KR101197777B1 - Leadframe and method of manufacturig same - Google Patents

Abstract

The present invention provides a die pad portion short-circuited with a lead portion composed of a first metal by an insulating portion composed of an insulating material; A circuit pattern formed of a second metal on the lead portion or the insulating portion; An inner lead formed on an upper surface of the circuit pattern and positioned adjacent to the die pad part; And an outer lead formed on a lower surface of the lead part, and a manufacturing method thereof. As a result, cost is reduced by reducing wires connected to the chip and the circuit pattern, and a large number of signal transmission systems are established and thinned by connecting the lead part and the chip with a fine and uniform circuit pattern. In addition, due to the method of printing the metal paste, the number of processes is reduced, and unlike the PCB substrate in which the lead portion and die pad surface connecting the circuit are formed by plating, the metal member is used as it is to improve signal transmission and thermal conductivity. .

Semiconductor Chip Packages, Supports, Wires

Description

LEAD FRAME AND METHOD OF MANUFACTURING THEREOF {LEADFRAME AND METHOD OF MANUFACTURIG SAME}

The present invention relates to a lead frame and a method of manufacturing the same.

Semiconductor packaging refers to a process in which individual chips made by the wafer process are electrically connected so that they can be used as actual author parts, and sealed and packaged to protect against external impact.

 Typically, a single wafer is made from dozens or even hundreds of chips printed with the same electrical circuit. These individual chips cannot, by themselves, serve as electronic components. Therefore, it is necessary to make an electric cable connected to the outside in order to receive the electrical signal from the outside to deliver the electrical signal operated inside the chip. In addition, chips contain very fine circuitry, which can be easily damaged by moisture, dust and external shocks. After all, the chip itself on the wafer surface is not a complete product until it is mounted on a printed circuit board (PCB) as an electronic component. Therefore, the packaging process is to finalize the chip to make electrical connections to the chip on the wafer and seal the packaging to withstand external shocks so that the chip can serve as a complete individual electronic device.

In addition, in manufacturing a semiconductor package, a lead frame plays an important role in supplying input / output means for chip mounting and signal transmission, and various types of lead frames for highly integrated signal transmission have been developed.

In general, the shape of a lead frame manufactured is a die pad and a lead portion using an etching method or a stamping method. However, the conventional method of manufacturing the lead frame is not easy to form a multi-row lead required for high integration of the semiconductor.

In addition, a lead frame manufactured using a recently developed two-stage etching is limited in reducing the implementation pitch of the inner lead, thereby limiting the number of lead pins that can be implemented. In addition, according to the conventional method, in order to mount the lead frame on the PCB substrate, there is a process troublesome process of performing tin plating for soldering.

In particular, when the circuit pattern of the lead frame is implemented by two-stage etching, a circuit pattern having a constant thickness cannot be formed due to isotropic etching. That is, the edge part cut | disconnected by etching takes a concave shape, and the part in which the metal part which comprises an inner lead and an outer lead is located is comprised higher than other parts. This will act as a limit of thinning and miniaturization of the circuit pattern.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a lead frame having a more integrated signal transmission system and a lead frame manufacturing method implementing the same in a simpler process.

A lead frame according to an embodiment of the present invention includes a die pad portion spaced apart from a lead portion composed of a first metal by an insulating portion composed of an insulating material; A circuit pattern formed of a second metal on the lead portion and the insulation portion; An inner lead formed on an upper surface of the circuit pattern and positioned adjacent to the die pad part; And an outer lead formed on the lower surface of the lead portion, and the circuit pattern may be formed separately from the lead portion to form a finer circuit pattern.

In particular, the thickness of the circuit pattern is constant, because the circuit pattern due to the printing of the metal paste, not the etching process is not formed in the concave shape of the corner portion.

Here, the lead portion is characterized in that the width of the upper direction is narrower than the width of the lower direction.

According to one or more exemplary embodiments, a method of manufacturing a lead frame includes: (a) forming an insulation part groove, a die pad part, and a lead part by performing half etching on a metal substrate; (b) forming an insulating part by filling an insulating material in the insulating part groove; And (c) forming a circuit pattern by printing a metal paste on the lead portion or the insulating portion to be insulated from the die pad portion, wherein step (c) comprises: (c1) a circuit on the lead portion; Forming a pattern; And (c2) etching the lower surface of the metal substrate to insulate the die pad portion from the lead portion. (C1) etching the lower surface of the metal substrate to insulate the die pad portion from the lead portion; And (c2) forming a circuit pattern on the lead portion.

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Here, the material of the circuit pattern of step (c) may be made of one or more of copper (Cu), aluminum (Al), and magnesium (Mg).

The lead frame manufacturing method may further include (d) forming a wire bonding pad on an upper surface of the circuit pattern or the die pad, or forming a solder mounting pad on the lower surface of the lead portion or the die pad. .

In particular, step (c) is characterized in that the step of printing the metal paste so that the thickness of the circuit pattern is constant.

According to the present invention, the cost is reduced by reducing the wires connected to the chip and the circuit pattern, and the lead part and the chip are connected in a fine and uniform circuit pattern to build a large number of signal transmission systems and at the same time, to realize a thinning. . In addition, due to the method of printing the metal paste, the number of processes is reduced, and unlike the PCB substrate in which the lead portion and die pad surface connecting the circuit are formed by plating, the metal member is used as it is to improve signal transmission and thermal conductivity. .

Hereinafter, with reference to the accompanying drawings will be described in detail a method for manufacturing a lead frame according to a preferred embodiment. In the following description, well-known functions or constructions are not described in detail to avoid unnecessarily obscuring the subject matter of the present invention.

In the description of the embodiments, "on" and "under" include both directly and "indirectly" formed through other components. The reference to the top or bottom of the clothes will be described with reference to the drawings.

1A to 1I are cross-sectional views of each step of the lead frame manufacturing method according to an embodiment of the present invention.

As shown in FIG. 1A, a metal substrate 110 serving as a circuit main body is prepared. The metal substrate 110 is preferably copper (Cu). Metal members, such as copper alloy, iron (Fe), and an iron alloy which are conductive materials, can also be used. The thickness of the metal substrate 110 to be used here is preferably 10 mils (1 mil = 1 / 1,000 inch) or less, more preferably 5 mils or less.

Thereafter, as shown in FIG. 1B, photoresist 120 is formed on the upper and lower portions of the metal substrate 110. In this case, the photoresist 120 may be formed of a liquid type photo resist 120 (LPR: Liquid Photo Resist), a film type photo resist 120 (DFR: Dry Film Resist), or the like. The photoresist 120 is exposed and developed by a photolithography process using a photomask 130 on the upper and lower portions of the metal substrate 110.

In addition, although the application of the photoresist 120 may be applied only to the upper surface of the metal substrate 110, in order to protect the member on the lower surface, double-sided coating is preferable.

Here, the photomask 130 includes a blocking region S1 in which a blocking layer is formed on a quartz substrate, and a transmission region S2 in which only a quartz substrate is present. The photomask 130 located above the metal substrate 110 has a transmissive region positioned at the position where the insulating portion groove is to be formed to transmit ultraviolet rays during the exposure process, thereby removing the photoresist 120 of the portion where the insulating portion groove is to be positioned after the developing process. do. Here, the photoresist 120 may be of a type in which a portion exposed to ultraviolet rays is removed and a type in which a portion not exposed to ultraviolet rays is removed. In this step, the former photoresist 120 is used.

Subsequently, half etching is performed on the metal substrate 110 to form an insulation groove, which is a space in which the insulator will be filled. In this case, the depth to be etched can be adjusted as needed.

In the case of etching in this way, due to the isotropic etching, as shown in FIG. 1C, the inner corner portion where the groove is formed is also etched to realize a concave shape. That is, the width of the upper direction of the lead portion 180 becomes narrower than the width of the lower direction, it is difficult to implement a lead portion of a constant thickness by etching.

Thereafter, the photoresist 120 is peeled off to form the shape of the metal substrate 110 as shown in FIG. 1C. The shape of the metal substrate 110 shown in FIG. 1C includes a lead portion 180, an insulation portion groove, and a die pad portion 115.

And, as shown in Figure 1d, a resin (resin) capable of insulating function is filled on top of the metal substrate 110. Here, in the case of using the liquid-type resin, after filling the insulating groove through the screen printing must go through a step (not shown) to increase the hardness of the liquid-type resin. In addition, in the case of using a film-type resin (for example, PP (Prepreg), RCC (Resin Coated Copper)), the resin is laminated on the metal substrate 110 and then filled with the resin by applying a predetermined pressure and temperature.

Next, as shown in FIG. 1E, a polishing process is performed to expose portions of the resin that do not need to be filled, that is, upper surfaces of the lead portion 180 and the die pad portion 115.

Here, another method of filling the half-etching surface is to use solder resist (SR). In the case of the liquid type SR, after coating through screen printing, exposure is performed using the pattern mask 130. The lighted portion is removed through the development process, exposing the member surface of the region that does not need to fill the resin, and then curing the SR filled in the half etching region. In this case, the polishing process may be performed to make the height of the filled resin and the exposed metal surface the same. In addition, a DFSR (Dry Film Solder Resist) existing as a film type may be used. The DFSR is laminated to the half etched metal substrate 110. Thereafter, the development is performed after the exposure is performed using the pattern mask 130. These DFSRs have similar properties to SRs and require a curing step.

Thereafter, as shown in FIG. 1F, the circuit pattern 160 is formed on the upper surface of the lead portion and the insulating portion 150 by using a metal paste. More specifically, for example, a screen printing method may be used in which a metal paste is pushed into a squeegee and printed on a metal mask on which a desired circuit pattern is formed. As a result, a fine and constant thickness circuit pattern can be formed easily.

The thickness of the circuit pattern 160, that is, the height of the circuit pattern 160 may be controlled by adjusting the number of times of printing (for example, thickening when two or more times) or by adjusting the viscosity of the paste. In addition, the width of the circuit pattern can be adjusted by adjusting the width of the circuit pattern of the metal mask used when printing the metal paste.

Here, as the metal paste, a mixed paste using one or two or more of copper (Cu) paste, aluminum (Al) paste, and magnesium (Mg) paste may be used, and other conductive materials may be used. In particular, when the material of the metal substrate 110 is Cu, it is preferable to use a Cu paste composed of the same components and high in thermal conductivity. The circuit pattern 160 should have a separation distance to be insulated from the die pad unit 115. The upper surface of the lead frame on which the circuit pattern 160 is formed is shown in FIG. 2.

In particular, the circuit pattern formed by printing the metal paste is different in form from the circuit pattern formed by the conventional etching technique. That is, in the prior art, by plating a metal part such as an inner lead and an outer lead first, and then forming a circuit pattern through etching, the circuit pattern part on which the outer lead and the inner lead part (located on the edge part due to etching) is formed. It becomes higher than other parts.

On the other hand, the present invention is not by etching, as shown, the edge portion is not cut so that the circuit pattern can be formed to a constant thickness, as a result, it is possible to thin the entire lead frame.

2 is a top view illustrating a circuit pattern of a lead frame according to an embodiment of the present invention. Referring to FIG. 2, the distance between the circuit patterns 160 may be configured very finely, thereby establishing a large number of signal transmission systems.

Next, as shown in FIG. 1G, the bottom surface of the metal substrate 110 is etched entirely. The reason for this is to allow the lead portion 180 and the die pad portion 115 to be electrically insulated. As a result, the lead portion 180 and the die pad portion 115 are spaced apart with the insulating portion 150 interposed therebetween.

Here, steps 1f and 1g may be reversed. That is, the circuit pattern 160 may be formed after first etching the lower surface. In this case, when the lower surface is first etched, since the insulating surface 150 and the lead portion 180 surface is exposed at the same time, unlike in FIG. 1G, a circuit pattern may be formed on the lower surface.

However, when the lower surface is etched first, it is more preferable to perform the step of 1g after 1f because the substrate is thinner and it is more difficult to control.

3B is a rear view illustrating a portion where a solder mounting pad of a lead frame according to an embodiment of the present invention is to be mounted. Referring to FIG. 3B, the bottom surface is etched by step 1g to expose the bottom surface of the die pad 115 and the bottom surface of the lead frame.

In addition, the cross-sectional shape after etching is shown in FIG. Referring to FIG. 4, the lead unit 180 may be formed to have the same thickness as the insulation unit 150 as shown on the left side, or may be formed inside the insulation unit 150 as shown on the right side. When the lead unit 180 is formed inside the insulating layer, the die frame may be molded later and the adhesive force may be increased during the soldering process.

After performing this lower surface etching, a process for forming a wire bonding pad (or referred to as an inner lead) and a solder mounting pad (or referred to as an outer lead) is performed, as shown in FIG. 1H. do. More specifically, the photoresist 120 is coated on both surfaces, and the wire bonding pad 190 is exposed and developed by using the mask 130 including the light blocking region S1 and the light transmitting region S2. ) And the location where the solder mounting pad 185 is to be formed.

Thereafter, the exposed portion is plated. The plating treatment here may form gold (Au) plating after nickel (Ni) plating. Further, palladium (Pd) and Au may be sequentially plated on the Ni plating layer. In addition, one or more of Ni, Pd and Au can be replaced with Ag. The plating layer sphere generally proceeds by electroplating, but may also proceed by using electrolytic plating and electroless plating.

Finally, the photorest is removed to form the wire bonding pad 190 and the solder mounting pad 185 as shown in FIG. 1I. An upper surface of the wire bonding pad 190 thus formed is shown in FIG. 3A.

In addition, the thickness of the circuit pattern 160 and the thickness of the wire bonding pad 190 may be adjusted as needed, so that the height of the circuit pattern 160 and the height of the wire bonding pad 190 may be the same or different. have.

As a result, a fine circuit pattern 160 can be formed by a simple process as compared with the conventional BGA (Ball Grid Array) manufacturing method. In addition, unlike the conventional structure in which the lead part performs the role of the circuit pattern 160, the circuit pattern 160 is separately formed by the paste printing method to form a circuit pattern 160 that is more fine, uniform in thickness, and highly integrated. can do.

In the foregoing detailed description of the present invention, specific examples have been described. However, various modifications are possible within the scope of the present invention. The technical spirit of the present invention should not be limited to the above-described embodiments of the present invention, but should be determined by the claims and equivalents thereof.

1A to 1I are cross-sectional views of each step of the lead frame manufacturing method according to an embodiment of the present invention.

2 is a plan view showing a circuit pattern 160 of a lead frame according to an embodiment of the present invention.

3A is a plan view showing a wire bonding pad portion of a lead frame according to one embodiment of the present invention.

3B is a plan view showing a solder paste pad portion of a lead frame according to one embodiment of the present invention.

4 is an enlarged cross-sectional view of a lead portion of a lead frame according to an embodiment of the present invention.

Description of the Related Art [0002]

110: metal substrate 115: die pad portion

120: photoresist 130: photo mask

150: insulation unit 160: circuit pattern

180: lead portion 185: solder mounting pad (outer lead)

190: wire bonding pad (inner lead)

Claims (9)

A die pad part spaced apart from a lead part made of a first metal by an insulating part made of an insulating material; A circuit pattern formed of a second metal on the lead portion and the insulation portion; An inner lead formed on one side edge of the circuit pattern upper surface on one side and the other side of the circuit pattern near the die pad portion; And And an outer lead formed on the lower surface of the lead part. The method of claim 1, The lead frame, characterized in that the thickness of the circuit pattern is constant. The method of claim 1, The lead portion, the lead frame, characterized in that the width of the upper direction is narrower than the width of the lower direction. (a) forming a dielectric part groove, a die pad part, and a lead part by performing half etching on the metal substrate; (b) forming an insulating part by filling an insulating material in the insulating part groove; And (c) forming a circuit pattern by printing a metal paste on the lead portion and the insulation portion to be insulated from the die pad portion; , ≪ / RTI & In step (c), (c1) forming a circuit pattern by printing a metal paste on the lead portion and the insulating portion; And (c2) etching the lower surface of the metal substrate to insulate the die pad portion from the lead portion. delete (a) performing half etching on the metal substrate to form an insulating part groove, a die pad part, and a lead part; (b) forming an insulating part by filling an insulating material in the insulating part groove; And (c) forming a circuit pattern by printing a metal paste on the lead portion and the insulation portion to be insulated from the die pad portion, The step (c) (c1) etching the lower surface of the metal substrate to insulate the die pad portion from the lead portion; And (c2) forming a circuit pattern by printing a metal paste on the lead portion and the insulating portion. The method according to claim 4 or 6, The material of the metal paste of the step (c) is made of at least one of copper (Cu), aluminum (Al), and magnesium (Mg). The method according to claim 4 or 6, The lead frame manufacturing method, (d) forming a wire bonding pad on an upper surface of the circuit pattern or the die pad portion, or forming a solder mounting pad on a lower surface of the lead portion or the die pad portion. The method according to claim 4 or 6, The step (c) is a step of printing a metal paste so that the thickness of the circuit pattern is constant.

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