KR100492491B1 - Composite film and lead frame adhering this film - Google Patents

Abstract

The present invention relates to a heat-resistant composite film used in a semiconductor package such as a LOC, COL, etc. for bonding a semiconductor chip and a lead frame, or a semiconductor package such as a composite lead frame with a heat sink, and a lead frame to which the composite film is bonded. In particular, it is an object of the present invention to provide a lead frame with a composite film having high reliability by preventing burrs and foreign matter from being punched.

The present invention, in order to achieve the above object, in a composite film having a structure in which an adhesive is laminated on a heat resistant base film, the elastic modulus ratio of the composite film and the base film and the interfacial adhesion between the base film and the adhesive of the composite film A composite film characterized by satisfying the following formulas (1) and (2) and a lead frame to which the composite film is attached are disclosed.

(1) R = E / E _B , 0.5 ≦ R <1.0

(2) F _AD ≥150 / R + 300

Description

Composite film and lead frame adhering this film}

The present invention relates to a composite film and a composite film used in a semiconductor package such as a lead on chip (LOC) and a chip on lead (COL) for bonding a semiconductor chip and a lead frame or a composite lead frame with a heat sink. To an attached leadframe.

Composite with adhesive laminated on base film to bond leadframe and semiconductor chip in semiconductor package such as lead on chip (LOC), chip on lead (COL) or composite leadframe with heat sink Film is used

In general, the composite film is attached to the required portion of the lead frame by punching. When punching at room temperature, the composite film has high normal stress and shear stress in the form of elongation and compression in the composite film. The foreign matter in the form of powder and yarn is generated. Such foreign matters and burrs are a cause of lowering the yield and productivity of the lead frame to which the film is attached. In addition, burrs and foreign substances generated in the composite film have a fatal effect on the reliability of the semiconductor package chip.

In order to improve this, USP 5,593,774 and USP 5,998,020 propose a method of minimizing burrs and foreign substances generated in a composite film by using a film having a certain range of edge tearing resistance as a base film of the composite film. It was.

However, since the burrs and foreign substances generated when the composite film is punched on the lead frame are generated in the adhesive film as well as the base film, there is not a method of simply limiting the edge insulation resistance of the base film as set forth in the above patents. It is not practical.

An object of the present invention is to provide a composite film for a semiconductor package with high yield and productivity when manufacturing a semiconductor package by not generating foreign substances and burrs during punching of the composite film. Still another object of the present invention is to provide a lead film with a composite film having high reliability, which is attached to a required portion of the lead frame by punching the composite film according to the present invention.

The present invention provides a composite film and a lead frame to which the composite film is attached to satisfy the specific relationship that the elastic modulus of the composite film and the base film and the interfacial adhesion between the base film and the adhesive are described below. present. Hereinafter, the present invention will be described in detail.

The present inventors have studied the relationship between the occurrence of foreign matter and burrs during punching of the composite film. As a result, the concentrated stress (elastic coefficient x strain) acting on the interface between the base film and the adhesive layer of the composite film causes different deformations in the composition of the composite film. This confirmed that interfacial peeling occurred. In general, composite materials are known to concentrate stress at the interface of dissimilar materials when stress is applied. That is, when the adhesion between the base film and the adhesive of the composite film is weak, the concentrated stress received during punching is concentrated on the interface of the composite film, and this stress concentration causes the interfacial peeling on the punched cut surface. As the interfacial adhesion increases, the interfacial peeling phenomenon is transferred to burrs and foreign bodies. In addition, when the interfacial adhesion reaches a certain level, burrs and foreign matters are remarkably reduced.In the case where the interfacial adhesion properties of the base film and the adhesive of the composite film are the same, the similarity of the elastic modulus of the base film and the composite film is, The reason for this is that the greater the difference in the elastic modulus between the base film and the composite film when the stress is concentrated, the different the strain of the base film and the composite film. In other words, the greater the difference in elastic modulus, the greater the difference in strain rate, and the easier the interface peeling occurs. Of course, in order to reduce the concentrated stress during punching, various mechanical methods such as optimally adjusting the clearance of the punching tool may be attempted. However, the inventors of the present invention suggest that burrs and foreign materials of the composite film are described in the composite film. The invention was found to be closely related to the interfacial adhesion between the film and the adhesive layer and the elastic modulus.

Specifically, in the composite film having a structure in which an adhesive is laminated on a base film, the modulus of elasticity of the composite film and the base film is E, E _B and the interfacial adhesion between the base film and the adhesive of the composite film is F _AD . When the elastic modulus and interfacial adhesion in the case satisfy the following formula (1), (2) relates to a composite film and a lead frame with the composite film.

(1) R = E / E _B , 0.5≤R <1.0

(2) F _AD ≥ 150 / R + 300

In Equation (1), (2), E (GPa) is the elastic modulus of the composite film, E _B (GPa) is the elastic modulus of the base film, the unit GPa of the elastic modulus is 10 ⁹ N / m ² , F _AD (gf / 10 mm) represents the interfacial adhesion between the base film of the composite film and the adhesive.

In the present invention, the composite film is manufactured through a drying process after applying the adhesive on both sides of the base film. There is a method of coating and drying the adhesive on the surface of the base film and then drying and coating the adhesive on the back side, there is a method of coating the adhesive on both sides simultaneously or sequentially and then drying, and also different adhesives may be applied to both sides. .

The base film used in the present invention is a heat-resistant engineering plastic prepared by mixing one or a combination of polyimide, polyamide, polysulfone, polyphenylene sulfide, polyether ether ketone, polyacrylate, and polyisulfone Films are suitable, with a preferred thickness being on the order of 10-150 μm, more preferably in the range of 20-100 μm.

Since the composite film of the present invention is used in a high temperature process of 300 ° C. or higher during the manufacture of a semiconductor package, the base film is required to have a high glass transition temperature and a low thermal expansion coefficient, in particular, a glass transition temperature higher than 250 ° C., and a thermal expansion coefficient (ASTM D). -691-91) is preferably 30 ppm / 占 폚 or less.

Various methods can be used to achieve high adhesion between the base film and the adhesive. Among them, surface treatment methods include chemical treatments such as alkali treatment, silane coupling treatment, and physical treatment methods such as sand blasting, plasma, corona treatment, and the like. Depending on the film, it is possible to apply a combination of surface treatments in combination. Among them, the plasma treatment method and the sand blasting method are the most effective methods in terms of improving adhesion.

On the other hand, a method of using a coextruded base film prepared by co-extrusion of a back surface layer having a glass transition temperature of 150 to 300 ° C. with a thickness of 0.1 to 5 μm on the back surface of the base film when the base film is prepared, It is a method to increase the adhesive strength of the adhesive. In this case, the glass transition temperature of the layer is preferably at least 30 ° C lower than the glass transition temperature of the base film, and the thinner the coextrusion thickness, the better. Finally, there is also a method of improving the adhesion between the base film and the adhesive by applying a primer (Primer) coating between the base film and the adhesive. A primer having a glass transition temperature of 200 ° C. or less may be coated with an adhesive after preliminary coating on both sides of the base film to 1 μm or less, more preferably 0.2 μm or less. The primer at this time should have a lower glass transition temperature than the adhesive, but preferably 50 ° C. or less. In addition, the adhesion can be improved by adjusting the drying temperature after coating the adhesive or by selecting and blending the solvent appropriately.

The adhesive used in the present invention is a heat-resistant thermoplastic resin as a main component and the glass transition temperature is suitable between 135 ℃ to 250 ℃, the thermoplastic resin having a weight average molecular weight of 15,000 or more, polyimide-based or polyamide-based less than 100,000 Adhesive is suitable. The polyimide here includes not only general polyimide but also resins having imide bonds such as polyamideimide, polyesterimide, polyimideim.

If the glass transition temperature of the heat-resistant adhesive is lower than 135 ° C, problems such as the internal lead move during the wire bonding process occur. If the glass transition temperature is higher than 250 ° C, the adhesion temperature during the high temperature bonding process of the lead or chip is too high. It becomes high and the problem of adhesion time becoming too long arises. On the other hand, when the adhesive is thermoplastic, when the weight average molecular weight of the adhesive is less than 15,000, the adhesive seriously contaminates the punching machine during punching, and when the molecular weight exceeds 100,000, problems such as an increase in viscosity during coating occur. do.

The adhesive of the present invention may adjust the modulus of elasticity by adding organic and inorganic particles, and in particular, a coupling agent may be added to improve the bonding strength between the inorganic particles and the heat resistant adhesive. Coupling agents include silane coupling agents such as vinyltrimethoxyoxy, vinyltriethoxysilane, gamma-methacryloxy-propyltrimethoxysilane, and titanite. (titanate), aluminum chelate (zircoaluminate) and the like can be used. The adhesive solution is prepared by dissolving an adhesive whose main component is a thermoplastic resin in an organic solvent. In addition, the adhesive solution may be a precursor structure of the heat resistant adhesive that is changed into a heat resistant adhesive by a heat treatment or the like after the coating process. For example, polyamide acid, a precursor of polyimide, is converted to polyimide by heat treatment. On the other hand, if a small amount of the surfactant is added in order to improve the coating property can not only produce a good coating surface, but also improve the wettability (Wetting property) with the base film to improve the adhesion between the base film and the adhesive.

When the adhesive solution is coated on the base film, a comma, reverse, or die coater may be used. Among these, the die-shaped coater is most preferred in terms of suppressing foreign particles and bubble generation. In the form of a drying unit for drying the polyimide adhesive solution after coating, a roll carrier form in which a film is placed on a roll and the film is moved is generally used to coat one or both sides of the film. In addition, in the case of coating on both sides, a floating carrier form in which the film is conveyed without contacting a roll or the like is used. In the coating process, the method of coating and drying the adhesive on both sides of the surface and the back side simultaneously or sequentially is an advantageous method in terms of productivity and processability.However, since the floating method must be used, the drying temperature and air volume during the initial drying should be carefully examined and optimized. .

After the adhesive solution is coated on the base film, the adhesive solution should be slowly dried for a period of 3 to 20 minutes between 50 to 250 ° C. in order to remove the solvent. If heated rapidly, bubbles generated in the adhesive layer may cause poor adhesion during adhesion with the lead frame, thereby deteriorating the reliability of the semiconductor. Therefore, it is preferable to form a stable coating layer free of bubbles by raising the drying temperature as slowly as possible until 90% of the solvent of the adhesive applied to the base film is dried.

The thickness of the adhesive layer formed on the base film is preferably in the range of 5 to 50㎛ thickness of one layer, if the thickness of the adhesive is less than 5㎛ may lead to a low adhesion when bonding with the lead frame.

The lead frame of the present invention consists of a composite film and lead frame attached to the lead frame by punching the composite film developed in the present invention. The leadframe may be of any type of construction, with typical shapes in which an inner lead portion is attached to a chip, an outer lead portion is connected to an external circuit, and a composite film is attached to a predetermined position. The lead frame to which the composite film is attached is manufactured by bonding the composite film to the lead frame. Thus, the semiconductor package manufactured using the lead frame to which the composite film is attached according to the present invention has excellent reliability.

For example, to facilitate the process of attaching one adhesive layer of the composite film to the leadframe, a punching machine is applied to the leadframe strip continuously at a predetermined lead frame position at a pressure of 0.5 to 70 MPa and a time of 0.2 to 3 seconds. The composite film is attached. In addition, according to the shape of the chip, the position of the chip attached to the lead frame, the shape of the lead frame, etc., the shape of the composite film cut by punching is various. When punching the composite film, the lead frame is heated to about 200 to 500 ° C.

As such, the burrs and foreign matters generated during punching cause problems in the wire bonding process. When using the composite film, the base film, and the adhesive having elastic modulus and interfacial adhesion to satisfy the relation according to the present invention, such burrs and It was confirmed experimentally that the generation of foreign bodies can be suppressed.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the scope of the present invention is not limited thereto. And, among the characteristic values mentioned in the following Examples and Comparative Examples, the glass transition temperature is a value measured by JIS K 7121 evaluation method, the elastic modulus is a value measured at room temperature (25 ℃) by ASTM D 882, the interfacial adhesion Is the value measured by 180 degreeC peeling (PEEL) experiment (measurement temperature: 25 degreeC, peeling rate: 50mm / min).

Example 1

A polyimide adhesive having a glass transition temperature of 205 ° C. after plasma treatment of a 75 μm polyimide film having a glass transition temperature of 300 ° C. or higher, a thermal expansion coefficient of 12 ppm / ° C., and a soft tear resistance of 77 kgf / 20 mm. The average molecular weight of 50,000, Mw / Mn = 2.1) is applied to both sides with a thickness of 15.0㎛, dried to a total thickness of 105.0㎛, the ratio of the elastic modulus of the composite film to the base film is 0.80, the interfacial adhesion is 620gf / 10mm Composite film was prepared. The composite film was placed on a nickel alloy 42 lead frame heated to 380 ° C., and the composite film was punched with a punching machine and pressed for 10 seconds at a pressure of 10 MPa to prepare a lead frame having a composite film. Observation of the edge of the punched composite film under a microscope revealed no burrs and foreign objects.

Comparative Example 1

A composite film was prepared in the same manner as in Example 1 without performing plasma treatment on a 75 μm polyimide film having a glass transition temperature of 300 ° C. or higher, a thermal expansion coefficient of 12 ppm / ° C., and a soft edge resistance of 77 kgf / 20 mm. A composite film was prepared in which the ratio of the elastic modulus of the composite film to the film was 0.80 and the interfacial adhesion of the composite film was 420 gf / 10 mm. In the same manner as in Example 1, the composite film was prepared with a lead frame to which the composite film was attached. Observation of the edge of the punched composite film under a microscope revealed burrs and foreign objects.

Example 2

Polyimide adhesive having a glass transition temperature of 157 ° C immediately after corona treatment of a 50 μm polyimide film having a glass transition temperature of 300 ° C. or more, a thermal expansion coefficient of 12 ppm / ° C., and a soft tear resistance value of 44 kgf / 20 mm. A weight average molecular weight of 50,000, Mw / Mn = 2.1) was applied on both sides with a thickness of 15.0 μm and dried to obtain a composite film having a total thickness of 80 μm, an elastic modulus ratio of 0.75, and an interfacial adhesion of the composite film of 535 gf / 10 mm. Prepared. The composite film was placed on a nickel alloy 42 lead frame heated to 380 ° C., and the composite film was punched with a punching machine, and then pressed with a lead of the lead frame below at a pressure of 10 MPa for 0.6 seconds to prepare a lead frame having a composite film. . Observation of the edge of the punched composite film under a microscope showed no burrs and foreign objects.

Comparative Example 2

A polyimide adhesive having a glass transition temperature of 205 ° C. on a 50 μm polyimide film having a glass transition temperature of 300 ° C. or higher, a thermal expansion coefficient of 12 ppm / ° C., and a soft tear resistance of 47 kgf / 20 mm (weight average molecular weight of 50,000 , Mw / Mn = 2.1) was applied on both sides with a thickness of 15.0 μm and dried to prepare a composite film having a total thickness of 80 μm, an elastic modulus ratio of 0.77, and an interface adhesion of 450 gf / 10 mm. The composite film was placed on a nickel alloy 42 lead frame heated to 380 ° C., and the composite film was punched with a punching machine and pressed for 10 seconds at a pressure of 10 MPa to prepare a lead frame having a composite film. Observation of the edge of the punched composite film under a microscope revealed burrs and foreign objects.

Example 3

A polyimide adhesive having a glass transition temperature of 155 ° C. on a 50 μm polyimide film having a glass transition temperature of 300 ° C. or more, a thermal expansion coefficient of 10 ppm / ° C. or less and a soft tear resistance of 40 kgf / 20 mm (weight average molecular weight This 35,000, Mw / Mn = 2.1) was applied to both sides with a thickness of 25.0㎛ and dried to prepare a composite film having a total thickness of 100㎛, an elastic modulus ratio of 0.57 and an interfacial adhesion of 610gf / 10mm. The composite film was placed on a nickel alloy 42 lead frame heated to 320 ° C., and the composite film was punched with a punching machine and pressed for 10 seconds at a pressure of 10 MPa to prepare a lead frame having a composite film. Observation of the edge of the punched composite film under a microscope revealed no burrs and foreign objects.

Comparative Example 3

A polyimide adhesive having a glass transition temperature of 155 ° C. on a 50 μm polyimide film having a glass transition temperature of 300 ° C. or higher, a thermal expansion coefficient of 10 ppm / ° C. or lower, and a soft tear resistance of 55 kgf / 20 mm (weight average molecular weight This 35,000, Mw / Mn = 2.1) was applied to both sides with a thickness of 25.0㎛ and dried to prepare a composite film having a total thickness of 100㎛, elastic modulus ratio 0.45 and interfacial adhesion of 650gf / 10mm. The composite film was placed on a nickel alloy 42 lead frame heated to 400 ° C., and the composite film was punched with a punching machine and pressed for 10 seconds at a pressure of 10 MPa to prepare a lead frame having a composite film. Observation of the edge of the punched composite film under a microscope revealed no burrs and foreign objects.

Comparative Example 4

A polyimide adhesive having a glass transition temperature of 155 ° C. on a 50 μm polyimide film having a glass transition temperature of 300 ° C. or more, a thermal expansion coefficient of 10 ppm / ° C. or less and a soft tear resistance of 40 kgf / 20 mm (weight average molecular weight This 50,000, Mw / Mn = 2.1) was applied to both sides with a thickness of 25.0㎛ and dried to prepare a composite film having a total thickness of 100㎛, an elastic modulus ratio of 0.57 and an interfacial adhesion of 510gf / 10mm. The composite film was placed on a nickel alloy 42 lead frame heated to 320 ° C., and the composite film was punched with a punching machine, and then pressed with a lead of the lead frame below at a pressure of 10 MPa for 0.6 seconds to prepare a lead film having a composite film. . Observation of the edge of the punched composite film under a microscope revealed burrs and foreign objects.

Example 4

Polyimide adhesive having a glass transition temperature of 155 ° C on both sides of a 25 μm polyimide film having a glass transition temperature of 300 ° C. or more, a thermal expansion coefficient of 10 ppm / ° C. or less and a soft tear resistance of 15 kgf / 20 mm. An average molecular weight of 35,000, Mw / Mn = 2.5) was applied to both sides by 15.0㎛ and dried to prepare a composite film having a total thickness of 55.0㎛, an elastic modulus ratio of 0.55 and an interfacial adhesion of 625g / 10mm. The composite film was placed on a nickel alloy 42 lead frame heated to 300 ° C., and the composite film was punched with a punching machine and pressed for 10 seconds at a pressure of 10 MPa to prepare a lead frame having a composite film. Observation of the edge of the punched composite film under a microscope revealed no burrs and foreign objects.

Comparative Example 5

A polyimide adhesive having a glass transition temperature of 155 ° C. on a 25 μm polyimide film having a glass transition temperature of 300 ° C. or more, a thermal expansion coefficient of 10 ppm / ° C. or less, and a soft tear resistance of 27 kgf / 20 mm (weight average molecular weight This 35,000, Mw / Mn = 2.5) was applied to both sides by 15.0㎛ and dried to prepare a composite film having a total thickness of 55.0㎛, an elastic modulus ratio of 0.52 and an interfacial adhesion of 500g / 10mm. The composite film was placed on a nickel alloy 42 lead frame heated to 380 ° C., and the composite film was punched with a punching machine and pressed for 10 seconds at a pressure of 10 MPa to prepare a lead frame having a composite film. Observation of the edges of the punched composite film under a microscope resulted in burrs and foreign objects.

Example 5

Polyimide adhesive having a glass transition temperature of 125 ° C on both sides of a 25 μm polyimide film having a glass transition temperature of 300 ° C. or more, a thermal expansion coefficient of 10 ppm / ° C. or less and a soft tear resistance of 27 kgf / 20 mm (weight average Molecular weight of 35,000, Mw / Mn = 2.5) was coated on each side by 0.1㎛, and polyimide adhesive (weight average molecular weight 35,000, Mw / Mn = 2.5) with glass transition temperature of 155 ℃ was applied on both sides by 15.0㎛. After coating and drying, a composite film having a total thickness of 55.2 μm, an elastic modulus ratio of 0.52, and an interface adhesion of 700 g / 10 mm was prepared. The composite film was placed on a nickel alloy 42 lead frame heated to 300 ° C., and the composite film was punched with a punching machine and pressed for 10 seconds at a pressure of 10 MPa to prepare a lead frame having a composite film. Observation of the edge of the punched composite film under a microscope revealed no burrs and foreign objects.

The properties of the Examples and Comparative Examples are shown in Table 1 below.

TABLE 1

As can be seen from the above examples and comparative examples, the composite film satisfying the present invention does not generate burrs or foreign matters when punching on the lead frame and does not cause interfacial peeling, thus providing a lead frame with a composite film having high reliability. It has the usefulness to do it.

Claims (7)

In a composite film having a structure in which an adhesive is laminated on a base film, when the elastic modulus of the composite film and the base film is E, E _B and the interfacial adhesion between the base film and the adhesive of the composite film is F _AD , the elastic modulus ratio And the interfacial adhesion between the following formulas (1) and (2). (1) R = E / E _B , 0.5 ≦ R <1.0 (2) F _AD ≥150 / R + 300 (E is the elastic modulus (GPa) of the composite film, E _B is the elastic modulus (GPa) of the base film, F _AD represents the interfacial adhesion of the base film and the adhesive of the composite film (gf / 10nm)) The composite film of claim 1, wherein the base film has a glass transition temperature of 250 ° C. or more and a thermal expansion coefficient of 30 ppm / ° C. or less. The composite film of claim 1, wherein the adhesive has a glass transition temperature in the range of 135 to 250 ° C. and a weight average molecular weight of the resin in the range of 15,000 to 100,000. The composite film of claim 1, wherein the thickness of one layer of the adhesive is in the range of 5 to 50 μm. The method of claim 1, wherein the base film is polyimide, polyamide, polysulfone, polyphenylene sulfide, polyether ether ketone, polyacrylate and polyisulfone selected from the group consisting of, or a mixture thereof Composite film. The composite film of claim 3, wherein the adhesive is selected from polyimide or polyamide. In a lead frame with a composite film having a structure in which an adhesive is laminated on a base film, the elastic modulus of the composite film and the base film is E and E _B , respectively, and the interfacial adhesion between the base film and the adhesive of the composite film is F _AD . The lead film with a composite film, characterized in that the elastic modulus and the interfacial adhesion force is punched with a punching machine to a composite film satisfying the following formulas (1) and (2). (1) R = E / E _B , 0.5 ≦ R <1.0 (2) F _AD ≥150 / R + 300 (E is the elastic modulus (GPa) of the composite film, E _B is the elastic modulus (GPa) of the base film, F _AD represents the interfacial adhesion of the base film and the adhesive of the composite film (gf / 10nm))