Abstract:
Proper registration between layers of a laminated multi-layer interconnect can be achieved by precisely dimensioning the alignment plate, selecting the materials of which the alignment plate is composed to have the same thermal coefficient of expansion as the layers being laminated, and/or providing the alignment plate with pins sized to be equal to or larger the alignment/registration holes of the layers.

Description:
FIELD OF THE INVENTION  
         [0001]    The field of the invention is lamination of dielectric based layers.  
         BACKGROUND OF THE INVENTION  
         [0002]    When laminating multiple layer pairs and bond-plys to form a multiplayer interconnect, it is important to align the layers as well as possible to insure proper registration between layers. One method for doing so involves providing an alignment plate comprising tooling pins and stacking layers to be laminated on the plate so that the plate tooling pins pass through alignment/registration holes in each layer.  
           [0003]    Obtaining proper registration is sometimes made more difficult because of the tendency of the alignment plate dimensions to change with changes in temperature of the alignment plate. When the dimensions of the alignment plate change, the spacing between tooling pins changes as well. As a result, a layer may be distorted as a result of being stretched or compressed by such changes in spacing.  
           [0004]    To avoid stretching or compressing a layer as the plate&#39;s temperature changes, it is possible to utilize registration holes in the layers which are large enough so that changes in positions of the pins simply result in their movement within the registration holes without stretching or compressing the layer. Such a solution is less than desirable, however, as it allows movement of the layers on the pins with such movement making it more difficult to achieve proper registration between layers.  
           [0005]    Thus, there is a continuing need for improved lamination methods and devices which minimize registration problems resulting from temperature changes to the alignment plate.  
         SUMMARY OF THE INVENTION  
         [0006]    Methods and apparatus are provided which facilitate proper registration between layers when creating a laminated multi-layered device such and an integrated circuit (IC) interconnect. In particular, proper registration can be achieved by precisely dimensioning the alignment plate, selecting the materials of which the alignment plate is composed to have the same thermal coefficient of expansion (TCE) as the layers being laminated, and/or providing the alignment plate with pins sized to be equal to or larger the alignment/registration holes of the layers.  
           [0007]    Various objects, features aspects and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the invention, along with the accompanying drawings in which like numerals represent like components. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    [0008]FIG. 1 is a side view of an alignment plate embodying the invention.  
         [0009]    [0009]FIG. 2 is a perspective view of an alignment plate embodying the invention.  
         [0010]    [0010]FIG. 3 is a schematic of a method embodying the invention. 
     
    
     DETAILED DESCRIPTION  
       [0011]    Referring first to FIGS. 1 and 2, an alignment plate  10  comprises tooling pins  12 , and may be used to laminate layers  30 , possibly by stacking and sandwiching layers  30  on tooling pins  12  and between release sheets  22  and  24 . Alignment plate  10  is preferably constructed from a material having the same or approximately the same thermal coefficient of expansion (TCE) as layers  30 . Tooling pins  12  preferably have a diameter equal to or greater than the diameter of alignment holes  32  of layers  30 .  
         [0012]    Referring to FIG. 3, a preferred method of lamination comprises: step  100 , providing a plurality of layers  30  to be laminated; step  200 , determining the TCE of the layers  30  to be laminated; step  300 , providing an alignment plate  10  having approximately the same TCE, and step  400 , stacking the plurality of layers  30  onto the alignment plate  10 . If layers  30  and alignment plate  10  have the same TCE, the layers and plate will expand and contract together. In preferred embodiments, an alignment plate  10  will have a TCE close enough to the TCE of the layers as to maintain an alignment of ±5-20 μm. For polyimide film layers, copper alignment plates will likely have TCEs which match the TCEs of the layers sufficiently as to maintain an alignment of ±5-20 μm. Approximately the same as used in regard to the TCEs of the alignment plate  10  and layers  30  simply means that any difference in expansion and contraction of the copper plate  10  relative to layers  30  is small enough so that any misalignment caused by any such difference falls within acceptable bounds. However, it is contemplated that it would be particularly beneficial if the greatest difference between the TCE of alignment plate  10  and the average TCE of the layers be less than 2 ppm (parts per mill).  
         [0013]    Preferred methods will also comprise: lazing registration/alignment holes  32  in the layers  30  to be laminated, the registration holes  32  having a diameter at least as large as the diameter of the tooling pins  12  of the alignment plate  10 . The tooling pins  12  have at least the same diameter as the alignment/registration holes  32  in the layers  30  so as to prevent any movement of the layers  30  once they are positioned on the pins. The need for overly large registration holes to compensate for different rates of expansion between the alignment plate  10  and layers  30  is minimized if layers  30  and alignment plate  10  have similar TCEs. It is contemplated that lazing the registration holes  32  such that their diameters are at least 0-5 μm smaller than the diameter of the tooling pins would be particularly beneficial.  
         [0014]    It is also preferred that the materials comprising layers  30  be chosen so that layers  30  have substantially similar TCEs. Having all the layers  30  having substantially similar TCEs prevents distortion of one or more layers  30  because of differences in TCE between layers and between any one layer and the alignment plate  10 . Substantially similar as used in regard to the TCEs of the layers simply requires that the individual layers expand and contract similarly enough that any mis-alignment resulting from difference in rates of expansion fall within acceptable bounds. However, it is contemplated that it would be particularly beneficial if the greatest difference in TCE between any two layers is less than 2 ppm.  
         [0015]    Applying the disclosed methods to situations in which the tooling pins  12  are larger in diameter than the registration holes  32  will likely require forcing the layers  30  onto the tooling pins  12 . Providing tooling pins  12  with conical tips allows a layer to be positioned and to rest on the tooling pins  12  with a portion of the conical tips of tooling pins  12  extending into the registration holes  32  to insure proper alignment of the registration holes  32  and tooling pins  12  prior to forcing the layer onto tooling pins  12 .  
         [0016]    Thus, specific embodiments and applications of alignment plates have been disclosed. It should be apparent, however, to those skilled in the art that many more modifications besides those already described are possible without departing from the inventive concepts herein. The inventive subject matter, therefore, is not to be restricted except in the spirit of the appended claims. Moreover, in interpreting both the specification and the claims, all terms should be interpreted in the broadest possible manner consistent with the context. In particular, the terms “comprises” and “comprising” should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced.