JPH05123861A - Method for soldering circuit substrate in reflow furnace - Google Patents

Abstract

PURPOSE:To provide a soldering method for circuit substrate in a reflow furnace, in which the generation of warp in the circuit substrate can be prevented even in the case of mounting on both surfaces. CONSTITUTION:By inserting spacers 5 for floating a parts in between the circuit substrate 1 and an endless conveyor 4 at the position corresponding to the endless conveyor 4 for preventing the warp, the circuit substrate 1 is conveyed into the reflow furnace.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art When a component is soldered to a circuit board in a reflow furnace, the circuit board on which the component is to be soldered is usually mounted on a lower surface of a chain conveyor or the like on the lower surfaces of both ends in a direction orthogonal to the carrying direction. It is carried into the reflow furnace by being supported by the endless conveyor for the end. In this case, since the circuit board is supported by the endless conveyors for the end portions only on the lower surfaces of both ends in the direction orthogonal to the transport direction, the intermediate portion of the circuit board 1 is projected downward as shown in FIG. There was a problem that the center of the lower surface of the component 2 lying on the mold was lifted up by h and the soldering became impossible. In particular,
As part 2, a large size QFP (Quad Flat Pack)
This tendency is remarkable in the case of surface mounting four-way lead type packages and surface mounting connectors called age). According to the calculation, if a warp of 3 mm occurs on the circuit board 1 having a width of 200 mm, the lift h from the circuit board 1 at the center of the component 2 is 0.12
mm. The printed thickness of cream solder is 0.15 to 0.2 mm, so soldering becomes impossible if the lead is bent (lifted) or warped more.

Therefore, as shown in FIG. 4, a circuit board 1 to which a component is to be soldered is supported by endless endless conveyors 3 such as chain conveyors on the lower surfaces of both ends in a direction orthogonal to the carrying direction, and There has been proposed a method of soldering a circuit board in a reflow furnace in which a lower surface of an intermediate portion is supported by a warp-preventing endless conveyor 4 such as a wire conveyor or a chain conveyor and carried into the reflow furnace.

In this way, since the circuit board 1 to which the components are to be soldered is supported by the warp preventing endless conveyor 4 on the lower surface of the intermediate portion in the direction orthogonal to the carrying direction, the circuit board 1 is prevented from warping. can do.

[0005]

However, such a method of soldering a circuit board in a reflow furnace does not pose a problem in the case of single-sided mounting in which components are soldered only to the upper surface of the circuit board 1, but the circuit board is not problematic. In the case of double-sided mounting in which parts are soldered to both the upper and lower surfaces of 1, the side where the parts are soldered first faces downward, and then when the parts are soldered to the upper surface, the warp prevention endless conveyor 4 is used. There is a problem that components cannot be mounted on the lower surface of the circuit board 1 corresponding to the supporting portion. That is, when a component is mounted on the lower surface portion of the circuit board 1 corresponding to the portion supported by the warp prevention endless conveyor 4, the component is supported by the warp prevention endless conveyor 4, so the circuit board 1
The circuit board 1 itself is no longer supported by the warp prevention endless conveyor 4, and the warp prevention endless conveyor 4
Therefore, the circuit board 1 is warped.

It is an object of the present invention to provide a method of soldering a circuit board in a reflow furnace which can prevent the circuit board from warping even when it is mounted on both sides.

[0007]

Means for Solving the Problems To explain the means of the present invention for achieving the above object, the present invention is directed to the bottom surface of both ends of a circuit board to which a component is to be soldered in a direction orthogonal to its carrying direction. Of the circuit board in the reflow furnace, which is supported by the part endless conveyor, and supported by the warp prevention endless conveyor at the lower surface of the intermediate part and carried into the reflow furnace, and soldering the parts to the circuit board in the reflow furnace. In the soldering method, the circuit board is conveyed by interposing a component floating spacer between the circuit board and the warp prevention endless conveyor at a position corresponding to the warp prevention endless conveyor. .

[0008]

With this configuration, in the case of double-sided mounting, when the component is soldered first with the surface facing downward, and then when the component is soldered on the upper surface, the lower surface of the circuit board is placed through the component floating spacers. It will be supported by the warp prevention endless conveyor. Therefore, even if components are mounted on the lower surface of the circuit board corresponding to the warp prevention endless conveyor, the circuit board can be conveyed in the reflow furnace while preventing warpage.

[0009]

FIG. 1 and FIG. 2 show an embodiment of the present invention. In this embodiment, the component floating spacer 5 is attached to the lower surface of the circuit board 1 in advance at a position corresponding to the warp prevention endless conveyor 4 by adhesion or the like. The height of the component floating spacer 5 is set higher than the height of the component 2 attached to the lower surface of the circuit board 1 corresponding to the warp prevention endless conveyor 4. Along with this, the warp prevention endless conveyor 4 needs to be lowered downward by the height of the component floating spacers 5.

When such a circuit board 1 is used to place the illustrated components on the upper surface of the circuit substrate 1 and soldering with cream solder, as shown in FIG. 1, the lower surface of the circuit substrate 1 is the component. It is supported by the warp prevention endless conveyor 4 via the floating spacers 5. Therefore, even if the component 2 is mounted on the lower surface portion of the circuit board 1 corresponding to the warp prevention endless conveyor 4, the circuit board 1 can be transported in the reflow furnace while preventing warpage.

Therefore, the mountable area of the circuit board 1 can be greatly increased. Spacer 5 for floating parts
May be removed after the soldering is completed, or may be left as it is if it does not disturb the incorporation into the product.

[0012]

As described above, in the method of soldering a circuit board in a reflow furnace according to the present invention, parts are provided between the circuit board and the warp prevention endless conveyor at a position corresponding to the warp prevention endless conveyor. Since the circuit board is transported with the floating spacers interposed, in the case of double-sided mounting, the surface to which the component is soldered first faces downward, and then when the component is soldered to the upper surface, the lower surface of the circuit board Will be supported by the warp prevention endless conveyor via the component floating spacers, so even if components are mounted on the lower surface of the circuit board corresponding to the warp prevention endless conveyor, the circuit will be prevented while warping. The substrate can be transferred in a reflow oven. Therefore, according to the present invention, the mountable area of the circuit board can be significantly increased. In addition, it is possible to prevent the parts existing on the lower surface of the circuit board corresponding to the warp prevention endless conveyor from being damaged by the warp prevention endless conveyor.

[Brief description of drawings]

FIG. 1 is a side view of essential parts showing an example of an implementation state of a method for soldering a circuit board in a reflow furnace according to the present invention.

FIG. 2 is a bottom view of the circuit board according to this embodiment.

FIG. 3 is an explanatory diagram showing a warped state of a conventional circuit board.

FIG. 4 is a perspective view showing an implementation state of a method for soldering a circuit board in a conventional reflow furnace.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Circuit board, 2 ... Parts, 3 ... Endless conveyor for end parts, 4 ... Endless conveyor for warp prevention, 5 ... Spacers for floating parts.

Claims (1)

[Claims] 1. A circuit board to which a component is to be soldered is supported by endless endless conveyors on the lower surfaces of both ends in a direction orthogonal to the carrying direction, and the lower surface of an intermediate portion is supported by warp prevention endless conveyors. In a method of soldering a circuit board in a reflow furnace that carries in a reflow furnace and solders the component to the circuit board in the reflow furnace, the circuit board and the circuit board at a position corresponding to the warp prevention endless conveyor. A method of soldering a circuit board in a reflow furnace, characterized in that the circuit board is conveyed by interposing a spacer for floating a component between the warp prevention endless conveyor.