TWI382506B - Method and structure of multi-chip stack having central pads with upward active surfaces - Google Patents

Description

Active face-up stacking method and structure of central pad type wafer

The present invention relates to semiconductor devices, and more particularly to an active face-up stacking method and configuration for a center pad type wafer.

Currently, in a semiconductor package structure, a plurality of chips having the same memory capacity are allowed to be packaged in the same package to achieve a function of twice or more than a capacity, for example, a wafer-bonded package having two memory capacities of 512M. A package structure having a memory capacity of 1024 M is obtained, which is a so-called "Multi-Chip Module package" (MCM package). A conventional semiconductor wafer, such as a central pad type wafer, is a peripheral pad type wafer. Generally, a center pad type wafer is generally suitable for achieving high speed operation of a semiconductor element. However, in today's industry, various package products such as multi-chip stacks with active face-up are available with Film Over Wire (FOW) as the filling and protection bonding wires for wafer spacers, but most of them only end around. The application of pad-type wafers has a wide range of application problems for central pad type wafers because the bonding wires connecting the central pads are long bonding wires, which have excessively high arcs and bond wires between the wafers. The longer length makes the long wire easy to touch the upper and lower wafers causing short circuit and long wire bonding risk.

In order to achieve a central pad type wafer in a multi-wafer stack package stacked on the front side of the wafer, a conventional method of actively stacking the center pad type wafer is disclosed in the certificate No. I250597 "on the wafer stacking". Multi-chip package method for inter-bonded wire bonding." As shown in FIG. 1 , the first wafer 120 is disposed on the substrate 110 , and a first adhesive layer 130 is formed on the active surface 121 of the first wafer 120 , but must be patterned to make the first adhesive. The layer 130 exposes the pads 122 of the first wafer 120. Next, a wire bonding step is performed to electrically connect the first wafer 120 to the substrate 110 by a plurality of long bonding wires 140. When the die bonding operation is performed to set the second wafer 150, a second adhesive layer 160 (ie, a Film Over Wire (FOW)) may be formed in advance on the back surface 152 of the second wafer 150, the second wafer. The active surface 151 of 150 has a center pad 153. When the second wafer 150 is taken onto the first adhesive layer 130, the first adhesive layer 130 and the second adhesive layer 160 are coated together to form the long solder. Line 140. However, the first adhesive layer 130 has a central gap in the active surface 121 of the first wafer 120, and the second adhesive layer 160 must function to reduce the line arc of the long bonding wires 140 to cause fluidity. Too bad, the second adhesive layer 160 can not completely fill the central void as expected, the adhesion between the wafers is not good, resulting in voids inside the product during packaging, and even when the product is tested for reliability. The situation of bursting.

Another conventional method and structure for the active face-up stacking of a central pad type wafer is disclosed in the "Semiconductor Multi-Wafer Package and Manufacturing Method" of the No. I258823 patent, which is mainly composed of a lower wafer, an insulating support structure, The long bonding wire and the upper wafer are formed, wherein the insulating supporting structure is partially disposed on the active surface of the lower wafer in a pattern, and is located outside the intermediate pad of the lower wafer, for example, strip or mound for direct support The wafer provides an insulating space between the upper and lower wafers, but the intermediate pads of the lower wafer must be exposed. After the wire is applied, an additional layer of glue (the so-called spacer material) is additionally provided on the active surface of the lower wafer. The covering glue is partially coated on the active surface of the lower wafer to partially coat the long bonding wire. In the die bonding operation, the upper wafer is bonded to the lower wafer by thermocompression bonding for a period of time so that the overlying adhesive material is pressed down to diffuse toward the peripheral glue. However, the time of the sticky crystal is very short, which is not enough to provide good gel diffusion, so that the direction of diffusion of the glue is uncontrollable, and the range of gel diffusion is irregular. Therefore, the coated glue which is required to carry out the diffusion of the glue at the time of sticking has a low effective effective crystal area and a poor adhesive strength. In addition, under the hindrance of the insulating support structure, the gap filling effect between the upper and lower wafers of the overlying adhesive material is reduced, and the gap is easily generated at the edge of the insulating support structure, thereby reducing the reliability of the entire packaged product, and the wafer is bonded. It is more difficult to seal the insulating support structure.

In order to solve the above problems, the main object of the present invention is to provide an active face-up stacking method and structure of a center pad type wafer, which has a better effective die area and a die bond strength, and can change the long inter-wafer soldering. The line arc shape of the wire is lower and flatter, does not require a wire with a particularly high hardness, and there is no risk of touching the back side of the wafer. In addition, there is a better sealing effect between the upper and lower wafers, which prevents voids inside the product and has the convenience of die bonding operation.

A second object of the present invention is to provide an active face-up stacking method and structure of a central pad type wafer, which can provide perfect protection of the long bonding wire after the bonding, can increase the adhesion strength between the wafers and increase the welding. The fixing force of the wire on the solder joint on the wafer, which in turn reduces the occurrence of long wire bonding.

The object of the present invention and solving the technical problems thereof are achieved by the following technical solutions. The invention discloses an active face-up stacking method for a central pad type wafer, which mainly comprises the following steps: providing a composite adhesive crystal tape having a first adhesive layer and a second adhesive layer, the first adhesive layer Thinner than the second adhesive layer. The composite adhesive tape is attached to a first wafer, and the first adhesive layer is adhered to the back surface of the first wafer. A second wafer is provided. The second wafer is disposed on a substrate. The active surface of the second wafer is provided with a plurality of central pads, and is electrically connected to the substrate via a plurality of first bonding wires. Performing a die bonding operation to set the first wafer over the active surface of the second wafer. In the die bonding operation, the second adhesive layer is softer than the first adhesive layer to partially seal the first a bonding wire, and by blocking the first adhesive layer to lower the arc height of the first bonding wires, so that the first bonding wires do not touch the back surface of the first bonding chip. The present invention further discloses an active face-up stacking configuration of a center pad type wafer fabricated in accordance with the above method.

The object of the present invention and solving the technical problems thereof can be further achieved by the following technical measures.

In the above-mentioned active face-up stacking method of the central pad type wafer, after the second wafer is provided and before the die bonding operation, the method further includes: coating a liquid insulating layer on the second wafer The active surface is covered, and the insulating layer covers the solder joints of the first bonding wires on the central solder pads, and then the insulating layer is cured.

In the above-mentioned active face-up stacking method of the central pad type wafer, the second adhesive layer can adhere the insulating layer, and the first bonding wire does not touch the first layer by the barrier of the insulating layer. The active surface of the two wafers.

In the active face-up stacking method of the central pad type wafer, the liquid insulating layer may be selected from one of an underfill and a liquid epoxy compound, and has a second wafer. The mobility of the active surface.

In the above-described active face-up stacking method of the center pad type wafer, the liquid-like insulating layer coating method may be selected from one of dashing and spraying.

In the above-mentioned active face-up stacking method of the central pad type wafer, in the die bonding operation, the first bonding wires may be squeezed to have a multi-bend shape, so that the first bonding wires are arc-shaped. The area touches the first adhesive layer, and the arc areas below the first bonding wires touch the insulating layer.

In the above-described active face-up stacking method of the center pad type wafer, in the die bonding operation, the method of making the second adhesive layer softer than the first adhesive layer is to pre-cure the first adhesive layer. .

In the above-described active face-up stacking method of the center pad type wafer, in the die bonding operation, the method of making the second adhesive layer softer than the first adhesive layer is to make the glass of the first adhesive layer The state transition temperature is higher than the glass transition temperature of the second adhesive layer.

In the above-described active face-up stacking method of the central pad type wafer, the first wafer and the second wafer system may be substantially the same, and have the same size and function, and the active surface of the first wafer is also provided. A plurality of central pads.

In the active face-up stacking method of the central pad type wafer, after the die bonding operation, the method further comprises the steps of: forming a plurality of second bonding wires electrically connecting the central pads of the first wafer To the substrate.

In the above-mentioned active face-up stacking method of the central pad type wafer, after the second bonding wire is formed, the method further includes the steps of: providing a plurality of wire fixing members on the active surface of the first wafer to fix The second bonding wires.

In the above-mentioned active face-up stacking method of the central pad type wafer, after the second bonding wire is formed, the method further includes the steps of: forming a gel on the substrate to seal the first wafer, the first Two wafers, the first bonding wires and the second bonding wires.

In the active face-up stacking method of the central pad type wafer, after the sealing body is formed, the method further includes the step of: setting a plurality of solder balls on the lower surface of the substrate.

In the above-described active face-up stacking method of the central pad type wafer, the step of attaching the composite adhesive tape can be implemented at a wafer level, wherein the first wafer is one of the wafers. Cutting the grains.

It can be seen from the above technical solution that the active face-up stacking method and structure of the central pad type wafer of the present invention has the following advantages and effects:

First, by providing a composite adhesive tape as one of the technical means, since the composite adhesive tape has a first adhesive layer and a second adhesive layer, in the die bonding operation, the second adhesive layer is softer than the first The adhesive layer is used to partially seal the long bonding wire, and the barrier of the first adhesive layer is used to lower the arc height of the long bonding wire so that the long bonding wire does not touch the back surface of the upper wafer. The second adhesive layer provides a better effective die area and die bond strength. Therefore, the shape of the line arc of the long wire between the wafers can be changed to be lower and flatter, the wire having a particularly high hardness is not required, and there is no risk of touching the back side of the wafer.

Second, by providing a composite adhesive tape and coating a liquid insulating layer as one of the technical means, since the liquid insulating layer is coated on the active surface of the second wafer, and the insulating layer covers the bonding wire on the central pad The solder joints can increase the adhesion strength of the second adhesive layer and increase the fixing force of the long solder wire on the wafer after the adhesion, thereby reducing the occurrence of the long bond wire.

Third, by providing a composite adhesive tape and coating a liquid insulating layer as one of the technical means, since the second adhesive layer can provide a better effective die area and die bond strength, the first wafer and the second wafer There is a better sealing effect between the wafers to prevent voids inside the product.

The embodiments of the present invention will be described in detail below with reference to the accompanying drawings in which FIG. The components and combinations related to this case, the components shown in the figure are not drawn in proportion to the actual number, shape and size of the actual implementation. Some size ratios are proportional to other related sizes or have been exaggerated or simplified to provide clearer description of. The actual number, shape and size ratio of the implementation is an optional design, and the detailed component layout may be more complicated.

In accordance with an embodiment of the present invention, an active face-up stacking method for a center pad type wafer is illustrated in a cross-sectional view of the elements of FIGS. 2A-2K. The detailed steps are explained below.

First, as shown in FIG. 2A, a composite adhesive tape 210 is provided, which has a first adhesive layer 211 and a second adhesive layer 212. The first adhesive layer 211 is thinner than the second adhesive layer 212. . The first adhesive layer 211 and the second adhesive layer 212 have different adhesive properties and functions, and the two adhesive layers may have different curing temperatures. For example, the curing temperature of the first adhesive layer 211 is lower than the second adhesive. The curing temperature of the layer 212; or, the two adhesive layers have different curing modes, for example, the first adhesive layer 211 may be photocurable, and the second adhesive layer 212 may be thermosetting. In a preferred embodiment, the first adhesive layer 211 can be selected from Dicing Die Adhesive Film (DDAF), and the second adhesive layer 212 can be selected from a Film Over Wire (Film Over Wire). FOW) is preferably a solid film type at room temperature. In different embodiments, the first adhesive layer 211 and/or the second adhesive layer 212 are too glued, and a peelable carrier film may be attached under the second adhesive layer 212 (not shown). In order to facilitate the transfer and attachment of the composite adhesive tape 210. In the case of the die bonding operation, the material of the first adhesive layer 211 must be harder than the second adhesive layer 212. In detail, the main functions of the first adhesive layer 211 include: (1) adhering the crystal back of the wafer, (2) changing to lower the arc height of the wire, and (3) protecting the long wire to avoid contact with the crystal of the wafer. Back. The main functions of the second adhesive layer 212 include: (1) adhering the lower wafer, (2) coating and fixing the long bonding wire between the wafers, and (3) covering the insulating layer.

Referring to FIG. 2B, the composite adhesive tape 210 is attached to a first wafer 220, and the first adhesive layer 211 is adhered to the back surface 221 of the first wafer 220. In this embodiment, the step of attaching the composite adhesive tape 210 can be implemented at a wafer level, wherein the first wafer 220 is an uncut die in the wafer, and the wafer has Complete the production of the required integrated circuit. After this step, the first adhesive layer 211 may be semi-cured or fully cured.

As further shown in FIG. 2C, the wafer is diced by a cutter 224 to separate the first wafer 220. At this time, the first die 220 is attached with the composite adhesive tape 210, and the second adhesive layer 212 is exposed.

As shown in FIG. 2D, a second wafer 230 is provided. The second wafer 230 is disposed on a substrate 240. The active surface 231 of the second wafer 230 is provided with a plurality of central pads 232. A plurality of first bonding wires 250 are electrically connected to the substrate 240, so the first bonding wires 250 can be regarded as long bonding wires. The first bonding wires 250 may be gold wires. In this embodiment, as shown in FIGS. 2B, 2D, and 2H, the first wafer 220 and the second wafer 230 can be substantially the same, and have the same size and function, and the active surface of the first wafer 220 223 also has a plurality of central pads 222. In a preferred embodiment, the second wafer 230 is bonded to the back surface of the second wafer 230 and the upper surface of the substrate 240 by a die bonding layer 233. The first bonding wires 250 have a one-line arc height. The term "arc height" as used herein refers to the height between the highest point of the line arc of the first bonding wires 250 to the active surface 231 of the second wafer 230. Since the first adhesive layer 211 is required to press the first bonding wires 250 downward to reduce the arc height during the die bonding process. Therefore, in the wire bonding process included in this step, it is not necessary to consider the arcing height of the first bonding wires 250, and the production capacity of the wire bonding process is not limited.

After the first bonding wires 250 are formed, as shown in FIG. 2E, a liquid insulating layer 260 is applied to the active surface 231 of the second wafer 230 by a showerhead 261, and the insulating layer 260 is applied. The solder joints (or wire ends, ball ends) of the first bonding wires 250 on the central pads 232 are covered, and the insulating layer 260 is cured. In detail, the main functions of the insulating layer 260 include: (1) protecting the wire bond head, (2) preventing the long wire from touching the surface of the wafer and short-circuiting, and (3) improving the adhesion to the wire coating layer. In one embodiment, the insulating layer 260 can be fully cured or partially cured by heating or irradiating UV light. In this embodiment, the insulating layer 260 may be selected from one of an underfill and a liquid epoxy compound, and has a high fluidity capable of covering the active surface 231 of the second wafer 230, and the insulation Layer 260 is formed with an uneven surface to enhance adhesion strength. More specifically, the coating method of the liquid insulating layer 260 may be selected from one of dashing and spraying, so that the liquid insulating layer 260 may completely cover the active surface 231 of the second wafer 230. And after the insulating layer 260 is cured, the wire ends of the first bonding wires 250 can be fixed to prevent the first bonding wires 250 from contacting the active surface 231 of the second wafer 230, thereby causing a short circuit. The situation. In addition, it is possible to avoid the formation of the first bonding wire 250 by the printing method, and it is also possible to prevent the wire portion of the first bonding wire 250 on the active surface 231 from being contaminated with excessive insulating material.

Referring to FIGS. 2F to 2H, a die bonding operation is performed to place the first wafer 220 over the active surface 231 of the second wafer 230. As shown in FIG. 2F, during the start of the die bonding operation, the second adhesive layer 212 is softer than the first adhesive layer 211, and the first bonding wires 250 may be embedded in the second adhesive layer 212 to The portion is sealed, and the first bonding wires 250 are initially pressed by the first adhesive layer 211 to be bent. Then, in the intermediate process of the die bonding operation, as shown in FIG. 2G, the first wafer 220 is continuously pressed down, and the arc of the first bonding wires 250 is lowered by the barrier of the first adhesive layer 211. The first bonding wires 250 are not touched to the back surface 221 of the first wafer 220, and the overall bending amplitude is gradually reduced. As shown in FIG. 2H, the first wafer 220 is bonded to the insulating layer 260 by the second adhesive layer 212 to complete the above-mentioned die bonding operation. At this time, as shown in FIG. 2H, the first bonding wires 250 are pressed to be multi-bent, so that the arc regions above the first bonding wires 250 touch the first adhesive layer 211, and the The arc regions below the first bonding wires 250 touch the insulating layer 260. Preferably, since the second adhesive layer 212 can adhere to the insulating layer 260, the first bonding wires 250 do not touch the active surface 231 of the second wafer 230 by the barrier of the insulating layer 260. In addition, since the second adhesive layer 212 is converted into a colloidal colloid after being heated, it can provide a better effective crystallite area and a cohesive strength, and can be closely adhered to the liquid insulating layer 260, thereby increasing The adhesion between the second adhesive layer 212 and the insulating layer 260 is to strengthen the overall structure. In a preferred embodiment, the method of making the second adhesive layer 212 softer than the first adhesive layer 211 in the die bonding operation may be pre-curing the first adhesive layer 211, for example, in the above paste. After the steps are attached. In another variation, in the die bonding operation, the method of making the second adhesive layer 212 softer than the first adhesive layer 211 is such that the glass transition temperature of the first adhesive layer 211 is higher than the The glass transition temperature of the second adhesive layer 212 is such that the first adhesive layer 211 has higher fluidity and wettability with respect to the second adhesive layer 212 at the die bonding temperature. Therefore, the first bonding wire 250 can be better protected by the combination of the first adhesive layer 211, the second adhesive layer 212 and the insulating layer 260, and the bonding line arc is controlled at the second bonding. The layer 212 is more flat and does not cause a short circuit with the back surface of the first wafer 220 and the active surface of the second wafer 230, which also reduces the risk of twisting.

Further, as shown in FIG. 2I, after the die bonding operation, the method further includes: forming a plurality of second bonding wires 270 electrically connected to the central pads 222 of the first wafer 220 to The substrate 240. Then, as shown in FIG. 2J, after the second bonding wires 270 are formed, the method further includes: providing a plurality of wire fixing members 271 on the active surface of the first wafer 220 to fix the first Second weld line 270. The wire fixing members 271 may be paste-like agglomerates to fix one of the second bonding wires 270. The wire fixing members 271 can reinforce the overall structure of the second bonding wires 270 to avoid the problem of twisting wires in subsequent processes.

As shown in FIG. 2K, after the second bonding wire 270 is formed, the method further includes: forming a glue 280 on the substrate 240 to seal the first wafer 220, the second wafer 230, and the Some first bonding wires 250 and the second bonding wires 270. In detail, the encapsulant 280 can completely cover the upper surface of the substrate 240. Finally, after forming the encapsulant 280, the method further includes: setting a plurality of solder balls 241 on the lower surface of the substrate 240 (as shown in FIG. 3), that is, completing the central pad type wafer of the present invention. The active face is stacked upwards.

In the present invention, by providing the composite adhesive tape as one of the technical means, since the composite adhesive tape 210 is composed of a two-layer structure, the first adhesive layer 211 and the second adhesive are operated at the die bonding operation. The layer 212 exhibits a relatively hard and soft material property, so that the second adhesive layer 212 can embed the first bonding wires 250 to partially seal the first bonding wires 250 during the die bonding operation. Further bonding to the insulating layer 260 or the second wafer 230. In addition, the arc of the first bonding wires 250 is lowered by the barrier of the first adhesive layer 211 such that the first bonding wires 250 do not touch the back surface of the first wafer 220. That is, the present invention can utilize the harder material properties of the first adhesive layer 211 during the die bonding process, and press the first bonding wires 250 downward to naturally lower the arc height of the first bonding wires 250. Therefore, the shape of the line arc of the first bonding wire 250 can be changed to be lower and flatter, the bonding wire having a particularly high hardness is not required, and there is no risk of touching the back surface 221 of the first wafer 220. The second adhesive layer 212 can provide a better effective die area and a die bond strength, and effectively coat the first bond wires 250 in a limited thickness, thereby reducing the multi-wafer stack height.

In addition, since the liquid insulating layer 260 is coated on the active surface 231 of the second wafer 230, and the insulating layer 260 covers the solder joints of the first bonding wires 250 on the central pads 232, the The adhesion of the first bonding wires 250 on the second wafer 230 and the adhesion strength to the second bonding layer 212 can also reduce the occurrence of the first bonding wires 250. Further, since the composite adhesive tape 210 and the insulating layer 260 are closely adhered to each other without gaps, the problem of easily creating voids inside the product is eliminated, and the yield of the product is greatly increased, and A burst will occur in subsequent linear tests.

The present invention also discloses an active face-up stack configuration of a center pad type wafer fabricated using the foregoing method, which is illustrated in FIG. The active face-up stacking structure of the center pad type wafer mainly comprises a composite die bonding tape 210, a first wafer 220 and a second wafer 230. The composite adhesive tape 210 has a first adhesive layer 211 and a second adhesive layer 212. The first adhesive layer 211 is thinner than the second adhesive layer 212. In a preferred embodiment, the first adhesive layer 211 is a Dicing Die Adhesive Film (DDAF), and is disposed between the second adhesive layer 212 and the first adhesive layer 211, and The second adhesive layer 212 can be a Film Over Wire (FOW), so the material of the first adhesive layer 211 is harder than the second adhesive layer 212. The second adhesive layer 212 can serve as a stress buffer layer to avoid straining the first bonding wires 250. In this embodiment, the composite adhesive tape 210 is completely covered on the back surface 221 of the first wafer 220, and the back surface 221 of the first wafer 220 is protected by the first adhesive layer 211 to avoid possible damage.

The second wafer 230 is disposed on a substrate 240. The active surface 231 of the second wafer 230 is provided with a plurality of central pads 232 and electrically connected to the substrate 240 via a plurality of first bonding wires 250. The first wafer 220 is disposed on the active surface 231 of the second wafer 230. The second adhesive layer 212 is softer than the first adhesive layer 211 to partially seal the first bonding wires 250. The arc of the first bonding wires 250 is lowered by the first adhesive layer 211 to prevent the first bonding wires 250 from contacting the back surface 221 of the first wafer 220. In a preferred embodiment, the first wafer 220 and the second wafer 230 can be substantially the same, and have the same size and function, and the active surface 223 of the first wafer 220 is also provided with a plurality of central pads. 222.

In the present invention, an insulating layer 260 coated in a liquid state may be further formed on the active surface 231 of the second wafer 230. The insulating layer 260 covers the first bonding wires 250 on the central pads 232. Solder joints and cure. In detail, the first bonding wires 250 may be in a plurality of curved shapes, the arc regions of the first bonding wires 250 touch the first adhesive layer 211, and the first bonding wires 250 are under the arc. The area touches the insulating layer 260. In addition, the second adhesive layer 212 can adhere to the insulating layer 260. The first bonding wire 250 does not touch the active surface 231 of the second wafer 230 by the barrier of the insulating layer 260. Preferably, the liquid insulating layer 260 is selected from one of an underfill and a liquid epoxy compound, and has fluidity capable of filling the active surface 231 of the second wafer 230. Therefore, the insulating layer 260 can completely cover the active surface 231 of the second wafer 230. After curing, the first bonding wires 250 can be further fixed to prevent the first bonding wires 250 from contacting the second surface. The active surface 231 of the wafer 230 causes a short circuit condition.

Further, in this embodiment, a plurality of second bonding wires 270, a plurality of wire fixing members 271, a glue body 280, and a plurality of solder balls 241 may be further included. The second bonding wires 270 are electrically connected to the central pad 222 of the first wafer 220 to the substrate 240 . The wire fixing members 271 are disposed on the active surface 223 of the first wafer 220 to fix the second bonding wires 270, so that the structures of the second bonding wires 270 can be reinforced to avoid the occurrence of twisted wires. . The encapsulant 280 can be formed on the substrate 240 to seal the first wafer 220, the second wafer 230, the first bonding wires 250, and the second bonding wires 270. In addition, the solder balls 241 can be disposed on the lower surface of the substrate 240 such that the active surface-up stack configuration of the center pad type wafer can be externally connected.

The above is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Although the present invention has been disclosed in the above preferred embodiments, it is not intended to limit the present invention. Any simple modifications, equivalent changes and modifications made without departing from the technical scope of the present invention are still within the technical scope of the present invention.

110. . . Substrate

120. . . First wafer

121. . . Active surface

122. . . Solder pad

130. . . First adhesive layer

140. . . Long wire

150. . . Second chip

151. . . Active surface

152. . . back

153. . . Solder pad

160. . . Second sticky layer

210. . . Composite adhesive tape

211. . . First adhesive layer

212. . . Second adhesive layer

220. . . First wafer

221. . . back

222. . . Central pad

223. . . Active surface

224. . . Tool

230. . . Second chip

231. . . Active surface

232. . . Central pad

233. . . Binder layer

240. . . Substrate

241. . . Solder ball

250. . . First wire bond

260. . . Insulation

261. . . Nozzle

270. . . Second wire

271. . . Wire fastener

280. . . Sealant

Fig. 1 is a schematic cross-sectional view showing a conventional in-plane stacking method for a conventional center-type wafer.

2A to 2K are cross-sectional views showing the components in the process of the active face-up stacking method of the center pad type wafer according to an embodiment of the present invention.

Figure 3 is a cross-sectional view showing the active face-up stacking configuration of a center pad type wafer in accordance with an embodiment of the present invention.

210. . . Composite adhesive tape

211. . . First adhesive layer

212. . . Second adhesive layer

220. . . First wafer

221. . . back

222. . . Central pad

223. . . Active surface

230. . . Second chip

231. . . Active surface

232. . . Central pad

233. . . Binder layer

240. . . Substrate

250. . . First wire bond

260. . . Insulation

Claims (14)

An active face-up stacking method for a central pad type wafer, comprising: providing a composite adhesive tape having a first adhesive layer and a second adhesive layer, wherein the first adhesive layer is thinner than the second adhesive layer Laying the composite adhesive tape to a first wafer, bonding the back surface of the first wafer with the first adhesive layer; providing a second wafer, the second wafer is disposed on a substrate, the first The active surface of the two chips is provided with a plurality of central pads, and is electrically connected to the substrate through a plurality of first bonding wires; and performing a die bonding operation to set the first wafer to the active surface of the second wafer Above, in the die bonding operation, the second adhesive layer is softer than the first adhesive layer to partially seal the first bonding wires, and the first adhesive layer is blocked by the first adhesive layer to reduce the first The arc of the bonding wire is high so that the first bonding wires do not touch the back surface of the first wafer. According to the active face-up stacking method of the central pad type wafer according to claim 1, in the step of providing the second wafer and before performing the die bonding operation, the method further comprises: coating a liquid insulating layer on the first The active surface of the two wafers is covered, and the insulating layer covers the solder joints of the first bonding wires on the central solder pads, and then the insulating layer is cured. An active face-up stacking method of a central pad type wafer according to claim 2, wherein the second adhesive layer adheres to the insulation The layer, by the barrier of the insulating layer, prevents the first bonding wires from contacting the active surface of the second wafer. An active face-up stacking method for a central pad type wafer according to claim 2, wherein the liquid insulating layer is selected from one of an underfill and a liquid epoxy compound, and has a capacity to be filled. The fluidity of the active surface of the second wafer. The active face-up stacking method of the central pad type wafer according to the fourth aspect of the patent application, wherein the liquid-like insulating layer is coated by one of a dipping and spraying. The active face-up stacking method of the central pad type wafer according to the second aspect of the patent application, wherein in the die bonding operation, the first bonding wires are pressed to be multi-bend, so that the first welding The arc area above the line touches the first adhesive layer, and the arc areas below the first bonding lines touch the insulating layer. The active face-up stacking method of a central pad type wafer according to claim 1, wherein in the die bonding operation, the method of making the second adhesive layer softer than the first adhesive layer is pre-cured. The first adhesive layer. An active face-up stacking method for a central pad type wafer according to claim 1, wherein in the die bonding operation, the method of making the second adhesive layer softer than the first adhesive layer is the first The glass transition temperature of the adhesive layer is higher than the glass transition temperature of the second adhesive layer. Active in accordance with the central pad type wafer of item 1 of the patent application scope The face-up stacking method, wherein the first wafer and the second wafer are substantially identical in size, and have the same size and function, and the active surface of the first wafer is also provided with a plurality of central pads. According to the active face-up stacking method of the central pad type wafer according to claim 9 of the patent application, after the die bonding operation, the further comprising the steps of: forming a plurality of second bonding wires electrically connected to the first chip Central pad to the substrate. According to the active face-up stacking method of the central pad type wafer of claim 10, after the second bonding wire is formed, the method further comprises: providing a plurality of wire fixing members on the active surface of the first wafer To fix the second bonding wires. According to the active face-up stacking method of the central pad type wafer of claim 10, after forming the second bonding wire, the method further comprises the steps of: forming a gel on the substrate to seal the first wafer The second wafer, the first bonding wires, and the second bonding wires. According to the active face-up stacking method of the central pad type wafer of claim 12, after the sealing body is formed, the method further comprises the steps of: setting a plurality of solder balls on the lower surface of the substrate. According to the active face-up stacking method of the central pad type wafer of claim 1, wherein the step of attaching the composite adhesive tape is performed at a wafer level, wherein the first wafer is a wafer One of the uncut grains.