Patent Publication Number: US-6668125-B2

Title: Lead frame, optical module, and a method of optical module

Description:
This application is a divisional of U.S. application Ser. No. 09/267,617, filed Mar. 15, 1999, patented U.S. Pat. No. 6,377,742. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a lead frame applicable to a resin-encapsulated optical module, an optical module employing this lead module, and a method of making the optical module. 
     2. Related Background Art 
     Researches and developments are being made in optical modules in which an optical fiber, a ferrule, and a semiconductor optical device are mounted on a substrate, bonded onto a lead frame, and then resin-encapsulated by transfer molding. There have been no reports in conferences or the like concerning a mass production method in which a highly reliable optical module can be made. 
     SUMMARY OF THE INVENTION 
     Such an optical module comprises an optical fiber, a ferrule, a semiconductor laser diode, a substrate, and a resin body. The substrate is formed with an optical fiber support groove for supporting the optical fiber, and a ferrule support groove for supporting the ferrule. On the substrate, the optical fiber is provided in the optical fiber support groove, the ferrule is provided in the ferrule support groove, and the semiconductor laser diode is provided so as to be optically coupled to the optical fiber. After this substrate is bonded on the lead frame, wire bondings are made. After the resulting assembly is subsequently resin-encapsulated, the lead frame is cut, and the leads are bent. As a result, the finished optical module is provided. 
     FIG. 1 is a plan view of a lead frame that can be applied to such an optical module. The lead frame  90  comprises an island  93  and support portions  94 . The above-mentioned substrate is mounted on the island  93 . Each support portion  94  connects the island  93  to either a frame  91  or a tie bar  92 , thereby supporting the island  93 . The support portions  94  extend from three sides of the island  93  in the respective directions perpendicular to their corresponding sides, thereby reaching either the frame  91  or tie bars  92 . 
     In a method of making the optical module, an optical module principal portion mounted with the ferrule is bonded to the island. For resin encapsulating the optical module principal portion and the lead frame, the lead frame mounted with the optical module principal portion is placed in an encapsulating die so as to be resin-encapsulated. 
     Having studied this optical module, the inventor has found the following points. 
     Since the island is supported by the support portions extending along three respective directions, the island does not have a sufficient flexibility with respect to the outer frame of the lead frame. When the lead frame is placed in the encapsulating die, care must be taken so that no force is applied from the encapsulating die to the ferrule mounted on the optical module principal portion. It is necessary that the lead frame is placed in the encapsulating die after the optical module principal portion is correctly aligned with the lead frame and then bonded to it. Otherwise, it is necessary that the optical module principal portion is correctly aligned with the lead frame on the encapsulating die. This procedure needs much time for aligning the optical module principal portion. 
     It is an object of the present invention to provide a lead frame which can reduce the force applied to the ferrule from an encapsulating die, an optical module made with this lead frame, and a method of making this optical module. 
     The lead frame in accordance with the present invention is utilized for mounting an optical module principal portion. The optical module principal portion includes an optical module substrate. Placed on the substrates are an optical fiber, a ferrule, and a semiconductor optical device optically coupled to the optical fiber. The lead frame comprises an island portion, a frame portion, and an island support portion. The island portion is provided so as to mount the optical module principal portion such that the ferrule aligns with a predetermined axis. The frame portion is provided so as to support the island portion. The island support portion is provided so as to connect the island portion and the frame portion to each other, and has a plurality of bent portions. The island support portion extends from the island portion and bends at a plurality of positions, so as to reach the frame portion. As a consequence, when the optical module principal portion is resin-encapsulated using an encapsulating die, the misalignment between the ferrule mounted on the substrate and the encapsulating die can be reduced by the island support portion. 
     The lead frame in accordance with the present invention can further comprise a substrate support portion provided so as to support the optical module principal portion mounted on the island portion. The substrate support portion is separated from the island portion. The island portion has a notch, whereas the end of the substrate support portion is positioned within the notch. Also, the lead frame in accordance with the present invention can comprise a pair of substrate support portions. The pair of substrate support portions can be arranged such that the predetermined axis is provided between the pair of substrate support portions. 
     Various kinds of arrangements can be applied to the island support portion of the lead frame in accordance with the present invention as follows. The island support portion can comprise a first part extending from the island portion in a direction intersecting the predetermined axis, a second part extending from the first part along the predetermined axis, and a third part extending from the second part in a direction intersecting the predetermined axis. Alternatively, the island support portion can comprise a fourth part extending from the island portion along the predetermined axis, a fifth part extending from the fourth part in a direction intersecting the predetermined axis, and a sixth part extending from the fifth part along the predetermined axis. The island support portion can include a part thinner than the island portion. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a plan view of a lead frame; 
     FIG. 2 shows an optical module substrate formed with grooves; 
     FIG. 3 shows the optical module substrate; 
     FIG. 4 shows the substrate during a step of mounting an optical device thereon; 
     FIG. 5 is a view showing a step of providing the substrate with an optical fiber; 
     FIG. 6A shows an optical module principal portion, FIG. 6B shows an optical fiber secured to an optical fiber support groove, and FIG. 6C shows a ferrule secured to a ferrule support groove; 
     FIG. 7 shows a step of assembling the optical module principal portion on a lead frame; 
     FIG. 8 shows a step of dropping a resin onto the optical module principal portion; 
     FIG. 9 is a plan view of a lead frame in accordance with the present invention; 
     FIG. 10 is a plan view of a lead frame in accordance with another embodiment of the present invention; 
     FIG. 11 is a plan view showing a lead frame in accordance with still another embodiment of the present invention; 
     FIG. 12 is a plan view showing the lead frame of FIG. 9 mounted with the optical module principal portion of FIG. 6A; 
     FIG. 13 is a perspective view showing a transfer-molding die; 
     FIG. 14 is a perspective view showing the lead frame of FIG. 12 on which the transfer-molding die of FIG. 13 is provided; 
     FIG. 15 is a plan view showing the lead frame encapsulated with a molding resin; 
     FIG. 16 is a perspective view showing the finished optical module; and 
     FIG. 17 is a perspective view of another optical module principal portion to which the lead frame of the present invention is applicable. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiments of the present invention will be explained with reference to the accompanying drawings. Parts identical or similar to each other will be referred to with the identical numerals or letters if possible, without repeating their overlapping descriptions. 
     FIG. 2 is a view showing an optical module substrate. The substrate  2  comprises a first region  2   a , a second region  2   b , and a third region  2   c  along a predetermined axis  3 . 
     The first region  2   a  is provided with a ferrule support groove  4  for supporting a ferrule. The ferrule support groove  4  has two side faces  4   a ,  4   b  for supporting the ferrule and a bottom face  4   c  held between these two side faces. This groove has a trapezoidal cross section. The second region  2   b  is provided with an optical fiber support groove  5  for supporting an optical fiber. In the optical module substrate  2 , the optical fiber support groove  5  and the ferrule support groove  4  are formed on the same substrate  2 . 
     Referring to FIG. 3, the substrate  2  is formed with a positioning groove  9  and a connecting groove  10 . 
     The substrate  2  has the positioning groove  9  provided so as to separate the second region  2   b  and the third region  2   c  from each other and be able to position the optical fiber. The positioning groove  9  is disposed at one end of the optical fiber support groove  5  and intersects the optical fiber support groove  5  at a predetermined angle, e.g., 90°. 
     The substrate  2  has the connecting groove  10  disposed so as to separate the first region  2   a  and the second region  2   b  from each other. The connecting groove  10  is disposed between the optical fiber support groove  4  and the ferrule support groove  5 . The connecting groove  10  intersects the optical fiber support groove  4  and the ferrule support groove  5  at an angle of 90°, for example. 
     The third region  2   c  has an optical device mount portion  6 . FIG. 2 shows the substrate  2  suitable for optically connecting a semiconductor light-emitting device ( 11  in FIG. 4) to the optical fiber. A semiconductor light-emitting device such as semiconductor laser is placed at the optical device mount portion  6 . For monitoring the semiconductor laser, a monitor light-receiving device ( 12  in FIG. 4) such as photodiode can be provided. The optical device mount portion  6  has electrodes  8   a ,  8   b ,  8   c ,  8   d  for the optical device. 
     The substrate  2  is also referred to as silicon bench when it is formed of a silicon substrate. 
     FIG. 4 is a view showing a step of mounting a semiconductor optical device onto the substrate  2 . The optical device is placed at the optical device mount portion  6  of the substrate  2 . This optical device can be optically coupled to the optical fiber. The following explanation will relate to a semiconductor laser (LD)  11  and a monitor photodiode (PD)  12  mounted on the substrate as the semiconductor light-emitting device and semiconductor light-receiving device, respectively. 
     The LD  11  is die-bonded to the optical device mount portion  6  of the substrate  2 . The die-bonding is carried out after markers on the LD and the substrate  2  are aligned with each other by use of image recognition. For achieving sufficient optical coupling to the optical fiber (single-mode optical fiber: SMF) disposed in the optical fiber support groove  4 , a positioning tolerance of 2 μm is required. 
     Subsequently, the PD  12  is die-bonded on the optical device mount portion  6  of the substrate  2 . The die bonding is carried after a marker on the PD and markers  7   a ,  7   b  on the substrate  2  are aligned with each other by use of image recognition. A positioning tolerance of about 10 μm is required for this step. 
     FIG. 5 is a view showing a step of securing an optical fiber  16  to the substrate  2 . The optical fiber is placed in the optical fiber support groove  5  of the substrate  2  and then is secured thereto by means of a securing member  18 . For this purpose, a UV-curing resin is dropped onto the substrate  2  so as to avoid the optical fiber support groove  5 , thereby forming resin members  19   a . The optical fiber  16  is disposed in the optical fiber support groove  5  and then is covered with the securing member  18 . The securing member  18  has a groove  18   a  for accommodating the optical fiber  16 , and a bonding surface  18   b  provided so as to face the substrate  2 . The optical fiber  16  is supported by three flat faces consisting of the two side faces of the optical fiber support groove  5  and the bottom face of the groove  18   a  of the securing member  18 . The securing member  18  is formed from a material that can transmit ultraviolet light therethrough, e.g., quartz. 
     FIG. 6A is a view showing a step of securing a ferrule  17 . The ferrule  17  is placed in the ferrule support groove  4 . UV-curing resin members  19   b  are also applied to the regions between the side face of the ferrule  17  and the first region  2   a  of the substrate  2 . 
     Upon irradiation with ultraviolet light, the optical fiber  16  is secured by the securing member  18  and the resin members  19   a , whereas the ferrule  17  is secured by the resin members  19   b . As a consequence, an optical module principal portion  1  is accomplished. 
     Since the UV-curing resin is used for securing the ferrule  17  and the substrate  2  to each other, the easier handling of the optical module principal portion is provided after this step. In place of the UV-curing resin, a thermosetting resin can be used as well. 
     In FIG. 6B, the optical fiber  16  is secured to the optical fiber support groove  5  while coming into contact therewith at two side faces  5   a ,  5   b . In FIG. 6C, the ferrule  17  is secured to the ferrule support groove  4  while coming into contact therewith at two side faces thereof. 
     FIG. 7 shows a step of assembling the optical module principal portion  1  on a lead frame  60 . The optical module principal portion  1  is bonded to an island portion  63  of the lead frame  60 . After the island portion  63  is coated with silver paste, the optical module principal portion  1  is mounted on the island portion  63 . For example, the silver paste is heated under such a condition as 180° C. for 20 minutes, so as to be thermally cured. Prior to this bonding, the lead frame  60  and the ferrule  17  are aligned with each other. 
     Thereafter, the optical module principal portion  1  and the lead frame  60  are wire-bonded. 
     FIG. 8 shows a potting step in which a resin is dropped onto the optical module principal portion  1 . It is desirable that the potting is effected at two locations of the optical module principal portion. 
     One of the locations lies in the region where the LD  11 , PD  12 , and the end portion of the optical fiber  16  optically coupled to the LD  11  are provided. A potting resin member  39   a  is transparent to light generated by the LD  11 . 
     The other lies in the region where the optical fiber  16  exposed on the substrate  2  is provided. Covering the optical fiber  16  with a potting resin member  39   b  can reduce the influence of contraction at the time of the hardening of the molding resin used in transfer molding. 
     Thereafter, after the encapsulation with a resin body  52  in transfer molding and the formation of leads, an optical module  54  as shown in FIG. 16 is accomplished. 
     Now referring to FIG. 9, the lead frame in accordance with the present invention will be described. FIG. 9 is a plan view of the lead frame  60  on which the optical module principal portion  1  shown in FIG. 6A can be mounted. 
     The lead frame  60  comprises an outer frame  61 , tie bars  61   e ,  61   f , inner leads  62   a , outer leads  62   b , an island portion  63 , and island support portions  64 ,  65 ,  66 . The outer frame  61  has a top rail  61   a , a bottom rail  61   b , and side rails  61   c ,  61   d . The outer frame  61  is provided with two positioning holes  69 , at their respective locations, available for aligning the lead frame  60  with an encapsulating die. The outer frame  61  constitutes a frame portion. The frame portion can include the tie bars  61   e ,  61   f . The frame portion can also include the inner leads  62   a  and outer leads  62   b.    
     The lead frame  60  has a plurality of inner leads  62   a . In the lead frame  60  shown in FIG. 9, the inner leads  62   a  are provided so as to face three sides of the island portion  63 . These three side faces are oriented in one direction along the predetermined axis  51  and other directions orthogonal to a predetermined axis  51 , respectively. The inner leads  62   a  are wire-bonded by conductive wires to their corresponding electrodes on the optical module principal portion  1  mounted on the island  63 , so as to be electrically connected with the optical module principal portion  1 . The inner leads  62   a  are supported by the tie bars  61   e ,  61   f.    
     The lead frame  60  has a plurality of outer leads  62   b . The plurality of outer leads  62   b  are disposed so as to correspond to the respective inner leads  62   a . In the lead frame  60  shown in FIG. 9, the outer leads  62   b  extend in directions orthogonal to the predetermined axis  51 . The outer leads  62   b  start from the tie bars  61   e ,  61   f , and then extend in a direction from the tie bars  61   e ,  61   f  toward the outer frames  61   a ,  61   b  so as to reach the outer frame. 
     The optical module principal portion  1  is mounted on the island portion  63  such that the end face of the ferrule  17  mounted on the optical module principal portion  1  is oriented in the direction of the predetermined axis  51  (the positive direction of X axis in FIG.  9 ). The island portion  63  has the island support portions  64  ( 64   a ,  64   b ,  64   c ,  64   d ,  64   e ),  65  ( 65   a ,  65   b ,  65   c ,  65   d ,  65   e ),  66  ( 66   a ,  66   b ,  66   c ,  66   d ,  66   e ) extending from three side faces thereof, respectively. 
     The island support portions  64 ,  65 ,  66  have deformation parts which are disposed such that the position of the island portion  63  can be displaced in directions (e.g., Y directions in FIG. 9) intersecting the predetermined axis  51  within the plane including the island portion  63 . The island support portions  64 ,  65  are disposed at two island sides oriented in directions intersecting the predetermined axis  51 . The island support portion  66  is disposed at one of island sides oriented in the directions of the predetermined axis  51 . The island support portions  64 ,  65 ,  66  reach the outer frame  61   d  or the tie bars  61   e ,  61   f , so as to support the island portion  63 . The deformation parts are elastically deformed or flexed, thereby making the position of the island portion  63  movable in directions orthogonal to the predetermined axis  51  in the plane including the lead frame  60 . 
     Each of the island support portions  64 ,  65 ,  66  can comprise bent parts which are bent at two or more positions. 
     When the bent parts are provided at two positions, the following structure can be realized: the island support portion can comprise a first part extending along the predetermined axis  51 , and second and third parts extending in directions intersecting the predetermined axis  51 , both ends of the second part being provided with the second and third parts, respectively; the island support portion can comprise fourth and fifth parts extending along the predetermined axis  51 , and a sixth part extending in a direction intersecting the predetermined axis  51 , both ends of the sixth part being provided with the fourth and fifth parts, respectively. 
     The X coordinates of the positions at which the island support portions  64 ,  65  connect with the tie bars  61   e ,  61   f  differ from those of the positions at which they connect with the island  63 . The Y coordinates of the positions at which the island support portion  66  connects with the outer frame  61   a  to  61   d  also differ from the Y coordinate of the position at which the island support portion  66  connects with the island  63 . Such positional differences make it easy to provide the island support portions  64 ,  65 ,  66  with bent parts without restricting the arrangement of inner leads. 
     In the example shown in FIG. 9, a first portion  66   a  and second portions  64   b ,  65   b  function as deformation parts. Preferably, the first portion  66   a  is narrower and longer than the other parts of the island support portion  66 . Preferably, the second portions  64   b ,  65   b  are narrower and longer than the other parts of the island support portions  64 ,  65 . 
     The island  63  is supported by the island support portions  64 ,  65 ,  66 . As a consequence, when the ferrule  17  is placed at the ferrule accommodation portion ( 42  in FIG. 12) of the encapsulating die so as to be resin-encapsulated, the deformation parts are deformed in response to the misalignment between the ferrule  17  mounted to the optical module principal portion  1  and the ferrule accommodation portion  42 . This deformation can absorb the positional deviation between the ferrule  17  and the ferrule accommodation portion ( 42  in FIG.  12 ). The inner stress caused by this positional deviation would not remain in the encapsulating resin body. 
     The lead frame  60  shown in FIG. 9 relates to the case where three sides of the island  63  are provided with the island support portions  64 ,  65 ,  66 , respectively. The positions at which the island support portions are arranged should not be, however, restricted to the examples shown in FIG.  9 . For example, the island support portions can be provided at only two sides of the island portion  63  that are oriented in directions orthogonal to a predetermined axis. 
     Preferably, the island support portions are made thinner than the island  63 . The thinner island support portions can be deformed more easily. A method of thinning the island support portions  64 ,  65 ,  66  is as follows: the lead frame  60 , covered with an etching mask except for parts to be thinned, is exposed for a predetermined period of time to a solution capable of chemically etching the material of lead frame  60 . 
     FIGS. 10 and 11 show other embodiments of the lead frame in accordance with the present invention. In FIGS. 10 and 11, parts having the same functions as those of the lead frame  60  shown in FIG. 9 are referred to with the identical numerals or letters, without repeating their descriptions. 
     The lead frame  70  shown in FIG. 10 comprises only one island support portion  66 . The island support portion  66  has a deformation part provided so as to make the island portion  63  displaceable in directions (Y directions in FIG.  10 ) orthogonal to the predetermined axis  51 . The island support portion  66  is disposed at an island side intersecting the predetermined axis  51  (the positive x direction in FIG.  10 ). 
     The lead frame  70  comprises substrate support portions  67   a ,  67   b . The substrate support portions  67   a ,  67   b  extend toward the island  63  from the tie bars  61   e ,  61   f , respectively. The substrate support portions  67   a ,  67   b  can assist in supporting the optical module principal portion  1  mounted onto the island portion  63 . Together with the island support portion  66 , the substrate support portions  67   a ,  67   b  support the optical module principal portion  1 . The island portion  63  comprises a pair of depressions  63   b . The front ends of the substrate support portions  67   a ,  67   b  are positioned within the depressions  63   b  of the island  63 , respectively. 
     When the front end parts of the substrate support portions  67   a ,  67   b  come into contact with the bottom face of the optical module principal portion  1 , the substrate support portions  67   a ,  67   b  support the optical module principal portion  1  together with the island portion  63 . The substrate support portions  67   a ,  67   b  prevent the island support portion  66  supporting the island  63  from flexing due to the load of the optical module principal portion and thereby dislocating the island portion  63  from the plane including the lead frame  70 . 
     FIG. 11 is a plan view showing the lead frame in accordance with another embodiment of the present invention. Referring to FIG. 11, the lead frame  80  comprises a pair of island support portions  68  ( 68   a ,  68   b ,  68   c ). The pair of island support portions  68  ( 68   a ,  68   b ,  68   c ) have deformation portions provided so as to make the island  63  movable in directions (Y directions in FIG. 11) orthogonal to the predetermined axis  51 . The pair of island support portions  68  are disposed at the opposite ends of one side of the island portion  63 , respectively. 
     The island support portions  68  prevent the dislocation of the island  63  from the plane including the lead frame  80  due to the load of the optical module principal portion  1 . FIG. 11 shows the lead frame  80  having the substrate support portions  67   a ,  67   b . The substrate support portions  67   a ,  67   b  can be, however, omitted if the island portion  63  can fully be supported by the island support portions  68  attached thereto. When no substrate support portions  67   a ,  67   b  are provided, the arrangement of inner leads  62   a  is restricted thereby. 
     As described in the foregoing, since the island support portions  64 ,  65 ,  66 ,  68  are provided, the positional deviation between the ferrule  17  mounted on the optical module principal portion  1  and the ferrule accommodation portion of the encapsulating die ( 42  in FIG. 12) can be absorbed by the island support portions when the ferrule  17  is placed in the ferrule accommodation portion ( 42  in FIG.  13 ). 
     A method of making an optical module using the lead frame in accordance with an embodiment of the present invention will now be explained in detail with reference to FIGS. 12 to  16 . 
     Referring to FIG. 12, the optical module principal portion  1  is mounted on the island portion  63  such that the ferrule  17  aligns with the predetermined axis  51  of the lead frame  60 . The optical module principal portion  1  is positioned on the lead frame  60  such that the ferrule  17  is accommodated in the ferrule accommodation portion ( 42  in FIG. 13) when the lead frame  60  is placed in the encapsulating die. After the mounting location of the optical module principal portion  1  is determined, the optical module principal portion  1  is bonded onto the island portion  63 . 
     Subsequently, the lead frame  60  including the optical module principal portion  1  bonded thereon is placed in the encapsulating die. This placement has already been described with reference to FIGS. 7 and 8. 
     FIG. 13 is a perspective view of the lower encapsulating die  40 . The die  40  comprises pins  41  for aligning with the lead frame  60 . On the lead-frame mounting surface  43  of the die  40 , the ferrule accommodation portion  42  and a cavity portion  45  are disposed. The ferrule accommodation portion  42  accommodates the ferrule  17  mounted onto the optical module principal portion  1  when the lead frame  60  is mounted on the surface  43 . The cavity portion  45  defines the form of the resin body of the optical module provided under the lead frame surface. The encapsulating resin for resin-molding is introduced into the cavity portion  45  from an injection gate portion  47 . 
     Referring to FIG. 14, the lead frame  60  is mounted on the die  40  such that the positioning pins  41  of the die  40  are inserted into the alignment holes  69 . Simultaneously with this positioning, the ferrule  17  is accommodated in the ferrule accommodation portion  42 . Even if the optical module principal portion  1  is slightly dislocated in the rightward or leftward direction of the ferrule  17  with respect to the lead frame  60 , such dislocation can be absorbed by the island support portions  64 ,  65 ,  66 . As a consequence, providing the island support portions  64 ,  65 ,  66  can reduce the force applied to the ferrule  17  even when it is accommodated in the ferrule accommodation portion  42  of the die  40 . 
     After the lead frame  60  and the optical module principal portion  1  are mounted on the lower die  40 , the upper die (not depicted) is assembled thereto. The encapsulating resin is injected from the injection gate  47  and cured, whereby a resin body is formed. 
     FIG. 15 is a plan view showing the resin body  52  and the lead frame  60 . The inner leads  62   a  extend in directions orthogonal to the predetermined axis  51  and are encapsulated within the encapsulating resin body  52 . The island support portions  64 ,  65  extend from the tie bars  61   e ,  61   f , respectively so as to be contained within the encapsulating resin  52 . The island support portions  66  extend from the outer frame  61   d  of the lead frame so as to be encapsulated within the encapsulating resin  52 . 
     After the resin molding, the tie bars  61   e ,  61   f , the island support portions  64 ,  65 ,  66 , and the outer leads  62   b  are cut at predetermined positions, and the outer leads  62   b  are shaped. 
     FIG. 16 shows the finished optical module  54 . Referring to FIG. 16, the shaped outer leads  62   b  and the cut end  65   f  of the island support portion  65  are shown. In the optical module  54  shown in FIG. 16, since the tie bars  61   e ,  61   f  are cut, the outer leads  62   b  are electrically isolated from each other and from the island support portions  64 ,  65 ,  66 . Providing the island support portions  64 ,  65 ,  66  would not affect the electric characteristics of the finished optical module  54 . 
     An optical module principal portion  56  in accordance with another embodiment of the present invention will now be explained with reference to FIG.  17 . The optical module principal portion  56  corresponds to the optical module principal portion  1  shown in FIG.  6 A. The lead frame, optical module, and method of making the optical module in accordance with the present invention are also applicable to the optical module principal portion  56  as described hereinafter. 
     Referring to FIG. 17, the substrate  57  comprises a base  57   a  and a platform  57   b . The platform  57   b  is mounted on the base  57   a . The base  57   a  has a first region  57   c  thereon. The platform  57   b  has a second region  57   d  and a third region  57   e  along a predetermined axis  3 . The first region  57   c  is provided with a ferrule support groove  58  for supporting a ferrule. The second region  57   d  is provided with an optical fiber support groove  5  for supporting an optical fiber. 
     The optical fiber support groove  5  and the ferrule support groove  58  are centered at the predetermined axis  3 . Since the substrate  57  is similar to the substrate  2  of FIG. 3 except for these points mentioned above, further detailed explanation will be omitted. 
     In the lead frame in accordance with the present invention, as explained in detail in the foregoing, the island support portion allows the position of the island, provided for mounting the optical module principal portion, to be displaced in a direction intersecting the ferrule axis. When the lead frame is placed in the encapsulating die so as to be resin-encapsulated, the stress caused by the positional deviation can be absorbed by the island support portion. Applying these lead frames to optical modules provides the optical modules in which the inner stress of the resin body is decreased.