Method for connecting surface mounted electronic components to a circuit board

Abstract

To provide a method for connecting a surface-mount electronic component to a circuit board.SOLUTION: A method for connecting an electronic component to a circuit board is disclosed. Initially, a substrate and an electronic component with solder located therebetween are placed under a flashlamp. Multiple light pulses from the flashlamp are applied to the electronic component, the substrate and the solder until the solder reflows. During the application of the light pulses, the power of one of the light pulses from the flashlamp and a temperature of the electronic component are measured, the measured power is converted to radiant exposure, and, in response to the measured temperature of the electronic component, a duty cycle of a next light pulse is adjusted adaptively according to the radiant exposure of the one light pulse.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] (Technical field) This application relates generally to manufacturing methods, and more particularly to methods for connecting surface mount electronic components to circuit boards. [Background technology]

[0002] (background) Generally, electronic components can be connected to circuit boards via soldering. With the advent of surface mount technology and wave soldering, the need to manually solder electronic components onto circuit boards has, in most cases, been eliminated from a production standpoint.

[0003] Surface mount technology requires the use of solder paste, which has solder particles dispersed in an organic flux. The solder paste is selectively deposited on a circuit board, followed by the placement of the electronic components to be soldered. The circuit board is then placed in a reflow oven equipped with a conveyor. The reflow oven heats the solder paste, activating the flux in the solder paste, cleaning the surface, and melting the solder, causing it to reflow. The molten solder wets the surface and solidifies, thereby forming a good electrical and mechanical connection between the electronic components and the circuit board.

[0004] However, there are several constraints to the reflow process. Because the entire assembly must pass through a reflow oven, the entire circuit board and electronic components must be able to withstand the high temperatures required to reflow the solder paste. For standard SAC-305 solder paste, that temperature is approximately 217°C. Another constraint to the reflow process is the long time required to process the solder paste to allow the solder to reflow. Typically, this takes about 10 minutes, as the thermal profile of the reflow oven is carefully controlled and may include multiple predetermined steps of ramp-up, soak, and ramp-down temperature zones.

[0005] One solution to the high temperature requirement of the reflow process is to use a solder paste with a lower reflow temperature. Currently, such solder pastes tend to have lower thermal and mechanical performance compared to standard SAC-compatible solder pastes. Another solution to the high temperature requirement of the reflow process is to use a conductive adhesive instead of the solder paste. This allows processing at temperatures close to room temperature (25°C). As with low-temperature solder pastes, the mechanical and electrical robustness of the joint is sacrificed.

[0006] With the reflow process, energy is transferred to the electronic components, circuit board, and solder paste via convection, but this presents another problem. Shear from the air in the reflow oven can cause electronic components to be blown off the circuit board or to be misaligned before they are soldered to the circuit board. This is even more of a problem when electronic components are very small because their aerodynamic cross-section to weight ratio is greater.

[0007] An alternative approach to the reflow process is to use a laser. With this approach, a solid-state laser is directed onto the solder joints or electronic components, heating them and reflowing the solder without heating the entire circuit board. The laser process delivers a precise amount of power and energy to the solder joints, allowing the solder paste to reflow within approximately one second. However, the laser process is inherently serial in nature, and therefore the total amount of time required for circuit boards with many solder joints increases as the number of solder joints increases. In addition, the laser process requires alignment of the solder joints. This, in turn, requires either a machine vision system and / or careful alignment and programming of the location of each joint to be soldered. Furthermore, the laser process can suffer from beam non-uniformity, which can cause the electronic components to heat unevenly. This can result in weak solder joints, damage to other parts of the circuit board, or "tombstoning" of the electronic components.

[0008] Another alternative approach to the reflow process is to use a continuous light source, such as a tungsten filament or tungsten-halogen-based lamp. One problem with this approach is that it takes a finite amount of time, approximately 1 second, to turn the light source on or off. Unlike laser processes, continuous light sources cannot be modulated on the timescale of the thermal equilibrium time of solder paste deposition, which is typically less than approximately 100 milliseconds. This limitation hinders the ability to precisely control the power and energy profile deposited on the material being processed. This is especially true for exposures where the target material being processed is stationary during exposure. When the target material is being transported, a similar problem exists in that the ideal exposure is generally linked to the transport speed. Adjusting either the transport speed or the exposure level to ensure uniform thermal treatment of the material being processed cannot be done quickly enough relative to controlling the machine output.

[0009] As a result, it is desirable to provide an improved method for electrically and mechanically connecting surface mount electronic components to circuit boards. Summary of the Invention [Means for solving the problem]

[0010] (Summary of the Invention) In one embodiment, a substrate and an electronic component are placed under a flash lamp with solder positioned therebetween. Multiple light pulses from the flash lamp are applied to the electronic component, the substrate, and the solder until the solder reflows. During application of the light pulses, the power of one of the light pulses from the flash lamp and the temperature of the electronic component are measured, the measured power is converted to radiant exposure, and in response to the measured temperature of the electronic component, the duty cycle of the next light pulse is adaptively adjusted according to the radiant exposure of the one light pulse. The present invention provides, for example, the following items. (Item 1) 1. A method for connecting an electronic component to a substrate, the method comprising: placing the substrate under a flash lamp with the solder positioned between the electronic component and the substrate; applying a plurality of light pulses from the flash lamp to the electronic component, the solder, and the substrate until the solder reflows; During said application of light pulses, measuring the power of one of the light pulses from the flash lamp and converting the measured power into a radiation exposure value; measuring the temperature of the electronic components soldered on the board; adaptively adjusting a duty cycle of a subsequent light pulse according to the radiation exposure value of the one light pulse in response to the measured temperature of the electronic component; To do A method comprising: (Item 2) Item 10. The method of claim 1, wherein the power measurement is performed by using a photodiode. (Item 3) Item 3. The method of item 2, further comprising calibrating the photodiode to generate a calibration coefficient. (Item 4) 4. The method of claim 3, wherein the converting further comprises converting the measured power to the radiation exposure value using the calibration factor. (Item 5) Item 10. The method of claim 1, wherein the temperature measurement is performed by using an infrared (IR) camera. (Item 6) Item 10. The method of item 1, wherein adjusting the duty cycle is performed by changing the frequency of the light pulses. (Item 7) Item 10. The method of item 1, wherein adjusting the duty cycle is performed by changing the pulse length of the light pulses. (Item 8) Item 2. The method according to item 1, wherein the substrate is a circuit board. (Item 9) Item 10. The method according to item 1, wherein the substrate is a thermoplastic material having a maximum working temperature of less than 200°C. (Item 10) Item 10. The method of claim 1, wherein the solder is a thick film material having a thickness greater than 50 microns. (Item 11) Item 10. The method of item 1, further comprising transporting the electronic component during the application of the light pulses. (Item 12) Item 12. The method of item 11, further comprising synchronizing the speed of the transport of the electronic component with the frequency of the light pulses. (Item 13) 2. The method of claim 1, further comprising placing the electronic component in an environmentally controlled chamber prior to the application of the light pulse. (Item 14) 1. A system for connecting an electronic component to a substrate, the system comprising: A capacitor bank, a capacitor bank charging power supply for charging the capacitor bank; an IGBT-based switching device; A frequency controller; a flash lamp for emitting light pulses, the flash lamp receiving charge from the capacitor bank via the IGBT-based switching device, the IGBT-based switching device being repeatedly switched on and off by the frequency controller to modulate the flow of charge from the capacitor bank to the flash lamp, which in turn switches the flash lamp on and off; a photodiode for measuring the power of the light pulse from the flash lamp; an infrared camera for measuring the temperature of electronic components soldered on the board; a processor, responsive to the measured temperature of the electronic component, for adaptively adjusting a duty cycle of a next light pulse via the frequency controller according to a radiant exposure resulting from the measured power of the light pulse from the flash lamp; A system comprising: (Item 15) Item 15. The system of item 14, further comprising a bolometer for calibrating the photodiode. (Item 16) Item 15. The system of item 14, wherein the capacitor bank includes a plurality of electrolytic capacitors. (Item 17) Item 15. The system of item 14, wherein the processor adjusts the duty cycle of the light pulses by changing the frequency of the light pulses via the frequency controller. (Item 18) Item 15. The system of item 14, wherein the processor adjusts the duty cycle of the light pulses by changing the pulse length of the light pulses via the frequency controller. (Item 19) Item 15. The system of item 14, further comprising a conveyor for transporting electronic components and substrates being processed. (Item 20) Item 15. The system of item 14, further comprising an environmentally controlled chamber for containing the electronic components during the application of the light pulses.

[0011] All features and advantages of the present invention will become apparent in the following detailed written description. [Brief explanation of the drawings]

[0012] The invention itself, as well as its preferred mode of use, further objects and advantages, will best be understood by reference to the following detailed description of illustrative embodiments when read in conjunction with the accompanying drawings.

[0013] [Figure 1] FIG. 1 is an isometric view of a system for heat treating solder paste to connect surface mount electronic components to a circuit board, according to one embodiment. [Figure 2] FIG. 2 is a detailed block diagram of the system from FIG. 1, according to one embodiment. [Figure 3] FIG. 3 is a flow diagram of a method for connecting a surface mount electronic component to a circuit board. [Figure 4] FIG. 4 graphically illustrates the flash lamp emission intensity versus wavelength at two different capacitor bank firing voltages. DETAILED DESCRIPTION OF THE INVENTION

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings, and in particular to FIG. 1 , an isometric view of a system for heat-treating solder paste to connect electronic components to circuit boards is depicted, according to one embodiment. As shown, system 100 includes an enclosure 110 that rests on an equipment rack 160. Enclosure 110 includes a hatch door 120 that can be lifted open via a handle 140. A semi-transparent window 130 is provided in hatch door 120 to allow a user to observe any processes occurring within enclosure 110. At least one flash lamp (not shown) is positioned within enclosure 110 to enable the heat treatment. A user can input information to and receive information from system 100 via touchscreen 150.

[0015] The enclosure 110 may include an environmentally controlled chamber (not shown), which may be filled with an inert gas (e.g., nitrogen) or a reactive gas (e.g., formic acid) or may be a vacuum, in which the heat treatment may be performed on the electronic components. Additionally, the enclosure 110 may include a conveyor (not shown) for transporting the electronic components during the heat treatment.

[0016] The various mechanical and electrical components configured to operate the system 100 may be contained within the equipment rack 160 .

[0017] Referring now to FIG. 2 , a block diagram of system 100 according to one embodiment is depicted. As shown, system 100 includes a capacitor bank charging power supply 210, a capacitor bank 220, an insulated gate barrier transistor (IGBT)-based switching device 230, a frequency controller 240, a flash lamp 250, a photodiode 260, an integrator 265, a bolometer 270, an infrared (IR) camera 280, and a computer 290. Computer 290 includes a processor and various storage devices known to those skilled in the art. The capacitors in capacitor bank 220 are, for example, electrolytic capacitors. Some of the above-mentioned components can be installed in equipment rack 160 (from FIG. 1 ).

[0018] Capacitor bank 220 can be charged by capacitor bank charging power supply 210. Then, charge from capacitor bank 220 is discharged into flash lamp 250 through IGBT-based switching device 230, which is repeatedly switched on and off by frequency controller 240 during discharge. Frequency controller 240 controls the gating of IGBT-based switching device 230 and thus the switching frequency of the discharge. The repeated on and off switching of IGBT-based switching device 230 is intended to modulate the flow of current from capacitor bank 220 to flash lamp 250 and thus switch flash lamp 250 on and off. In other words, the frequency or pulse length of the light pulses emitted by flash lamp 250 is dictated by frequency controller 240.

[0019] The photodiode 260 needs to be calibrated before the system 100 can be deployed to perform thermal processing. The photodiode 260 can be calibrated by using a bolometer 270 that is preferably National Institute of Standards and Technology (NIST) traceable. During calibration, both the photodiode 260 and the bolometer 270 are exposed to a single light pulse emitted from the flash lamp 250. The bolometer 270 measures the radiant exposure or energy per unit area (units: J / cm) of the single light pulse. 2 ), and photodiode 260 measures the instantaneous power (in W) of the same light pulse. The instantaneous power signal from photodiode 260 is then integrated by integrator 265 to provide a radiant exposure value for the same single light pulse, and the radiant exposure measurement from bolometer 270 is divided by this radiant exposure value from integrator 265 to generate a calibration factor as follows:

number

[0020] After calibration, the photodiode 260 / integrator 265 combination can be utilized to provide radiant exposure information for each light pulse emitted from flash lamp 250. Essentially, the radiant exposure information for a light pulse emitted from flash lamp 250 can be calculated by multiplying the output value of integrator 265 (the radiant exposure value for a light pulse emitted from flash lamp 250, formed by integrating the instantaneous power signal of the light pulse emitted from flash lamp 250 measured by photodiode 260) by a calibration coefficient obtained during calibration.

[0021] The reason for using photodiodes such as photodiode 260 to obtain radiant exposure information of light pulses from flash lamp 250 in system 100, even though photodiodes are technically designed to measure instantaneous power instead of radiant exposure, is that photodiodes are sufficiently reliable and small for placement adjacent to flash lamp 250 or for sampling light from small optical fibers that do not intercept the light pulses, have relatively high sample rates of over 1 MHz, and are also inexpensive.

[0022] However, as mentioned above, to employ a photodiode to obtain radiant exposure information of a light pulse from a flash lamp, the photodiode needs to be calibrated. One reason for calibration can be seen in Figure 4, which depicts the emission intensity from two flash lamp discharges of the same pulse length as a function of wavelength for two different capacitor bank voltages, namely, 300 V and 400 V. The light pulse emitted by the flash lamp is broadband, from about 250 nm to about 1,700 nm. The integral of the intensity over the emission range is expressed in W / cm. 2 The spectral emission distribution is proportional to the emitted power in units of . As the voltage increases, emission in all bands increases, but emission at shorter wavelengths increases more rapidly than at longer wavelengths. In other words, as the discharge voltage of the capacitor bank changes, the spectral emission distribution also changes. Unfortunately, photodiodes have sensitivity that varies across wavelength. Therefore, the direct output of a photodiode cannot give a quantitative power output from a flashlamp emission because the signal magnitude is a convolution of the photodiode sensitivity and the emission intensity, both of which vary across wavelength.

[0023] The calibration process described above is designed to improve the deficiencies of photodiodes. By using a bolometer, such as bolometer 270, and an integrator, such as integrator 265, the photodiode can be calibrated by integrating the power signal from a single pulse of light emitted from a flash lamp. In contrast to photodiodes, bolometers can measure the radiative exposure (total energy) emitted by a light pulse emitted from a flash lamp. This is primarily due to the fact that the radiation-sensing element has uniform sensitivity across the entire emission spectrum. Therefore, shifts in the flash lamp's emission spectrum do not affect the bolometer's ability to measure all the light that impinges upon it. However, the radiative exposure of a light pulse from a flash lamp cannot be measured solely using a bolometer. This is because the time response of a bolometer is very slow. A typical time resolution of a bolometer can be about 1 Hz, compared to a photodiode with a frequency of over 1 MHz. Additionally, bolometers are usually quite large, which obscures some of the light from the flash lamp.

[0024] Referring now to Figure 3, a flow diagram of a method for connecting electronic components to a circuit board is depicted, according to one embodiment. Beginning at 300, and as shown in block 310, a photodiode, such as photodiode 260 from Figure 2, is first calibrated by using a bolometer, such as bolometer 270 from Figure 2. Calibration is performed by using a single light pulse from a flash lamp, such as flash lamp 250 from Figure 2, to obtain a calibration factor, as described above. After calibration, the photodiode is ready to be employed to measure the radiant power of each light pulse emitted by the flash lamp.

[0025] Then, as depicted in block 320, the circuit board or substrate is placed under a flash lamp with some solder paste positioned between the electronic component and the circuit board. The solder paste can be a SAC-compatible solder paste or any solder paste including a thick-film material having a thickness greater than 50 microns. The substrate can be a circuit board having a standard circuit board material such as FR4, a thermoset, or a thermoplastic having a maximum working temperature less than 200°C. Then, as shown in block 330, multiple pulses of light from the flash lamp are applied to the electronic component, the solder paste, and the circuit board.

[0026] As depicted in block 340, during the application of the light pulses (i.e., the heat treatment operation), the radiant exposure value of each light pulse from the flash lamp is acquired by a calibrated photodiode and integrator, such as integrator 265 from FIG. 2, and the temperature of the electronic components soldered on the circuit board is acquired by an IR camera, such as IR camera 280 from FIG. 2.

[0027] In addition, an IR camera monitors the circuit board during application of the light pulse to measure the temperature of the electronic components and / or the temperature distribution across the circuit board. Because emissions from the flash lamp are in the range of 250 nm to about 1,700 nm and the IR camera "sees" primarily in the 10 micron portion of the electromagnetic spectrum, there is no interference from the flash lamp with the infrared emissions by the circuit board. Thus, the IR camera can "see" the heating across the circuit board during the flash lamp treatment.

[0028] The power information measured by the photodiode is converted to a radiation exposure value using a calibration factor obtained during the calibration process (i.e., block 310). Based on the radiation exposure value of the light pulse and the measured temperature information of the electronic component, the frequency and / or duty cycle of the subsequent light pulse can be adaptively adjusted prior to application of the subsequent light pulse, as shown in block 350.

[0029] For example, a computer such as computer 290 from Figure 2 can instruct a frequency controller such as frequency controller 240 from Figure 2 to adjust the duty cycle of the next light pulse to be emitted by the flash lamp based on the radiant exposure value and the measured temperature information to track a desired temperature profile of the electronic components on the circuit board. The temperature profile of the electronic components on the circuit board can be as follows: [Table 1]

[0030] A determination is then made as to whether the solder paste has been reflowed, as depicted in block 360. If the solder paste has not been reflowed, the process returns to block 330, but if the solder paste has been reflowed, the application of the light pulses may be stopped, as shown in block 370. The steps shown in blocks 330, 340, 350, and 360 are performed in an iterative manner. After the solder paste has been reflowed, it is then cooled to solidify, at which point electronic components are connected to the circuit board via the solidified solder.

[0031] For a given firing voltage from a capacitor bank, such as capacitor bank 220 from FIG. 2, the integrated photodiode signal is proportional to the radiation exposure of each pulse over a long range of pulse lengths and pulse frequencies. There are two requirements for this technique. First, to use the integrated photodiode signal to correlate the energy emitted from the flash lamp on a pulse-by-pulse basis over a range of firing frequencies, the capacitor bank charging power supply, such as capacitor bank charging power supply 210 from FIG. 2, must be large enough to fully recharge the capacitor bank, such as capacitor bank 220 from FIG. 2, before each light pulse is emitted. Second, to correlate the integrated power signal from the photodiode to the bolometer over a range of pulse lengths, the capacitor bank voltage must have minimal droop during discharge. Doing so ensures that the peak spectral output intensity remains relatively constant during discharge. Therefore, a large capacity is preferred, and the size of the capacitor bank depends on the accuracy required for the power measurement. Preferably, less than 5% of the stored energy in the capacitor bank is discharged in each pulse.

[0032] The techniques described in this disclosure enable traceable measurement of the radiant energy emitted by a flash lamp. Thus, for a 10 Hz firing rate, the average power (or cumulative energy) emitted can be known at a 10 Hz data rate. For a 50 Hz firing rate, the average power emitted can be known at a 50 Hz data rate. Furthermore, the firing rate and / or duty cycle of the flash lamp can be electronically adjusted by a frequency controller during processing intervals longer than 1 second to generate a tailored power profile. The amount of energy delivered over time can be varied by varying the pulse rate and / or duty cycle.

[0033] Heating profiles for electronic components can be preprogrammed or modified during processing as determined by temperature sensors trained on the circuit board (or material) as it is being processed. Regarding the latter, understanding the emitted energy from the flash lamp is only half the problem. The entire circuit board, including the circuit board, trace metals, electronic components, and solder paste, is illuminated. Because each item has a different absorption rate of the flash lamp emission, a different thermal mass, and a different heat transfer to surrounding components, they each heat up to different temperatures from a uniform emission source. Therefore, in addition to understanding the flash lamp emission, it is also important to understand the heating response of the different electronic components on the circuit board due to the emission.

[0034] Multiple thermal processes such as activating the flux, evaporating the flux, heating the solder particles to their melting point, melting the solder particles, and reflowing the solder can be performed by the system 100 over a processing time of 1 to 10 seconds. Because all of the processing steps described above are performed over a very short period of time, it is necessary to be able to deliver a known amount of power to the circuit board and vary that power during processing.

[0035] System 100 can also emit the same average power over a period of time with varying spectral output. Because different components or electronic parts have different absorptivities across the flash lamp 250 emission spectrum, this allows for better discrimination between what is heated on the circuit board by the beam and what is not. Specifically, when the capacitor bank 220 firing voltage is higher, the total power across the spectrum is higher than for lower voltages, but the proportion of shorter wavelength light is higher (see FIG. 4). In other words, when the capacitor bank 220 firing voltage is lower, the spectral emission in all bands is lower, but the percentage of longer wavelength light is higher. Because the flash lamp duty cycle can be adjusted, the same amount of radiant power delivered over many pulses can still be at a predetermined level independent of the firing voltage. This can be achieved by varying the pulse length or / and pulse frequency. More specifically, if the portion of the circuit board desired to be heated is more absorbent at longer wavelengths in the emission spectrum, one can have a longer pulse length or higher frequency pulse of the flash lamp 250, depositing the same emission power profile as a higher voltage, shorter pulse length, shorter frequency condition. Additionally, optical filtering of the emission may be utilized to allow even more discrimination. For system 100, control parameters include capacitor bank voltage, pulse length, pulse frequency, and total pulse train duration.

[0036] System 100 may include one or more lamp housings, each of which contains at least one flash lamp, such as flash lamp 250. This allows for thermal processing of solder on circuit boards and thick films on substrates by top illumination (e.g., thick film side illumination), bottom illumination (e.g., substrate side illumination), or both. The top and bottom flash lamps may be independently synchronized in their discharge initiation, or they may receive the same discharge initiation trigger signal.

[0037] The conveyor in system 100 includes two modes of operation: a stationary mode and a synchronous mode. When using the stationary mode, the circuit boards are not transported during processing, and the exposure profile is electronically controlled by frequency controller 240. In this case, the pulse frequency, and therefore the power emitted by flash lamps 250, may vary over the time of processing. Alternatively, the pulse length of each pulse may be changed during processing to adjust the energy per pulse delivered to the circuit board by flash lamps 250. In the synchronous mode, the same radiant exposure (i.e., J / cm) is applied to the transported circuit boards. 2 The pulse rate of the light pulses from the flash lamps 250 can be synchronized with the conveying speed of the conveyor to result in a total energy delivered in units of . When this is done, the delivered radiation exposure can be independent of the conveying speed.

[0038] The flash lamp housing, which holds the flash lamp 250 and has a reflector for directing light from the flash lamp 250 to the optical circuit board, can be tilted upward during synchronization mode, for example, rotated toward or away from the transport direction as the circuit board is transported past the flash lamp housing. When the flash lamp housing is parallel to the transported circuit board, the exposure is very uniform, with approximately 2% to 3% variation across the exposed area. When the flash lamp housing is far from the circuit board, the light pulse is less intense. Therefore, tilting the head of the flash lamp 250 allows the exposure to be stepped up or down in intensity as the circuit board is transported past the head of the flash lamp 250. This feature allows for further control of gases generated from processing the solder paste, so that electronic components can be successfully attached without failure.

[0039] As has been described, the present invention provides an improved method for electrically and mechanically connecting surface mount electronic components to a circuit board.

[0040] Although designed to process solder paste, the system 100 uses multiple pulses to deliver precise and high amounts of energy (>30 J / cm) delivered over a precise power profile for periods of 1-10 seconds. 2 The present invention is suitable for processing any thick film above 50 microns where the same problems arise, such as the need to apply a thermally sensitive adhesive. Additionally, the disclosed method allows for the ability to attach thermally sensitive electronic components to circuit boards over the prior art by reducing the total thermal budget. The reduced thermal budget also allows for the use of processing thick films on thermally sensitive substrates with maximum operating temperatures below 200°C. Examples include thermoplastics such as PVC, TPU, polyester, PET, PEN, paper, etc.

[0041] While the present invention has been particularly shown and described with reference to preferred embodiments, it will be understood by those skilled in the art that various changes in form and details can be made therein without departing from the spirit and scope of the invention.

Claims

1. A method for connecting an electronic component to a substrate, the method comprising: Providing a substrate, solder, and an electronic component; applying a plurality of light pulses from the flash lamp to heat the solder until the solder flows to solder the electronic component to the substrate; During the application of the plurality of light pulses, measuring the power of one of the plurality of light pulses from the flash lamp; measuring a temperature associated with the electronic components soldered onto the substrate; adaptively setting flash lamp operating parameters for a next light pulse based on the measured power of the one light pulse based on the measured temperature of the electronic component; To do A method comprising:

2. The method described in claim 1, wherein measuring the power is performed by using a photodiode.

3. The method of claim 2, further comprising calibrating the photodiode to generate a calibration coefficient.

4. The method of claim 3, further comprising converting the measured power into a radiation exposure value using the calibration coefficient, and wherein adaptively setting comprises setting the flash lamp operating parameters for the next light pulse according to the radiation exposure value.

5. The method of claim 1, wherein measuring the temperature is performed by using an infrared (IR) camera.

6. The method described in claim 5, wherein measuring the temperature includes measuring the temperature of the electronic component.

7. The method described in claim 1, wherein setting the flash lamp operating parameters is performed by changing the frequency of the next light pulse.

8. The method described in claim 1, wherein setting the flash lamp operating parameters is performed by changing the pulse length of the next light pulse.

9. The method of claim 1, wherein the substrate comprises a circuit board.

10. The method of claim 1, wherein the substrate comprises a thermoplastic material having a maximum working temperature of less than 200°C.

11. The method of claim 1, wherein the solder comprises a thick film material having a thickness greater than 50 microns.

12. The method of claim 1, further comprising transporting the electronic component during application of the multiple light pulses.

13. The method of claim 12, further comprising synchronizing the speed of the transport of the electronic component with the frequency of the multiple light pulses.

14. The method of claim 1, further comprising placing the electronic component in an environmentally controlled chamber prior to applying the multiple light pulses.

15. A system for connecting an electronic component to a substrate, the system comprising: a capacitive device; A switching device; a flash lamp for emitting light pulses, the flash lamp configured to receive charge from the capacitive device via the switching device; a light sensor for measuring the power of the light pulses from the flash lamp; a temperature sensor for measuring a temperature associated with an electronic component soldered onto the board; a processor configured to adaptively set flash lamp operating parameters for a next light pulse as a function of the measured power based on the measured temperature associated with the electronic component; and A system comprising:

16. The system described in claim 15, wherein the optical sensor comprises a photodiode, and the system further comprises a bolometer for calibrating the photodiode.

17. The system of claim 15, wherein the capacitive device includes a plurality of electrolytic capacitors.

18. The system described in claim 15, wherein the processor sets the flash lamp operating parameters of the next light pulse by setting the frequency of the next light pulse.

19. The system described in claim 15, wherein the processor sets the flash lamp operating parameters of the next light pulse by setting the pulse length of the next light pulse via a frequency controller.

20. The system described in claim 15, further comprising a conveyor for transporting the electronic components and the substrate to the flash lamp.

21. The system described in claim 15, further comprising an environmentally controlled chamber for containing the electronic components during application of the light pulse.

Images