JPH066025A - Solder ball removing method - Google Patents

Abstract

(57) [Abstract] [Purpose] A solder paste consisting of solder balls and flux is printed on a printed wiring board and attached, the terminals of the component are placed on it, and passed through a heating furnace with a prescribed temperature profile. Provided is a method for surely removing solder balls remaining in the vicinity of soldering without using an organic halogen-based solvent after removing the residue and the solder balls remaining in the soldered portion after reflow soldering by reflow soldering. The purpose is to [Structure] The printed wiring board 4 is horizontally moved linearly at a constant speed below the soldering surface 41, and hot water 6 having a temperature lower than the solder melting temperature and higher than the flux melting temperature is supplied to the printed wiring board 4.
Over the entire width of the roller, the roller is rotated so that the soldering surface 41 is heated and washed by spraying it obliquely from below and the soldering surface 41 of the pouring part of the hot water 6 is swept so that the brush bristles sweep in the traveling direction. The brush 7 is used for cleaning.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention prints and attaches a solder paste consisting of solder balls and flux onto a printed wiring board, mounts the terminals of components on the printed wiring board, and places it in a heating furnace having a predetermined temperature profile. The present invention relates to a method of removing residue and solder balls remaining in a soldered portion after passing and reflow soldering.

The components are mounted on a printed wiring board by soldering, but there is a step of washing flux and residue in the post-soldering step, and an organic halogen-based solvent (chlorofluorocarbon, trichloroethane) having a strong washing power is used as a washing liquid. ) Has been commonly used.

However, due to the environmental regulations of the Montreal Agreement, it is now obliged to completely abolish the use of organic halogen-based solvents that cause ozone layer depletion by the year 2000. In the future, low residue type flux will be used for soldering, and organic halogen will be used. The development of cleaning methods that do not use system solvents and the promotion of non-cleaning are required.

[0004]

2. Description of the Related Art FIG. 3 shows a reflow soldering process,
(a) is a solder printing state, (b) is a preheating state, and (c) is a solder melting state.

Conventional SMT (Surface Mount Technology)
In the manufacturing process of (1), in order to prevent deterioration of insulation resistance between terminals after reflow soldering, cleaning is performed with an organic halogen-based solvent such as trichloroethane to remove solder balls and residue.

That is, as shown in FIG. 3 (a), the solder paste 3 is printed on the connection pads 42 of the printed wiring board 4 by screen printing or the like so that the solder balls 1 having a diameter of 40 to 60 μm and the flux 2 are formed. A predetermined amount is attached, the terminal 5 of the component is placed on it, and it is put in a heating furnace and soldered.
In the pre-heating state that is performed in advance, as in
When is softened, the solder balls 1 on the edge of the piled up may fall off and may protrude from the connection pad 42.
Even in the soldering state, as shown in (c) of FIG. 3, the molten solder is completely melted on the connection pad 42, but it is spilled out from the connection pad 42 or floats on the flux 2 which has weak surface tension and is softened. The oxidized solder balls 1 that have flowed out are present in the shape of balls near the connection pads 42.

Therefore, the flux 2 and the residue are removed by cleaning, and the solder balls 1 remaining in the vicinity are also removed at the same time to prevent the insulation resistance between the terminals from deteriorating.

[0008]

However, as mentioned above, the use of organic halogen-based solvents must be abolished. Due to this, another removal method must be developed. There were problems such as.

In view of the above problems, it is an object of the present invention to provide a method for surely removing solder balls remaining in the vicinity of soldering without using an organic halogen solvent.

[0010]

As shown in the principle explanatory diagram of FIG. 1, [1] a solder paste 3 composed of a solder ball 1 and a flux 2 is printed on a printed wiring board 4 to be adhered, Is a method of removing the residue and the solder balls 1 left on the soldered portion after the terminal 5 of the above is placed on it and passed through a heating furnace having a predetermined temperature profile for reflow soldering. The plate 4 is horizontally moved linearly at a constant speed below the soldering surface 41, and hot water 6 having a temperature lower than the solder melting temperature and higher than the flux melting temperature is jetted obliquely from below in the traveling direction over the entire width of the printed wiring board 4. Let the soldering surface
Achieved by the solder ball removing method of the present invention in which 41 is heated and washed, and at the same time, the soldering surface 41 of the pouring part of the hot water 6 is cleaned by the roller brush 7 which rotates so that the brush bristles sweep in the traveling direction. To be done. [2] Also, the solder ball removing method described above using heated compressed air instead of the hot water 6 can be applied. [3] The solder ball removing method of the present invention in which the above solder removing method is repeated a plurality of times in series in the traveling direction achieves reliable removal.

[0011]

In other words, after soldering, the flux 2 serves as a binder and solidifies and adheres to the solder ball 1 after soldering. Therefore, the flux 2 is heated by the hot water 6 to be in a softened and melted state, and the solder ball 1 is caused by its flow force. Can be removed because it is made to flow out and is swept away by the roller brush 7.

Here, by jetting the hot water 6 from diagonally below the printed wiring board 4 in the traveling direction, a large landing area can be secured without lowering the flow force. That is, in order to improve the efficiency of the heating effect and the action of washing away.

If the direction of rotation of the roller brush 7 is reversed, the flow of the hot water 6 flowing on the surface is obstructed, and the area of the adhering portion is reduced, so that the heating time is shortened and the cleaning efficiency is increased. Therefore, it is important to rotate the printed wiring board 4 so that the brush bristles sweep in the traveling direction of the printed wiring board 4.

It is apparent that the same effect can be obtained by using heated compressed air, for example, steam having a predetermined temperature and pressure, instead of the hot water 6. Further, by repeating this in series a plurality of times, it can be surely removed.

Thus, according to the present invention, it is possible to provide a method for surely removing solder balls remaining in the vicinity of soldering without using an organic halogen-based solvent.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the embodiments shown in the drawings. Throughout the drawings, the same reference numerals denote the same objects. 2A and 2B show a removing apparatus according to an embodiment of the present invention, wherein FIG. 2A is a side view of the configuration, and FIG.

This embodiment is applied to a soldering process of a manufacturing line for a large-sized printed wiring board which constitutes an electronic circuit, and is a solder ball removing device which replaces a conventional cleaning device using an organic halogen-based solvent. is there.

As shown in FIG. 2 (a), the printed wiring board 4 is held inside the apparatus by holders 8 on both side edges and is moved straight at a constant speed by a belt (not shown). On the lower surface of the printed wiring board 4 and the soldering surface 41, three nozzles 9 for injecting the hot water 6 are provided upright at a predetermined interval from the rear obliquely lower side, and the roller brushes 7 are soldered on the rear surfaces of the nozzles 9, respectively. It is arranged at a position for cleaning 41, and all of these are individually driven and controlled by a controller (not shown).

The input information for the control is provided by two infrared photosensors 91, 92 mounted between the nozzles 9 and the roller brushes 7 of each set at a predetermined distance in the traveling direction. When the printed wiring board 4 is passed, ON / OFF information is generated, and the control unit drives the nozzle 9 and the roller brush 7.

This nozzle 9 is, as shown in FIG.
The injection ports 99 of about 1 mmφ are arranged in a line at intervals of 4 mm over a length of 26 cm, and the front end is inclined at an angle of 45 ° with respect to the vertical direction, and the hot water 6 of about 90 ° C and about 5 kgf / cm ² is sprayed.

The roller brush 7 is a horsehair brush having a diameter of 7 cm and a foot length of 1 cm. Initially, all the nozzles 9 and the roller brush 7 are in a stopped state, the printed wiring board 4 is conveyed by the holder 8, and when the first optical sensor 91 senses it, hot water 6 is jetted from the first nozzle 9 to be soldered. The surface 41 is heated and washed.

Next, if the optical sensor 92 is further detected,
The first roller brush 7 starts to rotate. Further, when the printed wiring board 4 advances and the next optical sensor 91 is operated at the front edge, the next nozzle 9 works to eject hot water 6, and when the optical sensor 92 also operates, the next roller brush 7 rotates. To start.

Further proceeding, the last optical sensors 91 and 92 sense and the nozzle 9 and the roller brush 7 are operated in the same manner.
These stop controls detect when the trailing edge of the printed wiring board 4 passes the position of the optical sensor 91 and stop the nozzles 9 of the set, and when the optical sensor 92 detects the passage, the set. The roller brush 7 is stopped.

Similarly, the following optical sensors 91 and 92 sequentially detect and stop the nozzle 9 and the roller brush 7. The apparatus of this embodiment can be applied to the printed wiring board 4 having a width of 10 cm to a maximum of 25 cm, and one of the holder 8 and the belt is moved according to the width dimension so that the facing distance is changed.

Therefore, even if the spray width of the nozzle 9 is fixed to the maximum, the unnecessary portion is covered with the cover to prevent the hot water 6 from scattering to other portions. Although not shown in the figure, a prototype of a removal device that sprayed steam instead of the hot water 6 was prototyped. However, since steam has a smaller heat capacity than hot water, temperature control is difficult, removal efficiency is low, and the number of series must be increased. However, there is an advantage that the drying process is not required after the removal and the total process can be shortened.

The above embodiment is an example, and the shape, size, and material of each part are not limited to the above.

[0027]

As described above, according to the solder ball removing method of the present invention, an apparatus for surely removing solder balls remaining in the vicinity of soldering without using an organic halogen solvent can be obtained. By increasing the number of times, it is possible to replace the conventional cleaning device without changing the number of steps.

[Brief description of drawings]

FIG. 1 is an explanatory view of the principle of the present invention.

FIG. 2 is a side view of a removing device according to an embodiment of the present invention.

[Fig. 3] Reflow soldering process (a) Solder printing state (b) Pre-heating state (c) Solder molten state

[Explanation of symbols]

1 Solder ball 2 Flux 3
Solder paste 4 Printed wiring board 5 Terminals 6
Hot water 7 Roller brush 8 Holder 9
Nozzle 41 Soldering surface 42 Connection pad 9
1,92 Optical sensor 99 Injection port

Claims (3)

[Claims] 1. A solder paste (3) consisting of a solder ball (1) and a flux (2) is printed and adhered to a printed wiring board (4), and a component terminal (5) is placed on the printed wiring board (4), and a predetermined part is attached. After passing through a heating furnace with a temperature profile and performing reflow soldering, the residue and solder balls remaining in the soldered part
(1) is removed by moving the printed wiring board (4) horizontally below the soldering surface (41) at a constant speed to remove hot water ( 6) is sprayed over the entire width of the printed wiring board (4) obliquely from below to heat the soldering surface (41),
Solder ball removal characterized by cleaning and also the soldering surface (41) of the pouring part of the hot water (6) with a roller brush (7) that rotates so that the brush bristles sweep in the traveling direction. Method. 2. The method for removing solder balls according to claim 1, wherein heated compressed air is used instead of the hot water (6). 3. A solder ball removing method, characterized in that the solder removing method according to claim 1 or 2 is repeated a plurality of times in series in the traveling direction.