JP3343454B2 - How to join electronic circuits - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the joining of electronic circuits, and more particularly to a joining method and a solder composition for joining an electronic component to a circuit board without using a flux, and forming the solder on a connection terminal. Electronic components.

[0002]

2. Description of the Related Art Conventionally, soldering using a flux has been widely and generally performed for joining electronic circuit devices. Solder is connected by metal bonding between the solder and the base material to be connected, which constitutes the connection terminal.The surface of the solder and the base material to be bonded is usually covered with an oxide film or organic contaminant film. Therefore, even if the solder is heated and melted as it is, it is not joined. Therefore, by using the flux, the surface oxide film and organic contaminant film are chemically removed, and the flux covers the joint, thereby maintaining a clean surface state, preventing re-oxidation, and providing a good joint. Can be performed.

FIG. 7 shows a process chart of soldering on a general electronic circuit board. As shown in FIG. 1A, a solder paste composed of a solder powder 10 and a paste-like flux 11 covered with an oxide film 5 is applied to a metal mask or screen printing corresponding to the electrodes 2 on the printed circuit board 1. Supplied by Then, when the electrode (chip electrode) 6a of the electronic component 6 is positioned on the electrode 2 and heated, as shown in FIG. In order to remove the oxide film on the surface of the electrode 6a and the solder powder 10, as shown in FIG. 3C, when the melting point of the solder becomes higher than the melting point, the solder powder 10 agglomerates and spreads over the electrode 2 and the chip electrode 6a. . After the solder 3 is solidified, the flux residue 12 remains on the solder surface as shown in FIG. 4D, and is removed by washing, and the joining is completed as shown in FIG. As described above, in the soldering using the solder paste, it is possible to simultaneously and easily supply the solder and the flux having the effect of cleaning the surface of the solder and the surface to be joined and preventing re-oxidation.

However, with the recent miniaturization, high density, and multi-functionality of electronic circuit devices, solder joints have been miniaturized and highly integrated, and voids generated by flux being caught in the connection portions have become a problem. ing. Further, in the case where the flux is used, as shown in FIG. 7D, the flux residue 12 remains, which may cause corrosion, migration, or short circuit. Therefore, a cleaning step for removing the flux is required. Becomes Until now, cleaning has been performed using an organic solvent such as chlorofluorocarbon or trichloroethane, which has excellent cleaning properties. However, these cleaning agents cause an environmental problem that the ozone layer is destroyed.

In order to solve these problems, a fluxless solder connection method that does not use a flux and does not require cleaning has been studied. For example, the surface oxide film and organic contaminant film of the part to be joined and the solder material are removed (cleaned) by irradiating with an atom or ion beam, and the connection terminals of the electronic components are aligned with the electrodes on the circuit board in the air. A method is shown in which mounting is performed, and connection is performed by heating and melting in a non-oxidizing atmosphere to prevent re-oxidation. In addition,
Japanese Patent Application Laid-Open No. Hei 3-241755 discloses a fluxless solder connection of this type.

[0006]

However, the conventional fluxless solder connection method uses an atomic or ion beam in a vacuum chamber to clean the interconnecting surfaces in a vacuum chamber instead of using no flux. In order to prevent oxidation, the connection must be performed in a non-oxidizing atmosphere, and there is a problem that the mass production is inferior and the cost is high as compared with the connection using a solder paste that has been exclusively used conventionally.

[0007] In addition, in soldering with a solder paste, as described above, in addition to void defects and environmental problems, the amount of solder supplied by printing tends to be non-uniform. However, there is a problem that defects such as unconnection and a bridge occur. Furthermore, even in the fluxless solder connection, it is an important issue to supply the solder easily and efficiently to fine and multipoint connection parts.

Accordingly, an object of the present invention is to solve the above-mentioned conventional problems of soldering, and the main object is to be able to supply solder uniformly and easily, to be excellent in workability and productivity, and to reduce soldering. It is an object of the present invention to provide an improved method of soldering electronic circuits by means of a fluxless method, and another object of the present invention is to provide an improved solder capable of easily realizing this soldering method.
Still another object is to provide an electronic component in which this solder is formed on a connection terminal.

[0009]

SUMMARY OF THE INVENTION The above object, an electrode provided above the electronic circuit board, both the connection terminal of the electronic component, Ru <br/> is joined with the fluxless solder member the solder member in soldering method of an electronic circuit
Is a solder member containing a substance that can easily generate gas at a solder melting temperature at the time of solder connection, wherein the solder
The member is at least a joint of the electrode or the connection terminal .
It is supplied to one, and is formed on the surface of the solder member
The solder member is heated to a temperature at which the
Thereby bonding the two with a clean solder component
This is achieved by an electronic circuit joining method characterized by the following.

As the solder containing the gas generating agent of the present invention, generally used solder compositions such as Sn-Pb-based, Sn-Ag-based, Au-Sn-based and Sn-I
An n-based, Sn-Bi-based or the like as a base material, and a gas generating agent containing a suitable amount of a substance capable of easily gasifying at a solder melting temperature and breaking an oxide film on a solder surface with this gas pressure is used. Can be

As the gas generating agent, a substance which does not deteriorate the solder is selected in order to secure the reliability of the solder connection. Practically, for example, a hydrate of an organic compound is preferably used. A hydrate of an organic compound used as a dispersant (surfactant) in a solder plating solution, for example, a compound in which polyethylene glycol nonyl phenyl ether of a polyethylene glycol derivative is combined with water, polyoxypropylene polyoxyethylene glycol; Compounds in which water is bound, compounds in which polyethylene glycol and water are bound, and the like are mentioned. The hydrates of these organic compounds easily generate water vapor as a generated gas at the solder melting temperature.

A preferable amount of the gas generating agent contained in the solder is 10 to 100,0 in terms of a gas component.
It is about 00 wt ppm.

In the solder connection of an electronic circuit, the solder containing this gas generating agent is plated, for example, on a connection terminal of an electronic component or an electrode provided on an electronic circuit board.
Alternatively, in the case of using a solder powder, if a solder containing this gas generating agent is plated on the surface of a solder ball formed of a solder alloy base material or the like, connection is made by a normal solder connection method. be able to. The practical thickness of the solder plating is about 10 to 100 micrometers. The solder plating may be either electrolytic plating or electroless plating, but electrolytic plating is advantageous in terms of plating speed, and is suitable for forming a thick plating film.

As a method for introducing the gas generating agent into the solder, solder plating is effective as described above.
A predetermined amount of a hydrate of a dispersant (surfactant) may be added as a gas generating agent to the solder plating solution to perform plating.

Further, in order to make the solder connection more effective, when mounting the electronic component on the circuit board, the electronic component is preliminarily formed by using an adhesive which completes the curing before the solder is melted. It is effective to fix it on the substrate. As electronic components, surface-mounted components such as QFP, SOP, PLCC, chip components, and bare chip components such as flip chips and TAB can be joined. When the fixed electronic components and the circuit board are heated, the electronic components are fixed when the solder expands due to the generation of gas when the solder is melted. However, a force acts on the component to try to prevent it. For this reason, the oxide film is easily broken as compared with the case where no adhesive is used, so that bonding can be performed even when the oxide film is covered with a thicker oxide film.

The supply of solder can be formed not only on the electrode side of the circuit board but also on the connection terminal (electrode) side of the electronic component. When solder is formed on the electrode side of electronic components,
By mounting this component on the circuit board electrode, heating and melting, the generated gas was formed on the electrode of the electronic component,
The oxide film on the solder surface is broken, and a new solder surface is exposed and joined. In this way, the solder is supplied to the joint by combining the solder and a substance that generates a gas by boiling or a chemical reaction when the solder is melted.

Another object of the present invention is to form a thin film of a substance (gas generating agent) that generates a gas when the solder is melted in a partial area on an electrode of a circuit board, and apply the solder on the thin film. It is also achieved by a joining method of forming and soldering electronic components. According to this, when the solder is melted by heating, a gas is generated from the thin film containing the gas generating agent, so that the molten solder expands due to the gas pressure. Then, when the oxide film on the solder surface is broken and the gas is released, a new surface of the solder is exposed and joined. In this case, a normal solder containing no gas generating agent can be used, but using a solder containing a gas generating agent is more effective.

[0018]

The principle of the present invention will be specifically described with reference to the process chart of FIG. As shown in FIG.
The solder 3 containing the gas generating agent 4 is previously formed on the electrode 2 at the time of melting the solder. The surface of the solder 3 is usually covered with an oxide film 5. Electronic components 6 on this substrate
With.

As shown in FIG. 1B, when the solder 3 is heated, a gas 7 is generated from the gas generating agent 4 when the solder 3 is melted, and the solder expands. Then, when the solder expands until the breaking stress of the surface oxide film is exceeded, the oxide film 5 is torn, as shown in FIG. 3a is exposed.

Further, immediately before the new surface is exposed, the solder expands due to the gas, so that the part to be joined and the solder are in close contact with each other. The electrode 6a of the part to be joined is wetted and joined as shown in FIG. As a result, the solder can be wet and the connection can be made before the exposed new surface re-oxidizes. Furthermore, even when the new surface is re-oxidized due to atmospheric conditions or the like, a new gas is newly released, so that the new new surface is exposed and connection is possible. In addition, the solder 3
To provide uniform and fine pitch joints,
Moreover, the solder can be supplied easily.

The added gas generating agent generates a gas such as water vapor when the solder is melted, and this gas has an important function of breaking the oxide film on the solder surface. Depending on the type of gas generating agent used, some of the organic components that cannot be gasified react with the oxide film and decompose, and some have an action of reducing a part of the oxide to generate a solder alloy. .

[0022]

An embodiment of the present invention will be described below with reference to the drawings. <Embodiment 1> FIG. 1 is an enlarged sectional view of the vicinity of an electrode showing a typical embodiment of a solder connection according to the present invention. As shown in FIG. 1, a gas generating agent 4, for example, a dispersant in a solder plating solution is applied to an electrode 2 for connecting a chip component, for example, an electronic component (1608 component) such as a resistor or a capacitor, on a printed circuit board 1. The solder 3 containing 0.2 wt% (0.82 microgram per connection part in terms of gas component amount) of a compound in which polyethylene glycol nonyl phenyl ether of a polyethylene glycol derivative used as water is combined with water. By plating, a eutectic solder of Sn and Pb having a melting point of 183 ° C. is formed with a thickness of 60 μm, for example, to a thickness necessary for soldering.

Further, since the plating surface after the formation of the solder plating is exposed to the air, the oxide film 5 covers the entire surface. As the solder is heated, when the solder is melted, water is decomposed from the gas generating agent by thermal decomposition to generate steam gas. The oxide film 5 is broken by this gas pressure,
The new solder surface is exposed on the electrode 2, and the connection terminal of the electronic component (not shown) and the electrode 2 are joined by solder.

<Embodiment 2> FIG. 2 is a sectional view showing a step of soldering an electronic component (chip component) on a printed circuit board by using the solder supply method of the present invention. The process will be described below in the order of steps. First, as shown in FIG. 1A, for example, connection terminals (electrodes) 6a are provided at both ends.
The 1608 chip component 6 is positioned and mounted on the eutectic solder plating 3 of Sn and Pb supplied by the method shown in FIG.

Heating is performed in this state, and the melting point of the solder is 18
When the temperature reaches 3 ° C., the solder 3 is melted and the molten solder expands due to the steam gas 7 generated in the solder, as shown in FIG.

As shown in FIG. 3C, at the moment when the oxide film 5 on the solder surface is broken by the expansion due to gas generation, the steam gas 7 is released to the outside and the new solder surface 3 is formed.
a is exposed and spreads to the electronic component electrode 6a.

As a result, as shown in FIG. 2D, a fillet is formed and the chip component 6 is soldered on the printed circuit board.

Further, in the fluxless solder connection of the present invention, since there is no step of removing an oxide film by flux, atomic or ion beam irradiation as in the conventional case, the solder surface after joining is formed by the conventional soldering. Compared to the surface, as shown in FIG. 5D, the oxide film 5 is thickly covered, so that corrosion and the like can be prevented.

<Embodiment 3> FIG. 3 is a cross-sectional process diagram of soldering a chip component 6 in a state where the back surface of the chip component 6 has been previously bonded to a circuit board surface using an adhesive when mounting the chip component. . As shown in FIG. 1A, for example, in a eutectic solder plating 3 of Sn and Pb having a thickness of 60 μm, compound 4 in which polyoxypropylene polyoxyethylene glycol and water are combined as a gas generating agent is added in an amount of 0.1 μm. 2w
When the 1608 chip component (capacitor in this example) 6 is bonded to the electrode 2 using a solder containing t% (0.69 micrograms per connection portion in terms of gas component amount), the 1608 chip component 6 When aligning and mounting
The back surface of the chip component 6 is bonded and fixed on the circuit board surface with an adhesive 8 in advance. Note that, as the adhesive 8, an adhesive that completes curing before the solder is melted is used, similarly to the adhesive used in the normal mounting. For example, in the case of joining by eutectic solder of Sn and Pb, an epoxy-based adhesive with a curing condition of 120 ° C. is used.

Thus, as shown in FIG. 2B, the eutectic solder of Sn and Pb is melted by heating to generate steam gas 7, and when the solder 3 expands, the chip component 6
Is fixed to the circuit board, the oxide film 5 covering the surface of the solder is subjected to a force to expand from the inside and a force to prevent it from the electronic components 6 on the outside. Therefore, the oxide film 5 is easily broken. At the same time, the expanded solder is deformed by the fixing of the chip component 6, and the area of contact between the solder 3 and the chip component electrode 6a is increased. Therefore, as shown in FIG. When the film 5 is torn, the solder is easily wetted and spread, and the connection is made as shown in FIG. As described above, by the combination of the solder supply by solder plating and the adhesive according to the present invention, bonding can be performed even with a thicker oxide film, and the bonding method according to the present invention can be performed on a double-sided printed circuit board.

<Embodiment 4> FIG. 4 shows the same effect as in Embodiments 1 to 3 in which a thin film containing a gas generating agent 4 is formed in a partial area of the electrode 2 so as to be a base for the solder 3. FIGS. 7A and 7B are diagrams for explaining another embodiment of the present invention for obtaining the above-mentioned structure, wherein FIG. 7A is a plan view and FIG.

As shown in the drawing, a part of the electrode 2 connecting the electronic components on the printed circuit board 1 is exposed,
A substance (gas generating agent) 4 that generates a gas when the solder is melted is formed by bonding. For example, 0.5 mm pitch 20
When an 8-pin QFP is joined, the compound 4 in which polyethylene glycol and water are bonded to each electrode is adhered to the electrode 2 of the circuit board 1 with an adhesive within a range of 50% or less of the electrode surface area. By plating on this, Sn and P
The eutectic solder plating 3 of b is formed to a thickness of, for example, 60 micrometers. In this case, the compound 4 is supplied in an amount of 0.4 wt% of the supplied solder amount (0.73 microgram per connection portion in terms of gas component amount).

In order to facilitate the formation of the plating, the compound 4 is adhered at intervals using a predetermined mask as shown in FIG. Further, since the surface of the solder plating 3 is exposed to the atmosphere, the oxide film 5 is spontaneously formed and covers the entire surface. Thus, when the electronic component 6 is mounted and heated in the same manner as in the process of FIG. 2 shown in the second embodiment, steam gas is generated when the solder is melted.
As in the case shown in the step (c), the oxide film 5 on the solder surface can be broken, and the new solder surface is exposed and joined.

In this embodiment, a solder containing no gas generating agent is used as the solder 3. However, it goes without saying that a solder containing a gas generating agent may be used similarly to the first and second embodiments. .

<Embodiment 5> FIG. 5 is a sectional process view showing an embodiment of the solder material of the present invention. In the following, according to the steps, FIG. 1A shows a step of forming a solder ball 3b, which is manufactured by spraying molten solder from a nozzle by a normal manufacturing method. Here, a eutectic solder ball of Sn and Pb is used as an example.

Next, as shown in FIG. 3B, a eutectic solder 3 of Sn and Pb containing a compound 4 in which polyethylene glycol nonyl phenyl ether and water were bonded was formed on the surface of the solder ball by electroplating. . The oxide film 5 is spontaneously formed on the surface of the solder ball manufactured as described above with the passage of time.

The solder ball in which the solder plating layer 3 containing the gas generating substance 4 is formed on the surface layer in the above steps is
It is used for circuit connection in the same way as the solder balls used so far, but is superior in terms of fluxless solder.

That is, in the solder connection, the parts to be joined can be joined by breaking the surface oxide film 5 by the same action as in FIG. By using such a solder material, it is possible to perform soldering without using flux in the process shown in FIG.

Further, in a solder paste using such a solder material, an oxide film on a solder surface is more easily broken than in a conventional solder paste. Therefore, even when a flux containing almost no activator such as a carboxylic acid, an aliphatic amine, or an addition salt of an aliphatic amine that chemically removes an oxide film is used, solder bonding can be performed. It is thought that cleaning without solder bonding is also possible.

<Embodiment 6> FIG. 6 is a sectional view of an electronic component, showing an embodiment of an electronic component manufactured by using a solder material containing the gas generating substance 4 of the present invention. As shown, for example, the solder 3 containing the substance 4 that generates a gas when the solder is melted is placed on the electrode 6a of the 1608 chip component 6 by, for example, a compound obtained by combining polyethylene glycol and water at 0.2 wt% ( A solder containing 0.86 micrograms per connection part in terms of the gas component amount) is formed to a thickness of 60 micrometers by, for example, electroplating.

The surface of the solder 3 is covered with a spontaneously formed oxide film 5. However, the use of the electronic component 6 allows the oxide film to be easily broken by gas generation at the time of solder connection, thereby enabling highly reliable bonding. By using the component in which the solder containing the gas generating substance 4 is formed in advance on the electrode surface of the electronic component as described above, the solder joining process of the second embodiment shown in FIG.
Further, since the solder is easily wetted and spread, solder joining can be performed in a shorter time.

[0042]

As described in detail above, the intended object has been achieved by the present invention. In other words, by supplying a solder in combination with a substance that generates a gas when the solder melts, the solder is generated without using a flux requiring a cleaning step and without requiring a step of removing a surface oxide film of the solder. With the use of the gas, the connection can be made by breaking the surface oxide film to expose the new surface. Also,
Since there is no step of removing the entire oxide film on the solder surface, the oxide film is thickly covered even after bonding, and the oxide film itself has an effect of preventing contamination and corrosion. Further, the supplied solder protects the electrodes from oxidation and organic film contamination, and at the same time, supplies a necessary amount of solder for soldering. Further, when the solder is supplied by plating, the solder can be supplied stably to the fine joint. For this reason, it is excellent in workability and mass productivity, and enables low-cost fluxless solder connection.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a solder supply method according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a soldering step, which serves as an explanation of the principle of the present invention and one embodiment.

FIG. 3 is a sectional view showing a soldering step according to another embodiment.

FIG. 4 is an explanatory view showing still another solder supply method.

FIG. 5 is a cross-sectional view showing one embodiment of the same solder material.

FIG. 6 is a sectional view showing one embodiment of the electronic component.

FIG. 7 is a process chart of soldering using a conventional solder paste.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Printed circuit board, 2 ... Electrode, 3 ... Solder, 3a ... New surface of solder, 3b ... Ball-shaped solder, 4 ... Substance which generates gas when solder melts, 5 ... Oxide film, 6 ... Electronic component, 6a ... Electronic component electrode , 7 ... gas, 8 ... adhesive, 10 ... solder powder, 11 ... flux, 12 ... flux residue.

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Mamoru Mita 2-1-2 Marunouchi, Chiyoda-ku, Tokyo Inside Hitachi Cable, Ltd. (56) References JP-A-6-155068 (JP, A) JP-A-6 −226485 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H05K 3/34 B23K 35/14 B23K 35/26 H05K 3/24

Claims (9)

(57) [Claims] An electrode provided above an electronic circuit board;
Both the connection terminal of the electronic component, the soldering method of the electronic circuits to be joined using a fluxless solder member, the solder member, as a substance capable of generating easy gas at solder melting temperature at the time of solder connection Organic compounds
A solder member containing a hydrate , wherein the solder member is supplied to at least one of the electrode and the connection portion of the connection terminal, and until a temperature at which an oxide film formed on the surface of the solder member is broken. A method for joining electronic circuits, comprising heating and joining the two using a clean solder component of the solder member. An electrode provided above the electronic circuit board;
Use a fluxless solder for both the connection terminals of the electronic components.
Soldering method for electronic circuits that are joined using solder members
In the above, the solder member is used for solder melting at the time of solder connection.
Solder part containing a substance that can easily generate gas at temperature
Material, the solder member at least the electrode or
Supply to any of the joints of the connection terminals, and
To a temperature at which the oxide film formed on the
Heating, using the clean solder component of the solder member,
Joining the two and soldering the electronic component onto the electronic circuit board, using an adhesive that finishes curing before the solder member is melted, and bonds the electronic component to the circuit board. a step of preliminarily bonded and fixed to the upper
A method for joining electronic circuits, comprising: An electrode provided above the electronic circuit board;
Use a fluxless solder for both the connection terminals of the electronic components.
Soldering method for electronic circuits that are joined using solder members
In the above, the solder member is used for solder melting at the time of solder connection.
Solder part containing a substance that can easily generate gas at temperature
Material, the solder member at least the electrode or
A plating process is applied to any of the joints of the connection terminals.
And an oxide film formed on the surface of the solder member
Is heated to a temperature at which the solder member breaks.
A method for joining electronic circuits, wherein the two are joined using a solder component . In wherein said plating step, during solder plating solution, it was added a hydrate of an organic compound used as a dispersant surfactant as a substance capable of generating the gas,
4. The method for joining electronic circuits according to claim 3, further comprising a step of solder plating. 5. An electrode provided above an electronic circuit board,
Use a fluxless solder for both the connection terminals of the electronic components.
Soldering method for electronic circuits that are joined using solder members
Oite, on a part of at least said electronic circuit board electrodes, leave thin a substance capable of generating a gas when the solder is melted into a film form, comprising a step of forming a solder thereon How to join electronic circuits. 6. A method for soldering an electronic circuit in which both an electrode provided on an electronic circuit board and a connection terminal of an electronic component are joined by a fluxless solder connection. A method for joining electronic circuits, comprising a step of partially forming a thin film of a substance capable of generating a gas when the solder is melted in a region, and forming a solder thereon. 7. A fluxless solder material in which a surface of a solder ball formed of a solder alloy base material is coated with a solder plating containing a substance capable of generating a gas when the solder is melted. 8. An electronic component having a connection terminal formed with solder plating containing a substance capable of easily generating gas at a solder melting temperature at the time of solder connection. 9. A method for manufacturing an electronic component, comprising: a step of plating a connection terminal of the electronic component in a solder plating solution containing a substance capable of generating a gas when the solder is melted when the solder is plated.