To interface bare semiconductor dies to a support surface such as a printed circuit board, there is a need for an appropriate package substrate to interface and route the semiconductor dies within a package, such as a ball grid array (BOA) package, chip scale package (CSP), or system-in-package (SiP), to the printed circuit board. A conventional interface substrate may start with a core material with laminate film layers built up on both sides of the core material. A flip-chip die may then be coupled to the interface substrate using solder bumps.
Demand for higher performance, power efficiency, and reduced form factor have driven successive generations of die shrinks, resulting in flip-chip dies with very high density interconnect features. As the solder bump interconnects are also required to become increasingly dense, the manufacturability, cost, and reliability requirements for interface substrates have gradually become more difficult to meet. Moreover, with shrinking die sizes, effective thermal dissipation from the smaller available die surface area has also become a greater concern.
The present disclosure is directed to low cost and high performance flip chip packages, substantially as shown in and/or described in connection with at least one of the figures, and as set forth more completely in the claims.
The following description contains specific information pertaining to implementations in the present disclosure. One skilled in the art will recognize that the present disclosure may be implemented in a manner different from that specifically discussed herein. The drawings in the present application and their accompanying detailed description are directed to merely exemplary implementations. Unless noted otherwise, like or corresponding elements among the figures may be indicated by like or corresponding reference numerals. Moreover, the drawings and illustrations in the present application are generally not to scale, and are not intended to correspond to actual relative dimensions.
As discussed in the background, demand for higher performance, power efficiency, and reduced form factor have driven successive generations of die shrinks for flip chip 110, requiring a correspondingly higher pitch between solder bumps 115. For example, for a flip chip 110 using a 40 nm process, in high volume manufacturing, a 150 micron pitch is standard between solder bumps 115. However, solder bumping is quickly reaching its technological limit as the minimum practical solder bump pitch is considered to be 130 to 150 microns.
Flip chip 110 is manufactured using smaller feature sizes, such as 28 nm and below, solder humping technology is unable to keep pace with the reduced bump pitch demanded of flip chip 110. Thus, a die size of flip chip 110 must increase, resulting in significant cost and form factor increases. Even if the die size of flip chip 110 is successfully reduced, effective thermal dissipation from the smaller die surface area also becomes a greater concern. Moreover, at fine solder bump pitch densities, reliability issues with the solder bump interconnects become increasingly pronounced, with solder joint cracking, electromigration performance degradation, and other issues resulting in lower yields and increased costs.
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Flip chip package 200a in
Since reflow processes can be avoided entirely and the formation of vias 232 can be carried out at essentially room temperature, coefficient of thermal expansion (CTE) mismatches arising from such reflow processes are also advantageously avoided. Conductivity and electromigration performance is also improved as electrical connection routes 295 may be composed wholly of highly conductive materials such as copper, in comparison to the required solder humps 115 of package 100.
Furthermore, the tight coupling of semiconductor die 210 to package substrate 206 eliminates the need for a separate substrate fabrication process as package 200a is assembled using a substrate panel level process. Thus, central core 140 of substrate 120 may be completely omitted in package substrate 206, resulting in a coreless substrate. Thus, pre-soldering, core materials, and core via drilling and plating steps may be omitted, and layer counts may also be reduced as layers do not need to be built on both sides of a core. By reducing the number of required steps and materials, a very cost effective package assembly may be provided while providing a thinner form factor and higher electrical performance. Moreover, since heat spreader 280 is already an integral part of package 200a and is coupled to semiconductor die 210 via a surrounding adhesive TIM 286, improved thermal dissipation may be provided and package height may be even further reduced as a separate heat sink is not required.
With regards to electrical performance, according to electrical simulations, package 200a may be expected to have an approximately 60% reduction in package resistance and an approximately 70% reduction in inductance when compared to package 100, both considerable improvements. However, since capacitance is largely related to the build-up stack of laminate dielectric films 290, little variance in capacitance is expected between package 100 and package 200a. The removal of the thick central core 140 with its large vias 145 is also expected to provide significant improvements in crosstalk, simultaneous switching output (SSO) noise, and signal path impedance mismatch, which in turn reduces serial interface differential return loss and parallel interface signal reflection. These signal improvements may be especially relevant for high speed, high density memory devices.
From the above description it is manifest that various techniques can be used for implementing the concepts described in the present application without departing from the scope of those concepts. Moreover, while the concepts have been described with specific reference to certain implementations, a person of ordinary skill in the art would recognize that changes can be made in form and detail without departing from the spirit and the scope of those concepts. As such, the described implementations are to be considered in all respects as illustrative and not restrictive. It should also be understood that the present application is not limited to the particular implementations described herein, but many rearrangements, modifications, and substitutions are possible without departing from the scope of the present disclosure.
This application is a continuation of U.S. patent application Ser. No. 13/357,078, entitled “Low Cost and High Performance Flip Chip Package,” filed on Jan. 24, 2012, which is expressly incorporated by reference herein.
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Parent | 13357078 | Jan 2012 | US |
Child | 14247222 | US |