JP2000061628A - Fusion joining method and mounting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To mount parts a plurality of times using a brazing tiller metal of the same temperature characteristic. SOLUTION: A solder plated on a terminal 14 of a mounting parts 12 is exposed to and fluoridated by a mixed gas of HF gas and steam, and then, arranged on a gold bump 32 of a circuit substrate 30. The fluoridated solder is melted at the temperature lower than the melting point before fluoridation by 20-50 deg.C. The circuit substrate 30 with the mounting parts arranged thereon is placed in a reflow furnace 34, and heated to the temperature lower than the melting point of the solder before fluoridation to melt the solder and the terminal 14 is soldered to the gold bump 32.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a joining method for melting a brazing material and joining materials to be joined, and particularly to a fusion joining method and mounting suitable for multi-chip mounting for mounting various electronic components on a mother board. Regarding the method.

[0002]

2. Description of the Related Art In recent years, with the increasing precision and miniaturization of electronic equipment, various electronic components such as semiconductor chips and resin connectors are mounted on a circuit board such as a printed wiring board using surface mounting technology. I am trying to do it. To mount electronic components on a printed wiring board, solder, which is a brazing material, is applied to predetermined positions on the printed wiring board, and a large number of electronic components are placed on the solder and heated in a reflow oven. , The solder is melted (melted) to join many electronic components at once.

However, there are cases where it is not possible to mount all the electronic components at once, and it may be necessary to mount them all at once. In this case, the circuit board is heated each time. Then, in such a case, if the solder material having the same melting point is used, the solder of the previously joined component will be melted to cause a joint failure. Therefore, in general, for the component to be joined first, the solder having the high melting point is used and joined later. A solder with a lower melting point is used for the parts to prevent the solder of the previously joined parts from melting. Further, when all the components cannot be mounted at once, there is also a method of locally heating only the vicinity of the components to be mounted on the circuit board later and melting and joining only a part of the solder portion.

[0004]

When the above-mentioned electronic components are divided and mounted on a circuit board several times, various kinds of solders having different melting points are used to prevent the solder of the previously joined components from melting. It is troublesome to use. In addition, the solder for joining the electronic components has a lower limit of the melting point of 180 ° C. in consideration of the use environment of a device in which the circuit board on which the components are mounted is incorporated. Difficult to use in the environment. Furthermore, for example, electronic components such as resistors and capacitors have a heat resistance temperature of about 250 ° C., and the melting point of solder is 250 due to the heat resistance of the components.
℃ is the upper limit. That is, the melting point of solder that can be used in electronic devices has a lower limit of about 180 ° C. and an upper limit of about 250 ° C. Therefore, even if it is possible to prepare several kinds of solder having different melting points in this temperature range, it is difficult to finely control the temperature when mounting the electronic component, and even if it is possible to do so. Productivity is significantly reduced.

Moreover, when melting a metal, it is known that the metal does not actually melt unless the temperature is higher by about 40 ° C. than the melting point of the metal itself, and solder is no exception. Therefore, in actual soldering, the melting point of the solder is 40
Considering the heat damage to the components caused by heating the circuit board many times, it is performed by heating to a high temperature of around ℃. It is desirable to try to relax the process environment and various equipment conditions.

On the other hand, the mounting method of locally heating and melting a part of the solder has a limit to the fine mounting in which the mounting density is improved and the respective parts are in contact with each other as in the present case. Considering that it is becoming more and more detailed, it is necessary to wait for the proposal of a new heating method.

The present invention has been made in order to solve the above-mentioned drawbacks of the prior art, and an object thereof is to enable mounting of components in plural times by using a brazing material having the same temperature characteristic.

Another object of the present invention is to enable melting and joining at a temperature lower than the original melting point of the brazing material.

[0009]

In order to achieve the above object, the fusion bonding method according to the present invention is a fusion bonding method for joining materials to be joined via a molten brazing material, wherein the surface of the brazing material is Is fluorinated, and the brazing material is heated to a temperature lower than the melting point before fluorination and melted.

In the present invention thus constructed, the fluorine taken into the brazing material by the fluorination treatment moves and diffuses in the brazing material when heated to melt the brazing material. At this time, fluorine is easily bonded to other atoms,
It acts to break the bonds between the metals that make up the brazing material and destroys the crystal structure. Therefore, the brazing material melts at a temperature lower than the melting point before the fluorination treatment.

The melting temperature of the fluorinated brazing material depends on the amount of fluorine taken into the brazing material, and the higher the amount of fluorine, the lower the melting temperature. For example, when the brazing material is solder, by applying a fluorination treatment,
The melting temperature is 20 to 50 more easily than the melting point before fluorination.
It can be lowered by about 0 ° C. Therefore, by heating the fluorinated brazing material to a temperature lower than the melting point before the fluorination processing, the brazing material can be melted and the materials to be joined can be joined.

The mounting method according to the present invention is a mounting method in which a plurality of types of mounting components are divided into a plurality of times and bonded to a substrate via a brazing material, and the brazing material provided in the bonding portion is fluorinated. It is characterized in that the brazing material is heated to a temperature lower than the melting point before the fluorination treatment to be melted and joined.

In the present invention thus constituted, the brazing material subjected to the fluorination treatment melts at a temperature lower than the melting point before the fluorination treatment. Therefore, by heating to a temperature lower than the melting point before the fluorination treatment, Electronic components, which are mounted components, can be joined to the circuit board. Further, the fluorine taken into the brazing material by the fluorination treatment is released into the atmosphere as a gas when the brazing material is heated and melted. For this reason, the melting point of the brazing material melted during mounting returns to the value before the fluorination treatment when it solidifies. Therefore, when the mounting components are joined in plural times, by fluorinating the brazing material in the joint, only the brazing material in the fluorinated portion is melted at a lower temperature than the brazing material in other portions. It is possible to easily carry out mounting a plurality of times without melting the brazing material of the previously joined portion using the brazing material having the same temperature characteristics,
Even if the joining process is performed on the substrates a plurality of times, the joining failure of the previously joined components does not occur. Moreover, since the heating temperature at the time of joining can be lowered, the damage of the components due to the heat can be reduced and the joining conditions can be relaxed. Further, since the brazing material has an original melting point when solidified, even if the components are joined at a temperature lower than the heat resistance temperature required for the equipment (for example, 180 ° C.) by fluorination treatment, After joining, the heat resistant temperature can be sufficiently satisfied, and no problem occurs even when used under severe operating conditions.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of a fusion bonding method and a mounting method according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is an explanatory diagram of a mounting method according to an embodiment of the present invention. In FIG. 1, the fluorination processing unit 10
Is for fluorinating the terminal 14 which is a joint portion of the mounting component 12 such as a semiconductor chip, and is for exposing the mounting component 12 to hydrogen fluoride (HF) gas which is a reactive fluorine-based gas. The fluorination chamber 16 is provided. Then, in the fluorination treatment chamber 16, H through the pipes 18 and 20
The F gas supply unit 22 and the steam generation unit 24 are connected to each other so that a mixed gas of HF gas and steam is supplied. Further, the mounting component 12 is conveyed by a conveyer 26 such as a conveyor as shown by an arrow 28, and when passing through the lower portion of the fluorination treatment chamber 16, the mounting component 12 comes into contact with the mixed gas of HF gas and water vapor and reaches the terminal 14. Solder, which is a plated brazing material, is fluorinated. The plated solder is, for example, 90 wt% tin and 10 wt% lead and has a melting point of 215.
It is around ℃.

When the terminal 14 is exposed to a mixed gas of HF gas and water vapor, HF and H ₂ O are generated on the surface of the terminal 14,

[0017]

[Chemical Formula 1] Reaction of 2HF + H ₂ O → HF ₂ ⁻ + H ₃ O ⁺ occurs, and fluorine ions (HF ₂ ⁻ ) are generated at the terminal 14.
Reacts with the plated solder and fluoresces the surface of the solder.
That is, the surface of the solder is covered with a natural oxide film when placed in the air, like a general metal, and the substitution reaction between oxygen of the oxide film and F of HF ₂ ⁻ occurs to cause the surface to disappear. Is fluorinated. When the terminal 14 is fluorinated, the carrier 26 can be stopped and the lower portion of the fluorination chamber 16 can be closed by a shutter (not shown) to prevent the mixed gas from leaking to the outside.

The mounting component 12 having the terminals 14 fluorinated in this way is transported to the component mounting step and mounted on the circuit board 30 which is a substrate by a mounting robot (not shown). That is, the gold bumps 32 are provided at predetermined positions on the circuit board 30, and the terminals 14 of the mounting component 12 are arranged on the gold bumps 32. After that, the circuit board 30 on which the plurality of mounting components 12 are mounted is carried into the reflow furnace 34, which is a soldering step, and heated to a predetermined temperature under, for example, a nitrogen atmosphere.

Conventionally, when a solder having a melting point of about 215 ° C. is melted and soldered, it is about 40 ° C. higher than the melting point by 250 to 250 ° C.
It was general to heat to about 260 ° C. But,
In this embodiment, since the solder plated on the terminal 14 of the mounting component 12 is fluorinated, the fluorine taken into the solder is heated to cut the metal bond of the solder, and the temperature of 180 ° C. It becomes possible to melt at about this temperature. Therefore, the temperature of the terminal 14 is lower than the melting point before fluorination of the solder by the reflow furnace 34.
Since the solder is melted by heating to about 80 to 190 ° C., the terminal 14 can be bonded to the gold bump 32 of the circuit board 30.

That is, the soldering temperature can be significantly lowered as compared with the prior art, and the thermal damage received during the soldering of the mounting component 12 can be reduced, so that the reliability is improved and the soldering The thermal condition of is relaxed, various conditions such as environment and equipment can be relaxed, and the soldering can be facilitated. Moreover, the fluorinated solder is
When melted, fluorine becomes a gas and is released into the atmosphere, so that the melting point after solidification returns to the original temperature of about 215 ° C.
For this reason, when all the mounted components cannot be soldered at once and are soldered in plural times, even if the solders having the same temperature characteristics are used, the joint part (solder Part) by fluorination treatment,
The heating temperature for soldering can be set to 180 to 190 ° C., the solder in the previously soldered portion can be prevented from melting, no joint failure occurs, and solder management and soldering Work becomes easy.

In the above embodiment, the case where the brazing material is solder has been described, but the brazing material may be a tin-based alloy such as a tin-zinc alloy or a tin-silver alloy.

2 to 4 show another embodiment of the fluorination treatment method.

FIG. 2 shows a structure in which a stable fluorine-based gas is turned into an active gas by electric discharge and introduced into a fluorination treatment chamber in which mounting parts are arranged. The raw material gas supply unit 40, the water bubbling unit 42 and the electric discharge. And a unit 44. Stable fluorine-based gas such as CF ₄ and SF ₆ from the raw material gas supply unit 40 flows into the water bubbling unit 42 through the raw material gas pipe 46. The water bubbling unit 42 and the discharge unit 44 are connected by a supply pipe 48 so that CF ₄ containing water vapor in the water bubbling unit 42 can be supplied to the discharge unit 44.

The discharge unit 44 includes a pair of discharge electrodes 52 and 54 in the discharge chamber 50.
A mixed gas of CF ₄ and water vapor under atmospheric pressure passes between 54. Then, the discharge unit 44
Has a high frequency power source 56 connected to one discharge electrode 52 and the other discharge electrode 54 grounded.
By applying a high-frequency voltage between 54, it is possible to generate a gas discharge through the mixed gas. Further, the fluorination treatment chamber 60 in which the mounting component 12 is arranged is connected to the discharge unit 44 via a treatment gas pipe 58.

In the embodiment configured as described above, water vapor is added in the water bubbling unit 42 to CF ₄ which is the source gas from the source gas supply unit 40,
It is introduced into the discharge unit 44 at atmospheric pressure. The discharge unit 44 uses the high frequency power source 56 to discharge the discharge electrodes 52, 5
A high-frequency voltage of 13.56 MHz, for example, is applied between the _{four terminals,} and discharges through a mixed gas of CF ₄ and water vapor (H ₂ O) to cause CF ₄ and water vapor to react with each other to generate HF, F ₂ , CO
It produces a reactive fluorine-based gas such as F ₂ . The generated reactive fluorine-based gas is sent to the fluorination treatment chamber 60 together with the unreacted CF ₄ , and comes into contact with the mounting component 12 to fluorinate the solder plated on the terminal 14.

FIG. 3 shows an embodiment in which mounted components are arranged in the discharge region and fluorinated. The fluorination processing unit 62 according to this embodiment includes a high-frequency electrode 64 connected to the high-frequency power source 56 and a grounded ground electrode 66, and the mounting component 12 to be fluorinated is arranged on the ground electrode 66. ing. A discharge gas 68 containing at least a fluorine-based gas is supplied between the high-frequency electrode 64 and the ground electrode 66 in an atmospheric pressure state. As the discharge gas 68, for example, argon (Ar)
To which a few percent to a dozen percent of CF ₄ is added, oxygen added thereto, and further HF, F ₂ and COF _{2 described above.}
It may be a reactive fluorine-based gas or the like.

In this embodiment having such a configuration, the discharge gas 6 is provided between the high frequency electrode 64 and the ground electrode 66.
8 is introduced and a high frequency voltage is applied between the high frequency electrode 64 and the ground electrode 66 by the high frequency power source 56,
A gas discharge 70 is generated. As a result, the discharge gas 68
Is activated, and active fluorine such as a fluorine-based ion, a fluorine-based radical, or a single fluorine atom is generated. These active fluorines collide with the mounting component 12 arranged on the upper surface of the ground electrode 66 in the discharge region and fluorinate the terminals 14.

FIG. 4 shows another fluorination treatment method. Fluorination treatment section 72 according to this embodiment
The high frequency electrode 76 of the discharge unit 74 is the high frequency power source 5
It is connected to 6. A ground electrode 80 is attached to the high frequency electrode 76 via an insulator 78. The ground electrode 80 is provided on both sides of the high frequency electrode 76 or the high frequency electrode 76.
Is provided so as to surround the lower end of the high frequency electrode 76.

The ground electrode 80 has its lower end narrowed inward to form an irradiation port 82. Further, an inlet 92 is provided above the ground electrode 80 so that the discharge gas 68 can be introduced into the ground electrode 80. A discharge region 94 where a gas discharge is generated is formed between the lower end of the ground electrode 80 and the lower end of the high frequency electrode 76, and the active fluorine 96 generated in the discharge region 94 is blown downward from the irradiation port 82. I am able to do it. Further, below the irradiation port 82, a table 98 for arranging the mounting component 12 is arranged.

In this embodiment having such a configuration, a high-frequency voltage is applied between the high-frequency electrode 76 and the ground electrode 80 by the high-frequency power source 56, and the discharge gas 68 is introduced into the ground electrode 80 from the inlet 92. Then, gas discharge is generated in the discharge region 94 through the discharge gas 68. Then, the fluorine-based gas contained in the discharge gas 68 becomes active fluorine due to the gas discharge, and is irradiated to the mounting component 12 below through the irradiation port 82 to fluorinate the terminal 14.

In this embodiment, since the mounting component 12 is not arranged in the discharge area 94, collision of high energy electrons and ions can be avoided, and damage due to discharge can be prevented.

In addition to the above-mentioned method, the fluorination treatment is
For example, the mounting component 12 may be exposed to hydrofluoric acid vapor, or stable fluorine-based gas may be decomposed by ultraviolet rays or heat to generate active fluorine, which may be brought into contact with the mounting component 12.

[0033]

As described above, according to the present invention, by fluorinating the brazing material, it becomes possible to melt the brazing material at a temperature lower than the melting point before the fluorinating treatment. When melted and solidified, the fluorine blows off and the melting point returns to the original value, so soldering with the same temperature characteristics can be used in multiple mountings, and the temperature for bonding decreases and the heat of the mounted components decreases. Target damage can be reduced.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a mounting method according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of another fluorination treatment method according to the embodiment.

FIG. 3 is an explanatory diagram of still another fluorination treatment method according to the embodiment.

FIG. 4 is an explanatory diagram of still another fluorination treatment method according to the embodiment.

[Explanation of symbols]

10 Fluoride treatment part 12 Mounted parts 14 Joint (terminal) 16, 60 Fluorination chamber 22 HF gas supply unit 24 Steam generator 30 board (circuit board) 32 gold bumps 34 Reflow furnace 40 Raw material gas supply section 42 Water bubbling unit 44 Discharge unit 62, 72 Fluoride treatment part 68 Discharge gas 74 discharge unit

Claims (3)

[Claims] 1. A fusion bonding method for joining materials to be joined via a molten brazing material, wherein the surface of the brazing material is fluorinated, and the brazing material is heated to a temperature lower than the melting point before the fluorination treatment. A fusion bonding method characterized by melting by melting. 2. A mounting method in which a plurality of types of mounting components are divided into a plurality of times and bonded to a substrate via a brazing material, the brazing material provided in the bonding portion is fluorinated, and the brazing material is fluorinated. The method of mounting is characterized by heating to a temperature lower than the melting point and melting and joining. 3. The mounting method according to claim 2, wherein the fluoridation treatment fluorinates a joint portion of the mounting component.