JPS58139498A - Printed circuit board flux - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention aims to improve work efficiency and solder joints in the soldering process when electronic components are attached to printed boards (including board-shaped and flexible ones) using an automatic soldering device. For printed boards with electronic components inserted and mounted for the purpose of improving
The present invention relates to a method of coating and forming soldering flux, and more specifically, relates to a modification of a method of forming soldering flux using a transfer method.

The typical conventional method of forming soldering flux is to use rosin as the main ingredient, water, and alcohol.

Printed boards with pre-flux applied to protect circuit surfaces during the printed board manufacturing process using liquid flux dissolved in solvents such as esters, ketones, aromatic hydrocarbons, etc., and then mounted with electronic components, etc. There are several methods: brushing, applying with a roller, dipping into a flux solution, bubbling liquid flux and immersing it in the foamed flux, and atomizing the flux before applying. Since it is extremely easy to apply to printed boards, it is suitable for labor saving in mass production and is widely used.

However, on the other hand, with these coating methods, (1) it is difficult to fill the coating amount into a tube, and uniformity is lacking. ■Since the application is in a liquid state containing a large amount of solvent, it is applied from the insertion hole of the lead to the back side, that is, the part where the scissors are attached.4. It may penetrate into the internal parts along the lead wires of the removed parts, impairing the functionality of the electronic parts. ■For soldering, dry organic solvents such as alcohol, aromatic, etc. after applying flux.
It has many problems, including the risk of ignition.

In order to overcome these shortcomings, the 7 lux coating method using the transfer method disclosed in Japanese Patent Application No. 55-147 II 53 filed by the present applicant et al. is a futsututas transfer method in which soldering flux is coated on one side of the support film and dried. Paper is adhesively bonded to the printed board using a transfer machine such as a four-wheel type or flat pressure type, and after cooling, the support film is peeled off to form a black layer on the printed board, and electronic components are inserted. The liquid flux is directly applied to the soldering process.
There was a problem with the cloth forming method. Uniform application amount,
This was an excellent method for solving various problems such as oozing of solvents to the back side of printed boards and the risk of fire. However, in the case of flux formation using this transfer method, since the flux is formed before electronic components are mounted, there is no possibility that 7lux will adhere to the Y-D line of electronic components inserted later.
This connection between the lead wire and the metal is made by attaching the flux that has fallen from the printed board to the lead wire in a soldering bath, activating the metal surface of the lead wire and making soldering possible.However, the amount of flux that adheres to the pigeonhole lead wire is There is a possibility that the joint state between the lead wire and the solder varies due to the looseness and non-uniform wetting, resulting in joint defects and poor soldering such as bridges.

Among the conventional soldering flux forming methods as described above, the present invention uses a liquid 7x that does not contain a solvent to be applied to electronic components in the pre-process 1, which enters the soldering bath during soldering in the 4IK transfer method 2. Soldering provides a flux forming method that enables excellent bonding with fewer defects by forming the flux only on the lead portions.

In other words, after the soldering flux is formed on the printed board using the transfer method, electronic components are inserted and soldered using the conventional transfer method. However, in the present invention, in order to improve the wetting of the solder on the lead part, heating is performed → before soldering, a liquid flux consisting of an organic acid that is liquid at room temperature, and an organic acid that becomes liquid when heated are used. By immersing the lead wires of electronic components and other components in a solvent-free 7-lux solution consisting of acid and lysine and forming the coating, reliable soldering is possible while retaining the advantages of flux formation using the transfer method. Specifically, 7 lux for soldering is applied and formed on a smooth support film, this flux is brought into close contact with a wiring board for soldering, and transferred by heating and pressure. After inserting the electronic component glue into this wiring board from the back side, organic acids or rosin resins such as milk soap, oleic acid, pallic acid, or stearic acid, which become liquid when heated at room temperature or below 100°C. This is a method for forming a 7-lux, which is characterized in that a liquid soldering flux consisting of the following is dip-coated onto the lead wire portion of an electronic component.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The method for forming soldering flux according to the present invention will be described below with reference to Examples and drawings.

Figure 1 shows a method for forming flux on a printed board using the transfer method. 1) A base made of paper - a material such as phenol resin, glass - epoxy resin, and an electrode made of metal such as steel or silver. (2) A supporting film (4) made of a plastic film such as polyethylene terephthalate film, boria film, polyethylene, polypropylene-based polyolefin film, self-unfilm, etc. is coated onto a printed board made of (2) and soldered. Transfer the soldering flux transfer foil consisting of the soldering flux (3) by applying heat and pressure using a pressure-type or roll-type transfer machine, and after cooling, peel off the support film (4) and print the soldering flux (3). Transfer and form onto the board.

The soldering flux (3) is mainly composed of gum rosin, kutudrozin, tall oil rosin, etc., and various additives are added thereto. Ethyl cellulose, wax, etc. as a film reinforcing agent for forming and holding onto the support film (4) as a transfer foil.
These include ethylene-vinyl acetate copolymer.

Figure 2 is a diagram in which the support film (4) has been peeled off and electronic components (5) such as ICs, diodes, and resistors have been mounted. It is plated, solder plated, nickel metal plated, etc. 3 to 5 show examples according to the present invention, and FIG. 3 shows a printed board with soldering flux (3) transferred onto the printed board shown in FIG. After applying flux (7) (medium edge)'# (61) by dip coating and adhering the liquid soldering flux (7) to the tip of the K IJ card as shown in No. 411, immerse it in a solder bath. Solder.

FIG. 5 shows this state, in which the solder (8) completely connects the lead wire (6) and the electrode (2). The liquid soldering flux (7) is a solvent-free flux that does not contain any solvent, and it works to assist the soldering flux action formed on the printed board by the transfer method. Liquid soldering flux (7) is suitable for acids that have the role of removing oxides and promoting wetting of solder, and have a slight corrosive effect.
Organic acids such as lactic acid and olefinic acid, which are liquid at room temperature,
Alternatively, organic acids such as valmitic acid, stearic acid, and isostearic acid, which become liquid when heated at 100°C or less, wood rosin, gum rosin, tall oil rosin, and polymerized rosin by dimerization of these rosins, hydrogenated disproportionate esterification, etc. The rosin is made of one or a combination of two or more modified rosins.

, 1! iJ Organic Acid Binding [Saturated fatty acids such as valeric acid, butyric acid, and caproic acid can also be used, but they are undesirable for work due to their odor, and the solder melting temperature (&-Pb eutectic solder melting point 183℃, For general soldering, the working temperature is 220°C to 28°C.
It is also possible to use adipic acid, tartaric acid, maleic acid, etc., which become liquid when heated at temperatures below 0°C), but high temperature heating is not preferred for the sake of operation.

Materials that melt at low temperatures below ℃ are suitable.

In Fig. 4, the part of the inserted lead wire (6) below the printed circuit board 1 that is not coated with liquid soldering flux (7) is pushed up by the solder due to the difference in specific gravity in the solder bath, and the liquid soldering is caused by the flux (7). ) wets the lead l1l (61) evenly and uniformly, making it possible to achieve a perfect solder joint as shown in FIG.

As explained above, according to the present invention, soldering of pinholes, bridges, etc. that are caused by no flux formation on the lead wires of electronic components during flux formation by the transfer method is not possible. By applying a solvent-free liquid flux to the lead wire before forming, it takes advantage of various advantages such as the uniformity of the coating amount of the transfer method, preventing fat from seeping onto the back side of the printed board, and reducing the risk of fire. It was an excellent product that enabled reliable soldering and significantly improved the poor quality of soldering.

Next, examples will be shown.

Example 1 A flux solution consisting of the composition of polyester film 25μ (Toshi It) K lower 1e was applied by a gravure coating method using a gravure plate with a plate depth of B5μ, and after drying, the coating amount was 1
It was B fly4.

The 7 lux transfer paper obtained by this pressure was applied to a printing board (
Steel clad laminate → Etching resist printing → Etching → Etching resist removal → Ruder resist printing → Hardening →
(Created from character/mark printing to punching process) K transfer. The transfer was performed using a roll transfer machine made of silicone rubber four rollers at a roll temperature of 100°C, pressure of 41, and transfer speed of 5.
It was done under the rules.

After cooling, peel off the polyester film that is the support film, and then remove the electronic parts (lead wire material: 2 solder-plated steel III).
), and then dipped the lead wire into a column filled with lactic acid using lactic acid, which is liquid at room temperature, as a soldering flux to form a soldering F@7 flux on the lead wire portion according to the present invention. It was formed on the tip of the lead wire.

Example 2 As in Example 1, after forming soldering flux on a printed board and inserting electronic components, soldering flux was made by heating balmitic acid (melting point 63°C), which is solid at room temperature, to 80°C and turning it into a liquid. A lead wire was immersed in it and formed at the tip of the lead.

In order to prevent solder scattering due to heat-synthesis in a soldering bath, the printed circuit board (IN) with electronic components mounted on it which was flux-formed according to the above embodiment was heated at 100° C. using an infrared heater.
When soldering was carried out using a jet soldering device heated to 1 degree Celsius and heated to 25 degrees Celsius, it was possible to obtain good soldering without any pinholes or icicles. There was no evidence of flux seeping onto the back of the printed board, which is an advantage of this method, and the soldering was good.

[Brief explanation of drawings]

FIG. 1 and FIG. 1 are explanatory diagrams for explaining the flux forming method of the present invention. FIGS. 3, 4, and 5 are explanatory diagrams of an embodiment in which electronic components are soldered to a printed board by the 7-lux forming method of the present invention. 1 fI plate 2 Electrode 3 7 lux for soldering 4 Support film 5 Electronic components 6 Lead wire 7 Liquid soldering flux 8 Solder patent applicant Representative of Toppan Printing Co., Ltd. Kazuo Suzuki 22211 Figure 4 3 Figure 5

Claims (1)

[Claims] (11) Coat and form a soldering flux on a smooth support film, bring the soldering wiring board into close contact with the flux surface, transfer by heating and pressing, and then attach the electronic components to the wiring board from the back side. After inserting the lead wire, apply liquid soldering flux made of organic acids such as lactic acid, oleic acid, palmitic acid, or stearic acid, or rosin resin, which becomes liquid when heated at room temperature or below 100°C, to the lead binding part of the electronic component. A method for forming a flux, characterized in that the flux is applied by dip coating.