WO2001055686A9

WO2001055686A9 - Method and apparatus for measuring and collecting temperature data from a thermal processor

Info

Publication number: WO2001055686A9
Application number: PCT/US2001/003282
Authority: WO
Inventors: Philip C Kazmierowicz
Original assignee: Kic Thermal Profiling Inc
Priority date: 2000-01-31
Filing date: 2001-01-31
Publication date: 2002-10-17
Also published as: WO2001055686A1

Abstract

A method for measuring and collecting temperature data from a thermal processor utilizes a self-contained probe placed in the thermal processor. During the thermal process, temperature data are recorded in a memory. After the probe exits the thermal processor, these data are transmitted by wireless from the memory to a remote data acquisition device. The probe features one or more temperature sensor connections, a memory, a transmitter and a detector for transmitting the contents of the memory in response to a query signal or exit of probe from the thermal process.

Description

S P E C I F I C A T I O N

TITLE OF THE INVENTION

METHOD AND APPARATUS FOR MEASURING AND COLLECTING

TEMPERATURE DATA FROM A THERMAL PROCESSOR

FIELD OF THE INVENTION The present invention relates to temperature probes and methods for measuring and collecting thermocouple data in a thermal processor.

BACKGROUND OF THE INVENTION Thermal processing involves a series of procedures by which an item is exposed to a temperature-controlled environment. Thermal processes are used in a variety of manufacturing procedures such as heat treating, quenching and refrigerated storage. One example of a thermal processor is a reflow oven. The production of various goods such as electronic circuit boards in solder reflow ovens frequently entails carefully controlled exposure of the goods to heating and/or cooling environments for specific periods. The elevated temperature conditions needed to solder component leads onto printed circuit boards must be gradually and uniformly applied to minimize thermal expansion stresses. For this reason, convection heat transfer may be employed in these solder "reflow" operations. The connecting solder paste incorporates an amalgam of substances that must undergo phase changes at separate temperature levels. Solder reflow may be performed by sequentially passing a part (such as a printed circuit board to become a processed product) through a series of thermally isolated adjacent regions or "zones" in the reflow oven, the temperature of each being independently controlled. The part may be placed on a conveyor, which moves the part into the reflow oven entrance, sequentially through the zones, and out of the oven through the exit.

The temperature response of the part may be monitored by instrumenting the part or adjacent device with one or more thermocouples (or other temperature measuring contact devices such as thermisters or resistance temperature detectors) prior to sending the part into the reflow oven, or by remote observation with a thermal sensor. The temperature adjacent to the part (for example, along the conveyor) may also be measured by different means. Two examples are a probe having at least one

1 ₍ thermocouple conveyed so as to move along with the part, and a fixed probe extending along the length of the oven and positioned adjacent to the conveyor having a plurality of thermocouples disposed along the probe interior. Probes corresponding to these two configurations are available as SlimKIC™ Thermal Profiler and Prophet™ Thermal Manager, respectively, both available from KIC Thermal Profiling of San ι , Diego, California. These commercially available probe designs are compatible with types K and J thermocouples, both well known in the art.

The thermocouple measurements can be sent to a data acquisition device, such as a personal computer (PC) or equivalent device having appropriate software, through an attachable cable or by a conventional wireless link. The SlimKIC probe can pass

2_| temperature data to the PC in a "real-time" mode during the thermal profile period while the probe is being conveyed through the thermal processor. Alternatively, the SlimKIC probe can record the temperature data in a "data-logging" mode during the thermal process. Afterwards, the recorded data may be extracted by establishing a cable connection from the PC to the probe.

2 The real-time mode may be accomplished either by wireless communication or through a cable link (such as RS-232) physically attached to the SlimKIC. Using wireless communication (UHF radio, for example), a receiver may be connected to the serial port of the PC, and the SlimKIC transmitter transmits the data contemporaneously with the thermal process, (i.e., as temperature data are measured in the thermal processor). In the data-logging mode, the temperature data are recorded on an internal memory of the probe and downloaded after the thermal process has been completed.

A typical conventional telemetering system known to those of ordinary skill in the art includes a measuring sensor called a transducer, a medium of transmission (such as radio or light waves), equipment for receiving and processing the signal, and ₍ recording or display equipment. The transducer converts the physical stimulus to be measured into a corresponding electrical signal. In the case of temperature, the Seebeck effect is used to create an electromotive force. A thermocouple is calibrated to provide a unique measurable electrical response to a particular temperature over a specified range.

, A telemetry system ordinarily may handle more than one channel of information simultaneously by multiplexing a plurality of channels of data into a single composite signal for transmission over the communication link. The receiver at the data acquisition system extracts the signal and renders the signal in intelligible form. , The real-time mode has the advantage of verifying the connections for the thermocouples, ensuring voltage adequacy of the battery (e.g., 9-volt alkaline) used to power the untethered probe, monitoring the profile response during the thermal process, and determining whether the probe's internal temperature is within its operational range. A poor thermocouple connection may yield an open or short- circuit, which pegs the measurement reading. A weak battery suggests that the probe may fail to continue recording or transmitting temperature data during the thermal process, meaning the battery should be replaced. In the event that a part remains in the thermal processor for an extended period (such as the conveyor being interrupted), the probe may continue to transmit temperature data from the part or adjacent region. Following a thermal process, the probe may have absorbed sufficient thermal energy to bias temperature data. The real-time mode enables an operator to determine when the probe has sufficiently cooled before reusing in the thermal processor. The realtime mode has the additional advantage of eliminating the need to connect a cable to the probe after the latter has become untouchably warm from thermal exposure.

The disadvantage of the real-time transmitting mode is that the received signal to the PC may be garbled during portions of the profile due to electro-magnetic interference or signal shielding, causing data dropouts for those portions of the thermal profile where the reception has been interrupted. Repositioning the receiver attached to the PC and rerunning the thermal profile may become an expensive undertaking, or may be constrained by the space available where the thermal processor is contained. A disadvantage of the real-time cable mode is that some thermal processing environments complicate the reliability and/or reusability of the cable and/or its harness. Hence this mode may not be appropriate or cost-effective for such applications.

The data-logging mode has the advantage of recording data that after the thermal process become available to the PC without gaps from transmission garbling. However, the feedback of information prior to or contemporaneous with the thermal profile may not be available in the data-logging mode. Post-test discovery of a weak battery or a poorly connected thermocouple may necessitate repeating the thermal profile measurement, with the attendant costs thereof. In addition, an operator may be reluctant to immediately handle a heated probe for the purpose of inserting a cable with which to download the data to the PC. Furthermore, some thermal processes involve such high temperature conditions that the probe may be required to be encased in a thermal insulator package. Removing a probe from such a package, designed for protecting temperature-sensitive equipment, can be a time-consuming and unpleasant chore. Therefore, a method and apparatus to limit the data loss from real-time transmission from an untethered probe would be desirable in the thermal processing industry.

SUMMARY OF THE INVENTION A method for measuring and collecting temperature data from a thermal processor utilizes a self-contained probe placed in the thermal processor. During the thermal process, temperature data are recorded in a memory. After the probe exits the thermal processor, these data are transmitted by wireless from the memory to a remote data acquisition device. The probe features one or more temperature sensor connections, a memory, a transmitter and a detector for transmitting the contents of the memory in response to a query signal or exit of probe from the thermal process.

BRIEF DESCRIPTION OF THE FIGURES FIG. 1 is a block diagram of a temperature probe in accordance with a specific embodiment of the present invention.

FIG. 2 A is a front perspective diagram of a temperature probe used on a thermal processor in accordance with a specific embodiment of the present invention. FIG. 2B is a front perspective diagram of a temperature probe used on a thermal processor in accordance with an alternate embodiment of the present invention.

FIG. 3 is a flowchart of the temperature measuring, recording and transmitting sequence procedure in accordance with a specific embodiment of the present invention.

FIG. 4 is a flowchart of the thermocouple response sequence logic in accordance with a specific embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Those of ordinary skill in the art will realize that the following description of the present invention is illustrative only and not in any way limiting. Other embodiments of the invention will readily suggest themselves to such skilled persons having the benefit of this disclosure.

In accordance with a specific embodiment of the present invention, the components, process steps, and/or data structures may be implemented using various types of operating systems, computing platforms, computer programs, and/or general purpose machines. In addition, those of ordinary skill in the art will readily recognize that devices of a less general purpose nature, such as hardwired devices, or the like, may also be used without departing from the scope and spirit of the inventive concepts disclosed herewith.

The present invention is directed to a method and apparatus for measuring and collecting temperature data from a thermal processor so as to collect the data during the thermal process and transmit the data after the thermal process is completed. In an alternative embodiment, the method and apparatus may also include transmission of the data during the thermal process contemporaneously with the recording of the data, followed by retransmission of the data after the thermal process has been completed. FIG. 1 is a block diagram illustrating a probe in accordance with a specific embodiment of the present invention. A probe 10 may include a battery 12 to provide direct current electrical power, a switch 14 to activate the probe components so that power may be supplied from battery 12, a recorder/player 16 connected to a memory 18, a wireless transmitter 20 and a serial port 22. The probe 10 may be encased in a sheath 24 and optionally have thermal protection material 26 inserted between the inner wall of the sheath 24 and the internal components to protect the latter from high temperature exposure. The sheath 24 may be composed material resistant to high temperature and/or chemically reactive atmospheres, as are well known in the art.

The thermal protection material 26 may be selected to have low thermal conductivity. Alternatively for a probe requiring minimal volume, the thermal protection material 26 may be a heat sink composed of a material having a high heat capacity per volume. For longer exposures, a phase-change heat exchanger may encase the probe. A water jacket may increase the exposure time by steam venting. For very high temperature conditions, the probe 10 may be enclosed in a thermally insulated container, exposing only the thermocouple 32 to the oven environment. The probe may be controlled by a processor 28 that runs a program 30 to provide sequential instructions in software to selected components. The processor 28 may write the data to memory 18, obviating the necessity of a dedicated recorder/player 16. The processor 28 may also serve as a multiplexer for combining • data from several channels (e.g., connected to a plurality of thermocouples) into a single pulse for signal transmission via transmitter 20.

The probe 10 has a connection for at least one temperature sensor, such as a thermocouple 32, or a plurality of thermocouples arranged in a desired pattern, that supply the temperature measurement data. The probe may also incorporate a receiver 34 for receiving remote instructions by wireless transmission. The transmitter 20 and receiver 34 may be combined in a single device. The direct current electrical power may be transmitted by current-conducting wires 36 or printed circuit board traces. The thermocouple data may be sent to various devices by data communication conduits 38, while signals from processor 28 may be sent via instruction communication conduits 40. The probe 10 is shown in FIG. 2A in conjunction with a conveyorized thermal processor 42. The probe 10 may be placed on conveyor 44 to measure a temperature profile of the thermal process in the thermal processor 42. The switch 14 may be physically activated immediately prior to the probe being placed on the conveyor 44, or alternatively activated by a signal sent by a PC 46 serving as a data acquisition device and intercepted by the probe's receiver 34. The probe 10 may be carried through the entrance 48 by the conveyor 44. The thermocouple 32, connected to the probe 10, measures the temperature in the thermal processor 42 as the probe is conveyed. The temperature measurements may be stored by the recorder 16 in memory 18. Optionally, the temperature measurements may also be transmitted to the PC 46 from the transmitter 20. The probe 10 may proceed along the conveyor 44 in the direction 50 and through the exit 52.

In contrast to a conveyorized reflow oven 42, a batch oven 54, shown in FIG. 2B, may have a closeable aperture 56 that serves as both an entrance and an exit. In the batch oven operation, the probe 10 may be inserted into the batch oven 54 through the aperture 56 and stationed on a platform 58 for the data measurement and/or collection. The collected temperature data may be transmitted to the PC 46 upon completion of the thermal process and removal of the probe 10 from the batch oven 54.

After completing the thermal profile, the recorded temperature data may be transmitted to the PC 46 by the wireless transmitter 20. This procedure provides redundancy for data processing in the event that data reception by the PC 46 during the thermal process was incomplete or compromised. This redundancy may be provided by repeating the transmission of the data stored in memory 18. The transmission may be repeated in a continuous loop until the power to the probe may be discontinued by turning off the switch 14, or an instruction to that effect has been received by the processor 28. An example instruction may be a time-out switch that discontinues the transmission after a specified period has elapsed after transmission has begun. FIG. 3 provides a flowchart showing the general process for the method of the present invention that combines the real-time transmitting mode and the data-logging mode so as to provide all the advantages of both modes. The process starts with an initialization step 60 to begin a thermal process. The probe 10 may, for example, be placed on a conveyor 44 in step 62 and conveyed through the thermal processor oven 42 in step 64. During the thermal process, the probe 10 receives measured temperature data from the thermocouple 32 in step 66 and records the temperature data onto memory 18 in step 68. Optionally, the probe 10 may also transmit the temperature data in step 70 to be received by a data acquisition device, such as PC 46. These operations continue until after the probe 10 exits from the oven 42 and the thermal process has been completed in step 72. Then, while the probe 10 maintains electrical power and assuming no discontinue command is given in step 74, the recorded temperature data are wirelessly transmitted from the memory via the transmitter in step 76. If a termination command is provided or power is turned off, the process discontinues in step 78.

FIG. 4 provides a flowchart showing the states based on temperature triggers for a specific embodiment of the present invention. The logic inequalities contained therein assume that a heating oven represents the thermal processor in which the temperature of the thermal process may be higher than the initial ambient temperature. For a cooling thermal processor, these inequalities would be reversed from those discussed below. In the former case, the thermocouples must be sufficiently cool prior to being placed in the oven in order to accurately measure the temperature rise from ambient to the oven conditions to which a part may be exposed. Step 62 of placing the probe on the conveyor includes a sequencing step 82 of querying the value of each thermocouple from = 1, ..., n (from a multiplexed plurality of n thermocouples) in a logical loop until all of the measured thermocouple temperatures 1} read below a beginning trigger temperature value _beg.

In the example provided, step 84 interrogates each thermocouple measurement to ensure that all thermocouples satisfy are below T_beg before continuing. If any thermocouple measurement does not satisfy the 7 < r_beg condition, the measurements are continued (before the probe enters the oven) through the loop in step 82 until the thermocouples have cooled down sufficiently so that each thermocouple has reached the desired initial condition. This enables the recording of data to begin for the thermal profile and produces a first state for the thermocouple measurement. Once the initialization condition in step 84 has been satisfied, the probe may be conveyed through the oven in step 64. The process proceeds to step 86, which loops each thermocouple until any thermocouple exceeds the beginning temperature, expressed as T_t > T_heg in the query of step 88. When any thermocouple temperature satisfies this condition, the thermocouple measurement reaches a second state, and the procedure continues to step 90, which loops each thermocouple until each thermocouple exceeds a midpoint temperature, r^. In the example provided, step 92 interrogates each thermocouple to insure that all thermocouples satisfy T_t > T„_ύA. Satisfaction of this midpoint condition may enable the thermocouple measurement to reach a third state from which termination of the thermal process may be determined. Upon satisfaction of the midpoint condition, the process continues to step 94, through the probe exit step 74. In step 94, the end condition query is looped for each thermocouple until all thermocouples have cooled down below an end temperature, _end as an end condition. The query of step 96 may ask if all T_t < _en , any failure of which causes the loop in step 94 to resume. Once each thermocouple has cooled to the extent to satisfy the end condition and establish a fourth state, the thermal process may be considered completed. The beginning, midpoint and end temperatures may be selected based on the anticipated thermal process set-point profile. The selection of temperature values for these parameters lies outside the scope of the present invention.

Subsequently, the thermocouple data, recorded internally in the probe, may be transmitted (or retransmitted) in step 98 for each thermocouple within each time interval during which thermal profile data were measured, and for the entire period of the thermal profile. This transmission step 98 may be repeated until a stop or off condition asked in query step 100 has been satisfied, at which time the transmission ceases in step 102 and the state sequencing process terminates in step 104. In an alternate embodiment of the present invention, the logical sequence based on temperature triggers may be replaced by a time-elapse trigger. This arrangement enables the transmission to commence after a preselected time from power activation. The alternate embodiment envisions simple processes with limited operational flexibility. While embodiments and applications of the invention have been shown and described, it would be apparent to those of ordinary skill in the art, having the benefit of this disclosure that many more modifications than mentioned above are possible without departing from the inventive concepts herein. The invention, therefore, is not to be restricted except in the spirit of the appended claims.

Claims

CLAIMS What is claimed is:

1. A method for measuring and collecting temperature data from a thermal processor by a self-contained probe, said thermal processor having an entrance, an exit and a conveyor coupling said entrance and said exit, said probe having a memory coupled to a temperature sensor and a transmitter coupled to said memory, said method comprising: placing the probe at the entrance of the thermal processor; activating the probe; conveying the probe from the entrance to the exit of the thermal processor; acquiring temperature data from the sensor during said conveying; storing temperature data in the memory; and causing the transmitter to wirelessly transmit temperature data stored in the memory to a data acquisition device apart from the probe after the probe leaves the exit of the thermal processor.

2. A method according to claim 1 further wherein: said conveying further comprises: determining that temperature data from the sensor read a measured value that corresponds to below a start temperature to produce a first state, determining that temperature data from the sensor read a measured value that corresponds to above said start temperature to produce a second state; said acquiring further comprises: determining that temperature data from the sensor read a measured value that corresponds to above a midpoint temperature to produce a third state; and said causing the transmitter to transmit further includes: determining that temperature data from the sensor read a measured value that corresponds to above a stop temperature to produce a fourth state, transmitting repeatedly temperature data in said memory from said start sector to said end sector, and terminating said transmitting repeatedly after the probe receives a termination command.

3. A method according to claim 2 wherein said termination command is a time-out switch.

4. A method according to claim 2 wherein said termination command is transmitted from a remote device.

5. A method according to claim 1 wherein said causing the transmitter to wirelessly transmit further includes a time-elapse trigger after activating the probe.

6. A method for measuring and collecting temperature data from a thermal processor by a self-contained probe, said probe having a memory coupled to a temperature sensor and a transmitter coupled to said memory, said method comprising: activating the probe; placing the probe in the thermal processor; acquiring temperature data from the sensor; storing temperature data in the memory; removing the probe from the thermal processor; and causing the transmitter to wirelessly transmit temperature data stored in the memory to a data acquisition device apart from the probe.

7. A method according to claim 6 wherein said placing a self-contained probe in the thermal processor and removing said probe from the thermal processor are performed by conveying said probe through the thermal processor on a conveyor.

8. A method for measuring and collecting temperature data from a thermal processor by a self-contained probe, said thermal processor having an entrance, an exit and a conveyor coupling said entrance and said exit, said probe having a memory coupled to a temperature sensor and a transmitter coupled to said memory, said method comprising: placing the probe at the entrance of the thermal processor; activating the probe; conveying the probe from the entrance to the exit of the thermal processor; acquiring temperature data from the sensor during said conveying; wirelessly transmitting temperature data by the transmitter to a data acquisition device; storing temperature data in the memory; and causing the transmitter to wirelessly retransmit temperature data stored in the memory to said data acquisition device after the probe leaves the exit.

9. A method according to claim 8 further wherein: said conveying further comprises: determining that temperature data from the sensor read a measureo value that corresponds to below a start temperature to produce a first state, determining that temperature data from the sensor read a measured value that corresponds to above said start temperature to produce a second state; said acquiring further comprises: determining that temperature data from the sensor read a measured value that corresponds to above a midpoint temperature to produce a third state; and said causing further comprises: determining that temperature data from the sensor read a measured value that corresponds to above a stop temperature to produce a fourth state, wirelessly transmitting temperature data repeatedly in said memory from said start sector to said end sector, and terminating said wirelessly transmitting after the probe receives a termination command.

10. A method according to claim 8 wherein said causing the transmitter to wirelessly retransmit further includes a time-elapse trigger after activating the probe.

11. A self-contained probe for measuring and- collecting temperature data from an attached sensor in a thermal processor, said thermal processor having an entrance, an exit, and a conveyor coupled to said entrance and said exit, said probe comprising: a receiver for receiving temperature data from the sensor; a memory for storing temperature data; a transmitter for wirelessly transmitting data to a data acquisition device, wherein said transmitter is coupled to said memory; and a processor for controlling acquisition of temperature data, storage of temperature data in said memory while the probe is conveyed on the conveyor through the thermal processor, and wireless transmission of temperature data by said transmitter after the probe has been conveyed through the exit of the thermal processor.

12. A self-contained probe according to claim 11 wherein said transmitter receives and wirelessly transmits temperature data to said data acquisition device while the probe is conveyed through the thermal processor.

13. A self-contained probe according to claim 11 further comprising a device in said probe responsive to an external signal for causing said transmitter to transmit temperature data stored in said memory.

14. A self-contained probe for measuring and collecting temperature data from an attached sensor in a thermal processor, said probe comprising: a receiver for receiving temperature data from the sensor; a memory for storing temperature data; a transmitter for wirelessly transmitting data to a data acquisition device,, wherein said transmitter is coupled to said memory; and a processor for controlling acquisition of temperature data, storage of temperature data in said memory while the probe is inside the thermal processor and wireless transmission of temperature data by said transmitter after the probe has been removed from the thermal processor.