U.S. patent application number 10/862735 was filed with the patent office on 2004-11-04 for microelectronic adaptors, assemblies and methods.
This patent application is currently assigned to Tessera, Inc.. Invention is credited to Damberg, Philip.
Application Number | 20040217461 10/862735 |
Document ID | / |
Family ID | 31190733 |
Filed Date | 2004-11-04 |
United States Patent
Application |
20040217461 |
Kind Code |
A1 |
Damberg, Philip |
November 4, 2004 |
Microelectronic adaptors, assemblies and methods
Abstract
A first microelectronic element such as a semiconductor chip is
mounted to a circuit board using an adaptor which has a region
extending beneath the first microelectronic element and an
additional region which may be folded over the first
microelectronic element or which may project laterally from the
first microelectronic element. The adaptor includes a functional
element in the additional region, such as a further microelectronic
element or an array of terminals for mounting another element. The
assembly provides the benefits of a stacked chip assembly or other
mustachio module, but can be made without the need for a special
prepackaged stacked chip assembly. The adaptor can be configured so
that it does not materially increase the height of the first
microelectronic element above the circuit board.
Inventors: |
Damberg, Philip; (Cupertino,
CA) |
Correspondence
Address: |
LERNER DAVID, LITENBERG, KRUMHOLZ & MENTLIK
600 SOUTH AVENUE WEST
WESTFIELD
NJ
07090
US
|
Assignee: |
Tessera, Inc.
San Jose
CA
|
Family ID: |
31190733 |
Appl. No.: |
10/862735 |
Filed: |
June 7, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10862735 |
Jun 7, 2004 |
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10236442 |
Sep 6, 2002 |
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6765288 |
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60401391 |
Aug 5, 2002 |
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Current U.S.
Class: |
257/698 ;
257/E23.172; 257/E23.177; 257/E25.011; 257/E25.013 |
Current CPC
Class: |
H01L 2224/05573
20130101; H05K 1/189 20130101; H05K 3/326 20130101; H01L 2224/05571
20130101; H01L 2924/00014 20130101; H05K 2201/049 20130101; H01L
2225/06517 20130101; H05K 1/141 20130101; H01L 25/0652 20130101;
H01L 23/5387 20130101; H01L 2225/06579 20130101; H05K 2201/0394
20130101; H05K 2201/0397 20130101; H01L 25/0657 20130101; H01L
2224/16225 20130101; H01L 23/5385 20130101; H01L 2924/00014
20130101; H05K 3/363 20130101; H01L 2224/05599 20130101 |
Class at
Publication: |
257/698 |
International
Class: |
H01L 023/04 |
Claims
1. An adaptor for use with a first microelectronic package having a
bottom surface, a top surface and an array of connection elements
projecting downwardly beyond the bottom surface of said package,
the adaptor comprising: a substrate having a first socket region
with an inner surface and an outer surface, an array of socket
openings extending through the substrate in said socket region,
said socket openings being disposed in an array corresponding to
the arrangement of connection elements on the microelectronic
element, the adaptor further comprising a set of socket contacts
aligned with at least some of said socket openings, said socket
contacts and socket openings being arranged so that the package can
be engaged with the adaptor with the bottom surface of the package
confronting the inner surface of the substrate in said socket
region and with the connection elements of the package engaged with
the socket contacts and projecting through said socket openings
beyond the outer surface of the substrate, the adaptor further
including one or more functional elements electrically connected to
at least some of said socket contacts.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation of U.S. patent
application Ser. No. 10/236,442, filed Sep. 6, 2002, which
application claims benefit of U.S. Provisional Patent Application
Ser. No. 60/401,391, filed Aug. 5, 2002, the disclosures of which
are hereby incorporated by reference herein.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to microelectronic assemblies
and to components and methods used for making the same.
[0003] Microelectronic elements such as semiconductor chips
ordinarily are mounted on circuit panels such as circuit boards.
For example, a packaged semiconductor chip may have an array of
bonding contacts on a bottom surface of the package. Such a package
can be mounted to a corresponding array of bonding contacts exposed
at a top surface of a circuit board by placing the package on the
circuit board with the bottom surface of the package facing
downwardly and confronting the top surface of the circuit board, so
that each bonding contact on the package is aligned with a
corresponding bonding contact on the circuit board. Masses of a
conductive bonding material, typically in the form of solder balls,
are provided between the bonding contacts of the package and the
bonding contacts of the circuit board. In typical surface-mounting
techniques, solder balls are placed on the bonding contacts of the
package before the package is applied to the circuit board.
[0004] Ordinarily, numerous microelectronic elements are mounted
side-by-side on the circuit board and interconnected to one another
by electrically conductive traces connecting the various bonding
contacts. Using this conventional approach, however, the circuit
board must have an area at least equal to the aggregate area of all
of the microelectronic elements. Moreover, the circuit board must
have all of the traces needed to make all of the interconnections
between microelectronic elements. In some cases, the circuit board
must include many layers of traces to accommodate the required
interconnections. This materially increases the cost of the circuit
board. Typically, each layer extends throughout the entire area of
the circuit board. Stated another way, the number of layers in the
entire circuit board is determined by the number of layers required
in the area of the circuit board having the most complex, densely
packed interconnections. For example, if a particular circuit
requires six layers of traces in one small region but only requires
four layers in the remainder of the circuit board, the entire
circuit board must be fabricated as a six-layer structure.
[0005] These difficulties can be alleviated to some degree by
connecting related microelectronic elements to one another using an
additional circuit panel so as to form a sub-circuit or module
which, in turn, is mounted to the main circuit board. The main
circuit board need not include the interconnections made by the
circuit panel of the module. It is possible to make such a module
in a "stacked" configuration, so that some of the chips or other
microelectronic elements in the module are disposed on top of other
chips or microelectronic elements in the same module. Thus, the
module as a whole can be mounted in an area of the main circuit
board less than the aggregate area of the individual
microelectronic elements in the module. However, the additional
circuit panel and the additional layer of interconnections between
this circuit panel and the main circuit board consume additional
space. In particular, the additional circuit panel and additional
layer of interconnections between the additional circuit panel and
the main circuit panel add to the height of the module, i.e., the
distance by which the module projects above the top surface of the
main circuit board. This is particularly significant where the
module is provided in a stacked configuration and where low height
is essential, as, for example, in assemblies intended for use in
miniaturized cellular telephones and other devices to be worn or
carried by the user. Such a module may also require a complicated
socket or connector between the module circuit panel and the
circuit board.
[0006] The additional space consumed by mounting prepackaged
semiconductor chips on a separate module circuit panel can be saved
by integrating the circuit panel of the module with a part of the
package itself, commonly referred to as a package substrate. For
example, several bare or unpackaged semiconductor chips can be
connected to a common substrate during the chip packaging
operation. Packages of this nature can also be made in a stacked
arrangement. Such multi-chip packages can include some or all of
the interconnections among the various chips in the package and can
provide a very compact assembly. The main circuit board can be
simpler than that which would be required to mount individual
packaged chips in the same circuit. However, this approach requires
unique packages for each combination of chips to be included in the
package. For example, in the cellular telephone industry, it is a
common practice to use the same field programmable gate array
("FPGA") or application specific integrated circuit ("ASIC") with
different combinations of static random access memory ("SRAM") and
flash memory so as to provide different features in different
cellular telephones. This increases the costs associated with
producing, handling and stocking the various packages.
SUMMARY OF THE INVENTION
[0007] One aspect of the invention provides a circuit panel
assembly which includes a circuit panel such as a printed circuit
board having a top surface and a first microelectronic element
disposed on the circuit panel, the first microelectronic element
having a bottom surface overlying the top surface of said circuit
panel and defining a gap therebetween. The assembly according to
this aspect of the invention also includes an adaptor having a
substrate including a first region. The substrate has
oppositely-directed inner and outer surfaces in said first region.
The first region of the substrate first extends at least partially
in the gap between said bottom surface of said first
microelectronic element and said top surface of said circuit panel
with said inner surface facing upwardly toward the bottom surface
of the first microelectronic element. The adaptor also includes a
functional element as, for example, an array of terminals for
connection to a further element disposed on the substrate outside
of the first region. For example, the functional element of the
adaptor may be disposed in an additional region which may be folded
over the top of the first microelectronic element. Where the
functional element includes terminals, one or more further
microelectronic elements can be disposed above the first
microelectronic element and connected to the terminals, to provide
a stacked arrangement. In other variants, the additional region may
project laterally away from the first microelectronic element.
[0008] The adaptor may have apertures in the first region, and
socket contacts aligned with at least some of these apertures.
Connection elements such as solder balls or surface-mountable leads
on the first microelectronic element may extend through the
apertures, and at least some of the connection elements may contact
the socket contacts of the adaptor.
[0009] The assembly can be made using the techniques normally used
to handle and secure packaged chips as, for example, placement,
soldering and reflow; there is no need to prepare special stacked
chip subassemblies in a chip packaging plant. Nonetheless, the
preferred embodiments of the assembly can provide the benefits
normally achieved by prepackaged stacked chip assemblies, such as
compactness and simplified wiring layouts in the circuit board. In
this arrangement, the functional element of the adaptor is
connected to the first microelectronic element, to the contact pads
of the circuit board, or both, by the socket contacts of the
adaptor. However, because the connection elements extend through
the adaptor to the circuit board, the presence of the adaptor need
not substantially increase the height of the first microelectronic
element above the circuit board.
[0010] In another arrangement, the adaptor has conductive
attachments in the first region as, for example, pads overlying
apertures in the adaptor substrate rather than the socket contacts
discussed above. The functional element is electrically connected
to at least some of these conductive attachments. The first
microelectronic element is connected to the conductive attachments
by internal connection elements such as thin solder lands, whereas
mounting elements as, for example, solder balls, extend between
said first conductive attachments and said contact pads. In this
arrangement as well, the mounting and connection elements most
preferably are arranged to minimize the height of the first
microelectronic element above the circuit board. Most preferably,
the bottom surface of the first microelectronic element is disposed
at a height above the top surface of said circuit panel less than
the sum of the height of the internal connection elements, the
height of the mounting elements and the thickness of first
connection region of the adaptor. For example, the mounting
elements may extend at least partially within apertures within the
adaptor, so that the height of the mounting elements is at least
partially concealed within the thickness of the adaptor substrate.
Here again, the assembly can be made using techniques similar to
those used in mounting packaged chips to a circuit board as, for
example, surface mounting techniques, so that there is no need for
special prepackaged stacked chip assemblies.
[0011] Further aspects of the invention provide adaptors suitable
for use in the aforementioned assemblies and assembly methods.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a diagrammatic bottom plan view of a component in
accordance with one embodiment of the invention.
[0013] FIG. 2 is a diagrammatic sectional view taken along line 2-2
showing the component of FIG. 1 in conjunction with a
microelectronic element during one stage of manufacture.
[0014] FIG. 3 is a view similar to FIG. 2 showing the component and
element of FIG. 2 during a later stage of manufacture.
[0015] FIG. 4 is a further diagrammatic sectional elevational view
showing the component and element of FIGS. 1-3 in an assembly with
additional elements.
[0016] FIG. 5 is a detailed view on an enlarged scale of the area
indicated in FIG. 4.
[0017] FIG. 6 is a view similar to FIG. 5 but depicting a component
according to a further embodiment of the invention.
[0018] FIG. 7 is a diagrammatic, partially sectional view depicting
an assembly in accordance with a further embodiment of the
invention.
[0019] FIG. 8 is a view similar to FIG. 7 but depicting an assembly
according to yet another embodiment of the invention.
[0020] FIG. 9 is a diagrammatic top plan view of a component in
accordance with yet another embodiment of the invention.
[0021] FIG. 10 is a diagrammatic, partially sectional elevational
view of a subassembly made using the component of FIG. 9.
[0022] FIG. 11 is a partially sectional, elevational view of an
assembly in accordance with yet another embodiment of the
invention.
[0023] FIG. 12 is a view similar to FIG. 11 but depicting an
assembly according to a further embodiment of the invention.
[0024] FIG. 13 is a diagrammatic sectional view on an enlarged
scale of the area indicated in FIG. 12.
[0025] FIGS. 14 and 15 are further diagrammatic sectional
elevational views depicting assemblies in accordance with further
embodiments of the invention.
DETAILED DESCRIPTION
[0026] An adaptor in accordance with one embodiment of the
invention includes a sheetlike, flexible substrate 20 having an
inner surface 22 and an oppositely-directed, outer surface 24. As
used in this disclosure, the term "sheetlike" refers to an element
which has thickness substantially less than its length and width.
Substrate 20 may be formed from essentially any material used in
formation of flexible circuits as, for example, unreinforced or
reinforced polyimides or BT resin. Most typically, the substrate is
about 25-75 microns thick. Other materials and thicknesses may be
employed. As discussed below, during fabrication of an assembly
incorporating the adaptor in accordance with this embodiment, the
substrate will be flexed in only one region, and, accordingly, only
that region needs to be flexible in this embodiment. Thus, other
regions of the substrate may be substantially rigid.
[0027] Substrate 20, as seen in plan view in FIG. 1, is generally
in the form of an elongated strip and has a first socket region 26
adjacent the end of the strip towards the left as seen in FIG. 1,
and has an additional or attachment region 28 adjacent the opposite
end of the strip. The substrate has an array of apertures 30
extending through it, from the inner surface 22 to the outer
surface 24 in the first socket region 26.
[0028] The adaptor further includes a set of first socket contacts
34 formed from one or more electrically conductive materials,
typically metals. Each first socket contact 32 is aligned with one
of the apertures 30. Each first socket contact is adapted to engage
a solder ball advanced through the corresponding aperture 30 and is
also adapted to allow the solder ball to project through the
aperture and through the contact itself. These contacts may be
generally similar to the contacts disclosed in U.S. Pat. Nos.
5,632,631; 5,980,270; 5,802,699; 5,615,824; and 6,200,143 the
disclosures of which are hereby incorporated by reference herein.
In the particular embodiment depicted, each socket contact 32 is
generally in accordance with certain preferred embodiments shown in
the aforementioned '631, '824 and '270 patents; each socket contact
includes a main structure 34 having a hole corresponding to the
aperture 30 and four tabs 36 which project inwardly, partially
across the hole and partially across the aperture 30. As disclosed
in certain of the aforementioned patents, the socket contacts may
incorporate features such as asperities and hard metal elements to
facilitate engagement with the solder balls and may have areas that
are not wettable by the solder or other joining material, that is
to be used with the socket contacts. Socket contacts 34 in the
embodiment of FIGS. 1 and 2 are disposed on the outer or bottom
surface 24 of substrate 20.
[0029] The adaptor further includes a layer of an adhesive 38
overlying the inner surface 22 of substrate 20 in attachment area
28. Adhesive 38 may be, for example, an epoxy or a so-called "dry
pad" adhesive arranged to remain solid until raised to an elevated
temperature and then promptly form a bond to a mating surface.
[0030] The adaptor also includes an additional functional element
in the form of an array of terminals 40 disposed on the outer
surface 24 of the substrate in the attachment region 28. As used in
this disclosure, the term "functional element" refers to an element
which itself can perform an electrical function as, for example, a
passive component such as a resistor, capacitor or inductor, a unit
incorporating several passive devices, commonly referred to as a
"passive chip", or an active semiconductor component such as a
semiconductor chip including numerous active devices with or
without passive devices, and also refers to an element which can be
used to make connections to an additional electronic device or
element as, for example, an array of terminals.
[0031] At least some of terminals 40 are connected to at least some
of the first socket contacts 32 by traces 42 extending along the
substrate 20. Some of the traces are omitted for clarity of
illustration in FIG. 1. Traces 42 and terminals 40 may be formed
from conventional materials used in flexible circuits, as, for
example, copper and copper-based alloys, with a thin layer of gold
or other non-reactive, readily-solderable metal on the exposed
surfaces of terminals 40. A solder mask layer (not shown) desirably
overlies the outer surface 24 of the adaptor and also covers traces
24. The solder mask layer has openings aligned with terminals 40 so
that the terminals remain exposed at the outer surface 24 of the
substrate. As used in this disclosure, a terminal or other
conductive feature is regarded as "exposed at" a surface of a
dielectric element where the terminal is arranged so that all or
part of the conductive feature can be seen by looking at such
surface. In the particular embodiment illustrated, terminals 40
project slightly from outer surface 24, but this is not essential;
the terminals 40 may be recessed within apertures extending to the
outer surface, or even provided on the inner surface and aligned
with apertures extending through the dielectric to the outer
surface.
[0032] In an assembly method according to a further embodiment of
the invention, the adaptor is assembled with a first
microelectronic element 44. Microelectronic element 44 may be a
"bare" semiconductor chip or, preferably, a packaged semiconductor
chip incorporating the active semiconductor elements or die 46 in a
protective package 48. The first microelectronic element as a whole
has a bottom surface 50, a top surface 52 and edges 54 and 56
extending between the top and bottom surfaces. The microelectronic
element further includes an array of bonding contacts 58 exposed at
the bottom surface 50 of the element. For example, where the first
microelectronic element is a semiconductor chip in a ball grid
array package, the bottom surface 50 may be defined by a package
substrate 60 and bonding contacts 58 may be provided as conductive
elements on this substrate. The bonding contacts are electrically
connected to the active semiconductor chip 46 by internal leads
(not shown). The edges and top surface of the microelectronic
element may be defined by an encapsulant covering the active
semiconductor or die 46. Such packages can be made with numerous
different internal configurations. For example, the active element
or die 46 may be mounted "face-up" so that the contacts of the
active semiconductor element or die 46 face upwardly, away from the
package substrate 60 or, alternatively, "face-down" so that the
active die contacts face toward the package substrate. Optionally,
microelectronic element 44 may have bonding contacts 58 which are
moveable with respect to the active semiconductor element or die
46.
[0033] The microelectronic element is provided with an array of
connecting elements in the form of solder balls 62. The solder
balls are attached to bonding pads 58 and project downwardly from
the bottom surface 50 of the microelectronic element. The solder
balls may be applied by conventional processes used in
surface-mounting technology. For example, the solder balls may be
bonded to the bonding contacts 58 by reflowing or melting the
solder balls when the balls are applied. The microelectronic
element 44, with connecting elements or solder balls 62, is
arranged over the inner surface 22 of the adaptor substrate in the
first socket region 26, so that the bonding contacts 58 and
connecting elements or solder balls 62 are aligned with the
apertures 30 in the adaptor substrate and, hence, with the socket
contacts 32. The microelectronic element and adaptor are then urged
toward one another, as depicted in FIG. 3. For example, the outer
surface 24 of the adaptor substrate may be supported by a resilient
element or by a temporary fixture 64 having openings 66 larger than
the solder balls 62 arranged in an array corresponding to the array
of apertures 30 and socket contacts 32. The top or rear surface 52
of the microelectronic element 44 may be engaged by another fixture
68. In this manner, the microelectronic element is advanced toward
the adaptor substrate so that the bottom surface 50 of the
microelectronic element approaches or engages the top surface 22 of
the adaptor substrate. The connecting elements or solder balls pass
through the apertures 30 in the substrate and engage the socket
contacts 32. As best seen in FIG. 5, at this stage of the process,
the tabs 34 of the socket contacts desirably bend downwardly as the
solder balls 62 pass through the socket contacts.
[0034] In the next stage of the process, substrate 20 is folded to
the configuration depicted in FIG. 4. In this configuration, the
substrate extends outwardly beyond one edge 54 of microelectronic
element 44 and upwardly along that edge. The attachment area 28 of
the substrate overlies the top or rear surface 52 of the first
microelectronic element 44. The inner surface 22 in the attachment
region faces downwardly and confronts the top surface of the
microelectronic element, whereas the outer surface 24 in the
attachment region faces upwardly. Thus, terminals 40, which are
exposed at the outer surface 24, are accessible from the top of the
first microelectronic element. The inner surface 22 is secured to
the top surface 52 of the microelectronic element by adhesive 38.
The substrate may be folded to this configuration simply by bending
the substrate around the edge of the microelectronic element or by
bending the substrate around a temporary tool or fixture (not
shown).
[0035] The microelectronic element and adaptor may be handled and
placed onto a circuit board 70 or other circuit panel having a top
surface 72 using standard surface-mounting techniques. In
accordance with standard surface-mounting techniques, the
connecting elements or solder balls 62 are aligned with bonding
contacts 76 exposed at the top surface of the circuit board, and
the solder balls are reflowed so as to bond the solder balls to
bonding contacts 76 and thus bond contacts 76 to the corresponding
bonding contacts 58 on the bottom surface of the microelectronic
element 44. Typically, a flux is applied to aid the solder reflow
process. During reflow, the solder in balls 62 forms a
metallurgical bond with socket contacts 32. As best seen in FIG. 5,
the prongs 34 of the socket contacts may penetrate into the
individual solder balls, as schematically depicted at 34'. The
socket contacts may thus provide additional reinforcement within
the solder balls in the finished assembly.
[0036] In this condition, first microelectronic element 44 sits on
the circuit panel in substantially the same position as if the
adaptor were not present. The first socket region 26 of adaptor
substrate lies in the gap between the bottom surface 50 of the
first microelectronic element and the top surface 72 of the circuit
board. The height of the microelectronic element above the top
surface 72 of the circuit panel may be nearly or exactly the same
as if the adaptor were not present. The exposed terminals 40 of the
adaptor provide an auxiliary mounting surface on top of element 44.
A second microelectronic element 78 and a third microelectronic
element 80 may be mounted on the terminals 40, again using standard
surface-mounting techniques. All of the operations involved in
assembling the adaptor to the first microelectronic element
mounting the adaptor to the circuit board and assembling the
further microelectronic elements to the terminals can be performed
as part of a "board stuffing" operation used to mount
microelectronic elements on a circuit board.
[0037] Other microelectronic elements 82 may be mounted on the top
surface of the circuit board in the normal manner. First
microelectronic element 44 is connected to these additional
elements by traces 74 within and on the circuit board 70. The
second and third microelectronic elements 78 and 80 are connected
to the first microelectronic element 44 through the terminals 40,
traces 42 and socket contacts 32 of the adaptor. The second and
third microelectronic elements are also connected to appropriate
contact pads 76 of the circuit board, and, hence, to other elements
to other elements of the circuit, by the terminals 40, traces 42
and socket contacts 34 in conjunction with the connecting elements
or solder balls which serve to connect the first microelectronic
element to the circuit board.
[0038] The assembly operation can be repeated numerous times to
produce numerous circuit assemblies. The operation can be varied by
varying the second and third microelectronic elements 78 and 80
used with the same type of first microelectronic element 44. For
example, in fabricating cellular telephones, different types of
static random access memory or SRAM and different types or sizes of
flash memory may be provided as the second and third
microelectronic elements in different units, all of which employ
the same baseband ASIC or FPGA. The cellular telephone manufacturer
may purchase standard chips in standard packages. The configuration
of the adaptor may be varied to accommodate different second and
third microelectronic elements.
[0039] The entire assembly is compact, in that the second and third
microelectronic elements 78 and 80 do not occupy any additional
area on the board top surface. Further, the assembly has a
relatively low height. Although the second and third
microelectronic elements are depicted in FIG. 4 as mounted to the
terminals by a ball grid array, other types of mountings may be
employed. For example, the mountings for these elements may include
relatively thin layer of solder in a so-called "land grid array" to
further minimize the overall height of the assembly above the board
top surface. Other types of interconnections may be employed, as,
for example, wire-bonded or leaded interconnections.
[0040] The joints between the second and third microelectronic
elements 78 and 80 and the adaptor are subjected to relatively low
stress because the underlying first microelectronic element 44
typically has a coefficient of thermal expansion close to those of
the second and third microelectronic elements. For example, a
typical copper and epoxy circuit board 70 may have a coefficient of
thermal expansion on the order of 16-18 ppm/.degree. C., whereas
the coefficient of expansion of the first microelectronic element
44, which is an aggregate of the coefficients of thermal expansion
of the die (about 2-3 ppm/.degree. C.) and the epoxy over-molding,
and hence would be somewhat less than that of the circuit board,
as, for example, about 8 ppm/.degree. C. As mentioned above, the
first microelectronic element may include provisions to allow the
bonding contacts 58 to move relative to the die 46 and thus relieve
differences in expansion between the circuit board 70 and the die.
Where this arrangement is employed, the adaptor does not
substantially restrict movement of the bonding contacts. Some or
all of the difference in thermal expansion between the die in first
element 44 and circuit board 70 may be accommodated by deformation
of the connecting elements or solder balls 62. Because the adaptor
extends around these elements and does not add height to these
elements, relatively large solder balls can be used to enhance
reliability of this connection without unduly increasing the
overall height of the assembly.
[0041] The socket contacts 32 can be designed to enhance the
structure of the solder balls 62 so that they can better resist
strain due to CTE mismatch between the die 44 and the circuit board
70. In particular, it is desirable for the socket contacts to
enhance the regions of the solder balls near the junctions of the
solder balls with bonding contacts 58, near the junctions of the
solder balls with the contact pads of the circuit board, or both.
Reinforcing one or both of these regions, commonly referred to as
fillet regions of the solder balls 62, can provide enhanced
resistance to forces that could otherwise cause premature failure
of the connections.
[0042] Because the second and third microelectronic elements 78 and
80 are interconnected with the first element through the adaptor,
the main circuit board 70 need not include layers of traces to make
these interconnections. This simplifies the layout of the main
circuit board and, in some cases, can reduce the number of layers
required in the board as a whole.
[0043] In a variant of the manufacturing process discussed above,
the second and third microelectronic elements 78 and 80 may be
assembled to the adaptor and bonded to terminals 40 before the
first microelectronic element and adaptor are assembled to the main
circuit board. Indeed, the second and third microelectronic
elements may be bonded to the adaptor before the adaptor is folded
or may be supplied as part of the adaptor.
[0044] The adaptor discussed above with reference to FIGS. 1-4 has
socket contacts on the outer surface 24 of the dielectric substrate
20 and has the terminals and traces also disposed on the outer
surface. In a further variant (FIG. 6), the socket contacts 132,
traces 142 and terminals 140 may be disposed on the inner surface
122 of the dielectric substrate 120. Here again, the socket
contacts are aligned with apertures 130 in the dielectric
substrate. When the first microelectronic element 144 is assembled
to the adaptor, the connecting elements or solder balls 162 project
through the socket contacts 132 and through the apertures 130, as
depicted in FIG. 6. Also, the terminals 140 are exposed to the
outer surface 124 of the substrate through holes 125 in the
substrate aligned with the terminals. The adhesive 138 may be
provided as a "dry pad" or solid adhesive layer overlying the
terminals on the inner surface 122 of the substrate. Also, the
adhesive 138 may extend into the socket region and may overlie the
entire inner surface of the substrate. The dry pad may have
apertures 139 aligned with the apertures 130 and socket contacts
132. In this embodiment, the dry pad acts as masking or
anti-shorting layer to protect the traces from accidental contact
with the edges of the chip or with one another when the substrate
is folded.
[0045] An assembly according to yet another embodiment of the
invention (FIG. 7) includes an adaptor having a similar flexible
substrate 220 and first socket contacts 232 in a socket region 226.
Here again, the socket region extends into the gap between the
bottom surface 250 of the first microelectronic element and the top
surface 272 of the circuit board. In this embodiment as well, the
adaptor includes a functional element in the form of terminals 240
in an attachment region 224 of the substrate, remote from the
socket region 226. Here again, the attachment region projects
outwardly beyond an edge 254 of the first microelectronic element
244. However, the attachment region is not folded back over the top
of the first microelectronic element. Instead, the attachment
region is extended over a neighboring element 201 on the circuit
board. Once again, the second microelectronic element 278 may be
mounted on the attachment region of the adaptor. In further
variance, attachment regions can be provided so as to overlie more
than one additional element on the circuit board and can project
outwardly from more than one edge of the first microelectronic
element.
[0046] An assembly according to yet another embodiment of the
invention shown in FIG. 8 includes an adaptor having a substrate
320 with a first socket region 326 and first socket contacts 332
similar to the first socket contacts discussed above. However, the
attachment region 324 of the substrate has terminals in the form of
a second set of socket contacts 333 similar to the first socket
contacts and has apertures 331 extending through the substrate in
this region, in alignment with the second socket contacts. The
second socket contacts 333 are connected via traces 340 on the
substrate of the adaptor to the first socket contacts. In this
assembly, the connecting elements 362 of the first microelectronic
element 344 extend through the first socket contacts 332. The
second microelectronic element 378 is mounted to the adaptor in
substantially the same way as the first microelectronic element, so
that second connecting elements 363 such as solder balls associated
with the second microelectronic element extend through the holes
331 in the attachment region of the substrate and engage the second
socket contacts. Both of these microelectronic elements 344 and 378
may be assembled to the adaptor in the manner discussed above with
reference to FIG. 3, and the entire assembly then may be mounted on
a circuit panel 370 so as to engage the connecting elements 362 and
363 of both microelectronic elements with the circuit panel.
Because the first and second microelectronic elements 344 and 378
are interconnected through traces 340 of the adaptor, the circuit
panel need not incorporate the traces required for such
interconnection and, hence, can be simpler and, in some cases, may
incorporate fewer layers than would otherwise be required. Here
again, presence of the adaptor does not add to the height of the
assembly.
[0047] The component depicted in FIG. 9 incorporates a substrate
420 having a first socket region 426 formed as a central panel of a
generally cruciform shape and having additional or attachment
regions 424 formed as arms of the cruciform shape projecting
outwardly from the central panel. In this embodiment, the adaptor
is prefabricated with functional elements in the form of additional
semiconductor chips 478, 479, 480 and 481 pre-connected to traces
440 extending to the first socket contacts 432 in the socket region
426. The particular embodiment shown has the first socket contacts
432, traces 440 and additional microelectronic elements 478-481,
all mounted on the inner surface of the substrate. Here again, a
microelectronic element such as element 440 is assembled to the
adaptor so that connecting elements 462 on the microelectronic
element project through the first socket contacts. As shown in FIG.
10, each arm of the adaptor is folded so as to bring the various
additional regions 424 over the first microelectronic element 444
and stack the various additional microelectronic elements over the
first microelectronic element. Such a sub-assembly may be mounted
onto a circuit board. The adaptor in accordance with this
embodiment of the invention provides advantages similar to those
achieved in the stacked package disclosed in commonly assigned,
co-pending U.S. patent application Ser. No. 10/077,388, filed Feb.
15, 2002, the disclosure of which is also incorporated by reference
herein. For example, the traces connecting the first
microelectronic element and socket contacts 432 to each of the
microelectronic elements are of equal or nearly equal length, so
that propagation times of signals to the various additional
microelectronic elements 478-481 are substantially equal. However,
the first microelectronic element 444 may be provided in a standard
package. The arrangement of FIGS. 9 and 10 may be made with less
than four or more than four additional regions. For example, if
only two additional regions are provided, these may be provided on
opposite sides of the central or first socket region 426.
Regardless of the number of such additional regions, the additional
regions may be folded on top of each other as shown in FIG. 10, or
may extend outwardly from the central panel as shown and described
in reference to FIGS. 7 and 8.
[0048] The connecting elements which link the first microelectronic
element to the circuit board need not be solder balls or other
masses of bonding material. In the embodiment of FIG. 11, the first
microelectronic element 544 incorporates a semiconductor die 546
mounted in a lead frame-type package which incorporates an epoxy
over-molding 545 encapsulating the active die and metallic leads
562 projecting out of edges of the over-molding and extending
downwardly beyond the bottom surface 550 of the over-molding. In
this arrangement, the adaptor substrate 520 has apertures 530
extending through it from its inner surface 522 to its outer
surface 524. Socket contacts in the form of metallic via liners 532
are provided in these apertures. The apertures 530 and socket
contacts are provided in a socket region 526 of the substrate. Here
again, the socket region 526 of the substrate lies at least in part
beneath the first microelectronic element 544, in the gap between
the bottom surface 550 of the microelectronic element and the top
surface 572 of a circuit board 570 when the first microelectronic
element is mounted on the circuit board. The leads 562 of the lead
frame package extend through the apertures in the socket region of
the substrate and engage the socket contacts 532. The leads may be
soldered to the socket contacts or vias 532 of the adaptor. Here
again, an additional region 528 of the substrate extends outside of
the gap between the microelectronic 544 and the circuit board, so
that an additional microelectronic element 578 can be engaged with
terminals 540 on the additional or attachment region 528. In this
embodiment, the adaptor substrate 520 is folded (about an axis
parallel to the plane of the drawing) to place the additional
region 528 over the top surface 552 of the first microelectronic
element 544. Here again, the additional microelectronic element may
be sub-assembled to the adaptor before or after mounting the first
microelectronic element and adaptor to the circuit board. The
circuit board has contact elements arranged to make connection with
the leads 562 of the first microelectronic element, as, for
example, pads 574 arranged for surface mounting of the leads or via
holes 575 extending through the circuit board with appropriate via
liners for through-board solder mounting the lead frame package.
Although both pads 574 and via holes 575 are depicted in FIG. 11,
in practice the board typically would include one or the other, and
not both. In a further variant, the same solder which connects
leads 562 to contact elements 574 or 575 may connect the leads to
the socket contacts 532 of the adaptor.
[0049] An assembly according to a further embodiment of the
invention (FIG. 12) includes an adaptor having a dielectric body
620 generally similar to the adaptor discussed above with reference
to FIGS. 1-4. However, the adaptor of FIG. 12 includes a first or
bottom connection region 626 and an additional region 628 remote
from region 626. Here again, the adaptor body 620 has an inner
surface 622 and an outer surface 624. The first connection region
626 extends in a gap between the first microelectronic element 644
and the circuit board 670, and thus extends beneath the bottom
surface 650 of the first microelectronic element 644. In the first
connection region 626, the inner surface 622 of the dielectric body
faces upwardly, toward the first microelectronic element, whereas
the outer surface 624 faces downward, toward the circuit board 670.
The additional region extends outside of the gap, and overlies the
top surface 652 of the first microelectronic element.
[0050] In place of the socket contacts discussed above, the adaptor
of FIG. 12 has first conductive attachments 634 which include
conductive pads disposed at or near the inner surface 622 of the
body in the first connection region 626, and holes 630 extending
through the body in alignment with these pads. Pads 634 desirably
are relatively thin as, for example, about 10-20 micron in
thickness. Pads or first conductive attachments 634 are connected
by traces 642 to terminals 640 on the additional region 628.
[0051] Here again, the first microelectronic element 644 has
bonding pads 658 exposed at its bottom surface. These bonding pads
are connected by internal connecting elements 602 to the pads or
conductive attachments 634 of the adaptor, which in turn are
connected by mounting elements 662 to the contact pads 676 of the
circuit board. Most preferably, the internal conducting elements
are thin layers of a conductive bonding material such as solder
lands. Desirably, the height h.sub.1 of each internal conducting
element, (FIG. 13) measured from the bottom surface 650 of the
first microelectronic element to the bottom of the internal
conducting element, is about 50 microns or less, and most
preferably about 40 microns or less. The mounting elements 662 most
preferably are masses of a conductive bonding material such as
solder balls or solid core solder balls. The mounting elements may
have height h.sub.2 or vertical extent from the upper surface 672
of the circuit board considerably greater than the height h.sub.1
of the internal connecting elements 602. For example, the height h2
of the mounting elements may be on the order of 100 to 300 microns.
However, the assembly still provides a relatively low overall
height or distance H between the top surface 672 of the circuit
board and the bottom surface 650 of the first microelectronic
element. Because the mounting elements 662 extend through holes 630
in body 620, a significant portion, typically about 25% or more, of
the height h.sub.2 of the mounting elements is concealed within the
thickness t of body 620. Thus, the overall height or distance H
from the board surface 672 to the bottom surface of the first
microelectronic element is less than the aggregate or sum of
heights h1, h2 and the thickness t of the body. Stated another way,
the assembly according to this embodiment of the invention can
provide a low overall height while allowing significant solder ball
height. Such relatively large solder balls can provide enhanced
resistance to strains due to differential thermal expansion of the
elements.
[0052] In a variant of this approach, the conductive attachments
634 are disposed at or near the outer surface 624, and the internal
connecting elements 602 extend from the first microelectronic
element 644 partially or entirely through the thickness of the body
to the conductive attachments. In this arrangement, the internal
conductive elements may be elements such as solder balls or solid
core solder balls having a relatively great height. The conductive
attachments or pads 634 are connected to the contact pads of the
circuit board by relatively thin mounting elements such as solder
lands. In this variant, the roles of the internal connecting
elements and mounting elements are reversed relative to the
arrangement shown in FIGS. 12 and 13. Here again, however, height
of the larger element (the internal connecting element) is
substantially concealed within the thickness t of the body, so that
the overall height H remains less than the sum of the heights of
the internal connecting elements, the mounting elements and the
thickness of the body. In a further variant, the conductive
attachments may include conductive elements at both surfaces of the
body defining sockets adapted to receive the mounting elements, the
internal connecting elements, or both so that either or both of
these are partially or entirely concealed within the thickness of
the body. For example, sockets as depicted in certain preferred
embodiments of U.S. Pat. No. 6,200,143, the disclosure of which is
incorporated by reference, may be used in this manner.
[0053] An assembly according to yet another embodiment of the
invention (FIG. 14) is generally similar to the assembly of FIGS.
12 and 13. However, in the assembly of FIG. 14, the conductive
attachments 734 are arranged so that the internal connecting
elements 702 which connect the first microelectronic element 744 to
the attachments are offset from the mounting elements 762 which
connect the attachments to the contact pads of the circuit board.
The height h.sub.1 of the connecting elements overlaps a part of
the height h2 of the mounting elements, a part of the thickness t
of the body of the adaptor, or both. In this arrangement as well,
the overall distance or height H from the top surface of the
circuit board to the bottom surface of the first microelectronic
element is less than the sum of h1, h2 and t. In one example of
such as structure, the connecting region 726 may have a structure
generally similar to the sockets shown in U.S. Pat. No. 5,951,305,
the disclosure of which is also incorporated by reference
herein.
[0054] In yet another variant (FIG. 15) the, internal connecting
elements are again offset in horizontal directions from the
mounting elements 862. Here again, the internal connecting elements
802 make connections to conductive attachments 834 on the bottom or
first connection region 826 of the adaptor body. This region of the
body is deformed into a non-planar shape, so that once again the
height h1 of the internal connecting elements overlaps the height
h2 of the mounting elements, the thickness t of the body, or both.
The configuration of this region may be similar to the
configuration of the sockets shown in certain embodiments of U.S.
Pat. No. 6,086,386, the disclosure of which is also incorporated by
reference herein. The arrangements of FIGS. 14 and 15 can also
provide a low overall height H of the first microelectronic element
above the circuit board, and hence a low height for the entire
assembly, while using internal conductive elements and/or mounting
elements having substantial height. The mounting arrangements
discussed above with reference to FIGS. 12-15 also can be used with
any of the adaptor configurations discussed herein, including those
discussed above with reference to FIGS. 7-11. Also, although the
embodiments of FIGS. 12-15 have been discussed above with reference
to the completed assembly, the present invention also includes the
adaptors and assembly methods used to form these assemblies. The
adaptors are similar to the adaptors discussed above, except that
the socket contacts and socket regions are replaced by the
conductive attachment elements and connection region. Also, the
assembly methods are similar to those discussed above with
reference to FIGS. 1-4, except that the bonding contacts of the
first microelectronic element are connected to the conductive
attachments of the adaptor, rather than directly to the circuit
board contact pads, and the method includes the further step of
connecting the conductive attachments of the adaptor to the circuit
board contact pads.
[0055] Numerous other variations and combinations of the features
discussed above can be utilized without departing from the present
invention. For example, in the embodiments discussed above, the
additional functional elements provided in the adaptor are either
terminals (such as terminals 40 in FIG. 1) or additional
semiconductor chips 478-481 (FIGS. 9 and 10). However, other
functional elements such as passive electrical components may be
incorporated in place of or in addition to these elements. In still
other arrangements, the adaptor may extend beyond the circuit
board. For example, the adaptor can extend around an edge of the
circuit board to provide mounting terminals on the bottom or rear
surface of the circuit board. Alternatively, the adaptor can be in
the form of a ribbon cable which has functional elements in the
form of contacts adapted to engage a socket on another circuit
board or another electronic device.
[0056] Also, it is not essential that the substrate be thin or
flexible throughout its entire extent. In those embodiments where
bending or folding is required, the substrate may be flexible in
only the regions to be deformed during bending or folding and may
be rigid in other regions. In embodiments where the substrate will
not be bent or folded, as, for example, in the arrangement of FIG.
8, the substrate may be entirely or partially rigid. Also, although
the adaptors discussed above incorporate only a single layer of
traces, additional metallic elements may be provided as desired.
For example, the adaptor may include electrically conductive plane
for carrying a ground or other substantially constant potential
spaced apart from the traces. Also, more than one layer of traces
may be incorporated in the adaptor to accommodate more complex
wiring requirements. Connecting elements other than the solder
balls and leads discussed above may be employed, as, for example,
solid core solder balls and pins.
[0057] In the foregoing description, terms such as "top", "bottom",
"upwardly" and "downwardly" refer to the frame of reference of the
microelectronic element or circuit board. These terms do not refer
to the normal gravitational frame of reference.
[0058] As these and other variations and combinations of the
features discussed above can be utilized without departing from the
present invention as defined by the claims, the foregoing
description of the preferred embodiment should be taken by way of
illustration rather than by way of limitation of the invention.
* * * * *