SU1512728A1 - Method of tinning the wires of printed-circuit boards - Google Patents

Abstract

The invention relates to the manufacture of wired circuit boards, mainly loop-wired installation. The purpose of the invention is to reduce the time of tinning at 280-300 ° C and prevent overheating of the non-direct part of the wires and the printed circuit board during the tinning of wires with varnished insulation. After inserting loops of wires into the holes of the board and fixing them, they perform preliminary fluxing and short-term immersion in the molten solder. As a result, microcracks are formed on the lacquer film. When re-fluxing, the flux in microcracks interacts with the bare metal. The method makes it possible to reduce the tinning time at the operating temperature by 2-4 times and to reduce the tinning temperature by 70-100 ° C. 1 tab.

Description

one

(21) 4361183 / 25-27

(22) 01/08/88

(46) 10/07/89. Bul Number 37

(72) E.M. Tereshchenko and V.M.Emelnov

(53) 621.791.3 (088.8)

(56) USSR Copyright Certificate №} 201077. cl. At 23 K 1/08, 1984.

(54) METHOD FOR TREATING PCB WIRES

(57) The invention relates to a technology for the manufacture of wired circuit boards, mainly loop-wired installation. The purpose of the invention is to reduce the time of tinning at 280-300 ° C and prevent overheating of the non-direct part of the wires and the printed circuit board during the tinning of wires with varnished insulation. After inserting loops of wires into the holes of the board and fixing them, they perform preliminary fluxing and short-term immersion in the molten solder. As a result, microcracks are formed on the lacquer film. When re-fluxing, the flux in microcracks interacts with the bare metal. The method makes it possible to reduce the tinning time at the operating temperature by 2-4 times and to reduce the tinning temperature by 70-100 ° C. Table I

The invention relates to the technology of manufacturing wired printed circuit boards, mainly loop-wired installation.

The purpose of the invention is to reduce the time of tinning at 280-300 ° C and prevent overheating of a small part of the wires and the printed circuit board during the tinning of wires with lacquer insulation.

The introduction of a pre-fluxing operation and the placement of wire-hinge loops in the molten solder for carrying out thermochemical impact significantly reduces the residence time of the wires in the molten solder until the quality of the tinning and the solder temperature are obtained.

The mechanism of the positive effect can be explained by the example of the tinning of the PEVTLK wire. The time of the tinning of the PEVTLK wire by placing it into the molten solder is known by a known method depending on the process temperature. The dependence of the time of the PEVTLK wire tinning on the temperature of the solder is given in the table.

S

(L

At 380 ° C, the tinning time (3c) meets the requirements of the soldering standards, however, the molten solder at this temperature is subjected to active oxidation and requires complex and costly protection. The high solder temperature is actively retracted to the copper core wire, and despite the acceptable tinning time, the insulation of the wires, especially short jumpers, is disturbed on the back side of the board, leading to short circuits. At / ° 28b-300 ° C, typical for baths Toning, long time of tinning of the wire is explained by the thermal nature of the destruction of the insulation. Due to the fact that the flux interacts with the surface of the wire, which in the initial stage of the process represents the surface of a strong lacquer film, in the first seconds of immersion in the solder, its role in this method of tinning is minimal. Concord

1C

1HE

00

But the proposed method in the process of pre-immersion in solder for a short time under the action of temperature and flux micro varnish film breakdown occurs and when the wire is fluxed a second time and immersed in solder, the microcrack flux interacts with the bare metal, its role in removing the insulation increases immeasurably, and the tinning time is significantly reduced.

Thus, the essence of the proposed method is that according to the method of tinning wire installation loops, including applying a protective mask, inserting wire loops in the holes of the board and fixing them, fluxing, tinning the wire loops in melted solder, removing the protective mask, before fluxing is introduced An additional step is that the hinges are pre-fluxed and placed in the molten solder for a short time sufficient to conduct a thermochemical shock.

The method is carried out as follows. Elastic pads are placed in the device for wire installation to hold the loops, mask, and blank board. In a known manner, manual or automatic tools are wired onto the surface of the board by inserting loops into the holes of the board and securing them in an elastic material. Then the elastic pads are removed, the loops are fluxed and briefly placed in the molten solder. The product is removed, the loops are again fluxed and put into the molten solder for the time of tinning. Then ud. Sew a protective mask.

Example I. PEVT / 1K 0 0.1 wire is tinned by placing it into molten solder at / ° 280 ° C. The end of the wire is fluxed, the PCR flux is placed in the molten solder and held for 3 s. Then the wire is removed from the solder, again fluxed and placed in the solder for 5 s. The extracted wire has an edged end to be unpacked to the contact pad.

Example 2. Group tinning of wire wired loops diluted on a blank board of size 200X280 is performed.

The wire of PEVTLK 0 is 0.1, the number of loops is 3200, the temperature of the solder in a tinning installation is 300 ° C. Loops to be tinned, fluxed dipping m in the tub with flux

FCSP. Then, the board is fixed in a rotary device for group tinning. The cleaning mechanism removes an oxide layer from the surface of the mirror; the board is installed above the mirror, lowered to

immersing the loops in the molten solder, stand for 3 s, and then automatically return to its original position. The board is cooled in air, fluxed by dipping in a PCB flux bath and the solder mirror cleaning mechanism is activated again. Using a rotating device, the board is placed above the mirror with solder, lowered before the loops are dipped into the molten solder and held for 3 seconds, after which they are automatically returned to

the initial position, the mask is removed.

As a result, 95% of the loops were laid.

The use of the proposed method of tinning loop-hole mounting allows a 2-4-fold reduction in the tinning time at working temperature and 70-100 ° C to reduce the process temperature, thereby eliminating overheating of the solder, board and wiring and increasing the reliability of wiring.

Claims (1)

Invention Formula A method of wiring a wire of printed circuit boards, including applying a protective mask, inserting wire hinges into the holes of the board and fixing them, fluxing, immersing the loops in the molten solder, removing the protective mask, characterized in that in order to reduce the time of tinning at 280-300 ° C and to prevent overheating of the non-part of the wires and the printed circuit board, when tinning the wires with lacquer insulation, after fixing the loops in the holes of the printed circuit board, perform preliminary fluxing and short-term immersion in the molten board. Sing to form microcracks on the lacquer film.