JP2003110232A - Mask jig for flow soldering and mounting method of electronic parts by using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To heat a printed wiring board more efficiently than a conventional one, without extending a pre-heating zone nor extending heating time in a pre-heating process. SOLUTION: A mask jig 1 loaded on the printed wiring board 2 is provided with a frame 3 surrounding the periphery of the printed wiring board 2, shielding parts 4 and 5 which are formed inside the frame 3 and shield and area where the contact of molten solder in the printed wiring board 2 is not desirable and an opening part 6 exposing an area including a part where soldering is performed in the printed wiring board 2. The mask jig 1 where the shielding parts 4 and 5 are constituted of heat resistant materials transmitting an infrared ray radiated from a heater is mounted on a face where the printed wiring board 2 is soldered. Electronic parts 7 are soldered on the printed wiring board 2 by a flow soldering method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of soldering an electronic component to a printed wiring board while shielding a region where molten solder is not preferable to contact during flow soldering, and a mask jig used in that case. It is a thing.

[0002]

2. Description of the Related Art FIG. 4 is a cross-sectional view (FIG. A) of a board J2 and a mask jig when a conventional mask jig J1 is mounted on a soldering surface of a printed wiring board J2, and the printed wiring at this time. A plan view (FIG. B) of the surface of the substrate J2 on which the mask jig J1 is mounted is viewed from the front. Further, FIG. 5 shows one step of a flow soldering method using a conventional mask jig.

Conventionally, when a plurality of lead electronic components J7 are mounted in a region J2a including a through hole J9 of a printed wiring board J2 having a plurality of electronic components J8 mounted on both sides, a mask jig is mounted on the printed wiring board J2. Wear J1,
Only the area J2a including the through hole J9 is soldered by the flow soldering method.

This method will be described. After a plurality of electronic components J8 are mounted on both sides in the previous step, the steps shown in FIGS.
As shown in FIG.
When the board is mounted, an opening J6 having a portion corresponding to a region J2a (hereinafter referred to as a soldering region J2a) including a through hole J9 for soldering in the printed wiring board J2, and a printed wiring board Of J2, a shield for shielding a region J2b in which a plurality of electronic components J8 are mounted in the previous step and a region J2c where adhesion of solder or the like is not preferable (hereinafter, these two regions are referred to as mask regions J2b and J2c, respectively) A stainless steel mask jig J1 having parts J4 and J5 is mounted on the surface of the printed wiring board J2 to be soldered.

Then, the solder flux is applied to the printed wiring board J2 while the mask jig J1 is mounted, and the solder flux is applied only to the soldering area J2a. Next, in order to evaporate the solvent in the solder flux, the mask jig is attached in the preheating step, and the upper surface of the heater is passed with the surface having the soldering area J2a facing down.
The entire printed wiring board J2 is heated.

After that, as shown in FIG. 5, in that state, the molten solder to be jetted is passed over the molten solder to bring the molten solder into contact with the soldering region J2a, so that only the soldering region J2a is soldered. To do.

[0007]

In the step of passing the printed wiring board J2 over the molten solder, when the molten solder comes into contact with the soldering area J2a, the molten solder enters the through hole J9. Then, the molten solder moves in the through hole J9 from the surface of the printed wiring board J2 in contact with the molten solder to the surface opposite thereto, and the entire area of the through hole J9 is filled with this solder. As a result, the lead electronic component J7 inserted into the through hole J9
Is fixed to the printed wiring board J2.

However, at this time, when the temperature of the printed wiring board J2 is lower than the temperature of the molten solder, the temperature of the molten solder decreases while the molten solder moves in the through hole J9. The molten solder is printed wiring board J
If the temperature of the molten solder becomes lower than the melting point before reaching the surface opposite to the surface having the second soldering area J2a, the molten solder solidifies. As a result, the molten solder cannot move any more, and the through hole J9 cannot be sufficiently filled with solder. Therefore, the fixing of the lead electronic component J7 to the printed wiring board J2 by soldering becomes insufficient.

Therefore, in order to prevent this, in the preheating step which is the preceding step, the soldering area J2
It is necessary to bring the temperature of a close to the temperature of the molten solder in advance.

Conventionally, lead-tin solder has been used as solder, and the temperature of the molten solder has been around 240.degree.
However, since the melting point of this lead-tin solder was about 180 ° C., it was not necessary to heat the temperature of the soldering region J2a to around 240 ° C., and it was sufficient to heat it to be higher than 180 ° C.

However, in recent years, the melting point is about 220 ° C.
And lead-free solder, which is higher than lead-tin solder, is used, and the soldering area J2 is set so that the temperature becomes higher than before.
a had to be heated. On the other hand, by increasing the preheat zone or extending the heating time, it is possible to sufficiently heat the soldering area, but in these cases, the equipment cost increases due to the extension of the preheat zone. Also, problems such as a decrease in production rate due to extension of heating time occur.

In view of the above points, an object of the present invention is to heat the soldering area J2a to a higher temperature than before by suppressing an increase in equipment cost and a decrease in production rate.

[0013]

[Means for Solving the Problems] In order to achieve the above object, the improvement points of the conventional heating method were examined, and the following were considered.

In this step, the entire printed wiring board J2 is heated together with the mask jig J1 by a heater that radiates infrared rays. However, when the mask jig J1 is mounted, the mask areas J2b, J of the printed wiring board J2 are
Since 2c is not directly heated by the heater but is heated by radiant heat from the heated stainless steel mask jig J1, the temperature rise takes longer than that in the soldering area J2a. This causes a temperature difference between the soldering area J2a and the mask areas J2b, J2c, and the heat of the soldering area J2a escapes to the mask areas J2b, J2c. Therefore, the heating efficiency of the printed wiring board J2 was not good.

Therefore, in the invention described in claim 1, a step of mounting the electronic component (7) on the printed wiring board (2),
An opening for exposing a predetermined area (2a) of the printed wiring board (2) including a portion to be soldered, to the surface of the printed wiring board (2) opposite to the surface on which the electronic component (7) is mounted. A mask jig (1) having a part (6) and a shielding part (4, 5) for shielding other than a predetermined region, and the shielding part (4, 5) made of a heat-resistant material that transmits infrared rays is mounted. Process and mask jig (1) of printed wiring board (2)
A step of applying a solder flux to the surface on which the solder is attached and applying a solder flux to the predetermined area (2a), and then heating the predetermined area by a heating means that emits infrared rays, and infrared rays emitted from the heating means. A step of heating a portion other than the predetermined area by transmitting the light to the blocking portion, and thereafter, by contacting the molten solder with the surface of the printed wiring board (2) on which the mask jig (1) is mounted, the predetermined area ( 2a)
It is characterized in that it has a step of performing soldering only on.

By performing flow soldering by using the mask jig whose shield portion is made of a heat-resistant material that transmits infrared rays in this way, the printed wiring board can be heated when the printed wiring board is heated in the preheating step. The area of the substrate covered with the mask jig can be heated by not only the radiant heat of the mask jig but also the infrared rays radiated from the heating means. As a result, the entire printed wiring board can be heated more efficiently than before.

Therefore, even when using a lead-free solder having a melting point higher than that of lead-tin solder, it is not necessary to add a preheating zone for heating in the preheating step. Further, the heating time may not be extended.

As a heat resistant material that transmits infrared rays,
For example, it is preferable to perform soldering by using a mask jig that uses heat-resistant tempered glass as described in claim 2.

According to the third aspect of the invention, the step of mounting the electronic component (7) on the printed wiring board (2) and the surface of the printed wiring board (2) on which the electronic component (7) is mounted. An opening (6) for exposing a predetermined area (2a) of the printed wiring board (2) including a portion to be soldered and a shield section (4, 5) for shielding the area other than the predetermined area on the opposite surface. Has a plurality of diameters of 1.0 m
Mask jig (1) having a hole of m or less
Of the printed wiring board (2), applying solder flux to the surface of the printed wiring board (2) on which the mask jig (1) is attached, and applying solder flux to the predetermined area (2a), and then printing. The step of heating the wiring board (2), and then the mask jig (1) of the printed wiring board (2)
It is characterized by having a step of soldering only the predetermined region (2a) by bringing the molten solder into contact with the surface on which is mounted.

Even if a mask jig having a hole having a size such that molten solder does not pass through is used, the printed wiring board can be heated more efficiently than before in the preheating step.

A mask jig according to a fourth aspect, when mounted on a printed wiring board (2), has a frame portion (3) surrounding the printed wiring board (2), and the printed wiring board (2). Of the printed wiring board (2), an opening (6) for exposing a predetermined region including a portion to be soldered and a shield (4, 5) for shielding the printed wiring board (2) other than the predetermined region are provided. It is characterized in that it is made of a heat-resistant material that allows permeation.

By using this mask jig, the electronic component mounting method according to the first aspect can be performed.

Further, in the mask jig according to claim 5, heat-resistant tempered glass is used for the shielding portion, and the electronic component mounting method according to claim 2 is performed by using this mask jig. You can

A mask jig according to a sixth aspect of the present invention, when mounted on a printed wiring board (2), includes a frame portion (3) surrounding the printed wiring board (2) and the printed wiring board ( An opening (6) for exposing a predetermined area including a portion to be soldered of 2) and a shield (4, 5) for shielding the printed wiring board (2) other than the predetermined area are provided. Is characterized by having a plurality of holes with a diameter of 1.0 mm or less.

By using this mask jig, the electronic component mounting method according to the third aspect can be performed.

The reference numerals in parentheses of the above-mentioned means indicate the correspondence with the concrete means described in the embodiments described later.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIG. 1 is a cross-sectional view (FIG. A) of a printed wiring board 2 on which a mask jig 1 to which the first embodiment of the present invention is applied is mounted and a printed wiring board 2
2 is a plan view (FIG. B) of the surface on which the mask jig 1 of FIG.

As shown in FIGS. 1A and 1B, the mask jig 1 includes a substantially rectangular frame portion 3, shield portions 4 and 5 formed inside the frame portion 3, and the shield portion 4. 5 and an opening 6 in a region where 5 is not formed.

In the mask jig 1, the frame portion 3 is formed in a shape corresponding to the outer shape of the printed wiring board 2 so that the printed wiring board 2 and the mask jig 1 can be positioned and fixed.

Therefore, in the present embodiment, when the mask jig 1 is mounted on the substantially rectangular printed wiring board 2, the inside of the frame portion 3 is formed so that the printed wiring board 2 can fit exactly inside the frame portion 3. It has a rectangular shape. Here, the outside of the frame portion is also formed in a substantially rectangular shape. Further, at the time of flow soldering, the mask jig 1 is mounted on the printed wiring board 2 and the frame portion 3 of the mask jig 1 is held by the transport mechanism of the soldering device, whereby the mask jig 1 The printed wiring board 2 and the printed wiring board 2 are integrally conveyed. The frame 3 is made of stainless steel.

Next, the shielding portion 4 is for preventing the molten solder from adhering to the region 2b (hereinafter referred to as the mask region 2b) of the printed wiring board 2 where the plurality of electronic components 8 are already mounted. Is. Therefore, the shielding portion 4 is formed so as to cover the entire mask region 2b. And
As shown in FIG. 1A, the shielding portion 4 has a concave shape on the printed wiring board 2 side and has a bottom surface 4a and a side wall 4b. Since the shielding portion is thus formed in a concave shape, the shielding portion 4 can accommodate the electronic component 8 mounted on the printed wiring board 2.

Further, the shielding portion 5 prevents solder from adhering to a region 2c (hereinafter referred to as a mask region 2c) of the printed wiring board 2 where electronic components are not mounted but solder should not be attached. It is for. Like the blocking section 4, the blocking section 5 is also formed so as to cover the entire mask region 2c. The blocking portion 5 is also formed in a concave shape and has a bottom surface 5a and a side wall 5b.

Heat-resistant tempered glass, for example, is used as a material for transmitting infrared rays on the bottom surfaces 4a, 5a of the shielding portions 4, 5, and stainless steel is used for the side walls 4b, 5b.

Although the blocking portion 5 has a concave shape on the printed wiring board 2 side, if there is no electronic component and no problem occurs even if the blocking portion 5 comes into contact with the printed wiring board 2, the blocking portion 5 is, for example, the bottom surface 5a. It may be configured with only.

Then, as shown in FIG. 1B, the opening 6 is a region including the through hole 9 in the printed wiring board 2 where the lead 7a of the lead electronic component 7 is located (hereinafter, soldering region 2a). 2) is formed at a predetermined position inside the frame 3 so as to expose 2a.

When performing flow soldering using this mask jig 1, as shown in FIG. 1, the surface of the printed wiring board 2 to be soldered is faced down and the present embodiment is applied to that surface. Mount the applied mask jig 1 and print wiring board 2
Is set together with the mask jig 1 in the flow soldering device.

Then, in the step of applying the solder flux, the solder flux is applied to the soldering area 2a of the printed wiring board 2. Next, the printed wiring board 2 together with the mask jig 1 is conveyed to a preheat zone in which a heater is installed. Next, in a preheating step, the entire printed wiring board 2 is heated together with the mask jig 1 while passing over a preheating zone in which a heater is installed. Here, the heater is a heating means that emits infrared rays.

In this step, since heat-resistant tempered glass is used for the bottom surfaces 4a, 5a of the shielding portions 4, 5 of the mask jig 1 instead of the conventional stainless steel, the heaters, which are almost shielded by stainless steel, radiate the heat. Infrared rays can be transmitted to the blocking units 4 and 5. From this,
In addition to the radiant heat of the mask jig 1, the mask areas 2b and 2c can be heated by infrared rays from the heater. As a result, the temperature of the mask regions 2b and 2c rises faster than in the conventional case, and as a result, the entire printed wiring board 2 can be efficiently heated.

For reference, FIG. 2 shows a comparison result of the temperature gradient of the printed wiring board when the mask jig 1 and the conventional mask jig J1 in the preheating step are used.
From this result, it can be seen that the temperature gradient is higher when the mask jig 1 to which the present embodiment is applied is used as compared with the conventional case. That is, the temperature of the printed wiring board 2 rises faster than in the conventional case, and the printed wiring board using the mask jig 1 to which the present embodiment is applied is faster than the conventional mask jig made of stainless steel. It can be said that 2 is being efficiently heated.

As a result, even if lead-free solder is used, the mask jig 1 can be heated to near the melting point of the lead-free solder without increasing the preheating zone or extending the heating time.

After this preheating step, the printed wiring board 2 together with the mask jig 1 is conveyed to a flow tank in which molten solder is jetted, and is brought into contact with the molten solder to solder only the soldering area 2a.

Although the mask jig 1 to which the present embodiment is applied is provided with two cut-off shields and one opening.
It suffices to provide the required number of blocking portions and openings in accordance with the arrangement of the area where the flow soldering is performed and the area where the printed wiring board 2 is not performed.

Although heat-resistant tempered glass is used for the bottom surfaces 4a and 5a of the blocking portions 4 and 5, other heat-resistant materials that allow infrared rays to pass therethrough may be used.

(Second Embodiment) FIG. 3 is a sectional view of the printed wiring board 2 and the mask jig 21 when the mask jig 21 to which the second embodiment of the present invention is applied is mounted (FIG. 3A) and the printed wiring. 2 is a plan view (FIG. B) of the surface of the substrate 2 on which the mask jig 21 is mounted, as viewed from the front.

Here, only the parts different from the first embodiment will be described. As shown in FIG. 3A, the blocking portions 24 and 25 of the mask jig 21 are formed in a concave shape on the printed wiring board 2 side, and have bottom surfaces 24a and 25a and side walls 24b and 25b. Has become. In the first embodiment, the heat resistant tempered glass is used for the bottom surfaces 4a and 5a, but stainless steel is used for the bottom surfaces 24a and 25a of the present embodiment.

As shown in FIG. 3B, the bottom surfaces 24a, 25a are provided with a plurality of ventilation holes 26 having a diameter of 1.0 mm or less so that the molten solder does not pass through at regular intervals.

The reason for providing the plurality of ventilation holes 26 in this way will be described. As shown in FIG. 4, the conventional mask jig J1
When the surface of the printed wiring board J2 to be soldered is heated in the mounted state, the mask jig J1 is heated by the heater. Then, by the radiant heat of the heated mask jig J1, the mask regions J2b, J of the printed wiring board J2 are formed.
2c is heated. At this time, the mask regions J2b and J2
Air is trapped between c and the shielding portions J4 and J5 of the mask jig J1. The fact that this air acts as a heat insulating layer is also considered to be the reason why the temperature rise of the mask regions J2b and J2c is slow.

Therefore, in this embodiment, the mask jig 21 is used.
By installing a plurality of ventilation holes 26 on the bottom surfaces 24a and 25a of the shielding portions 24 and 25, the air between the mask regions 2b and 2c and the shielding portions 24 and 25 is heated by a heater outside the mask jig 21. I was supposed to replace the air. Therefore, in the preheating process, the temperature of the air between the mask regions 2b and 2c and the shields 24 and 25 rises faster than before. As a result, the mask area 2
Since the temperature rise of b and 2c can be accelerated, the heating efficiency of the entire printed wiring board 2 can be improved.

For reference, FIG. 2 shows the substrate temperature gradient during the preheating step when the mask jig 21 to which the present embodiment is applied is used. From this, it is understood that the mask jig 21 to which the present embodiment is applied has a higher temperature gradient and higher heating efficiency than the case of using the conventional mask jig J1.

Although the plurality of ventilation holes 26 in the shielding portions 24 and 25 are circular in FIG. 3, they may have other shapes.
Further, the intervals of the ventilation holes 26 may be such that the adjacent holes do not overlap each other.

Although the mask jig 21 is made of stainless steel, it may be made of another heat resistant material such as heat resistant resin.

[Brief description of drawings]

FIG. 1 is a cross-sectional view (upper side of the drawing) of a main part of a mask jig and a printed wiring board when the mask jig to which the first embodiment of the present invention is applied is mounted on the printed wiring board, and a print at this time. FIG. 6 is a plan view (lower side of the drawing) of the surface of the wiring board on which the mask jig is mounted as viewed from the front.

FIG. 2 is a diagram showing a comparison result of substrate temperature gradients during a preheating step when using the mask jigs of the first and second embodiments and a conventional mask jig.

FIG. 3 is a cross-sectional view (upper side of the figure) of the mask jig and the main part of the printed wiring board when the mask jig to which the second embodiment of the present invention is applied is mounted on the printed wiring board; FIG. 6 is a plan view (lower side of the drawing) of the surface of the wiring board on which the mask jig is mounted as viewed from the front.

FIG. 4 is a cross-sectional view (upper side of the figure) of the mask jig and the main part of the printed wiring board when the conventional mask jig is mounted on the printed wiring board, and the mask jig of the printed wiring board at this time is mounted. It is a top view (lower side of a figure) when the made side is seen from the front.

FIG. 5 is a diagram showing one step in a flow soldering method performed by mounting a mask jig on a printed wiring board.

[Explanation of symbols]

1 ... Mask jig, 2 ... Printed wiring board, 3 ... Frame part,
4, 5 ... Blocking section, 4a ... Bottom surface of blocking section, 6 ... Opening section, 7
... lead electronic parts, 8 ... electronic parts, 9 ... through holes.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B23K 1/08 B23K 1/08 Z 3/00 310 3/00 310P // B23K 101: 42 101: 42

Claims (6)

[Claims] 1. A mask jig (1) is mounted on a soldering surface of a printed wiring board (2), and an electronic component (7) is mounted on the printed wiring board (2) by a flow soldering method. A step of placing the electronic component (7) on the printed wiring board (2), and the electronic component (7) of the printed wiring board (2).
An opening (6) for exposing a predetermined area (2a) of the printed wiring board (2) including a portion to be soldered and a portion other than the predetermined area are shielded from the surface opposite to the surface on which is mounted. A step of mounting a mask jig (1) having a shield part (4, 5), the shield part (4, 5) being made of a heat-resistant material that transmits infrared rays; and the printed wiring board (2) A step of applying a solder flux to the surface on which the mask jig (1) is mounted and applying a solder flux to the predetermined area (2a); and radiating infrared rays after the step of applying the solder flux. Heating the predetermined area by the heating means, and heating infrared rays emitted from the heating means to the blocking portion to heat the area other than the predetermined area, and the step of heating the printed wiring board (2). After, before A step of soldering only the predetermined area (2a) by bringing molten solder into contact with the surface of the printed wiring board (2) on which the mask jig (1) is mounted. Electronic component mounting method. 2. The electronic device according to claim 1, wherein in the step of mounting the mask jig on the printed wiring board, the mask jig uses heat-resistant tempered glass for the shielding portion. How to mount parts. 3. A mask jig (1) is mounted on a surface of a printed wiring board (2) to be soldered, and an electronic component (7) is mounted on the printed wiring board (2) by a flow soldering method. A step of placing the electronic component (7) on the printed wiring board (2), and the electronic component (7) of the printed wiring board (2).
An opening (6) for exposing a predetermined area (2a) of the printed wiring board (2) including a portion to be soldered and a portion other than the predetermined area are shielded from the surface opposite to the surface on which is mounted. Mounting a mask jig (1) having a shielding part (4, 5), and the shielding part (4, 5) having a plurality of holes having a diameter of 1.0 mm or less; A step of applying solder flux to the surface of the printed wiring board (2) on which the mask jig (1) is mounted, and applying solder flux to the predetermined area (2a); and applying the solder flux. After the step, after heating the printed wiring board (2) by a heating unit, and after heating the printed wiring board (2), the mask jig (1) of the printed wiring board (2) Apply molten solder to the surface where Be to, electronic part mounting method characterized by having a step of performing soldering only in the predetermined region (2a). 4. A mask jig (which is mounted on the soldering surface of the printed wiring board (2) when the electronic component (7) is soldered to the printed wiring board (2) by the flow soldering method. 1) which is mounted on the printed wiring board (2) and is soldered to the frame portion (3) surrounding the printed wiring board (2) and the printed wiring board (2). An opening (6) for exposing a predetermined region including a portion to be performed and a shield (4, 5) for shielding the printed wiring board (2) other than the predetermined region are provided, and the shield transmits infrared rays. A mask jig for flow soldering, which is made of a heat-resistant material. 5. The mask jig for flow soldering according to claim 4, wherein heat-resistant tempered glass is used as the heat-resistant material that transmits the infrared rays. 6. A mask jig (1) mounted on a soldering surface of the printed wiring board (2) when an electronic component is soldered to the printed wiring board (2) by a flow soldering method. And a frame portion (3) surrounding the printed wiring board (2) when mounted on the printed wiring board (2), and a portion of the printed wiring board (2) to be soldered. The printed wiring board (2) includes an opening (6) for exposing a predetermined area including the shield and a shield (4, 5) for shielding the area other than the predetermined area of the printed wiring board (2).
A mask jig for flow soldering, wherein the mask jig has a hole of 0 mm or less.