JPH087656Y2 - Reflow furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a reflow oven for heating and soldering a printed circuit board coated with cream solder.

[Conventional technology]

In general, infrared heaters are installed above and below the tunnel in the reflow oven.The infrared solder heater heats the printed circuit board while it is being conveyed by a conveyor running in the tunnel, melting the cream solder applied to the printed circuit board and printing it. The board and the electronic component are soldered together.

Since electronic devices have been downsized in recent years, electronic parts have been mounted at high density. When electronic components are mounted at high density, it is difficult for infrared rays that go straight ahead to reach the shadow of the electronic components, and the cream solder applied to the soldering portion may not be melted. on the other hand,
The electronic parts near the heater were sometimes overheated by receiving infrared rays, which could cause thermal damage.

Since heating by infrared rays alone causes non-uniform heating, many reflow furnaces have been proposed recently, which use infrared rays together with hot air or heat only with hot air.
The hot air makes the temperature distribution in the reflow furnace uniform and, at the same time, penetrates between the electronic components mounted at high density, and thus has the effect of locally preventing insufficient heating or overheating.

[Problems to be solved by the invention] By the way, cream solder is a mixture of liquid or pasty flux and powdered solder, and the flux contains solid components such as pine resin, thixotropic agent and activator such as alcohol and ether. It was dissolved in an organic solvent. Therefore, cream solder is at the soldering temperature
When heated above 200 ° C, solid components and organic solvents vaporize to form flux fumes, which fill the reflow furnace.
Some of them will go out of the reflow oven and cause discomfort to workers. The flux fumes adhere to any places such as tunnels and conveyors, but in the hot air circulation type reflow furnace, they further adhere to blowers and hot air passages, which deteriorates the rotation of the blower and deteriorates the ventilation.

The present invention is to provide a hot air circulation type reflow furnace in which flux fumes do not easily adhere.

[Means for solving the problem]

The present inventors have completed the present invention by paying attention to the fact that the catalytic effect is further increased by depositing a ceramic having a catalytic action on the porous metal body because the porous metal body has a large surface area. .

[Constitution of device]

The present invention is a reflow furnace for heating and soldering a printed circuit board with circulating hot air, characterized in that a composite material in which ceramics are adhered to the surface of a metal porous body is installed in a hot air passage. is there.

The deposition of ceramics on the porous metal body is obtained by spraying ceramics.

[Action]

Since the porous metal body has a large surface area, it easily adsorbs flux fumes. Further, the catalytic ceramics adhered to the surface of the porous fumed metal make the flux fumes smokeless and odorless.

Ceramics have a brittle property, but if they are welded to a porous metal body, they are less likely to be damaged.

〔Example〕

In the reflow furnace, a large number of infrared heaters 2 ... Are installed in the upper and lower portions of the tunnel 1, and a conveyer 3 that conveys a printed circuit board P runs in the direction of arrow A between the upper and lower heaters. A gas ejection port 4 and a gas recovery port 5 are installed at positions different from the axial direction of the tunnel. The gas ejection port and the gas recovery port are led to the outside of the reflow furnace by a pipe 6 and connected to the flow device 7. The flow device is a device that causes gas to flow in one direction, and the flow velocity can be adjusted by adjusting the drive motor 8 of the flow device. A composite material 9 made of a metal porous body and a material having a catalytic action is installed in the gas recovery port 5 which is a hot air circulation passage. As shown in FIG. 2, the composite material is one in which ceramics 11 is sprayed on the surface of a porous metal body 10. The metal porous body used in the present invention is a material having corrosion resistance because the flux fumes are corrosive, for example, an alloy such as Ni-Cr,
A porous product (trade name: Celmet) is suitable. The ceramics are oxides of silicon, zircon, titanium, aluminum, etc., which were sprayed onto the surface of the metal porous body to obtain a composite material. Although the composite material is installed in the gas recovery port in the present embodiment, it may be installed in any place as long as it is a hot air passage, not limited to the gas recovery port. Further, in the embodiment, as the hot air reflow furnace, the one in which hot air is once outside the tunnel and then introduced again into the tunnel is shown, but the present invention is also applicable to a reflow furnace in which hot air circulates only inside the tunnel. It goes without saying that it can be adopted.

[Effect of device]

Since the reflow furnace of the present invention has a composite material composed of a metal porous body having a large surface area and ceramics having a catalytic action installed in the passage of hot air, it improves the adsorption of flux fumes and is smokeless and odorless. Therefore, even if the gas in the reflow furnace leaks to the outside, it does not cause discomfort to the operator, and flux fumes do not accumulate on the inside of the tunnel or the blower and adversely affect the printed circuit board. It has an excellent effect not found in

[Brief description of drawings]

FIG. 1 is a front sectional view of a reflow furnace of the present invention, and FIG. 2 is an enlarged sectional view of a composite material. 1 ... Tunnel, 2 ... Heater, 3 ... Conveyor, 4 ... Gas ejection port, 5 ... Gas recovery port, 6 ... Pipe, 7 ... Flow device, 8 ... Motor, 9 ... Composite material 10 ... … Porous metal, 11 …… Ceramics

Claims (1)

[Scope of utility model registration request] 1. A reflow oven for heating and soldering a printed circuit board with circulating hot air, wherein a composite material in which ceramics are adhered to the surface of a metal porous body is installed in a hot air passage. .