Technology is constantly evolving. The industrial sector follows the development, and the company focuses on the most needed applications in the market and changes their production focus according to the needs of consumers. AMX invented a new type of sintering tool Micro-Punch for its sintering press, which can independently press each component on the substrate, chip, chip with a specific pressure (thermistor, IGBT, mosfet).

Technology is constantly evolving. The industrial sector follows the development, and the company focuses on the most needed applications in the market and changes their production focus according to the needs of consumers. AMX invented a new type of sintering tool Micro-Punch for its sintering press, which can independently press each component on the substrate, chip, chip with a specific pressure (thermistor, IGBT, MOSFET). According to AMX, the Micro-Punch tool ensures uniform pressure and eliminates the following high-value problems: mold breakage, tilt, delamination, and voids. The Micro-Punch tool has no restrictions on the number or placement of chips; it can adapt to any DBC size or configuration, and can independently press the thinnest and smallest molds, even if they are very close to each other.

Pressure sintering

Silver (Ag)/copper (Cu) pressure sintering (see Figure 1) is a heat treatment process applied to powder materials (ie nanoparticles) to provide higher strength, integrity and conductivity. According to AMX, sintering is currently considered the most reliable technology for connecting power Electronic components. Silver sintered paste is currently the most widely used material. The melting point is about 960˚C, and the thermal conductivity of silver sintered paste is between 130 and 250 W/(m·K). Silver sinter paste has high adhesion to epoxy resin, can keep components in a fixed position for excellent management, and can generally increase the overall output of the process. The next generation requires copper sintering, especially to achieve significant cost savings. Compared with other bonding methods,

• It has the best thermal conductivity (》150 W/(m⋅K)).
• It has the best conductivity.
• It provides the best results in durability tests, even 100 times better than soldered interconnects.
• It shows a higher remelting temperature (>400˚C).

According to AMX, its patented pressure sintering technology allows:

• Sintering silicon and silicon carbide on DBC/AMC and other electroplated substrates or bare copper
• Frame/discrete
• Embedded molds, clips, gaskets, etc.
• Interaction of different materials, surfaces and processes

New applications include multi-level interconnection, integrated modules, component connections, power distribution, UPS conversion and storage, charging stations, inverters, servo motors, radars and sensors.

Talking about power semiconductor sintering chip technology
Figure 1: Schematic diagram of pressure sintering

A new method: Micro-Punch

During the research process, the company obtained an innovation patent, which achieved the best results from the sintering process, as shown in Figure 2. This is the Micro-Punch system, which is completely different from the traditional system and has a significant improvement over the previous system. The first system consists of a single press, which applies the same force to all components. Any difference in thickness of the various components will inevitably cause problems. In other words, if the dough layer is slightly thicker at a certain point, all the force of the press is accurately applied at that point, thereby increasing the pressure disproportionately and increasing the risk of material cracking.

The company introduced a major innovation with the Micro-Punch system: it now uses a dedicated press to apply pressure independently at each point. As a result, the previous problem was eliminated. Alessio Greci, Sales Manager of AMX, said: “AMX patents revolutionized this production area. The competition developed some intermediate and alternative solutions, usually grouping several presses into subgroups, but the MicroPunch system performed well in terms of repeatability. Especially in advanced packaging applications, although the cost of ownership and processing time are the same.”

Talking about power semiconductor sintering chip technology
Figure 2: One of AMX’s patented methods (right) and the classic method (left)

Talking about power semiconductor sintering chip technology
Figure 3: Evolution of AG sintering technology

Maximum customization

According to AMX, the Micro-Punch system can be customized to meet customer needs. In fact, many of them care more about the accuracy and reliability of the solution rather than its cost. Elimination of material damage is the primary requirement. This requirement is most obvious when various types of electronic components (such as a combination of diodes, mosfets and thermistors) are involved in the process. Using Micro-Punch, each presser foot is dedicated to a point (see Figure 4), and the entire system can independently press the thermistor and IGBT.

In addition, according to AMX, Micro-Punch can apply different and independent pressures to various electronic components. In this way, if the customer thinks that the component is more brittle and does not respond well to high pressure, they can reduce the pressure slightly. Therefore, in the design stage and according to the customer’s specifications, it is possible to choose between different pressures and applied components. Therefore, the final production machine is customized to meet the needs of the end user. For example, you can define the pressure ratio between various pistons and specify a parameter that indicates that the pressure of one piston must be twice that of the other piston.

“Obviously, these initially selected parameters can be modified by the customer each time the loop changes,[they]can modify the relationship between the applied pressures from time to time,” Gracie said. He continued, “The Micro-Punch system can handle elements that are very close to each other, because in theory these components can have zero GAP and can move freely while contacting each other. Sintering is currently used in Semiconductor applications, such as SiC.”

Talking about power semiconductor sintering chip technology
Figure 4: A single punch allows you to apply pressure individually.

Sintering in the automotive industry

In the past few years, everything in the car has been welded together. AMX also implements pressure sintering methods in the automotive sector, especially for ultra-high power modules. Today, the market requires greater miniaturization and high power, and most of the company’s activities will focus on such applications. There are also implementations of public transport with trains, but they obviously have no space issues. In fact, miniaturization mainly involves the automotive field. Other applications of power modules also involve data centers, uninterruptible power supplies and large power transformers.

Pressure sintering: a set of important parameters

The difference between different sintering procedures is not so much determined by the type of parts to be sintered, as it is determined by the selection and use of the slurry. Customers can choose the paste and workflow to follow. Obviously, some initial parameters are selected a priori, more or less standard. The sintering process requires a temperature of about 250˚C, a pressure of 15 to 25 MPa, and a time of about three minutes. This is the starting point for describing the entire process.

Based on the initial results, some parameters can be adjusted to obtain the best results. Usually, customers check the influence of force or heat, observe how components react to various types of fatigue, and analyze individual parts under a microscope. Usually, these parameters are set by the solder paste manufacturer and fine-tuned one by one during the test. Finally, pressure sintering is a process that allows high-temperature sealing, with high reliability and perfect repeatability, and is currently considered the best solution. Other parameters must be evaluated, such as temperature and thermal expansion coefficient.

Dual feedback system

AMX provides a “dual feedback” option. This is a feature to avoid errors when applying pressure to the components. Control the pressure exerted on two aspects:

• On the press
• At a specific point where the force is applied

A double check using a force sensor evaluates whether the force applied to the press is consistent with the force received by the component. After understanding the entire sintering area, you can calculate the pressure applied from above and the theoretical force constraining the reaction force, and compare it with the sensor output (see Figure 5). In fact, the operator may remove the presser foot for cleaning, and then forget to replace it. In this case, the programmed pressure will be different from the actual pressure applied to the component, resulting in a significant force imbalance. In other words, when the presser foot does not apply the expected force, the system will detect and notify the operator. Several sensors are also used for oxygen concentration and temperature, although seemingly redundant, they are used for safety reasons (for example, the sensor may malfunction). All this information is collected to get a complete overview of the entire process.

Talking about power semiconductor sintering chip technology
Figure 5: In pressure sintering, each press is controlled and completely independent of other presses.

Technology is constantly evolving. The industrial sector follows the development, and the company focuses on the most needed applications in the market and changes their production focus according to the needs of consumers. AMX invented a new type of sintering tool Micro-Punch for its sintering press, which can independently press each component on the substrate, chip, chip with a specific pressure (thermistor, IGBT, MOSFET). According to AMX, the Micro-Punch tool ensures uniform pressure and eliminates the following high-value problems: mold breakage, tilt, delamination, and voids. The Micro-Punch tool has no restrictions on the number or placement of chips; it can adapt to any DBC size or configuration, and can independently press the thinnest and smallest molds, even if they are very close to each other.

Pressure sintering

Silver (Ag)/copper (Cu) pressure sintering (see Figure 1) is a heat treatment process applied to powder materials (ie nanoparticles) to provide higher strength, integrity and conductivity. According to AMX, sintering is currently considered the most reliable technology for connecting power electronic components. Silver sinter paste is currently the most widely used material. The melting point is about 960˚C, and the thermal conductivity of silver sintered paste is between 130 and 250 W/(m·K). Silver sinter paste has high adhesion to epoxy resin, can keep components in a fixed position for excellent management, and can generally increase the total output of the process. The next generation requires copper sintering, especially to achieve significant cost savings. Compared with other bonding methods,

• It has the best thermal conductivity (》150 W/(m⋅K)).
• It has the best conductivity.
• It provides the best results in durability tests, even 100 times better than soldered interconnects.
• It shows a higher remelting temperature (>400˚C).

According to AMX, its patented pressure sintering technology allows:

• Sintering silicon and silicon carbide on DBC/AMC and other electroplated substrates or bare copper
• Frame/discrete
• Embedded molds, clips, gaskets, etc.
• Interaction of different materials, surfaces and processes

New applications include multi-level interconnection, integrated modules, component connections, power distribution, UPS conversion and storage, charging stations, inverters, servo motors, radars and sensors.

Talking about power semiconductor sintering chip technology
Figure 1: Schematic diagram of pressure sintering

A new method: Micro-Punch

During the research process, the company obtained an innovation patent, which achieved the best results from the sintering process, as shown in Figure 2. This is the Micro-Punch system, which is completely different from the traditional system and has a significant improvement over the previous system. The first system consists of a single press, which applies the same force to all components. Any difference in thickness of the various components will inevitably cause problems. In other words, if the dough layer is slightly thicker at a certain point, all the force of the press is accurately applied at that point, thereby increasing the pressure disproportionately and increasing the risk of material cracking.

The company introduced a major innovation with the Micro-Punch system: it now uses a dedicated press to apply pressure independently at each point. As a result, the previous problem was eliminated. Alessio Greci, Sales Manager of AMX, said: “AMX patents revolutionized this production area. The competition developed some intermediate and alternative solutions, usually grouping several presses into subgroups, but the MicroPunch system performed well in terms of repeatability. Especially in advanced packaging applications, although the cost of ownership and processing time are the same.”

Talking about power semiconductor sintering chip technology
Figure 2: One of AMX’s patented methods (right) and the classic method (left)

Talking about power semiconductor sintering chip technology
Figure 3: Evolution of AG sintering technology

Maximum customization

According to AMX, the Micro-Punch system can be customized to meet customer needs. In fact, many of them care more about the accuracy and reliability of the solution than its cost. Elimination of material damage is the primary requirement. This requirement is most obvious when various types of electronic components (such as a combination of diodes, MOSFETs and thermistors) are involved in the process. Using Micro-Punch, each presser foot is dedicated to a point (see Figure 4), and the entire system can independently press the thermistor and IGBT.

In addition, according to AMX, Micro-Punch can apply different and independent pressures to various electronic components. In this way, if the customer thinks that the component is more brittle and does not respond well to high pressure, they can reduce the pressure slightly. Therefore, in the design stage and according to the customer’s specifications, it is possible to choose between different pressures and applied components. Therefore, the final production machine is customized to meet the needs of the end user. For example, you can define the pressure ratio between various pistons and specify a parameter that indicates that the pressure of one piston must be twice that of the other piston.

“Obviously, these initially selected parameters can be modified by the customer each time the loop changes,[they]can modify the relationship between the applied pressures from time to time,” Gracie said. He continued, “The Micro-Punch system can handle elements that are very close to each other, because in theory these components can have zero GAP and can move freely while contacting each other. Sintering is currently used in semiconductor applications, such as SiC.”

Talking about power semiconductor sintering chip technology
Figure 4: A single punch allows you to apply pressure individually.

Sintering in the automotive industry

In the past few years, everything in the car has been welded together. AMX also implements pressure sintering methods in the automotive sector, especially for ultra-high power modules. Today, the market requires greater miniaturization and high power, and most of the company’s activities will focus on such applications. There are also implementations of public transport with trains, but they obviously have no space issues. In fact, miniaturization mainly involves the automotive field. Other applications of power modules also involve data centers, uninterruptible power supplies and large power transformers.

Pressure sintering: a set of important parameters

The difference between different sintering procedures is not so much determined by the type of parts to be sintered, as it is determined by the selection and use of the slurry. Customers can choose the paste and workflow to follow. Obviously, some initial parameters are selected a priori, more or less standard. The sintering process requires a temperature of about 250˚C, a pressure of 15 to 25 MPa, and a time of about three minutes. This is the starting point for describing the entire process.

Based on the initial results, some parameters can be adjusted to obtain the best results. Usually, customers check the influence of force or heat, observe how components react to various types of fatigue, and analyze individual parts under a microscope. Usually, these parameters are set by the solder paste manufacturer and fine-tuned one by one during the test. Finally, pressure sintering is a process that allows high-temperature sealing, with high reliability and perfect repeatability, and is currently considered the best solution. Other parameters must be evaluated, such as temperature and thermal expansion coefficient.

Dual feedback system

AMX provides a “dual feedback” option. This is a feature to avoid errors when applying pressure to the components. Control the pressure exerted on two aspects:

• On the press
• At a specific point where the force is applied

A double check using a force sensor evaluates whether the force applied to the press is consistent with the force received by the component. After understanding the entire sintering area, you can calculate the pressure applied from above and the theoretical force constraining the reaction force, and compare it with the sensor output (see Figure 5). In fact, the operator may remove the presser foot for cleaning, and then forget to replace it. In this case, the programmed pressure will be different from the actual pressure applied to the component, resulting in a significant force imbalance. In other words, when the presser foot does not apply the expected force, the system will detect and notify the operator. Several sensors are also used for oxygen concentration and temperature, although seemingly redundant, they are used for safety reasons (for example, the sensor may malfunction). All this information is collected to get a complete overview of the entire process.

Talking about power semiconductor sintering chip technology
Figure 5: In pressure sintering, each press is controlled and completely independent of other presses.