Abstract:
Disclosed herein is a method of positioning and placing an integrated circuit on a printed circuit board. The integrated circuit comprises first geometrical elements. The first geometrical elements are of one or more predefined shapes and are located on one or more predefined surfaces of the integrated circuit. The printed circuit board comprises second geometrical elements. The second geometrical elements are shaped to accommodate the first geometrical elements. The first geometrical elements are designed to fit into the second geometrical elements. The first geometrical elements are positioned and placed over the second geometrical elements. The first geometrical elements come in contact with the second geometrical elements at two or more points. The positioning and placement of the first geometrical elements over the second geometrical elements limits displacement of connections of the integrated circuit from the printed circuit board.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of non-provisional patent application number P 384063, titled “Means of positioning the enclosure of an electronic component, especially integrated circuit constructed as single layer, multi-layer or as a stacked package on silicon (Si) or ceramic substrates types: IC, SiP or MCM”, filed on Dec. 17, 2007 in the Polish Patent Office. 
     BACKGROUND 
     This invention, in general, relates to integrated circuits. More particularly, this invention relates to positioning and placing of the integrated circuit (IC) with leads or lead-less, hybrid circuits (HC), system in package (SIP), and multi-chip module (MCM) on the corresponding pads of a printed circuit board (PCB) or other substrate. 
     Shape or particular characteristics of the package of an IC, HC, SIP, or MCM package including the way the IC package is manufactured is based on simple and precise positioning of the package on the PCB during assembly or service. 
     At present expensive and high precision pick and place machines are used to position the IC package above corresponding pattern of connections on the PCB and to position the IC correctly and to solder the IC to the PCB. The placement accuracy of the IC is dependant on precision of the positioning or placing machine, and also dependant on the machine operator. 
     To establish a position metrology based on precision, optics and mechanics is used in conjunction with graphical two or three dimensional elements on the PCB which are not directly related to the IC package, or with IC connections and their matching equivalents such as the pads placed on the PCB. 
     The quantity of elements participating in the positioning process and variety of external conditions results in inaccurate positioning. 
     Hence, there is a need for a method to position and place the IC over the PCB without using expensive pick and place machines. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a method of placing geometrical elements of an integrated circuit and a printed circuit board as described in Example 1. 
         FIG. 2  illustrates contact made by geometrical elements of an integrated circuit and a printed circuit board as described in Example 1. 
         FIG. 3  illustrates contact made by geometrical elements of an integrated circuit and a printed circuit board as described in Example 2. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Disclosed herein is an integrated circuit (IC) package comprising first geometrical elements  102  that represent a unique rotation pattern. The IC package is placed during assembly in such a way that the first geometrical elements  102  fit into corresponding second geometrical elements  103  on a printed circuit board (PCB)  104 . The corresponding second geometrical elements  103  on the PCB  104  are a reversed pattern of the first geometrical elements  102  on the IC  101 . The method of placing geometrical elements of the IC  101  over the PCB  104  is exemplarily illustrated in  FIG. 1 . 
     The first geometrical elements  102  on the IC package and the reversed second geometrical elements  103  on the PCB  104  are constructed in such a way that they touch each other in at least two resistance points and in particular cases touch each other&#39;s surface, limiting movement of the IC  101  in a plane of the PCB  104  or other surface on which the IC  101  was going to be placed, that is, limiting the IC  101  movement in any direction on the PCB  104 . 
     The tolerance of the dimensions of the first geometrical elements  102  defining the accuracy of their fit is in direct relationship to the required accuracy and tolerance of placement of the IC  101  on the PCB  104 . 
     The first geometrical elements  102  on the IC  101  and the reversed second geometrical elements  103  on the PCB  104  are placed on the IC  101  and on the PCB  104  so that the proper fit of the first geometrical elements  102  is possible in one position of the IC  101  in relationship to the PCB  104 . 
     The pattern of one or more first geometrical elements  102  may be protruding out-wards from the bottom or the sides of the IC  101 , if more than one first geometrical elements  102  are chosen, as far as possible away from each other and on the diagonal of the IC  101 , while the pattern of the corresponding one ore more second geometrical elements  103  on the PCB  104  is a matching indent or opening in the PCB  104 . 
     The pattern of the one ore more first geometrical elements  102  may be protruding inwards from the bottom or sides of the IC  101 , if more than one first geometrical elements  102  are chosen, as far as possible away from each other and on the diagonal of the IC  101 , while the pattern of the corresponding one or more second geometrical elements  103  on the PCB  104  is a matching geometrical pattern protruding outwards or sticking out from the PCB  104 . 
     The first geometrical elements  102  intended for precision and defining orientation and accurate placement may be made of materials that conduct electricity and additionally can serve as electrical contacts. 
     In an embodiment, the first geometrical elements  102  may be a part of a cylinder with semicircular or semispherical ends positioned horizontally and not symmetrically on IC  101  bottom surface. In such a case, the corresponding shape on the PCB  104  will be an elongated opening or hole in the PCB  104 , matching the shape of the half cylinder with the semi-circular or semispherical ends. 
     The geometrical pattern may comprise the two cylinders protruding vertically from the bottom surface of the IC  101 , preferably on the opposite sides of the IC  101  on or close to a diagonal. The ends of the cylinders, by design, are conical, angled or rounded to facilitate insertion of the cylinders into matching holes or indents on the PCB  104 . In the case of two or more cylinders, the corresponding pattern on the PCB  104  is a set of two or more round holes having diameters and spacing matching the two or more cylinders protruding from the bottom surface or attached to the sides of the IC  101 . 
     The geometrical shape for the pattern may also be an indent in a shape of a cylinder with circular ends placed not centrally on the bottom surface of an integrated circuit. In such a case, the matching pattern on the PCB  104  will be half cylinder placed horizontally and with rounded ends to mach the indent in the IC  101 . 
     The geometrical pattern may be a set of minimum two round indents or holes in the IC  101  in its bottom surface, located by design on the opposite sides and possibly close to, or diagonally on the IC  101 . The corresponding, matching pattern on the IC  101  has minimum two cylinders protruding vertically from the PCB  104  with rounded, conical, or angled ends to facilitate the insertion of the IC  101  on the cylinders protruding from the PCB  104 . The first geometrical elements  102  may be a combination of one or more protruding elements and indents, and the corresponding second geometrical elements  103  accommodate the protruding elements and the indents. 
     The method disclosed herein facilitates the placement of an IC  101  of any kind precisely and expediently to match land pattern on the PCB  104 , or other substrate in less than a second. The use of the geometrical matching patterns on the bottom or sides of the IC  101  and the PCB  104  eliminates the necessity to use expensive and precise machines like automated or manual pick and place machines. Using the method of the matching geometrical patterns simplifies assembly and service of the PCB&#39;s  104  build employing surface mount technology. It makes possible the placement of the IC&#39;s  101  by hand, without the use of any machines. 
     Example 1 
     The overlapping of the IC  101  electrical connections with the corresponding pads on the PCB  104  is performed by matching or inserting the first geometrical elements  102  on the bottom of the IC  101  with the corresponding second geometrical elements  103  on the PCB  104 . The first geometrical elements  102  on the bottom of the IC  101  and the second geometrical elements  103  on the PCB  104  are selected in such a way so that when inserted into one another they touch each other in at least two points a′, a″, and in a particular case touch each other along sides b′, b″ as illustrated in  FIG. 2 , thereby limiting displacement in any direction including rotation of the IC  101  when placed on the surface of the PCB  104 . The accuracy of dimensions of the first geometrical elements  102  on both IC  101  bottom surface and the corresponding second geometrical elements  103  on the PCB  104  depends directly on the required accuracy of placement of the electrical connections of the IC  101  on the corresponding pads or electrical connections of the PCB  104 . 
     The first geometrical elements  102  on the bottom of the IC  101  and the second geometrical elements  103  on the PCB  104  are made and located so that their correct match is possible only when the IC  101  electrical connections correctly overlap with the corresponding electrical connections, lands, or pads on the PCB  104  on which the IC  101  is placed. 
     The first geometrical elements  102  may be indents on the bottom of the IC  101  or on its sides located preferably on the IC&#39;s  101  opposite sides. The corresponding second geometrical elements  103  on the PCB  104  may protrude upwards and have dimensions and spacing corresponding to dimensions and spacing of the first geometrical elements  102  on the bottom of the IC  101  to fit snugly when the IC  101  is placed correctly on the PCB  104 . 
     The first geometrical elements  102  on the bottom of the IC  101  and the second geometrical elements  103  on the PCB  104  may be made from materials that conduct electricity and may also serve as additional contacts. 
     In Example 1, the first geometrical elements  102  on the bottom of the IC  101  are in the form of half cylinders with rounded, half circle, or half spherical ends placed horizontally and asymmetrically in relationship to the IC package. In this case, the corresponding second geometrical elements  103  on the PCB  104  are openings or holes or indents in a PCB  104  of corresponding dimensions and locations to the first geometrical elements  102  on the bottom of the IC  101 . 
     Alternatively the first geometrical elements  102  on the bottom of the IC  101  may be openings or holes or indents located asymmetrically on the IC package, and the second geometrical elements  103  on the PCB  104  are in the form of a matching half cylinders with rounded, half circle or half spherical ends placed horizontally on the PCB  104 . Furthermore, the first geometrical elements  102  are located in places to assure overlap of the electrical connections of the IC  101  with the corresponding electrical connections on the PCB  104 . 
     Example 2 
     In this example, the first geometrical elements  102  on the bottom of the IC  101  are in the form of two cylinders protruding vertically downwards from the bottom surface of the IC  101 . The first geometrical elements  102  may be located on the IC&#39;s  101  opposite sides on or close to diagonal formed by opposite corners of the IC  101  The first geometrical elements  102  are asymmetrically located if the cylinders have the same diameter. 
     The matching second geometrical elements  103  on the PCB  104  are round openings or holes or indents in a PCB  104  of corresponding dimensions and locations to the first geometrical elements  102  on the bottom of the IC  101 . The ends of the cylinders have angled, rounded or conical edges to facilitate a snug fit of the cylinders into corresponding openings or indents in the PCB  104  when IC  101  is placed on the PCB  104 . 
     Alternatively, the first geometrical elements  102  on the bottom of the IC  101  may be round openings, holes, or indents located asymmetrically on the IC package, and the second geometrical elements  103  on the PCB  104  are in the form of matching cylinders with angled, rounded, or conical edges to facilitate a snug fit of the cylinders into corresponding openings or indents on the bottom of IC  101  when the IC  101  is placed on the PCB  104  and located in such places to assure overlap of the electrical connections of the IC  101  with the corresponding electrical connections on the PCB  104 . The contact made by geometrical elements of the IC  101  and the PCB  104  as described in example 2 is exemplarily illustrated in  FIG. 3 . 
     The IC  101  placement method disclosed herein allows for precise and quick placement of the IC package on the corresponding electrical connections on the PCB  104  and elimination of expensive feeders and positioning jigs or machines. 
     Implementation of the method disclosed herein simplifies surface mount components placement, facilitates and makes it economical and quicker, especially during processes of low volume production and service of PCB&#39;s  104  build using surface mount technology.