JP2910720B2 - Soldering method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a soldering method, and more particularly, to a soldering method for mounting a surface mount component with multi-pin leads such as an LSI on a printed wiring board.

[0002]

2. Description of the Related Art Conventionally, in mounting electronic parts on a printed wiring board, for example, Japanese Utility Model Application Laid-Open No. 60-12406.
As described in Japanese Patent Publication No. 4 (1993), after solder is supplied on a printed wiring board with high precision by screen printing using a metal mask, electronic components are mounted, and the solder is performed by batch heating in a reflow tank. I was However, as electronic devices become smaller and more sophisticated,
High density on a flat surface has been achieved by increasing the number of terminals and fine pitch of electronic components such as SI, making it difficult to supply an appropriate amount of solder, leading to solder bridges between the lead terminals and insufficient solder. The connection failure due to the above has been a problem. Also, because of screen printing, once,
Once the components have been soldered, it has not been possible to later solder only some of the components or replace and resolder.

[0003] As a means for solving such inconveniences, a soldering method as disclosed in Japanese Patent Application Laid-Open No. 6-169165 has been proposed. In this method, after placing electronic components on a printed wiring board, a comb-shaped jig provided with a number of partition plates for partitioning between the lead terminals of the electronic components is provided. After being placed on the printed wiring board so as to be arranged, soldering is performed by supplying a solder paste and heating with hot air or the like. According to this method, the bridge due to the solder flow can be prevented, and it is also possible to retrofit some parts.

[0004]

However, the method described in Japanese Patent Application Laid-Open No. 6-169165 requires a special jig for each electronic component. Has the disadvantage of increasing costs.

The present invention has been made in view of the above circumstances, and has as its object to provide a soldering method for securely performing soldering without requiring a special jig.

[0006]

According to a first aspect of the present invention, there is provided a method for forming a photosensitive resin layer by applying a photocurable photosensitive resin on a printed wiring board. ,
By performing exposure and development processing on the photosensitive resin layer, the photosensitive resin layer on the wiring conductor of the printed wiring board, which occupies a portion to be joined of each lead terminal of the surface mount component with multi-pin leads, is set in an unexposed state. On the other hand, by removing the uncured portion and exposing and hardening the photosensitive resin layer occupying the non-conductive region between the adjacent portions to be joined by exposure and curing, a damping portion for preventing solder flow is formed between the wiring conductors. After mounting the surface mount component on the printed wiring board in a state where each of the lead terminals is in contact with the corresponding to-be-joined portion, a solder paste is supplied to the to-be-joined portion. The present invention relates to a soldering method for heating and melting the solder paste to join the wiring conductor and the corresponding lead terminal. With obtaining the photosensitive resin layer of the multilayer structure by performing repetition and the exposure of the resin layer alternately,
By narrowing the width of the exposure region so as to become an upper layer, the photosensitive resin layer occupying the non-conductive region between the portions to be bonded is cured to have a substantially trapezoidal cross section, and thereafter, by developing, An uncured portion of the photosensitive resin layer is removed to form the dam portion having a substantially trapezoidal cross section.

Further, according to a second aspect of the present invention, a photosensitive resin layer is formed by applying a photocurable photosensitive resin on a printed wiring board, and then the photosensitive resin layer is exposed and developed. On the wiring conductor of the printed wiring board, the photosensitive resin layer which occupies a site to be joined of each lead terminal of the surface mount component with multi-pin leads is unexposed and is uncured and removed, while the adjacent joining is performed. By exposing and hardening the photosensitive resin layer occupying the non-conductive area between the planned portions, exposure damping was formed between the wiring conductors to prevent solder flow, and a solder paste was supplied to the planned joining portion. Thereafter, the respective lead terminals are placed in contact with the corresponding portions to be joined, and the surface mount component is placed on the printed wiring board, and the solder paste is heated and melted, The distribution According to a soldering method for joining a conductor and the corresponding lead terminal, the application of the photosensitive resin and the exposure to the photosensitive resin layer formed by the application are alternately and repeatedly performed to form the multilayer structure. Along with obtaining a photosensitive resin layer, by narrowing the width of the exposure region to the upper layer, the photosensitive resin layer occupying the non-conductive region between the portions to be joined is cured to have a substantially trapezoidal cross section, and Thereafter, by performing a developing process, the uncured portion of the photosensitive resin layer is removed to form the dam portion having a substantially trapezoidal cross section.

[0008]

[0009]

[0010]

According to the structure of the present invention, since the dam portion for preventing the solder from flowing is formed in advance between the wiring conductors of the printed wiring board, the solder is supplied to the portion to be joined when supplying the solder. However, by performing the soldering by heating and melting the solder, there is no possibility of causing a connection failure due to, for example, a solder bridge or insufficient solder. Therefore, the yield can be improved. Also, for example, even after a plurality of surface-mounted components have been once soldered, only some of the surface-mounted components can be later soldered or exchanged and soldered again. Further, in forming the damming portion, soldering can be surely performed without requiring a special jig. Also, since the side wall surface of each damming portion forms an inclined surface, if the surface mount component is roughly aligned on, for example, a printed wiring board, each lead terminal of each surface mount component will follow the guide of the side wall surface. Since it is securely mounted on the conductor end of the corresponding printed wiring board, it is possible to reduce the delicate alignment work.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. The description will be specifically made using an embodiment. FIGS. 1 and 2 are process diagrams for explaining a soldering method according to a first embodiment of the present invention, and FIG. 3 is a printed wiring before dam formation to which the soldering method is applied. FIG. 4 is a plan view showing a configuration of a main part of the printed wiring board after the dam is formed. FIG. 5 is a plan view showing a configuration of a main part of the printed wiring board. FIG. 2 is a plan view showing a configuration of a main part of a module made of FIG. In the soldering method of this example, for example, a module having a predetermined electronic function is mounted by mounting a large number of surface-mounted components with multi-pin leads, such as an LSI in which a large number of lead terminals are provided at a fine pitch, on a printed wiring board. This is a suitable method to use when manufacturing. As shown in FIG. 5, the module 1 of this example has various surface mount components 3, 3,...

The printed wiring board 2 of this embodiment is shown in FIG.
As shown in FIG. 4D and FIG. 4, a wiring conductor pattern for connecting between the surface mount components 3, 3,... Is formed on the surface of the insulating substrate. The conductor ends 221, 221,... Of the conductors 22, 22,.
Are arranged at a pitch of approximately 0.5 mm so as to correspond to each direction of the surface mount component 3 having lead terminals in four directions. The printed wiring board 2 is formed in a predetermined region of each gap between the conductor ends 221 and 221 so as to partition the conductor ends 221 and 221 and has a side inclined to the side to which the solder 4 is supplied. It has dams 23, 24,... Having a wall surface and a height of, for example, approximately 1 mm. These dams 23, 24,... Are formed by curing a resin having a property that the solder does not wet, an insulating property, and a photo-curing property. Each of the dams 23 is provided between the conductor ends 221 and 221 arranged in one direction.
Are provided at the corners of the component mounting portion 21.

First, as shown in FIGS. 1A and 3,
Printed wiring board 2 on which wiring conductor pattern is formed
1A, the printed wiring board 2a is immersed in a liquid photocurable resin to form a photocurable resin layer L0 having a thickness of about 1 mm on the surface, as shown in FIG. 1B. Next, as shown in FIG. 3C, the beam diameter is set to be approximately 0.1 mm, for example, only in a predetermined area above each gap between the conductor ends 221 and 221 from above the photocurable resin layer L0. Is irradiated with a laser beam in the ultraviolet region to cure the photocurable resin, thereby forming a cured region La. At this time, the irradiation range of the laser beam is determined by the conductor ends 221 and
These are regions having a rectangular cross section having the width of the gap between the 221 and each region having a substantially square cross section at the corner of the component mounting portion 21 where each dam 24 is to be formed.

Next, the printed wiring board 2b, in which the hardened areas La are formed at the locations where the dams 23, 24,... Are to be formed, is immersed in a developing solution, and the light of the unhardened areas Lb remaining without being hardened is exposed. The curable resin is removed and further cleaned using a cleaning liquid. Here, the hardened resin in the hardened area La and the photocurable resin in the unhardened area Lb are immersed in the developing solution at a portion closer to the surface, so that the dams 23 and 24 having a smaller width are closer to the surface. , ... are formed. Thus,
As shown in FIG. 4D and FIG. 4, the printed wiring board 2 having the inclined side walls and the dams 23, 24,... Here, each dam 23,
24 side wall surfaces 231, 231 and 24 side wall surfaces 241, 241
Are inclined at a predetermined angle.

Then, as shown in FIG. 1 (e), the surface mount components 3, 3,... Are arranged such that each lead terminal 31 is disposed on the corresponding conductor end 221, 221,. Are mounted on the component mounting portions 21, 21,... Of the printed wiring board 2.
At this time, the tip of each lead terminal 31 is, for example, a dam 2
3 or the upper part of the side wall surface 241 of the dam 24, is guided along the inclination of each side wall surface 231, 241 to the corresponding conductor end 221 along the slope, and FIG.
As shown in (f), each lead terminal 31 is securely mounted on the corresponding conductor end 221 of the printed wiring board 2. Therefore, the component mounting portion 21 of each surface mount component 3 is within the distance between the uppermost portions of the dams 23, 23 (24).
What is necessary is just to perform positioning with respect to.

Next, as shown in FIG. 2G, a paste-like solder 4 is applied to the connecting portion between each lead terminal 31 and the conductor end 221 by using a dispenser 5.
Supply from above. Since the resin material forming the dams 23, 24,... Has a property that the solder does not wet, the solder 4 is applied to each of the lead terminals 31 and the conductor end portions in the region sandwiched between the dams 23, 23 (24). 221. Next, as shown in FIG. 5H and FIG. 5, for example, a laser beam in an infrared region is applied to each portion on which the solder 4 is mounted, and the solder 4 is heated and melted, and each lead terminal 31 is connected. Connect to conductor end 221.

At this time, the lead terminal 31 and the conductor end 221
The solder 4 supplied to each connection portion with the dam 23 (2
4), for example, does not flow into an adjacent connection point. Thus, a module 1 on which the surface mount components 3, 3,... Are mounted as shown in FIG. Thereafter, if some surface mount components 3, 3,... Are found to be defective and are to be replaced, or if some surface mount components 3, 3,. .. Are formed only at the locations, and the respective surface mount components 3 are placed, the solder 4 is supplied only to these locations, and the connection is performed by locally heating and melting using a laser beam. .

According to the above configuration, the dams 23, 24,... For preventing the flow of the solder are formed in the printed wiring board 2 between the conductor ends 221 and 221 in advance. When supplying, dams 23, 23 (24)
By supplying the solder 4 to the portion sandwiched by the solder and heating and melting the solder 4 to perform soldering, for example, a solder bridge can be prevented. Dams 23 and 2
By adjusting the heights of 4,..., The shortage of solder can be prevented. Therefore, there is no possibility of causing a connection failure. Also, for example, once a large number of surface mount components 3, 3,
Are soldered afterwards, or only some of the surface mount components 3, 3,... Can be later soldered or replaced and soldered again. At this time, the portions on which the respective surface mount components 3 are already mounted other than the necessary portions are not heated, so that the respective surface mount components 3 are not adversely affected.

Are coated with a photo-curable resin on the printed circuit board 2a and then exposed to a predetermined portion between the conductor ends 221 and 221 to cure the photo-curable resin. The soldering can be easily and reliably performed without requiring a special jig. Also, the side wall surface 2 of each dam 23 (24)
31 (241) form an inclined surface, so that when the surface mount components 3, 3,... Are roughly aligned on the printed wiring board 2, each lead terminal 31 of each surface mount component 3
According to the guidance of the side wall surface 231 (241), the semiconductor device is reliably mounted on the corresponding conductor end portion 221 of the printed wiring board 2, so that it is possible to reduce the delicate alignment work.

FIG. 6 is a sectional view for explaining a soldering method according to a second embodiment of the present invention. The second embodiment differs greatly from the first embodiment in that, as shown in FIG. 6, a portion located below the edge of the lower surface of the surface mount component 3 of the printed wiring board 2 is also different from the first embodiment. Dam 25, 25,
.. Are provided in advance along the parallel direction of the lead terminals 31. The rest is almost the same as the first embodiment,
The description is omitted.

According to the above configuration, by providing each dam 25, it is possible to prevent the solder 4 from flowing down below the surface mount component 3, so that an appropriate amount of the solder 4 can be supplied, and the solder 4 can be more reliably provided. Solder defects can be prevented.

Although the embodiment of the present invention has been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and there are design changes and the like that do not depart from the gist of the present invention. Is also included in the present invention. For example, in the above-described embodiment, the case where the heights of the dams 23, 24,... Are approximately 1 mm has been described. However, the height can be appropriately increased or decreased according to the supply amount of the solder which is considered appropriate. Further, in the above-described embodiment, the surface of the printed wiring board 2a is approximately 1 mm.
After forming a photocurable resin layer having a thickness of 3 mm, a case where the laser beam is irradiated once to the portions where the dams 23, 24, 25,... Are formed to cure the resin has been described. The formation of a photocurable resin layer having a thickness of 1 mm and the irradiation of a laser beam are repeated to form a multilayer structure, and the width of the irradiation range of the laser beam is made narrower toward the upper layer, so that the cross section of the cured portion is obtained. .. May be formed so as to have a substantially trapezoidal shape, and thereafter, the uncured resin is removed to form dams 23, 24, 25,.

Although the case where the dams 23, 24, 25,... Are formed by using a photo-curable resin as the photo-sensitive resin has been described, a method using a photo-soluble resin may be used. Further, the case where the solder 4 is supplied after placing each surface mount component 3 on each conductor end 221 sandwiched between the dams 23, 23 (24) of the printed wiring board 2 has been described. The surface mount components 3 may be placed after the solder 4 is supplied onto the portion 221. In addition, although the case of irradiating a laser beam in an infrared region to heat and melt the solder 4 has been described, for example, a halogen lamp or a xenon lamp may be used as a light source (heat source). Also, without heating locally using a laser beam, etc.,
For example, heating may be performed at a time using hot air. Also, the formed dams 23, 24, 25, ...
May be removed after soldering is completed.

[0024]

As described above, according to the structure of the present invention, a damming portion for preventing the flow of solder is formed in advance between the wiring conductors of the printed wiring board, so that when the solder is supplied, In addition, by supplying the solder to the portion to be joined and performing the soldering by heating and melting the solder, there is no possibility of causing a connection failure due to, for example, a solder bridge or insufficient solder. Therefore, the yield can be improved. Also, for example, even after a plurality of surface-mounted components have been once soldered, only some of the surface-mounted components can be later soldered or exchanged and soldered again. Further, in forming the damming portion, soldering can be surely performed without requiring a special jig. Also, since the side wall surface of each damming portion forms an inclined surface, if the surface mount component is roughly aligned on, for example, a printed wiring board, each lead terminal of each surface mount component will follow the guide of the side wall surface. Since it is securely mounted on the conductor end of the corresponding printed wiring board, it is possible to reduce the delicate alignment work.

[Brief description of the drawings]

FIG. 1 is a process diagram for describing a soldering method according to a first embodiment of the present invention in the order of processes.

FIG. 2 is a process chart for explaining the soldering method.

FIG. 3 is a plan view showing a configuration of a main part of a printed wiring board before dam formation to which the same soldering method is applied.

FIG. 4 is a plan view showing a configuration of a main part of the printed wiring board after the formation of the dam.

FIG. 5 is a plan view showing a configuration of a main part of a module in which surface mount components are mounted on the printed wiring board.

FIG. 6 is a sectional view for describing a soldering method according to a second embodiment of the present invention in the order of steps.

[Explanation of symbols]

 2 Printed Wiring Board (Printed Wiring Board) 22 Wiring Conductor 23, 24, 25 Dam (Damp) 3 Surface Mounted Component 31 Lead Terminal 4 Solder L0 Photocurable Resin Layer (Photocurable Resin)

Claims (2)

(57) [Claims] 1. A photo-curable photosensitive resin is applied on a printed wiring board to form a photosensitive resin layer, and the photosensitive resin layer is exposed and developed to form a photosensitive resin layer on the wiring conductor of the printed wiring board. While the photosensitive resin layer occupying the site to be joined of each lead terminal of the multi-pin leaded surface mounting component is unexposed and uncured and removed, while the non-conductive region between the adjacent sites to be joined is removed. By leaving the photosensitive resin layer occupied by exposure and curing, a damming portion is formed between the wiring conductors for preventing the solder from flowing, and each of the lead terminals is disposed in contact with the corresponding one of the planned joining portions. After the surface mount component is placed on the printed wiring board in a state where the solder is supplied, a solder paste is supplied to the portion to be joined, the solder paste is heated and melted, and the lead corresponding to the wiring conductor is provided. A soldering method for joining a terminal and the photosensitive resin layer having a multilayer structure by alternately and repeatedly performing application of the photosensitive resin and exposure to the photosensitive resin layer formed by the application. In addition, by narrowing the width of the exposure region toward the upper layer, the photosensitive resin layer occupying the non-conductive region between the portions to be joined is cured to have a substantially trapezoidal cross section, and then subjected to development processing. Thus, an uncured portion of the photosensitive resin layer is removed to form the dam portion having a substantially trapezoidal cross section. 2. A photo-curable photosensitive resin is applied on a printed wiring board to form a photosensitive resin layer, and then the photosensitive resin layer is exposed to light and developed to form a photosensitive resin layer on the printed wiring board. While the photosensitive resin layer occupying the site to be joined of each lead terminal of the multi-pin leaded surface mounting component is unexposed and uncured and removed, while the non-conductive region between the adjacent sites to be joined is removed. By leaving the photosensitive resin layer occupied by exposure and curing, a damming portion for preventing solder flow is formed between the wiring conductors, and after supplying the solder paste to the joining scheduled portion, the respective lead terminals are The surface mount component is placed on the printed wiring board in a state of being placed in contact with the corresponding portion to be joined, and the solder paste is heated and melted to form the lead corresponding to the wiring conductor. A soldering method for joining a terminal and the photosensitive resin layer having a multilayer structure by alternately and repeatedly performing application of the photosensitive resin and exposure to the photosensitive resin layer formed by the application. In addition, by narrowing the width of the exposure region toward the upper layer, the photosensitive resin layer occupying the non-conductive region between the portions to be joined is cured in a substantially trapezoidal cross section, and then subjected to development processing. Thus, an uncured portion of the photosensitive resin layer is removed to form the dam portion having a substantially trapezoidal cross section.