CN105336768B - The packaging technology of highly reliable surface mount glass sealed diode - Google Patents

Abstract

The invention discloses a packaging process of a highly reliable surface-mounted glass-encapsulated diode. The diode includes a glass bulb, a chip inside the glass bulb, and lead-out ends sleeved at both ends of the glass bulb. Solder tab, the lead-out end of the diode and the glass bulb, the lead-out end and the solder tab, and the chip are bonded together through high-temperature metallurgy. The metallurgical bonding structure has the advantages of high reliability, high current impact resistance, small thermal resistance, and a wide operating temperature range (-55°C ~ 125°C), high temperature welding resistance (15 minutes at 550°C, the parameters do not deteriorate) ;The material selection of the product realizes the thermal matching of the product's full working temperature range; Nitrogen is used as the protective gas in the whole process, which is safe in production and no dangerous gas is used; the diodes made have small installation volume, high assembly density and light weight; Simple, easy to achieve batch or large-scale production.

Description

Encapsulation Technology of High Reliable Surface Mounted Glass-encapsulated Diodes

technical field

The invention relates to a packaging process for diodes, in particular to a packaging process for highly reliable surface-mounted glass-sealed diodes, and belongs to the technical field of diode packaging.

Background technique

At present, the small current Schottky diodes used in large quantities are packaged in the form of axial lead glass package, which has large installation volume, heavy weight, and high lead resistance, resulting in increased volume and reduced reliability of the whole machine, which is no longer suitable for high-precision diodes. High-density, high-performance, and high-reliability requirements for weaponry systems. The surface-mounted low-current Schottky diode is a metal silicide-silicon contact semiconductor device made of a metal silicide (such as MoSi2) as the positive electrode and an N-type semiconductor as the negative electrode, using the potential barrier formed on the contact surface of the two. The chip barrier of the device is a metal silicide-silicon contact Schottky barrier, which improves the forward characteristics of the device; at the same time, the chip adopts a guard ring and a multi-layer metallization structure, which improves the reverse withstand voltage and reverse characteristics of the device and thermal fatigue resistance. Surface mount glass-encapsulated low-current Schottky diode series have the characteristics of forward voltage drop, fast reverse recovery, small size, light weight, high efficiency, etc. They are mainly used as switches and rectifier diodes in switching power supply, high-frequency rectification and other circuits , the performance of the product directly affects the running speed and work efficiency of the main power supply system, and plays a vital role in improving the performance of the whole machine and optimizing the system design. The product can be widely used in computers, radars, communication transmitters, Aerospace vehicles, instrumentation, etc.

At present, the connection method between the chip and the lead-out of the surface-mounted glass-encapsulated diode is crimping, that is, the use of external force (such as the deformation pressure of the shrapnel, the shrinkage force of the high-temperature deformation of the glass) to realize the mechanical contact between the chip and the lead-out. Low reliability, can not meet the requirements of long-term reliability.

Contents of the invention

Aiming at the defects of the prior art, the present invention provides a packaging process for highly reliable surface-mounted glass-encapsulated diodes. The diodes made by the packaging process have high reliability, wide operating temperature, high-temperature welding resistance, and good thermal matching.

In order to solve the technical problem, the technical solution adopted in the present invention is: a packaging process for a highly reliable surface-mounted glass-encapsulated diode, the diode includes a glass bulb, a chip located in the glass bulb, and a chip set at both ends of the glass bulb. There is a soldering piece between the terminal and the chip, which is characterized in that the terminal of the diode is bonded to the glass bulb, the terminal and the soldering piece, and the chip through a high-temperature metallurgical process.

Further, the packaging process of the high-reliability surface-mounted glass-encapsulated diode of the present invention includes the following steps:

1) Prepare a chip with a chip thickness of 210μm±50μm;

2), use the mold to assemble the chip, solder piece, terminal and glass bulb together;

3) Nitrogen sintering, open the sintering furnace, set the working temperature and nitrogen flow rate according to the process conditions, the nitrogen flow rate is 1000ml/min±10ml/min, when the temperature of the furnace mouth rises to 300℃±20℃, the semi-finished device will be installed Put the mold in the furnace mouth to preheat for at least 10 minutes; after the furnace temperature rises to 620°C±20°C, push the mold into the constant temperature zone, and pull the mold to the furnace mouth to cool for 30 minutes after reaching the predetermined constant temperature time, and finally take out the mold and let it cool down to room temperature naturally. Complete the packaging to achieve good metallurgical bonding of the leads, solder pads and chips, and the sealing of the glass bulb and the leads.

Further, in the above constant temperature process, the constant temperature time is 10-30min.

Further, the solder sheet is silver-copper-tin sheet, and the weight ratio of silver-copper-tin is 6:3:1.

Further, the chip is a chip plated with silver on the surface and the barrier can withstand high temperature sintering above 600°C.

Further, the material of the lead-out end is Dumet wire, the outer surface of the lead-out end is copper, and the inside is iron-nickel alloy.

Beneficial effects of the present invention: the packaging process of the present invention utilizes the high-temperature metallurgical process to bond the lead-out end of the diode with the glass bulb, the lead-out end, the solder piece, and the chip, and the metallurgical bonding structure has high reliability and high current shock resistance , the advantages of small thermal resistance, and a wide operating temperature range (-55 ° C ~ 125 ° C), high temperature welding (15 minutes at 550 ° C environment, the parameters do not deteriorate); product selection to achieve the product's full operating temperature range of heat Matching; Nitrogen is used as the protective gas in the whole process, which is safe in production and no dangerous gas is used; the installed diode is small in size, high in assembly density, and light in weight; the process is simple to operate, and it is easy to realize batch or large-scale production.

Description of drawings

Fig. 1 is the structural representation of the surface-mounted glass-encapsulated diode of the present invention;

Fig. 2 is the schematic structural view when the surface mount glass-encapsulated diode of the present invention is packaged;

Fig. 3 is a temperature curve diagram during the encapsulation process;

In the figure: 1. Glass bulb, 2. Chip, 3. Lead terminal, 4. Solder tab.

Detailed ways

The present invention will be further described and defined below in conjunction with the accompanying drawings and specific embodiments.

As shown in Figure 1, it is a schematic structural diagram of the surface-mounted glass-encapsulated diode described in this embodiment, including a glass bulb 1, a chip 2 located in the middle of the glass bulb 1, a lead-out terminal 3 sleeved at both ends of the glass bulb 1, and a The solder tab 4 between the terminal 3 and the chip 2, in this embodiment, the glass bulb 1 and the terminal 3, the glass bulb 1 and the solder tab 4, and the chip 2 are bonded together through a pyrometallurgical bonding process.

In this implementation, the packaging process of the high-reliability surface-mounted glass-encapsulated diode includes the following steps:

1) Prepare a chip with a chip thickness of 210μm±50μm;

2) Assemble the chip, solder piece, terminal and glass bulb together with a mold, as shown in Figure 2;

3) Nitrogen sintering, open the sintering furnace, set the working temperature and nitrogen flow rate according to the process conditions, the nitrogen flow rate is 1000ml/min±10ml/min, when the temperature of the furnace mouth rises to 300℃±20℃, the semi-finished device will be installed Put the mold in the furnace mouth to preheat for at least 10 minutes; after the furnace temperature rises to 620°C±20°C, push the mold into the constant temperature zone, keep the temperature for 20 minutes, pull the mold to the furnace mouth to cool for 30 minutes, and finally take out the mold and let it cool naturally to room temperature to complete the packaging , to achieve good metallurgical bonding of the terminal, the solder piece and the chip, and the sealing of the glass bulb and the terminal. The temperature change curve during the sintering process is shown in Figure 3.

In this embodiment, the solder sheet is a silver-copper-tin sheet, and the weight ratio of silver-copper-tin is 6:3:1. The surface of the chip is silver, and its potential barrier can withstand high temperature sintering above 600°C. The material of the lead-out end is Dumet wire, the outer surface of the lead-out end is copper, and the inside is iron-nickel alloy.

The high-reliability surface-mounted glass-encapsulated diode described in this embodiment has the advantages of high current impact resistance, reliable connection, and small thermal resistance. When packaging, it is necessary to comprehensively consider factors such as the high temperature resistance of the Schottky chip, chip metallization, glass bulb material, and lead-out material to meet the requirements of thermal matching, mechanical strength, and current transmission. Therefore, in order to achieve the electrical parameter requirements and reliable connection of the product, the parameter characteristics and structural characteristics of the product should be considered.

The glass bulb adopts GLASS8532 type glass bulb, the temperature of the softening point of the glass bulb is 560°C, and the maximum temperature of the glass bulb's working point is 760°C; the solder piece is made of silver-copper-tin sheet, which appears liquid at about 600°C and completely liquid at 720°C, with a density of 9.57g/cc, so the high-temperature bonding temperature is determined to be 620°C±20°C. The material of the lead-out end is Dumet wire, the outer surface of the lead-out end is copper, and the inside is iron-nickel alloy. The surface of the chip is silver, and its potential barrier can withstand high temperature sintering above 600°C.

The main raw materials that make up the diode are lead-out terminals, glass bulbs, chips, and solder pads (the main component is Ag). The thermal expansion coefficients of various materials are shown in Table 1. The thermal expansion table of raw materials, and the thickness of the silicon layer of the product chip is determined according to the expansion coefficient of the material. x and the thickness of the silver layer of the chip and the thickness of the solder piece y, generally take the thickness x of the silicon layer as 0.21mm, and the thickness of the silver layer of the chip as 0.01mm, according to the formula (x+0.01+y)*8.0×10 ^-6 =x*4.2×10 ^-6 +(0.01+y)*18.9×10 ^-6 Calculate the thickness y of the solder piece to achieve thermal matching.

According to the structural characteristics of the product, the thermal matching between the glass bulb and the lead-out end of the Dumet wire is mainly considered. As can be seen from the above table, the thermal expansion coefficients of the two materials are similar, and the thermal matching is good. Therefore, we use a glass bulb that matches the expansion coefficient of Dumet wire, and sinter it in a nitrogen protective atmosphere to ensure long-term reliability of the product.

After the product is sintered and formed, it has done many tests related to thermal matching, including glass cracking resistance test, thermal shock test (liquid-liquid), 500 times of temperature shock test and other environmental mechanical tests, which proves the high reliability of the product Meet the national military standard requirements.

The above is only a further description and explanation of the principle of the present invention, so that those skilled in the art can better understand the present invention, it should be understood that the following content only serves to explain and illustrate, and does not have a substantial impact on the present invention. The content is limited, and all improvements within the idea of the present invention should be within the protection scope of the present invention.

Claims (4)

1. A packaging process for a surface-mounted glass-sealed diode, said diode comprising a glass bulb, a chip positioned in the glass bulb, lead-outs sleeved at both ends of the glass-bulb, soldering tabs are provided between the lead-out and the chip, and It is characterized in that: the leading end of the diode and the glass bulb are bonded together through a high-temperature metallurgical process, and the leading end is bonded with the solder piece and the chip through a high-temperature metallurgical process. The high-temperature metallurgical bonding temperature is 620 ° C ± 20 ° C; specifically includes the following step: 1) To prepare the chip, set the thickness of the silicon layer of the chip to x, the unit is mm, the thickness of the silver layer of the chip is 0.01mm, and the thickness of the chip is 210μm±50μm, according to the formula (x+0.01+y)*8.0×10 ^-6 =x*4.2 ×10 ^-6 +(0.01+y)*18.9×10 ^-6 Calculate the thickness y of the solder sheet, in mm, to achieve thermal matching, the solder sheet is silver-copper-tin sheet, and the weight ratio of silver-copper-tin is 6:3:1 ; 2), use the mold to assemble the chip, solder piece, terminal and glass bulb together; 3) Nitrogen sintering, open the sintering furnace, set the working temperature and nitrogen flow rate according to the process conditions, the nitrogen flow rate is 1000ml/min±10ml/min, when the temperature of the furnace mouth rises to 300℃±20℃, the semi-finished device will be installed Put the mold in the furnace mouth to preheat for at least 10 minutes; after the furnace temperature rises to 620°C±20°C, push the mold into the constant temperature zone, and pull the mold to the furnace mouth to cool for 30 minutes after reaching the predetermined constant temperature time, and finally take out the mold and let it cool down to room temperature naturally. Complete the packaging, realize the metallurgical bonding of the terminal, the solder piece and the chip, and the sealing of the glass bulb and the terminal. 2. The packaging process of surface mount glass-encapsulated diodes according to claim 1, characterized in that: the constant temperature time is 10-30 minutes. 3. The packaging process of surface-mounted glass-encapsulated diodes according to claim 2, wherein the chip is a silver-plated chip whose barrier can withstand high temperature sintering above 600°C. 4. The packaging process of surface mount glass-encapsulated diodes according to claim 3, characterized in that: the material of the lead-out end is Dumet wire, the outer surface of the lead-out end is copper, and the inside is iron-nickel alloy.