RU2389163C1 - Method of convection soldering of sm components and device to this end - Google Patents

Abstract

FIELD: process engineering. ^ SUBSTANCE: invention can be used for assembly/disassembly of SM components on one-side, double-side and multi-layer PCBs of radio electronic modules with the help of convective heating. Proposed method exploits air flow effects on component terminals in the following soldering conditions, i.e. temperature saturation, melting and cooling at different air temperature and airflow action duration. Note that melting conditions is realised by reducing and locking the distance between SM component and solder iron by hot air with the help of spring-loaded lever. Note also that required distance is set with the help of limiter with locking screw, bracket lever travel fine adjustment screw and measuring plate. ^ EFFECT: simplified process, reduced production costs. ^ 2 cl, 1 dwg

Description

The invention can be used for local installation and dismantling with surface-mounted components in modern buildings of a wide range of single, double-sided, single-layer and multi-layer printed circuit boards of electronic modules by convection heating. The method of convection heating of surface-mounted components is based on the effect of air flow on the component terminals during the following soldering modes - heating, temperature saturation, melting and cooling, having different air temperatures and duration of exposure, and the fusion mode is implemented by reducing and fixing the distance between the surface component mounting and soldering iron with hot air using a lever with a spring, and the required distance is set using a limiter I am with a fixing screw, a fine adjustment screw for the lever arm travel and measuring scale. In this case, the temperature and speed of the supplied air does not require automated changes. The method and device can simplify the process of convection-heating soldering when performing local installation and dismantling works, and also allows to reduce production costs for the implementation of the above operations.

The invention relates to the field of technological equipment and can be used for local installation and dismantling with surface mount components.

Of the known, the closest in essence is the method of convection heating brazing, when the component is assembled and disassembled by melting the solder with a stream of heated air supplied from a hot air gun, where the air temperature and duration of each soldering mode are maintained by a closed control system, and the fusion mode is implemented by automated increase temperature and air velocity [1].

The disadvantage of this method is the complexity of the technological process of these installation and dismantling works with components of surface mounting, which leads to an increase in labor costs, and therefore, to increase the cost of the product.

A device [2] is known, by which the soldering by convection heating of surface mounting components is performed. This convection system is a technical complex built on the basis of a hot air soldering station, and also containing a stand including a base on which a column is mounted, on which a printed circuit board holder is mounted, under which a lower heater with adjustable convection heating is installed, is mounted on the column bracket with fixing screws; a hot air soldering iron, which is part of the soldering station for soldering, is installed and fixed by means of a fixing screw in the bracket hot air. The heating method is an active convection in a closed volume, which is formed by the internal cavity of the nozzle located during soldering above the component. The heating process is controlled by the thermal profile, which is created and recorded in the system memory using a personal computer.

The disadvantages of the known device are the complexity of the equipment of the convection system, the complexity of its operation, as well as the high cost of the system.

The invention is aimed at simplifying the method of convection heating brazing when performing local installation and dismantling operations with surface-mounted components, simplifying this soldering process, reducing equipment costs, and reducing the cost of performing the above work.

This is achieved due to the fact that a lever with a spring, a stopper with a fixing screw, a screw for fine-tuning the stroke of the lever of the bracket and a measuring scale are installed on the bracket, the lever with a spring and a stopper with a fixing screw are interconnected, and the screw for fine-tuning the stroke of the lever is set to bracket under the limiter on one axis, and the measuring scale is mounted on the bracket parallel to the axes of the fine adjustment screw and limiter, while changing the lengths of the limiter and fine adjustment screw leads to a similar a different change in the stroke length of the bracket arm.

The invention is illustrated in the drawing, which schematically shows a device that implements the proposed method of brazing by convective heating of surface mounted components. The device comprises a rack including a base 1, on which a column 2 is mounted, on which the holder 3 is attached with a bolt 4, sheet asbestos 6 is laid over the area of the holder, on which a burner of increased power 5 is installed, the power cable is mounted to the latter and the heating pallet 7 is attached , on which a heating stand 8 is mounted by means of a heat-conducting paste, a bracket 16 with two fixing screws 17 and 18, a lever with a spring 19, a limiter 20, a fine adjustment screw x is mounted on a tripod and the lever arm 21 and the scale 22, and is installed in the bracket is fixed by the fixing screw 18 hot air solder 9, a part of solder for soldering station 10 of hot air with controlled heating and air flow rate. This design makes it possible to reproduce standard soldering modes by convection heating with high quality of the obtained results, without putting into operation complex expensive equipment.

The proposed method is implemented as follows. After adjusting the lengths of the limiter 20 and the screw for fine-tuning the stroke of the lever of the bracket 21 on the measuring scale 22, we set the necessary power mode for the high-power burner. The device is connected to a 220 V power outlet. After 20 minutes, a burner of increased power reaches an equilibrium state of heating, while the temperature on the heating pallet reaches about 280 ° C. The printed circuit board 11 of the electronic module on racks of the required length is installed on the heating pallet, so that the centers of the soldering iron with hot air, the surface mount component 12 and the heating stand 8 are on the same axis. A thermocouple 13 is mounted near the surface mount component to control the soldering temperature. This thermocouple is connected to a multimeter or digital thermometer 15. The number of connected thermocouples is not limited. To isolate the component to be soldered from the already installed elements on the board and create the necessary heat fluxes, a tin cone 14 is installed in the area of the surface-mounted component. After 7-10 minutes, the printed circuit board of the module is heated to an equilibrium state - about 125 ° C. Set the required settings on the soldering station for soldering with hot air. Turn on the soldering station. After a minute, the temperature in the region of the surface mount component is ~ 183 ° C, which is the eutectic point of lead-containing solders. Next, gently lower the lever with the spring 19 of the bracket 16, thereby reducing and fixing the distance between the surface mount component and the hot air soldering iron. After 30-40 seconds, the temperature in the region of the surface mount component will be ~ 225 ° C, which is the temperature of the fusion mode of the soldering of lead-containing solders. Next, you need to raise the bracket lever and disconnect the system from the 220 V power outlet. The circuit board will cool to room temperature in 10-15 minutes. The above modes correspond to the modes of preheating, temperature saturation, melting and cooling of the standard thermo-profile of convection heating soldering. This fact determines the high-quality soldering of surface mount components, which is also confirmed by the data of the experiment with a component with a matrix of ball terminals in an amount of 400 and the results of x-ray inspection.

The following operations are common to conventional convection soldering systems of a similar profile. The selection of the soldering mode (selection of the air flow rate, heating and time at each stage) is carried out for each specific type of element and depends on many different factors (type of surface-mounted component, module mounting density, number of PCB layers, solder paste composition, etc. ) Recording and testing of thermal profiles can also be done using a personal computer, ensuring its connection to a multimeter or digital thermometer, which, in turn, increases the efficiency of the above work.

INFORMATION SOURCES

1. Grachev A.A., Melnik A.A., Panov L.I. Design of electronic equipment based on surface mounting of components. - M.: NT Press, 2006 .-- 384 p.

2. Surface mounting: technological equipment. - M .: CJSC Enterprise "OSTEK", - 2007. - 162 p.

Claims (2)

1. The method of convection heating brazing of surface-mounted components, including the effect of air flow on the component leads under the following soldering modes: heating, temperature saturation, melting and cooling, having different air temperatures and duration of exposure, characterized in that the melting mode is implemented by reducing and fixing the distance between the surface mount component and the hot air soldering iron using a lever with a spring, and the required distance is set using a stop with a fixing screw, a fine screw for adjusting the travel of the arm of the bracket and the measuring scale. 2. A device for convection-heating brazing of surface-mounted components, comprising a rack including a base, on which a column is mounted, on which a holder of radio-electronic modules is mounted, under which a lower heater with adjustable convection heating is mounted, and to the last a power cable and a heating pallet with a stand are mounted , a bracket with fixing screws is attached to the column, and a hot air soldering iron with a fixing screw is mounted and fixed by means of a fixing screw on the bracket adjustable by heating and air flow rate, characterized in that a lever with a spring, a stopper with a fixing screw, a screw for fine-tuning the stroke of the lever of the bracket and a measuring scale are installed on the bracket, the lever with a spring and a limiter with a fixing screw are interconnected, and the fine adjustment screw the lever travel is mounted on the bracket under the limiter on one axis and the measuring scale is mounted on the bracket parallel to the axes of the fine adjustment screw and limiter.