JP2751979B2 - Vapor reflow soldering equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vapor reflow soldering apparatus, and more particularly to a so-called flat pack IC, in which electrode terminals are planarly extracted in four directions on a printed wiring board, and a surface of a resistor, a capacitor or the like. The present invention relates to a vapor reflow soldering apparatus suitable for high-density mounting for soldering chip parts.

[0002]

2. Description of the Related Art In recent years, high-density mounting of electronic components on printed wiring boards has been increasingly advanced. However, soldering work for bonding electronic components such as semiconductors and chip components to printed wiring boards is a final step in a line. For this reason, soldering technology has been regarded as the most important technology in the line. Recently, it is necessary to improve the uniformity of the temperature distribution in the furnace where soldering work is performed and to avoid harmful overheating of electronic components. There is a vapor reflow soldering apparatus for heating an object to be processed such as a printed wiring board. For example, as described in Japanese Patent Application Laid-Open No. 63-90361, this apparatus generates steam for soldering by passing a printed wiring board through saturated steam of a heat medium having a large specific gravity with respect to air as described above. This is a soldering device with a bath.

Conventional representative, will be described with reference to FIGS about vapor reflow soldering apparatus using a conveyor. Figure 3 is a longitudinal sectional view of a conventional vapor reflow soldering apparatus, FIG. 4, A-A sectional view taken along line of FIG. 3, FIG. 5, the object to be processed in the conventional soldering apparatus shown in FIG. 3 FIG. 3 is a diagram showing a temperature profile.

The apparatus shown in FIG. 3 includes a steam generation tank 4, a carry-in side transport path 5, a carry-out side transport path 6, a heater 7, a carry-in side cooler 8, a carry-out side cooler 9, a carry-in side exhaust port 10, and a carry-out side. Reflow section 1 comprising a side exhaust port 11, a preheating section 2 provided with a preheater 14, a cooling section 3 provided with a cooling fan 18, a conveyor 15, a drive sprocket 19, a carry-in sprocket 20, a carry-out sprocket 21 and the like. A drive train including
A heat medium recovery system including a recovery device 23, a hydroxyl remover 26, a circulation pump 27, etc., a temperature sensor 28, a temperature controller 29,
It comprises a control system such as a power controller 30 and a filtering system (not shown) for removing the flux mixed in the heat medium 12 in the steam generation tank 4. The steam generation tank 4 is separated from the carry-in side cooler 8 and the carry-out side cooler 9 by an open partition wall 38 at the lower part, and communicates with each other via a return passage 17 formed by the bottom plate 35 and the partition wall 38.

The operation of the conventional vapor reflow soldering apparatus configured as described above will be described. By starting the apparatus, power is supplied to the preheater 14 and the heater 7,
Since the latent heat of evaporation is about 1/25 of water, the heat medium 12 accumulated in the lower part of the steam generating tank 4 is heated by the heater 7 and immediately evaporated to generate saturated steam 13. As shown in FIG. 4 , the saturated steam 13 rises in the steam generating tank 4, and a part of the saturated steam 13 flows out of the lower steam outlet 33 through the lower steam outlet 33, and then flows out of the upper steam outlet 32 through the side wall passage 31. To ensure the necessary vapor level for reflow.

[0006] The saturated steam 13 that has heated the object 16 is condensed and liquefied and falls to the lower part of the steam generation tank 4.
Collect at the bottom of the. The remaining saturated steam 13 is cooled and liquefied by the carry-in side cooler 8 and the carry-out side cooler 9, and returns to the bottom of the steam generating tank 4 through the return passage 17. Slightly remaining steam is attached from the carry-in exhaust port 10 and the carry-out exhaust port 11, and the steam that has adhered to the processing object 16 and then separated is passed through the pipe 22 from the carry-out exhaust port 11, and is collected by the collection device 23. And the heat medium is recovered. The recovered heat medium is dehydroxylated by a dehydroxylator 26 and returned to the steam generation tank 4 by a circulation pump 27.

On the other hand, the workpiece 16 heated by the preheater 14 and carried from the preheating section 2 to the reflow section 1 by the conveyor 15 is heated by touching the saturated steam 13, and is heated in the steam generating tank 4. The solder is heated and melted by the latent heat of condensation and soldered. The workpiece 16 is gradually cooled into the unloading-side transport path 6, enters the cooling unit 3, is further cooled by the cooling fan 18, and is unloaded from the apparatus.
The height of the saturated steam 13 in the steam generation tank 4
Temperature sensor 28 and temperature controller 29 movably provided inside
Thus, the power to the heater 7 is controlled via the power controller 30 so that the temperature becomes a predetermined temperature, and is maintained at a predetermined value.

[0008]

In the above-described vapor reflow soldering apparatus, the following problems occur. The object to be processed generally has a configuration in which a wiring film and pads at its ends are provided on an insulating plate, solder paste is applied on the pads, and leads of the electronic component are located between the plurality of pads.

[0009] diagram of the temperature profile of the object shown in FIG. 5, the horizontal axis, the object to be treated is preheated section 2, the reflow section 1,
The time taken to convey the cooling unit 3 is shown, and the temperature is plotted on the vertical axis. The solid line indicates the temperature change of the pad portion of the object to be processed, and the broken line indicates the temperature change of the lead portion. When the object 16 is exposed to the saturated vapor 13 in the reflow section 1, the pad is covered with an insulating plate or a solder paste, while the lead has a large area in contact with the saturated vapor 13 because the lead has many exposed portions.
As shown in FIG. 5 , the lead reaches the melting point faster than the pad.

According to FIG. 5 , the reason why the temperature of the pad portion rises first in the preheating portion or the like is that the lower heater 14 in the preheating portion 2 is heated more strongly than the upper heater 14. This is because the saturated steam leaking from the steam generation tank 4 flows along the lower surface of the carry-in transfer path 5 and does not contact the workpiece 16 due to the specific gravity in the carry-in transfer path 5. When the lead reaches the melting point early, the solder starts to melt from the lead side. In this case, since the solder has a property of gathering on the previously melted side, the solder goes up the lead, and the solder between the pad and the lead is insufficient, so that good soldering may not be performed.

[0011] The present invention has the been made in order to solve the prior art problems, and an object can perform appropriate preheating depending on the component mounting condition of the object to be treated, the treated
Even if components with large heat capacity are provided on the lower surface of the object,
Make sure that the steam surface in the second steam generation chamber is
And the solder on the upper surface of the workpiece is
Since the solder can be melted from the soldering side, the solder in the soldering part does not move and the solderability does not decrease, and there is sufficient molten solder in the soldering part, and reliable soldering can be performed. An object of the present invention is to provide a vapor reflow soldering apparatus capable of improving the yield at the time of manufacturing a processed product.

[0012]

To achieve the above object, according to the solution to ## configuration <br/> formed of the vapor reflow soldering equipment according to the present invention, in the conveyor to the steam generating chamber that generates a saturated vapor of the heat medium In a vapor reflow soldering apparatus that conveys an object to be processed, makes saturated steam come into contact with the object to be processed, and heats and melts the solder on the object to perform soldering, a heater is provided upstream of the steam generation tank. A second steam generation chamber is provided for heating the stored heat medium to generate saturated steam.
Only, the heating saturated steam height generated from the steam generating chamber, to the extent that is in contact with the lower surface of the workpiece for conveying on a conveyor
A power adjusting means for adjusting the power of the heater is provided.

[0013]

The function of each of the above technical means is as follows. A second steam generation chamber is provided upstream of the steam generation tank ,
The power of the heater provided in the second steam generation chamber
Adjusted by the step, the upper limit of the height of the saturated steam in the second steam generation chamber is set as the pad position of the object to be processed, preferably the lower surface of the object to be processed, so that the pad is heated by heat conduction from below. The temperature rises before the lead.

Therefore, since the solder is melted from the pad side in the steam generating tank, the solder does not easily go up the leads, and the reliability of the soldering is greatly improved.
High yield can be obtained. In particular, when the time of heating from the lower surface is increased, the temperature rise of the object to be processed is averaged in the transport direction, and the melting of the solder occurs almost simultaneously on the entire surface of the object to be processed. Therefore, a phenomenon in which some of the leads of the electronic component are lifted without being soldered can be avoided.

[0015]

EXAMPLES Hereinafter, a description will be given of an embodiment of the present invention with reference to FIGS. FIG. 1 is a longitudinal sectional view of a vapor reflow soldering apparatus according to one embodiment of the present invention, and FIG. 2 is a diagram showing a temperature profile of an object to be processed in the soldering apparatus shown in FIG. In Figure 1, since Fig. 3 and those of the same symbols is prior art with equivalent portions is omitted general effects described. Embodiment shown in FIG. 1 is different from the prior art
Where the heat medium is guided from the heat medium recovery system and stored.
Another (second) heating by a heat heater to evaporate the heat medium
A) A steam generation chamber is provided upstream of the steam generation tank.
Then, the saturated steam height of the heat medium in the steam generation chamber is
Heat the heater so that it contacts the lower surface of the workpiece
It is providing the power adjustment means for adjusting the power of the motor.

The vapor reflow soldering apparatus shown in FIG. 1 comprises a steam generating tank 4, a carry-in side transfer path 5, a carry-out side transfer path 6, a heater 7, a carry-in side cooler 8, a carry-out side cooler 9,
The reflow section 1 including the carry-in side exhaust port 10, the carry-out side exhaust port 11, and the second steam generation chamber 43 provided upstream of the steam generation tank 4, the preheating section 2 including the preheating heater 14, and the cooling fan 18 The cooling unit 3 provided, a drive system including the conveyor 15, the drive sprocket 19, the carry-in sprocket 20, the carry-out sprocket 21, and the like, a control system such as a temperature sensor 28, a temperature controller 29, and a power controller 30; Device 2
3, a heating medium recovery system including a hydroxyl remover 26, a circulation pump 27, and the like.

The operation of the thus configured vapor reflow soldering apparatus of the present embodiment will be described. When the apparatus is started, power is supplied to the preheater 14 and the heater 7. The heat medium 12 stored in the lower part of the steam generation tank 4 is
Since the latent heat of evaporation is about 1/25 of water, the heater 7
, And immediately evaporates, generating saturated steam 13. The saturated steam 13 rises in the steam generating tank 4, and as shown in FIG. 4 , a part of the saturated steam 13 flows out from the lower steam discharge port 33 and the other flows out from the upper steam discharge port 32, and reflows the solder of the workpiece 16. To secure the necessary vapor level.

The saturated steam 13 that has heated the object 16 is condensed and liquefied and falls to the lower part of the steam generating tank 4, and the rest flows into the carry-in transport path 5 and the carry-out transport path 6. The saturated steam 13 flowing into the carry-in side transport path 5 through the second steam generation chamber 43 on the upstream side of the steam generation tank 4 is cooled by the carry-in side cooler 8 and flows into the carry-out side transport path 6. The saturated steam 13 is cooled and liquefied by the discharge side cooler 9, and returns to the bottom of the steam generating tank 4 through the return passage 17. The slightly remaining steam is supplied to the carry-in exhaust port 10 and the carry-out exhaust port 11.
Then, the gas flows into the collection device 23 through the pipe 22 and is collected. The recovered heat medium is dehydroxylated in a dehydrator 26 and is subjected to a second evaporation via a circulation pump 27 and a pipe 36.
Be stored is led to the gas onset Namashitsu 43.

A heater 42 is provided in the steam generation chamber 43.
When the heat medium is heated by the heater 42, the steam generating chamber
At 43, saturated steam 13 is generated. Steam generation chamber 43
Is set or controlled by a power controller (power control means) (not shown) connected to the heater 42 so that the height of the saturated vapor level is about the lower surface of the workpiece 16.

For example, when a component having a large heat capacity is provided on the lower surface of the workpiece 16 , a power controller (power
The power to the heater 42 is adjusted by the adjusting means
In the steam generation chamber 43 of the processing object 16
Since the saturated vapor height can be maintained, the heat capacity of the workpiece
Even if the amount is large, the solder on the upper surface can be melted from the pad side in the steam generation tank 4 .

The diagram of the temperature profile of the object to be processed shown in FIG. 2 corresponds to FIG. 5 described above, and the object to be processed is conveyed along the pre-heating unit 2, reflow unit 1, and cooling unit 3 on the horizontal axis. With the time taken, the temperature is plotted on the vertical axis, and the temperature change of the pad portion of the object to be processed is indicated by a solid line, and the temperature change of the lead portion is indicated by a broken line. As described above, since the object 16 is heated from the lower surface by the saturated steam generated in the second steam generation chamber 43 before being heated in the steam generation tank 4, it is shown in FIG. As described above, the temperature of the pad is kept higher than the temperature of the lead until the solder is melted, so that it is possible to prevent the lead from creeping up.

[0022]

As described above in detail, according to the present invention, it is possible to perform appropriate preheating in accordance with the state of component mounting of a workpiece, and a component having a large heat capacity is provided on the lower surface of the workpiece.
Even if provided, the steam level in the second steam generation chamber
It can be sufficiently maintained on the lower surface of the workpiece, and
The solder on the physical surface can be melted from the pad side
Because, without solderability decreases moving solder soldering portion, there is enough molten solder to the soldering portion, it is reliable soldering, the yield during manufacture of the object An improved vapor reflow soldering apparatus can be provided.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a vapor reflow soldering apparatus according to one embodiment of the present invention.

FIG. 2 is a diagram showing a temperature profile of an object to be processed in the soldering apparatus shown in FIG.

FIG. 3 is a longitudinal sectional view of a conventional vapor reflow soldering apparatus.

FIG. 4 is a sectional view taken along the line AA of FIG. 3 ;

5 is a graph showing the temperature profile of the workpiece in the conventional soldering apparatus shown in FIG.

[Explanation of symbols]

1 ... reflow chamber, 4 ... steam generation tank, 5 ... carry-in side conveyance path,
12: heating medium, 13: saturated steam, 15: conveyor, 16
... object to be treated, 23 ... recovery device, 27 ... circulation pump, 38
... partition wall, 42 ... heater, 43 ... steam generation chamber.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-64-44271 (JP, A) JP-A-1-150464 (JP, A) JP-A-62-9770 (JP, A) JP-A-61-64 92780 (JP, A) JP-A-62-101377 (JP, A) JP-A-63-53362 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) B23K 1/015 H05K 3 / 34

Claims (1)

(57) [Claims] An object to be processed is transported by a conveyor to a steam generating tank for generating saturated steam of a heat medium, and the object is brought into contact with the saturated steam to heat and melt the solder on the object to be soldered. in vapor reflow soldering apparatus to carry out, upstream of the steam generator vessel, equipped with a heater, set the second steam generation chamber to heat the heat medium stored to generate saturated steam only, from the steam generating chamber the saturated vapor height that occurs to an extent which is in contact with the lower surface of the workpiece for conveying on a conveyor
A vapor reflow soldering apparatus comprising a power adjusting means for adjusting the power of a heater .