CN101740539B - Four-square plane non-guide pin package unit and its manufacturing method and its lead frame - Google Patents

Abstract

A quad flat non-leaded package unit comprising: the lead frame comprises a chip seat and a plurality of pins, wherein the chip seat and the plurality of pins are respectively provided with a first surface and an opposite second surface; the active surface of the chip is provided with a plurality of welding pads, and the inactive surface of the chip is connected with the chip seat; a plurality of wires electrically connected to the chip and the pins respectively; the packaging colloid coats the chip, the lead and the lead frame, but the chip seat and the second surfaces of the plurality of pins are exposed; the pins at the outermost periphery of the lead frame are provided with extending parts and opposite concave parts, so that when the packaging unit is subjected to reflow soldering, the concave parts accommodate solder, and the bonding in the horizontal and vertical directions is provided to increase the bonding area, thereby having the advantage of improving the bonding strength of the packaging unit.

Description

Four-square plane non-guide pin package unit and its manufacturing method and its lead frame

technical field

The invention relates to a package unit without pins in a square plane, in particular to a package unit without pins in a square plane with pins that enhance the bonding strength of solder.

Background technique

The quadrilateral planar pinless package unit is a package unit in which the chip base and the bottom surface of the pins are exposed on the bottom surface of the encapsulant. Generally, the surface coupling technology is used to couple the package unit to the printed circuit board, thereby forming a specific function. circuit modules. In the surface coupling process, the die paddle and pins of the quad planar leadless package unit are directly soldered to the printed circuit board.

For example, US Pat. Nos. 6,201,292 and 7,049,177 disclose a conventional quadrilateral planar leadless package unit. The coupling method of the conventional quadrilateral planar leadless package unit to a printed circuit board is described below with reference to FIG. 1 .

The existing quadrilateral planar leadless package unit 100 includes the following components: (a) lead frame 110, which has a chip base 111 and a plurality of pins 113, and the chip base 111 and the plurality of pins 113 respectively have a first surface 120 and the opposite second surface 130; (b) chip 140 has an active surface 150 and an opposite non-active surface 160, with a plurality of solder pads 151 on the active surface 150, wherein the non-active surface 160 of the chip 140 is connected to Placed on the first surface 120 of the chip holder 111; (c) a plurality of wires 170 electrically connected to the pads 151 and the pins 113 respectively, and the wires 170 are bonded to the pins 113 The first surface 120; and (d) encapsulant 180, covering the chip 140, the lead 170 and the lead frame 110, but exposing the second surface 130 of the chip base 111 and the plurality of pins 113 to the outside ; Wherein, the second surface 130 of the die holder 111 and the second surface 130 of the pin 113 present a plane.

The printed circuit board 190 includes a substrate 191 , a ground portion 193 , and a plurality of conductive portions 195 . The grounding part 193 is used as a placement area for the chip holder 111 of the square planar leadless package unit 100, and its area is approximately equal to the area of the chip holder; and the conductive part 195 is used as an electrical connection point on the printed circuit board 190, and its area It is approximately equal to the area of the exposed surface of each pin on the quadrilateral planar leadless package unit.

Next, a solder coating process is performed, so that the solder 197 is coated on the surface of the ground portion 193 and each conductive portion 195 . Afterwards, the surface coupling procedure is performed to place the quadrilateral planar leadless package unit 100 on the printed circuit board 190 , and align each pin 113 and chip holder 111 to the corresponding conductive portion 195 and ground portion 193 respectively.

Finally, a reflow process (solder-reflow process) is carried out, so as to reflow the solder between each pin and the conductive part and between the chip base and the ground part, thus completing the quadrangular planar leadless package unit to the printed circuit board. Circuit board coupling process.

However, during the reflow process, the melted solder will shrink towards the center, so the reflowed solder will slightly bulge upwards, so that the bonding area becomes smaller, and because the second surface of the chip base and the pin The second surfaces are all flat surfaces, and the only planar combination also makes the bonding strength of the solder poor, thus causing the problem of poor reliability.

Therefore, how to solve the above-mentioned problems caused by the poor bonding strength of the existing solders and develop a novel quadrangular planar leadless package unit is an urgent subject to be solved at present.

Contents of the invention

In view of the disadvantages of the above-mentioned background technology, the present invention provides a quadrangular planar leadless package unit with recesses on the bottom surface of the leads, so as to improve the solder bonding strength in the horizontal direction and the vertical direction.

The present invention discloses a quadrangular planar leadless package unit, comprising: (a) a lead frame including a chip seat and a plurality of pins, the chip seat and the plurality of pins respectively have a first surface and an opposite second surface surface; (b) a chip having an active surface and an opposite non-active surface, the active surface has a plurality of pads, wherein the non-active surface of the chip is placed on the first surface of the chip holder; (c) multiple a wire electrically connected to the pad and the pin respectively, and the wire is bonded to the first surface of the pin; and (d) an encapsulant covering the chip, the wire and the wire frame, but the second surface of the chip base and the plurality of pins are exposed; wherein, the first surface of the outermost pins of the lead frame is formed with an extension, and extends away from the first surface , and the opposite second surface is formed with a concave portion, which is used to make the concave portion accommodate solder when the quadrilateral planar leadless package unit is reflowed.

The present invention also discloses a method for manufacturing a quadrilateral planar leadless package unit, including: providing a carrier board, the carrier board includes a plurality of cutting lines defined on the surface of the carrier board, and a plurality of bumps formed on the cutting lines , and the flat portion surrounded by the plurality of bumps; after forming a metal layer on the surface of the carrier with bumps, the metal layer is patterned to obtain a lead frame, and the lead frame has a lead frame formed on the flat portion The first surface and the opposite second surface have a chip seat and a plurality of pins, wherein some of the pins are formed at the bump and cover the bump, and the pins formed at the bump have extensions and the concave portion; then the chip is bonded on the chip holder; then a plurality of wires are formed to electrically connect the chip and the pins; an encapsulant is formed on the carrier board to cover the pins, the chip holder, the chip and the wires ; removing the carrier board to expose the lead frame; and cutting and separating along the cutting line to obtain a plurality of quadrangular planar leadless package units.

The present invention also discloses a lead frame with no guide pins on a square plane, comprising: a chip seat; and a plurality of pins surrounding the chip seat, the chip seat and the plurality of pins respectively have a first surface and an opposite second surface surface; wherein, an extension part is formed on the first surface of the outermost pin of the lead frame, and extends away from the first surface, and a concave part is formed on the opposite second surface to accommodate solder.

The beneficial effects of the present invention will be described below in combination with the above technical solutions. The present invention utilizes the concave portion formed on the second surface of the pin to accommodate the solder when the quadrilateral plane leadless package unit is reflowed, provides bonding in the horizontal and vertical directions, and increases the bonding area , thereby improving the solder bonding strength.

Description of drawings

FIG. 1 is a schematic cross-sectional view of an existing four-square planar package unit without leads;

2A to FIG. 2G are schematic cross-sectional views of the quadrangular planar pinless package unit and its manufacturing method of the present invention;

2A' is a schematic cross-sectional view showing a lead frame formed on a carrier;

2A" is a schematic cross-sectional view showing another lead frame formed on a carrier;

3A is a schematic cross-sectional view of another quadrangular planar leadless package unit of the present invention; and

3B to 3D are schematic diagrams showing the concave portion formed on the second surface of the die holder according to the present invention.

[Description of main component symbols]

100, 200 square planar lead-free package unit

110, 210 lead frame

111, 211 chip holder

113, 213 pins

120, 220 first surface

130, 230 second surface

140, 240 chips

150, 250 active face

151, 251 welding pad

160, 260 non-active surface

170, 270 wire

180, 280 encapsulation colloid

190, 290 printed circuit board

191 Substrate

193, 293 Grounding part

195, 295 Conductive part

197, 297 Solder

212 carrier board

214 Surface

216 Matrix sealing area

218 cutting line

219 matrix unit

221 flat part

223 bump

225 extension

227 concave part

241 Adhesive

Detailed ways

The implementation of the present invention is described below through specific specific examples, and those of ordinary skill in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

first embodiment

Please refer to FIG. 2A to FIG. 2G , which are schematic diagrams of the quadrilateral planar leadless package unit and its manufacturing method of the present invention.

As shown in FIG. 2A , a carrier 212 is provided, and the material of the carrier 212 can be (but not limited to) a metal material such as copper. The surface 214 of the carrier 212 includes a matrix sealing area 216 , and the matrix sealing area 216 defines a plurality of cutting lines 218 and matrix units 219 .

2A', each matrix unit 219 of the carrier 212 has a flat portion 221 and a plurality of bumps 223 are formed on the cutting line 218 and surround the flat portion 221, and the bumps 223 surround the flat portion 221 to obtain The area is approximately equal to the area of a quadrangular plane leadless package unit 200; then, a patterned metal layer is formed on the carrier board 212 using electroplating and patterning techniques, and the metal layer has, for example, gold/palladium/nickel/ A palladium layer or a gold/nickel/copper/palladium layer, and the patterned metal layer is used as a lead frame 210, the lead frame 210 has a chip holder 211 and a plurality of pins 213, wherein the chip holder 211 is formed on the flat portion 221 and the area of the chip seat 211 is approximately equal to the area of the chip; part of the pin 213 is formed between the chip seat 211 and the bump 223 and part of the pin 213 is formed at the bump 223 and covers the bump Block 223 , therefore, relative to the bump, the pin 213 formed at the bump 223 has an extension 225 and a recess 227 .

Or, as shown in FIG. 2A ", the inner side of the cutting line 218 of each matrix unit 219 of the substrate also has a bump 223 surrounding the flat portion 221. Therefore, the area of the flat portion 221 is larger than that shown in FIG. 2A' Small.

Specifically, referring to FIG. 2A', the lead frame 210 disclosed in the present invention includes: a chip holder 211; and a plurality of pins 213 surrounding the chip holder 211; Each pin 213 respectively has a first surface 220 and an opposite second surface 230; wherein, an extension 225 is formed on the first surface 220 of the outermost pin 213 of the lead frame 210, and extends away from the first surface 220. The direction extends, and the opposite second surface 230 is formed with a recess 227 for accommodating solder.

Similarly, as shown in FIG. 2A ″, extensions may be formed on the first surface of all the pins of the lead frame, extending in a direction away from the first surface, and recesses are formed on the opposite second surface. In addition, The second surface of the chip holder of the lead frame may further form a concave portion, which is used for allowing the concave portion to accommodate solder when the quadrilateral planar leadless package unit is reflowed.

As shown in FIG. 2B , a die bonding step is performed to provide a chip 240 with a plurality of bonding pads 251 on the active surface 250 , and the non-active surface 260 of the chip 240 opposite to the active surface 250 is bonded to the chip holder 211 through an adhesive 241 . In the present invention, examples of the adhesive include, but are not limited to, silver paste.

As shown in FIG. 2C , the step of electrically connecting the chip and the pins is performed, and a plurality of wires 270 are formed by way of wire-bonding, and the wires 270 are electrically connected to the pads 251 of the chip 240 and the pins. 213.

As shown in FIG. 2D , an encapsulation step is performed, which forms an encapsulant by means of molding or gluing, and the encapsulant 280 is formed on the carrier 212 to cover the pins 213, the chip holder 211, and the chip 240. and wire 270 .

As shown in FIG. 2E, an etching step such as wet etching is performed to remove the carrier, thereby exposing the bottom surface 261 of the lead frame 210 and the bottom surface 261 of the encapsulant 280, and since the carrier with bumps is removed Board, the pin 213 previously formed at the bump has a recess 227 opposite.

As shown in FIG. 2F , a dicing step is performed next, wherein each matrix unit is diced and separated along the dicing line 218 to obtain the quadrangular planar leadless package unit 200 of the present invention.

Through the foregoing manufacturing method, the present invention also discloses a quadrangular planar leadless package unit 200, comprising: a lead frame 210, including a chip holder 211 and a plurality of pins 213, and the chip holder 211 and the plurality of pins 213 respectively have a first surface 220 and an opposite second surface 230;

The chip 240 has an active surface 250 and an opposite non-active surface 260, and the active surface 250 has a plurality of bonding pads 251, wherein the non-active surface 260 of the chip 240 is connected to the first surface 220 of the chip holder 211 ;

a plurality of wires 270 electrically connecting the pads 251 and the pins 213 respectively, and the wires 270 are bonded to the first surface 220 of the pins 213; and

The encapsulant 280 covers the chip 240, the wires 270 and the lead frame 210, but exposes the second surface 230 of the chip holder 211 and the plurality of pins 213;

Wherein, an extension portion 225 is formed on the first surface 220 of the outermost pin 213 of the lead frame 210 and extends away from the first surface 220, and a concave portion 227 is formed on the opposite second surface 230 for When the quadrilateral planar leadless package unit 200 is reflowed, the concave portion is made to accommodate solder. More specifically, the outermost pin has a stepped structure, and the concave portion of the pin is located on the outer edge of the packaging unit.

In another embodiment of the present invention, extensions are formed on the first surfaces of all the pins and extend in a direction away from the first surfaces, and recesses are formed on the opposite second surfaces.

As shown in FIG. 2G, the soldering and reflow steps are performed in sequence to provide a printed circuit board 290, which has a predetermined ground portion 293 and a conductive portion 295, so that solder 297 is coated on the ground portion 293 and on the surface of each conductive portion 295, and then place the quadrilateral planar leadless package unit 200 on the printed circuit board 290, and align each pin 213 and chip holder 211 to the corresponding conductive portion 295 and ground portion 293 respectively .

Finally, carry out a reflow process (solder-reflow process), whereby the solder 297 is reflowed between each pin 213 and the conductive part 295 and between the chip holder 211 and the ground part 293, thus completing the four sides of the present invention The coupling process of the planar leadless package unit 200 to the printed circuit board 290. In addition, since the pins with the concave portion of the quadrangular planar leadless package unit of the present invention are located on the cutting line, after reflow, the solder can The pins on the sides of the packaging unit are covered to provide better bonding strength.

Therefore, the pins of the quadrilateral planar leadless package unit of the present invention have recesses to accommodate solder, thereby improving the bonding strength in the horizontal and vertical directions; moreover, an extension is formed on the first surface of the pins, and Extending away from the first surface, the pins of the present invention provide more areas for bonding with the encapsulant, and also enhance the bonding strength between the pins and the encapsulant.

second embodiment

Please refer to FIG. 3A to FIG. 3D , which are schematic diagrams of a second embodiment of the quadrangular planar leadless package unit of the present invention. At the same time, in order to simplify the figure, in this embodiment, the same or similar components as described above are represented by the same reference numerals.

The quadrangular plane leadless package unit and its manufacturing method of the present embodiment are substantially the same as those of the foregoing embodiments, the main difference being that a recess is formed on the second surface of the chip base for returning to the square planar leadless package unit. When soldering, the recess is made to accommodate solder. The method for forming the concave portion on the second surface of the chip holder may optionally form a concave portion on the second surface of the chip holder after removing the carrier board.

As shown in FIG. 3A , the concave portion 227 of the die holder 211 is formed at the center of the second surface 230 of the die holder 211 .

In addition, as shown in FIG. 3B and FIG. 3C , the concave portion 227 at the central position is rectangular or the concave portion 227 at the central position is circular.

As shown in FIG. 3D , the concave portion 227 of the die holder 211 can also be formed at the peripheral position of the second surface 230 of the die holder 211 .

On the other hand, it can be seen from FIG. 3A to FIG. 3D that the concave part of the chip holder included in the leadframe with no guide pin in the square plane of the present invention can be formed at the central position of the second surface of the chip holder, and the shape of the concave part has no difference. Particularly restrictive, the recess in this central position can therefore be rectangular or circular. In addition, the concave portion of the chip holder can also be formed on the peripheral position of the second surface of the chip holder.

The quadrilateral planar leadless package unit of the present invention provides bonding in horizontal and vertical directions by using the recess formed on the second surface of the pin to accommodate solder when the quadrilateral planar leadless package unit is reflowed, And increase the bonding area. In addition, since the pins located on the outer edge of the package unit form a stepped structure inward, the solder can cover the pins on the outer edge during reflow, which can further improve the bonding strength of the package unit. .

The specific embodiments described above are only used to illustrate the characteristics and effects of the present invention, rather than to limit the scope of the present invention. Without departing from the spirit and technical scope of the present invention, any application of the present invention Equivalent changes and modifications accomplished through the disclosed content should still fall within the scope of the appended claims.

Claims (16)

1. A four-square planar package unit without guide pins, comprising: a lead frame comprising a die pad and a plurality of pins, the die pad and the plurality of pins respectively having a first surface and an opposite second surface; A chip has an active surface and an opposite non-active surface, the active surface has a plurality of pads, wherein the non-active surface of the chip is placed on the first surface of the chip holder; a plurality of wires electrically connected to the pads and the pins respectively, and the wires are bonded to the first surface of the pins; and an encapsulant covering the chip, the wires and the lead frame, but exposing the second surface of the chip holder and the plurality of pins; It is characterized in that an extension part is formed on the first surface of the outermost pin of the lead frame, and extends away from the first surface, and a concave part is formed on the opposite second surface, so that there is no guide on the square plane. When the foot package unit is reflowed, the recess is made to accommodate solder. 2 . The quadrilateral planar leadless package unit according to claim 1 , wherein the outermost pin has a stepped structure, and the concave portion of the pin is located at the outer edge of the package unit. 3 . 3. The quadrilateral planar leadless package unit according to claim 1, wherein all the pins are formed with extensions on the first surface, and extend in a direction away from the first surface, and the opposite second Concaves are formed on the two surfaces. 4. The quadrilateral planar leadless package unit according to claim 1, wherein the second surface of the chip holder is further formed with a concave portion for reflowing the quadrilateral planar leadless package unit. The recess formed by the second surface of the die paddle accommodates solder. 5 . The quadrilateral planar leadless package unit according to claim 4 , wherein the concave portion of the die holder is formed at the center of the second surface of the die holder. 5 . 6 . The quadrilateral planar leadless package unit according to claim 4 , wherein the concave portion of the die holder is formed at a peripheral position of the second surface of the die holder. 7 . 7. A lead frame with no guide pins on a square plane, comprising: chip holder; and a plurality of pins surrounding the die paddle, the die paddle and the plurality of pins respectively have a first surface and an opposite second surface; It is characterized in that an extension portion is formed on the first surface of the outermost pin of the lead frame, and extends in a direction away from the first surface, and a concave portion is formed on the opposite second surface for reflow soldering. This recess is made to accommodate solder. 8 . The quadrilateral flat lead frame without leads according to claim 7 , wherein the outermost pins have a stepped structure, and the recesses of the pins are located on the outer edge of the packaging unit. 9 . 9. The lead frame with no guide pins on a square plane according to claim 7, characterized in that, all the first surfaces of the pins are formed with extensions, which extend in a direction away from the first surface, and are opposite to each other. A recess is formed on the second surface. 10. The lead frame without leads in a square plane according to claim 7, wherein a concave portion is formed on the second surface of the chip base for reflowing the package unit without leads in a square plane, The recess formed by the second surface of the die paddle receives solder. 11 . The quadrilateral flat lead frame without guide pins according to claim 10 , wherein the concave portion of the die holder is formed at the center of the second surface of the die holder. 12 . 12 . The lead frame without lead pins in a square plane as claimed in claim 10 , wherein the concave portion of the chip pad is formed at a peripheral position of the second surface of the chip pad. 13 . 13. A method for manufacturing a four-square planar package unit without guide pins, comprising the following steps: A carrier is provided, the carrier includes a plurality of cutting lines defined on the surface of the carrier, a plurality of bumps formed on the cutting lines, and a flat portion surrounded by the plurality of bumps; After forming a metal layer on the surface of the carrier with bumps, the metal layer is patterned to obtain a lead frame having a chip pad having a first surface and an opposite second surface formed on the flat portion and a plurality of pins, wherein some of the pins are formed at the bump and cover the bump, and the pins formed at the bump have extensions and recesses; bonding a chip to the chip holder; forming a plurality of wires to electrically connect the chip and pins; Forming an encapsulant on the carrier board to cover the pins, chip holders, chips and wires; removing the carrier plate to expose the lead frame; and Cutting and separating along the cutting line to obtain a plurality of quadrangular planar leadless package units. 14 . The method for manufacturing the quadrilateral planar leadless package unit according to claim 13 , further comprising bonding the chip base and the pins of the matrix unit to a printed circuit board by solder. 14 . 15 . The manufacturing method of the quadrilateral planar leadless package unit according to claim 13 , further comprising forming a concave portion on the second surface of the die pad after removing the carrier board. 16 . 16 . The manufacturing method of the quadrilateral planar leadless package unit according to claim 15 , wherein the concave portion of the die holder is formed at a peripheral position of the second surface of the die holder. 17 .

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