CN103646934B - First plate for two times and lose metal frame subtraction afterwards and bury chip and just filling flat leg structure and processing method - Google Patents

Abstract

The present invention relates to a structure and a process method of a metal frame subtraction embedded chip after plating first and then etching. The structure includes a metal substrate frame (1), and a base island (2) is arranged inside the metal substrate frame (1). ) and the pin (3), the pin (3) is stepped, the back of the base island (2) is flush with the stepped surface of the pin (3), and the stepped surface of the pin (3) A metal layer (4) is provided, and a chip (6) is mounted on the back of the base island (2), and the surface of the chip (6) is connected to the surface of the metal layer (4) through a metal wire (7). The inner area of the metal substrate frame (1) is filled with plastic encapsulant (8), the front of the plastic encapsulant (8) is flush with the stepped surface of the pin (3), and the back of the plastic encapsulant (8) is flush with the metal substrate frame (1) The back is flush, and the front and back of the base island (2), the front and back of the pin (3), and the front and back of the metal substrate frame (1) are provided with an anti-oxidation layer (9). The beneficial effect of the invention is that it can solve the problem that the traditional metal lead frame cannot be embedded in objects and limits the functionality and application performance of the metal lead frame.

Description

The structure and process method of the front-mounted flat feet of the metal frame subtraction embedded chip after the second plating

technical field

The invention relates to a structure and a process method of a front-mounted flat leg structure and a process method of a metal frame subtraction embedded chip after plating first and then etching, and 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, which is composed of a copper metal frame and a high-temperature resistant adhesive film (as shown in Figure 22);

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 (as shown in Figure 23 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. However, the power device and the control chip are packaged in the same package, and the heat dissipation of the power device will affect the control chip. transmission of signals;

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 purpose of the present invention is to overcome the above-mentioned disadvantages, and provide a structure and process method of first plating and then etching the metal frame subtractive embedded chip front-mounted flat feet, which can solve the problem of lack of system functions in traditional metal lead frames.

The object of the present invention is achieved in the following way: a metal frame subtractive embedded chip is mounted on a flat foot structure after secondary plating, which includes a metal substrate frame, and base islands and pins are arranged inside the metal substrate frame, and the lead The feet are stepped, the front of the base island and the pin are flush with the front of the metal substrate frame, the back of the pin is flush with the back of the metal substrate frame, and the back of the base island is flush with the stepped surface of the pin , the step surface of the pin is provided with a metal layer, the back of the base island is equipped with a chip through a conductive or non-conductive adhesive substance, the surface of the chip is connected with the surface of the metal layer by a metal wire, the metal The inner area of the substrate frame is filled with molding compound, the front of the molding compound is flush with the stepped surface of the pins, the back of the molding compound is flush with the back of the metal substrate frame, the front of the base island, the front and back of the pins and the metal substrate The front and back sides of the frame are provided with a metal anti-oxidation layer or Oxidation Antioxidant Overlay (OSP).

A metal layer is arranged between the chip and the back surface of the base island.

A kind of process method of first plating and then etching metal frame subtraction method of embedded chip front-mounted flat leg structure, said 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 on the front and back of the metal substrate

Use exposure and developing equipment to expose, develop and remove part of the graphic photoresist film on the front and back of the metal substrate that has been pasted with the photoresist film in step 2, so as to expose the areas that need to be electroplated on the front and back of the metal substrate;

Step 4. Plating anti-oxidation metal layer or coating anti-oxidant (OSP)

Electroplating an anti-oxidation metal layer or coating an anti-oxidant (OSP) on the area 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 surface of the metal substrate;

Step 6. Paste photoresist film

After the electroplating of the anti-oxidation metal layer is completed in step 4, a photoresist film that can be exposed and developed is pasted on the front and back of the metal substrate;

Step 7. Remove part of the photoresist film on the back of the metal substrate

Use exposure and development equipment to expose, develop and remove part of the graphic photoresist film on the etched area on the back of the metal substrate that has completed the photoresist film pasting operation in step 6, so as to expose the area that needs to be etched on the back of the metal substrate;

Step 8. Etching

Perform chemical etching in the area where part of the photoresist film is removed on the back of the metal substrate in step 7;

Step 9. Remove the photoresist film

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

Step 10. Paste photoresist film

Paste a photoresist film that can be exposed and developed on the front and back of the etched metal substrate in step 8;

Step 11. Remove part of the photoresist film on the back of the metal substrate

Use the exposure and development equipment to expose, develop and remove part of the graphic photoresist film on the etched area on the back of the metal substrate where the photoresist film pasting operation has been completed in step ten, so as to expose the area that needs to be electroplated in the etched area on the back of the metal substrate;

Step 12. Electroplating the metal circuit layer

In the eleventh step, the metal circuit layer is electroplated in the area where part of the photoresist film is removed from the etching area on the back of the metal substrate. After the electroplating of the metal circuit layer is completed, corresponding base islands and pins are formed on the back of the metal substrate;

Step 13. Remove the photoresist film

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

Step 14, loading film

Implanting the chip on the back of the base island formed in step 12 through a conductive or non-conductive bonding substance;

Step 15. Wire Bonding

Perform bonding metal wire operation between the front side of the chip and the pins formed in step 12;

Step 16. Epoxy resin plastic sealing

Epoxy resin molding protection is carried out on the etching area on the back of the metal substrate after chip loading and wiring;

Step 17. Paste photoresist film

Paste a photoresist film that can be exposed and developed on the front and back of the metal substrate after epoxy resin molding is completed in step sixteen;

Step 18. Remove part of the photoresist film from the front of the metal substrate

Using the exposure and development equipment, perform pattern exposure, development and removal of part of the pattern photoresist film on the front of the metal substrate that has completed the photoresist film pasting operation in step 17, so as to expose the area that needs to be etched later on the front of the metal substrate;

Step 19. Etching

Perform chemical etching in the region where part of the photoresist film is removed from the front of the metal substrate in step 18;

Step 20, remove the photoresist film

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

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

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 thermal 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, correspondingly occupy less space on the PCB, thus reducing 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;

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.

9. Subtraction technology of plating metal frame after secondary etching The lead frame will present a certain height difference on the front of the plastic compound on the surface of the metal lead frame. Its advantage is that it can firmly grasp and buckle the metal bump Points, thereby reducing the poor reliability of delamination caused by the gap between the plastic package and the metal lead frame due to the difference in CTE (expansion coefficient or shrinkage rate).

Description of drawings

Figures 1 to 20 are schematic diagrams of each process of a process method of the present invention, which is a process method of first plating first and then etching the metal frame subtractive buried chip front mounting flat leg structure.

Fig. 21 is a schematic diagram of a flat leg structure of a metal frame subtractive embedded chip with secondary plating first and then etching in the present invention.

FIG. 22 is a schematic diagram of a conventional quad flat no-leads (QFN) lead frame structure.

Figure 23 is a schematic diagram of a pre-encapsulated quad flat no-leads (PQFN) lead frame structure.

in:

Metal Substrate Frame 1

Key Island 2

pin 3

metal layer 4

Conductive or non-conductive bonding substances5

Chip 6

Metal wire 7

Plastic compound 8

Antioxidant layer9.

detailed description

Referring to Fig. 21 , the present invention is a metal frame subtractive embedded chip structure with secondary plating first and then etching, which includes a metal substrate frame 1, and a base island 2 and pins 3 are arranged inside the metal substrate frame 1. 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, 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 metal substrate frame 1. It is flush with the step surface of the pin 3, the metal layer 4 is arranged on the step surface of the pin 3, the back of the base island 2 is equipped with a chip 6 through a conductive or non-conductive adhesive substance 5, and the surface of the chip 6 is It is connected with the surface of the metal layer 4 through a metal wire 7. The inner area of the metal substrate frame 1 is filled with a molding compound 8. The front side of the molding compound 8 is flush with the stepped surface of the pin 3, and the back side of the molding compound 8 is flush with the stepped surface of the pin 3. The back of the metal substrate frame 1 is flush, and the front and back of the base island 2 , the front and back of the pin 3 and the front and back of the metal substrate frame 1 are provided with an anti-oxidation layer 9 .

A metal layer 4 is provided between the chip 6 and the back surface of the base island 2 .

Its process method is as follows:

Step 1. Take the metal substrate

See Figure 1, take a piece of metal substrate with appropriate thickness, the material of the metal substrate can be copper, iron, galvanized material, stainless steel, aluminum or metal or non-metal material that can achieve conductive function, the choice of thickness can be Choose according to product characteristics;

Step 2. Paste photoresist film

Referring to Figure 2, a photoresist film that can be exposed and developed is pasted on the front and back of the metal substrate, and the photoresist film can be a dry photoresist film or a wet photoresist film;

Step 3. Remove part of the photoresist film on the front and back of the metal substrate

Referring to Figure 3, use the exposure and developing 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, so as to expose the areas that need to be electroplated on the front and back of the metal substrate;

Step 4. Plating anti-oxidation metal layer or coating anti-oxidant (OSP)

Referring to Fig. 4, in step 3, in the area where part of the photoresist film is removed from the front and back of the metal substrate, an anti-oxidation metal layer is electroplated or coated with an antioxidant (OSP);

Step 5. Remove the photoresist film

See Figure 5, to remove the photoresist film on the surface of the metal substrate, the method of removing the photoresist film is softened by chemical potion and rinsed with high-pressure water;

Step 6. Paste photoresist film

Referring to Fig. 6, after the oxidation-resistant metal layer is electroplated in step 4, a photoresist film that can be exposed and developed is attached to the front and back of the metal substrate. The photoresist film can be a dry photoresist film or a wet photoresist film;

Step 7. Remove part of the photoresist film on the back of the metal substrate

Referring to Fig. 7, use the exposure and developing equipment to expose, develop and remove part of the graphic photoresist film on the etched area on the back of the metal substrate that has completed the photoresist film pasting operation in step 6, so as to expose the area that needs to be etched on the back of the metal substrate;

Step 8. Etching

Referring to Figure 8, perform chemical etching on the area where part of the photoresist film is removed on the back of the metal substrate in step 7. The chemical etching technology can use copper chloride, ferric chloride or chemicals that can corrode metal materials;

Step 9. Remove the photoresist film

Referring to Figure 9, remove the photoresist film on the surface of the metal substrate. The method of removing the photoresist film is softened by chemical potion and rinsed with high-pressure water;

Step 10. Paste photoresist film

Referring to FIG. 10 , the front and back of the metal substrate after etching in step 8 are pasted with a photoresist film that can be exposed and developed. The photoresist film can be a dry photoresist film or a wet photoresist film;

Step 11. Remove part of the photoresist film on the back of the metal substrate

Referring to FIG. 11 , use the exposure and developing equipment to expose, develop and remove part of the graphic photoresist film on the etched area on the back of the metal substrate where the photoresist film pasting operation has been completed in Step 10, so as to expose the etched area on the back of the metal substrate that needs to be subsequently electroplated;

Step 12. Electroplating the metal circuit layer

Referring to Figure 12, in step 11, the metal circuit layer is electroplated in the area where part of the photoresist film is removed from the etching area on the back of the metal substrate. After the metal circuit layer is electroplated, corresponding base islands and pins are formed on the back of the metal substrate. The metal circuit The material of the layer can be silver, nickel-gold or nickel-palladium-gold, etc. The thickness of the electroplating or the conductive metal material can be changed according to different characteristics. The electroplating method can be electrolytic plating or chemical deposition;

Step 13. Remove the photoresist film

Referring to Figure 13, remove the photoresist film on the surface of the metal substrate. The method of removing the photoresist film is softened by chemical potion and rinsed with high-pressure water;

Step 14, loading film

Referring to Figure 14, the back of the base island formed in step 12 is implanted into the chip through conductive or non-conductive adhesive substances. The way of implanting the chip can be flexibly selected according to the product characteristics, and the front of the base island can be glued and mounted, and the back of the chip can be covered. Laminate or DAF (DieAttachFilm) film for loading;

Step 15. Wire Bonding

Referring to Figure 15, perform bonding metal wire operation between the front side of the chip and the pins formed in step 12;

Step 16. Epoxy resin plastic sealing

Referring to Figure 16, the etched area on the back of the metal substrate is protected by epoxy resin molding after chip loading and wiring. The epoxy resin material can be filled or unfilled according to product characteristics;

Step 17. Paste photoresist film

Referring to Fig. 17, in step 16, the front and back of the metal substrate after epoxy resin molding is completed, and a photoresist film that can be exposed and developed is pasted;

Step 18. Remove part of the photoresist film from the front of the metal substrate

Referring to FIG. 18 , use the exposure and developing equipment to expose, develop and remove part of the graphic photoresist film on the front of the metal substrate that has completed the photoresist film pasting operation in step 17, so as to expose the area that needs to be etched later on the front of the metal substrate;

Step 19. Etching

Referring to FIG. 19, chemical etching is carried out in the area where part of the photoresist film is removed from the front of the metal substrate in step 18. The chemical etching technology can use copper chloride, ferric chloride or chemicals that can corrode metal materials;

Step 20, remove the photoresist film

Referring to FIG. 20 , the photoresist film on the surface of the metal substrate is removed. The method for removing the photoresist film is to soften it with chemical potions and wash it with high-pressure water.

Claims (1)

1. one kind is first plated for two times and loses metal frame subtraction afterwards and bury the processing method that chip is just filling flat leg structure, it is characterised in that described method comprises the following steps:

Step one, get metal substrate

Step 2, subsides photoresistance film operation

The photoresistance film that can carry out exposure imaging is sticked respectively in metal substrate front and the back side;

Step 3, metal substrate front and back side removal unit divide photoresistance film

Exposure imaging equipment is utilized to complete step 2 to paste the metal substrate front of photoresistance film operation and the back side carries out graph exposure, development and removal partial graphical photoresistance film, to expose the region that the follow-up needs in metal substrate front and the back side carry out electroplating;

Step 4, plating anti-oxidant metal layer

In step 3, metal substrate front and back side removal unit divide anti-oxidant metal layer in the region plating of photoresistance film;

Step 5, removal photoresistance film

Remove the photoresistance film of metallic substrate surfaces;

Step 6, subsides photoresistance film operation

The photoresistance film that can carry out exposure imaging is sticked at metal substrate front and the back side after step 4 completes plating anti-oxidant metal layer;

Step 7, metal substrate back side removal unit divide photoresistance film

The metal substrate back etched region utilizing exposure imaging equipment that step 6 completes to paste photoresistance film operation carries out graph exposure, development and removes partial graphical photoresistance film, to expose the region that the follow-up needs in the metal substrate back side carry out etching;

Step 8, etching

In step 7, the region of metal substrate back side removal unit point photoresistance film carries out chemical milling;

Step 9, removal photoresistance film

Remove the photoresistance film of metallic substrate surfaces;

Step 10, subsides photoresistance film operation

The photoresistance film that can carry out exposure imaging is sticked at metal substrate front and the back side after step 8 completes etching;

Step 11, metal substrate back side removal unit divide photoresistance film

The metal substrate back etched region utilizing exposure imaging equipment that step 10 completes to paste photoresistance film operation carries out graph exposure, development and removes partial graphical photoresistance film, to expose the region that the follow-up needs in metal substrate back etched region carry out electroplating;

Step 12, plated metal line layer

In step 11, metal substrate back etched region removal unit divides in the region of photoresistance film metallic circuit layer in plating, and namely metallic circuit layer forms corresponding Ji Dao and pin at the metal substrate back side after having electroplated;

Step 13, removal photoresistance film

Remove the photoresistance film of metallic substrate surfaces;

Step 14, load

Chip is implanted by conduction or the bonding material that do not conduct electricity at the Ji Dao back side that step 12 is formed;

Step 15, metal wire are bonded

Carry out being bonded metal wire operation between the pin that chip front side and step 12 are formed;

Step 10 six, epoxy resin plastic packaging

Complete load play line after metal substrate back etched region carry out epoxy resin plastic packaging protection;

Step 10 seven, subsides photoresistance film operation

The photoresistance film that can carry out exposure imaging is sticked at metal substrate front and the back side after step 10 six completes epoxy resin plastic packaging;

Step 10 eight, metal substrate front removal unit divide photoresistance film

The metal substrate front utilizing exposure imaging equipment that step 10 seven completes to paste photoresistance film operation carries out graph exposure, development and removes partial graphical photoresistance film, to expose the region that the follow-up needs in metal substrate front carry out etching;

Step 10 nine, etching

In step 10 eight, the region of metal substrate front removal unit point photoresistance film carries out chemical milling;

Step 2 ten, removal photoresistance film

Remove the photoresistance film of metallic substrate surfaces.