CN115220497A - Vacuum cavity heating device for vacuum reflow soldering furnace and temperature control method thereof - Google Patents

Abstract

The application discloses a vacuum chamber heating device for a vacuum reflow soldering furnace and a temperature control method thereof. The vacuum chamber heating device comprises: a vacuum chamber connected with a nitrogen generating unit; at least two groups of independently controlled radiation heating modules, Arranged in sequence along the upper cavity wall of the vacuum chamber for heating the vacuum chamber; each group of radiation heating modules is equipped with: a lamp module, including a plurality of radiation lamps arranged in parallel; and an independent Power feedthrough and thermocouple; among them, multiple groups of radiant heating modules work at the same time, independently control temperature, and together form a heating area in the vacuum chamber. The application takes both economy and flexibility into consideration, has a simple structure, is easy to install, and has flexible temperature control, and solves the problem of the prior art that the heating temperature needs to be customized.

Description

A vacuum chamber heating device for vacuum reflow soldering furnace and temperature control method thereof

technical field

The invention relates to the technical field of reflow soldering furnaces, in particular to a vacuum chamber heating device used in a vacuum reflow soldering furnace and a temperature control method thereof.

Background technique

Reflow oven (Reflow Oven) is a device that provides a heating environment to melt the solder paste by heat so that surface-mounted components and circuit boards can be reliably combined with the solder paste alloy.

Nitrogen protection in the reflow oven prevents easily oxidized materials such as solder and silver in the reflow zone from being oxidized at high temperatures and avoids soldering defects.

With the development of the electronic industry in the direction of miniaturization and multi-specification, people's requirements for product quality are getting higher and higher. In order to meet the new needs of the market and reduce product defects caused by welding, a vacuum reflow oven with a vacuum device gradually began to be widely used. The vacuum device can effectively reduce the size and quantity of solder voids during soldering in the reflow oven and improve the soldering quality.

Vacuum reflow oven is the key equipment of surface mount technology in electronic manufacturing industry. Its quality and operation directly affect the quality of final product, and once the soldering process is completed, to repair defective solder joints, components or circuit boards will become very complicated and expensive.

The function of the reflow zone is that the temperature rises rapidly to make the solder paste melt, and the liquid solder wets, diffuses, diffuses, or reflows the pads, component ends and pins of the PCB to form solder joints. The peak temperature of reflow soldering varies depending on the solder paste used. Generally, it is the melting point temperature of the solder paste plus 20 to 40°C. Since the viscosity and surface tension of the solder paste decrease with the increase of temperature, it is beneficial to promote the solder paste to be faster. wetting. Therefore, the ideal reflow soldering is the best combination of peak temperature and solder paste melting time. The ideal temperature curve is the tip area exceeding the melting point of the solder paste, the coverage area is the smallest and symmetrical, and the soldering time is generally 60-90s.

The reflow area of vacuum reflow soldering is located in the vacuum chamber. Generally, the heating equipment in the box is used, and the temperature in the box is about 320 °C; if it is heated internally, due to the vacuum environment, convection heating cannot be used, and the industry can only use heat conduction or radiation heating. . Due to technical limitations, the hot plate can generally only be set to one temperature, and the temperature curve required by the reflow soldering process cannot be flexibly adjusted. In radiation heating, some manufacturers use ceramic plate heating, and the temperature is controlled separately by the outer ring and the inner ring, and the temperature control is relatively rough. There is also a type of radiant heating that uses several radiant lamps for heating, multiple lamps work at the same time, and the temperature is controlled at the same time, which is high in cost and poor in flexibility.

Therefore, in the prior art, the vacuum chamber heating device used in the vacuum reflow oven needs to be further improved.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a vacuum chamber heating device for a vacuum reflow soldering furnace and a temperature control method thereof, so as to solve the problem existing in the prior art that the heating temperature needs to be customized, take into account the economy and flexibility, and can Flexible control of the process curve of vacuum reflow soldering in the reflow zone in the vacuum chamber.

To achieve the above object, the present invention adopts the following technical solutions:

In a first aspect, the present application provides a vacuum chamber heating device for a vacuum reflow oven, including:

The vacuum chamber is connected with a nitrogen generating unit;

At least two groups of independently controlled radiation heating modules are arranged in sequence along the upper chamber wall of the vacuum chamber for heating the vacuum chamber;

Each group of radiant heating modules is equipped with:

Lamp groups, including a plurality of radiant lamps arranged in parallel; and

Separate power feedthroughs and thermocouples;

Among them, multiple groups of radiant heating modules work at the same time and independently control the temperature, which together constitute a heating area in the vacuum chamber.

Preferably, the number of the radiation heating modules is 2 to 4 groups.

Preferably, the radiation lamp tube is a medium wave infrared heating tube.

Preferably, the thermocouple is a vacuum K-type thermocouple.

Preferably, a mirror surface reflection plate is installed on the lower side of the vacuum chamber, the mirror surface reflection plate is a whole flat plate, and the mirror surface reflection plate is arranged between the radiation heating module and the lower chamber wall of the vacuum chamber , and is separated from the lower cavity wall by a distance.

Preferably, a specular reflector is further provided above each group of radiation heating modules, and the specular reflector is provided with a mirror for reflecting the light emitted by the lamp tube group to the upper chamber wall of the vacuum chamber.

Preferably, the upper surface of each of the radiation lamps located on the upper chamber wall of the vacuum chamber is coated with a reflective coating, and the reflective coating causes the heat of the radiation lamps to be directionally reflected downward.

More preferably, the reflective coating is a white-plated reflective coating.

Preferably, at least two groups of independently controlled radiant heating modules are arranged on the lower cavity wall of the vacuum chamber in sequence, and the radiant heating modules located on the lower cavity wall and the radiant heating modules located on the upper cavity wall are arranged in a staggered manner. Or in an equal arrangement above and below.

More preferably, a second specular reflector is also provided below each group of radiation heating modules located on the lower cavity wall, and the second specular reflector is provided with a light beam for reflecting the light emitted by the lamp tube group of the lower cavity wall to The mirror surface of the lower chamber wall of the vacuum chamber.

More preferably, the lower surface of each radiant lamp tube of the radiant heating module located on the lower cavity wall of the vacuum chamber is coated with a reflective coating, and the reflective coating makes the heat of the radiant lamp tube directionally upwardly reflected.

In a second aspect, the present application also provides a temperature control method for a vacuum chamber heating device for a vacuum reflow soldering furnace, which is applied to the vacuum chamber heating device for a vacuum reflow soldering furnace described in the first aspect. The temperature control methods include:

Set the target temperature and stable deviation of heating for each group of radiant heating modules respectively;

Each group of radiation heating modules starts to heat, and the thermocouples of each group of radiation heating modules detect the temperature in real time;

Determine whether the detection temperature of the thermocouple is higher than the set threshold;

If it is higher than the set threshold, the alarm will send an over-temperature alarm, and the heating power will be cut off at the same time;

If it is not higher than the set threshold, the temperature controller receives the current temperature value collected by each thermocouple, performs PID calculation between the detected temperature value and the preset target temperature, and generates a control signal: if the current temperature value is the same as the set temperature If the difference between the target temperatures is greater than or equal to the stable deviation, it is determined that the current heating temperature of the radiation heating module corresponding to the thermocouple is too high, and then a control signal is sent to the power regulator to rapidly reduce the heating temperature to the preset target temperature ; If the difference between the current temperature value and the set target temperature is less than the stable deviation, it is determined that the current heating temperature of the radiation heating module corresponding to the thermocouple is too low, and then the control signal is sent to the power regulator to make the heating temperature Rapidly ramp up to the preset target temperature.

Compared with the prior art, the technical scheme of the present invention has the following beneficial effects:

The invention adopts multiple groups of independently controlled radiation heating modules, each group of radiation heating modules is installed with multiple radiation lamps, and is equipped with independent thermocouples and power feedthroughs, and multiple groups of independently controlled radiation heating modules work together. , you can set different temperatures, and flexibly adjust the process curve of the reflow zone of vacuum reflow soldering in the vacuum chamber. The invention takes both economy and flexibility into consideration, has simple structure, convenient installation and flexible temperature control, and solves the problem of the prior art that the heating temperature needs to be customized.

Description of drawings

The accompanying drawings constituting a part of the present application are used to provide further understanding of the present application, and the schematic embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation of the present application. In the attached image:

1 is a schematic diagram of the installation position of the radiation heating module of the present invention in a vacuum chamber;

Fig. 2 is the sectional view of Fig. 1;

Figure 3 is a top view of a single lamp tube group (covered with a specular reflector);

Figure 4 is a side view of a single lamp tube group (covered with a specular reflector);

Fig. 5 is the sectional view along the A-A direction of Fig. 4;

Fig. 6 is the structure schematic diagram of radiant lamp;

FIG. 7 is a schematic flowchart of the temperature control method of the vacuum chamber heating device of the present invention.

illustration:

1. Lamp group A; 2. Lamp group B; 3. Lamp group C; 4. Feed-through A; 5. Feed-through B; 6. Feed-through C; 7. Thermocouple A; 8. Thermocouple B; 9. Thermocouple C; 10. Radiation lamp tube; 11. Specular reflector; 12. Specular reflector; 13. Vacuum chamber; 14. Fixture inlet; 15. Fixture outlet; 16. Fixture delivery system.

Detailed ways

The present invention provides a vacuum chamber heating device for a vacuum reflow soldering furnace and a temperature control method thereof. In order to make the purpose, technical solutions and effects of the present invention clearer and clearer, the present invention is further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention.

It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above drawings are used to distinguish similar objects, and are not necessarily used to describe a specific sequence or sequence. It should be understood that data so used may be interchanged under appropriate circumstances. Furthermore, the terms "comprising" and "having", and any variations thereof, are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those expressly listed Rather, those steps or units may include other steps or units not expressly listed or inherent to these processes, methods, products or devices.

Example:

The application discloses a vacuum chamber heating device for a vacuum reflow soldering furnace, comprising:

The vacuum chamber is connected with a nitrogen generating unit;

At least two groups of independently controlled radiation heating modules are arranged in sequence along the upper chamber wall of the vacuum chamber for heating the vacuum chamber;

Each group of radiant heating modules is equipped with:

Lamp groups, including a plurality of radiant lamps arranged in parallel; and

Separate power feedthroughs and thermocouples;

Among them, multiple groups of radiant heating modules work at the same time and independently control the temperature, which together constitute a heating area in the vacuum chamber.

The number of the radiation heating modules may be 2 to 4 groups. This application does not limit the number of radiation heating modules, and the specific number can be adjusted according to actual needs.

1 to 2 are schematic diagrams showing the installation positions of three groups of independent radiation heating modules in the vacuum chamber. Referring to FIG. 1 to FIG. 2 , one side of the vacuum chamber 13 is provided with a fixture inlet 14 , and the opposite side thereof is provided with a fixture outlet 15 , and a fixture conveying system 16 is provided inside the vacuum chamber 13 . The jig entered at the jig inlet 14 is sent to the jig outlet 15 .

Three groups of independent radiation heating modules are installed above the vacuum chamber 13, each group of radiation heating modules includes a lamp tube group, and the three lamp tube groups are respectively the lamp tube group A 1, the lamp tube group B 2 and the lamp tube group. The lamp tube group C3 is arranged side by side and distributed at intervals on the lower surface of the upper cavity wall of the vacuum chamber 13 . Each lamp tube group includes two radiant lamps 10 arranged in parallel (refer to FIG. 6 ), and the temperature is controlled at the same time. In this way, a total of six radiant lamps 10 are heated in three groups. denser. Each lamp group has independent power feedthroughs (respectively feedthrough A 4, feedthrough B 5 and feedthrough C 6) and thermocouples (respectively thermocouple A 7, thermocouple B 8 and thermocouple Even C 9), independent temperature control heating, do not interfere with each other.

Wherein, the radiation lamp tube 10 is preferably a medium wave gold-plated infrared heating tube. Medium-wave gold-plated infrared heating tube is medium-wave double-hole semi-gold-plated, green and energy-saving, clean and safe, quick response, long life, easy to install, made of high-purity double-tube transparent quartz tube, 180° gold-plated on the back, and the reflection efficiency can reach 95%. The heating wire is made of nickel-chromium alloy, which will not oxidize and has a lifespan of 10,000 hours. The infrared wavelength range is 1.4-2.7μm, the peak value is 2.4-2.7μm, the heating wire temperature can reach 800-950 degrees, 100% full power output can be achieved in 20 seconds, and the temperature will drop rapidly. Of course, the radiation lamps 10 can also be replaced with other forms of radiation lamps.

Wherein, the thermocouple is preferably a vacuum K-type thermocouple. A thermocouple is a temperature sensing element and a primary instrument. It directly measures the temperature, converts the temperature signal into a thermoelectromotive force signal, and converts it into the temperature of the measured medium through an electrical instrument (secondary instrument). The basic principle of the K-type thermocouple wire is that two conductors of different compositions form a closed loop. When there is a temperature gradient at both ends, a current will flow through the loop. This is called the Seebeck effect. Homogeneous conductors with two different compositions are hot electrodes, the higher temperature end is the working end, the lower temperature end is the free end, and the free end is usually at a constant temperature. According to the functional relationship between thermoelectromotive force and temperature, a thermocouple graduation table is made. The graduation table is obtained under the condition that the temperature of the free end is at 0℃. Different thermocouples have different graduation tables. When the third metal material is connected to the K-type thermocouple wire loop, as long as the temperature of the two contacts of the material is the same, the thermoelectric potential generated by the thermocouple will remain unchanged, that is, the third metal will not be connected to the loop. Impact. Therefore, when measuring the temperature of the thermocouple, the measuring instrument can be connected, and the temperature of the measured medium can be known after measuring the thermoelectromotive force.

In order to better conduct and concentrate the energy of the infrared lamp tube on the heated material, in this embodiment, a reflective coating may also be added to the outer wall of the quartz tube. Specifically, a reflective coating may be applied to the upper surface of the outer wall of the quartz tube of each of the radiation lamps 10, so that the heat of each radiation lamp 10 is directionally reflected downward, so as to improve the heating efficiency. For example, the gold-plated reflective layer is a pure gold coating containing 15%, which is directly cured on the outside of the quartz tube at high temperature and can reflect more than 90% of infrared rays. The working temperature of the layer can reach about 600°C. For another example, the white-plated reflective coating is an alumina ceramic coating, which is cured on the surface of the quartz tube at high temperature and can reflect more than 65% of infrared rays. Although the reflection effect is not as good as that of the gold-plated coating, the working temperature can be as high as 900°C to 1000°C. The advantages of applying a reflective coating on the quartz tube are many, it can conduct more energy, shorten the heating time, and can also directional heating to reduce thermal interference.

In a preferred embodiment, a specular reflection plate 12 can also be installed on the lower side of the vacuum chamber 13. The specular reflection plate 12 is a whole flat plate, and the specular reflection plate 12 is arranged on the radiation heating module and the vacuum. The lower chamber walls of the chamber 13 are separated by a distance between and from the lower chamber walls. The specular reflector 12 allows the heat to be concentrated in the middle area of the vacuum chamber 13 as much as possible (the fixture is in the middle of the entire vacuum chamber 13 ), which enhances the heating efficiency of the radiant lamp 10 .

Referring to FIGS. 3 to 5 , in a preferred embodiment, a specular reflector 11 is further provided above each group of radiant heating modules, and the specular reflector 11 is provided with a reflector for reflecting the light emitted by the lamp tube group. The light reaches the mirror surface of the upper chamber wall of the vacuum chamber 13 . The specular reflector 11 is provided, so that the heat can be radiated downward as much as possible, and the heating efficiency can be improved. Of course, the specular reflector 11 can also be replaced with other plates or other materials for heat reflection.

In a preferred embodiment, the lower cavity wall of the vacuum chamber 13 can also be arranged with at least two groups of independently controlled radiant heating modules (not shown in the figure) in sequence. The radiant heating modules located on the lower cavity wall The radiant heating modules located on the upper cavity wall can be arranged in a staggered manner, or in an equal arrangement up and down. A second specular reflector can also be provided under each group of radiation heating modules located on the lower cavity wall, and the second specular reflector is provided with a light beam for reflecting the light emitted by the lamp tube group of the lower cavity wall to the vacuum cavity The mirror surface of the lower cavity wall of the chamber. The lower surface of each radiation lamp tube 10 located on the lower chamber wall of the vacuum chamber 13 may also be coated with a reflective coating, which makes the heat of the radiation lamp tube 10 reflect upwards in an upward direction, improving heating efficiency. That is, the radiant heating module installed on the lower cavity wall of the vacuum chamber 13 may have the same structure as the radiant heating module installed on the upper cavity wall, but the installation is reversed.

Referring to FIG. 7 , for the above-mentioned vacuum chamber heating device for a vacuum reflow soldering furnace, the temperature control method specifically includes the following steps:

Set the target temperature and stable deviation of heating for each group of radiant heating modules respectively;

Each group of radiation heating modules starts to heat, and the thermocouples of each group of radiation heating modules detect the temperature in real time;

Determine whether the detection temperature of the thermocouple is higher than the set threshold;

If it is higher than the set threshold, the alarm will send an over-temperature alarm, and the heating power will be cut off at the same time;

If it is not higher than the set threshold, the temperature controller receives the current temperature value collected by each thermocouple, performs PID calculation between the detected temperature value and the preset target temperature, and generates a control signal: if the current temperature value is the same as the set temperature If the difference between the target temperatures is greater than or equal to the stable deviation, it is determined that the current heating temperature of the radiation heating module corresponding to the thermocouple is too high, and then a control signal is sent to the power regulator to rapidly reduce the heating temperature to the preset target temperature ; If the difference between the current temperature value and the set target temperature is less than the stable deviation, it is determined that the current heating temperature of the radiation heating module corresponding to the thermocouple is too low, and then the control signal is sent to the power regulator to make the heating temperature Rapidly ramp up to the preset target temperature.

For example, set the target temperature of lamp group A 1 to 200°C, set the target temperature of lamp group B 2 to 300°C, set the target temperature of lamp group C 3 to 250°C, and set the stability deviation to ±1.5°C. . The three groups of lamps start to heat up, and the thermocouples detect the temperature respectively. Taking lamp group A1 as an example, when the thermocouple A7 of lamp group A1 detects that the temperature reaches 201.5°C, the DTM thermostat judges that the temperature exceeds the standard, and starts to send a signal to the power regulator SCR module to reduce the heating current, and the lamp The heating power of the tube group A 1 drops, and the temperature of the lamp group A 1 begins to drop; when the thermocouple A 7 of the lamp group A 1 detects that the temperature drops to 198.5 ℃, the DTM thermostat judges that the temperature is too low and starts to emit light. The signal is sent to the power regulator SCR module, the current is increased, and the heating power of the lamp group A 1 is increased. In this way, the temperature at the lamp group A 1 is stable and dynamically fluctuated within the range of 200±1.5°C, and the precise control of the current is run through the PID algorithm of the DTM thermostat. The working principle of the lamp group B 2 and the lamp group C 3 is the same as that of the lamp group A 1 , which will not be repeated here. Since the lamp group A 1 , the lamp group B 2 and the lamp group C 3 are independently controlled, the desired temperature curve can be easily modulated. The above-mentioned power regulator SCR, DTM thermostat can adopt commercially available products.

In summary, the present invention adopts multiple sets of independently controlled radiation heating modules, each set of radiation heating modules is equipped with multiple radiation lamps, and is equipped with independent thermocouples and power feedthroughs, and multiple sets of independently controlled radiation heating modules are installed. The heating modules work together, and different temperatures can be set to flexibly modulate the process curve of the reflow zone of the vacuum reflow soldering in the vacuum chamber. The invention takes both economy and flexibility into consideration, has simple structure, convenient installation and flexible temperature control, and solves the problem of the prior art that the heating temperature needs to be customized.

The specific embodiments of the present invention have been described above in detail, but they are only used as examples, and the present invention is not limited to the specific embodiments described above. For those skilled in the art, any equivalent modifications and substitutions to the present invention are also within the scope of the present invention. Therefore, equivalent changes and modifications made without departing from the spirit and scope of the present invention should be included within the scope of the present invention.

Claims (10)

1. A vacuum chamber heating apparatus for a vacuum reflow oven, comprising:

a vacuum chamber communicated with a nitrogen generating unit;

at least two groups of independently controlled radiation heating modules which are sequentially arranged along the upper cavity wall of the vacuum cavity and used for heating the vacuum cavity;

every group radiant heating module all disposes:

the lamp tube group comprises a plurality of radiation lamp tubes which are arranged in parallel; and

a separate power feed-through and thermocouple;

wherein, the multiple groups of radiation heating modules work simultaneously, independently control the temperature, and jointly form a heating area in the vacuum chamber.

2. The vacuum chamber heating apparatus for a vacuum reflow oven according to claim 1, wherein the number of the radiation heating modules is 2 to 4.

3. The vacuum chamber heating apparatus for a vacuum reflow oven of claim 1, wherein the radiant tube is a medium wave infrared heating tube.

4. The vacuum chamber heating apparatus for a vacuum reflow oven of claim 1, wherein the thermocouple is a vacuum K-type thermocouple.

5. The vacuum chamber heating apparatus for a vacuum reflow oven of claim 1, wherein the lower side of the vacuum chamber is mounted with a specular reflection plate, which is a one-piece flat plate, disposed between the radiation heating module and the lower chamber wall of the vacuum chamber and spaced apart from the lower chamber wall by a distance.

6. The vacuum chamber heating apparatus for a vacuum reflow oven of claim 1, wherein a mirror reflector is further disposed above each set of radiant heating modules, and the mirror reflector is configured with a mirror surface for reflecting the light emitted from the lamp tube set to the upper chamber wall of the vacuum chamber.

7. The vacuum chamber heating apparatus for a vacuum reflow oven of claim 1, wherein an upper surface of each of the radiant tubes located on an upper chamber wall of the vacuum chamber is coated with a reflective coating that directs a downward reflection of heat from the radiant tubes.

8. The heating apparatus for vacuum chamber of vacuum reflow oven of claim 1, wherein the lower chamber wall of the vacuum chamber further has at least two sets of independently controlled radiation heating modules arranged in sequence, the radiation heating modules located on the lower chamber wall and the radiation heating modules located on the upper chamber wall are staggered or arranged in an up-down equal manner.

9. The heating apparatus of claim 8, wherein the lower surface of each radiant tube of the radiant heating module disposed on the lower wall of the vacuum chamber is coated with a reflective coating, the reflective coating reflecting the heat of the radiant tube upwards; and

and a second mirror reflector is also arranged below each group of radiant heating modules on the lower cavity wall and is used for reflecting light rays emitted by the lamp tube group on the lower cavity wall to the mirror surface on the lower cavity wall of the vacuum cavity.

10. A temperature control method for a vacuum chamber heating apparatus of a vacuum reflow oven according to any one of claims 1 to 9, comprising:

respectively setting the target temperature and the stable deviation of heating of each group of radiation heating modules;

each group of radiation heating modules starts heating, and the thermocouples of each group of radiation heating modules detect the temperature in real time;

judging whether the detection temperature of the thermocouple is higher than a set threshold value;

if the temperature is higher than the set threshold value, the alarm gives an over-temperature alarm and cuts off the heating power supply;

if the temperature value is not higher than the set threshold value, the temperature controller receives the current temperature value collected by each thermocouple, performs PID calculation on the detected temperature value and the preset target temperature and generates a control signal: if the difference value between the current temperature value and the set target temperature is greater than or equal to the stable deviation, judging that the current heating temperature of the radiation heating module corresponding to the thermocouple is too high, and further sending a control signal to the power regulator to quickly reduce the heating temperature to the preset target temperature; if the difference value between the current temperature value and the set target temperature is smaller than the stability deviation, the current heating temperature of the radiation heating module corresponding to the thermocouple is judged to be too low, and then a control signal is sent to the power regulator, so that the heating temperature is quickly increased to the preset target temperature.

Images