Patent Publication Number: US-2007116862-A1

Title: Semiconductor Device Having Resin Anti-Bleed Feature

Description:
FIELD OF THE INVENTION  
      The present invention relates generally to semiconductor devices, and more particularly to a device for controlling a bleeding of resin on a substrate.  
     BACKGROUND OF THE INVENTION  
      In the semiconductor processing industry, various processes are performed on various substrates in order to form a multitude of various semiconductive components. For example, two or more differing components may be bonded to one another for purposes of electrical interconnection, heat dissipation, or to provide protection from environmental factors. In flip-chip semiconductor processing, for example, a conventional electronic device, such as the device  10  illustrated in  FIG. 1A , comprises a flip-chip  12  that is bonded to a substrate  14 , wherein the bond generally defines electrical connections (not shown) between the substrate and the flip-chip. Typically, the flip chip  12  is bonded to the substrate  14  via a plurality of solder balls, wherein the solder balls are melted in order to electrically connect and bond the substrate and the flip-chip. As illustrated in  FIG. 1B , in order to dissipate heat from the bonded flip-chip  12  (shown in phantom) and/or protect the bonded flip-chip from various environmental factors, such as dust or physical contact with other external devices (not shown), a protective cap  16  is typically bonded over a flip-chip region  18 , wherein the cap is bonded to the substrate via an adhesive  20 .  
      A typical adhesive  20  is comprised of a temperature-curable bonding agent suspended in a fluid-like resin, wherein the bonding agent is typically cured by an application of heat thereto. Such a curing process generally forms the bond between the cap  16  and the substrate  14 , however, the resin tends to bleed onto surrounding regions  22  of the substrate, as illustrated in  FIGS. 1A and 1B . Such a bleeding of the resin has a potential to contaminate the substrate  14 , the flip-chip  12 , and/or various other components  24  associated with the substrate. For example, the resin that is bled onto other components  24  may form an electrically-insulative layer (not shown) over the components, wherein future electrical connections to the components may be affected by the coating of resin thereover.  
      Furthermore, in an instance wherein the adhesive  20  comprises an electrically-conductive bonding agent (e.g., wherein an electrical connection between the cap  16  and the substrate  14  is desired), minute portions of the electrically-conductive bonding agent can also bleed or leach out with the resin before, during, or after the curing of the adhesive. Such a bleeding of the electrically-conductive bonding agent may provide further disadvantageous results in the finished device  10 , such as an electrical shorting of various circuits, capacitance bleeding, etc. For example, a bleeding of the resin over a side  26  of the substrate provides the potential for a short-circuiting of one or more connectors  28  associated with the device  10 . The connectors  28 , for example, may further comprise bonding pads (not shown), wherein the bonding pads are highly susceptible to resin-bleed contamination.  
      Conventionally, undesirable affects from resin bleed are minimized by providing a large bleed area on the substrate for the resin to bleed onto, wherein no electrical components are associated with the bleed area. However, as real estate on substrates becomes more and more valuable due to ever decreasing sizes of associated electronic devices, providing such a large area for resin bleed becomes less practical. Additionally, conventional devices used to prevent the resin bleed typically require additional processing steps, therein adding cost and/or valuable manufacturing time. Accordingly, a need exists in the art for an economical device for minimizing the negative impact of resin bleed.  
     SUMMARY OF THE INVENTION  
      The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the invention. It is intended to neither identify key or critical elements of the invention nor delineate the scope of the invention. Its purpose is to present some concepts of the invention in a simplified form as a prelude to the more detailed description that is presented later.  
      The present invention is generally directed toward a resin-bleed control device and method for controlling a bleed of resin on a substrate, wherein conventional processing for forming other electronic devices on the substrate can further incorporate a formation of the resin-bleed control device. In accordance with one exemplary aspect of the invention, the device comprises a substrate having a surface, wherein an interior region, a peripheral region, and an exterior region of the surface are generally defined on the surface of the substrate. One or more electrical devices, such as a flip chip, are further associated with the interior region of the substrate. In order to provide heat dissipation for the one or more electrical devices and/or protect the one or more electrical devices from an external environment, a cap is bonded to the substrate. In one example, the interior region is generally isolated from the external environment by the cap.  
      In accordance with one aspect of the invention, the cap is bonded to one or more of the substrate and one or more electrical devices via an adhesive, wherein the adhesive is comprised of a plurality of components. For example, the adhesive generally resides on the surface of the substrate in the peripheral region, wherein the cap is further placed on the adhesive for bonding to the substrate. A first barrier is further formed over the surface of the substrate, wherein the first barrier generally resides between the adhesive and the exterior region of the surface of the substrate, wherein the first barrier generally prevents one or more of the plurality of components of the adhesive, such as a resin, from bleeding substantially onto the exterior region of the surface of the substrate.  
      A porosity of the first barrier, for example, is less than a porosity of one or more of the interior region and the exterior region of the surface of the substrate, wherein the porosity of the first barrier generally provides a capillary action to prevent the resin from bleeding onto the exterior region of the surface of the substrate. For example, the first barrier is comprised of a metal, wherein the porosity of the metal is substantially less than the porosity of the substrate, and wherein the resin flow is generally confined to a surface of the metal after reaching the first barrier. The first barrier, for example, is further formed on the surface of the substrate during a formation of other components associated with the device, such as a formation of bonding pads or electrical interconnects. Thus, the formation of the first barrier can be performed in a manner that does not require additional steps in processing the device, and can also increase reliability of the device without substantially increasing manufacturing costs. According to another aspect of the invention, the first barrier is formed substantially close to a side of the device, wherein minimal surface real estate is utilized to prevent bleeding of resin onto the exterior region of the substrate.  
      In accordance with another exemplary aspect of the invention, the device comprises a second barrier formed on the surface of the substrate, wherein the second barrier is formed within one or more of the interior region and peripheral region. Consequently, the flow of resin is generally confined between the first barrier and the second barrier. The second barrier, for example, is further formed generally concurrently to the formation of the first barrier.  
      To the accomplishment of the foregoing and related ends, the invention comprises the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative embodiments of the invention. These embodiments are indicative, however, of a few of the various ways in which the principles of the invention may be employed. Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1A  is a prior art plan view of a typical substrate illustrating a bleed of resin onto the substrate.  
       FIG. 1B  is a prior art perspective view of a conventional substrate having a cap adhered thereto.  
       FIG. 2A  is a plan view of an exemplary device for preventing resin bleed in accordance with one exemplary aspect of the present invention.  
       FIG. 2B  is a partial cross-sectional view of the device of  FIG. 2A  in accordance with another exemplary aspect of the invention.  
       FIG. 3  is an exploded plan view of a portion of the device of  FIG. 2A  in accordance with yet another exemplary aspect of the present invention.  
       FIG. 4  is a plan view of another exemplary device for preventing resin bleed according to still another exemplary aspect of the present invention.  
       FIG. 5  is a block diagram of an exemplary method for controlling a resin-bleed on a substrate in accordance with another aspect of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      The present invention is directed towards a device for controlling a bleed of resin on a substrate. More particularly, the present invention provides a cost-effective solution for minimizing resin bleed into one or more regions of the substrate. Accordingly, the present invention will now be described with reference to the drawings, wherein like reference numerals are used to refer to like elements throughout. It should be understood that the description of these aspects are merely illustrative and that they should not be taken in a limiting sense. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be evident to one skilled in the art, however, that the present invention may be practiced without these specific details.  
      Referring now to the figures,  FIG. 2A  illustrates an exemplary electronic device  100 , such as an integrated circuit package  102 , in accordance with one aspect of the present invention. The device  100 , for example, comprises a substrate  105 , such as a ceramic or semiconductive substrate or carrier, wherein a surface  107  of the substrate is generally defined. An interior region  108 , a peripheral region  110 , and an exterior region  112  (e.g., a side surface  113 ) of the surface  107  are further defined, wherein an integrated circuit  115  generally resides within the interior region. The integrated circuit  115 , for example, comprises a flip-chip  117  that is electrically connected to one or more contacts (not shown) associated with the substrate  105 . The one or more contacts associated with the substrate  105 , for example, are operable to electrically connect the integrated circuit  115  to various other devices (not shown), as will be discussed hereafter. The device  100  may further comprise various other electrical components  118 , such as a plurality of capacitors  119 , wherein the other electrical components further reside within the interior region  108  of the substrate. The other electrical components  118 , for example, are further electrically connected to one or more of the integrated circuit  115  and other devices (not shown) associated with the device  100 .  
       FIG. 2B  illustrates a partial cross-section of the device  100  of  FIG. 2A , wherein a plurality of connectors  120  are illustrated across a bottom surface  121  of the substrate  105 . The plurality of connectors  120 , for example, may comprise pads, sockets or pins, wherein the plurality of connectors are electrically connected to the integrated circuit  115  and various other components  118 , wherein other devices (not shown) may be further electrically connected to the device  100 .  FIG. 2B  further illustrates a cap  122  that generally resides over the interior region  108  of the substrate  105 . The cap  122 , for example, generally surrounds the integrated circuit  115 , and is operable to protect the integrated circuit and/or other electrical components  118  (e.g., the plurality of capacitors  119 ) that generally reside in the interior region  108  from an external environment  123 . For example, the cap  122  generally prevents dust, moisture, or the like, from entering an interior space  124  that is generally defined between the cap  122  and the interior region  108  of the surface  107  of the substrate  105 .  
      The cap  122 , for example, is comprised of a plastic, ceramic, metal, such as copper or aluminum, or a composite material such as copper tungsten or aluminum nitride. The cap  122 , in one example, contacts the integrated circuit  115 , wherein the cap is operable to generally dissipate heat associated with the integrated circuit  115 . The cap  122  may be further associated with a heat sink (not shown), wherein the heat sink is further operable to conduct heat from the integrated circuit  115  via the cap. The cap  122 , in another example, further provides protection to the integrated circuit  115  from contact with physical sources associated with the external environment  123  (e.g., the cap generally prevents objects associated with the external environment from contacting the integrated circuit  115 ). Alternatively, the cap  122  is operable to provide electrical shielding of the integrated circuit  115  from electrical sources associated with the external environment  123 , or an electrical ground to the substrate  105 . In still another alternative, the cap  122  comprises any structure, such as a spacer (not shown), or the like, wherein the cap provides a physical separation of the integrated circuit  115  from other physical sources associated with the external environment  123 .  
      In accordance with one exemplary aspect of the invention, the cap  122  is generally affixed to the surface  107  of the substrate  105  by an adhesive  125 . For example, as illustrated again in  FIG. 2A , the adhesive  125  is applied to the peripheral region  110  of the surface  107  of the substrate  105 , and the cap  122  is subsequently placed over the adhesive, such that the cap is substantially adhered to the substrate via the adhesive. In another example, the adhesive  125  is further applied to the integrated circuit  115 , as illustrated in  FIG. 2B , wherein the adhesive generally provides an advantageous thermal conductivity between the integrated circuit and the cap  122  for purposes of heat dissipation. The adhesive  125 , for example, is generally comprised of a plurality of components, such as a metal in one or more binders, wherein the adhesive is curable by an application of heat thereto (e.g., at a temperature of approximately 150° C.), and wherein the cap  122  is generally bonded to the substrate  105  upon curing of the adhesive.  
      Again referring to  FIG. 2A , the adhesive  125 , for example, can comprise a resin  130  that will leech or bleed onto the surface  107  of the substrate  105  prior to curing of the adhesive. For example, over time, the resin  130  will bleed from the adhesive  125  and onto the surface  107  of the substrate  105 . Furthermore, the bleed of resin  130  can carry along one or more of the plurality of components of the adhesive  125 , such as the trace amounts of the metal, wherein the trace amounts of metal is further bled onto the surface  107 . Such a bleed of resin  130 , with or without the trace amounts of metal, can have deleterious effects on the device  100  if the bleed of resin extends onto the bottom surface  121  of the substrate and onto the plurality of contacts  120 .  
      Therefore, in accordance with the present invention, as illustrated in  FIG. 2A , a first barrier  135  is formed over the surface  107  of the substrate  105  within the peripheral region  110  in order to control the bleed of resin  130 . The first barrier  135 , for example, generally surrounds the interior region  108  of the substrate  105 , and further generally isolates the interior region from the exterior region  112  of the substrate. According to another example, the first barrier  135  is formed substantially close to the side surface  113  of the substrate, wherein the first barrier occupies a minimal amount of surface area of the substrate. Accordingly, the first barrier  135  is operable to generally control the flow of resin  130 , such that the resin is generally prevented from flowing onto the surface  107  of the substrate  105  in the exterior region  112  thereof.  
      According to another exemplary aspect of the invention, the first barrier  135  has a surface  140  that has a porosity that is less than a porosity of the surface  107  of the substrate  105  in one or more of the interior region  108  and the exterior region  112 . For example, the first barrier  135  is comprised of a material having a porosity that is less than a porosity of the substrate  105 . The first barrier  135 , for example, is comprised of one or more metals such as gold, silver, nickel, copper, and titanium, wherein the one or more metals are plated (e.g., electroplated) on the surface  107  of the substrate  105 . Alternatively, the first barrier  135  is formed on the surface  107  of the substrate  105  by silk-screening. The first barrier  135 , for example, is formed on the substrate  105  in conjunction with a formation of other metal features (not shown) on the substrate, such as during formation of bonding pads or wiring lines associated with the electrical connection of the integrated circuit  115  to the substrate  105 . According to one example, the first barrier  135  comprises silver or gold that is electroplated to a thickness of less than about one micron. Alternatively, the first barrier  135  is comprised of any material that has a porosity that is less than the porosity of the surface  107  of the substrate  105 , and any thickness of the first barrier is contemplated as falling within the scope of the present invention.  
      As stated above, the surface  140  of the first barrier  135  is less porous than the surface  107  of the substrate  105 . Such a porosity of the surface  140  of the first barrier  135  generally provides a channeling of the bleed, or flow, of resin  130  along the smoother, less porous surface  140  of the first barrier, wherein the resin flow generally follows a path of least resistance. Furthermore, the surface  140  of the first barrier  135  is operable to provide a capillary action, wherein the resin  130  is generally pulled toward the first barrier. Accordingly, the bleed of resin  130  is controlled by the first barrier  135 , wherein the surface  140  of the first barrier provides less resistance to flow than the surface  107  of the substrate  105 .  FIG. 3  illustrates an exploded view  145  of the device  100  of  FIG. 2A , wherein the resin bleed  130  flows from the adhesive  125  onto the surface  107  of the substrate  105 . Upon encountering the first barrier  135 , the resin  130  is generally channeled along the surface  140  of the first barrier. It is believed that the flow of resin  130  is generally controlled by capillary and/or other forces associated with the surface  140  of the first barrier  135 , since the surface  140  is less porous than the surface  107  of the substrate  105 .  
      Again, since the surface  107  of the substrate  105  in the external region  112  has a greater porosity than the surface  140  of the first barrier  135 , the resin  130  is generally deterred from bleeding into the external region after bleeding onto the first barrier. Therefore, the bleed of resin  130  is controlled still further, wherein the resin is generally prevented from bleeding into the external region  112  and bottom surface  121  of the substrate  105 , thus preventing a bleed of resin onto the plurality of connectors  120 . Such a control of the flow or bleed of resin  130 , for example, is highly advantageous if any electrically conductive components of the adhesive  125  are also carried or bled with the resin during its flow. Consequently, since the flow of resin  130  is generally controlled by the first barrier, electrically conductive or insulative components associated with the adhesive  125  are substantially prevented from contacting the connectors  120 , and thus providing a more reliable device  100 .  
      In accordance with one example, the first barrier  135  comprises a ring  141  formed on the surface  107  of the substrate  105  within the peripheral region  110 , wherein the first barrier generally surrounds the interior region  108 , thus limiting the resin bleed  130  to within the interior region  108 . Alternatively, the first barrier  135  comprises a plurality of barriers (not shown) formed in the peripheral region  110  of the surface  107  of the substrate  105 , wherein each barrier controls a particular portion of resin bleed  130  from bleeding into the exterior region  112 . Accordingly, the present invention contemplates any configuration of the first barrier  135 , wherein the first barrier generally controls the resin bleed  130  from flowing into the exterior region  112  of the substrate  105 .  
      In accordance with another exemplary aspect of the present invention,  FIG. 4  illustrates another exemplary device  150 , wherein a second barrier  155  is formed over the surface  107  of the substrate  105 . The second barrier  155 , for example, can be formed in a manner similar to the formation of the first barrier  135 , and may be comprised of a similar material (e.g., a metal). Again, like the first barrier  135  discussed above, the second barrier  155  has a surface  157  that has a porosity that is less than the porosity of the surface  107  of the substrate  105 . Consequently, the second barrier  155  can further control the bleed of resin  130 . For example, the second barrier  155  is formed on the surface  107  in one or more the interior region  108  and peripheral region  110  of the substrate  105 , wherein the bleed of resin  130  is generally confined between the first barrier  135  and the second barrier  155 . It should be noted that further barriers (not shown) can be formed on the substrate  105  in accordance with the present invention (e.g., between the integrated circuit  115  and the various other electrical components  118 ), wherein the further barriers provide a further control of resin bleed on the substrate, and such further barriers are contemplated as falling within the scope of the present invention.  
      According to still another exemplary aspect of the present invention,  FIG. 5  is a schematic block diagram illustrating an exemplary method  200  for controlling a bleed of resin on a substrate. While exemplary methods are illustrated and described herein as a series of acts or events, it will be appreciated that the present invention is not limited by the illustrated ordering of such acts or events, as some steps may occur in different orders and/or concurrently with other steps apart from that shown and described herein, in accordance with the invention. In addition, not all illustrated steps may be required to implement a methodology in accordance with the present invention. Moreover, it will be appreciated that the methods may be implemented in association with the systems illustrated and described herein as well as in association with other systems not illustrated.  
      As illustrated in  FIG. 5 , the method  200  begins with act  205 , wherein a substrate, such as a ceramic substrate, is provided, wherein the substrate has a first surface having a first porosity associated therewith. In accordance with one exemplary aspect of the invention, one or more regions of the first surface are generally defined, wherein an adhesive is operable to be applied to the first surface within one or more regions in order to secure a cap thereto. The adhesive, for example, is comprised of a suspension of metal in a resin, wherein the adhesive is operable to be cured by an application of heat thereto. Furthermore, the resin is operable to bleed or flow from the adhesive onto the first surface  
      In act  210 , a first barrier is formed over the first surface of the substrate, wherein the first barrier generally defines a second surface having a second porosity. In accordance with the present invention, the second porosity of the first barrier is less than the first porosity of the substrate. The first barrier, for example, is formed via electroplating a metal onto the first surface of the substrate, wherein the first barrier generally surrounds the one or more regions of the first surface. Since the second porosity of the first barrier is less than the first porosity of the substrate, the second surface is operable to generally provide a capillary effect for any resin that may bleed onto the second surface. Such a capillary action further generally prevents the bleed of resin outside of the one or more regions, therein generally controlling the bleed of resin.  
      Furthermore, since the resin will follow the path of least resistance upon bleeding of the adhesive (e.g., prior to curing of the adhesive), the resin will flow via capillary action on the second surface, but will not substantially flow from the second surface back onto the first surface, because the second porosity of the first barrier is less than the first porosity of the substrate.  
      Although the invention has been shown and described with respect to a certain aspect or various aspects, it is obvious that equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. In particular regard to the various functions performed by the above described components (assemblies, devices, circuits, etc.), the terms (including a reference to a “means”) used to describe such components are intended to correspond, unless otherwise indicated, to any component which performs the specified function of the described component (i.e., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function in the herein illustrated exemplary embodiments of the invention. In addition, while a particular feature of the invention may have been disclosed with respect to only one of several aspects of the invention, such feature may be combined with one or more other features of the other aspects as may be desired and advantageous for any given or particular application. Furthermore, to the extent that the term “includes” is used in either the detailed description or the claims, such term is intended to be inclusive in a manner similar to the term “comprising.”