JPH02160071A - Dipping tank - Google Patents

Abstract

PURPOSE:To prevent sticking of a moistureproof liquid to lead terminals by disposing a dipping tank in the state of enclosing the tank with a dipping liquid and heating the dipping liquid in the dipping tank the via dipping liquid in an outside tank. CONSTITUTION:The dipping tank has the outside tank 20, a heater 21 provided in the outside tank and the dipping tank 27 disposed in the state of enclosing the tank with a paraffin liquid 25. The paraffin liquid is filled in the dipping tank to about the level at which the liquid nearly overflows. The overflowing paraffin liquid 29 in the dipping tank 27 is received by the outside tank 20. The level of the liquid surface is maintained uniform in this way. A printed circuit board 2 is immersed into the paraffin liquid in the dipping tank 27 in the state of allowing the junctions to the lead terminals to remain slightly by taking the distance at which the paraffin line is resin along the circuit board surface by the surface tension into consideration. The height of the liquid surface is easily maintained in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a dip tank, and relates to, for example, an improvement in a dip tank used when a printed circuit board is immersed in a moisture-proofing liquid in order to perform moisture-proofing treatment on the printed circuit board.

(Prior Art) - For example, there is a hybrid IC as shown in FIG. 3, in which a plurality of ICs and other electronic components are mounted on a single printed circuit board 1.

That is, the hybrid TCI shown in FIG.

A plurality of Dl f' (Dual In 1.ine'
It is mounted with an ackagel type ROM 3 or other electronic components. To connect the lead terminals (lead electrodes) 4 to such a hybrid ICI, a large number of lead ends r-4 are connected in advance in a ■ shape using the connecting piece 7, and the ends of each lead terminal 4 are branched into two. Soldering is often performed with each conductive pattern 9 formed on the periphery of the printed circuit board being held under pressure by the supporting portion.

Printed circuit board 2 with the mounting and terminal connections completed in this way
After applying phenol liquid to the entire surface to form a protective film, as shown in FIG. It is common to perform moisture-proofing treatment by dipping the lead terminal in water, and then cut off the tip of the lead terminal including the connecting piece 7 after the moisture-proofing treatment is completed.

At this time, if the molten paraffin as a moisture-proofing material remains and solidifies at the edge of the printed circuit board 2 where the lead terminals 4 are connected, there is a problem that it becomes impossible to closely attach the edge of the printed circuit board to the motherboard.

Therefore, when dipping such a hybrid IC in a paraffin bath, especially when automating the process, the entire surface of the printed circuit board 2 is not immersed in the liquid, as shown in FIG. The jig is set to leave a small portion of the paraffin for dipping, and the dipping of the parts protruding from the liquid level depends on the rise in the liquid level due to the surface tension of the molten paraffin, so the liquid level is not maintained uniformly. Otherwise, there is a risk that paraffin may adhere to the terminals or that uncoated areas may be formed on the printed circuit board.

However, conventional dip baths were generally of the bath type and did not have a liquid level adjustment function, so the liquid level was likely to fluctuate due to a decrease in liquid, and it was difficult to use paraffin. It was difficult to uniformly apply it only to the printed circuit board.

To solve this problem, silicone rubber or the like is sometimes applied using a syringe near the boundary between the lead terminal and the board edge, as shown by the dotted line in Figure 4, but it takes a lot of man-hours to peel it off afterwards. There was a flaw.

In addition, since the paraffin liquid in the tank is configured to receive heat directly from the heater 17, the paraffin burns and stains the entire liquid, reducing transparency, so the resin surface coated on the printed circuit board or its L. - There was also the disadvantage that characters, codes, numbers, etc. printed on the paper were difficult to see.

Furthermore, in tank-type dip tanks, it is difficult to maintain the temperature of the paraffin liquid in the tank evenly, so there is a drawback that the thickness of the paraffin that is cooled and solidified after deposition varies. Ta.

(LI aspect of the invention) The present invention was made in order to eliminate the drawbacks of the conventional dip tank as described above, and a printed circuit board that has been mounted with mounted components and connected with lead terminals is dipped in a moisture-proof liquid. In particular, it is an object of the present invention to provide a dip bath in which the possibility of moisture-proofing liquid adhering to lid terminals is greatly reduced.

(Summary of the Invention) In order to achieve the above object, the present invention has an outer tank and a dipping tank disposed in the outer tank surrounded by a dipping liquid, and the dipping liquid in the dipping tank is exposed to the outside. It is characterized by being boiled in hot water using the dip liquid in the tank.

(Example) Hereinafter, the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.

FIG. 1 shows an embodiment of the daylab sliding according to the present invention, and this dip tank includes an outer tank 20 and a heater 21 provided in the outer tank.
and paraffin liquid (dip liquid) 25 in the outer tank.
It has an immersion tank (inner tank) 27 surrounded by a dipping tank (inner tank) 27.

The immersion tank 27 is filled with paraffin liquid 29 to the extent that it almost overflows, and the overflowing paraffin liquid 29 in the immersion tank 27 is received by the outer tank 20.

By doing this, it becomes easy to maintain the level of the liquid level uniformly, and when the liquid level decreases due to a decrease in the liquid 29, the liquid level is always kept at a constant level by replenishing the paraffin liquid at the appropriate time. It can be kept in place.

The printed circuit board 2 is placed in the paraffin solution in the immersion tank 27 with a slight connection part left with the lead end r, taking into consideration in advance the distance that the paraffin solution moves upward along the base surface due to surface tension. However, since it is easy to keep the level of the paraffin liquid 29 in the immersion tank 27 constant, it is necessary to hold the tip of the terminal 4 and mechanically lower it a certain distance. This makes it possible to achieve uniform coating with no excess or deficiency of H on all printed circuit boards connected via lead terminals.

Furthermore, although it is difficult to equalize the temperature of the paraffin liquid 25 in the outer tank 20 which directly receives heat from the heater 21, it is easy to equalize the temperature of the paraffin liquid 29 in the soaked tnM 27 by boiling in hot water. .

A uniform moisture-proof film can be formed over the entire printed circuit board.

Furthermore, unlike the paraffin in the outer bath, the paraffin in the immersion bath will not burn due to overheating of the heater, so it can maintain its transparency, and even when coated on the surface of a substrate, characters written on the surface will not be scorched. There's nothing to cover up.

FIG. 2 shows another embodiment of the present invention, which prevents liquid from scattering on the outside of the outer tank 20! By providing a cover 30 that protects the tank, work safety and cleanliness around the tank are maintained.

In addition, although the above embodiment mainly describes the process of applying paraffin as a moisture-proofing liquid to a printed circuit board in a dip method, the present invention is generally applicable to other cases in which a liquid material such as molten solder is applied in a dip method. It is possible to apply.

(Effects of the Invention) As described above, the present invention has an outer tank further disposed outside the immersion tank H1 for dipping objects to be coated such as printed circuit boards.
Since the tank has a multi-tank structure and the liquid level adjustment can be completed by filling the clay soaking tank, the liquid level can be easily maintained. Therefore, when automatically dipping printed circuit boards, etc.

It is possible to obtain an appropriate coating state simply by mechanically moving it up and down a certain distance.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing a preferred embodiment of the present invention, Fig. 2 is an explanatory diagram of the configuration of another embodiment, and Fig. 3 is an explanatory diagram showing a preferred embodiment of the present invention.
FIG. 4 is an explanatory diagram of a conventional dip tank. 20... Outer tank 21... Heater 25... Paraffin liquid (dip liquid) 27... Immersion tank (inner tank) 29... Rose 7 (liquid patent applicant Toyo Tsushinki Co., Ltd. agent) Patent Attorney Hitoshi Suzuki Figure 1 Figure 31 Figure 2 Figure 4

Claims (1)

[Claims] It has an outer tank and an immersion tank disposed in the outer tank surrounded by the dip liquid, and the dip liquid in the immersion tank is heated through the dip liquid in the outer tank. Features a dip tank.