted
Is supported by the transport chain 19 on both sides, and is heated by the sheet heater 13 from above and below while traveling in the furnace,
Heated to soldering temperature. The rail 21 is provided to prevent the transfer chain 19 from being slackened or rolled in the furnace, and to allow the circuit board 23 to be transferred without falling off at a certain height.

Since the width of the circuit board 23 varies depending on the type, the distance between the transport chain 19 and the rails 21 is
It is necessary to adjust according to the 23 types. For this rail
Both ends of the support 21 are supported by an end support 25, and the distance can be adjusted by laterally moving the end support 25. The transport chain 19 moves laterally with the rail 21.

[0005]

Since the linearity of the rail is accurate, if only both ends of the rail are supported and the distance between the both ends is adjusted to a desired distance, the distance between the rails is reduced. It is constant over the entire length (high parallelism is obtained). The distance between the transport chains is accordingly constant. However, in a structure that supports only both ends of the rail, the rail is bent, and it is difficult to keep the height of the circuit board constant.

In order to prevent the rail from bending, as shown by the dotted line in FIG.
It is desirable to install 27, but the intermediate support 27
The problem arises that even if the distance between the rails is precisely adjusted at both ends, the distance between the intermediate parts of the rails cannot be set accurately due to friction between the rail and the intermediate support.

[0007]

SUMMARY OF THE INVENTION The present invention provides a reflow furnace which solves the above-mentioned problems. The reflow furnace comprises a plurality of conveyors running in the furnace while supporting both sides of a circuit board. In a reflow furnace comprising a chain and a plurality of rails for guiding a transport chain traveling in the furnace, wherein the plurality of rails are supported at both ends so as to be adjustable in distance,
An intermediate support for supporting the intermediate portion of the rail from below is provided, and a moving mechanism for installing the intermediate support at a rail support position and at a standby position separated downward from the rail is provided.

[0008]

The intermediate support is set at the standby position when adjusting the distance between the rails. In this state, since the rail and the intermediate support are not in contact with each other, the distance between the rails can be set to be constant over the entire length by adjusting the distance between both ends of the rail. When the adjustment of the rail interval is completed, the intermediate support is installed at the rail support position. Then, since the rail is supported at the intermediate portion, the rail hardly bends. For this reason, the rails are maintained at a constant interval with almost no bending.

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings. 1 to 3 show an embodiment of the present invention. In the figure, 11 is a furnace body, 19 is a transport chain, 21 is a rail, and 23 is a circuit board on which electronic components are mounted. The illustration of the planar heater is omitted. Further, the rail 21 is supported at both ends so that the distance can be adjusted as in the conventional case.

The reflow furnace has an intermediate support 27 for supporting an intermediate portion of the rail 21. The intermediate support 27 is in the form of a cylindrical or cylindrical roll, and both ends thereof are rotatably supported by the distal ends of a pair of arms 29.
The base end of the arm 29 is fixed to a shaft 31 parallel to the intermediate support 27. The shaft 31 includes a bracket 33 installed in the furnace,
It is horizontally and rotatably supported by a bearing 35 that penetrates the furnace body 11, and one end thereof projects outside the furnace.

One end of a link 37 is fixed to a portion of the shaft 31 protruding outside the furnace. A movable end side of an actuator 39 such as a hydraulic cylinder is rotatably connected to the other end of the link 37 by a shaft pin 41. The fixed end side of the actuator 39 is rotatably connected to a support bracket 45 fixed to the furnace body 11 by a shaft pin 43.

The state shown in the figure is a state in which the actuator 39 is contracted and the intermediate support 27 is installed at the rail support position. The intermediate support 27 supports the intermediate portion of the rail 21 at the same height as both ends when in the rail support position.
Therefore, the rail 21 is hardly bent, and the transport chain 19 travels at a certain height. In addition, since the intermediate support 27 can be rotated like a roll, the intermediate support 27 can easily cope with the expansion and contraction of the rail 21 that occurs when the furnace temperature rises and falls.

Further, when heating of a circuit board of a certain size is completed and then heating of a circuit board of another size is performed, the distance between the rails 21 is adjusted as follows. First, the actuator 39 is extended from the state shown in the figure to move the intermediate support 27 to the standby position. Since the link 37, the shaft 35 and the arm 29 are integral, when the actuator 39 is extended, the link 37 and the arm 29 rotate to the position indicated by the two-dot chain line in FIG. Come to the standby position. In this state, the gap is adjusted at both ends of the rail 21 in the same manner as in the related art. At this time, since the middle portion is free, if the gap between both ends is accurately adjusted, the rails 21 have the same spacing over the entire length. Thereafter, the actuator 39 is contracted to return the intermediate support 27 to the rail support position.
This completes the interval adjustment of the rail 21. Transport chain 19
Is interlocked with the rail 21, so that it has the same interval as the rail 19.

FIG. 4 shows another embodiment of the present invention. In this embodiment, a ball support 49 for rotatably supporting a ball 47 is attached to the lower surface of an intermediate portion of the rail 21, and a plate-like intermediate support 27 is moved by a moving mechanism (not shown) to a rail support position (solid line) and a standby position. It is designed to be installed at a position (two-dot chain line). Even in this case, the same effect as in the above embodiment can be obtained.

In the above embodiment, the case where the intermediate support and its moving mechanism are provided at one place has been described. However, the intermediate support and its moving mechanism are installed at a plurality of places at intervals in the longitudinal direction of the rail. You can also. Also, the number of rails and transport chains can be three or more.

[0016]

As described above, according to the present invention, the bending of the rail can be almost eliminated by installing the intermediate support at the rail support position, and the intermediate support is moved to the standby position when adjusting the distance between the rails. By adjusting the distance between the rails, the distance between the rails can be accurately adjusted. For this reason, the height of the transfer chain traveling in the furnace becomes constant, the circuit board can be heated with an accurate temperature profile, and the distance between the transfer chains becomes constant, so that there is no possibility that the circuit board falls off the transfer chain. .

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an intermediate portion in a longitudinal direction of a reflow furnace according to one embodiment of the present invention.

FIG. 2 is a left side view of the reflow furnace of FIG.

FIG. 3 is a sectional view taken along line AA of FIG. 1;

FIG. 4 is a side view of a main part showing another embodiment of the present invention.

FIG. 5 is a longitudinal sectional view showing a basic configuration of a conventional reflow furnace.

FIG. 6 is a cross-sectional view of the reflow furnace of FIG.

[Explanation of symbols]

 11: Furnace 13: Planar heater 19: Transport chain 21: Rail 23: Circuit board 25: End support 27: Intermediate support 29: Arm 31: Axis 37: Link 39: Actuator

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H05K 3/34 B23K 1/008

Claims (1)

(57) [Claims] The present invention comprises a plurality of transport chains that travel in a furnace while supporting both sides of a circuit board, and a plurality of rails that guide the transport chains that travel in the furnace. In a reflow furnace supported at an adjustable interval, an intermediate support for supporting the intermediate portion of the rail from below is provided, and the intermediate support is connected to the intermediate portion of the rail.
A moving mechanism is installed at a rail support position for supporting the rails at the same height as both ends, and a standby position separated downward from the rails.
At the machine position, adjust the gap at both ends of the rail, and
After adjusting the distance between the rails, move the intermediate support to the rail support position.
A reflow furnace, which is installed to support an intermediate portion of a rail at the same height as both end portions .