Portable equipment for monitoring and controlling the level of oxygen in reflow oven atmosphere

Abstract

The present invention describes a portable device for monitoring and controlling the level of residual oxygen in reflow oven atmosphere (1). This referred equipment is able to determine the quality of the atmosphere of a reflow oven, using parameters predetermined by the user. Therefore, the equipment performs the monitoring of the reflow oven atmosphere (1) controlling the level of residual oxygen of the reflow oven (1) by increasing or decreasing of the feed flow rate of nitrogen by the control that the microcontroller exerts over the proportional valve of nitrogen flow control (9), by opening or closing the valves to kept such predetermined values.

Claims

1. Portable equipment for monitoring and controlling the atmosphere of reflow ovens, comprising: a nitrogen injection flow control box comprising at least one ball-type manual valve, at least one nitrogen pressure regulator with pressure gauge, a proportional valve of nitrogen flow control; and a cleaning line comprising a ball-type manual valve of the cleaning line and nitrogen pressure regulator of the cleaning line with a manometer; a collecting and analysis box comprising a line filter, at least one solenoid valve, a lambda sensor coupled with an analysis chamber, a signal converter, a flow meter with needle valve, and a diaphragm-type vacuum pump; and a box with a programmable controller, and a display with communicative interface comprising of a microcontroller, and a signal converter the lambda sensor coupled with an analysis chamber connected with one to another by electrical cables.

2. The portable equipment according to claim 1, wherein the cleaning line is used for cleaning a sampling system utilizing nitrogen.

3. The portable equipment according to claim 1, wherein the solenoid valve controls the flow rate of a cleaning sample or nitrogen.

4. The portable equipment, according to claim 1, wherein a desired value of oxygen in the reflow surroundings is preselected through a communicative interface.

5. The portable equipment, according to claim 1, wherein the lambda sensor coupled to an analysis chamber sends electrical signal to the signal converter.

6. The portable equipment, according to claim 1, wherein the microcontroller uninterruptedly evaluates and controls oxygen values collected in the collecting and analysis box of samples and makes a comparison with values of the atmosphere predetermined by a user.

7. The portable equipment, according to claim 1, wherein the microcontroller sends a control signal to the control box of nitrogen flow that coordinates opening and closing of the proportional valve of nitrogen flow control.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic flow diagram of the portable equipment for monitoring and controlling the atmosphere of reflow ovens.

DETAILED DESCRIPTION OF THE INVENTION

(2) This invention describes the portable equipment for monitoring and controlling the atmosphere of reflow ovens (1).

(3) The referred equipment is capable of: instantly ascertain the quality of the atmosphere of a reflow oven (1), to perform its monitoring and control.

(4) According to FIG. 1, the portable equipment for monitoring and controlling the atmosphere of reflow ovens (1) has: a collection and analysis box (3), a control box of nitrogen injection flow (2), a box with programmable controller, electrical power and display with communicative interface (4), connected with one another by electrical cables of power and logic.

(5) The control box of nitrogen injection flow (2) is comprised of ball-type manual valves (5), nitrogen pressure regulators with pressure gauge (8), proportional valve of nitrogen flow control (9) located between the nitrogen network and the reflow oven (1).

(6) There is a cleaning line (16) that comes out of the box control of nitrogen injection flow (2) which can be used to clean the sampling system using nitrogen. The cleaning line (16) is comprised of a ball-type manual valve of the cleaning line (6) and nitrogen pressure regulator of the cleaning line with pressure gauge (7).

(7) The collecting and analysis box (3) is comprised of line filter (10), solenoid valves (11) to control the input of cleaning sample or nitrogen, a lambda sensor coupled to an analysis chamber (12) which sends electrical signal to the signal converter (13), flow meter with needle valve (14) and a diaphragm-type vacuum pump (15).

(8) The box with the programmable controller, electrical power and display with communicative interface (4) is comprised of a microcontroller and an electrical panel of the control system.

(9) Operation of Portable Equipment for Monitoring and Controlling the Level of Oxygen in Reflow Oven Atmosphere

(10) The portable equipment for monitoring and controlling the atmosphere of reflow ovens (1) can be coupled to reflow ovens (1) of any brand and model for monitoring/controlling the reflow atmosphere.

(11) In the existing communicative interface in the box with programmable controller (4), the user preselects the desired values of oxygen on the reflow surroundings for a given recipe for the oven operation.

(12) Firstly, the equipment evaluates the values if the oxygen amount collected in the sampling collecting and analysis box (3) corresponds to an atmosphere within the desired operating recipe, as predetermined by the user.

(13) The microcontroller performs the control of the oxygen level in the reflow oven (1) by using as an ideal parameter the value preselected by the user. Additionally, the microcontroller informs the oxygen value measured through the equipment display and controls the nitrogen injection flow so that the oxygen level is kept in the reflow surroundings, according to that preselected by the user.

(14) The microcontroller continuously compares the oxygen levels desired predetermined by the oven operator (1) (set point) to real values presented during the operation performed at that time. The information on quality of the reflow atmosphere is obtained by the lambda sensor (12) in the collecting and analysis box (3) connected to the sampling line (17) of the reflow oven (1).

(15) After that comparison performed between the real values at the time of oven operation (1) and the values preset by the user, a command signal is sent from the microcontroller to the nitrogen flow control box (2), which then coordinates if the proportional valve of nitrogen flow control (9) must be open or closed. Therefore, it is possible to control the desired amount of oxygen in the reflow atmosphere.

(16) This system was designed to control oxygen concentrations below 3000 PPM, in the reflow oven surroundings (1). This way, during the monitoring the equipment detects that there is too much oxygen in the reflow oven surroundings (1) (levels above those previously determined by the user), the equipment automatically injects more nitrogen to the reflow oven (1) until the level predetermined by the user is reached.

(17) On the other hand, when the level of residual oxygen in the reflow surroundings is extremely low (below those values predetermined by the user), the equipment automatically reduces the nitrogen flow into the reflow oven (1), by closing the proportional valve of nitrogen flow control. (9).

(18) When the oxygen level is according to what has previously been predetermined by the user, the equipment automatically locks the open position of the proportional valve of nitrogen flow control (9). This way, it is kept a constant nitrogen injection flow into the reflow oven (1) until the moment at which the equipment detects that the oxygen level is no longer as predetermined by the user.

(19) Therefore, the use of a nitrogen amount lower or higher than that required for that oven specific operation (1) is avoided, preventing the waste of nitrogen, improving the quality of the final product of which specification requires low oxygen concentration in the reflow surroundings.

(20) Although the invention has been extensively described, it is obvious to those skilled in the art that several changes and modifications can be made aiming at a design improvement without these changes being not covered by the scope of the invention.