JPH10173327A - Method and system for soldering surface-mounting printed board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent bubbles from being mixed into a solder for soldering the terminal of a chip, located at a step and a soldering part by applying an ultrasonic vibration to bubbles confined in a molten solder formed on the outer circumference of an electronic device mounted on a board at the time of immersion, thereby removing bubbles. SOLUTION: After being thrust into a solder 6, a board 11 is applied at the step part thereof, with an ultrasonic vibration from a horn 27 of an ultrasonic vibrator, disposed in the proximity of the solder flow 6 in order to remove bubbles 32. When the board 11 is pulled up after being immersed into the solder flow 6 to such an extent as the ultrasonic vibration is also applied to other terminal part of a chip 9, the bubbles 32 are removed again and the chip 9 is placed in a space 23 defined by the board 11, an upper guide 22, a lower guide 21 and the solder flow 6, thus completing the soldering of the chip 9 and a printed wiring 16. According to the method, the bubbles 32 are eliminated from the solder for soldering the chip 9 and the printed wiring 16.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for soldering a surface-mounted printed circuit board, which solders an electronic component to a printed circuit board on a surface on which the electronic component is mounted.

[0002]

2. Description of the Related Art Conventionally, soldering between a mounted chip and a printed wiring on a surface mount type printed circuit board in which electronic components (chips) are connected by soldering on the chip mounting surface side of the printed circuit board is performed on the surface of the board (mounting surface). = Soldering side)
Is immersed (contacted) in a flow of molten solder (solder flow), so that the soldered portion of the printed wiring that protrudes out of the resist ink that insulates the printed wiring and the terminal that protrudes from the outer periphery of the mounted chip Solder or attach paste cream solder to the soldering part in the printed wiring, heat the substrate on which the chip is mounted so that the terminals are located on the cream solder, melt the cream solder, and It has been performed by a method such as soldering a soldering portion.

[0003]

However, the method of dipping the substrate in the solder flow can be performed at a relatively low cost, but the solder flow flows into the terminal side in order to solder the terminals of the chip and the printed wiring. When the flux (solvent)
The gas generated by the heating or the like of the solder flows into the solder flow or is formed by entraining air in the solder flow when the solder flow flows into the terminal side. There is a problem that the terminal formed near the step portion penetrates into the solder for soldering due to the step portion formed by the step (1), and the air bubbles cause defective soldering or the like.

[0004] Therefore, in the soldering in which the substrate is brought into contact with (immersed in) the solder flow, a soldering operation is performed a plurality of times, the solder is sprayed onto the substrate in a jet jet manner, or the solder is jetted to form a solder flow. A method of eliminating the soldering failure due to the air bubbles by swinging the jet port or the substrate itself is generally adopted. However, there are disadvantages such as poor work efficiency and generation of a bridge (short circuit) due to soldering of each chip terminal. There were problems such as relatively many.

On the other hand, the method using cream solder requires a relatively large number of work steps because it is necessary to apply cream solder on the substrate in advance, and the work cost of soldering is high due to the relatively expensive cream solder. In addition to the drawbacks, the cream solder is usually attached to the substrate by screen printing, which makes it difficult to print (adhere) the cream solder to a relatively small part and to control the amount of cream solder. there were.

[0006]

According to the present invention, there is provided a method of soldering a surface mount type printed circuit board on the mounting surface 11a of an electronic component 9.
The terminal 9b is connected to the circuit 16 on the side of the substrate 11 by dipping the surface-mount type substrate 11
b is connected to the board-side circuit 16 by soldering, and ultrasonic vibration is applied to the bubbles 32 in the dissolving solder 6 formed on the outer periphery 9a of the electronic component on the board 11 at the time of immersion. The first feature is that 32 is defoamed and removed.

Second, applying ultrasonic vibration toward the moving mounting-side substrate surface at a position near the liquid level of the melting solder 6 where the electronic component 9 enters or exits the liquid level of the melting solder 6. The feature is.

A third feature is that the substrate 11 is immersed by inserting and removing the substrate 11 from the liquid surface of the melting solder 6 downward.

On the other hand, the soldering apparatus for a surface-mounted printed circuit board according to the present invention comprises a surface-mounted board 11 for connecting the terminals 9b of the electronic component 9 to the circuit 16 on the board 11 on the mounting surface 11a side of the electronic component 9. Is inserted and removed in the vertical direction, so that the substrate 11 is immersed in the contained solder 6 and the terminal 9b and the circuit 16 are soldered. An ultrasonic vibration device 28 for applying ultrasonic vibration having a radiation axis whose direction intersects to the mounting surface 11a side of the substrate 11 near the liquid surface lower surface of the melting solder 6, and inserting the ultrasonic vibration into the substrate 11 of the melting solder 6. A gas nozzle 1 for injecting a non-oxidizing gas to a position near the liquid surface in a departure portion to form a non-oxidizing atmosphere
8 is provided.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail. FIG. 1 is a side view of a soldering device 1 for a surface mount type printed circuit board 11 for connecting terminals of the electronic chip 9 to a printed circuit on the board side on the mounting surface 11a side of the electronic chip 9. A so-called jet-type melting solder tank 3 containing melting solder is provided in the lower part of the main body 2. A solder flow 6 of the melting solder flows from a jet port 4 provided in the melting solder tank 3 and having an open top. Is squirting out to recirculate. An upper plate 8 having a substrate insertion port 7 opened above the melting solder bath 3 is provided.
The surface mount type printed circuit board 11 on which the chip (electronic chip) 9 is mounted (mounted) through the board insertion opening 7 can be vertically inserted into and removed from the main body 2 (melting solder tank 3). Has become.

As a result, the substrate 11 is moved up and down, and the substrate 11 is inserted into the main body 2 from the substrate insertion opening 7 so that the substrate 1
After immersing the chip 1 and the chip 9 in the solder flow 6 (melting solder), the substrate 11 immersed in the solder flow 6 is pulled up, so that the printed wiring of the substrate 11 and the chip 9 are soldered. The vertical movement of the substrate 11 is performed by clamping (holding) the upper end of the substrate 11 (the end opposite to the side to be inserted into the melting solder tank 3) with a holding holder 12 such as a conventionally known vertical moving robot mechanism (not shown). ) Can be easily performed by the robot.

Here, the structure of the surface mount type printed circuit board 11 will be briefly described. As shown in FIG.
A printed wiring 16 is formed on one or both sides of a base substrate 13 by forming a printed wiring 16 insulated by a heat-resistant insulating coating material (resist ink) 14.
The printed wiring 16 on the surface on the 6th side (mounting surface 11a)
Mounting section 17 where resist ink 14 does not exist
The chip 9 is to be mounted (to be formed in a concave shape) by bonding or the like.

As described above, on the mounting surface 11a side, the terminal 9b projecting from the outer periphery 9a of the chip 9 and the printed wiring 16 are connected by soldering, but the soldered portion 16a of the printed wiring 16 to the terminal 9b is connected. Is configured such that the resist ink 14 is peeled off and can be soldered. The chip 9 is mounted on the substrate 11 as shown in FIG.
And the substrate 11 form an uneven step portion 33. At this time, since the terminal 9b of the chip 9 protrudes from the outer periphery 9a of the chip 9, the step portion 33 includes a soldered portion 16a of the substrate 11 with the chip 9. .

On the other hand, as shown in FIG. 1, a gas nozzle for ejecting an inert gas such as nitrogen gas or hydrogen gas or a reducing gas is provided in a space below the upper plate 8 and between the upper plate 8 and the jet port 4. Two are provided symmetrically with respect to the substrate insertion port 7. At this time, a filter 19 for uniformly dispersing the gas is attached to the end face of the gas nozzle 18 and the solder flow 6 ejected from the jet port 4 is guided downward below the end face. A lower guide 21 is attached to this portion to shut off gas and outside air.

Above the end face of the gas nozzle 18, there is also provided an upper guide 22 which is close to the substrate 11 to be inserted from the substrate insertion port 7 (see FIG. 3). When inserted, the space 2 formed on the upper surface of the solder flow 6 by the upper guide 22, the substrate 11, the lower guide 21, and the solder flow 6 as shown in FIG.
3 is substantially shielded from the outside air, and the space 23 is a gas nozzle 1
The gas injected from 8 forms a non-oxygen space with a very low oxygen concentration. At this time, by inserting the substrate 11 so that the space 23 is formed on the mounting surface 11a (solder surface) of the chip 9 on the substrate 11, the chip 9 mounted on the substrate 11 is attached to the main body 2 (solder flow) of the substrate 11. At the time of insertion / removal with respect to 6), it is placed in a non-oxidizing atmosphere at least immediately before entering the solder flow 6 and immediately after exiting from the solder flow.

On the other hand, behind the melting solder tank 3 in FIG. 1, there is provided an ultrasonic vibrator 28 having an ultrasonic vibrator 26 therein and a horn 27 for emitting ultrasonic vibration forward at the tip. The ultrasonic vibration device 28
(The radiation axis of the ultrasonic vibration radiated from the horn 27) approaches the lower surface of the solder flow 6 and the substrate 1
The horn 27 is inserted into the melting solder tank 3 so as to intersect the insertion / removal direction of the horn 1. At this time, the ultrasonic vibration device 28 is attached to the slide guide 29 so as to be slidable in the above-described axial direction, and the position in the slide direction is finely adjusted by an adjusting mechanism 31 provided on the slide guide 29 to dissolve the ultrasonic vibration. The distance between the horn 27 and the substrate 11 (chip 9) inserted into the solder bath 3 can be finely adjusted.

Next, the soldering of the surface mount type printed circuit board 11 and the chip 9 by the soldering apparatus 1 having the above structure will be described. First, the substrate 1 on which the chip 9 is mounted
When the chip 9 is immersed in the solder flow 6 by inserting the chip 1 vertically into the melting solder bath 3, the flux (solvent) applied to the substrate 11 is heated as shown in FIG. Bubbles 32 enter the solder flow 6 due to gas generated by the above-described method, air that is entrained in the solder flow 6 when the substrate 11 enters the solder flow 6, and the like.
The bubble 32 is located at the step 33 of the above.

However, immediately after the substrate 11 enters the solder flow 6, the ultrasonic vibrating device 28 provided in the step portion 33 near the liquid surface of the solder flow 6 as shown in FIG.
The ultrasonic vibration from the (horn 27) is applied, and the bubble 32 is removed by the ultrasonic vibration. And FIG.
As shown in FIG. 3C, the substrate 11 is immersed in the solder flow 6 to the extent that the ultrasonic vibration is also applied to the other terminal portions of the chip 9, and then the substrate 11 is moved upward as shown in FIG. When the substrate 11 is lifted up, the bubbles 32 are removed again just before the substrate 11 escapes from the solder flow 6, and then the chip 9 is removed from the substrate 1.
1 (chip 9), the upper guide 22, the lower guide 21, and the space 23 formed by the solder flow 6, the soldering between the chip 9 and the printed wiring 16 is completed.

At this time, since the air bubbles 32 entering the step portion 33 of the printed board 11 are removed as described above, the chip 9 (terminal 9b) and the printed wiring 16 (solder portion 1) are removed.
6a), there is no bubble 32 in the solder, and the soldering failure due to the bubble 32 is prevented, and the chip 9 is placed when the soldering is completed (immediately after the chip 9 escapes from the solder flow 6). Since the space 23 to be cut is a non-oxygen space having a very low oxygen concentration, the oxidation of soldering is effectively prevented. Further, since the horn 27 of the ultrasonic vibrator 28 applies ultrasonic vibration to the substrate 11 side in the vicinity of the lower surface of the solder flow 6, the bubble 32 is generated immediately after the chip 9 enters the solder flow 6 and immediately before the chip 9 escapes. The defoaming action works, and the bubbles can be more reliably defoamed. Furthermore, since the substrate 11 is inserted and removed downward from the solder flow 6, the substrate 11 (chip 9) can be more easily immersed in the solder flow 6.

When the substrate is a double-sided mounting substrate on which chips can be mounted on both sides, the two spaces 23 are formed by both gas nozzles 18 and the chips on both sides of the substrate. The chips on both sides are respectively placed in the space 23. Therefore, by providing a plurality of (two) ultrasonic vibrating devices so that ultrasonic vibrations can be applied to both mounting surfaces of the substrate (double-sided mounting substrate) inserted into the solder flow 6, as described above. Soldering of chips on both sides of the substrate can be performed simultaneously.

[0021]

According to the structure of the present invention constructed as described above, when the terminal of the electronic component and the soldered portion of the printed wiring are immersed in the melting solder, the outer periphery of the electronic component and the substrate are used. Since ultrasonic vibration is applied to the step formed, bubbles in the dissolving solder formed on the outer periphery of the electronic component are defoamed by the ultrasonic vibration at the step, and the terminal of the chip located at the step and the solder are removed. Air bubbles are prevented from being mixed into the solder for soldering the attachment portion, and poor soldering due to the air bubbles is prevented. Thus, the soldering of the electronic chip to the surface mount type printed circuit board can be performed relatively inexpensively and without soldering failure.

Further, since ultrasonic vibration is applied toward the mounting-side substrate surface moving at a position close to the liquid level of the dissolving solder, bubbles are removed when the electronic component enters or exits the dissolving solder. In addition to the effect of more reliably defoaming bubbles, the substrate (chip) can be more easily immersed in the dissolving solder by inserting and removing the substrate downward from the dissolving solder liquid surface. You can do it too.

[Brief description of the drawings]

FIG. 1 is a side view of a soldering apparatus for a surface mount type printed circuit board.

FIGS. 2A, 2B and 2C are a plan view and a side sectional view of a surface mount type printed circuit board.

FIGS. 3 (a), (b), (c), and (d) are main-portion side sectional views showing a soldered state of a substrate.

[Explanation of symbols]

 3 melting solder tank 9 electronic component 9a outer periphery 9b terminal 11 substrate 11a mounting surface 16 printed wiring (circuit) 18 gas nozzle 28 ultrasonic vibration device 32 bubble

Claims (4)

[Claims] 1. The terminal (9b) of the electronic component (9) is connected to the substrate (11) on the mounting surface (11a) side of the electronic component (9).
Surface mount type board (11) to be connected to the side circuit (16)
Is immersed in a melting solder bath (3) to connect the terminal (9b) and the circuit on the substrate side (16) by soldering.
By applying ultrasonic vibration to the bubbles (32) in the melting solder (6) formed in a), the bubbles (32) are applied.
A method of soldering a surface mount printed circuit board to remove bubbles. 2. An ultrasonic vibration toward a moving mounting-side substrate surface at a position near the liquid surface of the melting solder (6) at which the electronic component (9) enters or leaves the liquid surface of the melting solder (6). 2. The method for soldering a surface mount type printed circuit board according to claim 1, wherein 3. The method for soldering a surface mount type printed circuit board according to claim 1, wherein the board is immersed by inserting and removing the board downwardly from a liquid surface of the molten solder. 4. The terminal (9b) of the electronic component (9) is connected to the substrate (11) on the mounting surface (11a) side of the electronic component (9).
Surface mount type board (11) to be connected to the side circuit (16)
Is inserted and removed in the vertical direction, so that the substrate (11) is immersed in the contained solder (6), and the terminals (9) are removed.
b) a melting solder bath (3) for soldering the circuit (16) and the ultrasonic vibration having a radiation axis in a direction intersecting the insertion / removal direction of the substrate (11);
An ultrasonic vibrating device (28) applied to the mounting surface (11a) side of the substrate (11) at a position near the lower surface of the liquid surface
And a gas nozzle (18) for injecting a non-oxidizing gas to a position near the liquid surface at a portion where the melting solder (6) is inserted and removed from the substrate (11) to form a non-oxidizing atmosphere. Soldering equipment.