CN116648321A - Apparatus and method with closed loop IR camera heat detection system - Google Patents

Abstract

An apparatus configured for joining an electronic component to an electronic substrate, comprising: a chamber housing including a passageway extending through a plurality of processing regions; a conveyor configured to transport electronic substrates through the plurality of processing zones in the lane; and a heat detection system including at least one temperature sensor coupled to the chamber housing. The at least one temperature sensor is configured to detect a temperature of the electronic substrate passing in proximity to the at least one temperature sensor. The apparatus further includes a controller coupled to the plurality of processing zones, the conveyor, and the heat detection system. The controller is configured to receive temperature data from the heat detection system.

Description

Apparatus and method with closed loop IR camera heat detection system

Background

1. Technical field

The present application relates generally to surface mounting electronic components to printed circuit boards by employing an assembly process such as a reflow process, a wave soldering process, and/or a selective soldering process, and more particularly to an apparatus designed to control the amount of heat applied to the printed circuit board during the assembly process.

2. Background art

In the fabrication of printed circuit boards, electronic components are typically surface mounted to the bare circuit board by a process known as "reflow soldering". In a common reflow soldering process, a pattern of solder paste is deposited on a circuit board and then leads of one or more electronic components are inserted into the deposited solder paste. The circuit board is then conveyed through an oven where the solder paste is reflowed (i.e., heated to a melting or reflow temperature) in a heated zone and then cooled in a cooling zone to electrically and mechanically connect the leads of the electronic component to the circuit board. As used herein, the term "circuit board" or "printed circuit board" includes any type of substrate assembly having electronic components, including, for example, a wafer substrate.

As mentioned above, current reflow ovens have a heating chamber and a cooling chamber. In order to achieve a consistent reflow process profile, the heat applied to the electronic component and the circuit board is precisely controlled to ensure proper mechanical and electrical connection of the electronic component to the circuit board.

In addition, in the fabrication of printed circuit boards, electronic components may be mounted to the circuit board by a process known as "wave soldering". In a typical wave soldering machine, the circuit board is moved in an inclined path by a conveyor, through an upper flux station, a pre-heating station, and finally through a wave soldering station. At the wave soldering station, a wave of solder is caused to rush upward (by a pump) through a wave soldering nozzle and into contact with the portion of the printed circuit board to be soldered. As with reflow ovens, wave soldering machines (and selective soldering machines) require precise control of the heat of each zone to ensure proper mechanical and electrical connection of the electronic component to the circuit board.

For reflow ovens and wave (and selective) soldering machines, controlling the heat in the zones of the respective equipment is important to obtain optimal performance. For example, undesirable temperature variations may lead to warpage of the circuit board and unreliable connections between the electronic components and the circuit board.

Disclosure of Invention

One aspect of the present disclosure relates to a reflow oven configured for joining an electronic component to an electronic substrate. In one embodiment, the reflow oven includes: a chamber housing including a passageway extending through a plurality of processing regions; a conveyor configured to convey electronic substrates through the plurality of processing zones in the lane; and a heat detection system including at least one temperature sensor coupled to the chamber housing. The at least one temperature sensor is configured to detect a temperature of the electronic substrate passing in proximity to the at least one temperature sensor. The reflow oven further includes a controller coupled to the plurality of processing zones, the conveyor, and the heat detection system. The controller is configured to receive temperature data from the heat detection system.

Embodiments of the reflow oven may further include the at least one temperature sensor having at least one sensor assembly. The at least one sensor assembly may include a support structure, a support bracket coupled to the support structure, and an IR camera secured to the support bracket. The support structure may include a shroud mounted on the mounting plate. The shield may be configured to surround an opening in the top of the channel to enable the IR camera to sense the temperature of the channel. The support bracket may include a port to connect to an inert gas source. The support bracket may include a glass cover to protect the IR camera. The support bracket may be configured to mount the IR camera on top of the channel at a desired height and desired orientation to achieve a full field of view. The at least one sensor assembly may include a plurality of IR cameras to measure two or more individual locations within a selected location within the channel. The thermal detection system may be configured with a controller to provide closed loop control of the process zone temperatures of the plurality of process zones using the sensor assembly. The at least one sensor assembly may be configured to obtain temperature data at a particular electronic substrate height location and in certain processing zones of the reflow oven. The temperature data may be used to provide traceability of the electronic substrate, wherein data regarding a particular electronic substrate is provided on a display associated with the controller. The temperature data may be used to find hot spot areas/heights within the reflow oven. The temperature data may be used to optimize the performance of the reflow oven, and/or to provide downstream inputs to the processing equipment, and/or to determine the start and end times of scans performed by the at least one sensor assembly on the electronic substrate, and/or to generate electronic substrate curves above and below the electronic substrate. The closed loop control may include controlling the speed of the conveyor in the plurality of processing zones. Each of these electronic substrates may include a bar code scanned with a bar code scanner. The controller may be configured to implement a scan mode for measuring the temperature of components of the electronic substrates as they travel on the conveyor through the reflow oven.

Another aspect of the present disclosure relates to a method for bonding an electronic component to an electronic substrate in a reflow oven. In one embodiment, the method comprises: transporting the electronic substrate through a chamber housing including a passage extending through a plurality of processing zones; detecting a temperature of an electronic substrate passing in proximity to a thermal detection system comprising at least one temperature sensor coupled to the chamber housing; and receiving temperature data from the heat detection system by a controller coupled to the plurality of processing zones, the conveyor, and the heat detection system.

Embodiments of the method may further include scanning a bar code associated with each substrate with a bar code scanner, and/or controlling a reflow oven to implement a scanning mode to measure a temperature of components of the electronic substrate as the electronic substrate travels on a conveyor through the reflow oven. The heat detection system may be configured to provide closed loop control of the process zone temperatures of the plurality of process zones using the sensor assembly by the controller. The at least one sensor assembly may be configured to obtain temperature data at a particular electronic substrate height location and in certain processing zones of the reflow oven. The temperature data may be used to provide traceability of the electronic substrate, wherein data regarding a particular electronic substrate is provided on a display associated with the controller. The temperature data may be used to find hot spot areas/heights within the reflow oven. The temperature data may be used to optimize the performance of the reflow oven, and/or to provide downstream inputs to the processing equipment, and/or to determine the start and end times of scans performed by the at least one sensor assembly on the electronic substrate, and/or to generate electronic substrate curves above and below the electronic substrate. The closed loop control may include controlling the speed of the conveyor in the plurality of processing zones. The method may further comprise: a bar code associated with each substrate is scanned with a bar code scanner. The method may further include controlling the reflow oven to implement a scan mode to measure a temperature of the components of the electronic substrate as the electronic substrate travels on the conveyor through the reflow oven.

Yet another aspect of the present disclosure relates to a wave soldering machine or selective soldering machine configured for joining an electronic component to an electronic substrate. In one embodiment, the reflow oven includes: a chamber housing including a passageway extending through a plurality of processing regions; a conveyor configured to convey electronic substrates through the plurality of processing zones in the lane; and a heat detection system including at least one temperature sensor coupled to the chamber housing. The at least one temperature sensor is configured to detect a temperature of an electronic substrate passing in proximity to the at least one temperature sensor. The wave soldering machine or selective soldering machine further includes a controller coupled to the plurality of processing regions, the conveyor, and the heat detection system. The controller is configured to receive temperature data from the heat detection system. The at least one temperature sensor may comprise at least one sensor assembly. The at least one sensor assembly may include a support structure, a support bracket coupled to the support structure, and an IR camera secured to the support bracket. The support structure may include a mounting plate positioned on top of the channel and a shroud mounted on the mounting plate. The shield may be configured to surround an opening in the mounting plate to enable the IR camera to sense the temperature of the channel. The support bracket may include a port to connect to an inert gas source. The support bracket may include a glass cover to protect the IR camera. The support bracket may be configured to mount the IR camera on top of the channel at a desired height and desired orientation to achieve a full field of view. The at least one sensor assembly may include a plurality of IR cameras to measure two or more individual locations within a selected location within the channel. The thermal detection system may be configured with a controller to provide closed loop control of the process zone temperatures of the plurality of process zones using the at least one sensor assembly. The at least one sensor assembly may be configured to obtain temperature data at a particular electronic substrate height location and in certain processing zones of the reflow oven. The temperature data may be used to provide traceability of the electronic substrate, wherein data regarding a particular electronic substrate is provided on a display associated with the controller. The temperature data may be used to find hot spot/height within a wave soldering machine or a selective soldering machine. The temperature data may be used to optimize the performance of the wave soldering machine or the selective soldering machine, and/or to provide downstream input to the processing apparatus, and/or to determine the start and end times of a scan performed by the at least one sensor assembly on the electronic substrate, and/or to generate an electronic substrate curve above and below the electronic substrate. The closed loop control may include controlling the speed of the conveyor in the plurality of processing zones. Each of these electronic substrates may include a bar code scanned with a bar code scanner. The controller may be configured to implement a scan mode to measure a temperature of a component of the electronic substrate as the electronic substrate travels on the conveyor past the wave soldering machine or the selective soldering machine.

Another aspect of the present disclosure relates to a method for joining an electronic component to an electronic substrate in a wave soldering machine or a selective soldering machine. In one embodiment, the method comprises: transporting the electronic substrate through a chamber housing including a passage extending through a plurality of processing zones; detecting a temperature of an electronic substrate passing in proximity to a thermal detection system comprising at least one temperature sensor coupled to the chamber housing; and receiving temperature data from the heat detection system by a controller coupled to the plurality of processing zones, the conveyor, and the heat detection system.

Embodiments of the method may further include scanning a bar code associated with each substrate with a bar code scanner, and/or controlling the machine to implement a scanning mode to measure a temperature of a component of the electronic substrate as the electronic substrate travels on a conveyor past the machine. The thermal detection system may be configured with a controller to provide closed loop control of the process zone temperatures of the plurality of process zones using the sensor assembly. The at least one sensor assembly may be configured to obtain temperature data at a particular electronic substrate height location of the machine and in certain processing zones. The temperature data may be used to provide traceability of the electronic substrate, wherein data regarding a particular electronic substrate is provided on a display associated with the controller. The temperature data may be used to find hot spot/height within the machine. The temperature data may be used to optimize the performance of the machine, and/or to provide downstream inputs to the processing equipment, and/or to determine the start and end times of scans performed by the at least one sensor assembly on the electronic substrate, and/or to generate electronic substrate curves above and below the electronic substrate. The closed loop control may include controlling the speed of the conveyor in the plurality of processing zones.

Another aspect of the present disclosure relates to an apparatus configured for joining an electronic component to an electronic substrate. In one embodiment, the apparatus comprises: a chamber housing including a passageway extending through a plurality of processing regions; a conveyor configured to transport electronic substrates through the plurality of processing zones in the lane; and a heat detection system including at least one temperature sensor coupled to the chamber housing. The at least one temperature sensor is configured to detect a temperature of an electronic substrate passing in proximity to the at least one temperature sensor. The apparatus further includes a controller coupled to the plurality of processing zones, the conveyor, and the heat detection system. The controller is configured to receive temperature data from the heat detection system.

Yet another aspect of the present disclosure relates to a method for joining an electronic component to an electronic substrate in an apparatus. In one embodiment, the method comprises: transporting the electronic substrate through a chamber housing including a passage extending through a plurality of processing zones; detecting a temperature of an electronic substrate passing in proximity to a thermal detection system comprising at least one temperature sensor coupled to the chamber housing; and receiving temperature data from the heat detection system by a controller coupled to the plurality of processing zones, the conveyor, and the heat detection system.

Drawings

The figures are not intended to be drawn to scale. In the drawings, each identical or nearly identical component that is illustrated in various figures is represented by a like numeral. For purposes of clarity, not every component may be labeled in every drawing. In the drawings:

FIG. 1 is a perspective view of a reflow oven of an embodiment of the present disclosure;

FIG. 2 is a schematic view of the reflow oven shown in FIG. 1;

FIG. 3 is a perspective view of a portion of a reflow oven illustrating a heat detection system of an embodiment of the present disclosure;

FIG. 4 is a perspective view of an IR camera component of the heat detection system shown in FIG. 3;

FIG. 5 is a perspective view of an IR camera component mounted on the top wall of a tunnel of a reflow oven;

FIG. 6 is a perspective view of an IR camera mounted on a gantry of another embodiment of a heat detection system;

FIG. 7 is a schematic diagram of a wave soldering machine according to an embodiment of the present disclosure;

FIG. 8 is a side elevation view of the wave soldering machine with the housing removed to expose the internal components of the wave soldering machine;

FIG. 9 is a perspective view of an IR camera component of the heat detection system associated with the wave soldering machine;

fig. 10 is a perspective view of the IR camera assembly shown in fig. 9.

Detailed Description

Solder paste is commonly used in assembling printed circuit boards, where the solder paste is used to join electronic components to the circuit board. The solder paste includes a solder for forming a solder joint and a flux for finishing a metal surface for solder attachment. Any number of application methods may be used to deposit solder paste onto metal surfaces (e.g., electronic pads) disposed on the circuit board. In one example, a stencil printer may employ a wiper blade to force solder paste through a metal stencil laid over an exposed surface of a circuit board. In another example, the dispenser may dispense solder paste material onto specific areas of the circuit board. The leads of the electronic component are aligned with and pressed into the solder deposits to form an assembly. In a reflow soldering process, the solder is then heated to a temperature sufficient to melt the solder and cooled to permanently electrically and mechanically couple the electronic component to the circuit board. Solder typically comprises an alloy having a melting temperature lower than the melting temperature of the metal surfaces to be joined. The temperature must also be low enough so as not to damage the electronic components. In some embodiments, the solder may be a tin-lead alloy. However, a solder using a lead-free material may also be used.

The temperature control of the welding process is very important. In one embodiment of the present disclosure, a heat detection system with several Infrared (IR) cameras is used to accurately measure the temperature of a circuit board within a strategic location of a reflow oven. Information obtained from the IR camera of the heat detection system may be used to provide closed loop control of the reflow oven to ensure proper connection between the electronic components and the circuit board. Other types of temperature measurement devices may be employed instead of an IR camera. For example, a laser temperature sensor may be used as part of the heat detection system. Furthermore, the techniques described herein may be used with other types of circuit board processing equipment (such as wave soldering machines and selective soldering machines) to achieve better temperature control.

For the purpose of illustration only and not for the purpose of limiting the generality, the present disclosure will now be described in detail with reference to the drawings. The disclosure is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The principles set forth in this disclosure are capable of other embodiments and of being practiced or of being carried out in various ways. Also, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of "including," "comprising," "having," "containing," "involving," and variations thereof herein, is meant to encompass the items listed thereafter and equivalents thereof as well as additional items.

Reflow oven

In the reflow process, the circuit printed board is heated according to a predefined temperature profile for approximately 3-5 minutes. The complete assembly (including circuit board materials, components and solder paste) should reach a minimum reflow temperature, but should not overheat. Overheating may damage the components and cause welding defects. To achieve this heating profile, the reflow oven includes a plurality of heating zones and cooling zones. These zones blow hot or cold air towards the circuit board. The gas temperature set points of these zones in combination with the conveyor speed define the final heating profile of the circuit board assembly.

To ensure that the reflow oven is operating properly, the printed circuit board is provided with thermocouples to record the temperature of the circuit board over time. Thermocouples are placed on the coldest and hottest positions of the circuit board assembly and on critical components to ensure that the components do not overheat. Once the set point and conveyor speed are determined to be within acceptable standards, the oven contains controls and thermal probes to maintain the temperature of these zones within acceptable limits. During production, the circuit board with thermocouples is run through a reflow oven to ensure that all pre-defined conditions remain within acceptable standards. A disadvantage of the prior art process control is that there is no temperature control of the circuit board assembly during the reflow process. Inspection of the components and pads of the circuit board occurs after soldering; however, there is no verification during heating of the circuit board.

Existing process control aims at maintaining the temperature and conditions of the various zones within standard ranges using thermal probes that will measure the gas temperature but not the actual temperature on the circuit board assembly. Thermal profile control hardware is available with software tools to help define, measure, monitor and improve the thermal process of electronic manufacturing services. These systems make the reflow oven more intelligent and reduce defects due to better process control. The intelligent software will modify the oven settings as needed to ensure consistent circuit board temperatures and solder quality.

Although the reflow oven has intelligent systems and process control, the actual temperature of the circuit board assembly during soldering is not verified. Implementation of a thermal inspection system that can obtain thermal images of the circuit board assembly during reflow increases the value of process control, thereby preventing component damage and reducing soldering defects.

Embodiments of the present disclosure relate to a heat detection system having several IR camera components strategically positioned within a reflow oven to obtain closed loop temperature control of the oven. In one embodiment, the lens of the IR camera component is kept clean to enable accurate temperature images to be made. The IR camera assembly includes a special chamber in front of the lens into which nitrogen is purged to create an overpressure to avoid condensation of flux contaminated gas on the lens. Another method of maintaining a clean lens free of flux residue disclosed herein is to provide a transparent foil on a reel system in front of the lens. Once the foil becomes dirty, the roll will have a new clean transparent spot. In addition, the reflow oven may include a catalyst to clean the gases in these areas.

Embodiments of the thermal detection system include using thermal images as part of a closed loop system that controls the reflow process. The data from the thermal image is integrated into the intelligent control system of the reflow oven. The camera may be a 3D thermal camera or a normal 2D camera. The generated data (temperatures of different zones, components, solder paste and circuit board materials) can be used to obtain traceability and corrective action. The reflow process may have multiple cameras. Thermal image scanning is a snapshot of the reflow process. However, when multiple cameras are installed, a collection of snapshots may be used to calculate important process parameters, such as peak temperature and time above liquidus. The data may be associated with defect levels and precautions may be sent to the printer or dispenser or pick-and-place machine to make necessary modifications.

The image scan may also emit a deviation signal and the reflow oven may react accordingly. If the temperature is too low or too high, different actions may be taken, such as changing the conveyor speed or adjusting the fan speed of one or more heating zones to increase or decrease heat transfer. Other methods of temperature correction are to temporarily stop warming the circuit board or push the circuit board through the zone to achieve a shorter heating time when the circuit board is overheated. These small corrections require free space between the circuit boards. If the circuit board is too cold, an IR lamp may be installed in the area behind the scanner to heat a particular circuit board faster to bring it into compliance. The tracking system of the oven transport should track the position of the circuit board in the reflow oven for scanning at the correct moment. Typically, the conveyor has an encoder or other device that controls the speed and defines the position of the circuit board. In one embodiment, additional sensors may be mounted near the scanner to determine the position of the circuit board. The circuit board may be configured with a bar code, an RFID tag, or some other type of identification traceability.

Embodiments of the thermal inspection system are configured to obtain an image scan to show component alignment and analyze component movement defects during a reflow process. For example, if there are multiple scanners in the reflow oven, the location at which the component moves within the reflow oven may be defined, and this may help avoid such defects. Further actions may include changing fans or reducing fan speeds in specific areas of the oven.

Embodiments of the heat detection system are further configured to obtain a temperature profile of the circuit board at strategic points within the reflow oven. This is more accurate than thermocouple curve control that returns only the temperature of the probe. The position of the probe may not be the most critical point on the circuit board assembly, and the thermocouple attachment point is the critical point. The thermocouple may loosen after a certain number of runs; however, if the lens remains clean, the IR camera remains accurate over time and is not limited by the number of samples.

Fig. 1 illustrates one embodiment of an exemplary reflow soldering apparatus for soldering a circuit board assembly. Such equipment is sometimes referred to in the printed circuit board fabrication and assembly arts as reflow ovens or reflow soldering ovens. The reflow oven, generally indicated at 10 in fig. 1, includes a reflow oven chamber 12 in the form of an insulated tunnel defining a path for preheating, reflowing, and then cooling solder on a circuit board passing therethrough. The reflow oven chamber 12 extends across multiple heating zones, including in one example three preheating zones 14, 16, 18 followed by three soak zones 20, 22, 24, each of which includes a top heater 26 and a bottom heater 28, respectively. For example, the soak zones 20, 22, 24 are followed by four spike zones 30, 32, 34, 36, which also include heaters 26, 28. And finally, the spike zones 30, 32, 34, 36 are followed by three cooling zones 38, 40, 42. Other reflow oven configurations may be provided.

The circuit board assembly 44, including the deposited solder paste and electronic components, passes (e.g., left to right in fig. 1) on a constant speed conveyor (indicated by dashed line 46) through each zone of the insulated reflow oven chamber 12 to achieve controlled and gradual pre-heat, reflow, and post-reflow cooling of the circuit board assembly. It should be appreciated that the constant speed conveyor 46 may be split between these zones and implemented as a variable speed conveyor. In the preliminary preheating zones 14, 16, 18, the circuit board assembly is heated from ambient temperature to a flux activation temperature, which may range between about 130 ℃ to about 150 ℃ for lead-based solders and higher for lead-free solders.

In the soak zones 20, 22, 24, temperature variations across the circuit board assembly stabilize and provide time for activated flux to clean component leads, electronic pads, and solder powder prior to reflow. In addition, VOCs in the flux may vaporize. The temperature in the soaking zones 20, 22, 24 is typically about 140 ℃ to about 160 ℃ for lead-based solders and higher for lead-free solders. In some embodiments, the circuit board assembly may take about thirty to about forty-five seconds to traverse the soak zones 20, 22, 24.

In the spike regions 30, 32, 34, 36, the temperature is rapidly raised to a temperature above the melting point of the solder to reflow the solder. The melting point of eutectic or near-eutectic tin-lead solders is about 183 c, with the reflow spike typically set to about 25 c to about 50 c above the melting point to overcome the paste range of the molten solder. For lead-based solders, the peak area typically has a maximum temperature in the range of about 200 ℃ to about 220 ℃. Temperatures above about 225 ℃ may lead to solder flux burn, component damage, and/or sacrifice solder joint integrity. Temperatures below about 200 c may prevent complete reflow of the solder joints. In one embodiment, the circuit board assembly is maintained at a temperature above the reflow temperature for about one minute, typically within the spike zones 30, 32, 34, 36.

Next, in the cooling zones 38, 40, 42, the temperature drops below the reflow temperature and the circuit board assembly is cooled sufficiently to solidify the solder joints, thereby maintaining solder joint integrity before the circuit board assembly exits the reflow oven chamber 12.

A flux extraction/filtration system (not shown) may be provided to remove contaminant material from the gas generated by the reflow oven 10. In one embodiment, the input gas conduit may be connected to or between selected zones to provide fluid communication from the reflow oven chamber 12 to the flux extraction/filtration system. The output gas conduit may be connected to or between selected regions to provide fluid communication from the flux extraction/filtration system back to the reflow oven chamber 12. In operation, a vapor stream is drawn from the reflow oven chamber 12 through the input gas conduit, through the system, then through the output gas conduit, and back to the reflow oven chamber. Similar configurations of the input gas duct, the system, and the output gas duct may be similarly positioned to withdraw vapor streams from or between other areas of the reflow oven 10.

The reflow oven 10 further includes a controller 50 for automating the operation of the several stations of the reflow oven, including, but not limited to, the top and bottom heaters 26, 28 associated with the preheating zones 14, 16, 18, the soak zones 20, 22, 24, the spike zones 30, 32, 34, 36, and the cooling zones 38, 40, 42, in a well-known manner. As shown, the controller 50 may include a display 52 having a user interface in which an operator of the reflow soldering machine 10 may control the operation of the machine.

In one embodiment, the controller 50 may be configured to use a computer system having a suitable operating system (such as Microsoft Windows (R) offered by Microsoft corporationOperating system) having software specific to the application program to control the operation of the reflow oven 10. The controller 50 may be networked with a master controller that is used to control a production line for making circuit boards. As will be described in more detail below, the controller 50 may use information obtained by the heat detection system to optimize the performance of the reflow oven 10. Such optimization would include eliminating warpage and better and more reliable attachment of electronic components to the circuit board assembly.

Referring to fig. 3, the reflow oven 10 includes a heat detection system, indicated generally at 60, configured to detect heat within various regions of the oven. In the illustrated embodiment, the heat detection system 60 includes several (e.g., three) sensor assemblies, such as IR camera assemblies, each indicated generally at 62. In this example, the first IR camera assembly 62a is located between zones 3 and 4 (preheat and soak) of the reflow oven 10, the second IR camera assembly 62b is located between zones 6 and 7 (soak and spike), and the third IR camera assembly 62c is located between zones 9 and 10 (spike and cool). It should be appreciated that the IR camera assembly 62 may be deployed anywhere within the reflow oven 10 to optimize the performance of the reflow oven.

Each IR camera assembly 62 is strategically placed to measure the temperature of the circuit board assembly 44 as it passes between these zones, thereby ensuring that the circuit board assembly is properly conditioned prior to being processed. The information obtained from each IR camera assembly 62 is communicated to the controller 50, which is configured to provide closed loop processing of subsequent circuit board assemblies passing through the reflow oven 10.

With additional reference to fig. 4 and 5, for reflow solderingFor oven applications, each IR camera assembly 62 includes a shroud 64 mounted on a top wall 66 of the chamber 12 of the reflow oven 10. The shroud 64 is configured to extend through an opening formed in a top wall 66 of the chamber 12 to enable the IR camera assembly 62 to sense the temperature of the channel. The support structure further includes a support bracket 68 mounted on the shroud 64 on top of the shroud. The support bracket 68 includes a port 70 to connect to nitrogen (N ₂ ) A source to provide an inert atmosphere within the shroud 64. The support bracket 68 further includes an input port 72 to connect the sensor to the support bracket.

The IR camera assembly 62 further includes a temperature sensor embodying an IR camera 74 that is supported in an operative position by the support bracket 68. A cable 76 is secured to the input port 72 to connect the IR camera 74 to the controller 50. As described above, any type of temperature sensor may be employed to measure the temperature of the circuit board assembly traveling within the tunnel (chamber 12) of the reflow oven 10. The IR camera 74 is configured to have a field of view directed through the shroud 64 toward the passage (chamber 12) of the reflow oven 10. The arrangement is such that the IR camera 74 of the IR camera assembly 62 is configured to detect the temperature of the circuit board assembly traveling in the tunnel (chamber 12) of the reflow oven 10 and communicate this information to the controller 50. The data obtained from the heat detection system 60 may be used for a variety of purposes, as will be described in more detail below.

Referring to FIG. 6, an alternative embodiment of a sensor assembly is indicated generally at 80. As shown, the sensor assembly 80 includes a gantry 82 and a temperature sensor, represented as an IR camera 84, connected to the gantry and the controller 50. The arrangement is such that the stage 82 is configured to move the IR camera 84 along the width of the channel (chamber 12) under the control of the controller 50 to obtain temperature data across the width of the printed circuit board assembly as it passes through the reflow oven 10. The sensor assembly 80 further may include a shroud (not shown) to maintain the IR camera 84 in an inert (clean) atmosphere.

Wave crest welding machine

In a wave soldering process, there are several process steps. There is a flux step in which the printed circuit board assembly is cleaned by spraying flux to the soldering side (bottom) of the printed circuit board assembly. After the flux is applied, the printed board assembly is transported to a pre-heating unit. The preheating unit may represent a different concept, such as a convection or radiation heater. The goal is to heat the printed circuit board assembly to a predefined temperature, which is typically measured on the soldering target side (top side board). The flux is activated by the pre-heater and the circuit board assembly heats up so that the solder does not solidify before reaching the top side plate. The printed circuit board assembly enters the solder wave. The soldering process involves a heated solder bath that is maintained at a desired temperature during the soldering process. A solder wave is established within the slot and the printed circuit board assembly passes through the solder wave such that the bottom side of the circuit board assembly contacts the solder wave.

The temperature of the circuit board assembly during preheating is typically measured with a pyrometer. This is typically done after the circuit board assembly passes through the last pre-heating unit, just prior to entering the solder wave station. However, the pyrometer has a limited site such that the data covers only a small area of the entire circuit board.

Embodiments of a heat detection system with an IR camera can scan the entire printed circuit board assembly to obtain temperature data from the printed circuit board assembly.

Embodiments of the heat detection system include an IR camera after the last pre-heat unit for a wave soldering machine. The data provided by the IR camera may be used for closed loop process control. When the IR camera is mounted above the printed circuit board assembly in the pre-heating unit, the IR camera may provide information to modify the pre-heater of the unit in a manner such that the subsequent circuit board reaches a specified temperature before entering the wave soldering station. Thus, the printed circuit board assembly can reach an optimal temperature when the printed circuit board assembly is soldered, which minimizes the risk of defects. This data is recorded and combined with board identification (such as bar codes or RFID) and can be used to obtain traceability that may be related to defects during assembly or field failure.

Referring to fig. 7, an exemplary wave soldering machine, indicated generally at 100, is used to apply wave soldering to a printed circuit board assembly. As described above, the wave soldering machine 100 is one of several machines in a printed circuit board manufacturing/assembly line. As shown, the wave soldering machine 100 includes a housing or frame 102 adapted to house the components of the machine. This arrangement allows the conveyor 104 to deliver printed circuit board assemblies 44 to be processed by the wave soldering machine 100.

Upon entering the wave soldering machine 100, each circuit board assembly 44 travels along a conveyor 102 along an inclined path (e.g., six degrees relative to horizontal) through a tunnel 106, which includes an upper flux station, indicated generally at 108, and a pre-heating station, indicated generally at 110, to condition the printed circuit board assemblies for wave soldering. Once conditioned (i.e., heated), the circuit board assembly 44 travels along the conveyor 102 to a wave soldering station, generally indicated at 112, to apply solder to the printed circuit board assembly. The controller 114 is configured to automate the operation of several stations of the wave soldering machine 100, including but not limited to the upper flux station 108, the pre-heating station 110, and the wave soldering station 112, in a well known manner.

As with the controller 50 associated with the reflow oven 10, the controller 114 for the wave soldering machine 100 may be configured to use a computer system having a suitable operating system (such as Microsoft (R) offered by Microsoft corporationOperating system) having software specific to the application program to control the operation of the wave soldering machine. The controller 114 may be networked with a master controller that is used to control a production line that produces circuit boards. Similar to the reflow oven 10, the controller 114 may use information obtained by the heat detection system to optimize the performance of the wave soldering machine 100. Such optimization would include eliminating warpage and better and more reliable attachment of electronic components to the circuit board assembly.

Referring to fig. 8, the upper flux station 108 is configured to apply flux to the printed circuit board as the printed circuit board travels on the conveyor 104 through the wave soldering machine 100. The pre-heating station 110 includes a number of pre-heaters (e.g., pre-heaters 110a, 110b, and 110 c) that are designed to incrementally increase the temperature of the printed circuit board assembly as the printed circuit board assembly travels along the conveyor 104 through the channel 106 to prepare the printed circuit board assembly for the wave soldering process. The wave soldering station 112 includes a wave soldering nozzle assembly in fluid communication with a solder reservoir. A pump is disposed within the reservoir to deliver molten solder from the reservoir to the wave soldering nozzle assembly. Once soldered, the printed circuit board assembly exits the wave soldering machine 100 via conveyor 104 to another station (e.g., pick and place machine) disposed on the manufacturing line.

In some embodiments, the wave soldering machine 100 may further include a flux management system, generally indicated at 116, to remove volatile contaminants from the channels 106 of the wave soldering machine. As shown in fig. 2, the flux management system 116 is positioned below the preheating station 110. In one embodiment, the flux management system 116 is supported by the housing 102 within the wave soldering machine 100 and in fluid communication with the channel 106, which is schematically illustrated in fig. 2. The flux management system 116 is configured to receive the contaminated gas from the channels 106, process the gas, and return the cleaned gas to the channels. The flux management system 116 is particularly configured to remove volatile contaminants from the gas, particularly under an inert atmosphere.

Referring to fig. 9 and 10, the wave soldering machine 100 includes a heat detection system configured to detect heat within an area of the machine, such as between the pre-heating station 110 and the wave soldering station 112. The heat detection system includes a sensor assembly, shown generally at 120, that is embodied as an IR camera assembly that is strategically deployed to measure the temperature of the circuit board assembly 44 as it passes between the various zones to ensure that the circuit board assembly is properly conditioned prior to processing. Information obtained from the IR camera assembly 120 is sent to the controller 114, which is configured to provide closed loop processing of subsequent circuit board assemblies passing through the wave soldering machine 100.

For wave soldering machine applications, the IR camera assembly 120 includes a support structure having a mounting plate 122 positioned on top of the channel 106 of the wave soldering machine 100 and a shroud 124 mounted on the mounting plate. The shield 124Is configured to surround the opening in the mounting plate 122 to enable the IR camera assembly to sense the temperature of the channel 106. The support structure further includes a support bracket 126 mounted on the shroud 124 on top of the shroud. The support bracket 126 includes a port 128 to connect to nitrogen (N ₂ ) A source to provide an inert atmosphere within the shield. The support bracket 126 further includes an input port 130 to connect the sensor to the support bracket.

The IR camera assembly 120 further includes an IR camera 132 supported in an operative position by the support bracket 126. A cable 134 is secured to the input port 130 to connect the IR camera 132 to the controller 114. As described above, any type of temperature sensor may be employed to measure the temperature of the circuit board assembly within the channel 106 of the wave soldering machine 100. The IR camera 132 is configured to have a field of view directed through the shroud 124 toward the channel 106 of the wave soldering machine 100. The arrangement is such that the IR camera 132 of the IR camera assembly 120 is configured to detect the temperature of the circuit board assembly within the channel 106 of the wave soldering machine 100 and send this information to the controller 114.

Selective welding machine

In a selective welding process, there are several process steps. First, there is an upper flux station in which the printed circuit board assembly is cleaned by spraying flux to the soldering side (bottom) of the printed circuit board assembly. After the flux is applied, the printed board assembly is transported to a pre-heating unit. The pre-heating unit may be configured to include different heating concepts, such as convection or radiant heaters. The purpose of this process step is to heat the printed circuit board assembly to a predefined temperature, which is typically measured on the soldering target side (top) of the printed circuit board assembly. The flux is activated and the circuit board assembly heats up so that the solder does not solidify before the selective soldering process is performed. Prior to implementing the heat detection system of the present disclosure, the temperature of the printed circuit board assembly during preheating may be measured with a pyrometer to generate very limited thermal information about the printed circuit board assembly.

After preheating, the printed circuit board assembly is transported to a soldering area where one of two soldering processes may be performed. In one soldering process, solder is applied through a small solder nozzle configured for performing a point-to-point soldering process. In another soldering process, solder is applied through a multiwavelength plate, wherein the solder joint is made by one drop (dip).

Embodiments of the heat detection system may include an IR camera (2D or 3D) in a selective welding process. The camera provided data may be used for closed loop process control. When a camera is mounted over a printed circuit board assembly in a pre-heat process, temperature data obtained from the camera may provide information to modify the power of the unit in a manner such that a particular temperature is achieved when the selective soldering machine is ready to deliver a circuit board to a soldering station. Thus, the printed circuit board assembly can reach an optimal temperature when soldered, which minimizes the risk of defects. This data may be recorded and combined with circuit board identification (such as bar codes or RFID) and may be used to obtain traceability that may be related to defects during assembly or field failure.

An IR scanner may also be provided in the welding station. For the multi-peak dip process, a 2D or 3D camera may be configured to measure the temperature of the solder joint. Such a configuration may identify whether the solder solidifies (below the melting point) before the printed circuit board assembly is moved to avoid stress in the solder joint. Furthermore, this data can also be used for process optimization and traceability purposes.

For point-to-point soldering processes, an IR scanner disposed above the soldering station may be useful to record the condition of the printed circuit board assembly and verify that the temperature is within temperature tolerances. This information can be used to reduce defects and have better process control.

Other aspects of the thermal detection system

In some embodiments, the support bracket includes IR camera glass to protect the IR camera. In fig. 9, a lens 140 is provided to protect the IR camera 132. Although shown with respect to the IR camera assembly 120 of the wave soldering machine 100, it should be understood that a lens 140 or camera glass may also be provided for the IR camera assembly 62 associated with the reflow oven 10. Other types of materials may also be provided to form the protective cover. The IR camera glass is positioned such that pressurized air moves over the IR camera glass to form an "air curtain" preventing blockage of the IR camera. In one embodiment, a moving film may be provided to protect the IR camera.

Lens 140 may be applied to IR camera 74 associated with reflow oven 10.

In some embodiments, the shield may be configured to be connected to another inert fluid source.

In some embodiments, the shield may be configured to be a temperature controlled fluid source to protect the IR camera.

In some embodiments, the support bracket may be configured to mount the IR camera at a desired height and a desired orientation to achieve a full field of view. In the illustrated configuration, the IR camera is mounted on top of the tunnel of the reflow oven. However, the IR camera may be mounted on the side of the tunnel of the reflow oven. In the case of side mounting, mirrors may be employed to view the top and bottom of the circuit board through the channels.

In some embodiments, the IR camera may be mounted on a support structure that acts as a gantry to move the camera over the circuit board. The IR camera may be positioned inside or outside the tunnel of the reflow oven.

In some embodiments, the IR camera assembly may include a plurality of IR cameras to measure two or more separate locations within a selected location within the path of the reflow oven.

In some embodiments, a one-dimensional line scan camera may be used to detect circuit board temperature.

In some embodiments, a two-dimensional camera may be used to detect circuit board temperature.

In some embodiments, existing reflow ovens may be updated by retrofitting a kit (including components of the heat detection system including a plurality of IR camera components, such as mounting plates, shields, support brackets, nitrogen connections, IR camera cables, and IR cameras). Software upgrades may be provided to the controller of the reflow oven.

In some embodiments, the heat detection system is configured with a controller to provide closed loop control of zone temperature using an IR camera assembly or other temperature detection device. This closed loop control enables the operator to monitor the circuit board temperature and locate hot spots on the circuit board (top and bottom of the circuit board).

In some embodiments, the controller is configured with executable software that enables closed loop control of various areas of the reflow oven.

In some embodiments, information obtained from the thermal detection system is collected and analyzed for future actions.

In some embodiments, the IR camera component of the heat detection system is configured to obtain temperature data at specific board height locations and in certain areas of the reflow oven.

In some embodiments, the IR camera component of the heat detection system is configured to provide data to the controller for process control and/or to address equipment issues for downstream parameters associated with the production line.

In some embodiments, the printed circuit boards have bar codes that are scanned by a bar code scanner or other type of identification system to track the data of each circuit board.

In some embodiments, the IR camera component of the heat detection system is configured to obtain temperature data for use by the controller to provide closed loop localized heating to a desired circuit board area. Real-time zone-to-zone temperature adjustments may be made for purposes of circuit board temperature uniformity or desired temperature profile.

In some embodiments, the closed loop processing of the circuit board may include controlling the conveyor to control conveyor speed in one or more zones to optimize heat transfer. The fan blower speed may also be controlled. In one embodiment, the conveyor may include a plurality of sections corresponding to the plurality of zones, wherein each conveyor section is controlled by a controller to control the speed of the conveyor section and thus the temperature applied to the circuit board. By this configuration, local heating of the circuit board is achieved.

In some embodiments, the data obtained from the heat detection system may be used for a variety of purposes. For example, the data may be communicated to a customer. The data may be used to provide traceability of the circuit board, wherein the data about a particular circuit board is associated with a customer. The data may be used to find hot spot areas/heights within the reflow oven. The data may be used to optimize the performance of the reflow oven. The data may be used to provide downstream inputs to the processing device. The data may be used to determine the start and end times for the IR camera component to perform a scan on the circuit board. The data may be used to generate circuit board curves above and below the circuit board to determine certain board areas or heights. The client may use the data for other analysis and store the data in a client server/network or cloud.

In some embodiments, the controller may be configured to implement a scan mode to measure the temperature of all circuit board components as the circuit board travels on the conveyor through the reflow oven.

In some embodiments, the thermal detection system is configured for thermal imaging during moire analysis (strain/stress analysis) to correlate temperature hot spots with warp responses.

In some embodiments, the heat detection system is configured to find hot and cold spots during reflow soldering, wave soldering, SRT rework, and selective soldering.

In some embodiments, a thermal detection system may be used to provide analysis to improve circuit board design and functionality.

In some embodiments, a heat detection system may be used to reduce voids in the reflow process.

In some embodiments, the heat detection system enables enhanced temperature control to reduce defects.

In some embodiments, the heat detection system enables overall closed loop control of the zone temperature of the reflow oven by employing multiple Infrared (IR) camera assemblies at strategic locations to reduce warpage, identify hot spots, determine component overheating, obtain curve verification, and reduce porosity.

In some embodiments, the heat detection system is configured to include an automatic sensing device with settings that self-adjust based on environmental conditions and the product being manufactured, thereby improving visibility, productivity, traceability, and response time while reducing costs.

In some embodiments, the thermal detection system enables visibility and normative real-time analysis through intelligence in the supply chain that can be used prospectively.

In some embodiments, the heat detection system increases flexibility by managing complexity within a closed loop system.

In some embodiments, connectivity is improved through an open architecture for developing standard or custom interfaces and data output. The architecture is configured to support a number of MEMS.

In some embodiments, automation is enhanced by providing automatic switching and consumable replenishment, thereby reducing operator error and human hands.

In some embodiments, the heat detection system is configured to achieve self-optimization by reducing operator intervention in machine parameters and providing closed-loop control, resulting in higher yields.

In some embodiments, maintenance is improved by applying predictive maintenance items based on actual needs of the reflow oven or wave soldering machine. And, improved maintenance replaces or reduces maintenance-based planning time.

In some embodiments, the controller associated with the reflow oven or wave soldering machine includes the following controllers: the controller is adapted to control the operation of the furnace or machine based on the operating parameters obtained by the controller. The controller may be configured to communicate with a controller associated with the production line. In one embodiment, the controller may be configured to communicate with another controller (e.g., a controller associated with a production line) via a Controller Area Network (CAN) bus or other type of network. In other embodiments, a master controller may be provided to control the operation of the controllers of the various parts of the equipment associated with the production line. The controller may include a display operatively coupled to the controller. The display is adapted to display operating parameters of the reflow oven or wave soldering machine such as, but not limited to, temperature data for various zones of the oven or machine, or data associated with the solder level of the machine. Suitable sensors may be provided to obtain such information. Alternatively or additionally to the previous embodiments, the operating parameters may be displayed on a display disposed within the reflow oven, a display disposed within the wave soldering machine, and/or a display associated with the manufacturing line.

In other embodiments, the material identification for an item (such as a circuit board) traveling through a reflow oven or wave soldering machine may include a means for manipulating the item and a scanner for scanning and identifying the item. For example, a reflow oven or wave soldering machine may be configured to include pinch rollers to rotate the circuit board to align a code or predetermined identification mark disposed on the circuit board with a scanner disposed on the oven or machine. The system is configured to associate a material identification associated with the circuit board with a recipe, production time, etc. for a reflow oven or wave soldering machine. In one embodiment, a bar code for identifying an item may be implemented. For example, the bar code may include a 1D scanner for UPC codes, a 2D scanner for QRC codes, printed indicia applied to the article, or laser etched indicia etched on the article. In another embodiment, an RFID system for identifying items may be implemented. For example, an RFID system may include an RFID tag applied to an item and an RFID reader associated with a reflow oven or wave soldering machine. In RFID systems, there is no need for a straight line pair between the reader and the item. In addition, scanning is not required to identify all items within the mobile cart. In another embodiment, an imaging or vision system for identifying an item may be implemented.

In some embodiments, a database is provided to track items processed through a reflow oven or wave soldering machine. In one embodiment, the database may include an open application (App) architecture and is configured to push data to a reflow oven or wave soldering machine. The oven or machine may be configured to communicate with the oven or machine to push/pull data to the oven or machine and/or the production line, or to communicate directly with the production line. The database may include job information or material information. The database may also be in communication with a Manufacturing Execution System (MES) associated with the production line, reflow oven, and/or wave soldering machine. The MES system can be configured to know which materials are needed for a production run. The movable cart can be configured to communicate with a MES system to adjust delivery of the items to a reflow oven or a wave soldering machine.

The database may also be configured to retrieve information about the item based on the identification (e.g., bar code number). In one embodiment, a central management system may be provided in which a reflow oven or wave soldering machine is programmed to accept material from a mobile cart. The reflow oven or wave soldering machine is programmed to update the database through a network that is associated with the MES system to process the circuit boards passing through the oven or machine.

The database may further be configured to store additional information such as temperature data, the number of circuit boards processed, and/or material consumption associated with a reflow oven or wave soldering machine. The database may be configured to store information locally or remotely, and may be configured to store data associated with one or more production runs.

The database may be configured to share forecast data when a new production run is envisaged or programmed. For example, with respect to storing information related to temperature processing efficiency, the database may be configured to perform one or more of the following: storing information about temperature zone data, the number and type of circuit boards processed when the paste consumable needs to be replenished; triggering an alarm and/or report; signaling inventory control systems associated with reflow ovens, wave soldering machines, and/or production lines; analyzing consumable usage based on the operating parameters and actual usage and upstream/downstream equipment activities; predicting replacement or maintenance; and correlating the plurality of sites to predict future production run parameters.

The database may be configured to store data associated with batch traceability. In addition, RFID or mechanical keying of the circuit board is provided to ensure proper alignment/orientation/back and forth/up and down when these items are inserted into a reflow oven or wave soldering machine for processing. A low cost reader can perform this function.

Having thus described several aspects of at least one embodiment of this disclosure, it is to be appreciated various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the spirit and scope of the disclosure. Accordingly, the foregoing description and drawings are by way of example only.

The claims.

Claims (20)

1. An apparatus configured for joining an electronic component to an electronic substrate, the apparatus comprising:

a chamber housing including a passageway extending through a plurality of processing regions;

a conveyor configured to transport electronic substrates through the plurality of processing zones in the lane;

a heat detection system comprising at least one temperature sensor coupled to the chamber housing, the at least one temperature sensor configured to detect a temperature of an electronic substrate passing in proximity to the at least one temperature sensor; and

a controller coupled to the plurality of processing zones, the conveyor, and the heat detection system, the controller configured to receive temperature data from the heat detection system.

2. The apparatus of claim 1, wherein the at least one temperature sensor comprises at least one sensor assembly.

3. The apparatus of claim 2, wherein the at least one sensor assembly comprises a support structure, a support bracket coupled to the support structure, and an IR camera secured to the support bracket.

4. The apparatus of claim 3, wherein the support structure comprises a shroud mounted on the mounting plate.

5. The apparatus of claim 4, wherein the shroud is configured to surround an opening in a top of the channel to enable the IR camera to sense a temperature of the channel.

6. The apparatus of claim 3, wherein the support structure comprises a mounting plate positioned on top of the channel and a shroud mounted on the mounting plate.

7. The apparatus of claim 6, wherein the shroud is configured to surround an opening in the mounting plate to enable the IR camera to sense the temperature of the channel.

8. The apparatus of claim 3, wherein the support bracket includes a port to connect to an inert gas source.

9. The apparatus of claim 3, wherein the support bracket comprises a glass cover to protect the IR camera.

10. The apparatus of claim 3, wherein the support bracket is configured to mount the IR camera on top of the channel at a desired height and a desired orientation to achieve a full field of view.

11. The apparatus of claim 1, wherein the at least one sensor assembly comprises a plurality of IR cameras to measure two or more individual locations within a selected location within the channel.

12. The apparatus of claim 1, wherein the heat detection system is configured with a controller to provide closed loop control of zone temperatures of the plurality of process zones using the sensor assembly.

13. The apparatus of claim 12, wherein the at least one sensor assembly is configured to obtain temperature data at a particular electronic substrate height location and in certain processing zones.

14. The apparatus of claim 13, wherein the temperature data is used to provide traceability of the electronic substrate, wherein the data regarding a particular electronic substrate is provided on a display associated with the controller.

15. The apparatus of claim 13, wherein temperature data is used to find hot spot/height within the chamber housing.

16. The apparatus of claim 13, wherein the temperature data is used to optimize performance of the apparatus, and/or to provide downstream input to the processing apparatus, and/or to determine start and end times of scans performed by the at least one sensor assembly on the electronic substrate, and/or to generate electronic substrate curves above and below the electronic substrate.

17. The apparatus of claim 12, wherein the closed loop control comprises controlling the speed of the conveyor in the plurality of processing zones.

18. The apparatus of claim 1, wherein the electronic substrates each comprise a bar code scanned with a bar code scanner.

19. The apparatus of claim 1, wherein the controller is configured to implement a scan mode to measure the temperature of components of the electronic substrates as they travel on the conveyor through the chamber housing.

20. A method for joining an electronic component to an electronic substrate in an apparatus, the method comprising:

transporting the electronic substrate through a chamber housing including a passage extending through a plurality of processing regions;

detecting a temperature of an electronic substrate passing in proximity to a thermal detection system comprising at least one temperature sensor coupled to the chamber housing; and

temperature data is received from the heat detection system by a controller coupled to the plurality of processing zones, the conveyor, and the heat detection system.