JP3874578B2 - Soldering method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention solders a plate-like workpiece to be soldered on which a large number of electronic components such as a printed wiring board are mounted.MethodAbout.
[0002]
[Prior art]
When an electronic component is mounted on a printed wiring board to form an electronic circuit, soldering is performed. That is, electrical connection and mechanical connection are performed by mounting electronic components on a printed wiring board and soldering the electrodes and lead wires of the components to the circuit pattern of the printed wiring board.
[0003]
By the way, it is known that the soldering strength, that is, the mechanical connection strength is increased by rapidly cooling the solder immediately after the soldering. For example, this is described in Japanese Utility Model Publication No. 45-21716. Therefore, the soldering apparatus is configured to provide a cooling step after the soldering step as described in the publication. And it is considered so that a printed wiring board with high reliability can be manufactured. The cooling technique described in Japanese Utility Model Publication No. 45-21716 is configured to cool the printed wiring board by blowing air with a fan.
[0004]
This also applies to a reflow soldering apparatus. For example, Japanese Patent Application Laid-Open No. 60-6270 discloses a configuration provided with a cooling fan for cooling a printed wiring board subjected to reflow soldering.
[0005]
On the other hand, in the soldering process, the soldered part of the printed wiring board and the solder are not oxidized to improve the solderability, and the fluidity of the molten solder is improved to reliably solder the fine soldered part. In order to realize so-called micro soldering, there is a soldering technique for performing soldering in an inert gas atmosphere having a low oxygen concentration.
[0006]
A soldering apparatus that performs soldering in an inert gas atmosphere having a low oxygen concentration includes nitrogen gas (N₂ An inert gas such as gas) is supplied to form an atmosphere having a low oxygen concentration, and a soldering process is performed in the chamber.
[0007]
In such a soldering apparatus, N₂ Gas consumption is added as a running cost, so N required to maintain the target oxygen concentration₂ There is a need for low gas consumption. Therefore, a special cooling technique is used so that air outside the chamber body does not flow into the chamber body.
[0008]
For example, the reflow soldering technique disclosed in Japanese Patent Laid-Open No. Hei 4-262862 discloses a cold N supplied from a cylinder.₂ This is a technology configured to cool by blowing gas onto a printed wiring board after soldering. Japanese Patent Laid-Open No. 7-202405 discloses a technique in which the atmosphere inside the chamber is cooled and filtered to remove the flux fume and the like, and the cooled atmosphere is blown onto the printed wiring board after soldering. This technology is configured to be able to
[0009]
In the soldering technique disclosed in Japanese Patent Laid-Open No. 10-98259, a technique for spraying a cooling liquid onto a printed wiring board after soldering to cool it and then supplying warm air to dry the wet printed wiring board. Is disclosed.
[0010]
[Problems to be solved by the invention]
In recent years, electronic devices having an electronic circuit formed on a printed wiring board have been used in every field of life, and as a facility that supports life, a high level of reliability is required for its reliability. Therefore, it is required to further improve the mechanical connection strength of soldering.
[0011]
In addition, lead mixed in the solder of discarded electronic equipment starts to melt and contaminates the environment and the human body with lead poison, and lead-less solder is being used. However, this lead-less solder has a problem that a lift-off phenomenon is likely to occur in the soldered portion due to solidification segregation of the components. The lift-off phenomenon is a poor soldering that causes a partially embrittled region in the soldered part due to segregation or the like generated in the solder of the soldered part and causes peeling or cracking in the soldered part. It is. In particular, it is known to easily occur in lead-free solder containing bismuth.
[0012]
In order to prevent such a lift-off phenomenon, the printed wiring board after soldering, that is, the solder of the soldered portion is rapidly cooled, and segregation or the like occurs as the molten solder solidifies or solidifies. It is to avoid.
[0013]
However, the cooling technique described in Japanese Utility Model Publication No. 45-21716 and the cooling technique disclosed in Japanese Patent Application Laid-Open No. 60-6270, that is, a cooling technique that relies solely on air flow, are used as a normal air atmosphere as a cooling medium. Since this is used as it is, there is a problem that the cooling rate is low and the degree of cooling cannot be freely adjusted. In addition, these techniques have a problem that they cannot be used as they are in a soldering apparatus that supplies an inert gas into the chamber body and performs soldering in an inert gas atmosphere having a low oxygen concentration.
[0014]
In other words, blowing and supplying air to a printed wiring board transported in a chamber in which an inert gas atmosphere having a low oxygen concentration is formed causes an extremely large increase in the oxygen concentration, resulting in a low oxygen concentration. This is because an active gas atmosphere cannot even be formed. As a result, the soldering quality is greatly impaired.
[0015]
Also, even if the atmosphere in the chamber is blown as it is and blown onto the printed wiring board, sufficient cooling is provided in the atmosphere in the chamber where the temperature is rising by high-temperature molten solder, a preheating heater, or the like. Not only can this be performed, but the flow of the atmosphere in the chamber is extremely intense due to this air blowing, so that a large amount of air enters from the carry-in port and carry-out port of the printed wiring board, causing the oxygen concentration to increase or not. It fluctuates stably. As a result, this also significantly impairs the soldering quality.
[0016]
On the other hand, there is a technique that considers special technical matters when performing soldering in an inert gas atmosphere with a low oxygen concentration as described above. However, as in the technique of JP-A-4-262862. Cold N supplied from cylinder₂ In a configuration in which cooling can be performed by blowing gas onto the printed wiring board after soldering, N is used to adjust the cooling amount and cooling temperature.₂ It is necessary to adjust the flow rate of the gas, which causes a problem that the oxygen concentration in the chamber changes. As a result, the soldering quality changes and decreases due to the change in oxygen concentration. Furthermore, in order to increase the cooling amount and lower the cooling temperature, a large amount of N₂ Need to supply gas, expensive N₂ There is a problem in that a large amount of gas is consumed to increase the running cost of soldering.
[0017]
The technique disclosed in Japanese Patent Application Laid-Open No. 7-202405 is a cooling technique that has extremely good power efficiency (or thermal efficiency) when viewed from the whole soldering apparatus. However, the cooling rate is further increased to further increase the cooling amount. Increasing the flow rate of the cooled atmosphere that is blown and supplied to the printed wiring board to increase the size of the chamber causes an unstable flow in the atmosphere in the chamber and the oxygen concentration in the chamber tends to fluctuate in an unstable manner. There is.
[0018]
Further, in the technique of spraying a cooling liquid onto a printed wiring board disclosed in Japanese Patent Application Laid-Open No. 10-98259, the cooling liquid which is sprayed and becomes a mist is floated on the side opposite to the surface to be soldered (in the drawing). It also adheres to the printed wiring board surface on the upper side, that is, it also adheres to the electronic components mounted on that surface, which impairs the function of the electronic components or renders them unusable and solders defective products. . In other words, there are many electronic components that should not have liquid droplets attached thereto (for example, non-molded components such as switches, relays, transformers, coils, etc.). The printed wiring board on which is mounted cannot be soldered and cooled.
[0019]
As described above, it is extremely difficult to perform cooling more rapidly than in the past while performing soldering in an inert gas atmosphere in the chamber, and to further freely adjust the cooling rate and the cooling amount. is there.
[0020]
  An object of the present invention is to provide a chamber body that maintains an inert gas atmosphere having a low oxygen concentration.Using lead-free solderSoldering to perform solderingMethodIn this case, the printed wiring board can be rapidly cooled to a desired temperature by the cooled air, which is inexpensive, and the oxygen concentration is stable and the cost required for cooling is low. Soldering without impairing the function and performance of the wiring board and the electronic components on itMethodAs a result, a highly reliable printed wiring board can be produced by soldering with high connection reliability.
[0021]
[Means for Solving the Problems]
  Soldering of the present inventionMethodIn the chamber body that is supplied with an inert gas and maintains an inert gas atmosphere with a low oxygen concentration, molten solder is supplied to the surface to be soldered while the printed wiring board, which is the work to be soldered, is transported by the transport means By meansLead-freeSoldering to make contact with molten solderMethodIn the above, the printed wiring board after soldering, that is, the work to be soldered, is soldered to the soldered portion by using the atmosphere in the chamber body.Solidification segregation occurs inIt is characterized in that it is configured so that it can be cooled rapidly before it starts.
[0022]
  That is, a tunnel-like chamber body is provided along a transport means for transporting the printed wiring board, and an inert gas supply means for supplying an inert gas into the chamber body is provided, so that the inert gas having a low oxygen concentration is provided in the chamber body. Create an atmosphere.
  Also, lead-less molten solder supply means for supplying lead-less molten solder to the soldered portion by bringing a jet wave of lead-less molten solder into contact with the soldered portion of the printed wiring board in the chamber body, The heating means for the printed wiring board for preventing the solidification of the lead-less molten solder supplied to the soldered portion after leaving the jet wave and the supply of the cooled outside air from the cooling body from the cooling means By providing an air exhaust port that surrounds the side periphery of the cold air outlet housing that blows cold air having a temperature lower than the atmospheric temperature and that is connected to the air exhaust means to the outside of the chamber body, the cold air flows from the cold air outlet housing to the exhaust air outlet, so A heat removal port housing for forming an air flow is provided in order along the transport direction of the transport means.
  Then, after supplying lead-less molten solder to the soldered portion of the printed wiring board in the inert gas atmosphere of low oxygen concentration, the printed wiring board is heated by the heating means and supplied to the soldered portion. The lead-free molten solder that has been transported to the heat sink housing and supplied to the soldered portion of the printed wiring board is brought into contact with the lead-free molten air flow while preventing solidification of the lead-free molten solder. The lead-less molten solder is solidified before solidification segregation occurs, so that a soldered portion is formed so as not to cause a lift-off phenomenon.Configure as follows.
[0023]
As a result, the cooled air outside the chamber body blown out from the cold air outlet case at the heat removal port of the heat removal case housing of the quenching means immediately flows to the air exhaust port of the heat exhaust port case, and A mountain-like cold airflow that is slightly raised is formed at the heat removal port. Therefore, it is extremely unlikely that the low oxygen concentration inert gas atmosphere held in the chamber body is disturbed by a large amount of air supplied or unstable atmosphere flow.
[0024]
The behavior of this mountain cold wind flow is determined by the supply flow rate of the cold wind and the exhaust flow rate of the exhaust wind, and a stable mountain cold wind flow is usually formed by selecting the latter slightly larger than the former. be able to. Then, by controlling the cooling power of the cooling device so that the temperature of the cold air supplied from the cold air outlet housing reaches a predetermined target temperature, the cooling rate and amount of cooling by the cold air can be freely adjusted. can do. In addition to this, it is also possible to adjust the cooling rate and the cooling amount of a printed wiring board, which will be described later, by increasing or decreasing the absolute values of the cold air supply flow rate and the exhaust air flow rate.
[0025]
  Therefore, the close position of the heat removal port housingLead-freeWhen the soldered surface of the printed wiring board to which the molten solder was supplied is transported and passed by the conveyor, a mountain-shaped cold airflow flows in contact with the soldered surface and is supplied to the soldered portion.Lead-freeThe molten solder is rapidly cooled and can be solidified rapidly before solidification segregation or the like occurs. As a result, soldering with high mechanical connection strength can be performed.
[0026]
The cooling process by the rapid cooling means is performed by blowing air to the printed circuit board as cold air that has been cooled by the cooling device after the air outside the chamber body is taken in. At that time, heat is taken from the molten solder in the soldered part. The temperature rises. Then, the exhausted heat is performed by exhausting the air whose temperature has increased to the outside of the chamber body.
[0027]
The cold air blown and supplied to the printed wiring board usually comes into contact with molten solder at 200 ° C. or higher, and the temperature rises. Therefore, it is usually higher than the atmospheric temperature outside the chamber body. Therefore, the cooling efficiency of the cooling device can be increased by not allowing the cooling device to reflux. In addition, the configuration of the present invention is extremely important because it is necessary to separately adjust the supply flow rate of the cold air and the exhaust air flow rate of the exhaust air to form a desired mountain cold air flow.
[0029]
  AlsoThe molten solder in the soldered part of the printed wiring board that has been supplied with the molten solder is completely solidified as the temperature of the solder supplied to the soldered part drops while it is transported to the heat removal port housing And the solder supplied to the part to be soldered in the heat sink housing is rapidly cooled to solidify completely.ing.
[0030]
  ThereforeWhen the molten solder supply means to the printed wiring board and the rapid cooling means for the printed wiring board cannot be disposed at a close distance, or when the conveying speed by the conveying means is slow, etc.Lead-freeAfter the molten solder is supplied, it is transferred to the quenching means.Lead-freeWhen there is a risk of solidification of the molten solder, the solidification of the molten solder is delayed by the heat-retaining heating means, and rapidly cooled at the heat removal port of the heat removal port housing by the rapid cooling means to cause solidification segregation, etc. Therefore, soldering with high mechanical connection strength can be performed.
[0031]
DETAILED DESCRIPTION OF THE INVENTION
  Soldering of the present inventionMethodCan be implemented in the following example embodiments.
[0032]
(1) Configuration of soldering equipment
  FIG. 1 illustrates the present invention.Realize soldering methodIt is a figure for demonstrating the embodiment of a soldering apparatus, (a) is a sectional side view, (b) is the figure which looked at (a) from the II cross section. In addition, FIG.Example embodimentIt is a figure for demonstrating the structure of the heat-release port housing | casing used for FIG.
[0033]
In this embodiment, the lower surface of the printed wiring board conveyed by the conveyor is a surface to be soldered, and a portion to be soldered exists on the surface side. Soldering is flow soldering.
[0034]
  That is, the transport conveyor 1 transports the printed wiring board 6 from the carry-in entrance 1 a to the carry-out exit 1 b, and the preheating heater 2 and the heater 2 are disposed on the lower side along the transport direction A of the transport conveyor 1.Lead-freeA solder bath 5 for forming a jet wave 4 of the molten solder 3 and a quenching means 7 for quenching a soldered portion of the printed wiring board 6 are disposed, and a tunnel is provided along the conveyor 1 so as to cover them. A cylindrical chamber body 8 is provided. still,Lead-freeThe solder tank 5 for forming the jet wave 4 of the molten solder 3 has a skirt portion 9 provided at the opening of the chamber body 8.Lead-freeBy immersing in the molten solder 3,Lead-freeThe arrangement of the jet wave 4 of the molten solder 3 in the chamber body 8 and the sealing of the chamber body 8 are realized.
[0035]
  And the printed wiring board 6 andLead-freeN in the chamber body 8 above the position where the jet wave 4 of the molten solder 3 is in contact, that is, above the solder bath 5.₂ Gas supply port 10 is provided and N₂ Gas cylinder or N₂ N from gas generator (both not shown)₂ A gas is supplied into the chamber. Although not shown, an oxygen concentration measuring device for measuring the oxygen concentration in the chamber body 8 is usually provided, and N is set so that the oxygen concentration becomes a predetermined value.₂ It is operated to adjust the gas supply flow rate.
[0036]
The restraining plate 11 provided in the chamber body 8 is a member for forming a labyrinth flow path in the chamber body 8, whereby the chamber body by the heat convection of the atmosphere in the chamber body 8 and the conveyor 1. It is possible to suppress an unnecessary atmosphere flow such as taking the atmosphere inside the chamber body 8 out of the chamber body 8 or bringing the atmosphere outside the chamber body 8 into the atmosphere, and form an inert gas atmosphere having a stable low oxygen concentration. become.
[0037]
  On the other hand, the solder bath 5 is heated by a heater (not shown) and melted.Lead-freeMolten solder 3 is contained and thisLead-freeThe molten solder 3 is supplied to the nozzle 14 of the nozzle body 13 by the pump 12 to form the jet wave 4, and the printed wiring board 6 that is conveyed in the direction of arrow A by the conveyor 1 to the jet wave 4 is soldered. The surface 6a is brought into contact with the soldered part.Lead-freeSoldering is performed by supplying the molten solder 3. Of course, the heater power is controlled by temperature adjusting means (not shown),Lead-freeThe temperature of the molten solder 3 is maintained at a target temperature.
[0038]
  And the printed wiring board 6 isLead-freeA quenching means 7 for rapidly cooling the soldered portion of the printed wiring board 6 is provided at a position immediately after the molten solder 3 leaves the jet wave 4.
[0039]
The rapid cooling means 7 is broadly divided into a cool air supply means 15 that takes in the air outside the chamber body 8 and cools and blows air, and exhausts the air whose temperature has been increased by cooling the printed wiring board 6 to the outside of the chamber body 8. Heat exhausting means 16 for exhausting heat, and a heat removal case 17 that forms a mountain-like cold airflow 30 that flows in a mountain shape and is difficult to leak to the outside.
[0040]
The cold air supply means 15 includes a fan 18 as a blowing means and a chiller 19 as a cooling means, and is configured to be able to adjust the flow rate of the cooled cold air. That is, although not shown, an inverter for adjusting the rotational speed of the fan 18 is provided, and the rotational speed of an induction motor (not shown) for driving the fan is adjusted by adjusting the output frequency and output voltage by the inverter. is there.
[0041]
Further, the chiller 19 is configured to be able to feedback control the degree of cooling, and the cold air temperature signal S detected by the cold air temperature sensor 20 provided in the heat removal port 17a of the heat removal port housing 17 is provided._t Referring to FIG. 4, the operation is performed to maintain a predetermined temperature set in advance.
[0042]
The exhaust heat means 16 is constituted by a fan 21 that can adjust the exhaust air flow rate. Like the fan 18 of the cold air supply means 15, the exhaust heat means 16 adjusts the exhaust air flow rate by adjusting the rotational speed by an inverter. It is a mechanism to discharge.
[0043]
On the other hand, the heat removal port housing 17 is connected to the cold air supply means 15 and the exhaust heat means 16 and receives the supply of cold air from the cold air supply means 15 as shown in FIG. A cool air outlet housing 22 that blows out from 22a and an exhaust heat outlet housing 23 connected to the exhaust heat means 16 are provided. Then, the exhaust port 23a of the heat exhaust port housing 23 is configured to surround the side periphery of the air blowing port 22a of the cold air port housing 22, and the heat removal port 17a is formed to configure the heat removal port housing 17. The heat removal port housing 17 configured in this manner is provided at a close position so that the heat removal port 17a faces the soldering surface 6a of the printed wiring board 6 conveyed by the conveyance conveyor 1.
[0044]
The cold air outlet housing 22 has a porous flow straightening plate 24 for uniformly adjusting the flow of the cold air blown from the cold air supply means 15 and a flow straightening plate in which a plurality of plate-like members for adjusting the flow direction are arranged in parallel. 25 is provided. The cold air port housing 22 is supported and fixed to the heat exhaust port housing 23 by support legs 32. The cold air supply pipe 26 is a means for connecting the cold air supply means 15 and the cold air outlet casing 22, and the exhaust heat pipe 27 is a means for connecting the exhaust heat outlet casing 23 and the exhaust heat means 16.
[0045]
  The heat removal port 17a of the heat removal port housing 17 is configured to face the soldered surface 6a of the printed wiring board 6, but the position where the heat removal port housing 17 is provided is the printed wiring board. 6 isLead-freeIt is preferable to provide it at a position within 5 seconds as much as possible after detachment from the molten solder 3. It was supplied to the soldered part of the printed wiring board within this time.Lead-freeThis is because the molten solder 3 can be rapidly cooled before the molten solder 3 is completely solidified.
[0046]
  However, for example, with the printed wiring board 6Lead-freeIn order to increase the contact time of the molten solder 3 with the jet wave 4, it is necessary to slow down the conveyance speed of the printed wiring board 6,Lead-freeThe printed wiring board 6 is caused by the case where it cannot be provided close to the jet wave 4 of the molten solder 3.Lead-freeIf it cannot be provided at a position within 5 seconds after detachment from the molten solder 3, it is formed in the solder bath 5.Lead-freeBetween the jet wave 4 of the molten solder 3 and the heat release casing 17, a heat-retaining heating means for keeping the solder of the soldered portion of the printed wiring board 6, that is, a heat-retaining heater (heat-retaining heating means) 29 Is provided.
[0047]
  As this heat-retaining heating means, a hot-wire heating means that mainly uses a heat ray such as infrared rays, a hot-air heating means that forms a high-temperature atmosphere with a heater, or a heating means that uses these in combination is suitable. However, it was supplied to the part to be solderedLead-freeThe hot air should not be supplied at such a speed that the molten solder 3 is blown away or its fillet shape is deformed. That is, this causes deterioration of the electrical connection state and mechanical connection state of the soldered portion, resulting in poor soldering.
[0048]
Note that the heat retaining heater 29 illustrated in FIG. 1 is configured by arranging a sheathed heater side by side on a box-shaped heater holding element, and a stainless steel plate as an infrared reflecting plate on the bottom surface of the holding frame. The warming heater 29 is disposed at a close distance (a distance of about 1 to 3 cm) facing the soldered surface 6a of the printed wiring board 6 conveyed by the conveyor 1.
[0049]
Thereby, infrared rays are radiated from the sheathed heater to the lower surface side of the printed wiring board 6, that is, the soldered surface 6 a side, and when the printed wiring board 6 is transported onto the heat retaining heater 29, the printed wiring board 6. As a lid, it becomes possible to maintain a high-temperature atmosphere between the box-shaped heater holding frame and the printed wiring board 6 and its soldered portion can be kept warm. By the way, at a distance of 3 cm or more, the outflow of the high temperature atmosphere increases and the heat retention is extremely reduced.
[0050]
  In addition, the insulation temperature of the printed wiring board 6, that is, the soldered portion was supplied.Lead-freeAlthough the heat retention temperature of the molten solder 3 varies depending on the solder material used, it is preferable that the temperature can be maintained at a temperature higher than the liquidus. In particular, when lead-free solder contains bismuth, it is important for preventing the lift-off phenomenon caused by the occurrence of solidification segregation.
[0051]
  Thereby, it supplied to the part to be soldered of the printed wiring board 6Lead-freeThe molten solder 3 can be kept warm and rapidly cooled by the heat removal port 17a of the heat removal port housing 17 of the rapid cooling means 7 to be solidified at once.
[0052]
The most important aspect of the present invention is that the printed wiring board 6 can be cooled by the cooled air without disturbing the atmosphere in the chamber body 8 holding the inert gas atmosphere having a low oxygen concentration. There are features.
[0053]
That is, as shown in FIG. 2, by forming the heat removal outlet casing 17, the cooled air outside the chamber body 8 blown out from the cold air outlet casing 22 immediately flows to the exhaust outlet 23 a of the heat exhaust outlet casing 23. Thus, a mountain-like cold air flow 30 in a slightly raised state is formed at the heat removal port 17 a of the heat removal port housing 17. Therefore, the low oxygen concentration inert gas atmosphere held in the chamber body 8 is extremely unlikely to cause a disturbance such as a large amount of air supplied or unstable atmosphere flow.
[0054]
The behavior of the mountain cold air flow 30 is determined by the supply flow rate of the cold air and the exhaust air flow rate of the exhaust air. Usually, the stable cold air flow 30 is obtained by selecting the latter slightly larger than the former. Can be formed. That is, the cold air supply means 15 and the exhaust heat means 16 are not configured to circulate, and the rotational speeds of the fans 18 and 21 are independently adjusted to form the mountain-like cold air flow 30 as described above. Will be able to.
[0055]
  Supplied to the soldered part of the printed wiring board 6Lead-freeThe cooling rate and the cooling amount of the molten solder 3 are determined by the temperature of the mountain-shaped cold air flow 30 and its flow velocity and consequently the flow rate. As described above, the temperature of the cold air can be freely controlled by using the chiller 19 having a temperature control function. Can be adjusted and set. Further, the cooling rate and the cooling amount of the printed wiring board 6 to be described later can also be adjusted by increasing or decreasing the absolute values of the cold air supply flow rate and the exhaust air flow rate.
[0056]
  Therefore, in the soldered portion of the soldered surface 6a of the printed wiring board 6,Lead-freeWhen the molten solder 3 is supplied and is transported and passed by the conveyor 1 near the position of the heat removal port 17a of the heat removal port housing 17, the mountain cold air flow 30 flows in contact with the soldered surface 6a. Supplied to the soldered partLead-freeThe molten solder 3 can be rapidly cooled and solidified quickly before solidification segregation occurs.Without causing the lift-off phenomenon,Soldering with high mechanical connection strength can be performed.
[0057]
  The process of cooling the printed wiring board 6 by the rapid cooling means 7 is carried out by blowing air to the printed wiring board 6 as cold air that has been taken in by the air outside the chamber body 8 and cooled to a low temperature by the cooling means 19, and at that time, the soldering target AttachedLead-freeIn this process, heat is removed from the molten solder 3 and the temperature rises, and the air (hot air) whose temperature has risen is exhausted outside the chamber body 8 to exhaust heat.
[0058]
  Here, the cold air blown and supplied to the printed wiring board 6 is usually 200 ° C. or higher.Lead-freeThe temperature rises in contact with the molten solder 3. Therefore, it is usually higher than the atmospheric temperature outside the chamber body 8. Therefore, the cooling efficiency of the quenching means 7 can be significantly increased by not circulating or refluxing the cooling means 19.
[0059]
  Also, as mentioned above,Lead-freeBy providing a heat retaining heater 29 between the jet wave 4 of the molten solder 3 and the heat sink casing 17,Lead-freeOf the part to be soldered of the printed wiring board 6 that has been supplied with the molten solder 3Lead-freeThe molten solder 3 was prevented from being completely solidified by being lowered in temperature while being transported to the heat sink casing 17, and was supplied to the soldered portion.Lead-freeThe molten solder 3 can be rapidly cooled by the heat sink housing 17 and solidified at once.
[0060]
  That is, to the printed wiring board 6Lead-freeWhen the supply means of the molten solder 3 and the rapid cooling means 7 of the printed wiring board 6 cannot be disposed at a close distance, or when the conveying speed by the conveying means is slow, the soldered portion of the printed wiring board 6 isLead-freeAfter the molten solder 3 is supplied, it is transferred to the rapid cooling means 7 until the molten solder 3 is supplied.Lead-freeIn the case where there is a possibility that the molten solder 3 is completely solidified, the heating means 29 for heat retentionLead-freeThe solidification of the molten solder 3 is delayed, the rapid cooling means 7 rapidly cools at the heat removal port 17a of the heat removal port housing 17 to prevent solidification segregation and the like, and soldering with high mechanical connection strength can be performed. it can.
[0061]
  Book as aboveExample embodimentIn this soldering apparatus, the soldered portion of the printed wiring board 6 was supplied.Lead-freeMolten solder 3Solidification segregation occurs inIt is possible to cool quickly beforeWithout causing soldering defects such as lift-off phenomenon,The mechanical connection strength can be increased more than ever.
[0062]
In the soldering apparatus illustrated in FIG. 1, the example in which the rapid cooling means 7 of the printed wiring board 6 is provided only on the soldered surface 6 a side of the printed wiring board 6, that is, on the lower surface side of the figure. The rapid cooling means 7 having the same configuration is also provided on the upper side of the printed wiring board, and the printed wiring board 6 is disposed on both the soldered surface 6a side and the lower surface of the figure or the upper surface of the figure. It can also be set as the structure which cools rapidly from.
[0063]
  In this case, not only the molten solder supplied to the soldered portion of the printed wiring board 6 but also the printed wiring board 6 itself can be rapidly cooled.Lead-freeThe cooling rate of the molten solder 3 can be further increased, and the cooling amount can be further increased.
[0064]
Further, as illustrated in FIG. 1A, a printed wiring board detection sensor 31 for detecting the entry of the printed wiring board 6 conveyed by the conveyor 1 is provided above the heat sink housing 17, and this detection signal S_p The fan 18 for supplying cold air and the fan 21 for exhausting air are rotated, and only when the printed wiring board 6 as the work to be cooled is conveyed above the heat sink housing 17 is cooled in a mountain shape. You may comprise so that the wind flow 30 may be formed.
[0065]
Alternatively, in a standby state in which the printed wiring board 6 does not enter, when the rotation speed of the cold air supply fan 18 and the exhaust air fan 21 is slowed down and the entry of the printed wiring board 6 is detected by the detection signal Sp. Alternatively, the rotational speeds of the fans 18 and 21 may be increased to normal rotation. As a result, the power consumption of the chiller 19 for cooling the air can be further reduced, and the influence of the mountain-shaped cold airflow 30 on the atmosphere in the chamber body 8 can be further reduced. Become.
[0066]
Such a detection signal S_p The rotation / stop control and rotation speed control of the fan can be performed using a sequencer, a programmable controller, and the like. Since examples of such control techniques are well known, the configuration thereof is omitted and not shown. .
[0067]
【The invention's effect】
  As described above, the soldering of the present inventionMethodIs supplied to the soldered part of the printed wiring board which is the work to be solderedLead-freeMolten solderSolidification segregation occurs inCooling quickly beforeThen solidifyIt becomes possible to do. In addition, the cooling temperature, cooling rate, and amount of cooling can be adjusted freely, and the flow state of the inert gas atmosphere with a low oxygen concentration and the oxygen concentration can be maintained with a stable cooling efficiency. Cooling can be performed.
[0068]
  As a result, the soldering strength of the work to be soldered, that is, the mechanical connection strength can be greatly increased. Also,Due to solidification segregationA lift-off phenomenon does not occur and a printed wiring board with high soldering reliability can be manufactured.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining an embodiment of a soldering apparatus of the present invention.
FIG. 2 is a diagram for explaining a configuration example of a heat removal port housing used in the soldering apparatus of the present invention.
[Explanation of symbols]
1 Conveyor
2 Preheating heater
3Lead-freeMolten solder
4 Jet waves
5 Solder bath
6 Printed wiring board
6a Soldering surface
7 Quenching means
8 Chamber body
9 Skirt
10 N₂ Gas supply port
11 Deterrence plate
12 Pump
13 Nozzle body
14 Air outlet
15 Cold air supply means
16 Heat exhaust means
17 Heat sink housing
17a Heat outlet
18 fans
19 Chiller (cooling means)
20 Cold air temperature sensor
21 fans
22 Cold air outlet housing
22a Air outlet
23 Heat exhaust port housing
23a Air vent
24 perforated current plate
25 Current plate
26 Cold air supply pipe
27 Waste heat pipe
28 Exhaust vent
29 Heat insulation heater
30 mountain cold wind
31 Printed wiring board detection sensor
32 Support legs

Claims (1)

Inert gas with a low oxygen concentration in the chamber body is provided with an inert gas supply means for supplying an inert gas into the chamber body with along the conveying means to convey the printed circuit board providing a tunnel-shaped chamber body Forming an atmosphere,
Moreover, said chamber body and lead-free molten solder supplying means for supplying a lead-free molten solder to the portion to be soldered by contacting the jet flow of the lead-free molten solder portion to be soldered of the printed wiring board, The heating means for the printed wiring board for preventing the solidification of the lead-less molten solder supplied to the soldered portion after leaving the jet wave and the supply of the cooled outside air from the cooling body from the cooling means By providing an air exhaust port that surrounds the side periphery of the cold air outlet housing that blows cold air having a temperature lower than the atmospheric temperature and that is connected to the air exhaust means to the outside of the chamber body, the cold air flows from the cold air outlet housing to the exhaust air outlet, so A heat sink casing for forming a wind flow is provided in order along the transport direction of the transport means,
After supplying lead-less molten solder to the soldered part of the printed wiring board in the inert gas atmosphere of low oxygen concentration, the printed wiring board was heated by the heating means and supplied to the soldered part The lead-less molten solder is rapidly cooled by being brought into contact with the lead-less molten solder conveyed to the heat sink housing and supplied to the soldered portion of the printed wiring board while preventing the solidification of the lead-less molten solder. Forming a soldered portion so that the lead-off molten solder is solidified before solidification segregation occurs and the lift-off phenomenon does not occur,
Soldering method characterized by

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