JP3956250B2 - Jet solder bath - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a jet solder bath suitable for soldering a printed circuit board, particularly a printed circuit board mounted with a chip component, with molten solder.
[0002]
[Prior art]
Recent electronic devices have become very small due to the tendency to be light, thin, and small, and the electronic components used therefor have also become smaller. This small electronic component is called a chip component. In general, the chip component is mounted on a printed board by soldering with a solder paste. This solder paste is made by kneading powder solder and cream-like flux, but it takes a lot of work to manufacture powder solder and kneading with flux, so the material cost becomes very expensive. ing. Therefore, when chip components are mounted on a printed circuit board of a relatively inexpensive home appliance such as a television, a video, and a radio cassette player, soldering using a solder paste increases the price. Therefore, when chip components are mounted on a printed circuit board of home appliances, the material cost is low, and the immersion soldering method that enables mass production is used.
[0003]
The immersion soldering method is a method in which a printed circuit board is soldered by an automatic soldering apparatus in which processing devices such as a fluxer, a preheater, a jet solder bath, and a cooler are installed.
[0004]
Here, the soldering of the printed circuit board by the automatic soldering apparatus will be briefly described.
[0005]
In automatic soldering equipment, flux is applied with a fluxer, preheated with a preheater, molten solder is applied in a jet solder bath, and molten solder is attached to the printed circuit board with a cooling machine while the printed circuit board is being transferred by a transfer device of the automatic soldering apparatus. Cooling is to be performed.
[0006]
A primary solder nozzle for jetting rough waves and a secondary jet nozzle for jetting gentle waves are installed in the jet solder tank of the automatic soldering apparatus. This rough wave of the primary jet nozzle is to make the molten solder penetrate into the place where the molten solder is difficult to penetrate to eliminate the unsolder, and the gentle wave of the secondary jet nozzle is formed by the rough wave of the primary jet nozzle. It is intended to correct bridges and icicles.
[0007]
By the way, when the chip part is mounted on the soldering surface of the printed circuit board and soldered by the dipping method, the chip part is a rectangular parallelepiped, so the pattern that is the soldered part of the printed circuit board and the electrode part of the chip part are at the right corner End up. When the printed circuit board with the soldered portion of the printed circuit board thus formed in the corner is soldered in the jet solder bath, the molten solder jetted from the nozzle may not enter the corner and become unsoldered. Therefore, in soldering a printed circuit board on which chip components are mounted, a jet solder bath that creates rough waves is always necessary.
[0008]
Conventionally, many jet nozzles that generate rough waves have been proposed. Examples of creating rough waves are those in which the oscillator is rotated or reciprocated by external power in the nozzle (Japanese Examined Patent Publication No. 62-46270, Japanese Examined Patent Publication No. 5-85262), and a porous plate in the nozzle. (No. 63-150636), and both ends of the nozzle held by a tension spring (No. 1-59073).
[0009]
[Problems to be solved by the invention]
Although these jet solder baths are effective in eliminating unsoldering on printed circuit boards on which chip components are mounted, they cause another problem. For example, a nozzle that creates a rough wave by moving an idler with power from the outside installs the motor near a hot solder bath, which shortens the life of the motor or changes the motor speed due to changes in the temperature of the solder bath. Sometimes the jet state changed.
[0010]
Also, in a jet solder bath with a perforated plate installed in the nozzle, solder oxide easily adheres to the hole in the perforated plate, and the size of the hole changes during long-term use, so the jet state also changes. There was a thing.
[0011]
The jet nozzle that holds the floating body installed in the nozzle with a spring (hereinafter referred to as a spring floating jet nozzle) is moved by the solder that the floating body constantly jets, so that the oxide is less likely to adhere to the floating body, Moreover, since no power is required from the outside, there is an excellent feature not found in other jet solder baths in that the jet state does not change due to the change in the rotational speed of the motor.
[0012]
However, the conventional spring floating jet solder bath does not have enough solder penetration into the corners of the chip parts, and it generates unsolder on a printed circuit board on which the chip parts are mounted at a high density as in recent times. There were rarely. The present invention is a spring floating jet nozzle that has a jet solder bath that allows molten solder to enter the corners of chip parts more easily than conventional ones, and can completely eliminate unsolder even on high-density printed circuit boards. Is to provide.
[0013]
[Means for Solving the Problems]
As a result of earnest research on the cause of unsoldering in the conventional spring floating jet nozzle, the present inventor has a simple rod shape, so that the molten solder flowing near the floating body has little influence on the floating body. As a result, it was found that the waves jetted from the nozzle were not so rough.
[0014]
Therefore, the present inventor has completed the present invention paying attention to the fact that the molten solder wave jetted from the nozzle is greatly roughened if the influence of the molten solder on the floating body can be increased.
[0015]
In the present invention, a primary jet nozzle and a secondary jet nozzle are installed, and in the primary jet nozzle, a rod-like floating body is installed in the nozzle in the longitudinal direction, and both ends of the floating body are held by springs. In the jet solder bath, the floating body has a large number of irregularities that can move the floating body greatly by varying the momentum of the molten solder passing through both sides of the floating body, and is alternately attached to both sides in the width direction of the nozzle. It is a jet solder bath characterized by being made.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
The unevenness attached to the floating body in the present invention is the one in which grooves are alternately engraved on both sides of the rod-shaped floating body as shown in FIGS. 1 to 4, or the rod-shaped floating body is alternately staggered as shown in FIGS. A bent one can be used. When the rod-shaped floating body is bent in a staggered manner, the crests protruding on one side are convex, the troughs retracted on one side are concave, and the crests and troughs are staggered on both sides in the width direction of the nozzle. Is formed.
[0017]
In the present invention, the spring that holds the floating body may be a tension spring that stretches the floating body, or a leaf spring that restrains the movement of the floating body in the vertical direction and can only move laterally. In the case of using a leaf spring, the corrugated leaf spring may be set in the vertical direction, or one end of the plate spring in the vertical direction may be set in a free state to perform only the lateral movement.
[0018]
The floating body used in the present invention may have a round cross section, but may have any other cross section such as a rectangle, an ellipse, a triangle, and a diamond.
[0019]
【Example】
The present invention will be described below with reference to the drawings. 1 is a partially broken perspective view of a primary jet nozzle of a jet solder bath of the present invention, FIG. 2 is an enlarged perspective view of a floating body used in the jet solder bath of the present invention, FIG. 3 is a plan view thereof, and FIG. FIG. 5 is a plan view of a floating body used in another embodiment, and FIG.
[0020]
A primary jet nozzle 1 and a secondary jet nozzle (not shown) are installed in the jet solder tank. The nozzle 2 of the primary jet nozzle 1 is composed of a pair of nozzle plates 3 and 3 on both sides in the longitudinal direction and a pair of side plates 4 and 4 on both ends thereof.
[0021]
The side plates 4 and 4 are formed with holes 5 and 5 at a position slightly lower than the upper end of the nozzle, that is, inside the nozzle. On the outside of the side plate 4 that coincides with the hole, spring cases 7 and 7 are installed via attachment plates 6 and 6.
[0022]
The spring case 7 is U-shaped and the open end of the spring case 7 coincides with the hole 5, and a hole is drilled in the other end. A screw 8 having a diameter slightly smaller than the diameter of the hole slides in the hole. It is inserted freely. A tension spring 9 is engaged with the tip of the screw 8, and a positioning nut 10 is screwed into the outside of the spring case 7.
[0023]
A floating body 11 is installed in the nozzle 2 in the longitudinal direction. Both ends of the floating body 11 are inserted into the spring case 7 through the holes 5 of the side plate 4, and the end of the floating body 11 is engaged with the tension spring 9. In the floating body 11, kerfs 12 are formed alternately in the width direction of the nozzle.
[0024]
Next, the jet state of the jet solder tank of the present invention configured as described above will be described.
[0025]
When the molten solder is jetted from below the nozzle 2, the molten solder passes through both sides of the floating body 11 and flows upward. The flowing molten solder passes through the inside of the groove 12 of the floating body 11 and along a round portion other than the groove. At this time, the molten solder passing through the groove 12 has a speed higher than that of the molten solder passing along the rounded portion, so that the molten solder jets higher than the molten solder passing along the rounded portion.
[0026]
Further, the molten solder that passes through the groove 11 and the molten solder that passes along the round portion have different momentums, and therefore the force that pushes the floating body laterally is not uniform. Since this occurs on both sides of the floating body, the floating body is moved more than a conventional simple rod-shaped body, and the molten solder is greatly roughened by the large movement.
[0027]
Here, an experiment in which a printed circuit board is soldered in a jet solder bath provided with a jet solder bath of the present invention and a conventional spring floating jet nozzle will be described. The printed circuit board to be soldered has 2,000 soldered portions and 200 chip components mounted thereon, and 100 printed circuit boards were soldered. Therefore, 200,000 soldering locations of 100 printed circuit boards are provided. The jet soldering bath of the present invention is formed by alternately engraving grooves having a depth of 2 mm and a width of 5 mm on both sides at 5 mm intervals on a round bar having a nozzle width of 12 mm and a floating body of 6 mm in diameter. The jet solder bath of the comparative example is a round bar having a nozzle width of the primary jet nozzle of 8 mm and a floating body of 3 mm in diameter.
[0028]
As a result of the experiment, in the jet solder bath of the present invention, there were 52 unsoldered portions, that is, 52 / 200,000, and 0.0026%. However, in the jet solder bath provided with the conventional spring floating jet nozzle, there are no unsoldered portions. 144 pieces, that is, 144 / 200,000 is 0.0072%, and it can be seen that the jet solder bath of the present invention has an extremely low defect rate compared to the conventional one.
[0029]
【The invention's effect】
As described above, the jet solder bath according to the present invention has the reliability that even when soldering a printed circuit board on which chip parts are mounted at high density, molten solder can be infiltrated into the corners of the chip parts and unsolder can be extremely reduced. It is possible to obtain an excellent soldering part.
[Brief description of the drawings]
FIG. 1 is a partially broken perspective view of a primary jet nozzle of a jet solder bath of the present invention. FIG. 2 is an enlarged perspective view of a floating body used in the jet solder bath of the present invention. FIG. 3 is a plan view of FIG. 2 is a side sectional view of FIG. 2. FIG. 5 is a plan view of a floating body used in another embodiment. FIG. 6 is a side sectional view of FIG.
DESCRIPTION OF SYMBOLS 1 Primary jet nozzle 2 Nozzle 3 Nozzle plate 4 Side plate 5 Hole 7 Spring case 8 Adjustment screw 9 Spring 11 Free moving body 12 Groove

Claims (3)

  In a jet solder bath in which a primary jet nozzle and a secondary jet nozzle are installed, a rod-like floating body is installed in the nozzle in the longitudinal direction in the nozzle, and both ends of the floating body are held by springs The floating body is provided with a large number of irregularities on both sides in the width direction of the nozzle, which can move the floating body greatly by changing the momentum of the molten solder passing through both sides of the floating body. A jet solder bath characterized by  2. The jet solder bath according to claim 1, wherein the irregularities attached to the floating body are grooves formed by alternately engraving both sides of the floating body.  The jet solder bath according to claim 1, wherein the irregularities attached to the floating body are peaks and valleys formed by alternately bending the floating bodies.

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