JP2008263233A - Method of partially soldering printed-circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for partially soldering a printed-circuit board, which can solve problems that: an oxide of a solder or a carbonized flux adheres to a soldered region; a solder projection, a solder bridge, or unsoldering occurs; and the solder does not flow into a through hole sufficiently; when the printed-circuit board is soldered by a conventional soldering method. <P>SOLUTION: Before a molten solder is brought into contact with the solder region of the printed-circuit board, the molten solder is jetted from a jet nozzle to clean the carbonized flux or the oxide of a solder adhering to the inside of the jet nozzle and to heat the jet nozzle sufficiently. After that, as the molten solder adheres to the printed-circuit board, the printed-circuit board is moved up to a position for the molten solder not to be cut, then the printed-circuit board is moved down slowly, to be cut. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a partial soldering method in which soldering is performed with molten solder that jets only to a necessary portion of a printed circuit board.

  In general, soldering of a printed circuit board is performed by an automatic soldering apparatus. The automatic soldering device is a device in which a fluxer, a preheater, a jet solder bath, a cooler, and the like are installed. When soldering a printed circuit board with the automatic soldering device, flux is applied to the entire back surface of the printed circuit board with a fluxer, pre-heated with a preheater, solder attached in a jet solder bath, and cooled with a cooler to complete the soldering. To do.

  Incidentally, in a recent printed board, as shown in FIG. 10, a large number of soldering portions 2... On the back surface of the printed board 1 are gathered to form a soldering group 3. A large number of soldering parts form a soldering group because electronic components mounted on a printed circuit board have many leads installed in one electronic component, such as PGA or dual-in package, This is because electrodes that are electrically connected to a large number of jacks are attached. In recent printed boards, surface mounted components D, connectors C, and the like are sometimes mounted on the back surface of the printed board in order to increase the mounting density. Therefore, in recent printed circuit boards, the soldering portion is a soldering group, and a surface mount component, a connector and the like are mounted on the back surface.

  When a printed circuit board having a surface-mounted component or connector mounted on the back surface is soldered by an automatic soldering apparatus used for soldering a general printed circuit board, a problem occurs in the surface-mounted component or connector. In other words, in an automatic soldering device, flux coating is applied to the entire back surface, the entire back surface is preheated, and molten solder is brought into contact with the entire back surface. Contact with the molten solder thus produced causes functional deterioration and thermal damage, and the connector attached to the back surface enters the insertion hole of the jack, and the molten solder enters the jack so that it cannot be used as a connector at all. Therefore, conventionally, so-called “partial soldering” has been adopted in which molten solder is brought into contact only with a necessary portion of the printed circuit board and soldering can be performed without affecting the unnecessary portion of the printed circuit board.

  As shown in FIG. 11, a partial jet solder bath used for partial soldering has a partial jet solder bath 4 provided with a jet pump 5 and a number of nozzles 6. 7 is kept in a molten state. The nozzle installation position coincides with the soldering group 3 of the printed circuit board 1 shown in FIG.

  Here, a conventional partial soldering method will be described with reference to FIGS.

FIG. 12: Flux application process The printed circuit board 1 is conveyed to the fluxer F by a conveyance device (not shown), and the soldering group and the spray nozzle are matched. At that position, the flux 6 is sprayed from the spray nozzle 8 to apply the flux to the soldering group. At this time, if only the spray nozzle is used, the flux spreads and sprays over a wide range. Therefore, the spray nozzle is surrounded by an enclosure 9 to control the spray direction and spray region.

FIG. 13: Preheating Step Next, the printed circuit board is transported to the preheater P by a transport device (not shown), and is stopped when the hot air outlet 10 of the preheater P and the soldering group of the printed circuit board coincide. Therefore, preheating is performed by applying hot air from the hot air outlet 10 of the preheater P to the soldering group of the printed circuit board.

Figure 14: Printed circuit board position setting process After the preheating of the soldering group is completed, the printed circuit board 1 is transported to the solder bath S, and the jet nozzle 11 of the solder bath and the soldering group of the printed circuit board are aligned and stopped. To do. At this time, the gap between the printed board 1 and the upper end of the jet nozzle 11 is a gap that can sufficiently flow out of the jet nozzle 11 after the molten solder 7 jetted from the jet nozzle contacts the printed board.

FIG. 15: Solder attachment process The molten solder 7 is jetted from the jet nozzle 11 and applied to the soldering group, and the solder is adhered to the soldering portion of the soldering group. The conventional jet nozzle used for partial soldering was a simple cylindrical one having substantially the same shape as the soldering group as shown in FIG. Therefore, the molten solder jetted from the jet nozzle has to flow out from the jet nozzle after jetting.

FIG. 16: Moving process of printed circuit board After solder is attached to the soldering portion of the soldering group, the molten solder 7 in the jet nozzle 11 is lowered to the liquid level of the solder bath. Here, it waits until the molten solder adhering to the soldering part is completely solidified, and when the solder is solidified, the printed circuit board is moved to a cooling device (not shown) to further lower the temperature of the printed circuit board.
JP 2003-000000 A Patent Ichiro “Various Hand Scanners” Patent Publication 2003

  By the way, when a printed circuit board is soldered by a conventional partial soldering method, solder oxide or flux carbide adheres to the soldered part, a bridge is generated in the soldered part, or solder is applied to the soldered part. However, there is a problem that unsolder that does not adhere completely occurs or that the solder does not sufficiently enter the through hole of the multilayer substrate. In particular, lead-free solder, which has recently been used frequently, has a high viscosity, and bridges frequently occur. The present invention is to provide a partial soldering method capable of solving these problems.

  As a result of intensive studies on problems in the conventional partial soldering method, the present inventors have found the following. In other words, solder oxide or flux carbide adheres to the soldering part. In the conventional soldering method, the molten solder is jetted from the jet nozzle at the time of soldering and brought into contact with the soldering group, and then the jet nozzle Lower the molten solder in the solder bath to the liquid level. At this time, the molten solder that has been in contact with the inside of the jet nozzle sticks to the inside of the jet nozzle, and is oxidized with the passage of time to become an oxide. Further, the flux applied to the soldering portion adheres to the jet nozzle, and is heated by the molten solder to become carbide, and also adheres to the inside of the jet nozzle. Then, when the molten solder that has been lowered to the level of the solder bath at the time of soldering the next printed circuit board is raised in the jet nozzle, the solder oxide or flux carbide (hereinafter referred to as oxide) adhered in the jet nozzle. Etc.) are peeled off by the molten solder rising in the jet nozzle, and these adhere to the soldered portion of the printed circuit board.

  Also, the conventional partial soldering method generates tsura, bridges, and unsolder in the soldered area, and sufficient solder cannot enter the through hole. The temperature of the soldered area increases sufficiently during soldering. Because it is not. In other words, if the soldered part is not sufficiently preheated, when the molten solder comes into contact with the soldered part, the molten solder will solidify before completely getting wet with the soldered part, resulting in a so-called wetting defect. These soldering defects occur. The cause of this is that even if the temperature of the molten solder in the solder bath is kept at a predetermined temperature, the temperature of the molten solder jetted from the jet nozzle is lower than the predetermined temperature, or the temperature of the soldering part is predetermined by preheating. This is because the temperature is not reached.

  The cause of tsura and bridge is not only the temperature of the molten solder and the soldering part, but also the molten solder detachment state from the soldering part after the molten solder is jetted from the jet nozzle and brought into contact with the soldering part. is doing. In other words, in the past, molten solder was brought into contact with the soldering part, and then the molten solder was lowered to the liquid level of the solder tank in the jet nozzle at a high speed. This separation condition was used for partial soldering, especially lead-free solder. This is not suitable for partial soldering, and thus wiggles and bridges have occurred in the soldered part.

  Therefore, the inventors of the present invention have found that if no oxide or the like remains in the jet nozzle, the oxide or the like does not adhere to the soldering portion, and if the jet nozzle is heated immediately before the jet, the molten solder jetted from the jet nozzle The present invention has been completed by paying attention to the fact that if the temperature does not drop and the molten solder is separated from the soldering portion by the pulling force of the molten solder, the occurrence of wiggle and bridge is eliminated.

  In the present invention, after the printed circuit board is brought into contact with the molten solder jetted from the jet nozzle, the printed circuit board is raised, and the rising of the printed circuit board is stopped immediately before the molten solder leaves the printed circuit board. A method of partially soldering a printed circuit board, wherein the molten solder is slowly lowered and separated from the soldered part of the printed circuit board.

The present invention also includes a step of applying a flux to a large number of soldering groups formed by aggregating soldered portions of a printed circuit board;
Drying the flux applied to the soldering group;
Cleaning the inside of the jet nozzle by jetting molten solder from the jet nozzle and heating the jet nozzle;
The jet nozzle is aligned with the soldering group of the printed circuit board, and the printed circuit board is stopped above the jet nozzle so that the molten solder spouted from the nozzle does not flow out between the printed circuit board and the jet nozzle due to surface tension. The step of:
A step of jetting molten solder from a jet nozzle until it sufficiently comes into contact with the printed circuit board to attach the molten solder to a soldering portion of a soldering group;
A step of raising the printed circuit board while the molten solder is jetted from the jet nozzle and stopping the rising of the printed circuit board immediately before the molten solder leaves the printed circuit board;
A step of slowly lowering the molten solder jetted from the jet nozzle to a predetermined position to release the molten solder from the soldered portion of the printed circuit board;
A step of moving the printed circuit board from the position of the jet nozzle after lowering the molten solder in the jet nozzle to the level of the molten solder in the solder bath;
A method for partially soldering a printed circuit board, comprising:

  In the partial soldering method of the present invention, when a gap is provided between the printed circuit board and the jet nozzle when the printed circuit board is stopped above the jet nozzle, the molten solder is jetted from the jet nozzle to adhere the solder to the soldering portion. Then, even if the printed circuit board is moved, the solder does not stick to the printed circuit board. This gap is a gap in which the molten solder jetted from the jet nozzle does not flow out of the jet nozzle due to the surface tension of the molten solder after contacting the printed circuit board. The gap is appropriately determined depending on the composition of the solder, but 0.1 to 1.0 mm is appropriate, and 0.7 mm is suitable for Sn-free lead-free solder.

  Further, in the present invention, the jet height when the printed circuit board is brought into contact with the molten solder jetted from the jet nozzle, that is, the height when the molten solder is jetted without placing the printed circuit board above the jet nozzle. For lead-free solder, 4-7mm is appropriate. Then, when the printed board is placed above the jet nozzle, molten solder is jetted in such a state that the jet height is reached to bring the molten solder into contact with the printed board. Thereafter, the printed circuit board is raised and stopped at a predetermined position. This predetermined position means that when the printed circuit board is lifted with the solder attached to the printed circuit board, the molten solder extends without breaking immediately and rises to a certain height. Cut away from the soldering part. In the present invention, the rising of the printed circuit board is stopped immediately before the molten solder is cut from the soldering portion of the rising printed circuit board. The height until the molten solder is cut, that is, the distance between the upper end of the jet nozzle and the soldered portion of the printed circuit board is suitably 4 to 7 mm.

  And after stopping a raise of a printed circuit board, the jet of the molten solder currently spouted from a jet nozzle is lowered slowly, and a molten solder is separated from a printed circuit board. Then, no bridge is generated in the soldering group of the printed circuit board.

  According to the present invention, when soldering a printed circuit board, no oxide or the like adheres to the soldered portion, so that the appearance after soldering is excellent, and the occurrence of wiggles and bridges in the soldered portion, and unsoldered Not only occurs, but also the solder completely penetrates into the through hole, so that a soldered portion having excellent reliability can be obtained.

  The partial soldering method of the present invention will be described below with reference to the drawings. FIGS. 1-8 demonstrates the process of the partial soldering method of this invention.

Figure 1: Flux application process;
The printed circuit board 1 is transported to the fluxer F by a transport device (not shown) and placed on the peripheral wall 12 of the fluxer F. In the fluxer F, a large number of peripheral walls 12... Are installed at positions corresponding to the soldering group of the printed circuit board 1, and spray nozzles 13 are attached in the peripheral walls. In the fluxer used in the present invention, a partition wall 14 having a lower height than the peripheral wall is erected on the inner side of the peripheral wall 12, and an exhaust duct 15 is connected to the partition wall 14.
When the spray is sprayed in the form of mist from the spray nozzle 13, the mist flux 16 adheres only to the soldering group, and the excess mist flux is discharged from the exhaust duct 15 and does not adhere to unnecessary portions of the printed circuit board. .

Figure 2: Flux drying process;
The printed circuit board on which the flux is applied only to the soldering group is transported to the drying device D by a transport device (not shown) and placed on the enclosure 17 of the drying device. The drying apparatus D is installed in a place where a large number of enclosures 17 coincide with the soldering group of the printed circuit board 1, and a hot air duct 18 is connected to the enclosure. In the drying apparatus used in the present invention, a partition wall 19 having a height lower than that of the enclosure 17 is erected on the inner side of the enclosure 17, and an exhaust port is opened in a part of the enclosure. The hot air sent from the hot air duct 18 strikes the soldering group and dries the solvent in the flux applied to the soldering group. Then, the hot air sent from the hot air duct 18 and hitting the soldering group of the printed circuit board is discharged from the exhaust port.

Figure 3: Jet nozzle cleaning and heating process;
Clean and heat the jet nozzle before soldering the printed circuit board. In the solder bath S, a large number of jet nozzles 20, which have the same shape as the soldering group, are installed at positions corresponding to the soldering group of the printed circuit board. A jet nozzle suitable for use in the present invention is shown in FIG. An outflow portion 22 for molten solder is formed below the one wall surface 21 of the jet nozzle 20. A flow duct 23 whose upper end is located slightly below the upper end of the jet nozzle is installed in the jet nozzle, and a gap 24 is provided between the wall surface 21 where the outflow portion is formed and the flow duct 23. . The flow duct 23 is connected to a jet pump installation section (not shown) in the solder bath S. The cleaning and heating of the jet nozzle can be performed before the printed circuit board reaches the solder bath or at a position where the printed circuit board is transported to the solder bath and the jet nozzle and the soldering group of the printed circuit board are aligned. The molten solder is jetted from the jet nozzle while stopped at a high position above. That is, the molten solder 7 is jetted from the jet nozzle 20 without bringing the molten solder into contact with the printed circuit board.
This is because when the molten solder is lowered to the molten solder liquid level in the solder bath after the previous soldering of the printed circuit board, oxides etc. are adhered to the inside of the jet nozzle, and the next printed circuit board is soldered as it is. If it does, an oxide etc. will adhere to a printed circuit board with a jet of molten solder. Therefore, before soldering the printed circuit board, molten solder is jetted from the jet nozzle, and oxides and the like adhering to the inside of the jet nozzle are cleaned with the molten solder jet. At this time, since the jet nozzle is heated by the molten solder jetted, the temperature of the molten solder jetted from the jet nozzle thereafter does not drop.

Fig. 4: Printed circuit board position setting process;
When the jet nozzle has been cleaned and heated, the molten solder jet is lowered to a position slightly higher than the duct 20. Thus, if the molten solder is raised in the jet nozzle before the arrival of the printed circuit board, the temperature of the jet nozzle does not decrease. Thereafter, the printed circuit board is conveyed to a predetermined position on the jet nozzle of the solder bath. The predetermined position referred to here is to match a number of jet nozzles and the soldered group of the printed board, and to stop the jet nozzle and the printed board with a certain gap. The fixed gap is a gap in which molten solder does not flow out between the jet nozzle and the printed board due to its own surface tension when molten solder is jetted from the jet nozzle and applied to the soldering group of the printed board. . The gap is suitably 0.1 to 1.0 mm, although it depends on the solder composition, that is, the surface tension inherent to the solder. If the gap between the jet nozzle and the printed circuit board is increased, the molten solder will flow out of the jet nozzle when the molten solder is jetted from the jet nozzle, and the surface mount component is mounted near the soldering group. Solder adheres to unnecessary parts such as connectors. However, if the printed circuit board is placed directly on the jet nozzle without providing a gap between the jet nozzle and the printed circuit board, the molten solder is jetted to adhere the solder to the soldering part, and then the molten solder jet is stopped. When the printed circuit board is moved from the jet nozzle after that, the solder having the same shape as the jet nozzle is stuck to the printed circuit board. This is because when the molten solder in the jet nozzle is lowered, the upper end of the jet nozzle cools, and the remaining solder sticks to the printed circuit board.

Figure 5: Solder adhesion process;
The height of the jet of the molten solder 7 from the jet nozzle 20 is increased so that the solder adheres to the soldering portion. By increasing the jet height of the molten solder, the molten solder penetrates sufficiently into the through-hole, and the molten solder is completely wetted with the soldered parts and leads of the printed circuit board, generating unsolder. Disappear. The height of the jet at this time is about 3 mm from the upper end of the jet nozzle when the printed circuit board is not placed above the jet nozzle.

Figure 6: Raising process of printed circuit board;
While the molten solder is jetted from the jet nozzle, the printed circuit board is raised to a predetermined height, that is, a height just before the molten solder adhering to the printed circuit board is cut from the printed circuit board (arrow A), and the printed circuit board is raised at that position. To stop. The predetermined height for raising the printed circuit board at this time is 4 to 7 mm, although it varies depending on the type of solder.

Figure 7: Molten solder removal process;
When the printed circuit board is raised to a predetermined position and stopped, the molten solder 7 jetted from the jet nozzle is slowly lowered (arrow) and separated from the soldering portion. At this time, the descending speed of the molten solder is set so as not to cause wiggles and bridges in the soldered portion.

Figure 8: Printed circuit board moving process;
After the molten solder is released from the soldering portion of the printed circuit board 1, the molten solder is lowered to the molten solder liquid level in the solder bath S. When the molten solder adhering to the soldering portion is completely solidified, the printed circuit board is transported to a cooling area (not shown), where it is completely cooled.

  The multilayer printed circuit board used for the video game control panel was soldered by the partial soldering method of the present invention. On the printed board, electronic parts such as PGA and dual-in package were mounted on the front surface, surface mounted parts and connectors were attached to the back surface, and a number of through holes were drilled. PGA and dual-in package leads are inserted from the front side to the back side of the printed circuit board, and a large number of soldering parts form a soldering group on the back side.

  The printed circuit board is transported by the transport device, the flux is applied by the fluxer, and the solvent of the flux is dried by the hot air of the drying device. During this time, the molten solder is jetted for 1 second in the solder bath to clean the jet nozzle and heat the jet nozzle. It was. After that, the jet flow from the jet nozzle is lowered by 1.5 mm from the upper end of the jet nozzle and set in a standby state. After the printed board is transported to the solder bath, the gap between the jet nozzle and the printed board is set to 0.5 mm and the printed board is stopped. It was.

  Next, molten solder was jetted from the upper end of the jet nozzle to a height of 3.0 mm from the jet nozzle to a height of 3.0 mm, and the molten solder was jetted into the soldering group of the printed circuit board for 2 seconds to adhere the solder to the soldered portion.

  The printed circuit board is raised to a height of 5 mm from the upper end of the jet nozzle. At this time, the molten solder adhering to the soldering portion of the printed circuit board is not cut off from the printed circuit board. Thereafter, the molten solder jet is slowly lowered to cut the molten solder from the soldered portion of the printed circuit board. The printed circuit board was transported to a cooling device and sufficiently cooled.

  When the printed circuit board soldered by the soldering method of the present invention was observed, there was no adhesion of oxides, etc. to the soldered part, no occurrence of wiggle, bridge, unsolder in the soldered part, and Solder completely penetrated the through hole. On the other hand, when the same printed circuit board was soldered by a conventional soldering method, oxides and the like were adhered to the soldered part, and not only tsura, bridges and unsoldered were generated, but also through holes. There was not enough solder inside.

Flux application process of the partial soldering method of the present invention Flux drying step of the partial soldering method of the present invention Jet nozzle cleaning / heating process of the partial soldering method of the present invention Printed circuit board position setting step of the partial soldering method of the present invention Solder adhesion process of the partial soldering method of the present invention Printed circuit board raising step of partial soldering method of the present invention Cutting step of molten solder of partial soldering method of the present invention Printed circuit board moving step of the partial soldering method of the present invention The perspective view of the jet nozzle used for the partial soldering method of this invention Back side of printed circuit board Top view of solder bath used for partial soldering method Flux process of conventional partial soldering method Preheating process of conventional partial soldering method Printed circuit board position setting process of conventional partial soldering method Solder attachment process of conventional partial soldering method Printed circuit board moving process of conventional partial soldering method Perspective view of jet nozzle used in conventional partial soldering method

Explanation of symbols

1 Printed circuit board 7 Molten solder 20 Jet nozzle

Claims (3)

Before soldering the printed circuit board, the molten solder is jetted from the jet nozzle to remove the oxide, and then the molten solder jet is lowered to the nozzle position. Stop the jet nozzle and the printed circuit board with a certain gap, increase the jet height of the molten solder from the jet nozzle and attach the solder to the soldering part, then raise the printed circuit board and melt it Partial soldering of a printed circuit board characterized in that the rising of the printed circuit board is stopped immediately before the solder leaves the printed circuit board, and then the molten solder jetted from the jet nozzle is lowered and separated from the soldered portion of the printed circuit board. Method. A process of applying flux to a large number of soldering groups formed by aggregating soldered portions of a printed circuit board;
A step of drying the flux applied to the soldering group; a step of jetting molten solder from the jet nozzle to clean the jet nozzle and heating the jet nozzle;
The jet nozzle and the soldering group of the printed circuit board are matched, and the printed circuit board is placed above the jet nozzle so that molten solder spouted from the jet nozzle does not flow out between the printed circuit board and the jet nozzle due to surface tension. The process of stopping;
A process in which molten solder is jetted from a jet nozzle until it is sufficiently in contact with the printed circuit board, and the molten solder is attached to the soldering portion of the soldering group;
A step of raising the printed circuit board while the molten solder is jetted from the jet nozzle and stopping the rising of the printed circuit board just before the molten solder leaves the printed circuit board;
The process of lowering the molten solder sprayed from the jet nozzle to a predetermined position and releasing the molten solder from the soldering portion of the printed circuit board; the molten solder in the jet nozzle is lowered to the level of the molten solder in the solder bath And a step of moving the printed circuit board from the position of the jet nozzle. 2. The method for partially soldering a printed circuit board according to claim 1, wherein a gap between the printed circuit board and the jet nozzle when the printed circuit board is stopped above the jet nozzle is 0.1 to 1 mm.

Images