Plastic integrated circuit device package and micro-leadframe and method for making the package

Plastic integrated circuit element packaging body, miniature lead frame and method for manufacturing the packaging body

<u>Field of invention</u>

The present invention is directed to an improved plastic package of integrated circuit die, and a method and lead frame for manufacturing the package.

<u>Background of the invention</u>

The conventional integrated circuit die is encapsulated in a plastic package, which provides protection from harmful environments and serves as an electrical interconnection between the integrated circuit die and the printed circuit board. This type of package component includes a metal lead frame, an integrated circuit die, a bonding material attaching the integrated circuit die to the lead frame, wiring which electrically connects the pad of the integrated circuit die to each lead of the lead frame, and a hard plastic package The encapsulant material covers part of the components and forms the outside of the package body.

The lead frame is the central support structure of the package. Part of the lead frame is located inside the package, in other words, it is completely surrounded by the plastic encapsulant. The leads of a part of the lead frame are extended from the package body for external connection to the package body.

Further background information about conventional plastic integrated circuit packages and lead frames is contained in Chapter 8 of the Microelectronics Encapsulation Handbook (1989), edited by R. Tummala and E. Rymaszewski, published by Van Nostrand Reinhold, New York, New York No. 5 114 Street.

The problem of the conventional plastic package is that the internal lead frame limits the shrinkage of the package size. Practitioners try to reduce the size of the package by removing the inner lead frame, as shown in US Patent No. 4,530,142 by Roche et al. and US Patent No. 5,172,213 by Casto, but this type of package has numerous disadvantages. In the '142 patent, Roche et al. showed that the contacts of the package have orthogonal sides. In this way, since the contacts are easily pulled by the encapsulant material, the package body becomes unreliable. The package shown by Casto in the '213 patent has bent leads, which extend vertically from the top of the die pad to the top of the die. Including such leads in the package will increase the manufacturing cost and limit the reduction in the lateral size of the package. This requires a smaller and more reliable plastic package.

<u>Summary of the invention</u>

The present invention is directed to an improved plastic package for covering an integrated circuit die, and a lead frame and method for manufacturing the package. In the specific example of the package assembly method of the present invention, step 1 provides a metal lead frame. The lead frame includes a disposable rectangular frame. The die pad is located inside the frame and connected with the frame. The plurality of leads extend from the frame lateral to the die pad without touching the die pad.

The die pad of the lead frame has a rectangular periphery. The die pad has a horizontal first surface on which the die is arranged during the assembly of the package. The opposite surface of the first surface is a substantially flat central second surface and a substantially flat peripheral third surface. The third surface is located at the periphery of the second surface, and is vertically recessed from the second surface, so there is a stepping profile on the lower surface of the die pad. In the completed package, the encapsulant material fills the bottom of the recessed third surface of the die pad, but does not cover the second surface of the die pad. The encapsulant material under the third surface of the die pad can prevent the die pad from being vertically pulled by the package body.

Each lead has a first surface, a second surface opposite to the first surface, and a third surface. The third surface is also opposite to the first surface and adjacent to the second surface. The second side has a rectangular or circular periphery. The third surface is vertically recessed from the second surface, resulting in a bottom surface of the lead with step-by-step skimming. In the completed package, the encapsulant material fills under the third surface of the lead, but does not cover the second surface of the lead. The second side of the lead is used as a connection point for connecting the package body from the outside, like an LCC package body, or as a land block for connecting solder beads. The encapsulant material under the third surface of the lead can prevent the lead from being pulled vertically by the package body.

The lead frame is formed from rolled metal strips by a two-step wet etching method. The first etching step is single- or double-sided etching, which etches through the metal strip and transfers the predetermined overall pattern of the lead frame to the metal strip. The second etching step is single-sided etching, etching the periphery of a die pad and selected parts of the leads. The second etching step partially etches through the thickness of the die pad and the lead, thereby forming the aforementioned vertical recessed flat or substantially flat third surface on the die pad and the lead.

Step 2 Set an integrated circuit on the first upper surface of the die pad. Depending on the application, the area of the die may be smaller than the area of the first side of the die pad, or it may have a larger area such that the die is suspended next to the die pad. In these cases, the die is also suspended by part of the lead length.

Step 3 Electrically connect the wiring or equivalent conductor between the wiring pad of the die and the first surface of the lead. The lead part of the wire connection may be plated with silver, gold or other metals, for example.

Step 4 Apply a viscous adhesive encapsulant material to the upper first surface of the die and the lead frame. Then the encapsulant material hardens. The encapsulant material covers the die, the wiring, the first side of the lead, the die and the third side of the lead, and the side surfaces of the die and the lead. The second surface of the die and the lead is not covered by the encapsulant material, but is exposed on the lower surface of the outer side of the package body.

Step 5: Use metal to plate the exposed surface of the lead frame, including the die pad and the exposed second surface of the lead, such as copper, gold, lead-tin alloy, tin, nickel, bar or any solderable metal. Depending on the application and the material used to make the die pad, step S can be deleted.

Step 6: The completed package body is cut by the encapsulated lead frame. Special step 6: Eliminate the disposable parts of the lead frame and/or cut the disposable parts of the lead frame, such as rectangular frame, by the non-disposable components of the lead frame, such as die pads and leads, depending on the encapsulation method used in step 4. Step 6 also cut off the encapsulant material to form the peripheral side of the package.

Step 6: Cut the leads by the lead frame. The cutting is carried out on the inside of the weir rod. Depending on the cutting position, the cut lead end may extend laterally beyond the side of the package body. Step 6 or subsequent steps also include bending the protruding end of the cut lead over the side of the package body, so that the lead end has an oblique angle with respect to the lower surface of the outer side of the package body and the remaining part of the lead enclosed. When the package is soldered to the printed circuit board, the solder can be connected to the upwardly bent end of the cut lead. In addition, it is connected to the horizontal part of the lead exposed on the lower surface of the outer side of the package to enhance the solder connection. The lower surface of the outer side of the package includes: the second surface of the die pad is located in the center of the bottom surface of the package; the second surface of the lead and the hardened encapsulant material form the rest of the bottom surface of the package and isolate the die pad and the lead .

The package of the present invention has countless advantages and can be used for countless applications including power devices and analog devices. The size of the package body can be made small. For example, the package body can be close to the size of a chip. In addition, the package body can be extremely thin. According to the present invention, a package with a thickness as small as about 0.5 mm or less can be manufactured. In addition, the lead wires can be placed close to the die, shortening the wiring length. The exposed surface of the die pad can be connected to the printed circuit board by a metal sturdy material to cool the package body.

Various changes of the aforementioned lead frame, package body and assembly method are described in this speed, and also constitute a part of the present invention. For example, in an alternative assembly method, a lead frame is provided which allows multiple packages to be formed at the same time.

<u>Detailed description</u>

Figure 1 is a flow chart of the method according to the present invention for assembling an integrated circuit component package. Fig. 5 shows a specific example of the package according to the present invention, which can be formed by the method of Fig. 1.

Step 1 of Figure 1 provides a metal lead frame. Figure 2 is a plan view of a lead frame 20 according to the present invention. For easy inspection, Figure 2 (and other figures) uses leads to distinguish between the metal part of the lead frame 20 and the blank space between the metal part of the lead frame 20.

The lead frame 20 in Figure 2 is made of a conventional lead frame metal, such as copper or copper alloy, copper plated, steel alloy plated, alloy 37 (37% nickel, 55% iron) or copper plated steel depending on its use .

The lead frame 20 in FIG. 2 includes a peripheral rectangular tie rod 21 and a central rectangular weir 29 (the industry understands that the term "rectangular" or "rectangular" includes a square, which is a rectangle with four equal sides). In alternative specific examples (not shown in the figure), for example, in the case where a plurality of lead frames 20 are etched on a metal strip (for example, Fig. 16), the tie rod 21 can be deleted, and the periphery of the lead frame can be interposed between adjacent lead frames. The metal strip is partially formed. In another alternative specific example (not shown in the figure), the tie rod 21 and the lead part between the tie rod 21 and the weir rod 29 can be deleted, so the outer frame of the lead frame is the weir rod 29.

The die pad 22 with a rectangular periphery is connected to the lead frame 21. The die pad 22 is tied to the inner side of the weir 29. The two connecting ports 28 connect the die pad 22 to the weir 29 and the tie stalk 21 of the lead frame 20. In step 6 of Figure 1, the connection port 2$ is cut off by the lead frame 20 inside the weir 29.

The eight leads 30 are connected to the tie rods and extend laterally outward from the tie rods 21 through the weir rods 29 toward the side of the die pad 22 without contacting the die pad 22. The first end 34 of each lead 30 is adjacent to the die pad 22. In step 6 of Figure 1, each lead 30 is cut between the weir 29 and the first end 34 of the lead 30. In an alternative specific example (not shown in the figure), the lead 30 starts from the weir 29 instead of the tie rod 21, and the tie rod 21 of the weir 29 can be tied by a plurality of symmetrically arranged long strips.

The numbers, positions and lateral paths of the leads 30 of the lead frame 20 shown in Figure 2 are for illustrative purposes only. The number, position and lateral path of the leads can be changed with the application. The advantage of the present invention is that the leads can be designed to match the number and position of the wiring pads of the special integrated circuit die.

In Figure 2, fourteen of the eighteen leads 30 are straight. The four leads 30 include a lateral bend between the weir 29 and the die pad 22. Each straight lead 30 includes an anchorage lug 36 which protrudes vertically from the lateral side of the lead 30. The bowl-fastening ears 36 are approximately rectangular and are interlaced with adjacent leads 30. In the completed package, the anchor ear 36 is bonded to the encapsulant material of the package and prevents the lead 30 from being pulled horizontally by the package. In addition, the through hole or the recess of the lead 30 can be used to replace the anchor ear to join the encapsulant material.

Fig. 3 is a cross-sectional side view of the lead frame 20 along the line 3-3 of Fig. 2 on the inner side of the parallel member of the weir 29. The die pad 22 and the two opposite leads 30 are shown in a side view. The part of the lead 30 shown starts from the inside of the weir 29 immediately. The lower surface of the die pad 22 and the lead 30 includes a vertical recess, a horizontal or a substantially horizontal plane

The die pad 22 in FIG. 3 has a substantially flat or flat upper first surface 23, an opposite substantially flat or flat second surface 24, and an opposite substantially flat or flat third surface 25. The orthogonal first side surface 26 is between the first surface 23 and the third surface 25, and the orthogonal second side surface 27 is between the third surface 25 and the second surface 24. The third surface 25 is vertically recessed from the second surface 24 by a distance "H1". In other words, the third surface 25 is vertically interposed between the first surface 23 and the second surface 24. The middle of the die pad 22 has a height "H" between the first surface 23 and the second surface 24. The third surface 24 of the die pad 22 is on the periphery of the second surface 24, and in a specific example, it surrounds the second surface 24.

Each lead 30 in FIG. 3 includes a flat or substantially flat first surface 31. On the opposite side of the first surface 31 are a flat or substantially flat second surface 32 and a flat or substantially flat third surface 33. The second surface 32 starts from the weir 29 and extends a distance from the inner side of the weir 29 toward the die pad 22. In this specific example, the second surface 32 has a rectangular periphery. The length of the second surface 32 varies with the application, but it needs to have a sufficient size for external connection of the package. The third surface 33 extends between the second surface 32 and the terminal 34 of the lead 30 adjacent to the die pad 22. The third surface 33 is vertically recessed from the second surface 32 by a distance "H". In other words, the third surface 33 is vertically interposed between the first surface 31 and the second surface 32. The bowl attachment ear 36 (not shown in the figure) extends vertically from the side 37 of the lead 30 adjacent to the third surface 33.

In step 6 of the first figure, after the lead frame 20 is encapsulated, the lead 30 is drawn from the inner side of the weir 29 along the lines A--A, B--B, C--C, and D--D in the second figure Cut off. The cutting system vertically penetrates the portion including the second surface 32 of the lead 30. In the completed package, the second surface 32 of each cut lead 30 serves as the package contact to directly or indirectly electrically connect the package to the external printed circuit board. In the completed package, the third surface 33 of the lead 30 is covered with an encapsulant material, so that it is located inside the package body (Fig. 5).

The example value of the height "H" of the die pad 22 and the lead 30 of the lead frame 20 in FIG. 3 includes about 0.15 to 0.50 mm, and the value of "H1" includes about 0.075 to 0.25 mm. Example values of the horizontal recess "W" of the die pad 22 include about 0.025 to 0.25 mm. (These values are also applicable to other graphs, where "H", "H1" and "W" are displayed). Expressed as a percentage, the "H1" value is the "H" value, that is, the distance between the first surface 23 and 31 and the second surface 24 and 32 is about 50% or 33% to 75%. Of course, these values are for illustrative purposes only, and the actual value depends on the purpose.

The lead frame 20 in FIG. 2 is made of rolled strip metal stock by wet chemical etching. As is well known, chemical etching (also known as chemical development) is a method of etching patterns into metal strips using lithography, photoresist, and metal-dissolving liquid chemicals. A typical layer of photoresist is applied to one or two flat surfaces of the strip. Secondly, the resist layer is exposed through a resist mask with a predetermined pattern. Then the photoresist is developed and fixed to form a patterned photoresist mask. Secondly, the chemical is sprayed or otherwise applied to one or two flat surfaces of the single-covered strip. The exposed part of the strip is removed by etching, leaving a predetermined pattern on the metal strip.

The two-step etching method is used to form the lead frame 20 of FIGS. 2 and 3 (and FIGS. 9, 13, 15 and 16). The first etching step is to etch one or two flat surfaces of the strip according to the resist pattern applied to one or two flat surfaces of the strip. This first etching step completely etches through the metal strips to form the overall pattern portion of the lead frame, as illustrated in FIG. 2. Next, a second resist pattern is formed on one side of the lead frame. The peripheral portion of the die pad and selected portions of the leads are not covered by the second resist pattern, so they are susceptible to further etching. The second etching step partially etches through the lead frame from one side according to the second resist pattern. This second etching step forms the recessed surface of the lead frame 20 in FIGS. 2 and 3, such as the third surface 5 of the die pad 22 and the third surface 33 of the lead 30 on the inner side of the weir 29. Inside the weir 29, the connection port 28 typically also receives this second etching step. When the chemical etches through the die pad and the selected part of the lead by a predetermined distance, the second etching step is terminated. In other words, the second etching step partially etches through the thickness of the selected portion of the die pad and the lead frame. Therefore, the amount of etching in the second etching step is determined according to demand, and a sufficient amount of encapsulant material is required because the third surface 25 of die pad 22 and the third surface 33 of the lead 30 are under the third surface 33 to firmly fix the die pad 22 and the lead 30. The package body. The typical second etching step removes about 50% of the thickness of the die pad and the lead, but the removal amount can account for about 33% to 75% of the thickness of the die pad and the lead. Due to the imperfect etching process, the third surfaces 25 and 33 may not be flat, but not substantially flat. The etched sidewalls of the die pad 22 and the lead 30 may have a radiused corner instead of being at a 90 degree angle.

In addition, the lead frame 20 can be formed by the first step of progressive stamping to form the overall pattern of the lead frame, and the second step of chemical etching partially etches through the die pad and lead thickness (as described above) of the stamped lead frame to form the lead frame 20 Concave.

Step 2 in FIG. 1 places the integrated circuit die 52 in the center of the first surface 23 of the die pad 22 (FIG. 5 ). The placement and attachment of the die 52 to the die pad 22 can be performed using a conventional die attaching machine and a conventional die attaching atmospheric resin. During step 2 and the subsequent assembly steps, the lead frame 20 of Figure 2 is grounded to protect it from electrostatic discharge ("ESD").

Step 3 in FIG. 1 electrically connects conductive metal wiring 54 or the equivalent between each wiring pad 53 (FIG. 5) of the integrated circuit die 52 and the first surface 31 of each lead 30. The first surface 31 may be plated with gold, silver, nickel, palladium, copper or other metals. During this wiring step, the lead frame 20 in Figure 2 is grounded to prevent damage to the integrated circuit components due to electrostatic discharge.

In step 4 of Figure 1, the viscous adhesive encapsulant material is applied to the lead frame 20 of Figure 2. The encapsulant material covers the integrated circuit die 52, the wiring 54, the side faces 26 and 27 of the die pad 22, the first face 23 and the third face 25 of the die pad 22, and the first face 31 and the first face of the lead 30 Two sides 33 and side (Figures 4 and 5). The second surface 24 of the die pad 22 and the second surface 32 of the lead 30 are not covered with the encapsulant material, in other words remain exposed. In an alternative embodiment, the die pad 22 may be disturbed during the encapsulation step, so a thin layer of encapsulant material is formed under the second surface 24 of the die pad 22. In this specific example, the die pad 22 is entirely located inside the package body. Finally, the encapsulant material hardens.

Depending on the application, there are several ways to complete step 4 in Figure 1. For example, step 4 in Figure 1 can be completed using conventional plastic molding techniques. In this method, the lead frame 20 of FIG. 2 is placed in a mold, and a section of solid molding encapsulant material is formed above and on the lead frame 20, as shown in FIG. 4. The encapsulant material may be a conventional plastic molding compound applied using conventional techniques. Exemplary molding compounds include NITTO MP-8000AN molding compound from Nitto, Japan, and EME 7351 UT molding compound from Sumitomo, Japan. The conventional gate can be formed on the lead frame 20 to assist the molding process. The side of the mold can be pushed and pulled to assist the mold release.

In addition, instead of using the molding process of step 4, step 4 can be completed using a liquid encapsulant. For example, as the first step, the lead frame 20 in Figure 2 is placed on a horizontal surface. As for the second step, the fusion beads of conventional hardenable viscous adhesive materials such as HYSOL 4451 epoxy resin from Dexter-Hysol Company, California Industrial City are applied to the lead frame 20 to form a closed rectangular weir surround The die 52 and the lead 30 at least partly inside the weir 29. As for the third step, the beads are cured, for example, heated at 140°C for 1 hour to cure. As for the fourth step, the conventional hardenable viscous adhesive material applied to the encapsulation body, such as HYSOL 4450 liquid encapsulant, is applied to the inside of the beads, so the unfinished encapsulation body inside the weir is covered with the encapsulant material. As for the final step, the encapsulant material is cured, for example, by heating at 140° C. for 1 hour to form a single solid segment of encapsulant material above and above the lead frame 20. When this method is used in step 4, step 6 uses sawing through the encapsulant material to form the side edges of the orthogonal encapsulation body and the completed package body cut by the lead frame. The similar molding method and the subsequent sawing step of cutting the lead frame from the package are described in US Patent Application No. 09/103,760, dated June 24, 1998, and are described here for reference.

In step 5 of Figure 1, the portion of the lead frame 20 in Figure 2 that is not covered with an encapsulant material includes the second side 24 of the die pad 22 and the second side 32 of the lead 30 using a conventional printed circuit board compatible Known plating metal plating. Examples of plated metals include gold, nickel palladium, inconel, lead tin solder or tantalum, depending on the application. If the metal used to form the lead frame 20 does not need to be plated or has been plated in advance, step 5 can be deleted. For example, if the metal strip used to manufacture the lead frame 20 is copper plated with nickel, step 5 can be deleted.

FIG. 4 is a perspective view of the lead frame 20 of FIG. 2 after completing steps 1-5 of FIG. 1. In this example, the molding process is used in step 4a to harden the encapsulant material block to form the package body 51. The pushing side 55 of the package body 51 is tied to the inside of the weir 29, so that the exposed part of the lead 30 extends between the side of the package body 51 and the weir 29.

Step 6 of Fig. 1 Cut the encapsulated lead frame 20 along the lines A--A, B--B, C--C, and D--D of Fig. 2 (Fig. 4). Refer to No. 281, No. 6 Figure cuts off the inner lead 30 of the weir 29. The cutting is performed through the second side 32 of the lead 30 (FIG. 31). Step 2 also cuts the connector 30 inside the weir rod 29. Finally, step 6 completes the formation of the package by cutting the completed package from the disposable part of the lead frame 20.

Step 6 can be performed using a punch, saw or equivalent cutting device. For example, a punch or a saw can be used when the package body 35 is molded, as shown in FIG. 5. When a punch is used, the completed package can be cut off by the lead frame 20 in a single punching operation. The package body is turned upside down, and the punch cuts the lead 30 inside the weir 29. The cutting position can be changed, so the cut lead extends from the side 55 of the package body to a length ranging from zero to, for example, 0.50 mm.

Figure 5 is a cross-sectional side view of the completed package 50 according to the present invention. The package body 50 is made by the lead frame 20 shown in FIG. 2 and punched through in FIG. 4. The package body 51 of the package body 50 is molded. The package body 50 has a flat or substantially flat outer side lower surface 52 and a side surface 55 that is pushed out.

Consistent with the structure of the package 50 obtained from the lead frame 20 in FIG. 2, the die pad 22 of the package 50 in FIG. 5 includes a flat or substantially flat first upper surface 23. The opposite surfaces of the first surface 23 of the die pad 22 are a flat or substantially flat second surface 24 and a flat or substantially flat peripheral third surface 25. The third surface 25 surrounds the second surface 22 and is vertically recessed by a distance "H1" from the second surface 22. The third surface 25 is interposed between the first surface 23 and the second surface 24 in the vertical direction, and covers an encapsulant material forming the package body 51. The encapsulant material under the first surface 23 can prevent the die pad 22 from being pulled apart vertically by the encapsulant. The second surface 22 is exposed to the lower surface 56 of the package body 50, and thus constitutes a portion of the second lower surface 56 of the package body 50. In an alternative specific example, the die pad 22 is entirely located inside the package body 51.

In FIG. 5, the integrated circuit die 52 is located and attached to the first side 23 of the die pad 22. The wiring 54 is connected between each wiring pad 53 of the die 52 and the first surface 31 of the lead 30.

The package 50 in FIG. 5 includes a plurality of leads, each of which penetrates the second surface 32 at a point inside the weir 29 and is cut by the lead frame 20 in FIG. 2. Depending on the design of the lead frame used to manufacture the package and the application, the arrangement and number of the leads 30 to be cut change. For example, as shown in Figure 2, the lead 30 has a straight and curved lateral path.

As in FIG. 2, each cut lead 30 includes a flat or substantially flat first surface 31, a relatively flat or substantially flat second surface 32, and a relatively flat or substantially flat third surface 33. The third surface 33 is vertically recessed by a distance "H1" from the second surface 32, so the encapsulant material covers the third surface 33. In other words, the third surface 33 is vertically interposed between the first surface 31 and the second surface 32. The second surface 32 of the lead 30 is not covered by the encapsulant material, but is exposed on the lower surface 56 of the package body 50 instead.

In FIG. 5, the first surface 31 of the lead 30 in the internal part of the package body 51 is at the same level as the first surface 23 of the die pad 22, and the third surface 33 of the lead 30 is on the third surface of the die pad 22 The same level of 25. In an alternative specific example (not shown in the figure), where the die pad 22 is disturbed in the mold, the first side 31 of the lead 30 located inside the package body 51 is connected to the first side 23 of the die pad 22 that is disturbed. Lower water level.

Each cut lead 30 in Fig. 5 includes a cut end 35 extending laterally beyond the package side 55, and the remaining part relative to the level of the second surface 32 of the lead 30 and the lower package surface 56 at an oblique angle θ The corners are bent upwards. The angle θ is about 15 to 70 degrees, but the angle can be changed. As shown, the upwardly bent end of the second side 32 of the lead 30 is exposed. The exemplary extent of the bent end 35 of the lead 30 is approximately 0.15 mm beyond the package body side 55, but this length varies with the application. The length of the end 35 of the cut lead 30 is in the range of 0 to 0.50 mm.

The cut end 35 of the lead 30 in FIG. 5 can be bent upward during step 6 by a punching machine used to punch the lead frame 20 through the package body 50. In an alternative specific example (not shown in the figure), the end 35 of the lead 30 can be bent upward, so it contacts the package body side 55, that is, the angle 0 is equal to the horizontal angle between the push and pull package body side 55. In yet another alternative specific example (not shown in the figure), step 6 in FIG. 1 may be to cut the lead 30 on the package side 55, so the cut end of the lead 30 is located laterally extending beyond the package side 55.

In an alternative specific example (not shown in the figure), the cut end 35 of the lead 30 extends laterally beyond the package body side 55 in the horizontal plane. In other words, the cut end 35 is not bent as shown in Fig. 5, but extends laterally on the same horizontal plane as the rest of the lead 30, so the angle θ is equal to zero degrees. When the saw is used in step 6, the package can be obtained. If necessary, when the saw is used in step 6, in addition to the separate bending step, the end 35 can be bent upward to achieve the configuration shown in Figure 5.

In Fig. 6, solder bumps 57 are attached between the package body 50 and the printed circuit board (not shown in the figure). The solder bump 57 contacts the second surface 32 of the lead 30 and also covers the bent end 35 of the lead 30.

Alternatively, in a specific example (not shown in the figure), the exposed second surface 24 of the die pad 22 can be used as a conductive connection, for example, connected to a printed circuit board by a hard material paste to assist the cooling of the package. Cooling is achieved by heat transfer.

FIG. 7 shows the lower surface 56 of the outer side of the package 50 of FIG. 5. The second side 56 of the package body 50 is made of the second side 24 of the die pad 22, the second side 32 of the split lead 30, and a hardened encapsulant material. The second surface 36 of the lead 30 has a rectangular periphery. The cut end 35 of the lead 30 extends slightly beyond the edge of the lower surface 56. Different sizes and shapes of the second surface 32, such as a round shape, are also possible depending on the coating used. The second bucket surface 24 of the die pad 22 also has a rectangular periphery, but other shapes are also possible.

In FIG. 7, the second surface 32 of the lead 30 is aligned in a row along the edge of the lower surface 56 of the package body 50. The cut end 35 of the lead 30 extends slightly beyond the edge of the lower surface 56. Fig. 8 shows an alternative lower surface 61 of the outer side of the package body 60, which is also within the scope of the present invention. In FIG. 8, the rectangular second surface 64 exposed by the cut lead 63 in FIG. 9 is aligned in a single row, and is located at a short distance inward from the edge of the lower surface 61 of the package body 60. For example, the 64-bit second surface is about 0.05 to 0.50 mm away from the periphery of the lower surface 61 of the package body 60, but the distance varies depending on the application. In an alternative specific example (not shown in the figure), the second surface 64 has a circular rather than a rectangular periphery, and forms a solder interconnect bead land.

Figure 9 is a cross-sectional view of the die pad 22 and the leads 63 of the lead frame 62 taken inside the weir bar 29, which are used to make the package 60 of Figure 8. The lead frame 62 of Figure 9 is roughly the same as that of Figures 2 and 3 The lead frame 20 is manufactured in the same manner, except for the arrangement "number and location of the bottom surface of the vertical recess of the lead 63. The repeated description is thus deleted."

Similar to the lead 30 in FIG. 2, the lead 63 in FIG. 9 includes a flat or substantially flat first surface 31 and an opposite flat or substantially flat second surface 64.

The second surface 64 serves as the external contact of the package, unlike the second surface 32 of the lead frame 20 in Fig. 3 and Fig. 9, the second surface 64 of the lead 63 in Fig. 9 is not immediately adjacent and adjacent to the weir 29 (No. 230 ), on the contrary, the position is closer to the die pad 24 between the third surface 66 and the fourth surface 65 of the lead 63. The third surface 66 and the fourth surface 65 are flat or substantially flat relative to the first surface 31, and are on the same plane, and are vertically recessed from the second surface 64 of the lead 63 by a distance "H1" (that is, between Between the second surface 31 and the second surface 64). The fourth surface 65 is interposed between the weir 29 (not shown in the figure but similar to FIG. 2) and the second surface 64 in the lateral direction, and the third surface 66 is interposed between the second surface 64 and the die pad 22.

The periphery of the second surface 64 of the lead 63 in FIGS. 8 and 9 can have various shapes to assist different external connections of the package. For example, as in FIG. 8, the second surface 64 has a rectangular periphery. In addition, the second face 64 may have a circular periphery.

Fig. 10 is a cross-sectional side view of the package 60 of Fig. 8. The package system of Fig. 10 is manufactured according to the method of Fig. 1 using the lead frame of Fig. 9. As shown, the fourth surface 65 is adjacent to the side 57 of the package body, and the second surface 64 is located at a selected distance inside the periphery of the lower surface 61 of the package body 60.

In Figures 8 and 10, the encapsulant material forming the body of the package covers all the leads 63 except for the second side 64. In other words, the third surface 66 and the fourth surface 65 of the lead 63 are covered by the encapsulant material, so that they are located inside the package. In an alternative specific example, the cut end of the lead extends beyond the side of the package body (for example, FIG. 5), and the encapsulant material does not cover the part of the cut lead that extends beyond the side of the package body.

FIG. 11 is a cross-sectional side view of an alternative package 70 according to the present invention, which can be manufactured by the method of FIG. 1. Figure 11 is taken along the line 11-11 of Figure 12. The die 52 is attached to the first upper surface 82 of the die pad 72 by using the conventional atmospheric resin die attaching material 87. The die 52 extends beyond the periphery of the die pad 72 and beyond the first upper surface 76 of the lead 73 of the package body 70. In this way, the package body 70 is close to the die size. The distance between the side 52A of the die 52 and the side 78 of the package body is as small as about 0.6 mm or less on the wiring side. In an alternative specific example (not shown in the figure), the die 53 extends beyond the periphery of the die pad 72, but does not extend beyond Lead 73. In another alternative specific example (not shown in the figure), the wiring here is only located on the two sides of the module instead of all four sides, and the distance between the die 52A and the package body side that is not connected to the junction can be as small as about 0.1 mm.

Figure 11 shows four leads 73. Only part of the length of the two inner leads 73 is shown behind this, because the inner leads include outer bends, as shown in the lead frame 71 in FIG. 13, which is behind the two outer leads 73.

In FIG. 11, the shorting wire 77 is connected between the bonding pads 53 of the die 55 and the first upper surface 76 of the lead 73. The wire 77 is connected to the first side 76 and is made to be adjacent to the first end 86 of the lead 73 on the side 79 of the package body.

The package 70 in FIG. 11 is a ball grid array package, but a land block grid array ("LGA") package is also possible. As shown in FIG. 12, an array of solder interconnect balls 78 is formed on the lower surface 80 of the outer side of the package body 70. As shown in FIG. In this way, the distance between the second surface 74 of the different lead 73 and the side edge 79 of the package body can be changed (refer to FIG. 12).

The package body 81 in Fig. 11 is made of a molded encapsulant material, but other encapsulation methods can be used. In step 4 of FIG. 1, the encapsulant is filled between the lower surface 89 of the die 52 and the first surface 76 of the lead 73. The non-conductive (ie insulating) adhesive epoxy 87 is located between the lower surface 89 of the die 52 and the first surface 82 of the die pad 72, attaching the die 52 to the die pad 72 and separating the die 52 Above the first surface 76 of the lead 73. In addition, the die 52 extends above the lead 73, and an additional insulating epoxy 87 is applied between the lower surface 89 of the die 52 and the first surface 76 of the lead 73 to separate the die 55 and the lead 73.

Each lead 73 in FIG. 11 has a first surface 76 that is flat or substantially flat. The second surface 74 and the third surface 75 are flat or substantially flat with respect to the first surface 76. The second surface 74 is located at the second end 85 of each lead 73 and is opposite to the first end 86. On the contrary, the second surface 32 of the lead 30 of the package 50 of FIG. 6 and the second surface 64 of the lead 63 of the package 60 of FIG. 8 are located at or respectively close to the periphery of the outer lower surface of the individual packages. .

In FIG. 11, the third surface 75 of each lead 73 is adjacent and is vertically recessed by a distance "H1" from the second surface 74 of the lead 73. The third surface 75 is vertically interposed between the first surface 76 and the second surface 74, and is formed by the same partial etching method of the third surface 33 of the lead 30 in FIGS. 3 and 5 as described above. As shown, the encapsulant material covers the third surface 75, thereby preventing the leads 73 from being vertically pulled apart from the package body 81. The package body material does not cover the second surface 74 of the lead 73.

The die pad 72 of the package body 70 in FIG. 11 has a flat or substantially flat first surface 82. The opposite first surface 82 is a flat or substantially flat second surface 83 and a flat or substantially flat third surface 84 on the periphery. The third surface 84 surrounds the second surface 83 and is vertically recessed by a distance "H1" from the second surface 83. The first surface 82 of the die pad 72 is located at the same level as the first surface 76 of the lead 73.

The third surface 84 of the die pad 72 in FIG. 11 is vertically interposed between the first surface 82 and the second surface 83, and is partially etched by the same partial etching method as the third surface 23 of the die pad 22 in FIG. 3A5 form. As shown in FIG. 11, the encapsulant material covers the third surface 84 of the die pad 72, so as to prevent the die pad 72 from being vertically pulled apart from the package body 81. The encapsulant material does not cover the second surface 83 of the die pad 72. To assist in cooling the package, the second surface 83 of the die pad 72 can be connected by solder interconnect beads or an equivalent conductor connected to an external printed circuit board. In addition, the die pad 72 can be disturbed in step 4 in FIG. 1, so the die pad 72 is covered by the encapsulant material and is completely located inside the package body 81. In this case, the first surface 76 of the lead 73 is located below the first surface 82 of the die pad 72.

FIG. 12 is a bottom plan view of the lower surface 80 of the outer side of the package body 70 in FIG. 11 before the solder interconnection bead is placed on the second surface 74 of the lead 73. As shown, the second face 74 is circular and arranged in an array. The third surface 75 of the lead 73 is not visible in this view, but because the third surface 75 is covered with an encapsulant material, it is located inside the package body 81. The metal corner plates 88 are located at the four corners of the lower surface 80.

Fig. 13 is a plan view of the lead frame 71 suitable for manufacturing the package 70 of Figs. 11 and 12. Unlike the rectangular die pad 22 in FIG. 12, the die pad 72 in FIG. 13 is a segmented strip connected to two parallel sides of the weir 29. The die pad 72 includes a quadrangular rectangular portion 72A, which can be connected to the printed circuit board by solder beads to assist in cooling of the package.

The lead 73 in Figure 13 has a variety of shapes and lengths, depending on its use. In particular, the plurality of leads 73 at the second lead end 85 extend from the weir 29 to the individual circular second surface 74 which is straight in the lateral direction (FIG. 11). The other leads 73 have one or more lateral bends at the second lead end 85 between the weir 29 and the respective second surface 74 (FIG. 11). The two leads 73 at each corner of the lead frame 71 are connected to the same lead end 86, but it is not necessary. In an alternative specific example (not shown in the figure), the lead 73 has a bowl lug or a through hole to join the encapsulant material. In step 6 of Fig. 1, each lead 73 is cut off by the lead frame 71 inside the weir 29 of Fig. 3. The cutting is attached to the outer edge of the metal corner 88 of the lead frame 71 and cut along the lines A--A, B--B, C--C, and D--D in FIG. 13 on the inner side of the weir 29.

In view of the present disclosure, the aforementioned package body, lead frame, and assembly method can be changed in many ways. For example, Figure 14 is a flowchart of an alternative assembly method, where multiple packages along the lines 5, 10, or 11 are formed at the same time. The basic steps of the method in Figure 14 are the same as those in the method in Figure 1, so there is no need to explain the steps in detail. The difference between the method in Fig. 1 and the method in Fig. 14 is that the steps are modified and coordinated to produce multiple packages at the same time. The method in Fig. 14 is performed by step 1 to provide a plurality of lead frames, such as lead frames 20, 62, or 71, which are etched adjacent to each other into a matrix on a single metal strip.

Figure 15 shows a matrix of twelve lead frames 71 in the metal strip 90 (Figure 11). The number of lead frames 71 etched on the strip 90 may vary. For example, thirty-six or sixty-four lead frames 91 can be etched on the strip 90. The lead frame 91 is simultaneously etched on the strip 90 using the aforementioned two-step chemical etching method or the two-step progressive forging followed by chemical etching method. For the configuration in FIG. 15, step 4 in FIG. 14 can be performed using conventional molding techniques to form individual package body 81 on each lead frame 71 of the strip 90. In other words, the mold has a cavity for each die and forms an incomplete package array similar to that shown in FIG. 4. Step 6: Use a punch or a saw to cut each package 70 from the strip 90.

Figure 16 shows an alternative strip 93 in which two matrices with eight lead frames 20 have been etched (Figure 2). Instead of molding the individualized package in step 4 of FIG. 14, a single piece of encapsulant material is applied to all the lead frames 20 of the two matrices individually. These encapsulant blocks can be achieved by first winding the HYSOL 4451 adhesive beads around each matrix of the lead frame 20 in FIG. 16. After the beads are cured, the HYSOL 4450 liquid encapsulant is applied to the inside of the beads, so each die 52 and the incomplete encapsulation disk 50 inside the weir are covered by the encapsulant material. Secondly, the encapsulant material is hardened, for example, by heating to form a fusion block of the aforementioned encapsulant material and placed on each of the two matrices of the lead frame 20. In step 6 of Figure 14, use a saw to cut out eight packages 50 from each of the two matrixes of strips 93. Step 6 is to cut the connection between the lead frame 20 and the die pad 22 and the leads 30. Step 6 also cuts through the encapsulant block to form the sides of the orthogonal encapsulation body.

The description of the specific examples of the invention in the preceding text is intended to be illustrative and not restrictive. Other specific examples of the present invention will be apparent to those in the industry in view of the foregoing disclosure.

<p>1-6...step 60...package body</p><p>3...line 61...lower surface</p><p>20...Lead frame 63...Lead</p><p>21...Tie stalk 64-6...Surface</p><p>22...die pad 70...package body</p><p>23-5...surface 72...crystal red pad</p><p>26-7...Side side 72A...Rectangular part</p><p>28...Port 73...Lead</p><p>29...Weir stalk 74-6...Surface</p><p>30...lead 77...wiring</p><p>31-3...Surface 78-9...Package body side</p><p>34-5...end 80...lower surface</p><p>36...4 lugs 81...package body</p><p>37...side 82-4...top surface</p><p>50... package body 85... terminal</p><p>51...Package body 86...end</p><p>52... Die 87... Adhesive Atmospheric Resin</p><p>52A...die side 88...corner</p><p>53...Wiring pad 89...Lower surface</p><p>54...wiring 90...wiring</p><p>55...side 91...lead frame</p><p>56...lower surface 93...long strip</p><p>57...Solder bumps</p>

The first picture is the flow chart of the packaging system law.

The second figure is a plan view of the lead frame used to manufacture the package.

The third figure is a cross-sectional side view of the die pad and the lead of the second figure taken from the inside of the weir bar along the line 3-3 of the second figure.

The fourth figure is a perspective view of the lead frame of the second figure after the die is attached and encapsulated with a molding encapsulant.

The fifth figure is a cross-sectional side view of a completed package, where the package body is molded and punched to separate the package from the lead frame.

Figure 6 is a cross-sectional view of the package of Figure 5 after the solder bumps are attached to the exposed part of the lead.

The seventh figure is a plan view of the outer bottom surface of the package of the fifth figure.

Figure 8 is a plan view of the lower surface of the outer side of the replacement package.

The ninth figure is a cross-sectional view of the die pads and leads of the lead frame of the package of figure eight taken from the inside of the weir bar.

Figure 10 is a cross-sectional side view of the package of Figure 8.

The eleventh figure is a cross-sectional view of the alternative package, where the die extends laterally around the die pad and part of the lead length.

Fig. 12 is a plan view of the lower surface of the outer side of the package of Fig. 11 without solder interconnect beads.

Figure 13 is a plan view of the lead frame for manufacturing the packages shown in Figures 11 and 12.

Figure 14 is a flow chart of the method of manufacturing multiple packages at the same time.

The fifteenth figure is a plan view of a two matrix of six lead frames etched on a metal strip.

Figure 16 is a plan view of a two matrix of eight lead frames etched on a metal strip.