JPH05347373A - Molding structure for semiconductor element and soldering method therefor - Google Patents

Abstract

PURPOSE:To enable manufacturing of high reliability and high yield and to realize good use durability by forming solder of a small amount stably at a lead end part, by enabling sure solder connection and by realizing a constitution which enables ready assurance of conduction and strength. CONSTITUTION:In a conventional method, solder is applied to the side of a substrate; however, in this method, solder 3 is applied to the side of a lead 2 alone by a spin coater. In the case of mounting a semiconductor element 1, a fillet is formed below the lead by heating and pressurizing by a thermocompression tool, thereby realizing connection.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor encapsulation structure and method for improving the solderability of high density semiconductor element leads.

[0002]

2. Description of the Related Art With the miniaturization and high density of household electric appliances and AV equipment and the miniaturization and high precision and multi-functionalization of personal computers and workstations, a fine surface mounting technology (hereinafter referred to as SMT) for mounting parts including semiconductor elements is required. Has been. Generally, the method of mounting a semiconductor element for surface mounting (hereinafter referred to as QFP) is that when solder cream is applied to a circuit board, it is printed while drawing a pattern on a plate (hereinafter referred to as stencil) that acts as a mask, and the mounted components are positioned from above Then, it is put on it, and it is soldered by passing it through a hot air oven (hereinafter referred to as reflow). Further, solder cream having a particle size of 10 to 50 microns has been put into practical use for mounting a fine circuit board. The organic flux contained in the solder cream is composed of a mixture of a plurality of solvents and resins because of its fluidity, non-drying property, viscosity, ionic property, non-cleaning property and the like.

In addition to the above, N2 reflow furnace, infrared combined reflow furnace, vapor fuse method, etc. have been put to practical use as a reflow furnace for heating, melting and hardening.

[0004]

However, in the circuit board of the QFP mounting method manufactured by the conventional method as described above, a bridging defect is caused in the leads of the semiconductor element due to the variation of the applied solder cream amount and the variation of the applied heat amount.・ Floating defects and unsoldered defects are likely to occur, and there is also a drawback that the manufacturing yield is reduced.

Then, in order to ensure product quality, visual inspection is performed in a later step. In many cases, the shape of the fillet to be detected is indefinite, and the soldering shape of the lead tip that can be detected is large or small. However, it has the disadvantage of promoting lead time and overlooking defective products.

Further, in the circuit board field, so-called bridges, unsolders, and floating defects frequently occur in the current solder cream coating method, in response to the market demand for establishing a fine mounting technology for 0.4 mm pitch or less. Even when mounting minute resistors and capacitors, such as the 1005 chip, with solder cream, tombstones and unsoldered defects similarly occur, and drastic proposals are awaited. As a drawback common to the conventional methods, there are many solder mounting defects, an increase in inspection cost in a post process, and a decrease in productivity has been forced.

Further, when the lead pitch is a narrow pitch QFP of 0.4 mm pitch or less, the solder cream becomes a "kamaboko" shape when screen-printed, and it is difficult to accurately stack the leads on the solder cream, and the printed shape collapses. However, there are problems such as the formation of solder bridges between leads and variations in solder wettability with lands. In addition, when the stencil has a narrow pitch, defective coating due to solder cream dropout such as stickiness, scraping, and defective shape occurs, which hinders the miniaturization of components. Furthermore, the organic flux contained in the solder cream dries over time, which in turn makes it impossible to avoid the occurrence of electrical connection defects and insufficient joint strength due to viscosity changes, coating amount variations, and solder defects.

On the other hand, a method of applying solder to only the lead side by electrolytic plating by high-speed solder plating technology and thermocompressing the substrate has been proposed in the Denpa Shimbun (February 13, 1992 issue). However, in this proposal, the tin composition is likely to become rich on the metallic lead side as long as it is originally electroplating of solder, and if the composition change of the eutectic alloy is taken into consideration, the uniformity of the molten state cannot be ensured. It'll be easy. Moreover, if the solder composition at the tip of the lead becomes non-uniform, the connection characteristics will vary and the reliability will be questioned. Furthermore, since the electrolytic density becomes rich in the four corners of the square semiconductor device QFP,
It is considered that the plating thickness becomes uneven compared to other leads, and the solder quality during mounting is not stable.

Also, as described in the newspaper,
Since each lead is solder-plated, there are drawbacks such as the warp of the printed circuit board and the variation in the lead position of the QFP, which causes floating and positional deviation during mounting.
Since it is necessary to control the concentration of the plating solution, variations in composition and thickness during mass production are inevitable. Further, since the number of plating processing steps is increased, the cost is increased by making a jig for each QFP to be processed and setting plating conditions. Although it depends on the plating process, it will be higher than the current reflow solder printing method.

That is, if the solder cream can be uniformly supplied to each electrode portion of the mounted component with high positional accuracy, such a problem does not occur. Therefore, development of a fine soldering technique used for mounting a circuit board having a configuration capable of solving these drawbacks has been earnestly desired.

The present invention has been made in view of the above-mentioned problems, and a fixed amount of solder having a uniform composition is stably applied only to the tip of the lead so that the solder can be accurately positioned on the land of the circuit board. We provide a semiconductor element mounting structure and soldering method that can produce highly reliable and high-yield electronic components with fine surface mounting that are highly reliable and have a high yield by using a simple composition. The feature is that solder is applied only to the tips of the lead parts of the semiconductor element connected to the mounting board by a simple method without composition change, and the solder at the lead tips is melted and fixed to the board with a heating tool. Achieved with a semiconductor element mounting structure.

1. In the ultra-fine surface mounting method of QFP, a sufficient amount of solder necessary and sufficient for connection can be stably applied only to the tip of the lead by a simple method with no composition change, and it is durable. Stable semiconductor element structure with high reliability over time and its soldering method 2. Pre-treatment such as pre-flux is not required for fine pattern circuit, stable fillet shape can be manufactured accurately, and sampling process is extracted The semiconductor element structure that realizes high-density surface mounting that can be abolished and its soldering method 3, It is faithfully rotated with good yield without being affected by changes in the solder printing environment or changes in the plating composition over time. A semiconductor element structure that has a high connection strength with a small amount of waste and a soldering method therefor 4. Easy to use without expensive solder printing equipment or solder plating equipment It is another object of the present invention to provide a soldering method, a semiconductor device structure can be fixed mounting by the method.

[0013]

SUMMARY OF THE INVENTION A semiconductor element structure and a soldering method thereof according to the present invention that achieves the above-mentioned various objects are formed by dropping molten solder onto a rotating shaft of a spin coater and then rotating the leads of the rotating semiconductor element. A semiconductor element mounting structure and a soldering method thereof, characterized in that a soldering film is formed at a tip, and the solder of the lead portion is melted and fixed by a heating tool on a land of a mounting substrate to which flux is previously applied. In contrast to the conventional method of soldering on the board side,
The solder is applied only to the lead side by centrifugal force, and the solder is not supplied to the board side. When mounting, thermocompression bonding is used. When heated and pressed with a tool, a fillet is formed under the lead and can be connected.

[0014]

EXAMPLES Example 1 The present invention will be described in detail below based on examples.

Vacuum suction of QFP of 0.5 mm pitch 205 pin to a spin coater (1H-360 made by MIKASA) (7
0 cmHg) and set. As shown in FIG. 2, the lead tip shape 2 was used with a lead length of 2.5 mm with a cross-sectional shape of 0.20 mm width and 0.15 mm height. The conditions were set such that the rotation speed in the first stage was 400 RPM and the system was started up in 11 seconds, and the rotation speed in the second stage was 900 RPM and held for 8 seconds. Active rosin (RA) type solder was melted at 250 degrees Celsius, and 50 CC was dropped onto the lead portion during the first rotation. The centrifugal force due to the rotation of the spin coater 5 and the increase in viscosity due to the temperature decrease are combined with each other, and
Solder amount 3 from 12CC to 0.20CC is 99.8%
It was attached with the probability of. As shown in FIG. 1, the solder 3 was selectively concentrated at the tip of the lead, and the shape was reproduced well.

[0016] A solder printing machine (NP-04AN2, made by Hitachi Techno) was used in advance on a glass epoxy circuit board on which mounting wiring of 0.5 mm pitch was applied, and a stencil made of Ni additive was sandwiched with a pattern. While printing RA type solder cream. A chip mounter (CM85C-ME, manufactured by Kyushu Matsushita) was used to mount parts such as coronal parts {electrolytic capacitor / variable resistor} and chip parts {capacitor / resistor / filter}.

Flux was applied to the QFP land portion of the circuit board 18, and the semiconductor element 1 of the present invention was mounted by a chip mounter. As shown in FIG. 7, the lead tip 2 of the present invention was suppressed from above by the heating tool 17 of the heat pulse system to raise the energization temperature, the solder at the tip was melted, and the connection fillet 19 with the land was created. After disconnection cooling, the heating tool was raised and the bonding process was completed.

As a result, the fillet shape of the lead terminal of the semiconductor element of the present invention could surely realize electrical connection and mechanical strength as shown in FIG.

No occurrence of bridging defects due to excessive application of solder cream and heat history as shown in the conventional method of FIG. Even if there is unevenness in the handling of the semiconductor elements or the lead terminals are warped, the heating tool 17 of the heat pulse method suppresses the flapping of the leads from the top, so there is no unsoldered or floating defect and it is stable. It has become possible to manufacture uniform fillet shapes.

Since the amount of solder at the tip of each lead is uniform, a bridging defect (FIG. 9) occurs due to an excessive amount of solder popping out in the lateral direction, and an unsoldered defect due to uneven distribution of the solder amount among the leads (see FIG. The occurrence of 10) has disappeared.

On the contrary, it led to the improvement in the deviation of the amount of solder due to the mixture with the pitch of 0.65 mm. The reason is that the amount of solder basically depends on the surface area of the tips of the leads, so even if the lead spacing, that is, the pitch spacing is 0.65 mm,
Even if it becomes 0.2 mm, it is considered that the above-mentioned soldering action is effective and the same action works.

There are reflow soldering, solder cream printing, and molten solder dripping as solder precoating methods, and heating methods include reflow furnace, infrared furnace, hot air circulation, laser heating, light beam heating, heating tool, air heater, hot. There are plates and latent heat of vaporization. These heating methods may be used alone, or may be used in combination or repeatedly. Mounting / removing the QFP to / from the spin coater and mounting it on the board are intended for high speed / mass production, assuming the use of horizontal articulated robots or scalar robots.

As the solder composition which can be used, it is possible to add 0.1 to 50% of a metal component such as tin, bismuth, lead, tin, lead, silver, etc., which can take into account the characteristics of the low melting point solder. The flux composition used is pure rosin (R), weakly active rosin (RMA), active rosin (RA), synthetic resins such as phenolic compounds, fluorine-containing synthetic activators and low residues such as organic acids, organic salts and synthetic resins. It is also possible to use a component to which properties for use are added, or a substance to which a water-soluble inorganic acid / inorganic salt / organic acid / base / organic salt / organic halogen is added.

Specific resistance (Ω ・ cm) ・ Joint strength (g / lead) ・
Table 1 shows the results of examining the quality characteristics of the bridging defect occurrence rate (%) and the solder defect occurrence rate (%).

[0025]

[Table 1]

(Embodiment 2) 0.4 mm pitch 260-pin QFP is immersed in a molten solder bath for 0.5 seconds, and a soldering film is formed on the lead portion with a thickness of 10 to 50 μm as shown in FIG. did. Then, the QFP is vacuum sucked (70 cmHg) into a spin coater (1H-360 manufactured by MIKASA).
Let it set. Lead tip shape 2 has a cross-sectional shape of 0.15 mm width and 0.12 mm height and a lead length of 2.3 mm.
Used in. Rotation speed of the first stage is 350 RPM 1
Start up in 0 seconds and set the second stage rotation speed to 1100 RPM
The condition was set for 10 seconds. Tin for solder composition
We started heating the solder with 20% of the metal component that can take into account the characteristics of low melting point solder such as bismuth / lead and tin / lead / silver from the first stage of rotation with laser light. The centrifugal force due to the rotation of the spin coater 5 and the increase in viscosity due to the decrease in temperature are combined, so that the lead tip may have a thickness of 0.12 CC to 0.20 C.
The amount of solder up to C was attached with a probability of 99.8%. As shown in FIG. 1, the solder 3 was selectively concentrated at the tip of the lead, and the shape was reproduced well.

Using a solder printer (NP-04AN2, made by Hitachi Techno), a stencil made of Ni additive method is engraved on a glass epoxy circuit board having 0.5 mm pitch mounting wiring in advance. While printing RA type solder cream. A chip mounter (CM85C-ME, manufactured by Kyushu Matsushita) was used to mount parts such as coronal parts {electrolytic capacitor / variable resistor} and chip parts {capacitor / resistor / filter}.

Flux was applied to the QFP land portion of the circuit board, and the semiconductor element 1 of the present invention was mounted by a chip mounter. As shown in FIG. 4, the solder of the lead tip portion 2 of the present invention is selectively heated and melted by laser light from above to form a connection fillet, which is sunk by its own weight or jig pressure.
The semiconductor element was mounted on the substrate and the bonding process was completed.

As a result, the fillet shape of the lead terminal of the semiconductor element of the present invention could surely realize electrical connection and mechanical strength as shown in FIG.

No occurrence of bridging failure due to excessive application of solder cream and heat history as shown in the conventional method of FIG. Even if there is unevenness in the handling of the semiconductor elements or the lead terminals are warped, the heating tool 17 of the heat pulse method suppresses the flapping of the leads from the top, so there is no unsoldered or floating defect and it is stable. It has become possible to manufacture uniform fillet shapes.

Since the amount of solder at the tip of each lead is uniform, a bridging defect (FIG. 9) occurs due to an excessive amount of solder popping out in the lateral direction, and an unsoldered defect due to the uneven distribution of the solder amount among the leads (see FIG. The occurrence of 10) has disappeared.

On the contrary, it led to the improvement in the deviation of the amount of solder due to the mixture with the pitch of 0.65 mm. The reason is that the amount of solder basically depends on the surface area of the tips of the leads, so even if the lead spacing, that is, the pitch spacing is 0.65 mm,
Even if it becomes 0.2 mm, it is considered that the above-mentioned soldering action is effective and the same action works.

There are reflow soldering, solder cream printing, and molten solder dripping as solder precoating methods, and heating methods include reflow oven, infrared oven, hot air circulation, laser heating, light beam heating, heating tool, air heater, hot. There are plates and latent heat of vaporization. These heating methods may be used alone, or may be used in combination or repeatedly. Mounting / removing the QFP to / from the spin coater and mounting it on the board are intended for high speed / mass production, assuming the use of horizontal articulated robots or scalar robots.

Specific resistance (Ω ・ cm) ・ Joint strength (g / lead) ・
Table 1 shows the results of examining the quality characteristics of the bridging defect occurrence rate (%) and the solder defect occurrence rate (%).

[0035]

[Table 2]

(Embodiment 3) A 0.3 mm pitch 304-pin QFP is immersed in a molten solder bath for 0.5 seconds, and a soldering film is rotated on the lead portion by a thickness of 5 to 45 microns as shown in FIG. While forming the solder only on the tip. In other words, the above QFP is a spin coater (1H-360 made by MIKASA)
Vacuum suction (70 cmHg) and set. The lead tip shape 2 was used with a cross-sectional shape of 0.12 mm width and 0.10 mm height and a lead length of 2.0 mm. The conditions were set such that the rotation speed in the first stage was 260 RPM, the startup was started in 8 seconds, and the rotation speed in the second stage was 1500 RPM, which was maintained for 22 seconds. Weakly active rosin (RM
A) type solder was started to be heated at high frequency from the first stage of rotation. The centrifugal force due to the rotation of the spin coater 5 and the increase in viscosity due to the temperature decrease are combined, and
Solder amount from 0.12CC to 0.20CC is 99.8
Attached with a probability of%. As shown in FIG. 1, the solder 3 was selectively concentrated at the tip of the lead, and the shape was reproduced well.

Using a solder printing machine (NP-04AN2, made by Hitachi Techno), a stencil made of Ni additive method is engraved on a glass epoxy circuit board having mounting wiring of 0.3 mm pitch in advance. While printing RA type solder cream.

Flux was applied to the QFP land portion of the circuit board, and the semiconductor element 1 of the present invention was mounted by a chip mounter. The lead tip portion 2 of the present invention was heated from above with a nitrogen gas heated at a high temperature to raise the temperature, and the solder at the tip portion was melted to form a connection fillet 19 with a land. After stopping the blow and cooling, the bonding process was completed.

As a result, the fillet shape of the lead terminal of the semiconductor element of the present invention could surely realize electrical connection and mechanical strength as shown in FIG.

No occurrence of bridging failure due to excessive application of solder cream and heat history as shown in the conventional method of FIG.

Even if the semiconductor device is misaligned in the handling of the semiconductor element or the lead terminals are warped, the leads are suppressed by the self-alignment effect, so that there is no unsoldered or floating defect, and a stable and uniform fillet shape is obtained. It has become possible to manufacture.

Since the amount of solder at the tip of each lead is uniform, a bridging defect (FIG. 9) occurs due to an excessive amount of solder popping out in the lateral direction, and an unsoldered defect due to uneven distribution of the amount of solder among the leads (FIG. 9). The occurrence of 10) has disappeared.

On the contrary, it led to the improvement in the deviation of the amount of solder due to the mixture with the pitch of 0.65 mm. The reason is that the amount of solder basically depends on the surface area of the tips of the leads, so even if the lead spacing, that is, the pitch spacing is 0.65 mm,
Even if it becomes 0.2 mm, it is considered that the above-mentioned soldering action is effective and the same action works.

There are reflow soldering, solder cream printing, and molten solder dripping as solder precoating methods, and heating methods include reflow furnace, infrared furnace, hot air circulation, laser heating, light beam heating, heating tool, air heater, hot. There are plates and latent heat of vaporization. These heating methods may be used alone, or may be used in combination or repeatedly. Mounting / removing the QFP to / from the spin coater and mounting it on the board are intended for high speed / mass production, assuming the use of horizontal articulated robots or scalar robots.

Specific resistance (Ω ・ cm) ・ Joint strength (g / lead) ・
Table 1 shows the results of examining the quality characteristics of the bridging defect occurrence rate (%) and the solder defect occurrence rate (%).

[0046]

[Table 3]

(Conventional Example) Next, a conventional example will be described with reference to FIGS. Solder printer (NP-04AN) on glass epoxy circuit board with 0.5mm pitch mounting wiring.
2. SUS made by Hitachi Techno)
Solder cream (PS10R-4
50A-F28 manufactured by Harima Kasei Co., Ltd. was printed. Chip mounter (CM85C-ME, made by Kyushu Matsushita), semiconductor element {VSO / QFP / SOP / PQA / power transistor}, coronal component {electrolytic capacitor / variable resistor}, chip component {capacitor / resistor / filter}
It is equipped with parts such as. It was cured in a reflow furnace (RF-10A manufactured by Kyushu Matsushita) whose temperature can be controlled while drawing a temperature profile. The initial temperature of 180 degrees Celsius was set as the maximum temperature of 235 degrees Celsius, and curing was performed for 45 seconds in total.

As a result, in the fillet shape of the lead terminal of the conventional solder cream, the solder particles 20 of several tens of microns are uniformly dispersed in the paste 21 as shown in FIG.
When the mounted circuit board was put into the reflow furnace, the solder cream was melted and then heat-bonded. FIG. 5 shows a general cross-sectional view after solder bonding, but the rise of the molten solder to the lead terminals 14 can be seen.

As for the fillet shape of the lead terminal 14 of the semiconductor element to be manufactured, a bridging defect 11 is generated in the lead terminal 14 of the semiconductor element due to the variation in the amount of applied solder cream and the variation in the amount of heat applied as shown in FIG. It was easy to do. Therefore, delicate humidity control, viscosity control, squeegee application speed / pressure control, stencil back surface cleaning / durability, etc. are required, and post-correction such as bridge failure / floating failure is required, resulting in poor production yield. There is.

Specific resistance (Ω ・ cm) ・ Joint strength (g / lead) ・
Table 1 shows the results of examining the quality characteristics of the bridging defect occurrence rate (%) and the solder defect occurrence rate (%).

[0051]

[Table 4]

[0052]

As described above, the following can be enumerated as the effects of the present invention.

The necessary and sufficient amount of solder can be applied to the QFP lead portion of the fine gorge pitch without changing the composition, and the positioning accuracy of the parts can be significantly improved over the mechanical accuracy of the chip mounter. ..

According to the solder viscosity characteristic of the spin coater, without using an expensive plating device, without being involved in delicate production condition setting, and without preparing a dedicated jig for each size of QFP. High-quality soldering can be realized easily and inexpensively under rotating conditions, and the quality and cost effects can be realized with less solder consumption than the conventional batch reflow printing method.

Since no solder paste is used, it becomes a CFC-less / global environment conservation activity,
Excellent in safety and health.

With the reflow furnace sensitive to the nonuniform N2 atmosphere control, the UV exposure / curing process can be simplified and downsized, and the productivity, the quality can be stabilized, and the yield can be improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional configuration diagram showing a solder shape of a semiconductor element according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional configuration diagram showing a soldering process of a lead tip according to the first embodiment of the present invention.

FIG. 3 is a sectional configuration diagram showing a solder shape of a semiconductor element of Example 2 of the present invention.

FIG. 4 is a perspective view showing a laser heating process of a lead tip according to a second embodiment of the present invention.

FIG. 5 is a cross-sectional configuration diagram showing a fillet shape of the present invention.

FIG. 6 is a perspective view showing a high-frequency heating process of a lead tip according to a third embodiment of the present invention.

FIG. 7 is a cross-sectional configuration diagram showing a joining process of the heating tool at the tip of the lead according to the first embodiment of the present invention.

FIG. 8 is a perspective view showing a semiconductor element to be positioned and a printed shape after applying a solder cream in a conventional example.

FIG. 9 is a perspective view of a bridging defect of a conventional example.

FIG. 10 is a cross-sectional configuration diagram showing a fillet shape of a non-soldered defect of a conventional example.

FIG. 11 is a cross-sectional configuration diagram showing a print shape after applying a solder cream in a conventional example.

[Explanation of symbols]

 1 Semiconductor Element of the Present Invention 2 Lead Terminal 3 Solder of Lead Terminal of the Present Invention 4 Solder Solder 5 Spin Coater 6 Scattered Solder 7 Solder of Lead Terminal after Flow of the Present Invention 8 Laser Heating Element 9 Conventional Example Semiconductor element 10 Solder paste after printing of Conventional Example 3 11 Solder shape with bridging failure 12 Land 13 Unsoldered failure 14 Lead of conventional example 15 Good fillet shape 16 High frequency heating element 17 Heating tool shape 18 Lead of conventional example 19 Connection fillet 20 solder particles 21 flux

Claims (11)

[Claims] 1. A semiconductor element mounting structure in which solder is applied only to the tips of the leads of a semiconductor element to be connected to a mounting board, and is crimped with a heating tool to be fixed to the board. A semiconductor rotating on a rotation axis of a spin coater. Molten solder is dropped onto the element, a solder film is formed only on the tip of the lead, and then a connection terminal on the mounting board on which flux has been applied in advance.
A semiconductor element mounting structure and a soldering method thereof, characterized in that the soldered lead tips are fixed under pressure (hereinafter referred to as lands) with a heating tool to melt the solder and mount the semiconductor element on a substrate. 2. A solder layer in a molten state (hereinafter referred to as a flow) instead of a method of dropping molten solder onto a semiconductor element which is rotating on a rotation axis of a spin coater and forming a solder film only on the tip of the lead. 2. The semiconductor element mounting structure and the soldering method thereof according to claim 1, wherein the semiconductor element is dipped in and the soldering film is formed on the lead portion. 3. A semiconductor element is spin-coated in a solder phase atmosphere in place of a method in which molten solder is dropped onto a semiconductor element rotating on a rotation axis of the spin coater and a solder film is formed only on the lead tips. The semiconductor element mounting structure and the soldering method thereof according to claim 1, wherein the lead part is rotated to form a soldering film. 4. Instead of a method of dropping molten solder onto a semiconductor element that is rotating on the rotation axis of a spin coater and forming a solder film only on the tip of the lead, solder plating and solder cream are applied to the lead portion of the semiconductor element. 2. A soldering film is formed on the lead portion by heating and melting while rotating with a spin coater.
Described semiconductor device mounting structure and its soldering method. 5. Instead of the method of press-fixing the soldered lead tips with a heating tool and melting the solder to fix the semiconductor element to the substrate, the lead tips are heated and irradiated with a light beam to remove the solder. 2. The semiconductor element mounting structure according to claim 1, wherein the semiconductor element is mounted on the substrate by melting and sinking it by its own weight or jig pressure. 6. Instead of a method of press-fixing the soldered lead end portion with a heating tool and melting the solder to fix a semiconductor element to a substrate, the solder of the lead portion is selectively irradiated with laser light. 2. The semiconductor element mounting structure and the soldering method thereof according to claim 1, wherein the semiconductor element is mounted on the substrate by heating, melting, and sinking under the weight or jig pressure. 7. The solder of the lead portion is selected by radiant heat of infrared rays instead of the method of press-fixing the soldered lead end portion with a heating tool and melting the solder to fix the semiconductor element to the substrate. 2. A semiconductor element mounting structure and a soldering method thereof according to claim 1, wherein the semiconductor element is mounted on the substrate by being heated and melted and sunk by self-weight or jig pressure. 8. The solder of the lead portion is selected by hot air or high temperature nitrogen instead of the method of fixing the soldered lead end portion under pressure with a heating tool and melting the solder to fix the semiconductor element to the substrate. 2. A semiconductor element mounting structure and a soldering method thereof according to claim 1, wherein the semiconductor element is mounted on the substrate by being heated and melted and sunk by self-weight or jig pressure. 9. The solder composition used is characterized by containing 0.1% to 50% of a metal component such as tin, bismuth, lead, tin, lead, silver, etc., which can take into account the characteristics of low melting point solder. 1. A semiconductor element mounting structure according to 1, and a soldering method thereof. 10. The flux composition used is pure rosin (R) / weakly active rosin (RMA) / active rosin (RA).
Claims characterized by adding 0.1% to 100% of a component capable of adding characteristics for low residue such as synthetic resin such as phenol and phenol, synthetic activator containing fluorine, organic acid, organic salt, synthetic resin, etc. Item 1. A semiconductor element mounting structure according to item 1 and a soldering method thereof. 11. The semiconductor element mounting structure and its soldering according to claim 1, wherein a water-soluble inorganic acid / inorganic salt / organic acid / base / organic salt / organic halogen is added to the flux composition used. Method.