CN103646938B - Once first plate and lose metal frame subtraction afterwards and bury flip-chip bump structure and process - Google Patents

Abstract

The present invention relates to a metal frame subtractive embedding chip flip-chip bump structure and process method, which is characterized in that the structure includes a metal substrate frame, and base islands and pins are arranged inside the metal substrate frame. The back side of the base island and the stepped surface of the pins are flipped with chips through the underfill glue, the area around the base island, the area between the base island and the pins, the area between the pins, the base The area above the island and the pins, the area below the base island and the pins, and the outside of the chip are encapsulated with a plastic compound, and the surface of the metal substrate frame is coated with an antioxidant, and the plastic compound and the coating on the upper and lower surfaces of the metal substrate frame The antioxidant (OSP) is flush with metal balls placed on the back of the pins. The invention can solve the problem that the thickness of the traditional metal lead frame cannot embed objects and limit the functionality and application performance of the metal lead frame.

Description

Metal frame subtractive buried chip flip-chip bump structure and process method

technical field

The invention relates to a metal frame subtractive embedded chip flip-chip bump structure and a process method thereof. It belongs to the technical field of semiconductor packaging.

Background technique

There are two main types of conventional four-sided flat leadless metal leadframe structures:

One is the four-sided flat no-lead package (QFN) lead frame. The lead frame of this structure is composed of a copper metal frame and a high-temperature resistant adhesive film (as shown in Figure 14).

One is a pre-encapsulated four-sided flat no-lead package (pQFN) lead frame. The lead frame structure of this structure includes pins and base islands, and the etched area between the pins and the base island is filled with plastic encapsulant (Figure 15 shown).

The above conventional metal lead frame has the following disadvantages:

1. The traditional metal lead frame, as the packaging carrier for loading chips, does not have system functions, which limits the integrated functionality and application performance of the traditional metal lead frame after packaging;

2. Since the traditional metal lead frame itself does not have system functions, chips and components can only be tiled or stacked on the front of the lead frame. While the power device and the control chip are packaged in the same package, the heat dissipation of the power device will affect the transmission of the signal of the control chip;

3. Since the traditional metal lead frame itself does not have system functions, the multi-functional system integration module can only be realized by tiling or stacking multiple chips and components on the front of the traditional metal lead frame, which correspondingly increases the number of component modules in the system. space occupied on the PCB.

Contents of the invention

The object of the present invention is to overcome the above-mentioned disadvantages, and provide a flip-chip bump structure and method thereof, which can solve the problem of lack of system functions in traditional metal lead frames.

The object of the present invention is achieved like this: a kind of manufacturing method of metal frame subtractive buried chip flip-chip bump structure after plating first, described method comprises the following steps:

Step 1. Take the metal substrate

Step 2. Paste photoresist film

Paste a photoresist film that can be exposed and developed on the front and back of the metal substrate;

Step 3. Remove part of the photoresist film from the surface of the metal substrate

Use the exposure and development equipment to expose, develop and remove part of the patterned photoresist film on the surface of the metal substrate that has completed the photoresist film pasting operation in step 2;

Step 4: Coating Antioxidant (OSP)

In step 3, the area where part of the photoresist film is removed from the surface of the metal substrate is coated with an antioxidant (OSP) to prevent metal oxidation, such as gold, nickel gold, nickel palladium gold, and tin.

Step 5. Remove the photoresist film

Remove the photoresist film on the surface of the metal substrate;

Step 6. Paste photoresist film

Paste a photoresist film that can be exposed and developed on the surface of the metal substrate;

Step 7. Remove part of the photoresist film from the surface of the metal substrate

Use exposure and development equipment to expose, develop and remove part of the patterned photoresist film on the surface of the metal substrate that has been pasted with the photoresist film in step 6, specifically remove the photoresist film other than the coated antioxidant (OSP) to expose the back of the metal substrate The pattern of the area that needs to be etched later;

Step 8. Chemical etching

Chemical etching of different depths is carried out in the area where part of the photoresist film is removed from the surface of the metal substrate in step 7. After the chemical etching is completed, the corresponding base island and stepped pins are formed;

Step 9. Remove the photoresist film

Remove the photoresist film on the surface of the metal substrate;

Step ten, loading film

On the back of the base island and the step surface of the pins in step 9, flip the completed chip with bumps on the surface, and protect the underfill with underfill glue after completion;

Step 11. Encapsulation

The inside of the metal substrate in step ten is plastic-sealed with a plastic sealing compound, and the plastic sealing compound is flush with the front and back of the metal substrate.

Step 12. Planting the ball

Implant metal balls on the back of the pins in step eleven.

When the anti-oxidation metal layer in step four is nickel-gold or nickel-palladium-gold, the steps six and seven can be omitted.

A flip-chip bump structure of first-plating and later-etching metal frame subtractive buried chip, which includes a metal substrate frame, a base island and pins are arranged inside the metal substrate frame, the pins are stepped, and the base The front of the island and the pin is flush with the front of the metal substrate frame, the back of the pin is flush with the back of the metal substrate frame, the back of the base island is flush with the stepped surface of the pin, and the back of the base island passes through The underfill is flip-chip, the area around the base island, the area between the base island and the pins, the area between the pins, the area above the base island and the pins, the base island and the pins The area of the lower part and the outside of the chip are all encapsulated with a molding compound, and the front side of the base island, the front and back sides of the pins, and the surface of the metal substrate frame are coated with antioxidant (OSP), and the molding compound and the upper and lower surfaces of the metal substrate frame Antioxidant coated (OSP) flush with metal balls placed on the front side of the pins.

Antioxidant is coated on the back of the base island and the stepped surface of the pin.

Compared with the prior art, the present invention has the following beneficial effects:

1. The interlayer of the metal subtraction technology lead frame can embed active components or components or passive components in the required position or area due to the needs of the system and functions, and become a single-layer line system-level metal lead frame;

2. From the appearance of the finished lead frame of metal subtraction technology, it is completely impossible to see that the internal interlayer has been embedded with objects required by the system or function, especially the embedding of silicon chips that cannot be inspected even by X-rays, which fully meets the requirements of the system and Confidentiality and protection of functions;

3. The interlayer of the metal subtraction technology lead frame can be embedded with high-power devices during the production process, and then the control chip is mounted after secondary packaging, so that the high-power device and the control chip are respectively installed on both sides of the metal subtraction technology lead frame, which can Avoid high-power devices from interfering with the signal transmission of the control chip due to heat radiation.

4. Metal subtraction technology The lead frame itself contains the function of embedded objects, and the integration and integration of system functions can be fully realized after secondary packaging, so that the volume size of the component module with the same function is smaller than that of the traditional lead frame packaged module. Small, the corresponding space occupied on the PCB is relatively small, which also reduces the cost.

5. The metal subtraction technology lead frame interlayer can embed heat conduction or heat dissipation objects in the required position or area due to heat conduction or heat dissipation requirements during the production process, thereby improving the heat dissipation effect of the entire package structure;

6. The finished metal subtraction technology lead frame itself is rich in various components. If the subsequent second packaging is not carried out, the metal subtraction technology lead frame is cut according to each cell, and it can become a Ultra-thin package or simple system-in-package;

7. Metal subtraction technology In addition to the embedded function of the embedded object, the lead frame can also be superimposed with different unit packages or system-level packages on the periphery of the package, fully achieving the dual system or multi-system of single-layer metal lead frames. System-level packaging technology capabilities.

8. The objects or objects embedded in the metal subtraction technology lead frame are all flush with the metal thickness, which fully reflects the ultra-thin and high-density filling in the thickness space in the metal subtraction technology lead frame.

Description of drawings

Figures 1 to 12 are schematic diagrams of each process of the process method of first plating first and then etching the metal frame subtractive embedded chip flip-chip bump structure of the present invention.

FIG. 13 is a schematic diagram of a flip-chip bump structure of a metal frame subtractive buried chip in a method of plating first and then etching in accordance with the present invention.

FIG. 14 is a schematic diagram of a conventional quad flat no-leads (QFN) lead frame structure.

Figure 15 is a schematic diagram of the lead frame structure of a pre-encapsulated quad flat no-lead package (pQFN).

in:

Metal Substrate Frame 1

Key Island 2

pin 3

Underfill 4

chip 5

Plastic compound 6

Coated Antioxidant 7

metal ball 8.

detailed description

The process method of the present invention is a metal frame subtractive embedded chip flip-chip bump structure as follows:

Step 1. Take the metal substrate

See Figure 1, take a piece of metal substrate with appropriate thickness, the material of this plate is mainly metal material, and the material of metal material can be copper, iron, galvanized, stainless steel, aluminum or can achieve electrical conductivity Functional metal substances or non-all-metal substances, etc., the choice of thickness can be selected according to product characteristics.

Step 2. Paste photoresist film

Referring to Figure 2, a photoresist film that can be exposed and developed is attached to the front and back of the metal substrate to protect the subsequent etching process. The photoresist film can be a dry photoresist film or a wet photoresist film.

Step 3. Remove part of the photoresist film from the surface of the metal substrate

Referring to Figure 3, use the exposure and developing equipment to expose, develop and remove part of the patterned photoresist film on the metal substrate surface (front and back) that has completed the photoresist film pasting operation in step 2, so as to expose the area that needs to be electroplated on the metal substrate surface graphics.

Step 4: Coating Antioxidant (OSP)

Referring to FIG. 4 , coating antioxidant (OSP) is carried out in the area where part of the photoresist film is removed from the surface of the metal substrate in step 3 to prevent metal oxidation, such as gold, nickel gold, nickel palladium gold, and tin.

Step 5. Remove the photoresist film

Referring to FIG. 5 , the photoresist film on the surface of the metal substrate is removed. The method of removing the photoresist film can be softened with chemical potions and washed with high-pressure water to remove the photoresist film.

Step 6. Paste photoresist film

Referring to FIG. 6 , a photoresist film that can be exposed and developed is pasted on the surface of the metal substrate to protect the subsequent etching process. The photoresist film can be a dry photoresist film or a wet photoresist film.

Step 7. Remove part of the photoresist film from the surface of the metal substrate

Referring to Fig. 7, use the exposure and development equipment to expose, develop and remove part of the photoresist film on the surface of the metal substrate that has completed the photoresist film pasting operation in step 6, specifically to remove the photoresist film other than the coated antioxidant (OSP), so as to Exposing the pattern of the area on the back of the metal substrate that needs to be etched later.

Step 8. Chemical etching

Referring to Figure 8, chemical etching of different depths is carried out in the area where part of the photoresist film is removed from the surface of the metal substrate in step 7. After the chemical etching is completed, the corresponding base island and stepped pins can be formed. The etching solution can be copper chloride. Either ferric chloride or a potion or technique that chemically etches metal.

Step 9. Remove the photoresist film

Referring to FIG. 9 , the photoresist film on the surface of the metal substrate is removed. The method of removing the photoresist film can be softened with chemical potions and washed with high-pressure water to remove the photoresist film.

Step ten, loading film

Referring to FIG. 10 , flip-chip the completed chip with bumps on the back of the base island and the step surface of the pins in step 9, and perform underfill protection with underfill glue after completion.

In order to prevent the oxidation of the metal substrate from affecting the electrical interconnection between the chip and the substrate and the tin diffusion during flip-chip, the exposed metal surface of the metal substrate surface can be coated with an antioxidant before step ten.

Step 11. Encapsulation

Referring to Figure 11, the inside of the metal substrate in step 10 is plastic-sealed with a plastic sealing compound. The plastic sealing compound is flush with the coating antioxidant (OSP) on the upper and lower surfaces of the metal substrate. The plastic sealing method can be mold filling, spraying, brushing or It is a film-pasting method, and the molding compound can be epoxy resin with filler or no filler.

Step 12. Planting the ball

Referring to Figure 12, metal balls are implanted on the back of the pins in Step 15. The ball planting method can be directly implanted with metal balls or brushed with metal paste using a mask (MASK), and then reflowed at high temperature to form a metal ball. ball.

Referring to FIG. 13 , it is a structural schematic diagram of a metal frame subtractive embedded chip flip-chip bump structure of the present invention, which includes a metal substrate frame 1, and a base island 2 and a lead are arranged inside the metal substrate frame 1. pin 3, the pin 3 is stepped, the front of the base island 2 and the pin 3 is flush with the front of the metal substrate frame 1, and the back of the pin 3 is flush with the back of the metal substrate frame 1, so The back of the base island 2 is flush with the step surface of the pin 3, and the back of the base island 2 is flip-mounted with a chip 5 through the underfill glue 4, and the area around the base island 2, the base island 2 and the pin 3 The area between pin 3 and pin 3, the area above base island 2 and pin 3, the area below base island 2 and pin 3, and the outside of the chip are encapsulated with plastic encapsulant 6. The front of base island 2, the front and back of pins 3, and the surface of metal substrate frame 1 are coated with antioxidant (OSP) 7, and the molding compound 6 is flush with the coated antioxidant (OSP) 7 on the upper and lower surfaces of metal substrate frame 1 , a metal ball 8 is arranged on the front surface of the pin 3 .

Claims (5)

1. a kind of processing method of metal frame subtraction buried chip flip-chip bump structure after plating first, described method comprises the steps: Step 1. Take the metal substrate Step 2. Paste photoresist film Paste a photoresist film that can be exposed and developed on the front and back of the metal substrate; Step 3. Remove part of the photoresist film on the front and back of the metal substrate Use the exposure and development equipment to expose, develop and remove part of the graphic photoresist film on the front and back of the metal substrate that has completed the photoresist film pasting operation in step 2; Step 4: Antioxidant coating Carry out coating antioxidant in the region where part of the photoresist film is removed on the front and back of the metal substrate in step 3; Step 5. Remove the photoresist film Remove the photoresist film on the front and back of the metal substrate; Step 6. Paste photoresist film Paste a photoresist film that can be exposed and developed on the front and back of the metal substrate; Step 7. Remove part of the photoresist film on the front and back of the metal substrate Use the exposure and development equipment to expose the front and back of the metal substrate after the photoresist film pasting operation in step 6, develop and remove part of the pattern photoresist film, specifically remove the photoresist film other than the coated antioxidant to expose the front and back of the metal substrate. The area graphics that need to be etched later on the back; Step 8. Chemical etching Chemical etching of different depths is carried out in the area where part of the photoresist film is removed on the front and back of the metal substrate in step 7. After the chemical etching is completed, the corresponding base island and stepped pins are formed; Step 9. Remove the photoresist film Remove the photoresist film on the front and back of the metal substrate; Step ten, loading film On the back of the base island and the step surface of the pins in step 9, flip the completed chip with bumps on the surface, and protect the underfill with underfill glue after completion; Step 11. Encapsulation The inside of the metal substrate in step 10 is plastic-sealed with a plastic sealing compound, and the plastic sealing compound is flush with the front and back of the metal substrate; Step 12. Planting the ball Implant metal balls on the back of the pins in step eleven. 2. the processing method of metal frame subtraction buried chip flip-chip bump structure after plating first according to claim 1, it is characterized in that when the antioxidant in step 4 is nickel gold or nickel palladium gold, said step Steps 6 and 7 are omitted. 3. A kind of processing method of metal frame subtraction buried chip flip-chip bump structure according to claim 1, it is characterized in that: remove the photoresist film in step 9 and install the chip in step 10. The bare metal surface of the substrate surface is coated with antioxidant. 4. A flip-chip bump structure obtained by the process method described in claim 1, 2 or 3, is characterized in that it includes a metal substrate frame (1), and The metal substrate frame (1) is provided with a base island (2) and pins (3), the pins (3) are stepped, and the front sides of the base island (2) and pins (3) are aligned with The front of the metal substrate frame (1) is flush, the back of the pin (3) is flush with the back of the metal substrate frame (1), and the back of the base island (2) is flush with the stepped surface of the pin (3) , the pin (3) and the backside of the base island (2) are flipped with a chip (5) through the underfill (4), and the peripheral area of the base island (2), the base island (2) and the pin Area between (3), area between pin (3) and pin (3), base island (2) and area above pin (3), base island (2) and pin (3) The lower area and the outside of the chip (5) are encapsulated with a plastic encapsulant (6), and the front of the base island (2), the front and back of the pin (3) and the surface of the metal substrate frame (1) are coated with antioxidants (7), the molding compound (6) is flush with the antioxidant coating (7) on the upper and lower surfaces of the metal substrate frame (1), and a metal ball (8) is arranged on the back of the pin (3). 5. The flip-chip bump structure of first-plating and later-etching metal frame subtractive buried chip flip-chip bump structure according to claim 4, characterized in that: the back surface of the base island (2) and the step surface of the pin (3) are covered with anti- Oxidizing agent (7).