JP2009038401A - Automatic soldering equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that conventional automatic soldering equipment using an inert atmosphere is not capable of simultaneously reducing an oxygen concentration and rapidly cooling a printed substrate by a jet solder bath that requires an inert gas and a preheater portion, and to provide automatic soldering equipment capable of simultaneously reducing the oxygen concentration by the jet solder bath and preheater and performing rapid cooling by a cooling device. <P>SOLUTION: In the automatic soldering equipment according to the present invention, an exhaust system is installed adjacent to the entrance of the automatic soldering equipment, and an inert gas cooled to a low temperature is blown from the cooling device. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an automatic soldering apparatus for soldering a printed circuit board in an inert atmosphere.

  Processing apparatuses such as a fluxer, a pre-heater, a jet solder bath, and a cooling apparatus are installed in an automatic soldering apparatus for soldering a printed circuit board, and a conveyor of a transport device runs on these processing apparatuses.

  When the printed circuit board is soldered by this automatic soldering apparatus, the printed circuit board is held by the claws of the conveyor and then traveled on the processing apparatus, and the processing is performed by each processing apparatus to perform soldering.

  A printed circuit board that is driven by a conveyor is first fluxed onto the soldering surface of the printed circuit board by a fluxer. This flux application is performed by bringing the printed circuit board into contact with the flux foamed by the foaming tube or spraying the flux atomized by the spray nozzle onto the printed circuit board. The fluxer may be installed in the automatic soldering apparatus or may be installed outside the automatic soldering apparatus. When the fluxer is installed outside the automatic soldering apparatus, the automatic soldering apparatus solders the printed circuit board in an inert atmosphere intended by the present invention. The automatic soldering apparatus having an inert atmosphere is installed outside the automatic soldering apparatus because the chamber is contaminated by the flux when the fluxer is installed in a chamber that makes the fluxer an inert atmosphere.

  Next, the printed circuit board to which the flux is applied is preheated by a preheater. The reason why the printed circuit board on which the flux has been applied is preheated is that if the solvent remains in the flux, the molten solder will scatter when brought into contact with the next molten solder. This is because if the printed circuit board is brought into contact with the molten solder that has suddenly increased in temperature, the printed circuit board or the electronic components mounted on the printed circuit board will be damaged by heat shock, and the printed circuit board at room temperature will become a molten solder. This is because the temperature of the molten solder is lowered when contacted, and when the temperature of the printed circuit board is low, the solderability is deteriorated.

  The printed circuit board preheated by the preheater is conveyed to a jet solder bath, where it contacts the molten solder and is soldered. A jet solder bath for soldering printed circuit boards is provided with a primary jet nozzle for jetting rough waves and a secondary jet nozzle for jetting gentle waves. At the time of soldering, the printed circuit board first disperses the molten solder into the corners and through holes of the soldered portion by the rough wave of the primary jet nozzle to eliminate unsolder. Next, bridges, wiggles, etc. generated by soldering of the primary jet nozzle are corrected by the gentle waves of the secondary jet nozzle.

  Conventionally, solder used for soldering printed circuit boards was Pb-63Sn solder. Since this Pb-63Sn solder has a relatively low melting point, the temperature of the molten solder at the time of soldering can be lowered, or the soldering property is good, so there are few defects and it has the excellent feature that it is inexpensive. ing. However, when a printed circuit board soldered with Pb-63Sn solder is disposed of in landfill, and acid rain comes into contact with the landed printed circuit board, Pb in the solder is eluted and mixed into groundwater. And when humans and livestock drank groundwater containing Pb for many years, lead poisoning is caused, and the use of solder containing Pb has been regulated. For this reason, so-called lead-free solder that does not contain Pb has recently been used.

  The lead-free solder is composed of Sn as a main component, and Ag, Cu, Bi, Zn, In, Cr, Mo, Co, Fe, P, Ge, Ga, or the like is appropriately added thereto. Lead-free solder has poor solderability and is easily oxidized compared to conventional Pb-63Sn solder. If the solderability with respect to the printed circuit board is poor, soldering defects such as unsoldering, bridges, and dewetting occur. In addition, lead-free solder that easily oxidizes generates a large amount of oxide in the jet solder bath, and not only expensive lead-free solder is wasted, but the oxide adheres to the printed circuit board and deteriorates the appearance. It may cause a short circuit or a decrease in insulation resistance. The reason why lead-free solder is easily oxidized is that Sn, which is easy to oxidize, is the main component, and lead-free solder having a high melting point increases the soldering temperature, so that oxidation is further promoted.

  It has been found that when lead-free solder is used in an automatic soldering apparatus, soldering can be performed in an inert atmosphere in order to eliminate soldering defects and prevent solder oxidation. An automatic soldering device that performs soldering in an inert atmosphere (hereinafter referred to as an inert soldering device) covers a preheater, a jet solder bath, a cooling device, etc. with a chamber, and the chamber contains a non-nitrogenous material such as nitrogen. It is filled with active gas, and many have been proposed heretofore. (See Patent Documents 1 to 3)

  The conventional inert soldering apparatus is provided with a slope that increases from the inlet side to the outlet side, and an inflow port through which an inert gas flows into the chamber is installed above each processing apparatus. In this soldering apparatus, after the inert gas flowing into the chamber fills the chamber, it flows out from the outlet side. The inert gas flows out from the outlet side in this way because the conveyor of the transport device is inclined 3 to 5 degrees upward in the traveling direction, and the inert gas in the chamber is warmed by the preheater or the jet solder bath This is because the heated and lightened inert gas flows out of the outlet side at a high position due to the chimney effect of the chamber.

  When the inert gas in the chamber flows out from the outlet side due to the chimney effect, air enters the chamber from the inlet and the oxygen concentration in the chamber increases. In particular, the oxygen concentration in the vicinity of a pre-heater or a jet solder bath that requires a low oxygen concentration atmosphere is increased. In order to prevent such an increase in oxygen concentration due to the chimney effect, a soldering apparatus has been proposed in which an opening with a suction device is provided near the inlet, and an inert gas in the chamber is sucked from the opening. (See Patent Document 4)

Japanese Patent Laid-Open No. 5-200538 (Fig. 2 on page 5) Japanese Patent Laid-Open No. 5-355530 (page 2 on page 7) Japanese Patent Laid-Open No. 6-26555 (Fig. 1 on page 4) Japanese Patent Laid-Open No. 7-36951 (Fig. 1 on page 3)

  By the way, the inert soldering apparatus provided with the opening in the vicinity of the inlet can surely prevent the chimney effect and the outflow of the inert gas from the outlet side is eliminated. However, soldering equipment with an opening near the inlet does not have a sufficient decrease in oxygen concentration in pre-heaters and jet solder baths that require a decrease in oxygen concentration. As a result, when lead-free solder is used, Defects such as unsoldering and bridges at the soldering portion of the substrate could not be completely eliminated, and generation of oxides could not be sufficiently suppressed in the jet solder bath.

  In addition, in the conventional inert soldering device provided with an opening near the entrance, the cooling effect of the printed circuit board in the cooling device is not sufficient, and after soldering in the jet solder bath, cracks and cracks occur in the solder. was there. In the inert soldering apparatus, the oxygen concentration in the pre-heater section and the jet solder bath where the oxygen concentration needs to be reduced can be extremely reduced, and cracks and cracks can be generated after soldering in the jet solder bath. An object of the present invention is to provide a soldering apparatus that does not generate the above.

  As a result of earnest research on reducing the oxygen concentration in the pre-heater part and the jet solder tank part by utilizing the chimney effect preventing means used in the conventional inert soldering apparatus, the present inventor, The present invention has been completed by finding out that if the cooling device is used for inflow of inert gas, it is effective in lowering the oxygen concentration in the necessary portion and preventing cracking and cracking in the soldered portion.

  In the soldering apparatus of the present invention, a low-temperature inert gas is blown from the cooling device onto the soldering surface of the printed circuit board immediately after soldering in the jet solder bath, thereby rapidly cooling. When the soldering part immediately after soldering is rapidly cooled, the molten solder adhering to the printed circuit board rapidly solidifies, so that cracks and cracks do not occur even if vibration or impact is applied due to conveyance. Lead-free solder, in particular, has a high melting temperature, so it did not solidify quickly with conventional fan cooling, and cracks and cracks were often generated. These sprays can be prevented by spraying on the surface.

  In the present invention, if the cooling device is connected to the refrigerator, a low-temperature inert gas can be sprayed onto the printed circuit board immediately after soldering, so that the molten solder adhering to the printed circuit board can be quickly cooled and solidified. Therefore, since the inert soldering apparatus of the present invention can rapidly cool even a high melting point such as lead-free solder, it can prevent the occurrence of cracks and cracks and can improve the strength by making the solder structure fine.

  In other words, the inert solder bath of the present invention is configured so that the inert gas flowing out from the cooling device, which is the final processing device, flows in the inlet direction against the chimney effect, and the jet solder bath or preheater that requires the inert gas is oxygenated. In order to make the concentration low, there is no loss of appearance due to unsolder, oxide, short circuit, insulation resistance drop, loss of expensive lead-free solder, etc. Conventional inert soldering not only does not cause cracks and cracks, but also improves the mechanical strength by reducing the solder structure in order to rapidly solidify the solder attached to the printed circuit board by spraying onto the printed circuit board. It has an excellent effect not found in the apparatus.

  The present invention relates to an automatic soldering apparatus in which a preheater, a jet solder bath, and a cooling device are covered with a chamber, and the printed circuit board is soldered in an inert atmosphere inside the chamber. The automatic soldering apparatus is characterized in that a blowout port for spraying on a printed circuit board is installed, and an exhaust device is installed in the vicinity of the entrance of the printed circuit board.

  The present invention will be described below with reference to the drawings. FIG. 1 is a front sectional view of the inert soldering apparatus of the present invention.

  In the inert soldering apparatus of the present invention, the conveyor 1 is installed with an upward inclination in the traveling direction (arrow A). Below the conveyor, processing devices such as a pre-heater 2, a jet solder bath 3, a cooling device 4, and the like are installed in the order of travel, and these processing devices are housed in a chamber 5.

  A non-illustrated fluxer and a preheater are installed outside the chamber 5 adjacent to the fluxer. The reason why the fluxer is installed outside the chamber is that when the flux is applied by the fluxer, the flux scatters and soils the chamber, and when the flux is applied, a low oxygen concentration is not required. A pre-heater (not shown) installed adjacent to the fluxer volatilizes the solvent of the flux applied to the printed circuit board and preheats the printed circuit board. Since the heating temperature is not too high, a low oxygen concentration is not necessary. Therefore, the fluxer and the preheater adjacent to the fluxer are installed outside the chamber.

  The pre-heater 2 installed in front of the jet solder tank 3 in the figure before the jet solder tank 3 is a printed circuit board preheated by a pre-heater (not shown) installed outside the chamber. Preheating is performed to a temperature suitable for attachment, and here, a low oxygen concentration is required for heating to a temperature higher than the preheating temperature in the preheater.

  In the conveyor 1, a pair of endless chains are rotating, and inner opposite chains run in the same direction (arrow A). The printed circuit board is held between a plurality of claws (not shown) attached to the inner opposing chains and runs on each processing apparatus.

  The preheater 2 is a panel heater and preheats the printed circuit board with radiant heat. When a panel heater is used as the pre-heater, the flow of gas in the chamber can be reduced because of the radiant heat, and the oxygen concentration is not increased by inflowing air from the outside.

  The jet solder tank 3 is provided with a primary jet nozzle 6 for jetting rough waves and a secondary jet nozzle 7 for jetting gentle waves. Further, lead-free solder 8 is placed in the jet solder bath, and is melted by a heater (not shown) and kept at a predetermined temperature.

  The cooling device 4 is connected to an inert gas supply device (not shown), and inert gas is ejected from the cooling device. If the refrigerator 9 is installed between the cooling device and the inert gas supply device, the inert gas can be ejected at a low temperature. If the inert gas can be sufficiently lowered by the inert gas supply device, the refrigerator need not be installed.

  The chamber 5 houses the preheater 2, the jet solder tank 3, and the cooling device 4 and is sealed so that no gas can flow in and out from the entrance and exit. A large number of labyrinth tapes 10 are suspended in the chamber. It is installed. The labyrinth stabilizes the gas in the chamber and prevents intrusion of outside air from the entrance / exit. Further, a glass plate 11 is fitted into the upper part of the jet solder bath 3 so that the molten solder jet state in the jet solder bath 3 can be observed from the outside through the glass plate. Furthermore, inflow pipes 12 and 12 for inert gas are installed in the chamber above the jet solder bath 3.

  An exhaust device 14 is installed in the vicinity of the inlet 13 of the inert soldering device. The exhaust device is connected to the blower 15 and forcibly sucks the gas in the vicinity of the inlet 13 of the inert soldering device from the exhaust device 14.

  Subsequently, soldering of the printed circuit board in the inert soldering apparatus of the present invention having the above-described configuration will be described. First, an inert gas (nitrogen) is caused to flow into the chamber 5 from the cooling device 4 and the inert gas inflow pipes 12 and 12 in the chamber, and the oxygen concentration in the chamber is lowered to 1000 ppm or less.

  When the oxygen concentration in the chamber drops to 1000 ppm or less, flux application and preheating are performed on the printed circuit board with a fluxer and a preheater (not shown). Thereafter, the printed circuit board is conveyed in the direction of arrow A by the conveyor 1 and enters the chamber 5 through the inlet 13 of the inert soldering apparatus, and is preheated to a predetermined temperature by the preheater 2. This predetermined temperature is about 150 ° C. when the solder in the jet solder bath is Sn-3Ag-0.5Cu lead-free solder (melting point: 217 ° C.).

  The printed circuit board preheated by the preheater 2 is conveyed to the jet solder bath 3 and soldered without unsoldering is performed by the primary jet nozzle 6, and then the bridge and tsura are corrected by the secondary jet nozzle 7.

  The printed circuit board soldered in the jet solder bath 3 is carried to the cooling device 4. A low-temperature inert gas is sprayed from the cooling device 4 onto the soldering surface of the printed circuit board to cool the molten solder adhering to the printed circuit board. The inert gas blown from the cooling device 4 is cooled to below zero (about −10 ° C.) by the refrigerator 9, and rapidly cools the soldering surface of the printed circuit board. The lead-free solder that adheres to the printed circuit board due to this rapid cooling solidifies rapidly, so that not only cracks and cracks are generated even if vibration or impact is applied to the printed circuit board, but the mechanical strength is improved by making the structure finer. .

  The inert gas flowing into the chamber 5 from the cooling device 4 flows in the direction of the inlet 13 as indicated by an arrow B. This is because the exhaust device 14 is installed in the vicinity of the inlet 13, and the gas near the inlet 13 is forcibly sucked from the exhaust device 14, so that the inert gas in the chamber 5 flows in the direction of the inlet 13. Therefore, since the inert gas supplied from the cooling device 4 and the inlet 12 flows into the jet solder tank 3 and the preheater 2 that require an inert gas during soldering, the oxygen concentration is low. .

It can be applied to an automatic soldering apparatus that performs soldering of a printed circuit board in an inert atmosphere.

Front sectional view of the inert soldering device of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Conveyor 2 Preheater 3 Jet solder tank 4 Cooling device 5 Chamber 8 Molten solder 9 Refrigerator 12 Inert gas inlet 13 Inlet 14 Exhaust device 15 Blower

Claims (5)

A slope that increases from the inlet side to the outlet side of the printed circuit board is attached, the preheater, the jet solder bath, and the cooling device are covered with a chamber, and sealed so that gas cannot flow in and out from other than the printed circuit board entrance and exit. In an automatic soldering apparatus for soldering a printed circuit board provided with an inert gas inlet for making the inside of the chamber an inert atmosphere on the solder bath,
A number of entrance side labyrinth tapes hung on the preheater side;
A number of outlet side labyrinth tapes hung on the cooling device side;
A blowout port for blowing a low-temperature inert gas on the soldering surface of the printed circuit board installed in a cooling device provided near the jet solder bath of the outlet side labyrinth tape;
An exhaust device installed on the inlet side labyrinth tape side,
The automatic solder is characterized in that the inert gas is introduced into the chamber from the inert gas inlet and the outlet, and the inert gas flowing into the chamber is sucked by the exhaust device. Attachment device. 2. The automatic soldering apparatus according to claim 1, wherein an exhaust device near the entrance of the printed circuit board on the entrance side labyrinth tape side is installed on a conveyor of a transport device. 2. The automatic soldering apparatus according to claim 1, wherein the exhaust device is installed on a conveyor of a transfer device outside the chamber. 4. The automatic soldering apparatus according to claim 1, wherein the blowout port is connected to an inert gas supply device via a refrigerator. The automatic soldering apparatus according to any one of claims 1 to 4, wherein an oxygen concentration in the chamber is set to 1000 PPM or less by the inert gas.

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