JPH02306693A - Mounting and soldering method for electronic component - Google Patents

Abstract

PURPOSE:To effectively and easily solder an electronic component to be placed and mounted on a circuit board by continuously performing in two stages a laser beam radiating operation by preheating and soldering as required at a part to be soldered. CONSTITUTION:A laser beam radiating travel to a part 4 to be soldered is continuously performed in two stages, the part 4 to be soldered is preheated by a traveling laser beam radiating 2a, and sequentially soldered as required by a following laser beam radiating 2b. Thus, the difference between a preheating temperature and a soldering temperature is reduced. ln this manner, generation of a solder ball can be entirely suppressed to effectively perform a predetermined soldering, and a preliminary heating is selectively and locally performed. Accordingly, solder drop of other soldering part, warpage of a circuit substrate 3, a thermal defect of other circuit substrate 3 can be eliminated.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a method for mounting and soldering electronic components, and particularly to a method for mounting and soldering electronic components that uses a laser beam as a heat source. relates to improvements in the method.

(Prior Art) High-density mounting circuit devices (hybrid circuit devices), in which electronic components such as pub-cage type IC elements are mounted and mounted on a predetermined area of a wiring board, are being widely used in various electronic devices. . By the way, in the configuration of this type of high-density packaging circuit device, it is known that a laser beam is used as a heat source for soldering, and leads of electronic components to be mounted are soldered to pads of a wiring board or the like. In other words, the required wiring board is first prepared, and the number of wiring boards is set on a mounting table equipped with a built-in preheater that generates heat of about 180 degrees Celsius, while electronic components are placed on the surface of a predetermined area of the wiring board. Further, the preheating heater is operated to preheat the wiring board to about 80 to 100°C, and a laser beam is irradiated to lead terminals derived from electronic components to be soldered to predetermined pads. A method is used to solder them to each other.

(Problems to be Solved by the Invention) However, the conventional method of soldering mounted electronic components by laser beam irradiation has the following disadvantages.

That is, since the preheating for soldering is applied to the entire wiring board, there is a risk that the solder in the soldered portion may melt or warp may occur on the wiring board. Therefore, there is a limit to the preheating temperature, and when soldering is performed by laser beam irradiation, the relationship between the temperature of the part to be soldered and the laser beam irradiation time is as shown in FIG. 4, for example. In other words, since the soldering temperature increases rapidly from the preheating temperature, solder balls and other
1 tends to lead to defects. These problems greatly affect the reliability of the connection when a large number of lead terminals (lead pins) are to be soldered or when the pitch of the lead terminals (lead pins) is narrow.

[Structure of the Invention] (Means for Solving the Problems) The present invention has been made in response to the above-mentioned circumstances, and includes disposing electronic components on a predetermined area surface of a wiring board, and connecting leads derived from the electronic components. In a method of soldering terminals to predetermined pads on a wiring board by laser beam irradiation, the laser beam irradiation operation is performed in two consecutive steps: preheating the part to be soldered and performing the required soldering. It is characterized by

In other words, the laser beam is divided into multiple parts and these are scanned continuously, the preceding laser beam irradiation preheats the parts to be soldered, and the subsequent laser beam irradiation performs the required soldering of the parts to be soldered. This is a basic outline.

(Function) According to the means of the present invention, the part to be soldered is irradiated and scanned with a laser beam in two stages, and the part to be soldered is preheated by the preceding laser beam irradiation. Further, the required soldering is performed sequentially by subsequent laser beam irradiation.

Therefore, the difference between the preheating temperature and the soldering temperature is reduced, and the generation of solder balls is completely suppressed, so that the desired soldering can be performed reliably. Furthermore, since the preheating is selective or local, there is no fear that other soldering may cause solder drop in parts, warping of the wiring board, or other thermal problems to the wiring board.

(Example) The present invention will be described in detail below with reference to FIGS. 1 to 3. First, the mounting soldering system is equipped with a wiring board mounting table 1 consisting of an X-Y table, and a laser beam irradiation scanning system 2 that is paired with a laser beam irradiation system 2a for preheating and a laser beam irradiation system 2b for soldering. Prepare the equipment. Here, the preheating laser beam irradiation system 2a and the soldering laser beam irradiation system 2b are configured to scan in a predetermined direction in synchronization. The above-mentioned mounting soldering is performed by placing a required wiring board, such as a ceramic wiring board 3, on a wiring board mounting table 1 of the device, and attaching a required electronic component, such as a QFP type I type wire, to a predetermined area surface of the ceramic wiring board 3. Position and arrange 4 C elements. After that, the laser beam irradiation scanning system 2
drive and scan.

In other words, a laser oscillation source is driven to generate a laser beam, and this laser beam is sent to the preheating laser beam irradiation system 2.
Q and soldering are performed via the laser beam irradiation system 2b.
The preheating laser beam irradiation system 2a scans in a predetermined direction over the lead terminal 4a rows led out from the FP type I type nest C element 4. FIG. 1 shows that a preheating laser beam is applied to a row of lead terminals 4a led out from a QFP type I type nest C element 4 through the preheating laser beam irradiation system 2a and the soldering laser beam irradiation system 2b. FIG. 2 is a side view schematically showing a state in which the irradiation system 2a is scanning in a predetermined direction in advance, and FIG. 2 is a plan view schematically showing the scanning state. In this way, the preheating laser beam irradiation system 2a scans the lead terminals 4a row led out from the QFP type I type nest C element 4, and the soldering target is the lead terminal 4a row. After selectively preheating the required portion 2a' to a temperature close to the eutectic point of solder, for example, the soldering laser beam irradiation system 2b is applied to the preheated QFP type I type nest C element 4-d. Terminal 4a row upper 2b'
By scanning in a predetermined direction, the pads 3a on the surface of the wiring board 3 are soldered and electrically connected to each other.

Therefore, in the mounting soldering method according to the present invention, preheating of the part to be soldered is selectively performed by laser beam irradiation, so that the part to be soldered is the third part.
As schematically shown in the figure, the temperature is easily raised to a temperature close to that required for soldering at the preheating stage. Therefore, during subsequent soldering, the required soldering can be easily achieved without generating solder balls or the like during irradiation with the laser beam.

Although the above example shows how to solder a QFP IC device, it is also possible to solder other flat package devices such as an SOP IC device, as well as electronic components with a small number of lead terminals such as resistors. may also be applied.

In addition, the energy irradiated via the preheating laser beam irradiation system 2a and the soldering laser beam irradiation system 2b may be selected and adjusted as appropriate depending on the condition of the part to be soldered, for example, the material and diameter of the lead terminal. Of course.

[Effects of the Invention] According to the present invention, electronic components mounted and mounted on a wiring board can be accurately and easily soldered as described above.

In other words, since the parts to be soldered are preheated to a relatively high temperature by laser beam irradiation, the generation of solder balls is sometimes completely suppressed during subsequent soldering by laser beam irradiation.

Therefore, highly reliable soldering can be achieved without causing any defects. Moreover, since the preheating is performed selectively or locally on the parts to be soldered, it is possible to avoid adverse thermal effects on the wiring board. Furthermore, it becomes possible to solder a double-sided component-mounted wiring board by irradiating each side with a laser beam, which was difficult in the conventional method due to preheating.

[Brief explanation of the drawing]

1 and 2 schematically show embodiments of the electronic component mounting and soldering method according to the present invention, respectively. FIG. 1 is a side view, FIG. 2 is a plan view, and FIG. 3 is a Figure 4 is a curve diagram schematically showing the temperature state of the part to be soldered in the mounting soldering method for electronic components according to the present invention. FIG. 3 is a curve diagram schematically showing temperature states. 1... Mounting table 2... Laser beam scanning system 2a... Preheating laser beam irradiation system 2b.
...Laser beam irradiation system 3 for soldering...
・Wiring board 3a...Pad 4...Electronic component 4a...Lead terminal

Claims (1)

[Scope of Claims] A method of arranging electronic components on a predetermined area surface of a wiring board, and soldering lead terminals derived from the electronic components to predetermined pads on the wiring board by laser beam irradiation, comprising: A method for mounting and soldering electronic components, characterized in that beam irradiation scanning is performed in two consecutive stages: preheating of a soldered part and required soldering.