BRIEF DESCRIPTION OF THE DRAWINGS
In order to understand the invention and to see how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:
FIG. 1 is an isometric view of a printed circuit board (PCB) according to the present invention;
FIG. 2 is a front view of the PCB seen in FIG. 1, together with a chip received therein;
FIG. 3 is an isometric view of the PCB according to another embodiment of the invention;
FIG. 4 is an isometric view of the PCB seen in FIGS. 1 and 2;
FIG. 5A is a schematic illustration of a prior art wire bonding process;
FIG. 5B is a schematic illustration of a wire bonding process according to the present invention;
FIG. 6 is an isometric view of yhe main components of an optical head shown in FIG. 7; and
FIG. 7 is an isometric view of an optical head.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
FIG. 1 illustrates a PCB generally designated 10 for use with an optical head 60 (shown in FIG. 7) of an endoscope. The PCB 10 comprises a front surface 11, a rear surface 13 and a recess 15 provided on the front surface 11. The recess 11 has a length L1 and a width W1 and is defined by four inner side walls 17. The recess has a depth De. The PCB further comprises a couple of alignment openings 19 at both sides of the recess 15, and a couple of through going openings 14 located at the upper edges 12 of the PCB 10. The PCB has a U-shape configuration, as will be further explained. The recess 15 has a square configuration, obtained by milling, cutting or any other suitable machining process. The recess 15 may also have corners 16 provided with small radii 16a, created during the manufacturing process.
FIG. 2 illustrates discrete components deployed on the PCB, namely, a chip 20 having bonding pads 22, and bonding pads 21 located on the front surface 11 of the PCB 10. The distance between the chip 20 and the closest thereto bonding pad 24 is designated D. The chip 20 has a length L2, a width W2 and a thickness T (shown in FIGS. 6 and 7). The chip 20 is mounted within the recess 15 by gluing in a manner that it is substantially flush with the front surface 11. The length L1 and the width W1 of the recess 15 are greater than the length L2 and the width W2 of the chip 20, respectively. Consequently, margins 23 of about 0.05-0.1 mm between the chip 20 and the inner side walls 17 of the recess made in the PCB 10 are created, the purpose of which is to allow small displacement of the chip 20 when it is being affixed within the recess 15.
FIG. 3 illustrates another embodiment of a PCB 30 according to the present invention. The PCB 30 comprises three layers: a top layer 31, an intermediate layer 33 and a bottom layer 35. The top layer 31 constitutes the forward face of the PCB 30, and a through going opening 37 is made thereinto, which can be obtained by drilling a cut-out therein, or by milling. The width W3 of the top layer 31 is substantially equal to the thickness T of the chip 20, which is mounted within the through going opening 37 as previously described. The top and the bottom layers 31 and 35 may be made of dielectric material, e.g. epoxy glass FR4, and the intermediate layer 33 may be made of an electrically conductive material, e.g. copper.
The following description, although referring to the PCB 10, is applicable to the PCB 30 as well.
FIG. 4 illustrates the PCB 10 with the chip 20 mounted within the recess 15 while the chip 20 is flush with the front surface 11 of the PCB 10. A cable 41 is seen being connected to the PCB 10. The cable comprises signal lines for transferring signals to and from the chip 20 as well as a power line for energizing the chip 20 and the LEDs of the optical head, as will be further described.
In use, the chip 20 is electrically connected to the bonding pads 21 by electrical wires 26 (shown in FIG. 2), which are bonded to the bonding pads 22 on the chip 20 at their one end and to the bonding pads 21 of the PCB 20 at their other end.
FIG. 5B illustrates a bonding process according to the present invention. A nozzle 51 of a bonding machine, having a radial dimension R, connects the bonding pad 21 to the corresponding bonding pad 22 of the chip 20. It is seen that the chip is flush with the front surface 11 of the PCB 10. By virtue of this provision the distance D2 between the bonding pad 22 of the chip 20 and the bonding pad 21 of the PCB is not limited by the dimension R, and may be reduced below the radial dimension R, thereby reducing the overall size of the PCB 10. In practice the distance D2 may be, for example, reduced from 045 mm (for a chip which is not flush) to about 0.15 mm.
FIGS. 6 and 7 illustrate the PCB 10 and the chip as they are used with an optical head 60 of an endoscope. FIG. 6 shows the main components of the optical head 60, namely, the PCB 10 with the chip 20 mounted therein, a lens retaining member 61, a filter 65 secured within the lens retaining member 61, and a lens 63. The PCB 10 is attached to the lens retaining member 61 by alignment pins (not shown) inserted in the alignment openings 19 (shown in FIGS. 1 to 4).
FIG. 7 illustrates the optical head 60 together with a disposable cap 70 put on a distal end of an insertion tube of an endoscope. The cap 70 is detachably connectable to a main body portion 71 of the optical head 60. Along the optical head 60 extends a multilumen tubing 73. The main body portion is provided with a dedicated U-like depression 75, through which extends the multilumen tubing and with a room 79, which has U-like cross sectional shape. Within the room 79 are received optical components of the optical head 60. The room 79 is located below the U-like depression such that the multilumen tubing is situated above the optical components. Among the optical components are, for example, lens 63 and illuminating means (not shown). The illuminating means, such as for example, two LEDs may be situated at the right and left side of the lens 63. The cap 70 comprises a butt end 72, which has a window 77a for the multilumen tubing 77, a window 63a for the lens 63 and a window 74a for passing light from the illuminating means. The above configuration of the optical head 60 is described in more details in Aizenfeld (International Patent Publication No. WO 2006/025058), which is incorporated herein by reference.
As shown in FIG. 7, the PCB 10 is part of the optical head 60 as previously described in FIG. 6. It can be also appreciated that the U-like cross-sectional shape of the room 79 dictates the U-shaped configuration of the PCB.
The invention is described in detail with reference to a particular embodiment, but it should be understood that various other modifications can be effected and still be within the spirit and scope of the invention.
Patent Application
20080055403
