Abstract:
Metal bases and window caps are used for semiconductor laser diode transistor-outline (TO) type packages and the like. New types of metal bases and window caps are disclosed. Tapered metal bases of the present invention works with tapered window caps of the present invention to function as a self-alignment mechanism of them, which is especially important for the ball lens window caps. The self-aligned tapered metal bases and tapered window caps provide a more productive (high yield), cost effective, and accurate means to manufacture semiconductor laser diode packages, which is a key factor for high-speed semiconductor laser diode application. The top surface of a metal base of the present invention has at least two fiducial marks designed to serve as the reference for the process automatic equipment to search and define the center of the metal base. These references will improve the accuracy of process equipment placing the laser diode chip and/or dispensing adhesive. To simplify the wire bonding process and make it robust, a two-bonding-surface post and a tilted-top post are disclosed in the present invention to eliminate the rotation process between two sequential bonding steps.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    (1) Field of the Invention  
           [0002]    The present invention relates to new types of metal bases and window caps for high-speed semiconductor laser diode transistor-outline (TO) type packages and the like and methods of aligning a laser diode chip to a metal base, and of self-aligning a window cap to the metal base so that the laser diode chip is automatically and indirectly aligned to the window cap with accuracy. This is one of crucial factors for manufacturing high-speed semiconductor laser diode packages and coupling optical fibers to laser diode packages. The present invention also relates to a metal base comprising a new feature, a post having two bonding surfaces, ensuring a reliable, inexpensive, and productive wire bonding process.  
           [0003]    (2) Prior Art  
           [0004]    The semiconductor laser diode package is well known in the prior art. Optical fiber is commonly used to guide laser light over a long distance. In order to couple a laser beam into an optical fiber the laser diode chip must be properly aligned with an optical element (a lens or lenses) so that as much laser light as possible is coupled into the optical fiber.  
           [0005]    In the processing of semiconductor laser diode package, a laser diode chip is placed onto a metal base to a certain degree of accuracy, and a window cap is welded to the metal base. By doing this the laser diode chip is aligned to the window cap. For fiber optics applications a piece of optical fiber then is aligned to the laser diode package. If the alignments are not accurate enough, most of the laser light will get lost. The whole package will fail for high-speed applications.  
           [0006]    There are varieties of prior art discussing devices and methods of aligning laser diode package to optical fiber. However those devices and methods are complex and expensive. Those prior art include U.S. Pat. No. 5,751,877 by Ishizaka et al., U.S. Pat. No. 6,244,754 B1, by Takagi et al., U.S. Pat. No. 5,870,517 by Wyland, U.S. Pat. No. 5,485,479 by Kitamura et al., U.S. Pat. No. 5,953,355, by Kiely et al., U.S. Pat. No. 5,939,773, by Jiang et al., U.S. Pat. No. 6,034,424, by Fujimura et al.  
           [0007]    To align an optical fiber to laser diode package, one of methods is known as active alignment. FIG. 56 is a copy of FIG. 5 of U.S. Pat. No. 6,034,424 and shows pigtail  562  connected to a laser diode package that comprises window cap  564  with ball lens  563 , laser diode chip  565  placed on top surface  566  of metal base  567 . During active alignment process, the laser diode chip  565  is powered, and testing equipment and automatic alignment equipment are used to test, place, and weld pigtail  562  to the laser diode package. If ball lens window cap  564  did not align to metal base  567  accurately, and/or the laser chip  565  did not align to the metal base  567  accurately, the laser diode chip  565  would not be aligned to the ball lens  563  accurately. As a result this package would be rejected in the following testing step. In this case the throughput and yield of the active alignment would be very low. There is no discussion about alignment between laser diode chip, metal base, and ball lens cap in this prior art.  
           [0008]    There is lack of prior art that discusses aligning a laser diode chip to a window cap.  
           [0009]    (A). For Vertical-Cavity Surface-Emitting Laser (VCSEL) Type of Packages  
           [0010]    Prior to aligning a piece of optical fiber to a laser diode package, it is desired to align the laser diode chip to the window cap, especially a ball-lens window cap. Otherwise a significant amount of laser light will get lost before it comes out the ball-lens window. Also when the alignment of a laser diode chip to a window cap, either a flat window cap or a ball-lens window cap, is not accurate enough, it would be impossible to align an optical fiber to that semiconductor laser diode package optically, even the active alignment for connecting an optical fiber to a semiconductor laser diode package is used.  
           [0011]    There are two steps in the alignment procedure: (1) align the laser diode chip to a metal base using pick/place process, and (2) align a window cap to the metal base during welding process.  
           [0012]    In the first alignment step, the pattern recognition (PR) system of automatic equipment is employed to find the center of the metal base by using either the outer edge of the top surface of the metal base or the edges of post-housing holes as fiducial marks. And then a laser diode chip is picked and placed to the center of the metal base. However the image of the chamfered outer edge of the top surface of the metal base is blur for the PR system of the automatic equipment. The blur imaging introduces a significant error in finding the center of the metal base. When using the post-housing holes as fiducial marks, the sub-mount and/or the monitoring photodiode (PD) chip used may block a fraction of the holes. Therefore the PR system cannot find those fiducials unless a lower recognition threshold is used. The lower recognition threshold itself will introduce an uncertain error.  
           [0013]    In the second alignment step, a typical metal base  11  of prior art as shown in FIG. 1 a  and FIG. 1 b  comprises a mesa  18 , vertical side surface  13  of mesa  18 , and bottom flange  16 . A high-speed metal base  61  of prior art as shown in FIG. 6 a  and FIG. 6 b  comprises a mesa  65 , vertical side surface  68  of mesa  65 , and bottom flange  63 . High-speed metal base  61  is designed for 20 GHZ and higher.  
           [0014]    A typical window cap  301  of prior art as shown in FIG. 30 comprises a vertical inside surface  303 , foot  304 , and projection  305 . During welding process, foot  304  sits on bottom flange  16  of metal base  11  or bottom flange  63  of metal base  61 , mesa  18  or mesa  65  confine the position of window cap  301  to certain degree, and projection  305  will be melted to weld foot  304  of window cap  301  to the bottom flange of metal bases, either metal base  11  or high-speed metal base  61 .  
           [0015]    The combination of the mechanical tolerances of the window cap&#39;s inner diameter of vertical inside surface  303  and the outer diameter of vertical side surface  13  of mesa  18  or vertical side surface  68  of mesa  65  may introduces alignment error in the alignment of the window cap to the metal base. This error is too big to accept for high-speed applications and this is one of reasons why there is no low-cost high-speed laser diode package on current market (there is no 2.5 GHZ ball lens laser diode package on current market).  
           [0016]    In practice there is a strong need for new types of metal bases and window caps designed with features that can provide a self-alignment mechanism for semiconductor laser TO-can type of package and the like with lower cost and simple fabrication.  
           [0017]    (B). For Edge-Emitting Laser Type of Packages  
           [0018]    There are two main issues needed to be resolved for edge emitting laser package: (1) alignment between a metal base and a window cap; (2) wire bonding two surfaces they are not on the same plane.  
           [0019]    [0019]FIG. 10 is a typical drawing of prior art of the metal base for an edge-emitting laser diode (LD) package. Similar to VCSEL package, there is an alignment issue for edge emitting laser diode package. Unlike the metal bases for VCSEL package, there is no mesa sitting on the top surface of bottom flange  104  for edge emitting laser diode package. A window cap is directly welded onto the top surface of bottom flange  104 . Therefore there is no physical surface to confine the position of a window cap and makes the alignment more difficult. Active alignment method is employed for only aligning x-y position at TO can package level.  
           [0020]    Therefore there is also a strong need for new types of metal bases and window caps designed with features that can provide a self-alignment mechanism for edge emitting laser TO-can type package and the like with lower cost and simple fabrication.  
           [0021]    At the center portion of the bottom flange, there is an area that is at an angle to the top surface of the bottom flange, hereafter called tilted area, as shown in FIG. 22. Typically the tilted area is for mounting PD monitoring chip.  
           [0022]    There is another structure for mounting PD monitoring chip that is to use a post with bent and flattened top portion, hereafter called L post, as shown in FIG. 10 prior art.  
           [0023]    There are three kinds of commonly used metal basest, type A, B, and C. Type A and B comprise a cylinder shape post with the top surface approximately parallels to the top surface of the bottom flange, hereafter called post, and a post with the top portion flattened, hereafter called flattened-top post. Type C, as shown in FIG. 16 and FIG. 22, comprises two of flattened-top posts. The flattened top surface of flattened-top posts approximately parallel to the vertical side surface of the pedestal. Laser chip is mounted on the vertical side surface of the pedestal.  
           [0024]    For type C metal base, laser chip is bonded to the two flattened-top posts without needing to rotate the metal base. The PD chip need to be bonded to the flattened top surface of one of flattened-top posts. Therefore the metal base needs to be rotating during bonding the same wire.  
           [0025]    For Type A and B metal bases, the top surface of monitoring PD chip is bonded to either the top surface of the post, or the flattened top surface of the flattened-top post. The laser chip is wire bonded to both the flattened surface of the flattened-top post and the top surface of the post. Rotating the metal base is needed during the bonding process.  
           [0026]    For manual wire bonding, rotating the metal base is time consuming. For an automatic wire bonder, rotating the metal base is a very expensive function.  
           [0027]    Therefore a new type of metal bases is needed to eliminate the need of rotation.  
         BRIEF SUMMARY OF THE INVENTION  
         [0028]    In the present invention, (1) metal bases and window caps with self-alignment structure for self-aligning a window cap to a metal base are disclosed; (2) metal bases with new features for the pattern recognition (PR) system of automatic equipment to find the center of the metal base are disclosed; (3) Metal bases with a post having two bonding surfaces for reliably wire bonding without rotating the metal base between two wire bonding steps are disclosed.  
           [0029]    There are at least two fiducial marks on the top surface of mesa of metal bases of this invention. Those fiducial marks are for the PR system of an automatic equipment to find the center of a metal base. The edge of the top surface of the mesa of the metal base is sharp and flat, i.e., the edge is non-chamfered. This feature is also for the PR system of automatic equipment to accurately find the center of the metal base. Therefore automatic equipment can place laser diode chips or dispense adhesive accurately.  
           [0030]    Both the inside surface of a window cap and the side surface of the mesa of a metal base of this invention are tapered to the approximately same angle so that the tapered window cap will be self-aligned to the tapered metal base when the window cap is placed on the metal base.  
           [0031]    A post of a metal base of the present invention comprises two bonding surfaces, one surface is approximately parallel to the laser chip that is mounted to the vertical surface of the pedestal, another surface is approximately parallel to the monitoring PD chip which is mounted on either tilted area or L post or the like.  
           [0032]    The top surface of a post of the present invention is tilted so that the tilted top surface of the post is approximately parallel to the top surface of the L post, which is commonly used to hold the monitoring PD chip. With these features, a regular wire bonder can reliably bond the wire to both surfaces without rotating the metal base after first bond.  
           [0033]    The primary object of the present invention is to provide new types of metal bases and window caps comprising features such that the window cap will accurately self-align to the metal base, and therefore high-speed laser diode package with or without connecting to optical fiber will be manufactured with high yield and high throughput.  
           [0034]    The second object of this invention is to provide new types of metal base comprising features such that a laser diode chip can be accurately placed onto it.  
           [0035]    The third object of the present invention is to provide new types of metal base with features such that the wire bonding process is reliable and inexpensive.  
           [0036]    Further objects and advantages of the present invention will become apparent from a consideration of the ensuing description and drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF DRAWINGS  
       [0037]    The novel features believed characteristic of the present invention are set forth in the claims. The invention itself, as well as other features and advantages thereof will be best understood by referring to detailed descriptions that follow, when read in conjunction with the accompanying drawings, wherein:  
         [0038]    [0038]FIG. 1 a  is a partially sectional view of metal base  11  of a typical prior art.  
         [0039]    [0039]FIG. 2 b  is a top view of metal base  11 .  
         [0040]    [0040]FIG. 2 is a partially sectional view of tapered metal base  21  showing a preferred embodiment of the present invention.  
         [0041]    [0041]FIG. 3 is a partially sectional view of tapered metal base  31  showing a preferred embodiment of the present invention.  
         [0042]    [0042]FIG. 4 is a top view of metal base  41  with fiducial marks showing a preferred embodiment of the present invention.  
         [0043]    [0043]FIG. 5 a  is a top view of metal base  51  with fiducial marks showing a preferred embodiment of the present invention.  
         [0044]    [0044]FIG. 5 b  is a top view of metal base  55  with fiducial marks showing a preferred embodiment of the present invention.  
         [0045]    [0045]FIG. 6 a  is a sectional view of high-speed metal base  61  of prior art.  
         [0046]    [0046]FIG. 6 b  is a top view of high-speed metal base  61  of prior art.  
         [0047]    [0047]FIG. 7 is a sectional view of tapered high-speed metal base  71  showing a preferred embodiment of the present invention.  
         [0048]    [0048]FIG. 8 is a sectional view of tapered high-speed metal base  81  showing a preferred embodiment of the present invention.  
         [0049]    [0049]FIG. 9 a  is a top view of high-speed metal base  91  with fiducial marks showing preferred embodiment of the present invention.  
         [0050]    [0050]FIG. 9 b  is a top view of high-speed metal base  93  with fiducial marks showing preferred embodiment of the present invention.  
         [0051]    [0051]FIG. 9 c  is a top view of high-speed metal base  94  with fiducial marks showing preferred embodiment of the present invention.  
         [0052]    [0052]FIG. 10 a  is a sectional view of metal base  101  of prior art.  
         [0053]    [0053]FIG. 10 b  is the top view of metal base  101 .  
         [0054]    [0054]FIG. 10 c  is the sectional view of the metal base  101 .  
         [0055]    [0055]FIG. 11 is a sectional view of tapered metal base  111  showing a preferred embodiment of the present invention.  
         [0056]    [0056]FIG. 12 a  is a sectional view of metal base  121  showing a preferred embodiment of the present invention.  
         [0057]    [0057]FIG. 12 b  is the top view of metal base  121 .  
         [0058]    [0058]FIG. 12 c  is the sectional view of the metal base  121 .  
         [0059]    [0059]FIG. 13 a  is a sectional view of metal base  131  showing a preferred embodiment of the present invention.  
         [0060]    [0060]FIG. 13 b  is the top view of metal base  131 .  
         [0061]    [0061]FIG. 13 c  is the sectional view of the metal base  131 .  
         [0062]    [0062]FIG. 14 a  is a sectional view of metal base  141  showing a preferred embodiment of the present invention.  
         [0063]    [0063]FIG. 14 b  is the top view of metal base  141 .  
         [0064]    [0064]FIG. 14 c  is the sectional view of the metal base  141 .  
         [0065]    [0065]FIG. 15 is a sectional view of tapered metal base  151  showing a preferred embodiment of the present invention.  
         [0066]    [0066]FIG. 16 a  is a sectional view of metal base  161  of prior art.  
         [0067]    [0067]FIG. 16 b  is the top view of metal base  161 .  
         [0068]    [0068]FIG. 16 c  is the sectional view of the metal base  161 .  
         [0069]    [0069]FIG. 17 is a sectional view of tapered metal base  171  showing a preferred embodiment of the present invention.  
         [0070]    [0070]FIG. 18 a  is a sectional view of metal base  181  showing a preferred embodiment of the present invention.  
         [0071]    [0071]FIG. 18 b  is the top view of metal base  181 .  
         [0072]    [0072]FIG. 18 c  is the sectional view of the metal base  181 .  
         [0073]    [0073]FIG. 19 a  is a sectional view of metal base  191  showing a preferred embodiment of the present invention.  
         [0074]    [0074]FIG. 19 b  is the top view of metal base  191 .  
         [0075]    [0075]FIG. 19 c  is the sectional view of the metal base  191 .  
         [0076]    [0076]FIG. 20 is a sectional view of tapered metal base  201  showing a preferred embodiment of the present invention.  
         [0077]    [0077]FIG. 21 is a sectional view of tapered metal base  211  showing a preferred embodiment of the present invention.  
         [0078]    [0078]FIG. 22 a  is a sectional view of metal base  221  of prior art.  
         [0079]    [0079]FIG. 22 b  is the top view of metal base  221 .  
         [0080]    [0080]FIG. 22 c  is the sectional view of the metal base  221 .  
         [0081]    [0081]FIG. 23 is a sectional view of tapered metal base  231  showing a preferred embodiment of the present invention.  
         [0082]    [0082]FIG. 24 a  is a sectional view of metal base  241  showing a preferred embodiment of the present invention.  
         [0083]    [0083]FIG. 24 b  is the top view of metal base  241 .  
         [0084]    [0084]FIG. 24 c  is the sectional view of the metal base  241 .  
         [0085]    [0085]FIG. 25 is a sectional view of tapered metal base  251  showing a preferred embodiment of the present invention.  
         [0086]    [0086]FIG. 26 is a sectional view of metal base  261  showing a preferred embodiment of the present invention.  
         [0087]    [0087]FIG. 27 a  is a sectional view of metal base  271  showing a preferred embodiment of the present invention.  
         [0088]    [0088]FIG. 27 b  is a top view of metal base  271 .  
         [0089]    [0089]FIG. 27 c  is a sectional view of metal base  271 .  
         [0090]    [0090]FIG. 28 is a sectional view of tapered metal base  281  showing a preferred embodiment of the present invention.  
         [0091]    [0091]FIG. 29 is a sectional view of tapered metal base  291  showing a preferred embodiment of the present invention.  
         [0092]    [0092]FIG. 30 a  is a sectional view of ball lens window cap  301  of prior art.  
         [0093]    [0093]FIG. 30 b  is a partially sectional view of ball lens window cap  309 , which has an irregular ball lens, of prior art.  
         [0094]    [0094]FIG. 31 is a sectional view of tapered ball lens window cap  311  showing a preferred embodiment of the present invention.  
         [0095]    [0095]FIG. 32 is a sectional view of tapered ball lens window cap  321  showing a modification of tapered ball lens window cap  311 .  
         [0096]    [0096]FIG. 33 is a sectional view of tapered ball lens window cap  331  showing a modification of tapered ball lens window cap  311 .  
         [0097]    [0097]FIG. 34 is a sectional view of partially tapered ball lens window cap  341  showing a preferred embodiment of the present invention.  
         [0098]    [0098]FIG. 35 is a sectional view of partially tapered ball lens window cap  351  showing a modification of partially tapered ball lens window cap  341 .  
         [0099]    [0099]FIG. 36 is a sectional view of partially tapered ball lens window cap  361  showing a modification of partially tapered ball lens window cap  341 .  
         [0100]    [0100]FIG. 37 is a sectional view of tapered ball lens window cap  371  with partially tapered inside surface showing a preferred embodiment of the present invention.  
         [0101]    [0101]FIG. 38 is a sectional view of tapered ball lens window cap  381  with partially tapered inside surface showing a modification of tapered ball lens window cap  371 .  
         [0102]    [0102]FIG. 39 is a sectional view of tapered ball lens window cap  391  with partially tapered inside surface showing a modification of tapered ball lens window cap  371 .  
         [0103]    [0103]FIG. 40 is a partially sectional view of flat window cap  401  of prior art.  
         [0104]    [0104]FIG. 41 is a sectional view of tapered flat window cap  411  showing a preferred embodiment of the present invention.  
         [0105]    [0105]FIG. 42 is a sectional view of tapered flat window cap  421  showing a modification of tapered flat window cap  411 .  
         [0106]    [0106]FIG. 43 is a sectional view of tapered flat window cap  431  showing a modification of partially tapered flat window cap  411 .  
         [0107]    [0107]FIG. 44 is a sectional view of partially tapered flat window cap  441  showing a preferred embodiment of the present invention.  
         [0108]    [0108]FIG. 45 is a sectional view of partially tapered flat window cap  451  showing a modification of partially tapered flat window cap  441 .  
         [0109]    [0109]FIG. 46 is a sectional view of partially tapered flat window cap  461  showing a modification of tapered flat window cap  441 .  
         [0110]    [0110]FIG. 47 is a sectional view of tapered flat window cap  471  with partially tapered inside surface showing a preferred embodiment of the present invention.  
         [0111]    [0111]FIG. 48 is a sectional view of tapered flat window cap  481  with partially tapered inside surface showing a modification of tapered flat window cap  471 .  
         [0112]    [0112]FIG. 49 is a sectional view of tapered flat window cap  491  with partially tapered inside surface showing a modification of tapered flat window cap  471 .  
         [0113]    [0113]FIG. 50 is a partially sectional view of an assembly of tapered metal base  31  and tapered ball lens window cap  311  as a preferred embodiment of the present invention.  
         [0114]    [0114]FIG. 51 is a sectional view of an assembly of tapered metal base  201  and tapered ball lens window cap  311  as a preferred embodiment of the present invention.  
         [0115]    [0115]FIG. 52 is a partially sectional view of an assembly of tapered metal base  31  and tapered flat window cap  411  as a preferred embodiment of the present invention.  
         [0116]    [0116]FIG. 53 is a sectional view of an assembly of tapered metal base  201  and tapered flat window cap  411  as a preferred embodiment of the present invention.  
         [0117]    [0117]FIG. 54 is a partially sectional view of an assembly of tapered metal base  31  and tapered ball lens window cap  381  as a preferred embodiment of the present invention.  
         [0118]    [0118]FIG. 55 is a sectional view of an assembly of tapered metal base  211  and tapered ball lens cap  381  as a preferred embodiment of the present invention.  
         [0119]    [0119]FIG. 56 is a partially sectional view of an assembly of a prior art of a semiconductor laser diode package with a pigtail. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0120]    While embodiments of this invention will be described below, those skilled in the art will recognize that other structures and methods are capable of implementing the principles of this invention. Thus the following description is illustrative only and not limiting.  
         [0121]    Reference is specifically made to the drawings wherein like numbers are used to designate like members throughout.  
         [0122]    [0122]FIG. 1 a  is a partially sectional view of metal base  11  of prior art. Metal base  11  comprises post  14 , post housing  15 , bottom flange  16 , mesa  18  sitting on the top of bottom flange  16 , vertical side surface  13  of mesa  18 , top surface  17  of mesa  18 , and chamfered edge  12  intersecting top surface  17  and vertical side surface  13 . Post housing  15  are holes through metal base  11 . Through post housing  15  a plurality of posts is fixed by insulating material.  
         [0123]    [0123]FIG. 1 b  is a top view of metal base  11 . There is no fiducial mark on top surface  17 .  
         [0124]    It is a common and easy way to find the center of a metal base first, and use the center as a reference point to determine where to place a laser chip and/or to dispense epoxy. The positions of post  14  vary in post-housing  15  due to the manufacturing process of metal bases. Therefore post  14  cannot be used as fiducial marks for finding the center of metal bases.  
         [0125]    Both chamfered edge  12  and post housing  15  are commonly used by the pattern recognition (PR) system of automatic equipment as fiducial marks to find the center of metal bases. However, since both post housing  15  will be partially covered by a sub-mount or a monitoring photodiode (PD) chip and chamfered edge  12  will be blur for the PR system, the founded center of metal bases will not be accurate. And the placement of semiconductor laser-diode chip or the dispensing of epoxy will not be accurate.  
         [0126]    This kind of metal base is commonly used for vertical-cavity surface emitting laser (VCSEL) diode package and the like.  
         [0127]    [0127]FIG. 2 is a partially sectional view of tapered metal base  21 , comprising a mesa  25 , top surface  24  of mesa  25 , tapered side surface  22  of mesa  25 , bottom flange  16 , post housing  15 , post  14 , and non-chamfered edge  23  intersecting top surface  24  and tapered side surface  22 .  
         [0128]    Metal base  21  replaces mesa  18  having vertical side surface  13  in FIG. 1 a  with mesa  25  having tapered side surface  22 . Tapered side surface  22  works with a tapered window cap to provide a self-alignment means to align the tapered window cap to the tapered metal base. Therefore, the semiconductor laser chip that is aligned with the tapered metal base will accurately align to the tapered window cap automatically.  
         [0129]    [0129]FIG. 3 is a partially sectional view of metal base  31 , comprising a mesa  36 , top surface  37  of mesa  36 , tapered side surface  33  of mesa  36 , bottom flange  16 , step  32  surrounding top surface  37  and between top surface  37  and tapered side surface  33 , vertical side surface  38  of step  32 , post housing  15 , post  14 , and non-chamfered edge  34  intersecting top surface  37  and vertical side surface  38 .  
         [0130]    Metal base  31  adds a new feature, step  32 , to metal base  21 , which is for the PR system of automatic equipment to be able to find reference point accurately.  
         [0131]    [0131]FIG. 4 is a top view of metal base  41 , comprising bottom flange  16 , top surface  17 , and two of circular fiducial mark  42  on top surface  17 .  
         [0132]    Metal base  41  provides two fiducial marks on a diagonal line to metal base  11  of prior art, those fiducial marks are for the PR system of automatic equipment to be able to find reference point accurately.  
         [0133]    [0133]FIG. 5 a  is a top view of metal base  51 . Metal base  51  has the same sectional view as metal base  21  and comprises bottom flange  16 , top surface  24 , tapered side surface  22 , and two of square fiducial mark  52  on top surface  17 .  
         [0134]    [0134]FIG. 5 b  is a top view of metal base  55 . Metal base  55  has the same sectional view as metal base  31  and comprises bottom flange  16 , top surface  37 , tapered side surface  33 , the horizantal surface  54  of step  32 , and two of square fiducial mark  53  on top surface  37 .  
         [0135]    Although there are two of square fiducial marks  52  on top surface  24  in FIG. 5 a , two of square fiducial marks  53  on top surface  37  in FIG. 5 b , and two of circular fiducial marks  42  on top surface  17  in FIG. 4, the shape of fiducial marks is not limited to circular or square. Other shapes may be used as fiducial marks too. The number of fiducial marks needs to be at least two and they are on diagonal positions for orientation. Fiducial mark  42 ,  52  and  53  allow the PR system of automatic equipment to find the location for the placement of a laser chip or dispensing of epoxy on the metal base accurately.  
         [0136]    [0136]FIG. 6 a  is a sectional view of high-speed metal base  61  of prior art, comprising post  64 , post housing  62 , mesa  65 , bottom flange  63 , and top surface  66  of mesa  65 . Mesa  65  sits on the top of bottom flange  63  and has vertical side surface  68 . Chamfered edge  67  intersects top surface  66  and vertical side surface  68 . Since metal base  61  and the like are designed for high-speed application, the alignment is very critical.  
         [0137]    [0137]FIG. 6 b  is a top view of metal base  61 . There is no fiducial mark on top surface  66 .  
         [0138]    [0138]FIG. 7 is a sectional view of tapered high-speed metal base  71 , comprising mesa  75 , top surface  74  of mesa  75 , tapered side surface  72  of mesa  75 , bottom flange  63 , post housing  62 , post  64 , and non-chamfered edge  73  intersecting top surface  74  and tapered side surface  72 . Tapered high-speed metal base  71  has a new feature, tapered side surface, that provides self-alignment means for accurately aligning tapered high-speed metal base to tapered window cap.  
         [0139]    [0139]FIG. 8 is a sectional view of tapered high-speed tapered metal base  81 , comprising a mesa  87 , top surface  86  of mesa  87 , tapered side surface  82  of mesa  87 , bottom flange  63 , tapered side surface  82  is at an angle to the top surface of bottom flange  63 , step  84  surrounding top surface  86  and between top surface  86  and tapered side surface  82 , vertical side surface  83  of step  84 , post housing  62 , post  64 , edge  85  intersecting top surface  86  and vertical side surface  83 . High-speed metal base  81  shows a new feature, step  84 , added to tapered high-speed metal base  71 , that allow PR system of automatic equipment to find the center of metal base accurately.  
         [0140]    [0140]FIG. 9 a  is a top view of high-speed metal base  91 . Metal base  91  has the same sectional view as metal base  61  and comprises two of square fiducial mark  92  on top surface  66 . Two of fiducial mark  92  are on a diagonal line and are not limited to square shape. Metal base  91  shows a new feature, fiducial marks, added to high-speed metal base  61  of prior art.  
         [0141]    [0141]FIG. 9 b  is a top view of tapered high-speed metal base  93 . Metal base  93  has the same sectional view as metal base  71  and comprises two of square fiducial mark  92  on top surface  74 , bottom flange  63 , and tapered side surface  72 . Two of fiducial mark  92  are on a diagonal line and are not limited to square shape. Metal base  93  shows a new feature, fiducial marks, added to tapered high-speed metal base  71 .  
         [0142]    [0142]FIG. 9 c  is a top view of tapered high-speed metal base  94 . Metal base  94  has the same sectional view as metal base  81  and comprises two of square fiducial mark  92  on top surface  86 , bottom flange  63 , tapered side surface  82 , and the horizontal surface of step  84 . Two of fiducial mark  92  are on a diagonal line and are not limited to square shape. Metal base  94  shows a new feature, fiducial marks, added to tapered high-speed metal base  81 .  
         [0143]    The combination of step  84 , vertical side surface  83 , fiducial mark  92 , and edge  85  allows the PR system of automatic equipment to accurately find the center of metal bases. Therefore the placement of semiconductor laser diode chip or dispensing of epoxy onto metal bases will be accurate. Tapered side surface  82  allows a tapered window cap to align with the tapered high-speed metal bases.  
         [0144]    [0144]FIG. 10 a  is a sectional view of metal base  101  of prior art, comprising post  107 , top surface  106  of post  107 , bottom flange  104 , L post  102 , top surface  103  of L post  102 , pedestal  105  sitting on bottom flange  104 , and vertical side surface  108  of pedestal  105 . Top surface  103  is at an angle to the top surface of bottom flange  104 . Pedestal  105  is for mounting edge emitting laser diode chip.  
         [0145]    [0145]FIG. 10 b  is a top view of metal base  101 .  
         [0146]    [0146]FIG. 10 c  is a sectional view of metal base  101 , comprising flattened-top post  110 , flattened-top surface  109  of flattened-top post  110 . Flattened-top surface  109  approximately parallels to vertical side surface  108 .  
         [0147]    There are three different posts in FIG. 10, post  107 , flattened-top post  110 , and L post  102 . Although flattened-top post  110  is at the left-hand side of post  107  in FIG. 10 c , there is a different type of metal base for which flattened-top post and regular post switch their positions.  
         [0148]    Since a window cap will be welded directly to the top surface of bottom flange  104  and there is no mesa to confine the position of the window cap. Therefore, the alignment of a window cap to metal base  101  and the like, thus to the laser chip, will be very difficult to control. For accurate alignment of a window cap to this kind of metal base, active alignment method is employed, which is expensive and throughput is low.  
         [0149]    Top surface  106  is approximately parallel to the top surface of bottom flange  104 , but not approximately parallel to top surface  103 . This feature makes wire bonding difficult without rotating the metal base during wire bonding process.  
         [0150]    Metal base  101  is typically used for edge emitting laser diode (LD) packages and the like.  
         [0151]    [0151]FIG. 11 is a sectional view of tapered metal base  111 , comprising mesa  113 , tapered side surface  112  of mesa  113 , bottom flange  114 , pedestal  105 , and L post  102 . Mesa  113  sits on bottom flange  114 . Pedestal  105  sits on mesa  113 .  
         [0152]    Tapered side surface  112  will align with a tapered window cap with high accuracy when welding the tapered window cap to bottom flange  114  of metal base  111 .  
         [0153]    Metal base  111  adds a new structure, mesa  113  with tapered side surface  112 , to metal base  101  of prior art.  
         [0154]    [0154]FIG. 12 a  is a sectional view of metal base  121 , comprising bottom flange  104 , tilted-top post  124 , tilted-top surface  122  of tilted-top post  124 , and L post  102 . Pedestal  105  sits on bottom flange  104 . Tilted-top surface  122  of tilted-top post  124  is made in a way such that tilted-top surface  122  is approximately parallel to top surface  103  of L post  102 . This feature allows a wire to be reliably bonded to the two approximately parallel surfaces without rotating metal base during wire bonding process.  
         [0155]    [0155]FIG. 12 b  is a top view of metal base  121 .  
         [0156]    [0156]FIG. 12 c  is a sectional view of metal base  121 , comprising tilted-top post  124 .  
         [0157]    [0157]FIG. 12 d  is a detailed sectional view of the top portion of tilted-top post  124 , comprising key  123  and top surface  122  of tilted-top post  124 . Key  123  is on the top portion of tilted-top post  124  and is for properly orienting tilted-top post  124  in post-housing  125  such that tilted-top surface  122  is approximately parallel to top surface  103 .  
         [0158]    [0158]FIG. 13 a  is a sectional view of metal base  131 . Metal base  131  comprises a novel feature, two-bonding-surface post  134  which has bent-bonding-surface  133  and vertical-bonding surface  132 . Metal base  131  comprises also L post  102 , top surface  103  of L post  102 , bottom flange  104 , and pedestal  105 . Pedestal  105  sits on bottom flange  104 .  
         [0159]    [0159]FIG. 13 b  is a top view of metal base  131 .  
         [0160]    [0160]FIG. 13 c  is a sectional view of metal base  131 .  
         [0161]    Two-bonding-surface post  134  provides two surfaces for wire bonding, one is vertical-bonding surface  132  that is approximately parallel to vertical side surface  108 , another one is bent-bonding-surface  133  that is approximately parallel to top surface  103 . Bent-bonding-surface  133  is adjacent to vertical-bonding surface  132 .  
         [0162]    Metal base  131  replaces flattened-top-surface post  110  of metal base  101  with a new structure, two-bonding-surface post  134 .  
         [0163]    Therefore the wire bonding process, in which a wire is bonded to two approximately parallel surfaces, either bent-bonding surface  133  and top surface  103 , or vertical-bonding surface  132  and vertical side surface  108 , is reliable and there is no need to rotate the metal base after the wire is bonded to the first surface.  
         [0164]    [0164]FIG. 14 a  is a sectional view of metal base  141 , comprising two-bonding-surface post  144 , bent-bonding-surface  143  of two-bonding-surface post  144 , vertical-bonding surface  142  of two-bonding-surface post  144 , L post  102 , top surface  103  of L post  102 , bottom flange  104 , and pedestal  105 . Pedestal  105  sits on bottom flange  104 .  
         [0165]    [0165]FIG. 14 b  is a top view of metal base  141 .  
         [0166]    [0166]FIG. 14 c  is a sectional view of metal base  141 .  
         [0167]    Two-bonding-surface post  144  provides two surfaces for wire bonding, one is vertical-bonding surface  142  that is approximately parallel to vertical side surface  108 , another one is bent-bonding-surface  143  that is approximately parallel to top surface  103 . Bent-bonding-surface  143  is adjacent to vertical-bonding surface  142 .  
         [0168]    Two-bonding-surface post  144  of metal base  141  shows a different configuration of two-bonding-surface post  134 . The scope of two-bonding-surface post of the present invention should not be limited to those two configurations.  
         [0169]    [0169]FIG. 15 is a sectional view of tapered metal base  151 , comprising two-bonding-surface post  134 , bent-bonding-surface  133 , vertical-bonding surface  132 , L post  102 , top surface  103  of L post  102 , bottom flange  114 , mesa  113  with tapered side surface  112 , and pedestal  105 . Pedestal  105  sits on mesa  113 . Mesa  113  sits on bottom flange  114 .  
         [0170]    Metal base  151  shows a combination of two new structures, a mesa with tapered side surface and a two-bonding-surface post  
         [0171]    [0171]FIG. 16 a  is a sectional view of metal base  161  of prior art, typically called C type metal base, comprising flattened-top post  162 , flattened-top surface  163  of flattened-top post  162 , bottom flange  104 , top surface  103  of L post  102 , and pedestal  105  sits on bottom flange  104 .  
         [0172]    [0172]FIG. 16 b  is a top view of metal base  161 .  
         [0173]    [0173]FIG. 16 c  is a sectional view of metal base  161 , comprising flattened-top surface  163 , flattened-top post  162 , flattened-top post  165 , flattened top surface  164  of flattened-top post  165 , and vertical side surface  108  of pedestal  105 . Flattened-top surface  163 , flattened-top surface  164 , and vertical side surface  108  are approximately parallel to each other.  
         [0174]    [0174]FIG. 17 is a sectional view of metal base  171 , comprising mesa  174 , tapered side surface  173  of mesa  174 , bottom flange  172 , pedestal  105  with vertical side surface  108 , flattened-top post  162  with flattened-top surface  163 , and L post  102  with top surface  103 . Mesa  174  sits on bottom flange  172 . Pedestal  105  sits on mesa  174 .  
         [0175]    Metal base  171  adds a new structure, mesa  174  with tapered side surface  173 , to metal base  161  of prior art. Tapered side surface  173  aligns with a tapered window cap with high accuracy when welding the tapered window cap to bottom flange  172  of metal base  171 .  
         [0176]    [0176]FIG. 18 a  is a sectional view of metal base  181 , comprising two-bonding-surface post  184 , bent-bonding-surface  183  of two-bonding-surface post  184 , vertical-bonding surface  182  of two-bonding-surface post  184 , L post  102 , top surface  103  of L post  102 , bottom flange  104 , and pedestal  105 . Pedestal  105  sits on bottom flange  104 .  
         [0177]    [0177]FIG. 18 b  is a top view of metal base  181 .  
         [0178]    [0178]FIG. 18 c  is a sectional view of metal base  181 , comprising vertical side surface  108 , vertical-bonding surface  182 , and flattened top surface  164  of flattened-top post  165 .  
         [0179]    Two-bonding-surface post  184  provides two bonding surfaces for wire bonding, one is vertical-bonding surface  182  that is approximately parallel to vertical side surface  108 , another one is bent-bonding-surface  183  that is approximately parallel to top surface  103 . Bent-bonding-surface  183  is adjacent to vertical-bonding surface  182 .  
         [0180]    Metal base  181  replaces flattened-top post  164  with two-bonding-surface post  182 , but not limited to replace flattened-top post  162 . Metal base  181  may replaces flattened-top post  165  with a two-bonding-surface post.  
         [0181]    [0181]FIG. 19 a  is a sectional view of metal base  191 , comprising two-bonding-surface post  192 , bent-bonding-surface  193  of two-bonding-surface post  192 , vertical-bonding surface  194  of two-bonding-surface post  192 , L post  102 , top surface  103  of L post  102 , bottom flange  104 , and pedestal  105 . Pedestal  105  sits on bottom flange  104 .  
         [0182]    [0182]FIG. 19 b  is a top view of metal base  191 .  
         [0183]    [0183]FIG. 19 c  is a sectional view of metal base  191 , comprising vertical side surface  108  and flattened top surface  164  of flattened-top post  165 .  
         [0184]    Two-bonding-surface post  192  provides two surfaces for wire bonding, one is vertical-bonding surface  194  that is approximately parallel to vertical side surface  108 , another one is bent-bonding-surface  193  that is approximately parallel to top surface  103  of L post  102 . Bent-bonding-surface  193  is adjacent to vertical-bonding surface  194 .  
         [0185]    Two-bonding-surface post  192  shows a different configuration of two-bonding-surface post  184 . The scope of two-bonding-surface post of the present invention should not be limited to those two configurations.  
         [0186]    [0186]FIG. 20 is a sectional view of metal base  201 , comprising two-bonding-surface post  184 , bent-bonding-surface  183  of two-bonding-surface post  184 , vertical-bonding surface  182  of two-bonding-surface post  184 , L post  102 , top surface  103  of L post  102 , bottom flange  172 , mesa  174  with tapered side surface  173 , and pedestal  105 . Pedestal  105  sits on mesa  174 . Mesa  174  sits on bottom flange  172 .  
         [0187]    Metal base  201  shows a combination of two new structures, a mesa with tapered side surface and a two-bonding-surface post added to metal base  161  of prior art.  
         [0188]    [0188]FIG. 21 is a sectional view of metal base  211 , comprising two-bonding-surface post  192 , bent-bonding-surface  193  of two-bonding-surface post  192 , vertical-bonding surface  194  of two-bonding-surface post  192 , L post  102 , top surface  103  of L post  102 , bottom flange  172 , mesa  174  with tapered side surface  173 , and pedestal  105 . Pedestal  105  sits on mesa  174 . Mesa  174  sits on bottom flange  172 .  
         [0189]    [0189]FIG. 22 a  is a sectional view of metal base  221  of prior art. Metal base  221  comprises bottom flange  230 . Tilted area  222  is located at the center portion of bottom flange  230  and is at an angle with the top surface of bottom flange  230 . There are post  223  with top surface  224  and flattened-top post  225  with flattened-top surface  226 . Pedestal  229  sits on bottom flange  230 . Tilted area is commonly for mounting monitoring chip.  
         [0190]    [0190]FIG. 22 b  is a top view of metal base  221 .  
         [0191]    [0191]FIG. 22 c  is a sectional view of metal base  221  comprising flattened-top post  225  with flattened top surface  226  and flattened-top post  227  with flattened top surface  228 .  
         [0192]    Flattened-top surface  226  and flattened-top surface  228  are approximately parallel to each other.  
         [0193]    [0193]FIG. 23 is a sectional view of metal base  221 , comprising post  223 , flattened-top post  225 , bottom flange  234 , mesa  233  sitting on bottom flange  234 , pedestal  229  sitting on mesa  233 , tilted area  222 , and tapered side surface  232  of mesa  233 .  
         [0194]    Metal base  231  adds a new structure, mesa  233  with tapered side surface  232 , to metal base  221  of prior art.  
         [0195]    [0195]FIG. 24 a  is a sectional view of metal base  241 . Metal base  241  comprising bottom flange  243 , tilted area  222 . Post  242  has tilted top surface  244  that is approximately parallel to the top surface of tilted area  222 . This feature makes wire bonding robust without rotating metal base during wire bonding process.  
         [0196]    [0196]FIG. 24 b  is a top view of metal base  241  showing tilted area  222  and tilted top surface  244  of post  242 .  
         [0197]    [0197]FIG. 24 c  is a sectional view of metal base  241 .  
         [0198]    [0198]FIG. 25 is a sectional view of metal base  251 , comprising mesa  233  sitting on bottom flange  234  and having tapered side surface  232 , and tilted-top post  242  having tilted-top surface  244 . Metal base  251  has a combination of two new features provided in FIG. 23 and FIG. 24.  
         [0199]    [0199]FIG. 26 is a sectional view of metal base  261 , comprising bottom flange  230 , and pedestal  229  having a vertical side surface  265 . Two-bonding-surface post  262  has bent-bonding surface  263  and vertical-bonding surface  264  that is approximately parallel to vertical side surface  265 . The feature that the top surface of tilted area  222  and bent-bonding surface  263  are approximately parallel to each other makes wire bonding robust without rotating metal base during wire bonding process.  
         [0200]    Metal base  261  adds a new feature, two-bonding-surface post, to metal base  221  of prior art.  
         [0201]    [0201]FIG. 27 a  is a sectional view of metal base  271 . Pedestal  229  sits on bottom flange  230 . Two-bonding-surface post  272  has vertical-bonding surface  273  that is approximately parallel to the vertical side surface of pedestal  229  and tilted-top surface  274  that is approximately parallel to the top surface of tilted area  222 .  
         [0202]    [0202]FIG. 27 b  is a top view of metal base  271  comprising tilted area  222  and tilted-top surface  274 .  
         [0203]    [0203]FIG. 27 c  is a sectional view of metal base  271 . Flattened-top surface  226  of flattened-top post  225 , vertical side surface  265  of pedestal  229 , and vertical-bonding surface  273  are approximately parallel to each other.  
         [0204]    Metal base  271  provides a two-bonding-surface post with different configuration to metal base  221  of prior art.  
         [0205]    [0205]FIG. 28 is a sectional view of metal base  281 . Pedestal  229  sits on mesa  233  that sits on bottom flange  234 . Pedestal  229  has vertical side surface  265 . Mesa  233  has tapered side surface  232 . Two-bonding-surface post  262  has both vertical-bonding surface  264  that is approximately parallel to vertical side surface  265  and bent-bonding surface  263  that is approximately parallel to the top surface of tilted area  222 . Tilted-top surface  244  of tilted top post  242  is approximately parallel to the top surface of tilted area  222 .  
         [0206]    Metal base  281  has three new structures, mesa  233  with tapered side surface  232 , two-bonding-surface post  262 , and tilted-top surface  244 , added to metal base  221  of prior art.  
         [0207]    [0207]FIG. 29 is a sectional view of metal base  291 . Pedestal  229  sits on mesa  233  that sits on bottom flange  234 . Mesa  233  has tapered side surface  232 . Two-bonding-surface post  272  has both vertical-bonding surface  273  that is approximately parallel to the vertical side surface of pedestal  229  and tilted-top surface  274  that is approximately parallel to the top surface of tilted area  222 . Tilted-top surface  244  of tilted top post  242  is approximately parallel to the top surface of tilted area  222 .  
         [0208]    The novel feature, a post has two bonding surfaces, of the present invention is set forth in the claim. FIGS. 13, 14,  15 ,  18 ,  19 ,  20 ,  21 ,  26 ,  27 ,  28 , and  29  are examples of a post having two bonding surfaces for wire bonding. The two bonding surfaces on the same post may have different shapes, forms, and positions.  
         [0209]    [0209]FIG. 30 a  is a sectional view of window cap  301  of prior art, comprising vertical inside surface  303 , vertical outside surface  302 , foot  304 , ball lens  306 , and projection  305 . Hereafter call the portion near ball lens as the top portion, the portion near the foot as the bottom portion.  
         [0210]    [0210]FIG. 30 b  is a sectional view of window cap  309  of prior art. The ball lens has large radius  308  for top half of the ball lens and small radius  307  for bottom half. All of new structures/features of the present invention for ball lens window cap apply to window cap  309 . Ball lens window caps with perfectly spherical ball lens are employed for the drawings of the ball lens window caps of the present invention.  
         [0211]    When welding window cap  301  of prior art to metal bases of prior art, projection  305  will sit on the top surface of the bottom flange and melt to weld foot  304  to the bottom flange. The alignment of window cap  301  to metal bases is dependent on the following factors:  
         [0212]    (1) Alignment between top and bottom electrodes of welding equipment, which is not accurate enough for high-speed semiconductor laser diode package;  
         [0213]    (2) The difference between the diameter of vertical outside surface  302  of window cap  301  and the inner diameter of the top electrode of welding equipment is too big for laser diode package;  
         [0214]    (3) How accurate the bottom electrode of welding equipment can hold metal bases, which is loose for high-speed semiconductor laser diode package; and  
         [0215]    (4) The different between the outer diameter of a mesa and the diameter of the vertical inside surface  303 .  
         [0216]    When welding window cap  301  of prior art to metal base  11  of prior art, the combination of the tolerance of the diameter of vertical inside surface  303  of window cap  301  and the tolerance of the outer diameter of mesa  18  of metal base  11  is so big that the alignment of the window cap to the metal base is not accurate enough for high-speed laser diode package. This is one of main reasons that there is no high-speed laser diode package with ball lens window caps.  
         [0217]    [0217]FIG. 31 is a sectional view of tapered window cap  311 , comprising ball lens  306 , foot  304 , and projection  305  located under foot  304 . Tapered inside surface  313  is from the top of window cap  311  to foot  304 . Tapered outside surface  312  is from the top of window cap  311  to the top surface of foot  304 . Projection may have variety of shapes.  
         [0218]    The angle of tapered inside surface  312  matches the angle of the tapered side surface of the mesa of a metal base so that tapered window cap will self-align to the tapered metal base. Therefore the laser diode chip will automatically align to the tapered window cap, since the laser diode chip has been aligned to the metal base during pick-place process.  
         [0219]    [0219]FIG. 32 is a sectional view of tapered window cap  321 , comprising ball lens  306 , foot  304 , and tapered inside surface  313 . Projection  322  is located on the bottom portion of tapered inside surface  313 . The bottom portion of tapered inside surface  313  is near foot  304 .  
         [0220]    During the active alignment process, it may be required to tilt a window cap to optimize the output of laser light beam. Projection  322  working with the tapered side surface of the mesa of metal bases meets the requirement.  
         [0221]    [0221]FIG. 33 is a sectional view of tapered window cap  331 , comprising ball lens  306 , foot  304 , tapered outside surface  312 , and tapered inside surface  313 . There is no projection on window cap  331 .  
         [0222]    [0222]FIG. 34 is a sectional view of partially tapered window cap  341 , comprising ball lens  306 , foot  304 , projection  305  located under foot  304 . Tapered inside surface  342  is at the bottom portion of window cap  341 . Vertical inside surface  343  is adjacent/above tapered inside surface  342 .  
         [0223]    The dimensions of tapered inside surface  342  and vertical inside surface  343  are not to scale.  
         [0224]    The angle of tapered inside surface  342  matches the angle of the tapered side surface of the mesa of a metal base so that tapered window cap will self align to the tapered metal base. Therefore the laser diode chip will automatically align to the tapered window cap.  
         [0225]    [0225]FIG. 35 is a sectional view of partially tapered window cap  351 , comprising ball lens  306 , foot  304 , tapered inside surface  342 . Vertical inside surface  343  is adjacent/above tapered inside surface  342 . Projection  322  is located on the bottom portion of tapered inside surface  342 . Projection  322  is no limited to the shape in FIG. 35.  
         [0226]    [0226]FIG. 36 is a sectional view of partially tapered window cap  361 , comprising ball lens  306 , foot  304 , and tapered inside surface  342 . Vertical inside surface  343  is adjacent/above tapered inside surface  342 . There is no projection for window cap  361 .  
         [0227]    [0227]FIG. 37 is a sectional view of tapered window cap  371 , comprising ball lens  306 , and foot  304 . Tapered inside surface  372  is located at the bottom portion of tapered window cap  371 . Vertical inside surface  373  is adjacent/above tapered inside surface  372 . Vertical outside surface  374  is from the top of window cap to foot  304 . Projection  305  is located under foot  304 .  
         [0228]    Vertical outside surface  374  is easy to interface with other fiber optical devices/connectors.  
         [0229]    [0229]FIG. 38 is a sectional view of tapered window cap  381 , comprising ball lens  306 , and foot  304 . Tapered inside surface  372  is located at the bottom portion of tapered window cap  381 . Vertical inside surface  373  is adjacent/above tapered inside surface  372 . Vertical outside surface  374  is from the top of tapered window cap  381  to foot  304 . Projection  322  is located at the bottom portion of tapered inside surface  372 .  
         [0230]    [0230]FIG. 39 is a sectional view of tapered window cap  391 , comprising ball lens  306 , and foot  304 . Tapered inside surface  372  is located at the bottom portion of window cap  391 . Vertical inside surface  373  is adjacent/above tapered inside surface  372 . Vertical outside surface  374  is from the top of window cap  391  to foot  304 . There is no projection.  
         [0231]    The angle of tapered inside surface  372  of tapered window cap  371 ,  381 , and  391  matches the angle of the tapered side surface of the mesa of a tapered metal base so that tapered window cap will self align to the tapered metal base. Therefore the laser diode chip will automatically align to tapered window cap.  
         [0232]    [0232]FIG. 40 is a partially sectional view of flat window cap  401  of prior art, comprising vertical inside surface  403 , vertical outside surface  404 , foot  402 , and flat window  405 .  
         [0233]    The alignment of a flat window cap to a metal base is not as critical as a ball lens cap. However, when connecting an optical fiber to a flat window package, the alignment of the flat window cap to the metal base is still important. Because the optical fiber will be aligned to the window cap and the laser chip has been aligned to the metal base, the window cap needs to be aligned with the metal base. Otherwise the optical fiber will have problem to couple the laser light.  
         [0234]    [0234]FIG. 41 is a sectional view of tapered window cap  411 . Tapered window cap  411  has flat window  405  and foot  402 . Tapered inside surface  414  is tapered from the top of tapered window cap  411  to foot  402 . Projection  412  is under foot  402 .  
         [0235]    [0235]FIG. 42 is a sectional view of tapered window cap  421 . Tapered window cap  421  has flat window  405  and foot  402 . Tapered inside surface  414  and tapered outside surface  413  are tapered from the top of tapered window cap  421  to foot  402 . Projection  422  is located on the bottom portion of tapered inside surface  414 , which is near foot  402 .  
         [0236]    [0236]FIG. 43 is a sectional view of tapered window cap  431 , comprising tapered inside surface  414 , flat window  405 , foot  402 . There is no projection.  
         [0237]    [0237]FIG. 44 is a sectional view of partially tapered window cap  441 . Partially tapered window cap  441  comprises flat window  405 , foot  402  and projection  412  located under foot  402 . Vertical inside surface  443  is adjacent/above to tapered inside surface  442 . The dimensions of tapered inside surface  442  and vertical inside surface  443  are not to scale.  
         [0238]    [0238]FIG. 45 is a sectional view of partially tapered window cap  451 . Tapered inside surface  442  is adjacent/below to vertical inside surface  443 . Partially tapered window cap  451  comprises flat window  405  and foot  402 . Projection  422  is located on the bottom portion of tapered inside surface  442 , which is near foot  402 .  
         [0239]    [0239]FIG. 46 is a sectional view of partially tapered window cap  461 . Tapered inside surface  442  is adjacent to vertical inside surface  443  that is above tapered inside surface  442 . Partially tapered window cap  461  comprises flat window  405  and foot  402 . There is no projection.  
         [0240]    [0240]FIG. 47 is a sectional view of tapered window cap  471 . Tapered window cap  471  comprises flat window  405  and foot  402 . Tapered inside surface  473  is partial of entire inside surface. Vertical inside surface  472  is adjacent and above tapered inside surface  473 . Vertical outside surface  404  is from the top that is near flat window  405  to foot  402 . Projection  412  is located under foot  402 .  
         [0241]    [0241]FIG. 48 is a sectional view of tapered window cap  481 . Tapered window cap  481  comprises flat window  405  and foot  402 . Vertical inside surface  472  is adjacent and above tapered inside surface  473 . Vertical outside surface  404  is from the top that is near flat window  405  to foot  402 . Projection  422  is located on the bottom portion of tapered inside surface  473 .  
         [0242]    [0242]FIG. 49 is a sectional view of tapered window cap  491 . Tapered window cap  491  comprises flat window  405  and foot  402 . Tapered inside surface  473  is partial of entire inside surface. Vertical inside surface  472  is adjacent and above tapered inside surface  473 . Vertical outside surface  404  is from the top that is near flat window  405  to foot  402 . There is no projection for window cap  491 .  
         [0243]    The angle of tapered inside surface  473  of tapered window cap  471 ,  481 , and  491  match the angle of the tapered side surface of the mesa of tapered metal bases of the present invention so that tapered window cap will self-align to the tapered metal bases. Therefore the laser diode chip will automatically align to tapered window cap.  
         [0244]    [0244]FIG. 50 is a partially sectional view of an assembly of tapered metal base  51  and tapered window cap  311 .  
         [0245]    Non-chamfered edge  34  and fiducial mark  53  (shown in FIG. 5 b ) allow PR system of automatic equipment to accurately find the center of metal base  51  and place laser diode chip accordingly.  
         [0246]    Tapered side surface  33  of tapered metal base  51  and tapered inside surface  313  of tapered window cap  311  match to each other and, thus, allow window cap  311  to self-align to tapered metal base  51 . Therefore laser diode is accurately aligned to window cap by a passive way.  
         [0247]    [0247]FIG. 51 is a sectional view of an assembly of tapered metal base  201  and tapered window cap  311 .  
         [0248]    Tapered side surface  173  of tapered metal base  201  matches tapered inside surface  313  of tapered window cap  311 , so that tapered window cap  311  is self aligned to tapered metal base  201 .  
         [0249]    [0249]FIG. 52 is a sectional view of an assembly of tapered metal base  31  and tapered window cap  411 .  
         [0250]    Tapered side surface  33  of tapered metal base  31  and tapered inside surface  414  of tapered window cap  411  match to each other and, thus, allow tapered window cap  411  to self-align to tapered metal base  31 . Therefore laser diode is accurately aligned to window cap by a passive way.  
         [0251]    [0251]FIG. 53 is a sectional view of an assembly of tapered metal base  201  and tapered window cap  411 .  
         [0252]    Tapered side surface  173  of tapered metal base  201  and tapered inside surface  414  of tapered window cap  411  match to each other and, thus, allow tapered window cap  411  to self-align to tapered metal base  201 . Therefore laser diode is accurately aligned to window cap by a passive way.  
         [0253]    [0253]FIG. 54 is a sectional view of an assembly of tapered metal base  31  and tapered window cap  381 .  
         [0254]    Tapered side surface  33  of tapered metal base  31  and tapered inside surface  372  of tapered window cap  381  match to each other and, thus, allow tapered window cap  381  to self-align to tapered metal base  31 . Therefore laser diode is accurately aligned to window cap by a passive way  
         [0255]    [0255]FIG. 55 is a sectional view of an assembly of tapered metal base  211  and tapered window cap  381 .  
         [0256]    Tapered side surface  173  of tapered metal base  211  and tapered inside surface  372  of tapered window cap  381  match to each other and, thus, allow tapered window cap  381  to self-align to tapered metal base  211 . Therefore laser diode is accurately aligned to window cap by a passive way.  
         [0257]    Further more, the active alignment procedure of connecting an optical fiber to the laser diode packages of the present invention, for examples as shown in FIGS.  50 - 55 , will be fast and have high yield, i.e., increasing throughput. Also metal bases and window caps of this invention allow people to build high-speed semiconductor laser packages with high yield without using expensive equipment.  
         [0258]    [0258]FIG. 50 to FIG. 55 are six examples of preferred embodiments of semiconductor laser diode package using different combinations of metal bases and window caps of the present invention. Semiconductor laser diode packages of other combinations of metal bases and window caps of the present invention are legal equivalents of the present invention.  
         [0259]    By controlling how far a tapered window cap is pushed toward to a tapered metal base of the present invention during welding process, the distance between the ball lens and the metal base is accurately controlled.  
         [0260]    [0260]FIG. 56 is a partially sectional view of an assembly  561  of semiconductor laser diode package with a pigtail of prior art, comprising pigtail  562 , ball lens  563 , window cap  564 , laser diode chip  565 , top surface  566 , and metal base  567 .  
         [0261]    Although the description above contains many specifications, these should not be construed as limiting the scope of the present invention but as merely providing illustrations of some of the presently preferred embodiments of the present invention.  
         [0262]    Therefore the scope of the present invention should be determined by the claims and their legal equivalents, rather than by the examples given.