JPS61169167A - Laser soldering method - Google Patents

Abstract

PURPOSE:To homogenize a soldering and to increase productivity by scanning at high speed a laser beam via optical system and by performing soldering with melting solders on plural joining parts. CONSTITUTION:A laser beam 2 is subjected to a spot irradiation on the contact 7' of the electronic component 6 of the above of a printed circuit board 5 with being converged by a curve mirrors 3 and 4. The curve mirrors 3 and 4 are made light-weighed, vibrating at the high speed of several scores Hz approx. and irradiating the laser beam 2 in numerous times in short time on plural soldering contacts 7'. With this method the part to be joined is heated nearly simultaneously and uniformly because of the laser beam being scanned at high speed on the plural parts to be joined. The problem of solder floating by individual joint method and defective contact, defective continuity, etc. are therefore prevented. The soldering is made uniform and made quickened, so the productivity is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a soldering method using laser light.

[Prior art] Conventionally, when mounting electronic components such as ICs, resistors, or capacitors on printed wiring boards, the leads of these electronic components are generally passed through through holes drilled in the wiring board to position them, and then solder is removed. A method of inflicting injury was adopted.

However, in recent years, electronic circuits have become smaller and more dense, and as a result, chip components such as flat ICs and transistor chips that do not use through holes as described above have come into use. To mount such an electronic component on a printed wiring board without using through holes, print the electronic component from above using a fixing jig, for example, so that the component does not shift from the specified position until the soldering is completed. It was necessary to hold the component by pressing it against a wiring board or the like. This has caused problems such as complication and inefficiency of the soldering process.

By the way, the laser soldering method, which has recently become widely used as one of the methods for soldering electronic components, is a non-contact process, so the external force that acts on the electronic components during soldering is extremely high. It has the feature of being small in size, making it suitable for soldering flat ICs with a narrow bonding pitch.

However, in the conventional laser soldering method, the contacts of the electronic component and the printed wiring board are soldered one by one. As it melts, the contacts in other unbonded parts float, causing phenomena such as the positional relationship with the contacts on the wiring board being noticeably shifted or floating compared to before the start of soldering. This has caused problems with solder defects such as poor contact at unbonded points and poor continuity.

[Problems to be Solved by the Invention] The present invention has been made in view of the above-mentioned points, and the purpose of the present invention is to solve the problems of the conventional example mentioned above, and
It is an object of the present invention to provide a new laser soldering method capable of uniformly soldering a large number of contacts.

[Means for Solving the Problems] The present invention achieves the above object by scanning a plurality of parts to be joined at high speed with a laser beam through an optical system, thereby reducing solder placed on the plurality of parts to be joined. This is a laser soldering method characterized by melting and soldering.

[Embodiments of the Invention] In the present invention, an individual electronic component having a plurality of contacts, such as the above-mentioned flat IC, or a single crystal such as this (even if there is only one contact point) is used. ) and for example the aforementioned pudding! - Soldering is performed on a plurality of parts to be joined, such as a wiring board, between these parts and a plurality of contacts of a joining member to be joined.

Of course, this is not limited to the above-mentioned electronic components and printed wiring boards; for example, any product that has multiple parts to be soldered, such as 1-Electronic distribution components and printed wiring boards, and the same dirt floor as the contacts in a wiring board. , it goes without saying that the method of the present invention is applicable.

Preferably, an appropriate amount of solder is placed in advance on such a plurality of parts to be joined. As the solder, for example, Pb-5n
Various materials such as Pb--based alloys and Pb--In based alloys are used in desired shapes such as paste or solid, and are appropriately selected depending on the material and shape of the parts to be joined. The solder placement method is not particularly limited, and for example, a desired amount of paste-like solder is applied to the bonded areas, a pre-coated layer of solder is provided on the bonded areas using a printing method, or solid solder is applied to the bonded areas. Various known methods can be applied, such as simply placing a desired amount of the compound on the site to be joined.

A laser beam is irradiated onto the part to be joined where the solder is placed as described above. Of course, it is also possible to perform laser beam irradiation without disposing the solder in advance and while continuously supplying solder to the parts to be joined during laser beam irradiation.

Examples of laser light include solid-state lasers using solid materials such as ruby, YAG (yttrium aluminum garnet), glass, or alexandrite, and gas lasers using gases such as C02 and He-Ne as oscillation media. Laser light is used. These laser beams are primarily used as a heat source for melting solder, and are preferably focused and used as spot beams, and are scanned at high speed so as to irradiate multiple joints to be soldered many times in a short period of time. Ru. The scanning speed IW is preferably set to a speed that allows each part to be welded to be irradiated about 20 to 50 times/second.

By periodically irradiating the laser beam many times, the plurality of parts to be joined are heated almost simultaneously, and the solder in the parts to be joined is melted almost simultaneously by the almost simultaneous heating,
Soldering is performed on the plurality of parts to be joined almost simultaneously.

Therefore, in the method of the present invention in which a plurality of parts to be joined are soldered almost simultaneously, the laser beam is sequentially irradiated to each part to be joined, and the soldering occurs because these parts are soldered separately. This eliminates the problems associated with conventional methods, such as floating of parts to be joined, such as electronic components, which occurs when multiple parts to be joined are soldered separately. This problem is solved, and stable soldering can be performed quickly.

In the present invention, as described above, a plurality of parts to be joined are periodically irradiated with laser light many times, but the irradiation conditions such as the output of the laser light used for such irradiation and the size of the irradiation spot etc. The undercoat is made of suitable strips depending on the material and size of the parts to be joined, which are made up of electronic components and contacts of printed wiring boards, etc., or the solder material, etc.
1- can be selected as appropriate. As an apparatus for implementing the present invention, for example, the one illustrated in FIG. 1 can be used.

As shown in FIG. 1, in this example, a laser beam 2 serving as a heat source for melting solder is focused by curved mirrors 3 and 4, and is focused on the contacts of an electronic component 6 placed on a printed wiring board 5. γ is irradiated as a spot light. curved mirror 3
and 4 are each equipped with a mechanism (not shown) for vibrating them at high speed in the X-axis and y-axis directions, and are designed to accurately irradiate a predetermined position on the printed wiring board 5 with the laser beam 2. The solder placed on the contact point γ is heated and melted in a controlled manner.

'' - The curved mirrors 3 and 4 irradiate the printed wiring board 5 with the laser beam 2 onto the plurality of contacts γ of the individual electronic components 6, but in order to uniformly heat the plurality of contacts, it is necessary to It is preferable to vibrate the curved mirrors 3 and 4 at a high speed of at least several tens of Hz, and irradiate the plurality of contacts γ with the laser beam 2 many times in a short period of time. Therefore, curved mirror 3
and 4 are preferably made of a material that is as oxidizable as possible to enable high-speed vibration, and that can sufficiently reflect the laser beam 2. Specific examples of such materials include, for example, aluminum or optical glass that has been subjected to a surface treatment (coating, etc.) that reflects well the laser wavelength used.

According to the device described in "-", it is possible to solder individual electronic components of the printed wiring board 5-1-, but for example, it is possible to solder individual electronic components of the printed wiring board 5-1-.
The irradiation area of the laser beam 2 due to the vibrations of 4 and 4 is set wider than that shown in FIG. 1, and the irradiation spot 7 of the laser beam 2 is controlled so that it can irradiate the contacts of multiple electronic components on the printed wiring board many times By doing so, it is of course possible in the present invention to solder a plurality of electronic components on a printed wiring board almost simultaneously.

For example, if an electronic component or printed wiring board located in the irradiation trajectory of the laser beam 2 has a part that needs to be avoided from being heated by the irradiation of the laser beam 2, the laser beam 2 from the laser oscillator 1 may be intermittently applied. Provide a control mechanism, such as a mechanical switch or an electro-optic switch, to enable the irradiation of the
It is also possible to perform soldering by irradiating the laser beam 2 only to necessary portions while avoiding irradiation of the laser beam 2 to unnecessary portions.

[Effects of the Invention] As explained above, according to the method of the present invention in which laser light is scanned at a high speed on a plurality of parts to be joined, it is possible to heat these parts to be joined almost simultaneously and almost uniformly. . Therefore, it is possible to prevent floating of parts to be joined such as electronic components due to solder flow, which has been a problem in the past, and it is possible to eliminate problems such as poor contact and poor conduction of parts to be joined that occur due to floating. . Furthermore, it is also possible to solder a plurality of members to be joined, such as electronic components, to a joining member such as a printed wiring board almost simultaneously and in a short time.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram illustrating an example of an apparatus for carrying out the method of the present invention. 1--Laser oscillator 2--Laser beam 3.4--Unicurved mirror 5-M-Printed wiring board 6--Electronic components? ---Irradiation spot γ-11 contact

Claims (1)

[Claims] (1) A laser soldering method characterized by melting and soldering solder placed on a plurality of parts to be joined by scanning a laser beam at a high speed through an optical system to the plurality of parts to be joined.