JPH08267281A - Microcapsule containing antioxidant, antioxidation member containing this microcapsule and soldering method using this microcapsule - Google Patents

Abstract

PURPOSE: To make it possible to form a nonoxidizing atmosphere for soldering purposes. CONSTITUTION: Microcapsules 1 are incorporated into a flux 4 stored in a flux tank 3. An inert gas is sealed in these microcapsules 1. The flux 4 into which the microcapsules 1 are incorporated adhere to the prescribed points of a printed wiring board 5 passing the flux tank 3. The shells of the microcapsules 1 which come into contact with molten solder 7 are melted and deformed and the inert gas is released when the printed wiring board is moved to a soldering stage in this state. Consequently, the nonoxidizing atmosphere 8 is formed and the good soldering is executed in the atmosphere.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antioxidant-containing microcapsule, an antioxidant member including the microcapsule, and a soldering method using the microcapsule.

[0002]

2. Description of the Related Art When electronic parts are soldered to a printed wiring board, a flux is used for the purpose of removing an oxide film on the soldered part and preventing oxidation during heating. However, the flux contains an activator for the purpose described above, and the flux remaining after soldering may corrode the wiring board. Therefore, a method to prevent corrosion from occurring by cleaning the soldered part of the wiring board after soldering has been taken, but the CFC used for cleaning cannot be used due to environmental problems and other cleaning methods are also available. It is difficult to spread due to cost reasons. Further, a flux containing a weak activator for eliminating the need for cleaning and a flux containing a reduced amount of the activator are known, but there is a problem that solderability is poor.

Further, a method of supplying an inert gas such as nitrogen gas from the outside to perform soldering in an inert gas atmosphere has been proposed, but a facility and a large amount of equipment for maintaining the inert gas atmosphere are proposed. Since it requires gas, it is difficult to spread because of cost.

Furthermore, in recent years, a method has been proposed in which cream solder containing an alkylazo compound capable of generating nitrogen gas under soldering conditions is used to form a non-oxidizing atmosphere locally for soldering. (Japanese Patent Laid-Open No. 4-351287).

[0005]

In the cream solder containing the alkylazo compound described in the above publication, all the alkylazo compounds may not vaporize due to the heat of soldering depending on the alkylazo compound used.
As a result, the residual alkylazo compound may be deteriorated to have corrosive properties, or the soldered part may be discolored. Therefore, there is a problem that the alkylazo compound used is limited.

The present invention solves the above problems and uses an antioxidizing agent-containing microcapsule capable of preventing corrosive residues from being generated in a soldered portion, an antioxidizing member including the microcapsule, and the microcapsule. An object is to provide a soldering method.

[0007]

SUMMARY OF THE INVENTION The present invention for solving the above problems and achieving the object is to seal an inert gas or a substance that generates an inert gas by heating, and thermally deform it at a soldering temperature. The first characteristic is that the microcapsules are composed of a shell of a polymer resin that melts.

The present invention is also characterized in that an antioxidant member is constituted by a support having both sides coated with an adhesive and the microcapsules attached to one side of the support by the adhesive.
The third feature is that the case having the gas release hole and the microcapsules housed in the case constitute an antioxidant member. Further, the present invention has a fourth feature in that the case is further provided with a leg fitted into a socket fixed to a printed wiring board.

Further, the present invention has two types of shells: a shell made of a polymer resin which is thermally deformed or melted at the residual heat temperature of soldering, and a shell made of a polymer resin which is thermally deformed or melted at the main heating temperature. A fifth feature is that two types of microcapsules are supported by the support or housed in a case.

A sixth feature of the present invention is that the inside of the case is partitioned by a partition plate, and the two types of microcapsules are respectively partitioned by the partition plate and housed in the case. is there.

Further, the present invention uses a flux or cream solder mixed with the microcapsules enclosing an inert gas, in a non-oxidizing atmosphere by the inert gas released from the microcapsules by heating during soldering. The seventh feature is that soldering is performed.

Further, according to the present invention, the antioxidation member supporting or accommodating the microcapsules is arranged adjacent to the soldering position, and the non-oxidizing gas generated by the inert gas released from the microcapsules by heating during the soldering is used. The eighth feature is that soldering is performed in an oxidizing atmosphere.

[0013]

According to the first feature, the shell of the microcapsule is thermally deformed or melted by the heating at the time of soldering,
An inert gas is released that is effective to shield the soldered part from the atmosphere. According to the second and third characteristics,
It is possible to provide a means for supporting the microcapsules near the soldering part. According to the fourth feature, the legs of the case accommodating the microcapsules can be fitted and held in the sockets fixed to the printed wiring board.

Further, according to the fifth feature, the shells of the two types of microcapsules are thermally deformed or melted in stages at the residual heat temperature of soldering and the main heating temperature to release the inert gas. Further, according to the sixth feature, since the inside of the case is partitioned by the partition plate, the microcapsules that are thermally deformed or melted at the residual heat temperature move to the other partitioned, and are still thermally deformed or melted. It is possible to prevent the microcapsule from being attached to the microcapsule or blocking the gas discharge hole of the case.

Further, according to the seventh feature, the microcapsules attached to the soldering portion by the flux or cream solder are thermally deformed or melted by heating during soldering. As a result, the soldered portion can be shielded from the atmosphere in a non-oxidizing atmosphere of the inert gas released from the microcapsules.

According to the eighth feature, the microcapsules supported or housed by the oxidation preventing member are adjacent to the soldering position, and the non-active gas released from the microcapsules due to the heating during the soldering is used. The soldering part can be shielded from the atmosphere in an oxidizing atmosphere.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings. FIG. 1 is a sectional view of a microcapsule (hereinafter, simply referred to as “capsule”) according to an embodiment of the present invention. The core 2 of the capsule 1 is filled with an inert gas such as nitrogen or argon for forming a non-oxidizing atmosphere around the soldering portion at the time of soldering, or a substance for generating the inert gas. . As the shell 1a of the capsule 1, that is, the outer wall, a material that reaches a melting point or a heat deformation temperature at a soldering temperature is preferably used, and a material that appropriately expands in accordance with the expansion of gas accompanying a temperature rise is preferable. For example, polymer resins such as polyamide, polyester, melamine resin, epoxy resin and phenol resin are suitable. Further, as the substance that generates the inert gas when heated, for example, an alkylazo compound can be used.

As a method for encapsulating the alkylazo compound in the core 2 of the capsule 1, a well-known capsule preparation method,
For example, an underwater drying method or a spray drying method (spray drying method) can be used. When an inert gas is filled as the core 2 of the capsule 1, the capsule prepared by the above method is further processed as follows. That is, the capsules are dried under reduced pressure to remove the solvent and water inside the capsules and left in a desired inert gas atmosphere to replace the inside of the capsules with an inert gas. If necessary, the shell 1a of the capsule 1 may be coated with the same substance as that of the shell or a resin having a lower melting point than the shell, and heated at a temperature not lower than the glass transition point and not higher than the melting point to provide airtightness to the shell 1a.
The diameter of the capsule is the reflow soldering method described later,
For example, those of 20 to 50 μm are suitable, and those of up to several mm can be used in the flow soldering method. Regarding the capsule preparation method, "Granulation Handbook", No. 59, published by Ohmsha, edited by Japan Powder Industrial Technology Association.
Pages 61-61 and 435-437, or JP-A-6-192068.

Next, a soldering method using the gas filled capsule will be described step by step. FIG. 2 is a schematic diagram showing the steps of the flow soldering method according to the first embodiment of the present invention. In the same figure (a), the process of applying the flux to the soldering position is shown. In the figure, a flux 4 is stored in a flux tank 3, and this flux 4 is agitated by an agitating means (not shown) such as a motor to form a wave 4a as shown. The flux 4 is a mixed liquid of alcohol and an extract of rosin, that is, pine resin, and in this embodiment, the capsule 1 containing an inert gas is further mixed in the mixed liquid.

A printed wiring board 5 to be soldered is passed over the wave 4a of the flux 4. Electronic components 6 are temporarily fixed to the upper surface and the lower surface of the printed wiring board 5, and resist treatment is applied to the portions other than the wiring portion so that solder does not adhere to them. When the printed wiring board 5 passes over the flux tank 3, the wave 4 of the flux 4 is generated.
The flux 4 is applied in contact with a.

After the process of applying the flux 4 is completed, the soldering process is started. FIG. 2B is an enlarged view of the printed wiring board transported to the jet portion of the molten solder. In the figure, the printed wiring board 5 is conveyed in the direction of the arrow above the jet portion, and immediately before it comes into contact with the molten solder 7, the gas in the capsule 1 in the flux 4 thermally expands and melts or thermally deforms from the capsule 1. To form a non-oxidizing atmosphere 8. In this atmosphere, the molten solder 7 is attached to a predetermined wiring portion and soldered.

Next, an example of using the capsule 1 for reflow soldering will be described. FIG. 3A shows a process of applying cream solder to the soldering position of the printed wiring board 5. In the figure, a mask 9 is overlaid on the printed wiring board 5, and cream solder 10 is applied on the mask 9.
The capsule 1 is mixed in the cream solder 10. When the printing squeegee 11, that is, the scraping plate is moved in the direction of the arrow while contacting the surface of the mask 9, the cream solder 10 is extruded from the through hole of the mask 9 to the printed wiring board 5 and applied at a desired position.

In the printed wiring board 5 thus coated with the cream solder 10, the component 6 is temporarily fixed and transferred to the reflow bath. In the reflow bath, as shown in FIG. 3B, infrared rays or hot air 12 is irradiated to heat the cream solder 10 and thermally deform or melt the capsule 1. As a result, the expanded gas is released and a non-oxidizing atmosphere 8 is formed, and in this atmosphere, the cream solder 10 adheres to a predetermined wiring portion and is soldered.

Next, a second embodiment of the present invention will be described. FIG. 4 is a cross-sectional view showing a sealing tape as a means for fixing the capsule 1 in the vicinity of the soldering portion. In the figure, the seal tape 13 is a support 14 and a support 1
4 has the pressure-sensitive adhesive 15 applied to both surfaces thereof, and the capsule 1 applied to one surface of the support 14 having the pressure-sensitive adhesive 15 applied thereto. Further, a release liner 16 is attached to the side of the support 14 on which the capsule 1 is applied. The release liner 16 comprises a release paper 17 and layers of release agents 18 and 19 formed on both sides thereof. When the release liner 16 is used as a finished product in a state where the seal tape 13 is wound in a reel shape, when the capsule tape 1 is used, the capsule 1 is not attached to the adhesive 15 in the adjacent layer. It is provided to avoid the problem of adhesion. Therefore, when the seal tape 13 is used in the vicinity of the soldered portion, the peeling learner 16 is peeled off to expose the capsule 1 as shown in FIG. 4B.

FIG. 5 is a diagram showing a soldering mode using the seal tape 13. In the figure, a connection pad 20 is formed on the printed wiring board 5, and a cream solder 21 is applied thereon. The connection pad 20 coated with the cream solder 21 has I
The leads 22 of the component 6 such as C are arranged. In this state, hot air or infrared rays 12 are irradiated for soldering. In the second embodiment, the seal tape 13 is arranged adjacent to the connection pad 20. The seal tape 13 is adhered to the printed wiring board 5 with the adhesive 15. At this time, as described above, the sealing tape 13
The release liner 16 has been peeled off, and the capsule 1 is exposed on the surface. Therefore, the capsule 1 is melted or thermally deformed by the irradiation of the hot air or the infrared rays 12 to release gas from the inside, and soldering is performed in a state where the non-oxidizing atmosphere 8 is formed.

FIG. 6 is a diagram showing a flow soldering process. In the figure, the seal tape 13 is the lead 2 of the component 6 on the back surface of the printed wiring board 5, that is, on the side of the molten solder 7.
Attach it adjacent to 2 in advance. When the molten solder 7 is passed through the flow tank in this state, the hot air of the molten solder 7 melts or thermally deforms the capsule 1 to release gas from the inside, and soldering is performed in a state where the non-oxidizing atmosphere 8 is formed. Be implemented. It should be noted that FIG. 3B is an enlarged view of the sticking portion of the seal tape 13.

As described above, according to the second embodiment, the capsule 1 is arranged apart from the soldering portion.
Therefore, even when the capsule 1 is filled with, for example, an alkylazo compound as an inert gas generating substance, the residue of the compound does not adhere to the printed wiring board 5, the connection pad 20 or the like, and thus the cleaning can be omitted.

The following materials can be used for the elements such as the support 14 constituting the seal tape 13. For example, crepe paper, Kapton, and polyetherimide can be used for the support 14, and the release paper 17 can be
Polylami kraft, high quality polylami paper, crepe coated paper, gramin paper, and plastic film can be used. Also,
The pressure-sensitive adhesive 15 is a silicon-based pressure-sensitive adhesive containing silicon rubber as a main component, a rubber-based pressure-sensitive adhesive in which resin is dispersed in natural rubber or synthetic rubber, and an acrylic pressure-sensitive adhesive which is a copolymer containing butyl acrylate as a main component. A release agent can be used.
Silicon resin, wax, and fluorine resin can be used for 19.

Next, a third embodiment of the present invention will be described. In the above-described second embodiment, the sealing tape type is used to arrange the capsule 1 near the soldering portion, but in the third embodiment, the capsule 1 is housed in the case and the case is mounted on the printed wiring board 5. I attached it to. FIG. 7A shows
It is a perspective view showing a case accommodating the capsule 1.
FIG.7 (b) is the same front view. Further, FIG. 7C is a front view showing a case with a lid. In the figure, the capsule 1 is housed in the case 23, and the case 23 is formed with innumerable holes 23a so that the inert gas released from the capsule 1 at the time of soldering can flow out. The case 23 in FIG. 7 (b) is sealed after the capsule 1 is stored, and in principle, once used, it cannot be reused. On the other hand, the case 23 of FIG. 7 (c) has a lid 23b so that the capsule 1 can be replaced and reused after use. The case 23 may be made of ceramic, polyphenylene sulfide, polyamide, polybutyl terephthalate (PBT), or the like. Also, the hole 2
3a does not necessarily have to be formed on the entire surface of the case, and holes 23a may be formed only on the side surface facing the soldering portion, for example, so that the inert gas can efficiently flow to the mounting portion.

FIG. 8 shows a case 23 containing the capsule 1.
It is a figure which shows the aspect of the soldering using. The same code | symbol as FIG. 5 shows the same or equivalent part. In the figure, the case 23 is arranged adjacent to the connection pad 20.
The case 23 is fixed to the printed wiring board 5 by the case 2
This is performed by inserting the leg 23c of No. 3 into the hole (not shown) formed in the printed wiring board 5. With this arrangement, the capsule 1 is irradiated with hot air or infrared rays 12.
Is melted or thermally deformed to release gas from the inside, and soldering is performed in a state where the non-oxidizing atmosphere 8 is formed.

The case 23 is not limited to being directly inserted into the hole of the printed wiring board 5, but for example, a socket provided in the printed wiring board 5 for inserting components such as a memory and a relay is used. be able to. The socket is a well-known socket in which parts such as the memory can be freely attached and detached, and an example is shown in FIG. In the figure, the socket 24 has a lead 24a protruding downward and a socket fitting 24b connected to the lead 24a.

The leg 23c of the case 23 is connected to the socket 24
The socket metal fitting 24b has a space or size that matches the socket metal fitting 24b. Therefore, when soldering, the socket 24
The case 23 can be inserted and used, and after soldering, the case 23 can be removed from the socket 24 and a component such as a memory that should be originally inserted in the socket can be attached. In this way, there is no need to specially provide a space for mounting the case 23 on the printed wiring board 5. Of course, if a space can be secured on the printed wiring board 5, a socket dedicated to the case 23 may be provided.

In the above embodiments, the capsule 1 is made of a material that melts or is thermally deformed at the soldering temperature. However, in the reflow soldering method using cream solder, the material of the capsule 1 can be selected as follows. More desirable.
That is, the reflow soldering method includes a two-step heating process. FIG. 10 is a diagram showing a thermal history in the reflow soldering method. As shown in the figure, in reflow soldering, preheating is first performed to evaporate the solvent component in the creme solder. The heating temperature at this time is about 150 °
It is C. Following this preheating, main heating is performed to melt the solder and join the printed wiring board 5 and the component leads. The heating temperature of this main heating is about 230 ° C.
Is. In each of these two-step heating process, the lead or cream solder is oxidized and the soldering performance is deteriorated. Therefore, it is desirable that the shielding action by the inert gas works in each of these two stages of heating.

In view of the above heat history, two kinds of capsules 1 having shells 1a made of two kinds of materials having different melting points are mixed in cream solder, adhered to the seal tape 13 or stored in the case 23. By doing so, it is convenient because the gas can be released from the capsule 1 in stages corresponding to the preheating and the main heating. For example, polyamide is used as the low melting point capsule and acrylic resin is used as the high melting point capsule.

FIG. 11 is a sectional view of the seal tape according to the fourth embodiment, showing an example in which two types of capsules 100 and 101 having different melting points are attached to the seal tape 13. In addition, FIG. 12 shows the capsule 10 in the case 23.
It is sectional drawing of the case 23 which shows the example which accommodated 0 and 101. In FIG. 12, one of the capsules 100 and 101 having a lower melting point is melted and the holes 23 are formed by the preheating.
Capsules 100 and 1 to prevent a being blocked
01 was partitioned by the partition plate 23d and stored.

With this construction, first, the low melting point capsule is melted or deformed by heat in advance to generate the inert gas enclosed as the core 2, or the inert gas generating substance generates gas to shield the gas. Then, in the subsequent main heating, the high melting point capsule is thermally deformed or melted to generate the inert gas enclosed as the core 2, or the inert gas generating substance generates gas to perform the shielding function.

[0037]

As is apparent from the above description, according to the invention of claim 1 or 2, the capsule shell is thermally deformed or melted by heating at the time of soldering, and the soldered portion is exposed to the atmosphere. An inert gas effective to shield is released.

According to the invention of claims 3 to 5, it is possible to provide means for supporting the capsule for releasing the inert gas in the vicinity of the soldering portion. Particularly, according to the feature of claim 5, the case is fitted into the socket fixed to the printed wiring board to hold the capsule, and after the soldering, the case is removed from the socket and originally attached to the socket. The parts to be attached can be attached. As a result, the space on the surface of the printed wiring board can be effectively used.

According to the inventions of claims 6 and 7,
The shells of the two types of microcapsules undergo thermal deformation or melting stepwise at the preheating temperature for soldering and at the main heating temperature to release an inert gas. Particularly, according to the invention of claim 7, since the inside of the case is partitioned by the partition plate,
Microcapsules that have been thermally deformed or melted at the preheating temperature move to the other partition, and adhere to the microcapsules that have not yet been thermally deformed or melted, or block the gas release holes of the case. Can be prevented.

According to the inventions of claims 8 to 9,
The microcapsules attached to the soldered portion by the flux or cream solder are thermally deformed or melted by heating during soldering. As a result, the soldered portion can be shielded from the atmosphere in a non-oxidizing atmosphere of the inert gas released from the microcapsules.

According to the tenth aspect of the present invention, the microcapsules forming the antioxidation member are adjacent to the soldering position, and the solder is applied in a non-oxidizing atmosphere due to the inert gas released from the microcapsules by heating during the soldering. The attachment part can be shielded from the atmosphere.

As described above, according to the inventions of claims 1 to 10, oxidation at the time of soldering can be prevented. In particular, in the soldering method using a microcapsule in which an inert gas is filled as an antioxidant, a corrosive residue is not generated after soldering, so that the printed wiring board cleaning step for removing the residue can be omitted. .

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a microcapsule encapsulating an antioxidant according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing flow soldering showing a first embodiment of the present invention.

FIG. 3 is a schematic view showing reflow soldering showing a first embodiment of the present invention.

FIG. 4 is a sectional view of a seal tape according to a second embodiment of the present invention.

FIG. 5 is a schematic view showing reflow soldering showing a second embodiment of the present invention.

FIG. 6 is a schematic diagram showing flow soldering showing a second embodiment of the present invention.

FIG. 7 is a perspective view and a front view showing a case according to a third embodiment of the present invention.

FIG. 8 is a schematic view showing reflow soldering showing a third embodiment of the present invention.

FIG. 9 is a schematic view showing a fixing means of the case according to the third exemplary embodiment of the present invention.

FIG. 10 is a diagram showing a heat history in a soldering process.

FIG. 11 is a sectional view of a seal tape according to a fourth embodiment.

FIG. 12 is a sectional view of a case according to a fourth embodiment.

[Explanation of symbols]

1 ... Microcapsule, 1a ... Shell, 2 ... Core, 4 ...
Flux, 5 ... Printed wiring board, 6 ... Parts, 7
... Molten solder, 8 ... Non-oxidizing atmosphere, 10 ... Cream solder, 13 ... Seal tape, 14 ... Support, 1
5 ... Adhesive agent, 16 ... Release agent, 23 ... Case, 24
…socket

Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location H05K 3/34 512 7128-4E H05K 3/34 512C

Claims (10)

[Claims] 1. A microcapsule containing an antioxidant, characterized in that a shell is made of a polymer resin which is filled with an inert gas and thermally deforms or melts at a soldering temperature. 2. A microcapsule containing an antioxidant, characterized in that a substance which generates an inert gas by heating is enclosed and a polymer resin which is thermally deformed or melted at a soldering temperature is used as a shell. 3. A support having both sides coated with an adhesive, and one side of the support attached with the adhesive.
Alternatively, an antioxidation member comprising the microcapsule according to 2. 4. An antioxidant member, comprising: a case having a gas release hole; and the microcapsule according to claim 1 or 2 housed in the case. 5. The antioxidant member according to claim 4, further comprising a leg fitted into a socket fixed to the printed wiring board. 6. The microcapsule has two types of shells, a shell made of a polymer resin that is thermally deformed or melted at a residual heat temperature of soldering, and a shell made of a polymer resin that is thermally deformed or melted at a main heating temperature. It is two kinds of microcapsules which it has, It is characterized by the above-mentioned.
The antioxidant member according to any one of 1. 7. A partition plate for partitioning the inside of the case is further provided, and the two types of microcapsules are respectively partitioned by the partition plate and housed in the case. The antioxidant member described. 8. Soldering is performed in a non-oxidizing atmosphere formed by the inert gas released from the microcapsules by heating during soldering, using the flux containing the microcapsules according to claim 1. A soldering method characterized by the above. 9. The solder paste is mixed with the microcapsule according to claim 1, and soldering is performed in a non-oxidizing atmosphere formed by the inert gas released from the microcapsule by heating during soldering. A soldering method characterized by performing. 10. The oxidation preventing member according to claim 3 is arranged adjacent to a soldering position, and is formed by an inert gas released from the microcapsules by heating during soldering. A soldering method characterized by performing soldering in a non-oxidizing atmosphere.