JPH02290672A - Vapor phase type soldering method - Google Patents

Abstract

PURPOSE:To prevent the temperature difference of each part of a work from increasing and to prevent defective soldering by controlling a heater with synchronizing width adjustment of a work carrying conveyor and controlling a vapor level of saturated vapor phase. CONSTITUTION:The saturated vapor phase is formed by heating an inert liquid 13 by the heater 14 in a vapor vessel 11 and the work W is carried in the saturated vapor phase shown by the vapor level 17a or 17b by the work carrying conveyor 21. Cream solder between a printed wiring board and parts mounted on the board is molten by latent heat of vaporization which the saturated vapor phase has and reflow soldering is carried out. In this case, the heater 14 is controlled in relation to the width adjustment of the work carrying conveyor 21 and the vapor level 17a or 17b of the saturated vapor phase is changed and controlled. By this method, the vapor level can be controlled to rise or fall according to size of the work and the temperature difference of each part of the work is not increased, hence defective soldering such as a part rise phenomenon can be prevented.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a vapor phase soldering method used mainly for soldering surface mount components to printed wiring boards. .

(Prior art) As shown in Japanese Patent Application Laid-Open No. 62-130770, a saturated vapor phase is formed by heating an inert liquid inside a steam tank using a heater, and the width can be adjusted according to the width of the workpiece. A vapor phase soldering method in which a workpiece is carried into a saturated vapor phase using a workpiece conveyor, and a printed wiring board (hereinafter simply referred to as a board) is reflow soldered as a workpiece using the latent heat of vaporization of this saturated vapor phase. There is.

Conventionally, in this type of vapor phase soldering method, after setting the vapor level of the saturated vapor phase during initial settings, the vapor level remains constant regardless of the size of the board as long as it is within the size of the board that can be transported. Performing reflow soldering.

(Problem to be Solved by the Invention) Conventionally, even if there is a large or small change in the substrate size, the vapor level has not been controlled to change. During the phase, the substrate temperature rises rapidly, and the temperature difference between each part of the substrate becomes large.
A problem has arisen in that parts standing phenomenon (Manhattan phenomenon) is likely to occur.

In such a vapor phase soldering method, the present invention provides:
The purpose is to apply an appropriate amount of flow heat to the workpiece according to the size of the workpiece, and to prevent soldering defects such as the phenomenon of parts standing up.

[Structure of the invention]

(Means for Solving the Problem) The present invention forms a saturated vapor phase inside a steam tank 11 by heating an inert liquid 13 with a heater 14, and forms a workpiece whose width can be adjusted according to the width dimension of the workpiece W. In a vapor phase soldering method in which a workpiece W is carried into a saturated vapor phase by a transfer conveyor 21 and the workpiece W is reflow soldered using the latent heat of vaporization of this saturated vapor phase, the method is related to the width adjustment of the workpiece transfer conveyor 21. The heater 14 is controlled by controlling the vapor level 171 or I? of the saturated vapor phase. This is a vapor phase soldering method that changes and controls b.

(Function) According to the present invention, when the size of the workpiece W is changed, the width of the workpiece transport conveyor 21 is also adjusted, so that the heater energization state related to the vapor level 17a or +7b is variably controlled in synchronization with this conveyor width adjustment. be done. A smooth temperature increase curve corresponding to the heat capacity of the workpiece W is obtained, and temperature differences between various parts of the workpiece do not become large.

(Example) Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 shows a first embodiment (step control type) of the present invention, in which an inert liquid (fluorine-based inert solvent)}3 is stored in a liquid storage part 12 of a steam tank 11 of a vapor phase soldering apparatus. This inert liquid 13 is supplied to the heater 1 provided at the bottom of the steam tank 11.
4, and a vapor level 171 or l? is evaporated between the workpiece loading port 15 and the workpiece loading port 16 of the steam tank 1l. A saturated vapor phase is formed, indicated by b. This saturated vapor phase is maintained within a certain range by the condensing action of the cooling coil 18 provided at the workpiece loading port 15 and the workpiece loading port 16, and leakage of the expensive fluorinated inert solvent to the outside is prevented. ing.

Furthermore, a workpiece conveyor 2l is provided for conveying the workpiece (printed wiring board) W from the workpiece inlet portion 15 through the saturated vapor phase to the workpiece outlet portion 16. Then, the workpiece W is carried into the saturated vapor phase indicated by the vapor level Its or Nb by the workpiece conveyor 21, and the latent heat of vaporization of this saturated vapor phase causes a gap between the printed wiring board and the parts mounted on the board. Melt some cream solder and perform reflow soldering.

The workpiece conveyor 2l has a fixed rail 22 on one side.
is provided, and a width adjusting rail 23 is provided on the other side so as to be movable in the distance direction while remaining parallel to the fixed rail 22.

Workpiece conveyance chains 24 and 25 are slidably provided along the fixed rail 22 and the width adjustment rail 23, respectively. The workpiece conveyance chains 24 on both sides,
Each of the pins 25 is endless, and a workpiece (printed wiring board) W is hung and placed on the pins 26 and transported. Therefore, when the width dimension of the workpiece W is changed, the width adjustment rail 23
is moved and adjusted.

A switch operating section 30 is integrally attached to the lower side of this width adjustment rail 23, and three limit switches 31, 32. 33 are facing each other. These limit switches 31, 32.
33 is connected to an electromagnetic contactor (magnetic contactor) 34. This electromagnetic contactor 34 includes each limit switch 31, 32. It has a coil that is excited when the switch 33 is turned on, and a contact that closes when the coil is excited to close an energizing circuit to the heater 14.

Then, when the width adjustment rail 23 is at the maximum workpiece corresponding position shown by the solid line in FIG. 1, all the limit switches 31, 32. 33 is in the on state, all heaters 14 are energized and the highest vapor level 17 is reached.
I is obtained.

Further, when the size of the workpiece W is changed to a smaller one and the width adjustment rail 23 is at the minimum workpiece corresponding position shown by the two-dot chain line in FIG. 1, the two limit switches 31.
32 is turned off, power supply to some of the corresponding heaters is stopped, resulting in the lowest vapor level 17b.

Next, FIG. 2 shows a second embodiment (continuous control type) of the present invention, in which the amount of rotation of the handle 42 of the width adjustment screw 41 for moving and adjusting the width adjustment rail 23 with respect to the fixed rail 22, and the 14 and is continuously synchronized and controlled.

That is, a rotary potentiometer 44 is provided to the width adjustment screw 41 via a rotation transmission mechanism 43, and this potentiometer 44 is connected to a power regulator 45.

This power regulator 45 variably adjusts the power supplied to the heater 14 in an analog manner. For example, when the workpiece W is small, the rotational operation of the width adjustment screw 4l that moves the width adjustment rail 23 to the left changes the resistance value for power setting of the potentiometer 44, and the power supplied to each heater 14 changes. The power regulator 45 is adjusted so that it becomes smaller.

Note that whether or not the vapor level is at a predetermined level is managed by temperature detection by a thermocouple (not shown) disposed inside the steam tank l1, and this thermocouple also controls the heater l4.

〔Effect of the invention〕

According to the present invention, since the heater is controlled in synchronization with the width adjustment of the work conveyor to control the vapor level of the saturated vapor phase, the vapor level is adjusted according to the size (width dimension) of the work to be reflow soldered. It is possible to control the rise or fall of the temperature, give the workpiece a smooth temperature rise curve according to its heat capacity, and since the temperature difference between each part of the workpiece does not become large, it is possible to prevent soldering defects such as parts standing up phenomenon.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a steam tank and an explanatory diagram of a heater control part showing a first embodiment of the vapor phase soldering method of the present invention, and FIG. 2 is a diagram of a work conveyor showing a second embodiment of the present invention. FIG. 3 is a cross-sectional view and an explanatory diagram of a heater control portion. W...Work, 11...Steam tank, l3...Inert liquid, l
4. Heater, 171. 17b21...Work conveyor. Fist Vaper Benore, λ1 Wazuku Beat %

Claims (1)

[Claims] (1) Form a saturated vapor phase inside the steam tank by heating an inert liquid with a heater, and transport the workpiece into the saturated vapor phase using a workpiece conveyor whose width can be adjusted according to the width of the workpiece. In a vapor phase soldering method in which workpieces are reflow soldered using the vaporization latent heat of the saturated vapor phase, a heater is controlled in conjunction with the width adjustment of the workpiece conveyor to change and control the vapor level of the saturated vapor phase. Characteristic vapor phase soldering method.