JPH0749155B2 - Solder melting device with hot air - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solder melting apparatus using hot air, that is, a soldering apparatus for mounting a semiconductor integrated circuit on a printed circuit board or the like, and particularly a package for protecting the semiconductor integrated circuit. The present invention relates to a structure of a soldering device suitable for use when there is a possibility that the package may be broken by heating for a long time at high temperature because a material having relatively low heat resistance such as plastic is used. .

[Background of the Invention]

In recent years, the degree of integration of semiconductor integrated circuits (hereinafter referred to as LSI) has become higher and higher, and as shown in FIG. 3, dozens or hundreds or more of lead pins (hereinafter referred to as leads) 2 are provided on four sides of a plastic package 1. The flat-pack type package (hereinafter referred to as FPP) that it has is rapidly becoming popular, and the mutual spacing between these leads 2 is extremely fine, about 1 mm to 0.6 mm or less.
When I is mounted on a printed circuit board (hereinafter referred to as PCB), it is usually soldered by hand by handling an electric iron (reference; electronic technology; vo126No6 (1984)). In addition, because electronic equipment using such LSI with low heat resistance is designed for low cost, the PCB used together
However, since an inexpensive and low heat-resistant material is used, it is impossible to use the automatic soldering device using the reflow device described below. In addition, FIG. 4 shows the type having the lead 2 in only two of these FPPs.
The same was true for this type of FPP.

Conventionally, an LSI having the above-described shape is developed mainly for a large-scale computer for the purpose of extremely high-density planar mounting on a PCB, and since it requires high reliability, the LSI main body is housed. It was customary to use ceramics in the package (container), to use a material with extremely good heat resistance such as maintaining sufficient airtightness, and to use a high heat resistant resin for the PCB on which it is mounted. Soldering of these highly heat-resistant LSI and PCB is usually performed by using an automated soldering apparatus as shown in FIGS. 5 to 7, and such an apparatus is used. When soldering FPP and PCB with low heat resistance as described above, there were the following drawbacks, which hindered automation.

Fig. 5 shows the principle of the soldering furnace proposed to perform soldering in an inert atmosphere in order to prevent the soldering surface and the solder surface of the PCB from being oxidized during heating and preventing good soldering. FIG. In the figure, a heater 5 is installed in the furnace body 4, and antioxidant nitrogen gas (N ₂ ) is introduced into the furnace, and the temperature inside the furnace is normally maintained at about 300 ° C. . On the other hand, on the PCB 6, a predetermined amount of solder paste, which is a mixture of solder powder and flux, is printed at the position to be soldered in advance (not shown), and the LSI is mounted at the same position (not shown). , The inside of the furnace body 4 is fed by being fed into the furnace body 4 by the belt conveyor 3.
When the solder melts within 15 to 20 minutes and is taken out from the furnace body 4, the soldering is completed. This method is a simple device and has the advantage that a large amount of soldering processing can be performed,
It cannot be used at all for FPP, which has a heat-resistant temperature of about 200 ° C and has only heat resistance for several seconds.

FIG. 6 is an explanatory view of the principle of the apparatus proposed for soldering by utilizing the latent heat of vaporization of an inert high boiling point organic fluorine compound, and the high boiling point organic compound 10 and A heater 11 for heating the furnace is installed, and the furnace body 7 is filled with the high-boiling point vaporized compound saturated vapor 9 vaporized from here. In the furnace body 7 configured in this way, the shutter 8
Is opened, the PCB 6 on which the LSI is mounted (not shown) is fed by the belt conveyor 3, and then the shutter 8 is closed. At this time, since the PCB6 is at room temperature (20 to 30 ° C), the saturated steam 9 near its surface is cooled and the latent heat is released while condensing and liquefying on the surface of the PCB6, so that the PCB6 is rapidly heated. Is 210-220 ℃, the pre-printed solder is melted and soldered. After that, the PCB 6 is taken out by opening the shutter 8'while cooling. This method has the advantage that it can be soldered at a relatively low temperature.
The temperature is still too high for soldering, and it takes several minutes to dozens of hours, and the material cost is very high due to the use of a special fluorine compound, and the equipment is complicated to prevent the consumption of these materials. FPP is the most expensive
It cannot be used for soldering.

FIG. 7 shows an apparatus proposed for soldering using infrared rays. The PCB 6 is fed into the furnace by the belt conveyor 3 and preheated to about 150 ° C. by the preheating section heater 12, and then the soldering section heater 13 Then, the solder is soldered by rapidly heating it to about 200 ° C or more to melt the solder. This method can solder at a relatively high speed within a few minutes,
Moreover, there is an advantage that the energy consumption of the furnace is smaller than those of the above two, but on the other hand, because the infrared ray is used, the FPP using the black plastic is heated rapidly because the heat absorption efficiency is good, It is necessary to take special protection measures that make it difficult for FPP to absorb heat, because the package may crack or the internal LSI body may break due to a temperature difference of tens of degrees on the bottom surface. On the other hand, PCB is also exposed to infrared radiation at the same time, causing a temperature rise, but an inexpensive PCB, which has a lower heat resistance temperature than FPP, cannot be used due to burning or the like.

As described above, the reflow soldering method using a furnace has the following common drawbacks in addition to being extremely difficult to apply to an inexpensive FPP or an inexpensive PCB having a low heat resistance.

FIG. 8 is an explanatory view showing the state of the lead portion of the soldered LSI. As shown in FIG. 8 (a), the lead 2 of the LSI package 1 is positioned on the solder paste 14 printed on the PCB 6 by a certain amount. When they are aligned and placed and soldered through a reflow furnace, a melted solder flake 15 is formed around the lead 2 as shown in FIGS. 2B and 2C, and normal and strong soldering is performed. Be done. However, the lead 2 of the LSI package 1 does not always maintain the state as shown in the figure with high accuracy, and it is ± several degrees due to the accuracy at the time of press shaping, the deformation after shaping and handling during handling, or during transportation. In general, there is a variation in the horizontal degree of upward and downward, and FIG. 9 shows a case where only one of the many leads 2 is deformed downward. As shown in (a), only one of the leads 2 is in contact with the solder surface and the other is in a floating state. When such a solder is soldered in the reflow furnace, as shown in FIG. 2B, the solder 15 in the floating lead portion 2 is attached only to the tip, and it is as if the amount of solder is insufficient. And the reliability of the connection is deteriorated due to insufficient solder strength, and in an extreme case as shown in FIG. 7C, the adjacent leads 2 do not reach the solder surface and are not soldered. The problem arises. In order to solve such a problem, there is a case where the customer himself or herself shapes the lead 2 with high accuracy using a very expensive precision press machine, but a relatively small quantity of the customer is too expensive. Therefore, this cannot be done, and in many cases the amount of the solder paste 14 as shown in FIG. 10 is printed in a large amount to compensate for the defect as shown in FIG. However, such a method causes a problem that an excessive amount of solder is applied to a normal one, and a solder bridging occurs between adjacent leads 2 as shown in FIG. 10 (c) to electrically short-circuit. .

As described above, the soldering apparatus using a furnace has many problems and cannot be used for FPP soldering. For this reason, as a device for soldering LSI one by one, there is a method of locally blowing hot air to the LSI lead portion as shown in FIG. 11 to perform soldering. There are drawbacks. First, in the figure, the LSI package 1 is mounted by aligning the leads 2 on a PCB 6 on which solder paste (not shown) is printed, and sending it from a hot air generator (not shown) to it. The hot air 16 blown vertically is blown through the duct 17 having a width adapted to the length of the lead 2 of the LSI package 1 as shown by an arrow 16 'to melt the solder, and then the duct 17 is removed. Or LSI
Soldering is completed by removing the PCB 6 on which the package 1 is mounted. In such a device, while blowing hot air, excess hot air is discharged through the hollow portion 18 at the center of the duct as shown by the arrow 16 ″,
The duct 17 is divided into those discharged from the lower end of the duct 17 as shown by the arrow 16. The hot air discharged from the arrow 16 ″ discharged through the hollow portion 18 of the duct 17 is discharged while heating the upper surface of the LSI package 1. As a result, a high temperature difference (estimated value of 50 ° C. or more) is generated between the upper surface and the lower surface of the package 1, which causes warpage due to the difference in thermal expansion between the upper and lower surfaces. As described above in the explanation of FIG. There is a problem that the package 1 may be damaged or the internal LSI body may be destroyed.

[Object of the Invention]

An object of the present invention is to provide a solder melting apparatus using hot air suitable for soldering FPP and PCB having a low heat resistant temperature.

[Outline of Invention]

In order to achieve such an object, the present invention provides a control means for controlling an air flow rate, a conversion means for converting air into hot air, a pressure equalization of the hot air, and a flow of hot air from the pores to the soldered component. A hot-air blowing means for blowing constitutes a solder melting apparatus using warm air.

Conventionally, many methods of soldering using hot air have been used, but the following conditions are necessary when applied to FPP soldering.

(1) The surface temperature of FPP can be maintained below about 200 ℃.

(2) Keep the temperature difference between the upper and lower surfaces of FPP during soldering to be at least about 30 ° C or less.

(3) Do not give thermal damage to the other side PCB to be soldered.

(4) The solder connection failure as described in FIGS. 9 and 10 should not occur.

We have found the specifications for designing a soldering device using hot air that can satisfy these conditions.

Example of Invention

 Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic view showing an embodiment of a soldering device according to the present invention. In the figure, 19 is compressed air supplied from the outside at a pressure of about 2 Kg / cm ² , 20 is a flow control valve for compressed air 19, 21 is its flow meter, 22 is a solenoid valve for opening and closing air, and 23 is A quartz tube heater, 24 is a pressure equalizing tank that stores compressed air heated by the quartz tube heater 23 and can maintain a uniform air pressure, and 25 is a nozzle portion having a substantially flat tip at the bottom of the pressure equalizing tank 24, 26 is a fine hole that is provided at the tip of the nozzle portion 25 to blow out hot air to the outside, 27 is a crimping pin that is formed on the outer surface of the tip of the nozzle portion 25, and 28 is a quartz tube heater 23 and a pressure equalizing tank 24 that are vertically moved The reference numeral 29 designates an air cylinder that is driven in the direction, and 29 is a robot that drives the quartz tube heater 23, the pressure equalizing tank 24, and the air cylinder 28 in the XY direction and in the rotational direction.

FIG. 2 is a view showing the nozzle portion 25 described above, FIG. 2 (a) is a sectional view, and FIG. 2 (b) is a plan view seen from the bottom. Nozzle part 25
For example, for a four-way terminal type LSI, pores 26 are provided at portions where the four-direction terminal portions of the LSI are correctly opposed to the positions to be soldered, and the package 1 is provided in the central portion. A crimping pin 27 to be pressed down is formed on the PCB 6 so as to project.

In such a configuration, first, when compressed air 19 of about 2 kg / cm ² is supplied from the outside, the flow rate control valve 20 controls the air flow rate and the flow meter 21
The amount of air is checked by and is introduced into the quartz tube heater 23 through the air solenoid valve 22. The air introduced here becomes hot air, is supplied and stored in the pressure equalizing tank 24, is equalized in pressure, and then is blown downward from the pores 26 of the nozzle portion 25.
Here, as shown in FIG. 2 (b), the pores 26 are properly opposed to, for example, a four-way terminal type LSI at the positions where the terminals of the four directions of the LSI are to be soldered, and are therefore blown out. The hot air is blown out in a ribbon shape with the width of the pores 26 and is blown only to the positions of the leads 2 of the package 1 shown in FIG. At this time, since the LSI package 1 is pressed against the PCB 6 by the crimping pin 27 provided at the center of the nozzle portion 25 at the same time, some of the leads 2 of the package 1 are deformed as shown in FIG. Crimping pin 27
It is shaped horizontally by the pressing force of. After the solder is melted in this way, the hot air from the quartz tube heater 23 is stopped, and then cool air is blown from the cooling air nozzle 30 in the direction of arrow 31 to solidify the solder, and the entire soldering device is packaged in the LSI package 1. By removing it from above, the package 1 is securely soldered and fixed onto the surface of the PCB 6. If the number of LSIs to be attached is large, the entire device can be attached to the robot and sequentially moved while the above-described operation is performed, so that a large number of LSIs can be automatically soldered. .

The following conditions are required for soldering the leads 2 of the LSI package 1 by the soldering device described above. That is, (1) The distance d between the lower surface of the nozzle portion 25 and the upper surface of the PCB 6 to be soldered should be 5 mm or less.

(2) Select the width W of the pores 26 from which hot air blows out within the range of 0.5 to 3 mm according to the shape of the LSI lead 2 part.

(3) The temperature of the hot air blown from the pores 26 is 280 ℃ to 450 ℃
To choose between.

Etc. are required.

With this configuration, the following effects can be obtained. That is, (1) The hot air is blown out in a ribbon shape from the pores 26 of the nozzle portion 25, and since there is no hollow duct in the center as in the device shown in FIG. 11, the hot air blown out is the LSI package. After heating the lead 2 part of 1 and then spreading outward, there is no overheating of the plastic mold part of the LSI.
I and PCB with low heat resistance are not destroyed by heat.
According to the results of experiments conducted by the inventors, the temperature of this portion could be maintained at about 200 ° C. or lower.

(2) The hot air blows out in a ribbon shape and heats only the necessary parts of the leads 2 of the LSI package 1 to supply heat energy in a concentrated manner, so the time until the solder is melted and the soldering is completed The soldering can be completed in an extremely short time of 3 to 10 seconds, and since only local heating is required, the energy consumption is only 1 KW or less in one device, and when using a furnace. Compared with the energy consumption of several tens of KW, the soldering work can be performed extremely economically.

(3) Even if the leads 2 of the LSI package 1 are slightly deformed upward or downward, soldering is performed while pressing with the crimping pins 27, so that stable and reliable soldering can be performed with a fixed amount of solder, and Improves reliability.

In the above-mentioned embodiment, the same effect as described above can be obtained by using a ceramic substrate, a paper epoxy substrate, a glass epoxy substrate, a phenol resin substrate, a paper phenol substrate or the like as the PCB.

〔The invention's effect〕

As described above, according to the soldering device of the present invention,
FPP and PCB with low heat resistant temperature can be soldered reliably at low temperature with high reliability, low energy consumption,
It has an extremely excellent effect that it can be obtained at low cost.

[Brief description of drawings]

FIG. 1 is a schematic view showing an embodiment of a soldering device according to the present invention, FIGS. 2 (a) and 2 (b) are cross-sectional views of a nozzle portion, a plan view seen from the bottom, and FIG. 3 (a), (B) is a plan view and a sectional view showing a four-way terminal flat type plastic package LSI, and FIGS. 4 (a) and 4 (b) are a plan view, a sectional view and a plan view showing a two-way terminal flat type plastic package LSI. Fig. 5 is a schematic diagram showing a soldering device using an inert gas atmosphere furnace, Fig. 6 is a schematic diagram showing a soldering device using a high boiling point vapor substance as a heat medium, and Fig. 7 is an infrared soldering device. Schematic diagram shown in FIGS. 8 (a), (b), and (c)
10 (a), (b), and (c) are cross-sectional views showing the state of the soldered LSI lead portion, and FIG. 11 is a schematic view of a main portion for locally blowing hot air for soldering. 1 ... LSI package, 2 ... LSI lead pin (lead), 3 ... Belt conveyor, 4 ... Furnace body, 5 ... Heater, 6 ... Printed circuit board (PCB), 7 ... Steam furnace, 8,8 ′
...... Shutter, 9 ・ ・ ・ Steam, 10 …… High boiling organic compound, 11 …… Steam source heater, 12 …… Preheating part heater, 13 ・ ・ ・
… Solder part heater, 14 …… Solder paste, 15 …… Solder,
16 …… hot air, 16 ′, 16 ″, 16 …… hot air path, 17 …… hot air duct, 18 …… hollow duct, 19 …… air, 20 …… control valve, 21 …… flowmeter, 22… … Solenoid valve, 23…
… Quartz tube heater, 24 …… equalizing tank, 25 …… hot air nozzle, 26 …… pore, 27 …… crimp pin, 28 …… air cylinder, 29 …… robot, 30 …… cooling air nozzle , 31 ……
The path of cold wind.

 ─────────────────────────────────────────────────── --- Continuation of the front page (56) Reference JP-A-57-132395 (JP, A) JP-A-60-94371 (JP, A) JP-A-58-212861 (JP, A) JP-A-51- 101863 (JP, A) JP 59-212167 (JP, A)

Claims (1)

[Claims] 1. A warm air for melting the solder for connecting the respective lead wires of the semiconductor integrated circuit housed in a package having a plurality of lead wires around the periphery and the connecting portion of the printed circuit board with hot air. The solder melting apparatus according to claim 1, wherein the control means for controlling the flow rate of air, the converting means for converting the air into hot air, the hot air is pressure-equalized, and the connection portion between the lead wires and the printed circuit board. Hot air blowing means for blowing hot air to the soldering portion, which has pores having a shape corresponding to the shape of the soldering portion, and for pressing the package onto the printed circuit board at the tip of the hot air blowing means. A hot air soldering device comprising a crimping pin provided at the tip of the hot air blowing means and a cold air nozzle provided around the hot air blowing means for blowing cold air to the soldering portion. Solution apparatus.