JP3414263B2 - Manufacturing method of electronic circuit board - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an electronic circuit board on which an LSI, components, etc. are mounted on an electronic circuit board, and more particularly to a method for manufacturing an electronic circuit board mounted using Pb-free Bi solder.

[0002]

2. Description of the Related Art It is known that when a Pb-free Bi-based solder is soldered by a normal flow process, the Cu land portion of the substrate and the solder are separated (called lift-off). It is known that lift-off is caused by the segregation of Bi in Sn-Bi solder (Suganuma: Proceedings of the Circuit Packaging Academic Conference, p67, H10.3.24).

The mechanism of this lift-off is complicated and not clarified, but it is known that the lift-off can be prevented by quenching with water or steam spray (H10).
4.27 Nikkan Kogyo Shimbun, Osaka University).

[0004]

However, if the material is rapidly cooled with water or steam spray, the segregation of Bi disappears, but cracks occur in the solder, thermal shock to the parts, and adverse effects of the cooling liquid (contact, corrosion, etc.). ) Problem.

It is an object of the present invention to provide a method for manufacturing an electronic circuit board which improves the connection reliability between an electronic component and a circuit board using a lead-free solder containing Bi and has few connection failures. In particular, it is an object of the present invention to improve the connection reliability by optimizing the temperature profile at the time of solder connection and to provide a method for manufacturing an electronic circuit board with few connection failures.

[0006]

In order to achieve the above object, the present invention is a method for manufacturing an electronic circuit board for connecting an electronic component and a circuit board using Pb-free solder containing Bi, The solder is cooled at a cooling rate of about 10 to 20 ° C./s to connect the electronic component and the circuit board.

A method of manufacturing an electronic circuit board, in which an electronic component and a circuit board are connected by using Pb-free solder containing Bi, wherein a temperature from near the liquidus temperature of the solder to near the solidus temperature is obtained. The electronic component and the circuit board are connected by cooling at a cooling rate of about 10 to 20 ° C./s.

[0008] A method of manufacturing an electronic circuit board for connecting an electronic component and a circuit board by using Pb-free solder containing Bi, wherein the temperature from near the liquidus temperature of the solder to near the solidus temperature One in which the temperature range is cooled at a first cooling rate of about 10 to 20 ° C / s, and then at a second cooling rate slower than the first cooling rate to connect the electronic component and the circuit board. Is.

The second cooling rate is 0.1 to 5 ° C.
That is / s.

A method of manufacturing an electronic circuit board, in which a Pb-free solder containing Bi is used to connect an electronic component and a circuit board, wherein a temperature range below a solidus temperature of the solder is 0.1 or less. It cools at a cooling rate of ~ 5 ° C / s.

In addition, the above-mentioned cooling is performed by air, an inert gas,
It is performed by using a refrigerant such as spray liquid, vapor, liquid, liquid nitrogen, dry ice, etc., at least at room temperature or lower.

Further, the inert gas is a mixture containing any one of liquid nitrogen, dry ice, liquid nitrogen and dry ice.

Further, a flux cleaning liquid such as a Fluorinert liquid at least at room temperature or lower is supplied by spraying or showering to cool it.

According to an experiment, if the material is rapidly cooled at 10 to 20 ° C./s in this manner, even if the electronic component and the circuit board are connected using the lead-free solder containing Bi, the solder does not crack. confirmed. That is, it was confirmed that it is possible to provide a method for manufacturing an electronic circuit board with few defective connections by rapid cooling at 10 to 20 ° C./s.

If the temperature below the solidus temperature is gradually cooled at 0.1 to 5 ° C./s, even if the electronic component and the circuit board are connected using the lead-free solder containing Bi, the solidus line It was also confirmed by experiments that the stress due to the temperature difference from the temperature to the room temperature is relaxed and the solder does not crack. That is, it was confirmed that it is possible to provide a method for manufacturing an electronic circuit board with few connection defects by gradually cooling below the solidus temperature at 0.1 to 5 ° C./s.

Furthermore, by combining these two types of rapid cooling and gradual cooling, it becomes possible to manufacture a comprehensively excellent electronic circuit mounting board.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a lift-off mechanism will be described with reference to FIG.

(A) shows cracks in the land portion of the through-hole cross section, and (b) shows SEM (scanning electron microscope) observation of the appearance of the solder, showing lift-off of the land portion. (c) is a model of an example in which a through hole having the Cu pad shown in (a) and (b) and a Cu lead inserted in the through hole are connected by soldering.

As shown in FIG. 2C, the cause of lift-off is that the difference in the coefficient of thermal expansion in the thickness direction of the substrate is significantly larger than that of the leads (pins). When it occurs due to a large temperature difference from the line temperature to room temperature (), and when it occurs due to the time difference of solder solidification during cooling ((-1): Since the component side is metal, the fillet tip as shown in the figure If the Bi part collects on the land part ((-2): product ( Bi) is formed, and even if the product (Bi) is not formed, strength is reduced due to the influence of Bi). Note that -1) is due to the temperature difference between the liquidus and solidus lines and the solidification process, and -2) is due to the segregation of Bi (the relationship is shown in FIG. 4 described later).

Next, in order to elucidate the lift-off phenomenon of Pb-free Bi-based solder, Sn-3mass% Ag (hereinafter, simply referred to as Sn-
Various experiments were conducted on solder with Ag as an abbreviated parameter) and Bi content as a parameter, and the phenomenon was considered from the data and physical properties of the material.

The lift-off test sample is a DIP (Dual Inl
Pins of (ine Package) were inserted into a through hole of a 1.6t glass epoxy board with 6 layers, flux with a little acid was applied to rosin, and it was immersed in a solder bath to change the cooling rate of the joint. . The experiment in which the cooling rate was changed was performed in the atmosphere and water (hot water) where the experiment was easy. The cooling rate was measured by fixing the tip of the thermocouple on the land with heat-resistant tape. Soldering conditions are 250 ° C. for 3 seconds for all compositions.
The hole diameter of the board is 1.0 mm and the land diameter is 1.6 mm. For the lift-off, the appearance was observed with a low-magnification electron microscope, and the length of the peeled portion around the land was used as a scale.

FIG. 1 shows Sn-3Ag solder with Bi content of 0, 2, 4, 7, 10, 1.
4 shows the relationship between the Bi amount when 5% is added and the length of the lift-off peeled portion (crack length).

It was found that lift-off occurred in all compositions at a cooling rate of about 1 ° C./s (black circles), which is the cooling rate in normal flow soldering.

Next, in order to greatly change the cooling rate, water is added.
Tried at room temperature and in hot water (100 ° C). 5-40 for water and hot water
It could be changed in the range of ° C / s. From this experiment, it was found that there is no lift-off and the appearance (no cracks occur) is excellent in hot water cooling (black square mark) with a cooling rate of 10 to 20 ° C / s. It was also found that water cooling with a cooling rate of about 40 ° C / s (black triangle mark) does not cause lift-off, but is not as good in appearance as water cooling. That is,
It was found that when the cooling rate was 40 ° C / s, cracking occurred because the cooling rate was too fast, which was not practical.

As the cooling rate was increased, the segregation of Bi could be prevented.

As described above, in order to suppress the segregation of Bi, which is considered to be one factor of lift-off, it is better to increase the cooling rate, but in order to suppress solder cracking, the cooling rate is about.
It turned out that it is better to be slower than 40 ° C / s. Especially 10 ~ 20
It was found that the cooling rate of ° C / s was good. Further, it was found that the factor shown in FIG. 2 can be solved because the partial time difference of solder solidification disappears by quenching.

On the other hand, in the case of Sn-3Ag, the reason why lift-off occurs even when Bi does not exist is due to the factor shown in FIG. 2, and a large thermal stress due to a large temperature difference from 221 ° C. to room temperature. I couldn't stand it, and found that lift-off occurred. That is, the thermal expansion coefficient (70 × 1
0-6 / ° C) is lead material (42 alloy: 4 × 10-6 / ° C, Cu-based: 17 × 10-)
6 / ° C) and solder (20 × 10-6 / ° C) are much larger than that of the solder.Therefore, it may occur because the board shrinks greatly in the thickness direction until the solder solidifies at 221 ° C and cools down to room temperature. Do you get it. Therefore, in order to suppress thermal stress, which is considered to be one factor of lift-off, the temperature below the solid layer wire temperature of the solder is set to 0.1
It has been found that slow cooling at ~ 5 ° C / s is preferable.

Next, FIG. 4 shows the results of FIG. 1 and FIG. 2 more clearly and shows the relationship between the Sn—Ag—Bi solder composition and the physical properties, melting characteristics, strength and the like. The ternary eutectic (S
The ratio of (n-1Ag-57Bi) is that Sn-3Ag has 1 Bi as shown in FIG.
Structure in 5% composition (coarse Sn crystal and fine Sn-1Ag
-57Bi ternary eutectic) and differential heat (DSC) curve at 137 ℃
The area Q1 of the reaction region of the ternary eutectic (Sn-1Ag-57Bi) was determined, and the area ratio of the two was determined with the area Q0 obtained from the DSC of the ternary eutectic as 100%.

As shown in FIG. 4, when Bi is 7.5% or more, the interface strength is low (-1), and a ternary eutectic exists.
In addition, the temperature difference ΔT () between the liquidus line and the solidus line also increases, and lift-off tends to occur. However, when it becomes a ternary eutectic (Sn-1Ag-57Bi) containing a large amount of Bi, the temperature difference ΔT
And the solidus temperature (137
Since the temperature difference from (° C) to room temperature (20 ° C) is small, lift-off does not occur. On the other hand, a composition containing less Bi, for example,
At around 2%, almost good results were obtained even when the cooling rate was 10 ° C / s or less. That is, the composition with less Bi has a higher solidus temperature,
The temperature difference between the liquidus line and the solidus line is small, and the strength of the bonding interface is high. For this reason, lift-off is less likely to occur, and the cooling rate can be around 5 ° C / s.
From this, lift-off is due to the temperature difference between the liquidus and solidus lines,
It was found that it depends on the interrelationship between the cooling rate and the strength of the interface, and naturally, it also affects the composition.

As described above, the cause of the decrease in the strength of the joint interface depends on the Bi amount. As can be seen from Fig. 1, it can be seen that the curve is bent around 4 to 6% Bi. It is expected that the phenomenon will be different at this inflection point. Above this inflection point, since there is a ternary eutectic containing a large amount (57%) of Bi with a low melting point, it is expected that Bi will bond with each other and become coarse, and segregate along the interface. It is clear that when Bi, which is originally hard to react with Cu, gathers at the Cu interface, it easily peels off due to lack of adhesion with Cu.

On the other hand, when Bi is below this inflection point, that is, when the solder has a relatively high melting point, a uniform Bi phase is not observed at the interface. However, even with a solder having a small amount of Bi, at the land interface of final solidification, although there is not enough amount to segregate Bi at the interface as a solidification process, it is expected that Bi will gather near the interface. As a result, Bi in FIG. 4 is related to the cause of strength reduction at 0 to the inflection point.

When Bi increases in this range, the strength decreases linearly, but in this range, Bi at the bonding interface is XMA.
It is a level that cannot be analyzed and is not considered to be the segregation of Bi. So far, in Sn-Pb based solder, it has been confirmed that the presence of Bi in the solder inhibits the compound formation with Cu-Sn, which is one of the causes of the strength reduction, and the interface strength of the solder It has been confirmed that the Bi content decreases as the Bi content increases (Yamamoto et al .: Journal of Japan Circuit Packaging Society, Vo
It is considered that this case is also phenomenologically similar, since l.10, No6 (1995.9))). That is, as Bi increases,
At the interface, it is presumed that the net joint between Cu and Sn is reduced in a very thin layer at the molecular level, resulting in a decrease in strength. The presence or absence of a ternary eutectic according to the DSC curve as the bulk material of the solder differs depending on the temperature gradient of heating and cooling, but since it appears almost in this vicinity, it is considered that there is a series of relationships. The boundary value of this Bi at the interface is delicate, and it is expected that some deviation will occur because it greatly affects the diffusion depending on the presence or absence of heat treatment and aging.

From the above experimental results, as a process condition for eliminating lift-off, precipitation of Bi at the interface is avoided by quenching at a solidus temperature at which solidification is completed at 10 to 20 ° C./s. It was found that it is desirable to disperse Bi in the solder to prevent the decrease in strength due to the segregation of Bi at the interface. As a result, it was confirmed experimentally that there was no Bi layer that was originally deposited at the interface, and that Bi was dispersed in a wide range in the solder due to rapid cooling. Also,
It was also confirmed that the solder did not crack.

On the other hand, the main factor causing defects upon rapid cooling is temperature change in a short time. Therefore, in order to reduce the generation of thermal stress, it has been found that it is desirable to gradually cool the temperature below the solidus temperature at 0.1 to 5 ° C./s to relax the stress due to the temperature change for a short time.

By the way, since the cooling rate is related to the heat capacity of the substrate, it is necessary to cool the substrate with a refrigerant having a solidus temperature or lower in order to enhance the cooling effect. In particular, when the refrigerant is a gas, the heat capacity of the gas is small. Therefore, in order to enhance the cooling effect, the temperature cannot be rapidly cooled unless the temperature is lowered to room temperature or lower and the initial cooling effect is not enhanced. Even if a gas cooled to below room temperature is used in the first stage, the thermal shock to the components and the substrate is not bad. The advantage of using gas is that it does not destroy the flux that is coated as a protective film after soldering and does not affect the contact parts inside the connector.

Therefore, as a desirable process, it is desirable to cool rapidly from the vicinity of the liquidus line to the solidus temperature during cooling, solidify in a short time, and then gradually cool to release the stress. . The ideal cooling medium is a liquid, and one having a boiling point near the solidus temperature of the solder is ideal for cooling performance. In the case of Fluorinert, it is possible to select the material to some extent. By rapidly becoming vapor from the liquid, latent heat is taken away and a cooling effect can be achieved.

Since the ternary eutectic is precipitated in the system in which Bi is more than 7.5%, the solidus temperature here is 137 ° C. Similarly, in order to improve the cooling effect, the cooling temperature can be lowered within a range in which there is no thermal influence on the substrate and components. However, the mechanical properties of the solder itself, especially elongation, are
Since a tendency similar to the interface strength characteristics shown in Fig. 4 is exhibited, lift-off can be avoided for compositions with a large amount of Bi depending on the dimensions and structure of the substrate and parts, but cracks (grain boundary cracks) in the solder itself can be avoided. ), Sn crystal grain boundary defects (micro void generation) appear. In the case of 15% Bi solder, even in the case of rapid cooling immersed in 100 ° C. hot water (10 ° C./s), it is not limited to the case of water shown in the upper part of FIG. . The cause of this is that large stress can be relaxed in the whole solder, but it is a defect that occurs because the mechanical properties of the solder itself are poor due to the large amount of Bi. Therefore Bi
In order to approach an ideal process in a system with a lot of solids, it is necessary to quench to the solidus and then slowly cool. 15% Bi
100 ℃ with solder containing solder and 137 ℃ with silicone oil
As a result of confirming the effect of quenching in, the superiority of 137 ° C was recognized in appearance.

On the other hand, in the case of solder containing 4% Bi containing Bi of 7.5% or less, the solid phase temperature is 200 ° C. However, even with 100 ° C. hot water (10 ° C./s), room temperature water (40 ° C./s) However, lift-off can be prevented, and defects such as cracks (grain boundary cracks) and micro voids cannot be found. However, comparing the appearance photographs of both, it is clearly superior to the case of dipping in water at 100 ° C. (middle row in FIG. 5) to the system containing less Bi (lower row in FIG. 5). Therefore, in a system with a small amount of Bi, it is possible to lower the solidus temperature to 100 to 150 ° C, which is lower than that, in order to improve the cooling effect. The reason why defects are less likely to occur is that the bulk solder has good mechanical properties. That is, Bi
The smaller the number, the better the joint can be obtained.

In the case of the method of cleaning the flux, 100 is used near the solidus temperature of the solder or in a system with little Bi.
By spraying or showering with Fluorinert or the like that can be carried out at up to 150 ° C, the cleaning and cooling effects can be expected at the same time. In this cleaning and cooling process, a cooling cleaning liquid recovery system is essential. In the case of the cleaning method, it is a necessary condition that the flux components are dissolved in the cleaning liquid.

In the case of water or water spraying, it is necessary to use a water-soluble flux, but halfway cleaning is a problem. In the case of water, the cost is low, but problems such as dirt, corrosion, and rust on the contact points of the connector and the like remain, so that the structure is also limited.

The mainstream is the flux-less cleaning,
In the case of the cleaning-less system, it is desirable to blow cooled air or nitrogen as a refrigerant from both sides of the substrate to prevent oxidation at high temperatures. At first, cool air or nitrogen is blown, and when the solidus temperature level of the solder is reached, by gradually cooling with normal air, the flux protective film is not destroyed and thermal shock to the board, parts, etc. is prevented. It is possible without giving. When a liquid such as water is used as the refrigerant, the coating film for the flux may be locally damaged by hot water, shower, spray water, or uneven adhesion may cause deterioration of the insulation, which is a troublesome problem. Becomes It is necessary to make the cooling method possible without cracking the flux coating. When water is used, it is important to evaporate instantly so that impurities do not remain at the contact point. Considering the influence of the residue, the process should also consider purity.

As a method of immersing in a liquid, a method of mainly cooling the soldering surface side is also possible. When using a connector, a process of dipping the soldering surface in the liquid in a manner similar to soldering is also possible to prevent liquid from entering the connector. Also, at this time,
On the component side, gas, spray, shower or the like may be combined. The temperature of the liquid needs to be controlled to be constant.

Next, FIG. 6 shows an example of application of double wave nitrogen atmosphere to flow soldering. Reference numeral 1 denotes a nitrogen chamber unit, which shows a cross section (upper stage) and a plan view (lower stage) in which the printed circuit board 6 on which the component 7 with the pin 8 is mounted passes through the primary jet nozzle 9 and the secondary jet nozzle 10 and shifts to the cooling step. An example of using Sn-3Ag-7.5Bi (liquidus line: 210 ° C, solidus line: 188 ° C) is shown. Immediately after the flow of the substrate, a curtain of the heat shield plate 3 is provided between the furnace and the cooling mechanism to cool the substrate rapidly without disturbing the flow of the nitrogen atmosphere, and a heat resistant film 15 is attached to the tip of the substrate to pass the mounted components. It is designed so that it will not interfere. Cooling air 5 and 4 introduced from the cooler flows between the heat shield plates and between the cooling plates 2 thereafter flows from the nozzle 14. The nitrogen 11 coming out of the nitrogen chamber 1 is sucked upward and downward (a part of the nitrogen or the air 5 coming out from the heat shield plate is also mixed) to enhance the cooling effect. Nitrogen or air coming out between the heat shield plates and air coming out between the cooling plates are mainly sucked on both sides 12 when the substrate is present. 13 is the temperature of the land part of the substrate when passing through each part, which was adjusted to 245 ° C. at the soldering part and 210 ° C. which is the liquidus temperature of the solder immediately after passing through the heat shield plate 3. At the time of passing through the cooling plate, the temperature was set to about 180 ° C, which is lower than the solidus temperature of the solder of 188 ° C. Depending on the sample, 150 ℃ (137 ℃ or higher)
It is effective even if cooled in. During this time, by cooling at 10 ° C / s, lift-off can be prevented. Temperature in the lower part of Fig. 6
The profiles of (t) and time (s) are shown. The temperature gradient of the board land at the point A where the material is rapidly cooled becomes 10 ° C / s. When a ternary eutectic appears, it is necessary to consider 137 ° C as the solidus temperature. In order to improve the cooling performance, it is effective to lower the temperature of the coolant, increase the flow rate, and slow the substrate speed. For quenching, it is effective to make the refrigerant liquid. In some cases, if a heat-retaining part at the liquidus temperature is provided, the influence of the turbulence on the flow part is eliminated, so that the cooling is facilitated. It should be noted that at 180 ° C. or lower, it is necessary to cool while relaxing the residual stress and strain, so it was slowly cooled at about 1 ° C./s. This provides a healthy joint. With other solder compositions, the lift-off prevention process control suitable for the melting characteristics of the solder can be performed in the same manner.

Next, FIG. 7 shows an example of introduction into a flux cleaning-less process which does not use nitrogen. A model is shown in which the heat shield plate 3 is immersed in the Fluorinert liquid 17 having a high boiling point for cooling, and the surface of the component 7 may be sprayed with nitrogen or air 16, or Fluorinert may be sprayed or sprayed by a shower. . This is possible with a series of flow steps, and the Fluorinert flow bath is kept at a constant temperature by a cooler. The substrate temperature control process can be the same as that shown in FIG. In this case, when water is used instead of Fluorinert, temperature control and impurity control are important.

By introducing the quenching process in the flow as described above, the effect of the quenching effect of the flow on the already joined reflow joint can be expected. Since it is possible to prevent segregation of Bi in the joint due to reflow caused by rapid cooling, high reliability can be expected.

Although the Sn-Ag-Bi lead-free solder has been described above as an example, the lift-off phenomenon occurs due to the temperature difference between the liquidus line and the solidus line even in a system without Bi. , This means that other Sn systems, such as Sn-Sb system, Sn-Cu system,
It is also possible in Sn-Zn system, Sn-In system, etc.,
It goes without saying that similar measures and methods can be applied. As a matter of course, Ag is not limited to 3%.

[0047]

According to the present invention, it is possible to improve the connection reliability between an electronic component and a circuit board using a lead-free solder containing Bi and to provide a method for manufacturing an electronic circuit board with few connection failures. it can. Especially by optimizing the temperature profile during solder connection, the connection reliability is improved,
It is possible to provide a method for manufacturing an electronic circuit board with few connection failures.

[Brief description of drawings]

FIG. 1 is a relationship between Bi amount and land solder crack length.

FIG. 2 shows a lift-off phenomenon of a glass epoxy substrate and its mechanism.

FIG. 3 shows the principle of the method for measuring the amount of ternary eutectic contained in Bi solder.

[Fig. 4] Bi content and physical properties, melting characteristics, and Sn-Ag-Bi solder
The relationship of strength etc. is shown.

FIG. 5 shows an appearance observation of a through hole joint by a SEM photograph.

FIG. 6 is a cross-sectional view and a plan view showing an application example of a nitrogen atmosphere to flow soldering.

FIG. 7 is a cross-sectional view showing an application example to flow soldering.

[Explanation of symbols] 1 ... Nitrogen chamber 10 ... Secondary jet nozzle 2 ... Cooling plate 11 ... Nitrogen 3 ... Heat shield plate 12 ... Suction 4 ... Cooling air 13 ... Temperature 5 ... Cooling air 14 ... Nozzle 6 ... Printed circuit board 15 ... Film 7 ... Parts 16 ... Nitrogen, air 8 ... Pin 17 ... Fluorinert liquid 9 ... Primary jet nozzle 18 ... Moving direction

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hidee Shimokawa, 292 Yoshida-cho, Totsuka-ku, Yokohama, Kanagawa Prefecture, Ltd. Production Engineering Research Laboratory, Hitachi, Ltd. (72) Koji Serizawa, 292 Yoshida-cho, Totsuka-ku, Yokohama, Kanagawa Incorporated company Hitachi Ltd., Production Technology Laboratory (72) Inventor Yasuo Amano 292 Yoshida-cho, Totsuka-ku, Yokohama City, Kanagawa Prefecture Incorporated Production Technology Laboratory, Hitachi, Ltd. (72) Satoshi Sakaguchi Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture 292 In stock production company Hitachi, Ltd. Production Technology Research Laboratory (72) Inventor Hiroshi Yamaguchi 292 Yoshida-cho, Totsuka-ku, Yokohama, Kanagawa Prefecture Inside Production Technology Research Laboratory Hitachi, Ltd. (56) Reference JP-A-9-326554 (JP , A) JP-A-8-150493 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H05K 3/34 B23K 31/02 B23K 35 / 26

Claims (6)

(57) [Claims] 1. A method of manufacturing an electronic circuit board for connecting an electronic component and a circuit board using a Pb-free solder containing Bi, comprising: from a liquidus temperature of the solder to a solidus temperature thereof. A method of manufacturing an electronic circuit board, characterized in that the electronic component is connected to the circuit board by cooling at a cooling rate of about 10 to 20 ° C./s. 2. A method of manufacturing an electronic circuit board for connecting an electronic component and a circuit board using a Pb-free solder containing Bi, comprising: from a liquidus temperature of the solder to a solidus temperature thereof. The temperature range is cooled at a first cooling rate of about 10 to 20 ° C / s, and then at a second cooling rate slower than the first cooling rate to connect the electronic component and the circuit board. A method for manufacturing an electronic circuit board, comprising: 3. The method for manufacturing an electronic circuit board according to claim 2, wherein the second cooling rate is 0.1 to 5 ° C./s. Wherein air, an inert gas, spray, vapor, liquid, liquid nitrogen, according to claim 1, characterized in that cooled by at least below room temperature of the refrigerant such as dry ice 3
A method for manufacturing an electronic circuit board according to any one of 1. 5. The method of manufacturing an electronic circuit board according to claim 4 , wherein the inert gas is a mixture containing any one of liquid nitrogen, dry ice, liquid nitrogen, and dry ice. 6. The Fluorinert solution method of manufacturing an electronic circuit board according to any one of claims 1 to 4, characterized in that cooling is supplied by spraying or shower at least below room temperature flux cleaning liquid, such as.