Patent Publication Number: US-2020286748-A1

Title: Lid attach process and dispenser head

Description:
PRIORITY CLAIM 
     The present application is a continuation of U.S. application Ser. No. 15/341,165, filed Nov. 2, 2016, which is a divisional of U.S. application Ser. No. 14/543,307, filed Nov. 17, 2014, which is divisional of U.S. application Ser. No. 13/494,814, filed Jun. 12, 2012, now U.S. Pat. No. 8,916,419, issued Dec. 23, 2014, which claims priority of U.S. Provisional Application No. 61/617,383, filed Mar. 29, 2012, which are incorporated herein by reference in their entireties. 
    
    
     FIELD 
     The disclosure relates generally to the fabrication of semiconductor packages, and more particularly, to a high throughput and accurate lid attach process and apparatus. 
     BACKGROUND 
     The assembly of a semiconductor package plays an important role in semiconductor fabrication and thermal management. A conventional semiconductor package includes a lid, one or more die, seal adhesive, interconnects, a substrate, and/or a thermal interface material (TIM). 
     The die is placed on the substrate through a die-attach process. Typically, the die-attach process involves attaching a flip-chip type die to the substrate by interconnects through a reflow process. In a lid attach process, the seal adhesive is dispensed on a periphery of the substrate by a needle-type dispensing head, for example, for attaching the lid later. The TIM is applied to a bottom side of the die (i.e., the side opposite the interconnects) by the needle-type dispensing head. An underfill may be applied to the interconnects, the die, and the substrate to at least reduce stress to the semiconductor package. The lid is thereafter placed on the substrate, typically making contact with the seal adhesive and the die by way of the TIM. 
     In the conventional lid attach process, the needle-type dispensing head is often used for both dispensing the seal adhesive and the TIM. The seal adhesive and TIM are typically contained in a container such as a flask or vial and dispensed through tubes in the needle-type dispensing head by capillary action. There are disadvantages, however in dispensing either the seal adhesive or TIM via the needle-type dispensing head process. For large or small die applications, the throughput can be reduced due to the time needed to apply complicated TIM dispensing patterns to the die.  FIG. 1  is a plan view of a semiconductor package undergoing a stage of fabrication where a complicated dispensing pattern  10  has been applied to a top of the die  20 . Further, the seal adhesive may be improperly dispensed on the substrate. These may cause voids on the substrate or the seal adhesive may shift from the correct dispensing pattern  10  thereby compromising the integrity of the semiconductor package.  FIG. 1  shows an example of seal adhesives  30  applied on the periphery of substrate  70  and a seal adhesive  40  that has shifted from its intended location  50 . Further still, in the needle-type dispensing process, the dispensing pattern and weight may be difficult to control leading to insufficient TIM coverage on the die or insufficient adhesive coverage on the substrate. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It is emphasized that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion. 
         FIG. 1  is a plan view of a semiconductor package showing a dispensing pattern applied to the top of a die. 
         FIG. 2 a    is a cross-sectional view of a semiconductor package having a die attached to a substrate undergoing a stage of lid attachment where adhesive material is attached to the substrate, according to aspects of the present disclosure. 
         FIG. 2 b    is a side view of a stamp-type dispensing head of an adhesive dispenser, according to one embodiment of the present disclosure. 
         FIG. 2 c    is a bottom view of the stamp-type dispensing head of  FIG. 2 b   , according to one embodiment of the present disclosure. 
         FIG. 3 a    is a cross-sectional view of the semiconductor package of  FIG. 2 a    showing a further step of applying a thermal interface material (TIM) on top of the die, according to aspects of the present disclosure. 
         FIG. 3 b    is a side view of a stamp-type dispensing head of a TIM dispenser, according to an embodiment of the present disclosure. 
         FIG. 3 c    is a bottom view of the stamp-type dispensing head of  FIG. 3 b   , according to one embodiment of the present disclosure. 
         FIG. 4  is a cross-sectional view of the semiconductor package of  FIG. 3 a    showing the package undergoing a further step of attaching a lid to the substrate, according to aspects of the present disclosure. 
         FIG. 5 a    is a cross-sectional view of a semiconductor package depicting a die attached to a substrate undergoing a stage of lid attachment where an adhesive material and a TIM are concurrently applied to the substrate and the die, respectively, according to aspects of the present disclosure. 
         FIG. 5 b    is a side view of a stamp-type dispensing head of a combination adhesive and TIM dispenser, according to an embodiment of the present disclosure. 
         FIG. 5 c    is a bottom view of the stamp-type dispensing head of  FIG. 5 b   , according to one embodiment of the present disclosure. 
         FIG. 6  is a cross-sectional view of the semiconductor package of  FIG. 5 a    showing the package undergoing a further step of attaching a lid to the substrate, according to aspects of the present disclosure. 
         FIG. 7  is a cross-sectional view of a semiconductor package undergoing a lid attachment process where TIM is applied to a top of a die by stencil printing, according to various aspects of the present disclosure. 
         FIG. 8  is a cross-sectional view of a semiconductor package undergoing a lid attachment process where adhesive material is attached to the substrate by way of dipping a periphery of a lid in adhesive material and then attaching the lid to the substrate, according to various aspects of the present disclosure. 
         FIG. 9  is a cross-sectional view showing a process of dipping a lid, attached to a lid carrier into a dipping tank in order to apply adhesive material to the periphery of the lid, according to one embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, specific details are set forth to provide a thorough understanding of embodiments of the present disclosure. However, one having an ordinary skill in the art will recognize that embodiments of the disclosure can be practiced without these specific details. In some instances, well-known structures and processes are not described in detail to avoid unnecessarily obscuring embodiments of the present disclosure. 
     Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. It should be appreciated that the following figures are not drawn to scale; rather, these figures are merely intended for illustration. For convenience of illustration and ease of understanding, the features and dimensions of the semiconductor package have been exaggerated in some aspects. However, one skilled in the art will appreciate that, in an actual device, these features may have relative dimensions that are different from those suggested in the figures. 
       FIGS. 2 a , 3 a   , and  4  are cross-sectional side views of a semiconductor package  5  at various stages of fabrication undergoing a lid attach process, according to an embodiment of the present disclosure. The semiconductor package  5  placed on a supporting boat or carrier  60  undergoes a lid attach process starting from a right side going to a left, as indicated by an arrow pointing to the left in these figures. It is understood that  FIGS. 2 a , 3 a   , and  4  have been simplified for a better understanding of the inventive concepts of the present disclosure.  FIG. 2 a    shows semiconductor package  5  having a die  20  (such as a microprocessor, a chipset, a memory device, an ASIC, any heat generating device, or the like), illustrated as a flip-chip attached to a substrate  70 , which may be a motherboard, interposer, a back surface of another dice, or the like. Die  20  may comprise of one or more dies. By way of a die-attach process, die  20  is attached to substrate  70  by interconnects  90 , such as solder bumps or solder balls. An underfill  100 , as known in the art, may be disposed between die  20 , interconnects  90 , and the substrate  70  to strengthen the semiconductor package  5 , prevent bump cracks, and/or enhance thermal dissipation of package. 
     According to an aspect of the present disclosure, an adhesive material  110  is dispensed on the substrate  70 . Adhesive material  110  may comprise any material suitable for sealing a lid onto substrate  70 , such as epoxies, urethane, polyurethane, silicone elastomers, and the like. In one embodiment, adhesive material  110  is a wet-dispensed adhesive such as SYLGARD® 577, EA6700 or EA6900 all produced by Dow Corning (Midland, Mich., USA). The adhesive material  110  is generally wet dispensed to an outer portion or a periphery or edges of substrate  70  by means of an adhesive dispenser  115  having a stamp-type dispensing head  120 .  FIG. 2 b    is a side view of the stamp-type dispensing head  120  of adhesive dispenser  115 , and  FIG. 2 c    is a bottom view of the stamp-type dispensing head  120  showing adhesive material  110  attached to the stamp-type dispensing head  120 , according to one embodiment of the present disclosure. The adhesive material  110  attached to the stamp-type dispensing head  120  may include a contiguous or non-contiguous pattern, as is understood by those skilled in the art. The adhesive dispenser  115  includes a container (not shown), such as a syringe for storing the adhesive material  110  and the stamp-type dispensing head  120  includes one or more conduits  125 . By an interaction force, such as for example, a pump extrusion force or a rotary pump extrusion force, the adhesive material  110  is pumped from the syringe into the one or more conduits (adhesive material  110  flow shown by arrows) and out through the orifice(s)  130  for application to substrate  70 . It is understood that the conduits  125  may be arranged in the stamp-type dispensing head  120  differently from the one(s) shown in  FIG. 2 b    and that any number of arrangements may be contemplated. 
     Following application of the adhesive material  110  to the substrate  70 ,  FIG. 3 a    shows the semiconductor package  5  undergoing a further step of applying a thermal interface material (TIM)  150  to the top of die  20 , according to aspects of the present disclosure. The thermal interface material  150  may include but is not limited to, thermal grease, phase-change material, metal filled polymer matrix, and solder [alloys of lead, tin, indium, silver, copper, bismuth, and the like (most preferred is indium or lead/tin alloy]). If the thermal interface material  150  is a solid, it may be heated to a temperature at which it undergoes a solid to liquid transition and then may be applied in liquid form to the surface of a die. 
     According to one embodiment of the present disclosure, the TIM  150  is generally wet-dispensed to the top of die  20  by means of a TIM dispenser  135  having a stamp-type dispensing head  140 .  FIG. 3 b    is a side view of the stamp-type dispensing head  140  of TIM dispenser  135 , and  FIG. 3 c    is a bottom view of the stamp-type dispensing head  140  showing TIM  150  attached to the stamp-type dispensing head  140 , according to an embodiment of the present disclosure. The TIM dispenser  135  includes a container (not shown), such as a syringe for storing the TIM  150  and the stamp-type dispensing head  140  includes one or more conduits  145 . By an interaction force, such as for example, a pump extrusion force or a rotary pump extrusion force the TIM  150  is pumped from the syringe into the one or more conduits (TIM flow shown by arrows) and out through the one ore more orifices  160  for application to a top surface of die  20 . It is understood to one of ordinary skill in the art that the conduits  145  may be arranged in the stamp-type dispensing head  140  differently the one(s) shown in  FIG. 3 b    and that any number of arrangements may be contemplated. 
     According to another embodiment, TIM  150  may be applied to a top surface of die  20  by means of stencil printing.  FIG. 7  shows semiconductor package  5  undergoing a process of stencil printing whereby, in a first step a stencil  220  is placed over the top surface of the die  20 , the stencil  220  having a patterned opening  230  therein. The stencil  220  is a thin flat material, such as stainless steel that has one or more openings or apertures through which TIM  150  is applied or printed. It is understood that any number of stencils, for the application of forming TIM  150  on top of die  20  may be used and any number of patterned openings  230  may be contemplated. In a second step, TIM  150  is deposited, preferably in liquid form on top of die  20  in the opening  230  of stencil  220 . In a third step, excess TIM  150  is squeezed or otherwise scraped off from the opening  230  by a blade or scraper  240  in order to form a generally flat TIM  150 , the generally flat TIM  150  being adapted to interface with a lid that is to be later placed on top of TIM  150 . In a fourth step, the stencil  220  is removed from the top surface of die  20 . An advantage of applying TIM  150  on die  20  in this manner is that TIM  150  may be formed on a batch of dies at the same time. Batch processing of TIM saves time, increases throughput, and forms uniform TIM dispensing layers when compared to other types of TIM dispensing processes, such as needle-type dispensing. 
     After the TIM  150  is applied to die  20 , semiconductor package  5  undergoes a further step of attaching a lid  170  to the substrate  70  (as depicted in  FIG. 4 ). Lid  170  is preferably constructed from a thermally conductive material, such as copper, copper alloys, aluminum, aluminum alloys, and the like and may be formed of any other suitable materials for application of the present disclosure. As shown in  FIG. 4 , lid  170  is positioned over die  20 , lowered and thereafter placed on top of the adhesive material  110  and on top of the TIM  150  by a lid carrier  175 , to thereby encapsulate and protect the die  20 . It is understood that additional processes may be performed before, during, or after the adhesive and/or TIM application processes to complete the fabrication of the semiconductor device, but these additional processes are not discussed herein in detail for the sake of simplicity. For example, heat may be applied to the semiconductor package  5  to cure the structure by increasing the temperature of the TIM  150  and the adhesive material  110 . 
       FIGS. 5 a    and  6  are cross-sectional side views of the semiconductor package  5  at various stages of fabrication undergoing a lid attach process, according to another embodiment of the present disclosure. As discussed previously, the semiconductor package  5  is placed on the supporting boat or carrier  60  and undergoes the lid attach process starting from a right side and going to a left side, as shown by an arrow pointing to the left. It is understood that  FIGS. 5 a    and  6  have been simplified for a better understanding of the inventive concepts of the present disclosure. 
     In this embodiment, an adhesive material  110  and a TIM  150  are applied concurrently onto a periphery of the substrate  70  and a top surface of die  20 , respectively by a combination adhesive and TIM dispenser  180  having a stamp-type dispensing head  190 .  FIG. 5 b    is a side-view of the stamp-type dispensing head  190  of the combination adhesive and TIM dispenser  180 , and  FIG. 5 c    is a bottom view of the stamp-type dispensing head  190  showing both adhesive material  110  and TIM  150  attached to the stamp-type dispensing head  190 , according to an embodiment of the present invention. The combination adhesive and TIM dispenser  180  includes a container (not shown), such as a syringe for storing the adhesive material  110  and TIM  150  and the stamp-type dispensing head  190  includes one or more conduits (not shown for simplicity and clarity). By an interaction force, such as for example, a pump extrusion force or a rotary pump extrusion force the adhesive material  110  and TIM are dispensed or pumped from the container or syringe into the respective conduits and out through orifice  200  and orifice  210  for application to substrate  70  and die  20 , respectively. It is understood that the conduits may be arranged in the stamp-type dispensing head  190  in any number of configurations contemplated. 
     Following application of the adhesive material  110  to the substrate  70  and TIM  150  to the die  20 ,  FIG. 6  shows the semiconductor package  5  undergoing a further step of attaching a lid  170  to the substrate  70 . Lid  170  is positioned over die  20 , lowered and thereafter placed on top of the adhesive material  110  and TIM  150  by a lid carrier  175  to thereby encapsulate the die  20 . 
       FIG. 8  is a cross-sectional side view of the semiconductor package  5  at various stages of fabrication undergoing a lid attach process, according to yet another embodiment of the present disclosure. TIM  150  is firstly applied on a top surface of die  20 . According to one embodiment, TIM  150  is applied to die  20  by a TIM dispenser  135  having a stamp-type dispensing head  140 . According to another embodiment, TIM  150  is applied to die  20  by a stencil printing process. As this process was described above with reference to  FIG. 7 , it will not be repeated again. In a further process of applying the adhesive material  110  to substrate  70 , as shown in  FIG. 9  the periphery of a lid  170 , which is attached to a lid carrier  175  is dipped in a dipping tank  250  containing adhesive material  110 . The adhesive material  110  thereby attaches to the periphery of the lid  170 . With reference back to  FIG. 8 , lid  170  now containing the adhesive material attached to the periphery thereof is then positioned over die  20 , lowered and thereafter placed on top of TIM  150  and substrate  70  with the adhesive material  110  being adapted to interface with the periphery of the substrate  70 . 
     Advantages of one or more embodiments of the present disclosure may include one or more of the following. 
     In one or more embodiments, instead of dispensing complicated TIM patterns on the die, simple and more straightforward patterns can be dispensed on the die. This decreases the time needed to apply a complicated dispensing pattern thereby increasing the throughput of the assembly process. 
     In one or more embodiments of the present disclosure, employing a stamp-type dispensing head to dispense a layer, such as an adhesive layer a more uniform dispensing layer can be achieved, providing for more sufficient adhesive coverage on the substrate. 
     In one or more embodiments of the present disclosure, both the adhesive and TIM dispensing processes are combined into a single step, thereby saving time and increasing throughput. 
     In one or more embodiments of the present disclosure, an advantage of applying the TIM on a die employing stencil printing permits the TIM to be formed on a batch of dies at the same time. Batch processing of TIM saves time, increases throughput, and forms uniform TIM dispensing layers when compared to other types of TIM dispensing processes, such as needle-type dispensing. 
     Although much of the description herein is directed to the dispensing of adhesive material and/or thermal interface material on a semiconductor package in a lid attach process, it is to be understood that aspects of the present disclosure may apply broadly to the dispensation of the adhesive material and/or thermal interface material or, for that matter, any other like material in a package structure from which one may want to attach and/or assemble components in package structures. 
     The present disclosure has described various exemplary embodiments. 
     According to one embodiment, a semiconductor package assembly process, comprises attaching one or more dies to a substrate; applying an adhesive material on a periphery of the substrate by an adhesive dispenser; applying a TIM on a top surface of the die; and positioning a lid over the one or more dies and placing the lid on top of the adhesive material and the TIM by a lid carrier to encapsulate the one or more dies. 
     According to another embodiment, a semiconductor package assembly process, comprises attaching one or more dies to a substrate; applying concurrently an adhesive material on a periphery of the substrate and a TIM on a top surface of the die by a combination adhesive and TIM dispenser; and positioning a lid over the one or more dies and placing the lid on top of the adhesive material and the TIM by a lid carrier to encapsulate the one or more dies. 
     According to yet another embodiment, a lid attach process, comprises attaching one or more dies to a substrate; applying a TIM on a top surface of the die; providing a lid and dipping the periphery of the lid by a lid carrier in a dipping tank of adhesive material such that the adhesive material attaches to the periphery of the lid; and positioning the lid over the one or more dies and placing the lid on the top of the TIM with the adhesive material being adapted to interface with the periphery of the substrate. 
     According to yet another embodiment, an adhesive dispenser comprises a stamp-type dispensing head for applying an adhesive material to a substrate, the adhesive dispenser having a container for storing the adhesive material and one or more conduits in the stamp-type dispensing head for dispensing the adhesive material therethrough by a pump extrusion force. 
     According to yet another embodiment, a TIM dispenser comprises a stamp-type dispensing head for applying a TIM to a die, the TIM dispenser having a container for storing the TIM and one or more conduits in the stamp-type dispensing head for dispensing the TIM from the container and through the one or more conduits by a pump extrusion force. 
     According to yet another embodiment, a combination adhesive and TIM dispenser comprises a stamp-type dispensing head for applying an adhesive material to a substrate and a TIM to a die, the combination dispenser having a container for storing the adhesive material and/or TIM, and one or more conduits in the stamp-type dispensing head for dispensing the adhesive material and/or TIM from the container and through the one or more respective conduits by a pump extrusion force. 
     An aspect of this description relates to an adhesive dispenser comprises a dispensing head. The dispensing head comprises an adhesive material applicator portion on a first level of the dispensing head. The adhesive material applicator portion corresponds to a periphery of a package. The dispensing head also comprises a thermal interface material (TIM) applicator portion on a second level of the dispensing head different from the first level. The TIM applicator portion corresponds to a die of the package. The dispensing head further comprises an adhesive material conduit configured to supply the adhesive material applicator portion with an adhesive material. The dispensing head additionally comprises a TIM conduit configured to supply the TIM applicator portion with a TIM. 
     Another aspect of this description relates to a combination adhesive and thermal interface material (TIM) dispenser. The dispenser comprises a stamp-type dispensing head configured to apply (1) an adhesive material to a periphery of a surface of a substrate and (2) a TIM to a top surface of a die attached to the surface of the substrate. The dispenser also comprises an adhesive material conduit configured to supply an adhesive material applicator portion of the stamp-type dispensing head with the adhesive material. The dispenser further comprises a TIM conduit configured to supply a TIM applicator portion of the stamp-type dispensing head with the TIM. 
     A further aspect of this description relates to a dispensing head comprising a first applicator region having an adhesive material applicator portion. The dispensing head also comprises a second applicator region having a thermal interface material (TIM) applicator portion. The dispensing head further comprises an adhesive material conduit configured to supply the adhesive material applicator portion with adhesive material. The dispensing head additionally comprises a TIM conduit configured to supply the TIM applicator portion with TIM. The dispensing head is configured to apply (1) the adhesive material to a periphery of a surface of a substrate using the adhesive material applicator portion and (2) the TIM to a top surface of a die attached to the surface of the substrate using the TIM applicator portion. The first applicator region and the second applicator region are arranged to accommodate the die within a cavity between the first applicator region and the second applicator region. 
     An aspect of this description relates to a lid attach process. The lid attach process includes dipping a periphery of a lid in a dipping tank of adhesive material such that the adhesive material attaches to the periphery of the lid. The lid attach process further includes positioning the lid over a die attached to a substrate using a lid carrier, wherein the periphery of the lid is aligned with a periphery of the lid carrier. The lid attach process further includes attaching the lid to the substrate with the adhesive material forming an interface with the substrate. The lid attach process further includes contacting a thermal interface material (TIM) on the die with the lid. In some embodiments, the lid attach process further includes coating the die with the TIM prior to attaching the lid to the substrate. In some embodiments, coating the die with the TIM includes using a stamp-type dispensing head. In some embodiments, coating the die with the TIM includes using a stencil printing process. In some embodiments, the lid attach process further includes moving the die from a first position to a second position prior to positioning the lid over the die. In some embodiments, dipping the periphery of the lid in the dipping tank includes dipping the lid in the dipping tank to a depth sufficient to avoid adhesive material attaching to a central portion of the lid. 
     An aspect of this description relates to a dispenser head. The dispenser head includes a first applicator portion on a first level of the dispensing head, the first applicator portion extending along an entirety of a periphery of the dispensing head. The dispenser head further includes a second applicator portion on a second level of the dispensing head different from the first level, the second applicator portion being spaced from the periphery of the dispensing head. The dispenser head further includes a first conduit configured to supply a first material to the first applicator portion. The dispenser head further includes a second conduit configured to supply a second material to the second applicator portion, wherein the first material is different from the second material. In some embodiments, the first applicator portion surrounds the second applicator portion in a plan view. In some embodiments, the dispenser head further includes a first portion housing the first conduit and the second conduit, wherein the first portion extends in a first direction; a second portion housing the second applicator portion, wherein the second portion extends in a second direction perpendicular to the first direction; and a third portion housing the first applicator portion, wherein the third portion extends in the first direction. In some embodiments, the second portion includes a central region corresponding to the second applicator portion; and a transition region between the central region and the third portion of the dispenser head. In some embodiments, the central region is recessed with respect to the transition region. In some embodiments, the transition region is free of an applicator portion. In some embodiments, the first applicator portion is recessed with respect to an outermost edge of the third portion of the dispenser head. 
     An aspect of this description relates to a method. The method includes applying an adhesive material to a peripheral region of a substrate using a dispensing head. The method further includes applying a thermal interface material (TIM) to a die connected to the substrate using the dispensing head. The method further includes positioning a lid over the die and the substrate, wherein a periphery of the lid is aligned with the adhesive material. The method further includes attaching the periphery of the lid to the substrate with the adhesive material forming an interface with the substrate. In some embodiments, the method further includes contacting a central portion of the lid to the TIM. In some embodiments, applying the adhesive material includes applying the adhesive material through a first conduit in the dispensing head. In some embodiments, applying the TIM includes applying the TIM through a second conduit in the dispensing head, and the first conduit is separate from the second conduit. In some embodiments, applying the adhesive material to the peripheral region of the substrate includes contacting the substrate with the dispensing head. In some embodiments, applying the TIM to the die includes applying the TIM to less than an entirety surface of the die. In some embodiments, the method further includes moving the substrate from a first position to a second position prior to positioning the lid over the substrate. 
     In the preceding detailed description, specific exemplary embodiments have been described. It will, however, be apparent to a person of ordinary skill in the art that various modifications, structures, processes, and changes may be made thereto without departing from the broader spirit and scope of the present disclosure. The specification and drawings are, accordingly, to be regarded as illustrative and not restrictive. It is understood that embodiments of the present disclosure are capable of using various other combinations and environments and are capable of changes or modifications within the scope of the claims.