JPH0673743B2 - Soldering method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a soldering method, and more particularly to a soldering method in which a soldering failure is not caused when separating a soldered object from molten solder ejected from a nozzle. Regarding

2. Description of the Related Art A jet soldering device that melts and stores solder in a solder bath equipped with a nozzle and ejects this molten solder from the nozzle is, for example, a lead for an electrical component that is intended to be mounted on a printed circuit board. Is widely used for soldering to the soldering land of the circuit pattern of the printed circuit board.

In this jet soldering device, for example, as shown in FIG. 2, a nozzle 2 made of metal is provided in a solder bath 1, and molten solder contained in the solder bath 1 is jetted from the nozzle 2 by an impeller 3. When attempting to solder the above-mentioned printed circuit board with this device, the printed circuit board a is carried in and brought into contact with the molten solder jetted out in a slightly raised state, and the printed circuit board is placed in the same posture. It is moved forward one after another so that the entire surface thereof is brought into contact with the molten solder in sequence.

By the way, the nozzle has a nozzle so that the printed circuit board can make good contact with the molten solder ejected from here.
2a metal wave matching plate on both sides of the printed circuit board moving direction
b and 2c are provided, and the waves of the molten solder ejected by these are arranged. To such a wave plate, for example, as shown in FIG. 2, a carry-in side wave plate 2b of a printed circuit board a is attached so that its tip is inclined downward, and a carry-out side wave plate 2c of the printed circuit board is attached. There is a so-called one-flow type that is composed of a horizontal plate portion and a vertical plate portion at the tip. In the case of this type, the molten solder immediately flows down on the carry-in side wave plate 2b, but on the carry-out side wave plate 2c side, this wave plate causes the nozzle 2
The molten solder spouted from is held on the wave-regulating plate 2c for a while while flowing without flowing down immediately, so that the molten solder has a quiet appearance close to a laminar flow. Therefore, as compared with the nozzle 2'having the wave-regulating plates 2'b, 2'c inclined downward on both sides of the ejection port 2'a as shown in FIG. 3, the solder attached to the soldering portion has a flow of molten solder. It is difficult to cause defective soldering such as flicker when separated from each other, or fusion of solders adhering to adjacent soldering portions to each other to form a solder bridge.

However, even in this case, the occurrence of defective soldering cannot be completely eliminated. One of the reasons for this is, for example, that the temperature of the molten solder that is temporarily held on the unloading side wave plate 2c side is longer than that of the molten solder that immediately flows down and stays in the air. For example, it may be 10 ° C lower than 250 ° C of the molten solder, and in this case, the flux is applied in the previous step, preheated, and the preheated side 100 to 140
It is heated to ℃, and the opposite side is 80 to 100 ℃ Even if the printed circuit board comes in contact with solder of 250 ℃ on the loading side wave plate 2b, it is about 10 ℃ lower on the output side wave plate 2c. Since it contacts solder of 240 ℃, when the solder of low temperature comes into contact with the solder of high temperature mentioned above and the soldered part is separated from the molten solder as it is, the temperature of the printed circuit board itself is much higher than 240 ℃. When the solder attached to the soldered part is cut from the flow of solder because of its low temperature, the temperature drop at the end of the solder becomes large and the end becomes trailing, which causes flicker and may occur between adjacent soldered parts. This is because they may be fused to form a solder bridge.

When flicker and solder bridges are generated in this way, resulting in defective soldering, these defective points must be manually corrected, which is a problem in terms of work efficiency.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention As described above, the conventional soldering method using a nozzle is defective in soldering such as flicker and solder bridge particularly on the side of the molten solder ejected from which the object to be soldered is separated. However, there is a problem that it may occur, and improvement thereof has been desired.

Means for Solving the Problems In order to solve the above problems, the present invention provides a channel-shaped flow passage at a rear edge in a moving direction of an object to be soldered at an ejection port for ejecting molten solder, An opening control plate having at least a tip portion whose rotation is freely adjustable is provided at the front edge, and the length of the channel-like flow passage for flowing the molten solder ejected from the ejection port is 50 mm or more, and the body to be soldered. The present invention provides a soldering method characterized by performing the soldering by setting the flow rate of the molten solder at a position away from the circulated molten solder to 15 cm / sec to 40 cm / sec.

Next, the present invention will be described in detail.

In the soldering method of the present invention, any soldering device capable of flowing the molten solder in a direction opposite to the carrying-in direction of the object to be soldered and contacting it, so-called a soldering device capable of countercurrently contacting the soldered object with the molten solder is used. it can. For example, there is a device for ejecting molten solder from a nozzle and flowing the molten solder through a flow passage provided in the nozzle in a horizontal direction or inclined downward.

When an object to be soldered, such as a printed circuit board, is carried in by a conveyor and brought into contact with the molten solder fluidized in this manner, the soldered portion of the printed circuit board gets wet with the molten solder. And when the printed circuit board is conveyed by the conveyor and separated from the molten solder, the molten solder wet to the soldering part is cut from the flow of the molten solder, and at this time, the cut end is the flow of the molten solder and the method of transferring the printed circuit board. Since they are reversed, they are oriented in the direction of this flow and do not come into contact with each other, so that a bridge can be prevented. To do this effectively, the flow of molten solder is 15 cm
/ Sec or more, preferably 15 cm / sec to 40 cm / sec. Particularly preferred is 18 cm / sec to 28 cm / sec. This molten solder is preferably made into a laminar flow, and for that purpose, the flow length of the molten solder is preferably 50 mm or more. In the case of violent turbulence, the above bridge may occur, and also when the flow rate of molten solder is less than 15 cm / sec,
This may result in the above bridge.

The flow rate of the molten solder can be set to the above value by, for example, introducing the jetted molten solder into a channel-shaped flow passage and squeezing the flow passage.

Thus, the flow velocity of the molten solder at the position away from the molten solder on the printed circuit board is important, but when the printed circuit board comes into contact with the molten solder, the temperature of the molten solder is 240 to 250 ° C.
As a result, the substrate warps convexly toward the molten solder, and the contact area of the molten solder with respect to the substrate increases so that there is no warp in the substrate. Also in this case, the flow rate of the molten solder at the shifted position is set to the above flow rate.

Operation Since the molten solder was made to flow in the direction opposite to the conveying direction of the body to be soldered and brought into countercurrent contact with the body to be soldered, when the molten solder wet to the soldering part is cut from the flow of the molten solder, the cut end Are controlled by the flow and do not fuse together.

Embodiment Next, one embodiment of the present invention will be described with reference to FIG.

In the figure, 11 is a soldering device.
The nozzle 13 is provided in the solder bath 12, and the molten solder contained in the solder bath 12 is ejected from the nozzle 13 by an impeller 14 driven by a motor (not shown).

The nozzle 13 has an elongated rectangular cross section, and an opening control plate 13b is provided along the front edge of a nozzle body 13a whose longitudinal section is formed in a shape in which the rear side is widened, while the rear side of the nozzle body 13a is provided. A channel-shaped flow passage 13c having side walls on both sides is provided along the edge. The opening control plate 13b,
The lower control plate 13b-1 is rotatably attached to the front edge of the nozzle body 13a, and the upper control plate 13b-2 is rotatably attached to the lower control plate. The discharge amount from the nozzle 13 can be controlled by controlling the. Further, the flow passage 13c,
The flow passage bottom plate 13c-1 is rotatably attached to the rear edge of the nozzle body 13a, and the side wall plates 13c-2 and 13c-3 (not shown) of the flow passage bottom plate 13c-1 are freely movable. It can be adjusted.

Next, the operation of this embodiment will be described.

In the apparatus shown in FIG. 1, the flow passage bottom plate 13c-1 is set substantially horizontally, the side wall plates 13c-2, 13c-3 of the flow passage are positioned to form the flow passage 13c, and the flow passage 13c is formed. 13c side wall plate 13
The position of the upper control plate 13b-2 is determined along the upper edges of c-2 and 13c-3.

Next, the impeller 14 is operated to eject the molten solder of approximately 250 ° C. from the nozzle 13. The ejected molten solder is ejected through an opening defined by the opening control plate 13b and the flow passage 13c, further flows through the flow passage 13c, and flows down from the tip to the solder bath 12. In this state, a conveyor (not shown) is operated to bring in the printed circuit board a, which has been preheated with flux and preheated, and is brought into contact with the flowing molten solder. The part to be soldered gets wet, and this is separated from the flow of molten solder as the printed circuit board is conveyed by the conveyor. At this time, the flow rate of the molten solder at the position to be separated is set to 18 to 28 cm / sec, and by setting the molten solder in the laminar flow state, the cut end of the molten solder attached to the soldering portion is the flow of the molten solder. Oriented in the direction, the tip of which is torn off by the molten solder and carried away with the molten solder. This flow velocity is measured by immersing the impeller blades in a flow of molten solder, rotating the impeller, and measuring the number of revolutions thereof, as described in JP-A-61-80056. To be done.

In the above, the flow rate α of the flow passage bottom plate 13c-1 is 50 mm to 300 mm.
Is preferable, and 100 mm or more is preferable for a 260 mm × 300 mm VTR printed circuit board. In this way, the length of the flow path is required because the printed circuit board warps when it comes into contact with the molten solder, and when the soldering part separates from the molten solder, its position is on the side of the upper control plate 13b-2. This is because as a result of approaching, the flow rate of the molten solder becomes smaller and the above-mentioned flow rate of 15 cm / sec cannot be obtained. The reason why the flow velocity on the side of the upper control plate is low is that the flow section of the molten solder is large and there is a flow resistance to the upper control plate.

When the molten solder was ejected and circulated as described above, the side wall plate and the upper control plate were at the same level position, so the molten solder overflowed over these side wall plates and was generated on the surface. The oxide film, particularly the oxide film generated in the slow-flowing molten solder near the upper control plate, is removed from the flow passage 13c, so that better soldering can be performed. Incidentally, when the upper control plate 13b-2 is at a position lower than the side wall plates 13c-2, 13c-3, the molten solder collects on the upper control plate side,
Here, it is easily oxidized.

Next, the experimental results based on the method of the present embodiment will be described in comparison with the comparative example.

In the experiment, using an automatic soldering device manufactured by Tamura Seisakusho, conveyor speed 1.3 m / min, conveyor inclination angle 7
Degree, flux (Solder Light CF-210V (manufactured by Tamura Kaken Co., Ltd.)) soldering surface temperature (preheat temperature) of the printed circuit board 90 ° C, soldering temperature 240 ° C, VTR board as a test printed circuit board The soldering conditions using (Soldering point 2000 per sheet) were adopted.

Under the above conditions, the nozzle shown in FIG. 1 (Example, where α is
170 mm), the nozzle shown in FIG. 2 (Comparative Example 1), and the nozzle shown in FIG. 3 (Comparative Example 2) were used for soldering, and the results of measuring the number of solder bridges generated per board were shown as 4th. Shown in the figure. Here, the horizontal axis indicates the type of nozzle, but for the nozzles of the examples, the test numbers in the following table are shown, and the numerical values corresponding to these numbers are the molten solder in the flow passage when the nozzles of the examples are used. The speed (cm / sec) of A is set at A (the tip of the flow passage), B (the position where the soldering part separates from the molten solder), and C (the vicinity of the upper control plate) in FIG. It was measured by the method described in the publication. In the case of the nozzles of Comparative Examples 1 and 2, the state of the molten solder ejected was a general solder wave state.

From the results shown in FIG. 4, all the examples having B positions of 15 cm / sec or more had the number of bridges of 5 or less, while those of less than 15 cm / sec and the comparative example were all. It turns out that it is 10 or more.

The α can be adjusted by making the tip length of the upper control plate 13b-2 and the tip of the flow passage bottom plate 13c-1 stepwise or low, and the tip of the flow passage bottom plate has grooves on both sides. It is also possible to provide an auxiliary plate that can be pulled out, and to adjust by this. Further, the vertical cross-sectional shape of the nozzle body 13a may be flared on both sides, or the opposite may be flared.

EFFECTS OF THE INVENTION As described above, according to the present invention, a channel-shaped flow passage is provided at the rear edge of the ejection port, and an opening control plate having at least the tip of which is rotatably adjustable is provided at the front edge of the ejection port. Flow in the direction opposite to the direction of the body to be soldered, the length of the channel-like flow path is 50 mm or more, and the flow rate of molten solder at the position where the body to be soldered separates is 15 cm / sec to 40 c
Since it is set to m / sec, the soldered part of the body to be soldered is separated from the smooth flow of the molten solder, and the cut edges are also controlled by the flow of the molten solder and do not fuse to each other, so a solder bridge is generated. In addition, since the generation and retention of solder oxide is small, the soldering failure due to this can be reduced, and furthermore, flicker is less likely to occur, for example, the soldering failure of the printed circuit board can be significantly reduced, and the soldering productivity can be reduced. Can be significantly reduced.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional explanatory view of a soldering device used in one embodiment of the method of the present invention, FIGS. 2 and 3 are schematic cross-sectional explanatory views of a conventional soldering device, and FIG. It is a graph which shows the result of having measured the number of defective soldering by performing soldering using a soldering device. In the figure, 11 is a soldering device, 12 is a solder bath, 13 is a nozzle, 13a is a nozzle body, 13b is an opening control plate, 13b-1 is an upper control plate, 13b-2 is a lower control plate, 13c is a flow passage, 13c-1 is a bottom plate of the flow passage, and 13c-2 and 13c-3 are side wall plates.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yuhiro Miyano 1336 Kitairi, Sayama City, Saitama Prefecture (56) References JP 59-5390 (JP, B1) JP 58-56048 Y1)

Claims (2)

[Claims] 1. An opening control plate in which a channel-shaped flow passage is provided at a rear edge in a moving direction of an object to be soldered at an ejection port for ejecting molten solder, and at least a front end of the ejection port is rotatably adjustable. Provided, the length of the channel-like flow passage for flowing the molten solder ejected from the ejection port is 50 mm or more, and the soldered body of the molten solder at a position away from the molten solder that has been circulated. A soldering method characterized in that soldering is performed by setting a flow rate to 15 cm / sec to 40 cm / sec. 2. The channel-shaped flow passage has a length of 50 mm to 30.
It is 0 mm, The soldering method of Claim 1 characterized by the above-mentioned.