Discussion on heat conduction and heat uniform distribution of LED dis…
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작성자 Anneliese 댓글 0건 조회 9회 작성일 24-06-03 16:09본문
This article only focuses on the customer's doubts about the poor heat dissipation of the COB integrated package LED display panel. What level can COB integrated package (COBIP) technology achieve in solving the heat conduction problem of LED display panels? Is there any better technology than it in solving the heat conduction and heat distribution problems of LED display panels? The scope of this article is limited to LED display field.
1. COBIP technology significantly improves the thermal conductivity of LED display panels
In actual business activities, customers often say that the heat dissipation of COB is not as good as that of SMD. Is this really the case? COB mentioned here refers to COBIP or COBLIP?
If we ask why COB does not dissipate heat well and why SMD dissipates heat well, I am afraid that no one can come up with decent arguments and arguments. Then why do customers form this impression? The main reason is that the misleading publicity of COB integrated packaging technology produced by traditional technology in the industry has a certain effect, and the motivation is understandable.
In the research on industrial issues that began in 2016, we have seriously considered the heat dissipation and heat distribution of LED display panels. We believe that the root of the heat dissipation problem lies in solving the heat conduction problem. As long as the internal heat of the LED display panel can be extracted as soon as possible, the heat dissipation is There are many solutions. Therefore, we established the functional structure models of pixel microcirculation systems of various packaging technologies under the two packaging systemization technologies of LED display panels, deduced their respective pixel total thermal working models, and then quantitatively studied their thermal conductivity. , see Figure 1.
In the center, two systematic packaging technologies are the main lines, and the left column is the bracket-pin single-device packaging system technology, including No. 1 SMD technology, No. 2 IMD (COBLIP or N in 1) technology, and No. 3 lamp-driver-in-seal SMD technology. The column on the right is the integrated packaging system technology without bracket pins, including No. 4 COBIP + front-mounted LED chip technology combination, No. 5 COBIP + flip-chip LED chip technology combination, No. 6 CNCIP + flip-chip LED chip + front-mounted driver IC chip technology combination, 7 No. COCIP + flip-chip LED chip + front-mount driver IC chip technology combination.
COBIP technology is the first-generation technology under the bracket-free integrated packaging system technology. It is a semi-bracket-free integrated packaging technology. Above-mentioned No. 4 and No. 5 technologies are exactly two technical variants thereof.
Before formally evaluating the thermal conduction effects of the above-mentioned different packaging technologies, let's understand some basic concepts below.
The basic functions of LED display pixels: first, to achieve continuous and stable LED chip controllable lighting, and second, to achieve a good pixel thermal working model.
Lighting is an electrical function. We hope to obtain higher light efficiency, better optical consistency, faster dynamic response speed and long-term reliability. This will be discussed in another article.
A good thermal working model of the pixel is to quickly dissipate the thermal load generated in the pixel, which involves which and how much thermal conductivity materials are used in the packaging technology, whether there is the shortest possible thermal conduction path and the least possible contact thermal resistance interface.
The functional structure model of the pixel microcirculation system can well reflect the realization of the electrical function of the LED chip and deduce the thermal working model of the pixel we need.
The thermal conductivity of the material:
In each packaging technology, the thermal conductivity of the packaging materials used by each manufacturer is different, as shown in Figure 2. For the sake of simplicity in comparison, we first assume that all packaging manufacturers use the same packaging technology materials, so we only need to pay attention to the comparison of the length of the heat conduction path and the number of contact thermal resistance interfaces.
Contact thermal resistance: When heat flows through the interface of two contacting solids, the interface itself presents an obvious thermal resistance to heat flow, which is called contact thermal resistance. The size of the contact thermal resistance is related to the fineness of the surface of the contact material. The higher the fineness, the larger the contact area, the less air remains in the gap between the contact surfaces, and the lower the thermal resistance value.
Chip-level contact thermal resistance: The contact thermal resistance generated inside the encapsulation compound. It is mainly generated on the welding surface of bonding wire or chip electrode and various materials.
Device-level contact thermal resistance: The contact thermal resistance generated outside the encapsulant. Produced on the soldering surface of the support pins of the packaged device and the circuit copper foil on the display panel PCB.
Generally speaking, the contact thermal group value of device-level pin soldering per unit area is greater than the contact thermal resistance value of chip-level electrode soldering. Because the chip-level electrode soldering contact thermal resistance interface is more delicate, the device-level pin soldering contact thermal resistance interface will be rougher.
Next, find out the corresponding packaging technology LED display panel pixel total thermal working model according to the sequence of packaging technology numbers in Figure 1:
1.1 SMD packaging technology pixel total thermal working model
The functional structure model of the pixel microcirculation system of SMD packaging technology is shown in Figure 3:
It can be seen that the heat source of the LED display panel with SMD packaging technology mainly comes from two parts: one is an LED chipset 10 in the SMD device, and the other is the driver IC packaging device 14 . If a driver IC package device controls S LED chipsets, then the heat source generated by each pixel is 1 LED chipset + 1/S.
The heat conduction path of the LED chipset 10: 10-8-7-11-4-3, the heat flows through 6 kinds of materials, and the contact thermal resistance interfaces 10/8, 8/7, 7/11, 11/4 and 4/3 are 5, of which 4 are at the chip level and 1 is at the device level.
The heat conduction path of the drive IC package device 14: 14-13-12, the heat flows through 3 kinds of materials, and the contact thermal resistance interfaces 14/13 and 13/12 generated by these 3 kinds of materials are 2, and they are all at the device level .
The total thermal working model of the pixel is 9 kinds of materials involved in heat conduction + 7 contact thermal resistance interfaces (4 chip level + 3 device level).
Since one driver IC package device needs to control S LED chipsets, the length of the circuit controlling each LED chipset is different. The short circuit generates less heat, and the long circuit generates more heat. The thermal load of the driver IC package device Large, high-temperature accumulation areas will be generated around the soldering area of the device pins, and the display panel will have serious uneven heat distribution, which will easily lead to accelerated light decay of the LED chipset around the soldering area, and then light spots will appear.
2.2 IMD (COBLIP or N in 1) packaging technology pixel total thermal working model
The functional structure model of the pixel microcirculation system of IMD packaging technology is shown in Figure 4:
It can be seen that the heat source of the LED display panel with IMD packaging technology mainly comes from two parts: one is the N LED chipsets 10 or 15 in the IMD device, and the other is the driver IC packaging device 14 . If a driver IC package device controls S LED chipsets, then the heat source generated by each pixel is 1 LED chipset + 1/S.
The heat conduction path of each LED chipset: 10-8-7-11-4-3, the heat flows through 6 kinds of materials, and the contact thermal resistance interfaces generated by these 6 kinds of materials are 10/8, 8/7, 7/11 , 11/4, and 4/3 are 5, of which 4 are at the chip level and 1 is at the device level.
The heat conduction path of the drive IC package device 14: 14-13-12, the heat flows through 3 kinds of materials, and the contact thermal resistance interfaces 14/13 and 13/12 generated by these 3 kinds of materials are 2, and they are all at the device level .
The total thermal working model of the pixel is 9 kinds of materials involved in heat conduction + 7 contact thermal resistance interfaces (4 chip level + 3 device level).
Since one driver IC package device needs to control S LED chipsets, the length of the circuit controlling each LED chipset is different. The short circuit generates less heat, and the long circuit generates more heat. The thermal load of the driver IC package device If it is large, a high-temperature accumulation area will be generated around the welding area of the device pins, and the display panel will have a serious problem of uneven heat distribution, which will easily lead to accelerated light decay of the LED chipset around the welding area, and then light spots will appear.
Although the total pixel thermal model of IMD and SMD is the same, there are N LED chipsets in the IMD package device, and the number of soldering pins of the general IMD device is divided into each pixel, which is half less than that of the SMD device (mainstream IMD package devices are generally 4 pixels and 8 pins). On the one hand, the heat source in the packaged device increases, and the heat load increases. On the other hand, the number of IMD device soldering pins required for heat dissipation is reduced, and serious thermal blockage will occur on the heat dissipation path. The actual heat dissipation effect is much worse than that of SMD. In the case of the same brightness and design requirements, IMD device pixel light attenuation will be faster than SMD.
IMD technology uses COB limited integrated packaging technology on the PCB board 5 in the bracket structure, that is, COBLIP (Chip On Board Limited Integrated Packaging). The customer said that COB heat dissipation is not as good as SMD, which should be the case, not the latter Speaking of the COBIP situation.
3.3 Total heat working model of pixel driven and sealed by SMD packaging technology
Figure 5 shows the functional structure model of the pixel microcirculation system of the light-driven combined-seal SMD packaging technology:
It can be seen that the heat source of the LED display panel with the LED driver-in-package SMD packaging technology comes from two parts: one is an LED chipset 10 and a driver IC bare chip 13 in the LED driver-in-package SMD device. Lamp-on-seal SMD is a static non-scanning technology.
The heat conduction path of the LED chipset 10: 10-14-7-11-4-3, the heat flows through 6 kinds of materials, and the contact thermal resistance interfaces 10/14, 14/7, 7/11, 11/4 and 4/3 are 5, of which 4 are at the chip level and 1 is at the device level.
The heat conduction path of the driver IC bare chip 13: 13-8-7-11-4-3, the heat flows through 6 kinds of materials, and the contact thermal resistance interfaces 13/8, 8/7, 7/ 11, 11/4, 4/3 are 5, of which 4 are chip level and 1 is device level.
The total thermal working model of the pixel is 8 kinds of materials participating in heat conduction + 9 contact thermal resistance interfaces (8 chip level + 1 device level).
Because both the LED chipset 10 and the driver IC bare chip 13 have the same heat conduction material 7-11-4-3.
Why there is only one device-level contact thermal resistance interface in the total thermal working model of the lamp driver packaged SMD pixel, because the LED chipset 10 and the driver IC bare chip 13 dissipate heat through the same 4/3 device-level contact interface of.
By comparing SMD and IMD, we found that the heat conduction paths of the LED chipsets of these three packaging technologies are the same length, while the heat conduction paths of the driver IC have undergone the following changes:
First of all, the driver IC is converted from the device level of SMD and IMD to the bare crystal level of lamp driver packaged SMD. The driver IC package device is no longer placed on the back of the LED display panel dot matrix pixel, but is placed in the form of bare crystal. Into each display pixel unit, together with the LED chipset, the plane layout in the same pixel is carried out. Secondly, the contact thermal resistance interface has changed, the contact thermal resistance interface at the chip level has increased, and the contact thermal resistance interface at the device level has decreased.
Since one driver IC only controls one LED chipset, the heat load on the driver IC is reduced, and the heat generated is also reduced accordingly. Moreover, the length of the circuit controlling each LED chipset is consistent. Under the same requirement conditions, the heat in the lamp driver packaged SMD device will not be much higher than that in the SMD device, and at the same time solve the problem of uneven heat distribution in the SMD and IMD display panels.
In general, within the technical framework of the stand-off single-device packaging system, the total thermal working model of the pixel of the light-driven package SMD has theoretical advantages compared with SMD and IMD. train of thought. There is currently a lack of actual case data on the cooling effect of practical applications, and it is difficult to make an assessment. But one thing is for sure, the reason that limits its commercial large-scale application is not the pros and cons of its total thermal working model of the pixel, but the failure rate of the packaging device is too high, and the device obtained from the manufacturer fails. Rate data is 3000/PPM.
So far, the pixel total thermal working models of the three packaging technologies of SMD, IMD, and lamp driver combined package SMD under the stand-off pin type single-device packaging system technology have been summarized. Next, we will continue to find out the stand-off pin type integrated package. The pixel total thermal working model of various packaging technologies LED display panels under the system technology:
No. 4.4 COBIP (Chip On Board Integrated Packaging) + full LED chip set technology combination pixel total thermal working model
Figure 6 shows the functional structure model of the pixel microcirculation system of COBIP+ formal LED chipset technology combination:
It can be known that the heat source of the LED display panel with COBIP+ front-mounted LED chipset technology combination mainly comes from two parts: one is the LED chipset 6 in the pixel, and the other is the driver IC packaging device 9. If a driver IC package device controls S LED chipsets, then the heat source generated by each pixel is 1 LED chipset + 1/S.
The heat conduction path of LED chipset 6: 6-5-3, heat flows through 3 kinds of materials, and the contact thermal resistance interfaces 6/5 and 5/3 generated by these 3 kinds of materials are 2, all of which are at the chip level.
The heat conduction path of the driving IC package device 9: 9-8-7, the heat flows through 3 kinds of materials, and the contact thermal resistance interfaces 9/8 and 8/7 generated by these 3 kinds of materials are 2, and they are all at the device level .
The total thermal working model of the pixel is 6 kinds of materials participating in heat conduction + 4 contact thermal resistance interfaces (2 chip level + 2 device level).
Since one driver IC package device needs to control S led advertising board chipsets, the length of the circuit controlling each LED chipset is different. The short circuit generates less heat, and the longer circuit generates more heat. The thermal load of the driver IC package device Large, a high-temperature accumulation area is generated around the soldering area of the device pin. As with SMD and IMD packaging techniques, significant
1. COBIP technology significantly improves the thermal conductivity of LED display panels
In actual business activities, customers often say that the heat dissipation of COB is not as good as that of SMD. Is this really the case? COB mentioned here refers to COBIP or COBLIP?
If we ask why COB does not dissipate heat well and why SMD dissipates heat well, I am afraid that no one can come up with decent arguments and arguments. Then why do customers form this impression? The main reason is that the misleading publicity of COB integrated packaging technology produced by traditional technology in the industry has a certain effect, and the motivation is understandable.
In the research on industrial issues that began in 2016, we have seriously considered the heat dissipation and heat distribution of LED display panels. We believe that the root of the heat dissipation problem lies in solving the heat conduction problem. As long as the internal heat of the LED display panel can be extracted as soon as possible, the heat dissipation is There are many solutions. Therefore, we established the functional structure models of pixel microcirculation systems of various packaging technologies under the two packaging systemization technologies of LED display panels, deduced their respective pixel total thermal working models, and then quantitatively studied their thermal conductivity. , see Figure 1.
In the center, two systematic packaging technologies are the main lines, and the left column is the bracket-pin single-device packaging system technology, including No. 1 SMD technology, No. 2 IMD (COBLIP or N in 1) technology, and No. 3 lamp-driver-in-seal SMD technology. The column on the right is the integrated packaging system technology without bracket pins, including No. 4 COBIP + front-mounted LED chip technology combination, No. 5 COBIP + flip-chip LED chip technology combination, No. 6 CNCIP + flip-chip LED chip + front-mounted driver IC chip technology combination, 7 No. COCIP + flip-chip LED chip + front-mount driver IC chip technology combination.
COBIP technology is the first-generation technology under the bracket-free integrated packaging system technology. It is a semi-bracket-free integrated packaging technology. Above-mentioned No. 4 and No. 5 technologies are exactly two technical variants thereof.
Before formally evaluating the thermal conduction effects of the above-mentioned different packaging technologies, let's understand some basic concepts below.
The basic functions of LED display pixels: first, to achieve continuous and stable LED chip controllable lighting, and second, to achieve a good pixel thermal working model.
Lighting is an electrical function. We hope to obtain higher light efficiency, better optical consistency, faster dynamic response speed and long-term reliability. This will be discussed in another article.
A good thermal working model of the pixel is to quickly dissipate the thermal load generated in the pixel, which involves which and how much thermal conductivity materials are used in the packaging technology, whether there is the shortest possible thermal conduction path and the least possible contact thermal resistance interface.
The functional structure model of the pixel microcirculation system can well reflect the realization of the electrical function of the LED chip and deduce the thermal working model of the pixel we need.
The thermal conductivity of the material:
In each packaging technology, the thermal conductivity of the packaging materials used by each manufacturer is different, as shown in Figure 2. For the sake of simplicity in comparison, we first assume that all packaging manufacturers use the same packaging technology materials, so we only need to pay attention to the comparison of the length of the heat conduction path and the number of contact thermal resistance interfaces.
Contact thermal resistance: When heat flows through the interface of two contacting solids, the interface itself presents an obvious thermal resistance to heat flow, which is called contact thermal resistance. The size of the contact thermal resistance is related to the fineness of the surface of the contact material. The higher the fineness, the larger the contact area, the less air remains in the gap between the contact surfaces, and the lower the thermal resistance value.
Chip-level contact thermal resistance: The contact thermal resistance generated inside the encapsulation compound. It is mainly generated on the welding surface of bonding wire or chip electrode and various materials.
Device-level contact thermal resistance: The contact thermal resistance generated outside the encapsulant. Produced on the soldering surface of the support pins of the packaged device and the circuit copper foil on the display panel PCB.
Generally speaking, the contact thermal group value of device-level pin soldering per unit area is greater than the contact thermal resistance value of chip-level electrode soldering. Because the chip-level electrode soldering contact thermal resistance interface is more delicate, the device-level pin soldering contact thermal resistance interface will be rougher.
Next, find out the corresponding packaging technology LED display panel pixel total thermal working model according to the sequence of packaging technology numbers in Figure 1:
1.1 SMD packaging technology pixel total thermal working model
The functional structure model of the pixel microcirculation system of SMD packaging technology is shown in Figure 3:
It can be seen that the heat source of the LED display panel with SMD packaging technology mainly comes from two parts: one is an LED chipset 10 in the SMD device, and the other is the driver IC packaging device 14 . If a driver IC package device controls S LED chipsets, then the heat source generated by each pixel is 1 LED chipset + 1/S.
The heat conduction path of the LED chipset 10: 10-8-7-11-4-3, the heat flows through 6 kinds of materials, and the contact thermal resistance interfaces 10/8, 8/7, 7/11, 11/4 and 4/3 are 5, of which 4 are at the chip level and 1 is at the device level.
The heat conduction path of the drive IC package device 14: 14-13-12, the heat flows through 3 kinds of materials, and the contact thermal resistance interfaces 14/13 and 13/12 generated by these 3 kinds of materials are 2, and they are all at the device level .
The total thermal working model of the pixel is 9 kinds of materials involved in heat conduction + 7 contact thermal resistance interfaces (4 chip level + 3 device level).
Since one driver IC package device needs to control S LED chipsets, the length of the circuit controlling each LED chipset is different. The short circuit generates less heat, and the long circuit generates more heat. The thermal load of the driver IC package device Large, high-temperature accumulation areas will be generated around the soldering area of the device pins, and the display panel will have serious uneven heat distribution, which will easily lead to accelerated light decay of the LED chipset around the soldering area, and then light spots will appear.
2.2 IMD (COBLIP or N in 1) packaging technology pixel total thermal working model
The functional structure model of the pixel microcirculation system of IMD packaging technology is shown in Figure 4:
It can be seen that the heat source of the LED display panel with IMD packaging technology mainly comes from two parts: one is the N LED chipsets 10 or 15 in the IMD device, and the other is the driver IC packaging device 14 . If a driver IC package device controls S LED chipsets, then the heat source generated by each pixel is 1 LED chipset + 1/S.
The heat conduction path of each LED chipset: 10-8-7-11-4-3, the heat flows through 6 kinds of materials, and the contact thermal resistance interfaces generated by these 6 kinds of materials are 10/8, 8/7, 7/11 , 11/4, and 4/3 are 5, of which 4 are at the chip level and 1 is at the device level.
The heat conduction path of the drive IC package device 14: 14-13-12, the heat flows through 3 kinds of materials, and the contact thermal resistance interfaces 14/13 and 13/12 generated by these 3 kinds of materials are 2, and they are all at the device level .
The total thermal working model of the pixel is 9 kinds of materials involved in heat conduction + 7 contact thermal resistance interfaces (4 chip level + 3 device level).
Since one driver IC package device needs to control S LED chipsets, the length of the circuit controlling each LED chipset is different. The short circuit generates less heat, and the long circuit generates more heat. The thermal load of the driver IC package device If it is large, a high-temperature accumulation area will be generated around the welding area of the device pins, and the display panel will have a serious problem of uneven heat distribution, which will easily lead to accelerated light decay of the LED chipset around the welding area, and then light spots will appear.
Although the total pixel thermal model of IMD and SMD is the same, there are N LED chipsets in the IMD package device, and the number of soldering pins of the general IMD device is divided into each pixel, which is half less than that of the SMD device (mainstream IMD package devices are generally 4 pixels and 8 pins). On the one hand, the heat source in the packaged device increases, and the heat load increases. On the other hand, the number of IMD device soldering pins required for heat dissipation is reduced, and serious thermal blockage will occur on the heat dissipation path. The actual heat dissipation effect is much worse than that of SMD. In the case of the same brightness and design requirements, IMD device pixel light attenuation will be faster than SMD.
IMD technology uses COB limited integrated packaging technology on the PCB board 5 in the bracket structure, that is, COBLIP (Chip On Board Limited Integrated Packaging). The customer said that COB heat dissipation is not as good as SMD, which should be the case, not the latter Speaking of the COBIP situation.
3.3 Total heat working model of pixel driven and sealed by SMD packaging technology
Figure 5 shows the functional structure model of the pixel microcirculation system of the light-driven combined-seal SMD packaging technology:
It can be seen that the heat source of the LED display panel with the LED driver-in-package SMD packaging technology comes from two parts: one is an LED chipset 10 and a driver IC bare chip 13 in the LED driver-in-package SMD device. Lamp-on-seal SMD is a static non-scanning technology.
The heat conduction path of the LED chipset 10: 10-14-7-11-4-3, the heat flows through 6 kinds of materials, and the contact thermal resistance interfaces 10/14, 14/7, 7/11, 11/4 and 4/3 are 5, of which 4 are at the chip level and 1 is at the device level.
The heat conduction path of the driver IC bare chip 13: 13-8-7-11-4-3, the heat flows through 6 kinds of materials, and the contact thermal resistance interfaces 13/8, 8/7, 7/ 11, 11/4, 4/3 are 5, of which 4 are chip level and 1 is device level.
The total thermal working model of the pixel is 8 kinds of materials participating in heat conduction + 9 contact thermal resistance interfaces (8 chip level + 1 device level).
Because both the LED chipset 10 and the driver IC bare chip 13 have the same heat conduction material 7-11-4-3.
Why there is only one device-level contact thermal resistance interface in the total thermal working model of the lamp driver packaged SMD pixel, because the LED chipset 10 and the driver IC bare chip 13 dissipate heat through the same 4/3 device-level contact interface of.
By comparing SMD and IMD, we found that the heat conduction paths of the LED chipsets of these three packaging technologies are the same length, while the heat conduction paths of the driver IC have undergone the following changes:
First of all, the driver IC is converted from the device level of SMD and IMD to the bare crystal level of lamp driver packaged SMD. The driver IC package device is no longer placed on the back of the LED display panel dot matrix pixel, but is placed in the form of bare crystal. Into each display pixel unit, together with the LED chipset, the plane layout in the same pixel is carried out. Secondly, the contact thermal resistance interface has changed, the contact thermal resistance interface at the chip level has increased, and the contact thermal resistance interface at the device level has decreased.
Since one driver IC only controls one LED chipset, the heat load on the driver IC is reduced, and the heat generated is also reduced accordingly. Moreover, the length of the circuit controlling each LED chipset is consistent. Under the same requirement conditions, the heat in the lamp driver packaged SMD device will not be much higher than that in the SMD device, and at the same time solve the problem of uneven heat distribution in the SMD and IMD display panels.
In general, within the technical framework of the stand-off single-device packaging system, the total thermal working model of the pixel of the light-driven package SMD has theoretical advantages compared with SMD and IMD. train of thought. There is currently a lack of actual case data on the cooling effect of practical applications, and it is difficult to make an assessment. But one thing is for sure, the reason that limits its commercial large-scale application is not the pros and cons of its total thermal working model of the pixel, but the failure rate of the packaging device is too high, and the device obtained from the manufacturer fails. Rate data is 3000/PPM.
So far, the pixel total thermal working models of the three packaging technologies of SMD, IMD, and lamp driver combined package SMD under the stand-off pin type single-device packaging system technology have been summarized. Next, we will continue to find out the stand-off pin type integrated package. The pixel total thermal working model of various packaging technologies LED display panels under the system technology:
No. 4.4 COBIP (Chip On Board Integrated Packaging) + full LED chip set technology combination pixel total thermal working model
Figure 6 shows the functional structure model of the pixel microcirculation system of COBIP+ formal LED chipset technology combination:
It can be known that the heat source of the LED display panel with COBIP+ front-mounted LED chipset technology combination mainly comes from two parts: one is the LED chipset 6 in the pixel, and the other is the driver IC packaging device 9. If a driver IC package device controls S LED chipsets, then the heat source generated by each pixel is 1 LED chipset + 1/S.
The heat conduction path of LED chipset 6: 6-5-3, heat flows through 3 kinds of materials, and the contact thermal resistance interfaces 6/5 and 5/3 generated by these 3 kinds of materials are 2, all of which are at the chip level.
The heat conduction path of the driving IC package device 9: 9-8-7, the heat flows through 3 kinds of materials, and the contact thermal resistance interfaces 9/8 and 8/7 generated by these 3 kinds of materials are 2, and they are all at the device level .
The total thermal working model of the pixel is 6 kinds of materials participating in heat conduction + 4 contact thermal resistance interfaces (2 chip level + 2 device level).
Since one driver IC package device needs to control S led advertising board chipsets, the length of the circuit controlling each LED chipset is different. The short circuit generates less heat, and the longer circuit generates more heat. The thermal load of the driver IC package device Large, a high-temperature accumulation area is generated around the soldering area of the device pin. As with SMD and IMD packaging techniques, significant
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