A capacitive coupling isolation amplifier package structure and a packaging method thereof

Abstract

The application relates to a capacitive coupling isolation amplifier package structure and a packaging method thereof, and belongs to the technical field of integrated circuit packaging. The capacitive coupling isolation amplifier package structure comprises a double-base-island isolation type lead frame, a chip component, a chip capacitor, assembly material, a bonding wire and packaging material. The double-base-island isolation type lead frame comprises a left base island and a right base island which are isolated from each other, and two or more pins; the chip component is a semiconductor chip or a chip electronic component; an input side semiconductor chip or chip electronic component is arranged in a left side area of the left base island; and an output side semiconductor chip or chip electronic component is arranged in a right side area of the right base island. The chip capacitor is arranged in a close area of the two base islands; and the chip component and the chip capacitor are connected with corresponding electrical connection points through the bonding wire. The problems of large volume, poor anti-interference performance, low pressure bearing capacity, poor quality consistency and low reliability in the prior art are solved. The capacitive coupling isolation amplifier package structure is suitable for the fields of power supply, motor controller, remote voltage detection, biomedical measurement and remote data acquisition.

Description

Technical Field

[0001] This invention belongs to the field of integrated circuit packaging technology, and more specifically to the field of isolation amplifier packaging. In particular, it relates to an isolation amplifier packaging method based on capacitive coupling. Background Technology

[0002] An isolation amplifier is an amplifier that provides potential isolation between its input and output circuitry (including associated power supplies), with no conductive path between the input and output sections. Leakage current between the two sections is extremely low, and the dielectric breakdown voltage is very high. Typically, the input stage is a differential amplifier to attenuate common-mode voltages because the inputs differ by less than 1V, and the amplifier is floating and not ground-referenced. Careful design and layout minimize stray capacitive coupling between the sections to avoid compromising isolation. A schematic diagram of an isolation amplifier is shown below. Figure 1 As shown, isolation between components can be achieved through transformers, capacitors, or optical coupling to block DC and low-frequency components of the signal. A carrier wave is modulated using the input signal, and the full signal spectrum is transmitted, then recovered through demodulation at the device output. Isolated power supplies are used at both the input and output terminals.

[0003] The modulation technique used depends on the device; common techniques include frequency modulation, pulse width modulation, and trigonometric integrator modulation (TIM). TIM is the most frequently encountered; the input is differential, and the output can be single-ended or differential. Isolation amplifiers have separate power supply connections for the input and output sections. Typically, the input section uses a non-ground-referenced "floating" power supply. Maintaining good isolation requires well-isolated power supplies.

[0004] The maximum voltage difference rating between the input and output of an isolation amplifier is typically specified for continuous DC and AC voltages, while the maximum applied voltage for transient conditions is specified separately and depends on the timing of the transient conditions.

[0005] An isolation amplifier provides current blocking between its input and output, thus transmitting only the desired signal and eliminating high common-mode voltages. In sensor-based monitoring systems, isolation amplifiers maintain ground separation between sensors to eliminate ground loops. Isolation amplifiers are widely used in power supplies, motor controllers, remote voltage sensing, biomedical measurements, and remote data acquisition.

[0006] like Figure 2As shown, the input stage of an existing capacitively coupled isolation amplifier consists of a differential amplifier, followed by a driving triangular integral modulator. The isolation clock (carrier) is derived internally, and the transmitter (TX) driver transmits data to the other side of the signal transmission / reception dual capacitor coupler (dual capacitor isolation barrier). Each branch of the isolation barrier uses two series capacitors to provide capacitive isolation. The received modulated data is demodulated and synchronized with the clock on the low-voltage side, and the output is a differential signal.

[0007] The current packaging structure for isolation amplifiers involves assembling the input-side differential amplifier, modulator, receiver, and transmitter, along with an intermediate dual-capacitor coupler, and the output-side receiver, transmitter, demodulator, and output amplifier (with a filter) onto a substrate, followed by circuit connections and encapsulation. The problems include a large assembly size, poor interference immunity, low withstand capability on both the high-voltage input and low-voltage output sides (the withstand capability is entirely determined by the withstand voltage of the dual-capacitor coupler), long interconnections between components, and significant signal crosstalk, resulting in poor quality consistency and low reliability.

[0008] In view of this, the present invention is hereby proposed. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to solve the problems of large size, poor anti-interference, low pressure resistance, poor quality consistency and low reliability in the existing assembly technology.

[0010] The inventive concept of this invention is as follows: Figure 2 , Figure 3 As shown, a dual-base island isolation lead frame is used. The left input devices of the isolation amplifier and the left circuit of the dual-capacitor coupler are integrated together on the left base island, while the right output devices of the isolation amplifier and the right circuit of the dual-capacitor coupler are integrated together on the right base island. Thus, the two parallel sides of the gap between the dual base islands form a strong electromagnetic interference isolation barrier, forming an isolation gate. This effectively isolates the input and output sides, providing enhanced current isolation up to the kVRMS level.

[0011] This invention provides a packaging structure for an isolation amplifier based on capacitive coupling, such as... Figure 2-5 As shown, it includes: a dual-base island isolated lead frame, chip components, chip capacitors, assembly materials, bonding wires, and encapsulation materials.

[0012] The dual-base island isolated lead frame includes a left base island and a right base island that are isolated from each other, and two or more pins. A capacitor isolation barrier is formed between the parallel sides of the left base island and the right base island, generating an isolation barrier.

[0013] The chip-type component is a semiconductor chip or a chip-type electronic component. The input-side semiconductor chip or chip-type electronic component is located in the left region of the left base island, and the output-side semiconductor chip or chip-type electronic component is located in the right region of the right base island.

[0014] The chip capacitor consists of two independent capacitors and a shielding shell, located in the close area of ​​the two base islands.

[0015] The assembly material is conductive adhesive or DAF film, used to mount chip components onto corresponding substrate islands.

[0016] The bonding wire is a gold wire, a silicon-aluminum wire, or a copper wire, used to connect the electrode leads of the chip components and the electrode leads of the chip capacitors to the corresponding electrical connection points.

[0017] The encapsulating material is a molding compound.

[0018] This invention provides a method for packaging an isolation amplifier based on capacitive coupling, comprising the following packaging method:

[0019] (1) Gluing: The chip components and chip capacitors are mounted on the base island of the lead frame using assembly materials;

[0020] (2) Bonding: Bonding wires are used to bond the pads on the chip components and chip capacitors to the corresponding pins of the frame, thereby bringing out the function of the circuit from the external pins of the device.

[0021] (3) Packaging: Select a suitable molding compound to package the chip components and chip capacitors mounted on the lead frame island to form a semiconductor device with a certain structural shape.

[0022] (4) Marking: Laser printing of product labels;

[0023] (5) Shaping and trimming: Shaping and trimming according to product size requirements.

[0024] Technical effects of the invention:

[0025] (1) Applicable to device packaging based on capacitive coupling principle to achieve isolation amplification.

[0026] (2) When plastic packaging is used, the isolation strength between the input side and the output side is as high as kVRMS level strong current isolation.

[0027] (3) The chip components, chip capacitors and lead frames are structurally integrated, which makes the package miniaturized, powerful, low power consumption, low cost, high reliability, easy to design and easy to manufacture.

[0028] (4) Improve the system's design efficiency and overall performance, reduce system costs, increase its reliability, and reduce the requirements for chip design and equipment.

[0029] The technical solution of this invention is applicable to fields such as power supply, motor controller, remote voltage detection, biomedical measurement, and remote data acquisition.

[0030] Explanation of relevant terms:

[0031] 1. Isolation Amplifier: A special type of measurement amplifier circuit where there is no direct circuit coupling between its input, output, and power supply circuits, meaning the signal has no common ground during transmission. This amplifier circuit consists of an operational amplifier and a unity-gain isolation stage. The unity-gain isolation stage completely isolates the input and output of the device (ohmic isolation), eliminating ohmic continuity in the electrical signal.

[0032] 2. Isolation Barrier: The high-side power supply voltage module on the left base island and the low-side power supply voltage module on the right base island are independent of each other, forming an isolation channel between the left and right base islands; after the input power is applied, the voltages of the high-side and low-side power supplies are different, which manifests as a potential difference. Since the chip capacitors are made of materials with strong anti-magnetic interference capabilities, interconnecting the two capacitors can form an isolation barrier with strong anti-electromagnetic interference capabilities in the isolation channel.

[0033] 3. Conductive adhesive / DAF film: An adhesive that has a certain conductivity after curing or drying. It can connect multiple conductive materials together, so that an electrical path is formed between the connected materials.

[0034] 4. Bonding wire: A fine metal wire used in the assembly of semiconductor devices and integrated circuits to achieve electrical connection between the input / output bonding points of the internal circuitry of the chip and the internal contact points of the lead frame.

[0035] 5. Leadframe: A key structural material in integrated circuit packaging. It primarily serves to support the integrated circuit chip, connect the chip to external circuit boards for electrical signals, and provide mechanical support for mounting and securing the chip.

[0036] 6. Base island: The area on the lead frame that can hold the chip.

[0037] 7. Pin pitch: The distance between the centers of two adjacent pins.

[0038] 8. EMC: Epoxy molding compound.

[0039] 9. VRMS: Root mean square voltage, isolation voltage.

[0040] 10. DIE: Chip. Attached Figure Description

[0041] Figure 1 A schematic diagram of the principle of a general isolation amplifier.

[0042] Figure 2 Schematic diagram of the principle of a capacitively coupled isolation amplifier.

[0043] Figure 3 Schematic diagram of the assembly structure of a capacitively coupled isolation amplifier.

[0044] Figure 4 Schematic diagram of assembly and encapsulation structure.

[0045] Figure 5 Illustration of the lamination effect.

[0046] In the diagram: 1 is the left base island, 2 is the right base island, 3 is the pin, 4 is the input-side semiconductor chip or chip electronic component, 5 is the input-side chip capacitor, 6 is the output-side chip capacitor, 7 is the input-side semiconductor chip or chip electronic component, and 8 is the bonding wire. Detailed Implementation

[0047] like Figure 2-5 As shown, taking the 8-pin SOW8L package as an example, the specific implementation method is as follows:

[0048] A capacitively coupled isolation amplifier package structure includes a semiconductor chip, chip capacitors, bonding wires, molding compound, and a dual-base island lead frame.

[0049] The input side consists of the left base island, the input semiconductor chip (DIE1), and the input chip capacitor (DIE2), while the output side consists of the right base island, the output semiconductor chip (DIE4), and the output chip capacitor (DIE3).

[0050] The distance between the left and right base islands is 0.51mm (the design must ensure that the interval is not less than 0.50mm).

[0051] The lead frame is made of copper, which has advantages in electrical performance, heat dissipation and encapsulation, as well as cost.

[0052] The lead frame pins, numbered 1 to 8, correspond to the high-side power supply voltage, input (+), input (-), high-side ground, low-side ground, output (-), output (+), and low-side power supply voltage of the device, respectively. The pin width is 0.47 mm and the pin pitch is 1.27 mm.

[0053] By using gold wire bonding with a bonding wire diameter of 25μm, the pads on the semiconductor chip and chip capacitor are interconnected with the corresponding pins of the frame, thereby bringing out the function of the semiconductor chip and chip capacitor from the external pins of the device.

[0054] Selecting a suitable molding compound for injection molding involves using transfer molding to extrude the molding compound into the mold cavity, resulting in a semiconductor device with a specific structural shape.

[0055] The encapsulation method is as follows:

[0056] (1) Gluing: Using appropriate conductive adhesive / DAF film, the semiconductor chip and chip capacitor are mounted in the corresponding area of ​​the lead frame base island;

[0057] (2) Bonding: Gold wire with a bonding wire diameter of 25μm is used for bonding;

[0058] (3) Molding: Select the set molding material, use the transfer molding method to extrude the molding material into the mold cavity, and injection mold it into a semiconductor device with a certain structural shape.

[0059] (4) Marking: Laser printing of product labels;

[0060] (5) Molding and trimming: The pins are processed and trimmed, and the pin length is 0.50mm to 1.00mm.

[0061] Finally, it should be noted that the above embodiments are merely examples for clear illustration, and also include, for example:

[0062] Regarding the packaging structure:

[0063] (1) Depending on the design requirements of different types of isolation amplifiers, the above-mentioned dual-island structure can be extended to a three-island structure.

[0064] (2) It can be extended to integrated systems that integrate chips, sensors, components, antennas, interconnects, etc.

[0065] Regarding the preparation process:

[0066] (1) The base island is recessed: the frame part surrounded by the molding compound is recessed, that is, the frame is "U" shaped. During the injection molding process, it promotes the balance of the upper and lower mold flow of the encapsulation, improves reliability, and leaves space for the arc height of the chip bonding wire during bonding.

[0067] (2) Roughening the frame: that is, grinding the frame to increase its surface roughness, thereby enhancing the bonding force between the frame and the molding compound and improving reliability.

[0068] (3) The back of the base island is etched with pits or channels: Partial pit or channel etching is performed on the back of the base island to enhance the bonding force between the frame and the molding compound and improve reliability.

[0069] It can be applied to various packaging methods, including plastic, ceramic, and metal encapsulation. It is neither necessary nor possible to exhaustively list all possible implementations. Those skilled in the art can make other variations or modifications based on the above description. All implementations that meet the requirements of this invention are within the scope of protection of this invention.

Claims

1. A capacitively coupled isolation amplifier package structure, characterized in that: This includes dual-base island isolated lead frames, chip components, chip capacitors, assembly materials, bonding wires, and packaging materials; The dual-base island isolated lead frame includes a left base island and a right base island that are isolated from each other, and two or more pins. A capacitor isolation barrier is formed between the parallel sides of the left base island and the right base island to generate an isolation barrier. The high-side power supply voltage module on the left base island is independent of the low-side power supply voltage module on the right base island, and an isolation channel is formed between the left and right base islands. After the input power is applied, the voltages of the high-side and low-side power supplies are different, which manifests as a potential difference. Since the chip capacitors are made of materials with strong anti-magnetic interference capabilities, interconnecting the two capacitors can form an isolation barrier with strong anti-electromagnetic interference capabilities in the isolation channel. The chip-type component is a semiconductor chip or a chip-type electronic component. The input-side semiconductor chip or chip-type electronic component is located in the left region of the left base island, and the output-side semiconductor chip or chip-type electronic component is located in the right region of the right base island. The chip capacitor consists of two independent capacitors and a shielding shell, located in the close area of ​​the two base islands; The assembly material is a conductive adhesive or a DAF film; The bonding wire is a gold wire, a silicon-aluminum wire, or a copper wire, used to connect the electrode leads of the chip components and the electrode leads of the chip capacitor to the corresponding electrical connection points through the bonding wire. The encapsulating material is a molding compound; The encapsulation method of the encapsulation structure includes the following encapsulation methods: (1) Gluing: The chip components and chip capacitors are mounted on the base island of the lead frame using assembly materials; (2) Bonding: Bonding wires are used to connect the pads on the chip components and chip capacitors to the corresponding pins of the frame, thereby bringing out the function of the circuit from the external pins of the device; (3) Packaging: Select appropriate molding compound to package the chip components and chip capacitors mounted on the lead frame island to form a semiconductor device with a certain structural shape; (4) Marking: Laser printing of product identification; (5) Forming and trimming: Forming and trimming according to product size requirements; The base island is recessed; The frame is coarsened; The back of the base island is etched with pits or trenches.

2. The capacitively coupled isolation amplifier package structure as described in claim 1, characterized in that: The chip components and chip capacitors are bonded to the corresponding areas on the substrate island using conductive adhesive or DAF film.

3. The capacitively coupled isolation amplifier package structure as described in claim 1, characterized in that: The distance between the left base island and the right base island is not less than 0.50 mm.

4. The capacitively coupled isolation amplifier package structure as described in claim 3, characterized in that: The distance between the left base island and the right base island is 0.51 mm.

5. The capacitively coupled isolation amplifier package structure as described in claim 1, characterized in that: The lead frame is made of copper.

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