Abstract:
A device includes a printed circuit board having a first surface and a second surface. The printed circuit board defines an opening therethrough from the first surface to the second surface and a circuit formed on the first surface of the printed circuit board with no portion of the circuit intersecting the opening. The second surface of the printed circuit board at least partially bounds a first channel in fluid communication with the opening. A method of venting includes displacing air within a cavity of a switch by moving the air through one or more channels formed in a layer defining cut-outs in fluid communication with the cavity. The air is moved through an opening formed in a printed circuit board. The layer is positioned at a first side of the printed circuit board. In addition, the method includes moving the air through a venting channel positioned at a second, opposite side of the printed circuit board and into the surrounding environment.

Description:
TECHNICAL FIELD 
   This invention relates to an autoclavable switch assembly. 
   BACKGROUND 
   During a surgical procedure, remote hand controls including a series of switches built upon a printed circuit board are typically used to control surgical devices located in a non-sterile area of the operating room but that require control from the sterile field where a patient is located. The remote controls are sterilized by autoclaving after each use. In order to withstand repeated autoclave cycles, the switches and printed circuit board are generally sealed in an autoclave resistant housing. However, during switch operation, air often becomes trapped in a cavity of the switch. For the switch to function properly, the air is generally vented via air flow channels connecting the cavities and through vent holes connecting the channels to an environment external to the PCB but internal on the remote control assembly. 
   SUMMARY 
   The venting of air from the switch cavities increases the chance of failure of the printed circuit board circuitry because contaminants, such as water, can enter via the vent holes and contact the circuitry, causing shorts or other failures. Such damage can be limited by minimizing the number of vent holes, placing the circuitry on only one side of the printed circuit board, and providing a tortuous air flow channel that not only eliminates any direct path for the contaminants to travel to the circuitry but also acts to trap the contaminants in the channel. By limiting the damaging effects of contaminants, the present assemblies and techniques provide a surgical team with a remote control assembly that can withstand a commercially-acceptable number of autoclave cycles, for example, between approximately 500 and 1000 autoclave cycles without failure. 
   In one general aspect, a device includes a printed circuit board having a first surface and a second, surface. The printed circuit board defines an opening therethrough from the first surface to the second surface and a circuit formed on the first surface of the printed circuit board with no portion of the circuit intersecting the opening. The second surface of the printed circuit board at least partially bounds a first channel in fluid communication with the opening. 
   Implementations may include one or more of the following features. For example, a spacer layer is coupled to the first surface of the printed circuit board. The spacer layer defines a second channel in fluid communication with the opening in the printed circuit board and the first channel. The circuit includes a selectively activatable switch contact for completing an electrical circuit. 
   In addition, a set of solder pads are disposed on the second surface of the printed circuit board that provide termination points for the circuit. The first channel is formed in the second surface of the printed circuit board. The first channel includes a tortuous configuration and the first channel limits contact between contaminants and the circuit thereby enabling the device to be autoclaved. 
   In addition, a vent layer is coupled to the second surface of the printed circuit board. The vent layer defines a cutout therethrough that cooperates with the second surface of the printed circuit board to bound the first channel. A vent layer cover is coupled to the vent layer and defines an opening therethrough. The opening is in fluid communication with the first channel and the vent layer cover cooperates with the cutout and the second surface of the printed circuit board to bound the first channel. 
   A set of switch contacts are arranged in a predetermined pattern on the first surface of the printed circuit board, and a set of selectively activatable switches, are disposed within the spacer layer. Each one of the set of selectively activatable switches is positioned relative to a respective one of the set of switch contacts for activating the respective one of the switch contacts. 
   The second channel includes a set of cutout portions that overlay the set of switch contacts and a set of pathways extending between the set of cutout portions so that the set of pathways do not intersect the circuit. The first channel and the second channel cooperate to limit contact between contaminants and the circuit thereby enabling the device to be autoclaved. 
   The device further includes a cover layer coupled to the spacer layer to retain the set of selectively activatable switches in position within the spacer layer. The set of selectively activatable switches are dome switches that include gold plated stainless steel domes. 
   In another general aspect, a device includes a printed circuit board having a first surface and a second surface and a circuit traversing only the first surface of the printed circuit board. A selectively activatable switch is positioned relative to the circuit. The second surface of the printed circuit board at least partially bounds a channel in fluid communication with the selectively activatable switch. 
   Implementations may include one or more of the following features. For example, the device includes a resilient keypad including a button positioned relative to the selectively activatable switch for activating the selectively activatable switch. 
   In another general aspect, a method of venting includes displacing air within a cavity of a switch by moving the air through one or more channels formed in a layer defining cut-outs in fluid communication with the cavity. The air is moved through an opening formed in a printed circuit board. The layer is positioned at a first side of the printed circuit board. In addition, the method includes moving the air through a venting channel positioned at a second, opposite side of the printed circuit board and into the surrounding environment. 
   Implementations may include one or more of the following features. For example, the venting channel has a tortuous configuration. 
   Advantages can include limiting the exposure of the printed circuit board circuitry from any external penetration of contaminants; minimizing the number of vent access holes while maintaining ability to provide for venting of remote switches; providing solder pads on one side of a printed circuit board; reducing the pumping effect of switches alternating from pressure to vacuum by increasing the distance of the vent pathway; eliminating the solder mask from printed circuit board thereby eliminating exposure of circuitry as a result of degradation of the mask during autoclave cycles; and increasing spacing of circuit traces and solder pads reducing potential shorts. 
   The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. 

   
     DESCRIPTION OF DRAWINGS 
       FIG. 1  is an illustration of an autoclavable electronic device. 
       FIG. 2  is an exploded view of the remote control of  FIG. 1 . 
       FIG. 3  is an exploded view of a printed circuit board assembly of the electronic device of  FIG. 1 . 
       FIG. 4  is bottom view of the assembled printed circuit board assembly of  FIG. 3  without the vent layer cover. 
       FIG. 5  is a top view of the assembled printed circuit board assembly of  FIG. 3  without the cover. 
   

   DETAILED DESCRIPTION 
   Referring to  FIGS. 1 and 2 , an autoclavable switch assembly, for example, a remote control  100  includes a set of buttons  60  and associated switches  70  for manually operating a surgical device (not shown). The switches close circuits  205  ( FIG. 3 ) on a printed circuit board (PCB) assembly  20  to provide the control signals for the surgical device. The switches are activated by a keypad  30 . The PCB assembly  20  and the keypad  30  are sealed within a base  10  and a bezel  40 . Signals from the remote control  100  to the surgical device are communicated via a cable assembly  50 . Alternatively, signals can be transmitted wirelessly. 
   Referring to  FIG. 3 , the PCB assembly  20  includes a printed circuit board (PCB)  200  sandwiched between a spacer layer  300  and a vent layer  400 . The PCB  200 , spacer layer  300 , and vent layer  400  are sealed between a vent layer cover  500  and a switch cover  600 . 
   The PCB  200  includes a first surface  200   a  and a second surface  200   b . The circuits  205  are formed by, for example, chemical etching, on the first surface  200   a  of the PCB  200  in a desired pattern. The set of circuits  205  each traverse the first surface  200   a  and pass through a portion of the PCB  200  where they each terminate at one of a set of solder pads  215  ( FIG. 4 ) disposed on the second surface  200   b  of the PCB  200 . In this implementation, the set of circuits  205  do not traverse the second surface  200   b . Each of the pads in the set of solder pads  215  is coupled to a corresponding control wire  52  of the cable assembly  50  and is coated with a high temperature autoclavable epoxy. The circuits  205  include switch contacts  210  arranged in a predetermined pattern within the circuits  205 . The switch contacts  210  cooperate with respective switches  70  to close electrical circuits. The PCB  200  also defines an opening  220  therethrough that extends from the first surface  200   a  to the second surface  200   b . The opening  220  is in fluid communication with the spacer layer  300  and the vent layer  400  to provide a vent pathway, as described in more detail below. In this implementation, the PCB  200  is made from FR4 laminates with gold plating and without a conventional solder mask on the lower surface  200   b.    
   The spacer layer  300  is coupled to the first surface  200   a  of the PCB  200 . The spacer layer  300  includes a first surface  300   a  and a second surface  300   b  facing the first surface  200   a  of the PCB  200 , and an acrylic adhesive disposed on the first and second surfaces  300   a ,  300   b . When the spacer layer  300  is brought into contact with the PCB  200 , and more particularly, the second surface  300   b  of the spacer layer  300  is brought into contact with the first surface  200   a  of the PCB  200 , the acrylic adhesive acts to form a sealing bond between the spacer layer  300  and the PCB  200 . The spacer layer  300  defines a channel  305  that includes cutout portions  310  and pathways  315  extending between the cutout portions  310 . The cutout portions  310  overlay the pre-arranged pattern of the switch contacts  210  formed on the first surface  200   a  of PCB  200  and receive a respective one of the switches  70 . As shown in  FIG. 5 , the set of pathways  315  are formed in the spacer layer  300  such that when the spacer layer  300  is disposed on the PCB  200 , the set of pathways  315  do not overlap, intersect, or overlay any of the set of circuits  205 . This configuration limits the potential for contaminants to damage the set of circuits  205  as will be explained in more detail below. As further shown in  FIGS. 3 and 5 , a portion  315   a  of the set of pathways  315  overlays the opening  220  of the PCB  200  and is in fluid communication with the opening  220  when the spacer layer  300  is disposed on the PCB  200 . 
   Referring to  FIGS. 3 and 4 , the vent layer  400  is coupled to the second surface  200   b  of the PCB  200 . The vent layer  400  includes a first surface  400   a  and a second surface  400   b  each having an acrylic adhesive disposed thereon. As such, when the vent layer  400  is brought into contact with the PCB  200 , and more particularly, the first surface  400   a  of the vent layer  400  is brought into contact with the second surface  200   b  of the PCB  200 , the acrylic adhesive acts to form a sealing bond between the vent layer  400  and the PCB  200 . The vent layer  400  further defines a cutout  405  that extends from the first surface  400   a  to and through the second surface  400   b  and that forms a channel  415 . 
   The channel  415  includes a first end  415   a  that overlays, and is in fluid communication with, the opening  220  formed in the PCB  200 , and a second end  415   b  that is in fluid communication with an opening  510  formed in the vent layer cover  500 . The opening  510  is in fluid communication with the environment surrounding the PCB assembly  20 , which is the interior of the remote control  100  in this exemplary implementation defined by the base  10 , the bezel  40 , and the keypad  30 . The opening  510  represents the sole opening for the PCB assembly  20  in direct fluid communication with the environment. The vent layer cover  500  is coupled to the second surface  400   b  using the acrylic adhesive disposed on the second surface  400   b  of the vent layer  400 . The vent layer  400  and the vent layer cover  500  each further define openings  420  and  520 , respectively, which are configured to overlay the set of solder pads  215  and to provide a passageway for the control wires  52  therethrough. The acrylic adhesive used to couple the vent layer cover  500  to the vent layer  400  and the vent layer  400  to the second surface  200   b  of the PCB  200  forms a fluid-tight seal around the openings  420  and  520  so that there is no fluid communication between the PCB assembly  20  and the environment via the openings  420  and  520 . The vent layer cover  500  is made from a polyester or other suitable material. 
   Referring to  FIGS. 3 and 5 , the set of switches  70  are received within the set of cutout portions  310  of the spacer layer  300  and are free to move within the set of cutout portions  310  prior to disposition of the cover  600  on the spacer layer  300 . The cover  600 , which may be made from, for example, a polyester covered with a screened silver, retains the set of switches  70  in position within the spacer layer  300  and in position relative to a respective one of the set of switch contacts  210 , as illustrated in  FIG. 5 . Exemplary switches for use in this implementation include tactile, gold-plated, stainless steel dome switches, however, other suitable switches may be used. The use of gold-plating has been found to enhance the corrosion resistance of the set of switches  70 , to make the set of switches  70  less susceptible to retaining deposits, such as fluorides, during autoclave cycles, and to provide increased switch continuity. 
   As shown in  FIG. 2 , the keypad  30 , made, for example, from a resilient rubber, elastomer, or other suitable material, overlays the PCB assembly  20  in the remote control  100 . The keypad  30  includes the buttons  60  each of which is positioned over and relative to a respective one of the switches  70  for selectively activating the switch. For example, each of the buttons  60  can represent various functions (in a pump, for example), such as, power on/off, flow up/down, pressure up/down, etc. 
   The base  10  cooperates with the keypad  30  and the bezel  40  to seal the PCB assembly  20  within an interior of the remote control  100 . To provided this seal, the base  10  includes a set of peripheral grooves and protrusions  14  that mate with a set of corresponding grooves and protrusions  32 ,  42  formed on the keypad  30  and the bezel  40 . The base  10  also defines a cavity  16  that receives a set of control wires  52  of the cable assembly  50 . The control wires  52  carry control information from the electronic device  100  to the surgical device in a conventional manner. The base  10  further defines an area  15  configured to receive the PCB assembly  20  upon assembly of the remote control  100 . When the PCB assembly  20  is assembled into the base  10 , the vent opening  510  is positioned over the cavity  16  so that an air gap exists between the bottom of the cavity (not shown) and the vent opening  510 . Such placement limits direct contact by contaminants with the vent opening  510  in the event that water or other contaminants migrate through the seal and accumulate in the cavity  16 . 
   Referring again to  FIG. 1 , a clip  12  cooperates with the base  10  to provide a user with a convenient way to attach the remote control  100  to a desired attachment point, such as a patient&#39;s drape, a post, or other suitable location. The clip  12  has openings  12   a , and the base  10  includes protrusions  18 , one of which is shown in  FIG. 2 , that cooperate with the openings  12   a  and a spring  13  to pivotally mount the clip  12  to the base  10 . 
   The PCB  200 , the spacer layer  300 , the vent layer  400 , and the vent layer cover  500  cooperate to form a fluid communication pathway between each of the set of switches  70  and the external environment of the PCB assembly  20  such that air within a switch cavity  70   a , which is a cavity formed between the switch  70  and the PCB  200 , can be displaced and vented and the pressure equalized with the surrounding environment to permit the set of switches  70  to close properly. In the present exemplary implementation, the channel  305  of the spacer layer  300  is in fluid communication with the opening  220  defined by the PCB  200 , which is in turn in fluid communication with the channel  415  defined by vent layer  400 . The channel  415  is in turn in fluid communication with the opening  510  defined by the vent layer cover  500 , which is in turn in fluid communication with the surrounding environment of the PCB assembly  20 , which is the interior of the remote control  100  in this implementation. Accordingly, when one of the set of switches  70  is activated, air within the switch  70 , and more particularly, within a cavity  70   a  of the switch  70 , can move through the channel  305  of the spacer layer  300 , through the opening  220  formed in the printed circuit board  200 , through the channel  415 , and out the opening  510  to the surrounding environment. Venting each of the set of switches  70  in this manner allows the pressure within each of the set of switches  70  to be equalized with the surrounding environment. 
   The configuration of the vent channels in the instant implementation not only allows for switch closure but it also acts to limit the contamination of, and substantially extend the life of the PCB assembly  20 , and as a result the life of the remote control  100 , following multiple autoclave cycles. The keypad  30  of the remote control  100  acts to seal the PCB assembly  20  within the remote control  100  as discussed above. However, after a number of autoclave cycles, the seal between the bezel  40  and the base  10  can degrade and water or other contaminants enter the interior portion of the remote control  100 . If this occurs, these contaminants can eventually enter the opening  510  defined by the vent layer cover  500 , migrate along the channel  415  and eventually make there way to the circuits  205 , and more specifically, the set of switch contacts  210  via the pathways  315 . However, because of the configuration of the channel  415 , which as shown in  FIG. 3  comprises a tortuous configuration including a number of repeated turns or bends  415   c  along a circuitous path, and the channel  305 , and the fact that the set of pathways  315  do not intersect any of the set of circuits  205 , there is a long pathway between the opening  510  and the circuits  205 , with no direct path to the circuits  205  as a result. Therefore, the contaminants entering through the opening  510  tend to become trapped primarily within the tortuous channel  415  defined by the vent layer  400 , and secondarily, within the set of pathways  315  defined by the spacer layer  300  rather than reaching the set of circuits  205 . 
   A number of implementations of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. For example, while the tortuous channel  415  of the vent layer  400  has been illustrated as a separate layer coupled to the second surface  200   b  of the PCB  200 , the channel  415  may be formed directly in the second surface  200   b  of the PCB  200 . Although the PCB  200  has been described as being made from FR4 laminates with gold plating and without a conventional solder mask, other suitable laminates, such as CEM 1  or CEM 3 , and configurations are possible. Acrylic adhesives have been described for use on the spacer layer  300  and the vent layer  400 , but other suitable adhesives, such as epoxies, or other suitable materials may be used. In addition, although opening  220  is shown positioned in PCB  200  such that it fluidly communicates with the portion  315   a  of the pathways  315  and the first end  415   a  of channel  415 , opening  220  may be positioned at other locations in PCB  200 . For example, the opening  220  can be positioned to fluidly communicate with any one of the set of pathways  315  ( FIG. 3 ) so long as the opening  220  is also in fluid communication with the channel  415 . Accordingly, other embodiments are within the scope of the following claims.