CN101814446B - Island expose and multi-salient-point island expose lead frame structure and carving and plating method thereof - Google Patents

Abstract

The invention relates to a base island exposed and multi-bump base island exposed lead frame structure and a method for engraving first and then plating, comprising a base island (1) and pins (2). The base island (1) has two groups, one One group is the first base island (1.1), and the other group is the second base island (1.2). The front and back of the pin (2) are respectively provided with a first metal layer (4) and a second metal layer (5), in the peripheral area of the pin (2), the base island (1) and the pin (2) The area between the first base island (1.1) and the second base island (1.2) and the area between the pins (2) and the pins (2) are embedded with filler-free molding compound (3 ), and make the size of the base island and the back side of the pin smaller than the size of the base island and the front side of the pin, forming a base island and pin structure with a large top and a small bottom. The beneficial effect of the invention is that: the invention has a large binding ability between the plastic package body and the metal feet.

Description

Lead frame structure with base island exposed and multi-bump base island exposed lead frame and its method of engraving first and then plating

(1) Technical field

The invention relates to a base island exposed and multi-bump base island exposed lead frame structure and a method for engraving first and then plating. It belongs to the technical field of semiconductor packaging.

(2) Background technology

There are two main types of traditional lead frame structures:

The first:

After chemical etching and surface electroplating are performed on the front of the metal substrate, a layer of high-temperature-resistant adhesive film is pasted on the back of the metal substrate to form a lead frame carrier that can be packaged (as shown in Figure 14).

The second type:

After chemical etching and surface electroplating are performed on the front side of the metal substrate, the production of the lead frame is completed (as shown in FIG. 15 ). The backside of the lead frame is then etched during the packaging process.

However, the above two lead frames have the following disadvantages in the packaging process:

The first:

1) This kind of lead frame must be pasted with a layer of expensive and high temperature resistant adhesive film on the back. So directly increased the high cost.

2) Also because the back of this kind of lead frame must be affixed with a layer of high-temperature-resistant adhesive film, so the chip loading process in the packaging process can only use conductive or non-conductive resin technology, and can not be used at all. Chip-mounting process and soft solder process, so the types of products that can be selected are relatively limited.

3) Because the back of this kind of lead frame must be pasted with a layer of high-temperature-resistant adhesive film, and in the ball soldering bonding process in the packaging process, because the high-temperature-resistant adhesive film is a soft material, Therefore, the instability of ball bonding parameters is caused, which seriously affects the quality of ball bonding and the stability of product reliability.

4) Because the back of this kind of lead frame must be affixed with a layer of high temperature resistant adhesive film, and in the plastic sealing process during the packaging process, because of the high pressure of the plastic seal, it is easy to cause penetration between the lead frame and the adhesive film. Molding compound, and the originally conductive metal pin becomes an insulating pin due to infiltration of the molding compound (as shown in Figure 16).

The second type:

This kind of lead frame structure has a half-etching process on the front of the metal substrate. Although it can solve the problem of the first lead frame, because only the half-etching work is performed on the front of the metal substrate, the plastic encapsulation compound only covers The height of half a foot is used, so the binding ability between the plastic package and the metal foot becomes smaller. If the plastic package is not attached to the PCB board very well, it is easy to cause the problem of foot drop (such as Figure 17).

Especially when the type of molding compound is filled, because the relationship between the environment of the material in the production process and the stress change of the subsequent surface mount will cause vertical cracks between the metal and the molding compound, the characteristic is that the higher the filler ratio, the harder it is The more brittle the easier it is to crack.

(3) Contents of the invention

The object of the present invention is to overcome above-mentioned deficiency, provide a kind of package cost reduction, the product variety that can be selected is wide, the quality of ball welding and the stability of product reliability are good, the restraining ability of plastic package body and metal foot is big and the base island is exposed and The multi-bump base island exposes the lead frame structure and its engraving first and then plating method.

The purpose of the present invention is achieved in this way: a base island exposed and a multi-bump base island exposed lead frame structure, including the base island and pins, the base island has two groups, one group is the first base island, the other The group is a second base island, the front of the second base island is arranged in a multi-bump structure, and a first metal layer and a second metal layer are respectively arranged on the front and back of the base island and pins, and the The area around the pin, the area between the base island and the pin, the area between the first base island and the second base island, and the area between the pin and the pin are embedded with plastic molding compound without filler, the said The filler-free molding compound connects the periphery of the lower part of the pin, the first base island and the lower part of the second base island, the base island and the lower part of the pin, and the pin and the lower part of the pin, and makes the dimensions of the base island and the back of the pin Smaller than the size of the base island and the front side of the pin, forming a base island and pin structure with a large top and a small bottom.

The production method of base island exposure and multi-bump base island exposure lead frame of the present invention is engraved first and then plated, and the method includes the following process steps:

Step 1. Take the metal substrate

Step 2, film pasting operation

The photoresist film that can be exposed and developed is respectively pasted on the front and back of the metal substrate by using the film sticking equipment.

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

Use the exposure and development equipment to expose and develop the front side of the metal substrate that has completed the film attachment operation in step 2 to remove part of the photoresist film, so as to expose the area on the metal substrate that needs to be half-etched later.

Step 4. Half etching of the front side of the metal substrate

Perform half-etching on the area where part of the photoresist film is removed from the front of the metal substrate in step 3, form a recessed half-etched area on the front of the metal substrate, and simultaneously form base islands and pins relatively. There are two groups of base islands, one group is The first base island, the other group is the second base island,

Step 5. The front and back of the metal substrate are peeled off

Remove the remaining photoresist film on the front side of the metal substrate and the photoresist film on the back side,

Step 6. Fill the semi-etched area on the front of the metal substrate with a soft sealant without filler

In step 4, a recessed half-etched area is formed on the front of the metal substrate, and a soft sealant without filler is applied, and baked at the same time, so that the soft sealant without filler is cured into a mold compound without filler,

Step 7. Laminating film on the front and back of the metal substrate

Use the film sticking equipment to paste the photoresist film that can be exposed and developed on the front and back of the metal substrate that has been filled with soft gap filler without filler.

Step 8. Remove part of the photoresist film

Removing part of the photoresist film on the front and back of the metal substrate is intended to expose the back of the first base island, the second base island and the pins, as well as the partial area of the front of the second base island, the front of the first base island and the front of the pins,

Step 9, metallization layer

The second metal layer is plated on the back of the first base island, the second base island and the pins exposed in step 8, and the first metal layer is plated on the partial area of the front side of the second base island, the front side of the first base island and the front side of the pins ,

Step 10. Remove part of the photoresist film on the back of the metal substrate

Removing part of the photoresist film on the back of the metal substrate to expose the area on the back of the metal substrate corresponding to the non-conductive and filler-free molding compound and the area on the front of the base island that is not coated with the first metal layer,

Step 11. Half etching on the back of the metal substrate

On the back side of the metal substrate, the etching process is performed again on the area not covered by the photoresist film, all the metal in the remaining part of the half-etched area in step 4 is etched away, and at the same time, the half-etching process is performed on the front side of the second base island, The front side of the second base island is etched into a multi-bump shape, and the size of the base island and the back side of the pin is smaller than the size of the base island and the front side of the pin, forming a base island and pin structure with a large top and a small bottom,

Step 12. The front and back of the metal substrate are peeled off

Peel off the remaining photoresist film on the front and back of the metal substrate.

The beneficial effects of the present invention are:

1) There is no need to paste a layer of expensive and high temperature resistant adhesive film on the back of this kind of lead frame. Therefore, the high cost is directly reduced.

2) Also because the back of this kind of lead frame does not need to be pasted with a layer of high temperature resistant adhesive film, so in addition to using conductive or non-conductive resin technology, the chip loading process in the packaging process can also use a common Chip-mounting process and soft solder process, so there are a wide range of products to choose from.

3) Because the back of the lead frame does not need to be pasted with a layer of high-temperature-resistant adhesive film, the stability of the ball bonding parameters is ensured, and the quality of the ball bonding and the stability of product reliability are guaranteed.

4) Furthermore, because this kind of lead frame does not need to be pasted with a layer of high-temperature-resistant adhesive film, the plastic sealing process in the packaging process will not cause the plastic sealing compound to penetrate between the lead frame and the adhesive film at all.

5) Since there is no filler soft sealant embedded in the area between the metal feet (pins) and the metal feet, the filler-free soft sealant is different from the conventional filler molding compound in the molding process. Cover the entire height of the metal feet together, so the binding capacity between the plastic package and the metal feet becomes larger, and there will be no more problems of falling feet.

6) Due to the method of separate etching operations on the front and back, a structure in which the size of the back base island is slightly smaller and the size of the front base island is slightly larger can be formed during the etching operation, and the upper and lower sizes of the same base island are different in size The non-filler plastic encapsulation is tighter and less likely to slip and fall off.

7) The multi-bump metal base island can disperse the thermal expansion thermal stress and cold contraction stress of the metal base island to each bump, directly reducing the different expansion coefficients between the entire metal base island and the chip The stress deformation caused by the difference from the shrinkage rate will cause reliability damage after packaging.

(4) Description of drawings

1 to 12 are schematic diagrams of each process of the production method of the exposed base island and the multi-bump base island exposed lead frame of the present invention, which is engraved first and then plated.

FIG. 13 is a schematic diagram of the structure of the lead frame with exposed base islands and exposed multi-bump base islands according to the present invention.

Figure 14 is a picture of pasting a layer of high temperature resistant adhesive film on the back of the metal substrate in the past.

Fig. 15 is a working diagram of chemical etching and surface electroplating on the front side of a metal substrate in the past.

FIG. 16 is a schematic diagram of forming insulating feet in the past.

Fig. 17 is a diagram of a footfall formed in the past.

Reference signs in the figure:

Base island 1, first base island 1.1, second base island 1.2, pins 2, molding compound without filler 3, first metal layer 4, second metal layer 5, metal substrate 6, photoresist films 7 and 8 , half-etched region 9, photoresist films 10 and 11.

(5) Specific implementation methods

The production method of base island exposure and multi-bump base island exposure lead frame of the present invention is engraved first and then plated as follows:

Step 1. Take the metal substrate

Referring to FIG. 1 , take a metal substrate 6 with an appropriate thickness. The material of the metal substrate 6 can be changed according to the functions and characteristics of the chip, such as copper, aluminum, iron, copper alloy or nickel-iron alloy.

Step 2, film pasting operation

Referring to FIG. 2 , the photoresist films 7 and 8 that can be exposed and developed are respectively pasted on the front and back of the metal substrate by using the film sticking equipment to protect the subsequent etching process.

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

Referring to FIG. 3 , use exposure and development equipment to expose and develop the front of the metal substrate that has completed the film attachment operation in step 2 to remove part of the photoresist film, so as to expose the area on the metal substrate that needs to be half-etched later.

Step 4. Half etching of the front side of the metal substrate

Referring to Figure 4, perform half-etching on the area where part of the photoresist film is removed from the front of the metal substrate in step 3, forming a recessed half-etching area 9 on the front of the metal substrate, and at the same time relatively forming the base island 1 and pin 2, the main purpose of which is to Avoid glue overflow in subsequent operations. The base island 1 has two groups, one is the first base island 1.1, and the other is the second base island 1.2.

Step 5. The front and back of the metal substrate are peeled off

Referring to FIG. 5 , the remaining photoresist film on the front side and the photoresist film on the back side of the metal substrate are removed.

Step 6. Fill the semi-etched area on the front of the metal substrate with a soft sealant without filler

Referring to Figure 6, a recessed half-etched area 9 is formed on the front side of the metal substrate in Step 4, filled with a soft filler-free sealant, and baked at the same time to promote the soft filler-free sealant to solidify into a filler-free sealant. Plastic compound 3.

Step 7. Laminating film on the front and back of the metal substrate

Referring to Fig. 7, use film sticking equipment to stick photoresist films 10 and 11 that can be exposed and developed on the front and back of the metal substrate that has been filled with soft gap filler without filler, so as to protect the subsequent metal plating. layer craft work.

Step 8. Remove part of the photoresist film

Referring to Figure 8, part of the photoresist film is removed on the front and back of the metal substrate, the intention is to expose the back of the first base island, the second base island and the pins, as well as the partial area of the front of the second base island, the front of the first base island and the front of the first base island. pin front,

Step 9, metallization layer

Referring to Fig. 9, the second metal layer 5 is plated on the back side of the first base island, the second base island and the pin exposed in step 8, and the second metal layer 5 is plated on the front side of the second base island, the front side of the first base island and the front side of the pin. Put on the first metal layer 4, so as to facilitate the tighter and firmer bonding between the metal wire and the chip area and the inner pin area of the wire during subsequent wire bonding, and at the same time increase the bonding between the plastic encapsulant with fillers in the encapsulation process Spend. The composition of the metal layer may be gold-nickel-gold, gold-nickel-copper-nickel-gold, nickel-palladium-gold, gold-nickel-palladium-gold, nickel-gold, silver or tin, etc. depending on the chip material.

Step 10. Remove part of the photoresist film on the back of the metal substrate

Referring to FIG. 10 , part of the photoresist film on the back of the metal substrate is removed to expose the area on the back of the metal substrate corresponding to the filler-free molding compound and the area on the front of the base island that is not coated with the first metal layer.

Step 11. Half etching on the back of the metal substrate

Referring to FIG. 11 , the etching process is performed again on the area not covered by the photoresist film on the back side of the metal substrate, and all the metal in the remaining part of the half-etched area in step 4 is etched away, and at the same time, the half-etched area is etched on the front side of the second base island. The etching process makes the front of the second base island etched into a multi-bump shape, and makes the size of the base island and the back of the pins smaller than the size of the base island and the front of the pins, forming a base island and pin structure with a large top and a small bottom.

Step 12. The front and back of the metal substrate are peeled off

Referring to FIG. 12 , the remaining photoresist film on the front and back of the metal substrate is peeled off.

The final product is shown in Fig. 13: in Fig. 13, base island 1, pin 2, plastic encapsulant 3 without filler, first metal layer 4 and second metal layer 5, as can be seen from Fig. 13, the base island of the present invention is exposed and The multi-bump base island exposes the lead frame structure, including the base island 1 and pins 2. The base island 1 has two groups, one group is the first base island 1.1, and the other group is the second base island 1.2. The front side of the base island 1.2 is arranged in a multi-bump-like structure, and a first metal layer 4 and a second metal layer 5 are respectively arranged on the front and back sides of the base island 1 and the pin 2, and on the periphery of the pin 2 The area, the area between the base island 1 and the pin 2, the area between the first base island 1.1 and the second base island 1.2 and the area between the pin 2 and the pin 2 are embedded with a plastic encapsulant 3 without filler, The filler-free molding compound 3 connects the periphery of the lower part of the pin, the lower part of the first base island 1.1 and the second base island 1.2, the lower part of the base island 1 and the pin 2, and the lower part of the pin 2 and the pin 2, and makes the The size of the base island and the back side of the pins is smaller than the size of the base island and the front side of the pins, forming a base island and pin structure with a large top and a small bottom.

Claims (2)

1. sinking Ji Dao and multi-convex point base island lead frame structure, comprise Ji Dao (1) and pin (2), it is characterized in that: described Ji Dao (1) has two groups, one group is first Ji Dao (1.1), another group is second Ji Dao (1.2), described first Ji Dao (1.1) front middle section sinks, second Ji Dao (1.2) is arranged to multi-convex point shape structure in the front, front at described second Ji Dao (1.2) and pin (2) is provided with the first metal layer (4), at described first Ji Dao (1.1), the back side of second Ji Dao (1.2) and pin (2) is provided with second metal level (5), in pin (2) periphery, zone between pin (2) and first Ji Dao (1.1), zone between first Ji Dao (1.1) and second Ji Dao (1.2), zone between zone between second Ji Dao (1.2) and the pin (2) and pin (2) and the pin (2) is equipped with packless plastic packaging material (3), described packless plastic packaging material (3) is with pin (2) periphery, bottom, pin (2) and first Ji Dao (1.1) bottom, first Ji Dao (1.1) and second Ji Dao (1.2) bottom, second Ji Dao (1.2) links into an integrated entity with pin (2) bottom with pin (2) bottom and pin (2), and make described Ji Dao (1) and pin (2) back side size less than Ji Dao (1) and the positive size of pin (2), form up big and down small Ji Dao and pin configuration.

2. the first-engraving last-plating method of sinking Ji Dao as claimed in claim 1 and multi-convex point base island lead frame structure is characterized in that described method comprises following processing step:

Step 1, get metal substrate

Step 2, pad pasting operation

Utilize film sticking equipment to stick the photoresist film that can carry out exposure imaging respectively at the front and the back side of metal substrate,

Step 3, the positive part photoresist film of removing of metal substrate

The metal substrate front that utilizes exposure imaging equipment that step 2 is finished the pad pasting operation is carried out exposure imaging and is removed the part photoresist film, exposing the zone that follow-up needs etch partially on the metal substrate,

Step 4, metal substrate front etch partially

The positive zone of removing the part photoresist film of metal substrate in the step 3 is etched partially,, form Ji Dao and pin simultaneously relatively in the positive half-etched regions that forms depression of metal substrate, described Ji Dao has two groups, one group is first Ji Dao, and another group is second Ji Dao

The film operation is taken off at step 5, the positive back side of metal substrate

The positive remaining photoresist film of metal substrate and the photoresist film at the back side are removed,

Step 6, the packless soft gap filler of the positive half-etched regions full-filling of metal substrate

In the positive half-etched regions that forms depression of step 4 metal substrate, packless soft gap filler in the full-filling, and toast simultaneously, impel packless soft underfill cures to become packless plastic packaging material,

Step 7, the pad pasting operation of the positive back side of metal substrate

Utilize film sticking equipment to stick the photoresist film that can carry out exposure imaging respectively at the front and the back side of the metal substrate of finishing the packless soft gap filler operation of full-filling,

Step 8, removal part photoresist film

In the front of metal substrate and the back side remove the part photoresist film, purpose is to expose the back side of Ji Dao and pin and the front of the second basic island front regional area and pin,

Step 9, metal cladding

The Ji Dao that exposes in step 8 and the back side of pin plate second metal level, plate the first metal layer in the front of the second basic island front regional area and pin,

Step 10, removal metal substrate back portion photoresist film

Remove metal substrate back portion photoresist film, with zone between the zone between zone, first Ji Dao and the second basic island of the zone between the zone, first Ji Dao and the pin that expose pin periphery, the metal substrate back side, the positive central authorities in the first basic island, zone, second Ji Dao and the pin that front, the second basic island does not plate the first metal layer and the zone between pin and the pin

Step 11, the metal substrate back side etch partially

The etch process operation is carried out once more to the zone that is not covered by photoresist film in the back side at metal substrate, the metal of step 4 half-etched regions remaining part is all etched away, front to described first Ji Dao and second Ji Dao etches partially simultaneously, front, first basic island middle section is sunk, make the second basic island front-side etch become the multi-convex point shape, and make described Ji Dao and pin back side size less than Ji Dao and the positive size of pin, form up big and down small Ji Dao and pin configuration

The film operation is taken off at step 12, the positive back side of metal substrate

The photoresist film of metal substrate front and back remainder is removed.

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