Classification of semiconductor devices and their application in energy converters and information transmission. Semiconductor device housing for surface mounting Features of mounting semiconductor devices and microcircuits

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To avoid damage to semiconductor devices during installation, it is necessary to ensure that their terminals are stationary near the housing. To do this, bend the leads at a distance of at least 3...5 mm from the body and perform soldering with low-temperature POS-61 solder at a distance of at least 5 mm from the device body, ensuring heat removal between the body and the soldering point. If the distance from the soldering point to the body is 8...10 mm or more, it can be done without additional heat sink (within 2...3 s).

Re-soldering during installation and replacement of individual parts in circuits with semiconductor devices should be done with the power turned off using a soldering iron with a grounded tip. When connecting a transistor to a circuit under voltage, you must first connect the base, then the emitter, and then the collector. Disconnecting the transistor from the circuit without removing the voltage is performed in the reverse order.

To ensure normal operation Semiconductor devices at full power require the use of additional heat sinks. Finned radiators made of red copper or aluminum are used as heat sinks, which are placed on the devices. When designing circuits with a wide temperature range of operation, it should be taken into account that as the temperature increases, not only does permissible power dissipation of many types of semiconductor devices, but also permissible voltages and currents of transitions.

Operation of semiconductor devices should be carried out only within the range of required operating temperatures, and the relative humidity should be up to 98% at a temperature of 40 ° C; atmospheric pressure - from 6.7 10 2 to 3 10 5 Pa; vibration with acceleration up to 7.5 g in the frequency range 10...600 Hz; repeated impacts with acceleration up to 75g; linear accelerations up to 25g.

Increasing or decreasing the above parameters negatively affects the performance of semiconductor devices. Thus, a change in the operating temperature range causes cracking of semiconductor crystals and changes in the electrical characteristics of devices. In addition, under the influence of high temperatures, drying and deformation of the protective coatings, release of gases and melting of the solder occur. High humidity promotes corrosion of housings and terminals due to electrolysis. Low pressure causes a decrease in breakdown voltage and a deterioration in heat transfer. Changes in the acceleration of impacts and vibration lead to the appearance of mechanical stress and fatigue in structural elements, as well as mechanical damage (up to separation of leads), etc.

To protect against the effects of vibrations and acceleration, the structure with semiconductor devices must have shock absorption, and to improve moisture resistance it must be coated with a protective varnish.

Assembly and sealing of microcircuits and semiconductor devices includes 3 main operations: attaching the crystal to the base of the package, connecting the leads, and protecting the crystal from the external environment. The stability of electrical parameters and the reliability of the final product depend on the quality of assembly operations. In addition, the choice of assembly method affects the total cost of the product.

Attaching the crystal to the base of the case

The main requirements when attaching a semiconductor crystal to the base of the package are high reliability of the connection, mechanical strength and, in some cases, a high level of heat transfer from the crystal to the substrate. The connection operation is carried out using soldering or gluing.

Adhesives for mounting crystals can be divided into two categories: electrically conductive and dielectric. Adhesives consist of an adhesive binder and a filler. To ensure electrical and thermal conductivity, silver is usually added to the adhesive in the form of powder or flakes. To create heat-conducting dielectric adhesives, glass or ceramic powders are used as filler.

Soldering is carried out using conductive glass or metal solders.

Glass solders are materials composed of metal oxides. They have good adhesion to a wide range of ceramics, oxides, semiconductor materials, metals and are characterized by high corrosion resistance.

Soldering with metal solders is carried out using solder samples or pads of a given shape and size (pre-forms) placed between the crystal and the substrate. In mass production, specialized solder paste is used for mounting crystals.

Connecting leads

The process of connecting the leads of the crystal to the base of the package is carried out using wire, tape or rigid leads in the form of balls or beams.

Wire installation is carried out by thermocompression, electric contact or ultrasonic welding using gold, aluminum or copper wire/tapes.

Wireless installation is carried out using the “inverted crystal” technology (Flip-Chip). Hard contacts in the form of beams or solder balls are formed on the chip during the metallization process.

Before applying solder, the surface of the crystal is passivated. After lithography and etching, the contact pads of the crystal are additionally metalized. This operation is carried out to create a barrier layer, prevent oxidation and improve wettability and adhesion. After this, conclusions are formed.

Beams or solder balls are formed by electrolytic or vacuum deposition, filling with ready-made microspheres, or screen printing. The crystal with the formed leads is turned over and mounted on the substrate.

Protecting the crystal from environmental influences

The characteristics of a semiconductor device are largely determined by the state of its surface. The external environment has a significant impact on the surface quality and, accordingly, on the stability of device parameters. this effect changes during operation, so it is very important to protect the surface of the device to increase its reliability and service life.

Protection of the semiconductor crystal from the influence of the external environment is carried out at the final stage of assembling microcircuits and semiconductor devices.

Sealing can be carried out using a housing or in an open-frame design.

Housing sealing is carried out by attaching the housing cover to its base using soldering or welding. Metal, metal-glass and ceramic cases provide vacuum-tight sealing.

The cover, depending on the type of case, can be soldered using glass solders, metal solders or glued with glue. Each of these materials has its own advantages and is selected depending on the tasks being solved.

For unpackaged protection of semiconductor crystals from external influences, plastics and special casting compounds are used, which can be soft or hard after polymerization, depending on the tasks and materials used.

Modern industry offers two options for filling crystals with liquid compounds:

Filling with medium viscosity compound (glob-top, Blob-top)
Creating a frame from a high-viscosity compound and filling the crystal with a low-viscosity compound (Dam-and-Fill).

The main advantage of liquid compounds over other methods of crystal sealing is the flexibility of the dosing system, which allows the use of the same materials and equipment for various types and crystal sizes.

Polymer adhesives are distinguished by the type of binder and the type of filler material.

Binding material

Organic polymers used as adhesives can be divided into two main categories: thermosets and thermoplastics. All of them are organic materials, but

differ significantly in chemical and physical properties.

In thermosets, when heated, polymer chains are irreversibly cross-linked into a rigid three-dimensional network structure. The bonds that arise in this case make it possible to obtain high adhesive ability of the material, but at the same time maintainability is limited.

Thermoplastic polymers do not cure. They retain the ability to soften and melt when heated, creating strong elastic bonds. This property allows thermoplastics to be used in applications where maintainability is required. The adhesive ability of thermoplastic plastics is lower than that of thermosets, but in most cases it is quite sufficient.

The third type of binder is a mixture of thermoplastics and thermosets, combining

advantages of two types of materials. Their polymer composition is an interpenetrating network of thermoplastic and thermoplastic structures, which allows them to be used to create high-strength repairable joints at relatively low temperatures (150 o C - 200 o C).

Each system has its own advantages and disadvantages. One of the limitations of using thermoplastic pastes is the slow removal of solvent during the reflow process. Previously, joining components using thermoplastic materials required a process of applying a paste (maintaining flatness), drying to remove solvent, and then mounting the chip onto the substrate. This process eliminated the formation of voids in the adhesive material, but increased the cost and made it difficult to use this technology in mass production.

Modern thermoplastic pastes have the ability to evaporate the solvent very quickly. This property allows them to be applied by dosing using standard equipment, and the crystal to be installed on the paste that has not yet dried. This is followed by a rapid low-temperature heating step, during which the solvent is removed and adhesive bonds are created after reflow.

For a long time, there have been difficulties in creating highly thermally conductive adhesives based on thermoplastics and thermosets. These polymers did not allow increasing the content of thermally conductive filler in the paste, since good adhesion required a high level of binder (60-75%). For comparison: in inorganic materials the proportion of binder could be reduced to 15-20%. Modern polymer adhesives (Diemat DM4130, DM4030, DM6030) do not have this drawback, and the content of thermally conductive filler reaches 80-90%.

Filler

The type, shape, size and amount of filler play a major role in creating a thermally and electrically conductive adhesive. Silver (Ag) is used as a filler as a chemically resistant material with the highest thermal conductivity coefficient. Modern pastes contain

silver in the form of powder (microspheres) and flakes (scales). The exact composition, quantity and size of particles are experimentally selected by each manufacturer and largely determine the thermal, electrically conductive and adhesive properties of the materials. In applications where a dielectric with heat-conducting properties is required, ceramic powder is used as a filler.

When choosing an electrically conductive adhesive, consider the following factors:

Thermal and electrical conductivity of the glue or solder used
Permissible technological installation temperatures
Temperatures of subsequent technological operations
Mechanical strength of the connection
Automation of the installation process
Maintainability
Cost of installation operation

In addition, when choosing an adhesive for installation, you should pay attention to the elastic modulus of the polymer, the area and difference in the thermal expansion coefficient of the components being connected, as well as the thickness of the adhesive seam. The lower the elastic modulus (the softer the material), the larger the areas of the components and the greater the difference in the CTE of the components being connected and the thinner the adhesive seam is permissible. A high elastic modulus limits the minimum thickness of the adhesive joint and the dimensions of the components to be connected due to the possibility of large thermomechanical stresses.

When deciding on the use of polymer adhesives, it is necessary to take into account some technological features of these materials and the components being connected, namely:

die (or component) length determines the load on the adhesive joint after cooling the system. During soldering, the crystal and substrate expand in accordance with their CTE. For crystals large size soft (low modulus) adhesives or CTE-matched chip/substrate materials must be used. If the CTE difference is too great for a given chip size, the bond may be broken, causing the chip to delaminate from the substrate. For each type of paste, the manufacturer, as a rule, gives recommendations on the maximum crystal sizes for certain values of the crystal/substrate CTE difference;

width of the die (or components to be connected) determines the distance that the solvent contained in the adhesive travels before leaving the adhesive line. Therefore, the crystal size must also be taken into account for proper solvent removal;

metallization of the crystal and substrate (or components to be connected) not required. Typically, polymer adhesives have good adhesion to many non-metallized surfaces. Surfaces must be cleaned of organic contaminants;

thickness of the adhesive seam. For all adhesives containing a thermally conductive filler, there is a minimum adhesive joint thickness dx (see figure). A joint that is too thin will not have enough bonding agent to cover all of the filler and form bonds to the surfaces being joined. In addition, for materials with a high elastic modulus, the thickness of the seam may be limited by different CTE for the materials being joined. Typically, for adhesives with a low elastic modulus, the recommended minimum seam thickness is 20-50 µm, for adhesives with a high elastic modulus 50-100 µm;

the lifetime of the adhesive before installing the component. After applying the adhesive, the solvent from the paste begins to gradually evaporate. If the glue dries, the materials being joined will not be wetted or bonded. For small components, where the ratio of surface area to volume of adhesive applied is large, the solvent evaporates quickly and the time after application before installing the component must be minimized. As a rule, the lifetime before component installation for various adhesives varies from tens of minutes to several hours;

lifetime before thermal curing of the adhesive is counted from the moment the component is installed until the entire system is placed in the oven. With a long delay, delamination and spreading of the glue may occur, which negatively affects the adhesion and thermal conductivity of the material. The smaller the component size and the amount of glue applied, the faster it can dry. The lifetime before thermal curing of the adhesive can vary from tens of minutes to several hours.

Selection of wire, tapes

The reliability of a wire/tape connection greatly depends on the correct choice of wire/tape. The main factors determining the conditions for using a particular type of wire are:

Housing type. Sealed enclosures use only aluminum or copper wire because gold and aluminum form brittle intermetallic compounds at high sealing temperatures. However, for non-sealed housings, only gold wire/tape is used because this type the housing does not provide complete insulation from moisture, which leads to corrosion of aluminum and copper wire.

Wire/Ribbon Sizes(diameter, width, thickness) thinner conductors are required for circuits with small pads. On the other hand, the higher the current flowing through the connection, the larger the cross-section of the conductors must be provided

Tensile strength. Wire/strips are subject to external mechanical stress during subsequent stages and during use, so the higher the tensile strength, the better.

Elongation. An important characteristic when choosing wire. Too high elongation values make it difficult to control loop formation when creating a wire connection.

Choosing a crystal protection method

Sealing of microcircuits can be carried out using a housing or in an open-frame design.

When choosing the technology and materials to be used at the sealing stage, the following factors should be taken into account:

Required level of housing tightness
Permissible technological sealing temperatures
Chip operating temperatures
Presence of metallization of connected surfaces
Possibility of using flux and special installation atmosphere
Automation of the sealing process
Cost of sealing operation

The article provides an overview of the technologies and materials used to form pin leads on semiconductor wafers in the production of microcircuits.

Electrical installation of radio components must ensure reliable operation of equipment, instruments and systems under the conditions of mechanical and climatic influences specified in the technical specifications for this type REA. Therefore, when installing semiconductor devices (SD), integrated circuits (IC) radio components on printed circuit boards or equipment chassis, the following conditions must be met:

reliable contact of the powerful PCB case with the heat sink (radiator) or chassis;
necessary air convection near radiators and elements that emit large number warmth;
removal of semiconductor elements from circuit elements that emit a significant amount of heat during operation;
protection of installations located near removable elements from mechanical damage during operation;
in the process of preparing and carrying out electrical installation of PP and IC, mechanical and climatic influences on them should not exceed the values specified in the technical specifications;
When straightening, forming and cutting PP and IC leads, the lead area near the housing must be secured so that no bending or tensile forces arise in the conductor. Equipment and devices for forming leads must be grounded;
the distance from the PCB or IC body to the start of bending of the lead must be at least 2 mm, and the bending radius for a lead diameter of up to 0.5 mm should be at least 0.5 mm, with a diameter of 0.6-1 mm - at least 1 mm, with a diameter over 1 mm - at least 1.5 mm.

During installation, transportation and storage of PCBs and ICs (especially microwave semiconductor devices), it is necessary to ensure their protection from the effects of static electricity. To do this, all installation equipment, tools, control and measuring equipment are reliably grounded. To remove static electricity from the body of an electrician, use grounding bracelets and special clothing.

To remove heat, the output section between the PCB (or IC) body and the soldering point is clamped with special tweezers (heat sink). If the solder temperature does not exceed 533 K ± 5 K (270 °C), and the soldering time does not exceed 3 s, soldering of the PP (or IC) leads is carried out without a heat sink or group soldering is used (wave solder, immersion in molten solder, etc.) .

Cleaning of printed circuit boards (or panels) from flux residues after soldering is carried out with solvents that do not affect the markings and material of PCB (or IC) housings.

When installing ICs with rigid radial leads into metallized holes of a printed circuit board, the protruding part of the leads above the board surface at the soldering points should be 0.5-1.5 mm. Installation of the IC in this way is carried out after trimming the leads (Fig. 55). To facilitate dismantling, it is recommended to install ICs on printed circuit boards with gaps between their cases.

Rice. 55. Forming rigid radial IC leads:
1 - molded leads, 2 - leads before molding

Integrated circuits in packages with soft planar leads are installed on board pads without mounting holes. In this case, their location on the board is determined by the shape of the contact pads (Fig. 56).

Rice. 56. Installation of ICs with flat (planar) leads on a printed circuit board:
1 - contact pad with key, 2 - housing, 3 - board, 4 - output

Examples of molding ICs with planar leads are shown in Fig. 57.

Rice. 57. Forming flat (planar) IC leads when installed on a board without a gap (i), with a gap (b)

Installation and fastening of PP and IC, as well as mounted radio components on printed circuit boards must provide access to them and the ability to replace them. To cool the ICs, they should be placed on printed circuit boards taking into account the movement of air flow along their bodies.

For electrical installation of PCBs and small-sized radio components, they are first installed on mounting fittings (petals, pins, etc.) and the terminals are mechanically secured to it. To solder the field connection, acid-free flux is used, the residues of which are removed after soldering.

Radio components are attached to the mounting fittings either mechanically on their own terminals, or additionally with a clamp, bracket, holder, filling with compound, mastic, glue, etc. In this case, the radio components are fixed so that they do not move due to vibration and shock (shaking). Recommended types of fastening of radio components (resistors, capacitors, diodes, transistors) are shown in Fig. 58.

Rice. 58. Installation of radio components on mounting fixtures:
a, b - resistors (capacitors) with flat and round leads, c - capacitor ETO, d - diodes D219, D220, d - powerful diode D202, f - triodes MP-14, MP-16, g - powerful triode P4; 1 - body, 2 - petal, 3 - output, 4 - radiator, 5 - wires, 6 - insulating tube

Mechanical fastening of the terminals of radio components to the mounting fittings is carried out by bending or twisting them around the fittings and then crimping them. In this case, breaking the terminal during compression is not allowed. If there is a hole in the contact post or petal, the lead of the radio component is mechanically secured before soldering by threading it through the hole and bending it half or a full turn around the petal or post, followed by crimping. The excess output is removed with side cutters, and the attachment point is crimped with pliers.

As a rule, methods for installing radio components and fastening their terminals are specified in the assembly drawing for the product.

To reduce the distance between the radio component and the chassis, insulating tubes are placed on their housings or terminals, the diameter of which is equal to or slightly less than the diameter of the radio component. In this case, the radio components are placed close to each other or to the chassis. Insulating tubes placed on the terminals of radio components eliminate the possibility of short circuits with adjacent conductive elements.

The length of the mounting leads from the soldering point to the body of the radio component is given in the specifications and, as a rule, specified in the drawing: for discrete radio components it must be at least 8 mm, and for PCBs - at least 15 mm. The length of the lead from the housing to the bend of the radio component is also specified in the drawing: it must be at least 3 mm. The leads of radio components are bent using a template, fixture or special tool. Moreover, the internal bending radius must be no less than twice the diameter or thickness of the lead. Rigid terminals of radio components (PEV resistances, etc.) are not allowed to be bent during installation.

Radio components selected when setting up or adjusting the device should be soldered without mechanical fastening to the full length of their leads. After selecting their values and adjusting the device, the radio components must be soldered to the reference points with the pins mechanically secured.

The rapid development and expansion of areas of application of electronic devices is due to the improvement of the element base, the basis of which is semiconductor devices. Therefore, to understand the functioning of electronic devices, it is necessary to know the structure and operating principle of the main types of semiconductor devices.

Transistors

A transistor is a semiconductor device designed to amplify, generate and convert electrical signals, as well as switch electrical circuits.

A distinctive feature of the transistor is the ability to amplify voltage and current - the voltages and currents acting at the input of the transistor lead to the appearance of significantly higher voltages and currents at its output.

With the spread of digital electronics and pulse circuits, the main property of a transistor is its ability to be in open and closed states under the influence of a control signal.

The transistor got its name from the abbreviation of two English words tran(sfer) (re)sistor - controlled resistor. This name is not accidental, since under the influence of the input voltage applied to the transistor, the resistance between its output terminals can be adjusted within a very wide range.

The transistor allows you to regulate the current in the circuit from zero to the maximum value.

Transistor classification:

Based on the operating principle: field (unipolar), bipolar, combined.

According to the value of power dissipation: low, medium and high.

According to the limiting frequency value: low-, medium-, high- and ultra-high-frequency.

According to the operating voltage: low and high voltage.

By functional purpose: universal, amplifier, key, etc.

By design: unframed and in cased design, with rigid and flexible leads.

Depending on the functions performed, transistors can operate in three modes:

1) Active mode - used to amplify electrical signals in analog devices. The resistance of the transistor changes from zero to the maximum value - they say the transistor “opens slightly” or “closes slightly”.

2) Saturation mode - the transistor resistance tends to zero. In this case, the transistor is equivalent to a closed relay contact.

3) Cut-off mode - the transistor is closed and has a high resistance, i.e. it is equivalent to an open relay contact.

Saturation and cutoff modes are used in digital, pulse and switching circuits.

Bipolar transistor is a semiconductor device with two p-n junctions and three terminals that provides power amplification of electrical signals.

In bipolar transistors, the current is caused by the movement of charge carriers of two types: electrons and holes, which determines their name.

On diagrams, transistors can be depicted both in a circle and without it (Fig. 3). The arrow indicates the direction of current flow in the transistor.

Figure 3 - Graphic symbols n-p-n transistors(a) and p-n-p (b)

The basis of the transistor is a semiconductor wafer, in which three sections are formed with alternating types of conductivity - electronic and hole. Depending on the alternation of layers, two types of transistor structure are distinguished: n-p-n (Fig. 3, a) and p-n-p (Fig. 3, b).

Emitter (E) - a layer that is a source of charge carriers (electrons or holes) and creates a device current;

Collector (K) – a layer that receives charge carriers coming from the emitter;

Base (B) - the middle layer that controls the transistor current.

When a transistor is connected to an electrical circuit, one of its electrodes is the input (the source of the input alternating signal is turned on), the other is the output (the load is turned on), and the third electrode is common with respect to the input and output. In most cases, a common emitter circuit is used (Figure 4). A voltage of no more than 1 V is supplied to the base, and more than 1 V to the collector, for example +5 V, +12 V, +24 V, etc.

Figure 4 – Connection circuits for a bipolar transistor with a common emitter

The collector current occurs only when the base current Ib flows (determined by Ube). The more Ib, the more Ik. Ib is measured in units of mA, and the collector current is measured in tens and hundreds of mA, i.e. IbIk. Therefore, when an alternating signal of small amplitude is supplied to the base, small Ib will change, and large Ik will change in proportion to it. When a load resistance is connected to the collector circuit, a signal will be emitted on it, repeating the shape of the input, but with a larger amplitude, i.e. amplified signal.

To the number extremely acceptable parameters transistors primarily include: the maximum permissible power dissipated at the collector Pk.max, the voltage between the collector and the emitter Uke.max, the collector current Ik.max.

To increase the maximum parameters, transistor assemblies are produced, which can number up to several hundred parallel-connected transistors enclosed in one housing.

Bipolar transistors are now used less and less, especially in switching power technology. Their place is taken MOSFET field effect transistors and combined IGBT transistors, which have undoubted advantages in this area of electronics.

In field-effect transistors, the current is determined by the movement of carriers of only one sign (electrons or holes). Unlike bipolar ones, the transistor current is controlled by an electric field, which changes the cross-section of the conducting channel.

Since there is no current flow in the input circuit, the power consumption from this circuit is practically zero, which is undoubtedly an advantage of the field-effect transistor.

Structurally, the transistor consists of an n- or p-type conducting channel, at the ends of which there are areas: a source that emits charge carriers and a drain that receives charge carriers. The electrode that serves to regulate the cross-section of the channel is called a gate.

Field effect transistor is a semiconductor device that regulates the current in a circuit by changing the cross-section of the conductive channel.

There are field-effect transistors with a gate in p-n form transition and with an insulated gate.

Field-effect transistors with an insulated gate have an insulating layer of dielectric between the semiconductor channel and the metal gate - MOS transistors (metal - dielectric - semiconductor), a special case - silicon oxide - MOS transistors.

An MOS transistor with a built-in channel has an initial conductivity, which in the absence of an input signal (Uzi = 0) is approximately half of the maximum. In MOS transistors with an induced channel, at voltage Uzi = 0, there is no output current, Ic = 0, since there is initially no conducting channel.

Induced channel MOS transistors are also called MOSFET transistors. They are mainly used as key elements, for example in switching power supplies.

Key elements on MOS transistors have a number of advantages: the signal circuit is not galvanically connected to the control source, the control circuit does not consume current, and they have bidirectional conductivity. Field effect transistors, unlike bipolar ones, are not afraid of overheating.

Read more about transistors here:

Thyristors

A thyristor is a semiconductor device that operates in two stable states - low conductivity (thyristor closed) and high conductivity (thyristor open). Structurally, the thyristor has three or more p-n junctions and three outputs.

In addition to the anode and cathode, the thyristor design provides a third terminal (electrode), which is called the control terminal.

The thyristor is designed for contactless switching (switching on and off) of electrical circuits. They are characterized by high speed and the ability to switch currents of very significant magnitude (up to 1000 A). They are gradually being replaced by switching transistors.

Figure 5 - Conventional graphic designation of thyristors

Dynistors (two-electrode)- like conventional rectifier diodes, they have an anode and a cathode. With an increase in forward voltage at a certain value Ua = Uon, the dinistor opens.

Thyristors (thyristors - three-electrode)- have an additional control electrode; Uon is changed by the control current flowing through the control electrode.

To transfer the thyristor to the closed state, it is necessary to apply a reverse voltage (- to the anode, + to the cathode) or reduce the forward current below a value called the holding current Ihold.

Lockable thyristor– can be switched to the closed state by applying a control pulse of reverse polarity.

Thyristors: principle of operation, designs, types and methods of inclusion

Triacs (symmetrical thyristors)- conduct current in both directions.

Thyristors are used as contactless switches and controlled rectifiers in automation devices and electric current converters. In alternating and pulsed current circuits, you can change the open time of the thyristor, and therefore the time the current flows through the load. This allows you to regulate the power delivered to the load.

Usage: in the field of manufacturing semiconductor devices by flux-free soldering in air without the use of protective environments, it can be used in the assembly of Schottky diodes and bipolar transistors by soldering semiconductor crystals to cases with lead-based solders. The essence of the invention: a method for assembling semiconductor devices is that a filter and alloying element is placed on the base of the housing, on which a sample of solder and a crystal are placed, and the cassette with the assembled devices is loaded into a conveyor hydrogen oven at a soldering temperature of 370°C. What is new in the method is that semiconductor crystals with solder on the collector side are fixed in an inverted position in the cells of a vacuum suction cup and combined with the contact pads of device housings, and heating to soldering temperature is carried out in air with a current pulse through V-shaped electrodes, which are rigidly fixed in bracket, electrically connected in series with each other and located differentially above each crystal, and at the moment of solder melting, a vacuum suction cup with crystals is exposed to ultrasonic vibrations in a direction parallel to the solder seam, while pressure on each crystal is exerted by the mass of the device body and the bracket with electrodes. The technical result of the invention is to increase the reliability of semiconductor devices by reducing the heating temperature when soldering the surface of a crystal with structures, improving the wetting of joined surfaces with solder, and increasing the productivity of assembly operations due to group soldering of crystals to packages. 2 ill.

The invention relates to the manufacture of semiconductor devices by flux-free soldering in air without the use of protective environments. It can be used in assembling Schottky diodes and bipolar transistors by soldering semiconductor chips to packages with lead-based solders. There are various ways soldering semiconductor crystals to the body. There is a known method for assembling high-power transistors using the cassette method, in which the leg of the transistor is placed on guides in the cassette, and a sample of solder is placed between the crystal and the body, while soldering is carried out in a conveyor oven with a reducing environment without the use of fluxes. The cassette ensures precise orientation of the crystal relative to the device leg and prevents its displacement during the soldering process. The disadvantage of this known method is the relatively high complexity of manufacturing semiconductor devices. In addition, the presence of oxide films on the surfaces being joined impairs the wetting and capillary flow of solder in the joint gap. There is a known method for soldering microstrip devices with low-temperature solders without the use of fluxes, in which the soldered surfaces are pre-coated with metals or alloys with a melting point close to the melting point of the solder, but higher than it, and at the moment the solder melts, low-frequency vibrations are transmitted to one of the soldered parts. The main disadvantage of this method is the low productivity of this assembly operation, because soldering is carried out discretely. The closest to the claimed method in technical essence is the method of assembling semiconductor devices, which consists in placing a filter and alloying element on the base of the housing, on which a sample of solder and a crystal are then placed. The disadvantage of this method is the high labor intensity of assembly operations and the low percentage of usable devices. Besides, this method does not provide preliminary orientation and fixation of the crystal relative to the body, as a result of which rotation and displacement of the crystal is possible even before the start of the soldering process. Moreover, when soldering it is necessary high temperature heating, which places certain demands on the crystal. Particularly noteworthy is the presence of unsoldered gaps in the soldered seam, which contributes to an increase in the thermal and electrical resistance of the contact of the semiconductor crystal with the housing. Therefore, this method of assembling semiconductor devices is low-efficiency (or ineffective), especially when soldering semiconductor crystals to the packages of power electronics products. The problem that the proposed solution is aimed at is increasing the reliability of semiconductor devices by reducing the heating temperature when soldering the surface of the crystal with structures, improving the wetting of the surfaces to be joined with solder, and increasing the productivity of assembly operations due to group soldering of crystals to packages. This task is achieved by the fact that in the method of assembling semiconductor devices, which consists in placing a filter and alloying element on the base of the housing, on which a sample of solder and a crystal are placed, and the cassette with the assembled devices is loaded into a conveyor hydrogen oven at a soldering temperature of 370 o C , in order to increase the reliability of semiconductor devices by reducing the heating temperature when soldering the surface of crystals with structures, improving the wetting of joined surfaces with solder and increasing the productivity of assembly operations due to group soldering of crystals to cases, semiconductor crystals with solder on the collector side are fixed in an inverted position in the cells vacuum suction cup and combined with the contact pads of the housings, and heating to soldering temperature is carried out in air by a current pulse through V-shaped electrodes, which are rigidly fixed in the bracket, electrically connected in series with each other and located differentially above each crystal, and at the moment of solder melting, vacuum the suction cup with crystals is exposed to ultrasonic vibrations in a direction parallel to the solder seam, while pressure on each crystal is exerted by the mass of the device body and the bracket with electrodes. A comparable analysis with the prototype shows that the proposed method differs from the known one in that, in order to increase the reliability of semiconductor devices by reducing the heating temperature when soldering the surface of the crystal with structures, improving the wetting of the surfaces being connected with solder and increasing the productivity of assembly operations due to group soldering of crystals to packages semiconductor crystals with solder on the collector side are fixed in an inverted position in the cells of a vacuum suction cup and combined with the contact pads of the housings, and heating to soldering temperature is carried out in air by a current pulse through V-shaped electrodes, which are rigidly fixed in the bracket and electrically connected in series with each other and are located differentially above each crystal, and at the moment of solder melting, a vacuum suction cup with crystals is exposed to ultrasonic vibrations in a direction parallel to the soldered seam, while pressure on each crystal is exerted by the mass of the device body and bracket with electrodes. Thus, the proposed method for assembling semiconductor devices meets the “novelty” criterion. Comparison of the proposed method with other known methods from the prior art also did not allow us to identify in them the features claimed in the distinctive part of the formula. The essence of the invention is illustrated by drawings, which schematically depict: FIG. 1 - diagram of assembly and soldering of semiconductor crystals to cases, side view; in fig. 2 - fragment of assembly and soldering of one crystal to the case, side view. The method of assembling semiconductor devices (Figs. 1 and 2) is implemented according to a circuit containing a base 1 connected to a vacuum pump. A vacuum suction cup 2 is fixed to the base, in the cells of which semiconductor crystals 3 with solder 4 are fixed with the collector surface upwards on the soldered surface. Device housings 5 are placed on the crystals. V-shaped electrodes 6 are rigidly fixed in the bracket 7, electrically connected in series to each other and located differentially above each crystal. To uniformly heat the entire area of the crystal during soldering, the dimensions of the working area of the electrode should be 0.6-1.0 mm larger than each side of the crystal. Heating of the body, crystal and solder to the soldering temperature is carried out due to the heat generated by the working platform of the V-shaped electrode when a current pulse passes through it. To destroy oxide films and activate the connected surfaces of the crystal and the housing at the moment of melting of the solder, the crystals 3, through a vacuum suction cup 2 and the base 1, are exposed to ultrasonic vibrations in the direction parallel to the solder seam from the ultrasonic concentrator 8. The pressure on each crystal is exerted by the mass of the housing and the bracket with electrodes . An example of semiconductor device assembly is the assembly of Schottky diodes. On the collector surface of the semiconductor crystal as part of the wafer known technology the following films are sequentially applied: aluminum - 0.2 microns, titanium - 0.2-0.4 microns, nickel - 0.4 microns, and for soldering - solder, for example PSr2.5, 40-60 microns thick. The semiconductor wafer is then divided into crystals. A metal plate, consisting of 10 cases of 5 type TO-220, is coated using known technology with galvanic nickel with a thickness of 6 microns. The process of assembling Schottky diodes is as follows: crystals 3 with the collector surface up are fixed in the cells of the vacuum suction cup 2, the vacuum pump is turned on, and due to the pressure difference the crystals are pressed against the walls of the vacuum suction cup; the plate with the housings of the devices 5 is placed on the crystals; bracket 7 with electrodes 6 is combined with the contact pads of the housings in places where they are soldered with crystals 3. When soldering, bracket 7 with electrodes 6 presses the plate from housing 5 to the crystals 3. A current pulse is passed through the electrodes, electrically connected in series with each other. Heat from the working platform of the electrode is transferred to the housings and then to the crystals, heating the solder to soldering temperature. At this time, the crystals are exposed to ultrasonic vibrations in a direction parallel to the solder seam from the ultrasonic concentrator 8. This helps to destroy the oxide films and improve the wetting of the joined surfaces of the crystal and the body with solder. Through specified time the current is turned off, and after crystallization of the solder, a high-quality solder joint is formed. The compressive force of the crystal to the body during soldering is set by the mass of the body and the bracket with electrodes. Since during pulse soldering the crystal is heated through the body, the collector surface is heated to the soldering temperature, and the opposite surface of the crystal with structures has a heating temperature significantly lower than the collector surface. This factor helps to increase the reliability of semiconductor devices. Thus, the use of the proposed method for assembling semiconductor devices provides, compared to using existing methods the following advantages. 1. The reliability of semiconductor devices increases by reducing the heating temperature when soldering the surface of the crystal with structures. 2. Wetting of the joined surfaces with solder improves. 3. The productivity of assembly operations is increased due to group soldering of crystals to cases. Sources of information 1. Assembly of high-power transistors using the cassette method / P.K. Vorobyovsky, V.V. Zenin, A.I. Shevtsov, M.M. Ipatova//Electronic technology. Ser. 7. Technology, production organization and equipment. - 1979.- Issue. 4.- pp. 29-32. 2. Soldering microstrip devices with low-temperature solders without the use of fluxes / V.I. Bayle, F.N. Krokhmalnik, E.M. Lyubimov, N.G. Otmakhova//Electronic technology. Ser.7. Microwave Electronics.- 1982.- Issue. 5 (341).- P. 40. 3. Yakovlev G.A. Soldering materials with lead-based solders: Review. - M.: Central Research Institute "Electronics". Ser. 7. Technology, production organization and equipment. Vol. 9 (556), 1978, p. 58 (prototype).

Formula of invention

A method for assembling semiconductor devices, which consists in placing a filter and alloying element on the base of the housing, on which a sample of solder and a crystal are placed, and the cassette with the assembled devices is loaded into a conveyor hydrogen oven at a soldering temperature of 370°C, characterized in that the semiconductor crystals with solder on the collector side is fixed in an inverted position in the cells of a vacuum suction cup and combined with the contact pads of the device housings, and heating to soldering temperature is carried out in air by a current pulse through V-shaped electrodes, which are rigidly fixed in the bracket, electrically connected in series with each other and are located differentially above each crystal, and at the moment of solder melting, a vacuum suction cup with crystals is exposed to ultrasonic vibrations in a direction parallel to the solder seam, while pressure on each crystal is exerted by the mass of the device body and bracket with electrodes.