JPH06255078A - Coating of substrate with paste - Google Patents

Abstract

PURPOSE:To accurately apply solder paste to a printing substrate by preventing the generation of trouble such that solder paste remains on a mask or a bridge is formed between solder paste coated parts when the mask is separated from the printing substrate. CONSTITUTION:A mask 3 is superposed on the surface of a printing substrate 1 and solder paste 6 is applied to the surface of the printing substrate 1 through the hole formed to the mask 3 and the mask 3 is separated from the surface of the printing substrate 1. In this method, when the mask 3 is separated from the printing substrate 1, vibration is applied to at least either one of the mask 3 and the substrate 1 along the direction separating the mask 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of applying solder paste to a substrate in reflow soldering.

[0002]

2. Description of the Related Art As a technique for mounting a multi-terminal electronic component having leads in multiple directions, such as a flat package IC or a TAB component, on a surface of a printed circuit board, a predetermined pattern formed on the surface of the printed circuit board is used. Apply the solder paste by reflow soldering, then place the multi-terminal electronic component on the surface of the board, put each lead of the multi-terminal electronic component on the solder paste applied to the printed board, and heat the solder paste from the outside. Then, the leads of the multi-terminal electronic component and the pattern of the printed board are connected and fixed.

In the reflow soldering, a metal mask having holes formed in accordance with a predetermined pattern on a printed board is prepared, the mask is placed on the surface of the printed board and brought into close contact with it, and then a solder paste printing machine is used. This is a method of performing printing, applying solder paste through a hole of a metal mask onto a predetermined pattern of a printed board in the same shape and size, thereby forming a plurality of solder paste application parts on the surface of the printed board. After applying the solder paste, the mask is moved in the plate thickness direction of the printed board to separate it from the surface of the printed board.

[0004]

However, such a reflow soldering method has the following problems.

After the mask is placed on the surface of the printed circuit board and adhered thereto to apply the solder paste, when the mask is separated from the printed circuit board, a part of the solder paste applied portion of the solder paste application part formed on the surface of the printed circuit board is masked. May remain attached to the periphery of the hole.

In this case, of the solder paste application parts formed on the surface of the printed board, the solder paste application part in which the solder paste remains on the mask side has the phenomenon that the solder paste remains on the mask side. The solder paste application amount is smaller than that in the solder paste application portion in which the solder paste does not occur, and the solder paste application amount varies between the solder paste application portions. This causes variation in the connection state between the leads of the multi-terminal electronic component and the pattern of the printed circuit board when mounting the multi-terminal electronic component on the printed circuit board.

Further, when the mask is separated from the printed board after the solder paste is applied, the solder paste in the solder paste application section may be drawn by the mask and drip.

Then, the solder paste dripping from the solder paste application section contacts another adjacent solder paste application section, and as a result, a bridge is formed between the solder paste application sections, and the solder paste application sections are short-circuited. There is.

Recently, the outer leads of a multi-terminal electronic component mounted on the surface of a printed board are becoming narrower in pitch. For example, when the distance between the leads is 0.3 mm or less, the opening width of the holes in the mask is It is 0.15 mm or less for one pattern formed on. When the interval between the solder paste application parts is narrow as described above, a short circuit between the solder paste application parts is more likely to occur.

As described above, conventionally, when the mask is separated from the printed board, the solder paste remains on the mask, or a bridge is formed between the solder paste application sections, so that the shape of the solder paste application section formed on the printed board is changed. There was a problem in that the solder paste would collapse and the solder paste could not be applied accurately.

The present invention has been made based on the above circumstances, and prevents the occurrence of problems such as the solder paste remaining on the mask and the formation of a bridge between the solder paste application portions when the mask is separated from the printed board. It is an object of the present invention to provide a coating method capable of accurately coating the solder paste on the printed board.

[0012]

In order to achieve the above object, a method of applying a paste to a substrate of the present invention is as follows: a mask is placed on the substrate and solder paste is applied on the substrate through holes formed in the mask. In the method of applying the above, and then separating the mask from the substrate, when the mask is separated from the substrate, vibration is applied to at least one of the mask and the substrate along a direction in which the mask is separated. It is what

[0013]

When the mask is separated from the surface of the printed board, vibration is applied to at least one of the mask and the printed board in the direction of separating the mask to apply the solder paste formed on the surface of the printed board. The mask can be separated from the printed board without breaking the shape of the portion.

Therefore, when the mask is separated from the printed board,
It is possible to prevent the phenomenon that the solder paste remains on the mask and a bridge is formed between the solder paste application portions.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram for explaining an embodiment of the coating method of the present invention, and FIG. 2 is a diagram schematically showing this embodiment.

The printed board and the mask to which the solder paste is applied are set in a printing machine, and the solder paste is applied to the printed board. This process will be described below.

As shown in FIG. 1 (a), the printed board 1 is placed on the pedestal 2 and arranged horizontally. The printed board 1 is an insulating resin,
It is formed of ceramics or the like, and a predetermined pattern (not shown) is formed on the upper surface of the conductive material.

A multi-end terminal electronic component (not shown) is arranged at a predetermined position on the surface of the printed board 1, and leads provided on the electronic component are connected to the pattern formed on the printed board 1.

A mask 3 is prepared when applying the solder paste. The mask 3 is made of metal, and has a size and shape corresponding to the size and shape of the pattern formed on the printed board 1 at a plurality of positions facing the position of the pattern for connecting with the leads of the multi-end terminal electronic component. A hole 4 is formed. The mask 3 is arranged right above the printed circuit board 1, and the peripheral portion of the mask 3 is supported horizontally by a holder 5 provided in an elevating device (not shown).

When applying the solder paste, the holder 5 is lowered by the elevating device, and the printed board 1 supported by the holder 5 is lowered in the vertical direction (printing board thickness direction) for printing. The upper surface of the substrate 1 is overlaid and adhered. In this state, the holes 4 of the mask 3 are formed in the printed board 1
In, the pattern is connected to the lead of the multi-terminal electronic component.

Next, the solder paste 6 is placed on the upper surface of the mask 3. As solder paste, solder, gold,
Tin, silver, etc. are used. The squeegee 7 is moved on the upper surface of the mask 3 by a driving device (not shown), and the solder paste 6 is moved on the upper surface of the mask 3 by the driven squeegee 7.

The solder paste 6 enters each hole 4 formed in the mask 3 while being moved by the squeegee 7,
A mask 3 is formed on each pattern of the printed board 1 facing each hole 4.
It is applied with a thickness corresponding to the plate thickness of. That is,
A solder paste application section 6 is formed on each pattern of the printed board 1 facing each hole 4 of the mask 3.

After the application of the solder paste 6 is completed, as shown in FIG. 1 (b), the mask 3 held by the holder 5 is lifted in the vertical direction and separated from the printed board 1 by the lifting device. At this time, ultrasonic vibration is applied to the mask 3 along the separating direction (vertical direction, that is, the thickness direction of the printed board). A method of applying ultrasonic vibration to the mask 3 will be described. The ultrasonic horns 9 are provided at a plurality of positions on the peripheral portion of the mask 3 with the configuration described below.

As shown in FIG. 1, a bracket 8 is attached to a holder 5 for holding the mask 3, and an ultrasonic horn 9 having a piezoelectric element 10 is vertically held on the bracket 8.
The lower end of the ultrasonic horn 9 is a holder 1 attached to the mask 3.
Hold at 1. The piezoelectric element 10 is electrically connected to the DC power supply 12.

Then, a voltage is applied from the DC power source 12 to the piezoelectric element 10 of each ultrasonic horn 9, and the action of the piezoelectric element 10 causes each ultrasonic horn 9 to have an amplitude direction perpendicular to the ultrasonic horn 9 (mask 3 The ultrasonic vibration is generated along the direction of separating.

The ultrasonic vibration generated by each ultrasonic horn 9 is transmitted to the mask 3 via the holder 11. In this way, ultrasonic vibrations are transmitted at a plurality of locations along the peripheral edge of the mask 3 to uniformly ultrasonically vibrate the entire mask 3.

In this way, the mask 3 is moved upward and separated from the printed board 1 while applying ultrasonic vibration. When the solder paste 6 is applied, the solder paste application portions 6 formed on the pattern of the printed board 1 inside the holes 4 of the mask 3 are bonded to the peripheral portions of the holes 4, but the mask 3 is released. By separating the mask 3 from the printed board 1 while applying ultrasonic vibration in the direction, the solder paste of each solder paste application section 6 and the peripheral edge of each hole 4 are clearly separated.

Therefore, the mask 3 can be separated from the printed board 1 without breaking the shape of each solder paste application portion 6 formed on the surface of the printed board 1. Therefore, when the mask 3 is separated from the printed board 1, the solder paste 6 remains on the mask 3 and the shape of the solder paste application section 6 is lacking, resulting in a variation in the solder paste application amount of each solder paste application section 6. It can be prevented from occurring.

Further, the solder paste of the solder paste applying section 6 is dripping and adjacent to the solder paste applying section 6
It is possible to prevent a phenomenon in which a bridge is formed between the solder paste application parts 6 by contacting with each other. As a result, the solder paste application part 6 can be accurately formed on the printed board 1. This is particularly effective when the intervals between the solder paste application parts are small.

The amplitude of ultrasonic vibration applied to the mask 3 is
1μ to keep the shape of solder paste application part 6
m or less. The frequency of ultrasonic vibration applied to the mask 3 varies from 28 to 28 depending on the type or viscosity of the solder paste.
Select an appropriate value from the range of 250 KHz.

The piezoelectric element 10 and the ultrasonic horn 9
By providing the bracket 8 to be exchangeable,
Piezoelectric elements 10 having different frequencies of ultrasonic vibration can be selected.

In the above-described embodiment, only the mask 3 is ultrasonically vibrated, but in order to achieve the object of the present invention, it is possible to apply the ultrasonic vibration only to the printed substrate 1, or the mask 3 and the printing are performed. It is also possible to apply ultrasonic vibration to both of the substrates 1. When the ultrasonic vibration is applied only to the printed board 1, the ultrasonic vibration is applied to the printed board 1 by an ultrasonic horn provided with a piezoelectric element as in the above-described embodiment.

When ultrasonic vibration is applied to both the mask 3 and the printed board 1, both the printed board 1 and the mask 3 are exposed to the mask 3 by an ultrasonic horn provided with a piezoelectric element as in the above-described embodiment. Ultrasonic vibration is applied to both of the printed boards 1. FIG. 3 schematically shows an embodiment in which ultrasonic vibration is applied to both the mask 3 and the printed board 1.

In this case, for example, as shown in FIG. 4, when the phase of the ultrasonic vibration applied to the printed board 1 and the phase of the ultrasonic vibration applied to the mask 3 are made different from each other, the mask 3 and the solder paste can be more reliably. The coating unit 6 can be separated. The device for generating ultrasonic vibrations is not limited to that of the above-described embodiment, and ultrasonic vibrations are optimal as the vibrations applied to the printed board and the mask, but the invention is not limited to this. Further, the present invention is not limited to mounting the multi-terminal electronic device on the printed board, but can be widely applied to the case of performing reflow soldering.

[0035]

As described above, according to the method of applying the paste to the printed board of the present invention, when the mask is released from the surface of the printed board, the direction of releasing the mask to the mask or at least one of the printed boards is increased. By applying vibration along the surface of the printed circuit board, the mask can be separated from the printed circuit board without breaking the shape of the solder paste application part formed on the surface of the printed circuit board. It is possible to prevent the phenomenon that a bridge is formed between the paste application portions from occurring, and it is possible to accurately apply the solder paste to the printed board.

[Brief description of drawings]

FIG. 1 is a diagram illustrating an embodiment of a method of the present invention.

FIG. 2 is a diagram schematically showing the same embodiment.

FIG. 3 is a diagram schematically showing another embodiment.

FIG. 4 is a diagram showing a waveform of vibration applied to a printed board and a mask in the example.

[Explanation of symbols]

1 ... Printed circuit board, 3 ... Mask, 6 ...
Solder paste application part, 9 ... Horn, 10 ... Piezoelectric element.

Claims (1)

[Claims] 1. A method of arranging a mask on a surface of a printed board, applying solder paste to the surface of the printed board through holes formed in the mask, and then separating the mask from the surface of the printed board. A method of applying a paste to a substrate, characterized in that, when the mask is separated from the printed substrate, at least one of the mask and the substrate is vibrated along a direction in which the mask is separated.