Limiting of corrosion in machine for reflow soldering in vapor p

Details Limiting of corrosion in machine for reflow soldering in vapor p Limiting of corrosion in machine for reflow soldering in vapor p

1986-12-02

1988-05-31

Yuen, Henry C.

Drying and gas or vapor contact with solids

Apparatus

With means to treat gas or vapor

432197, 432210, 34 36, 134 31, F26B 1118, F27B 1500

Patent

active

047472189

DESCRIPTION:

BRIEF SUMMARY
The main object of the invention is the limiting of corrosion in a vapor phase reflow soldering machine.


BACKGROUND OF THE INVENTION

The increasing number of connections to be welded on electronic cards and, especially, the development of electronic cards produced in small batches have promoted the development of machines for reflow soldering in vapor phase. When soldering in vapor phase, the solder metal is deposited, in an initial stage, in the form of paste or solid solder preform. The soldering as such is performed in a second stage by the addition of heat. The heat is obtained by the condensation of primary liquid on the component. The primary liquid is heated to its boiling point which is above the melting point of the solder, so as to obtain a zone of saturated vapor. At atmospheric pressure, the temperature of the saturated vapor zone is the same as the boiling temperature of the liquid. Since the entire surface of the object to be soldered is in contact with the vapor, this vapor is heated uniformly and provides for the simultaneous soldering of all the connections that have to be made.
The part or component to be welded is plunged in a primary vapor zone. This vapor condenses upon contact with the part, thus providing for the addition of heat and for the melting of the previously deposited solder.
With a view to reducing losses of primary liquid through convection, diffusion or leakage, a secondary vapor zone forming a barrier is created, using a liquid which is often of greater density and lower boiling temperature and is less costly.
A liquid frequently used as a primary liquid is, for example, the one marketed by the 3M Company under the brand name "Fluorinert" with the reference FC 70. The secondary liquid used may be, for example, trifluorotrichloroethane with the formular CFCl.sub.2 --CCIF.sub.2. The method of vapor phase soldering uses liquids containing fluorine which are heated to high temperatures, for example 215.degree. C. At these temperatures, the primary and secondary liquids tend to decompose partially, the secondary liquid releasing Cl.sup.- and F.sup.- ions. The presence of these ions will cause two types of corrosion: firstly, a dry corrosion through the formation of the chloride and fluoride of the affected metals, and secondly an aqueous corrosion through the formation of acid in the presence of water. The presence of chlorine and fluorine ions has two consequences: firstly the corrosion of the vapor phase soldering machine, and secondly the presence of ions on the soldered parts, possibly leading to corrosion.


BRIEF DESCRIPTION OF THE INVENTION

The device according to the present invention proposes the complete elimination of water from the secondary liquid and, thereby, the elimination of the acid corrosion due to this liquid.
The main object of the present invention is a machine for reflow soldering in vapor phase, comprising a tank which contains a boiling primary liquid and a vaporized secondary liquid. The machine is designed to limit the losses of primary liquid, and also includes means for washing the secondary liquid and means for removing water from the secondary liquid as well as a storage vessel containing secondary liquid, and means for hermetically sealing the washing means from the water-removal means.


BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood from the following drawings with the appended figures which are given as non-exhaustive examples. Of these figures:
FIG. 1 is a diagram of a device according to the prior art;
FIG. 2 is a diagram of an initial alternative mode or embodiment of the device for regenerating the secondary liquid according to the invention;
FIG. 3 is a diagram of a second mode or embodiment of the device for regenerating the secondary liquid according to the invention;
FIG. 4 is a diagram of a device for soldering under vapor phase according to the invention.
FIGS. 1 to 4 use the same references to designate the same elements.


DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 depicts a vapor phase solderi

REFERENCES:
patent: 3947240 (1976-03-01), Pfahl, Jr.
patent: 4090843 (1978-05-01), Chu et al.
patent: 4135803 (1979-01-01), Van Houwelington
patent: 4261111 (1981-04-01), Rand
patent: 4453916 (1984-06-01), Osipov et al.
patent: 4466198 (1984-08-01), Doll
patent: 4628616 (1986-12-01), Shirai et al.
patent: 4642904 (1987-02-01), Smith, Jr.

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