Abstract:
A system and method for inductance testing a planar magnetic circuit in a board having a pair of contacts that may include a core; a pair of leads; a controller for contacting the pair of leads with the pair of contacts, registering the core with the planar magnet circuit, and delivering an electrical current through the planar magnetic circuit while the core enhances inductance in said planar magnetic circuit; and an inductance measuring tool. In another aspect, a system and method for high potential testing a planar magnetic circuit that may include providing an electrically isolated bed, loading the board on the bed, providing a pair of leads, contacting the pair of leads with the pair of contacts using a controller, delivering an electric current having a predetermined voltage between about 1,000 and about 30,000 volts through the planar magnetic circuit; and determining whether the board withstands the predetermined voltage. In another aspect, a plurality of beds may register a plurality of planar magnetic circuits.

Description:
This application claims the benefit of U.S. Provisional Application No. 60/549,997, filed Mar. 4, 2004. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to the testing of printed circuit boards, and more specifically the testing of circuit boards by administering one or more electrical tests under automated control and distinguishing between passed and failed circuit boards. 
   2. Background of the Invention 
   Circuit boards, i.e., printed circuit boards or PCBs, in general may be tested by administering electrical tests during manufacturing. For example, U.S. Pat. No. 6,396,295 teaches a method of administering a test to an integrated circuit and determining whether the integrated circuit passes or fails the test. 
   The evolution and advancement of circuit board and electronic technology has brought about the need for new or additional tests that may be difficult, or impossible, with existing testing equipment. Many tests may be conducted by human operators because no existing automated equipment may be able to conduct the required tests. 
   For example, technologies such as planar magnetics may require inductance testing using ferrite cores and high voltage potentials, e.g., 2,000 volts or more. Existing automated testing equipment, e.g., flying probe testers and bed-of-nails testers, may not be capable of testing at high potentials and with cores. In addition, existing testing equipment may not be fully automated and may require human operators to perform one or more steps for each circuit test, which may lower overall manufacturing and testing efficiency. For example, a human operator may be able to test only 1,000 to 2,000 planar magnetic circuit boards per day for inductance and high potential while production needs may be 100,000 to 300,000 circuit boards per day. 
   Existing testing methods may be so time consuming and expensive so that, in order to be cost effective, only samples of lots and not each individual circuit board may be tested. One to three hundred defective circuit boards may be missed for every million defective circuit boards that are identified. Since, for example, a single circuit board design may be produced, currently at global levels, in quantities of 100 million or more per year, 10,000 or more defective circuit boards may be allowed to pass though quality review and then further processed, used, or sold to manufactures and end-users. 
   Each defective circuit board allowed though testing, processing, and eventually sold may require hours of the end-manufacturer&#39;s or end-user&#39;s time identifying and repairing the problem, potentially costing much more in lost productivity than the production cost of the original defective board. 
   What is needed is a system for more effectively and more economically testing circuit boards. 
   BRIEF SUMMARY OF THE INVENTION 
   A system for inductance testing a plurality of planar magnetic circuits may include a substrate; a plurality of cores spaced and electrically isolated from one another and mounted on the substrate, wherein each one of the plurality of cores registers with a corresponding one of the plurality of planar magnetic circuits; a pair of leads; a controller for selecting one of the plurality of planar magnetic circuits, contacting the pair of leads with the selected planar magnetic circuit, and delivering an electrical current through the selected planar magnetic circuit while the corresponding registered core enhances inductance in the selected planar magnetic circuit; and an inductance measuring tool. The system may further include a plurality of beds in the substrate for registering the plurality of planar magnetic circuits with the plurality of cores. 
   Another aspect may be a system for inductance testing a planar magnetic circuit in a board having a pair of contacts that may include a core; a pair of leads; a controller for contacting the pair of leads with the pair of contacts, registering the core with the planar magnet circuit, and delivering an electrical current through the planar magnetic circuit while the core enhances inductance in the planar magnetic circuit; and an inductance measuring tool. Furthermore, at least a part of the core may be compressibly mounted. 
   Still another aspect may be a system for high potential testing a plurality of boards each one having at least one planar magnetic circuits with a pair of contacts, that may include a substrate having a plurality of electrically isolated beds for receiving said plurality of boards; a pair of leads; a controller for selecting one of the planar magnetic circuits and contacting the pair of leads with a corresponding pair of contacts for the selected planar magnetic circuit; a high potential testing tool for delivering a predetermined voltage between about 1,000 volts and about 30,000 volts through the selected planar magnetic circuit and determining whether the selected planar magnetic circuit withstands the predetermined voltage. Alternatively, the predetermined voltage may be between about 2,000 volts and about 3,000. In addition, the system may further include a means for subsequently identifying the selected planar magnetic circuit if the selected planar magnetic circuit fails to withstand the predetermined voltage. 
   Yet another aspect may be an apparatus for inductance testing boards having planar magnetic circuits that may include a substrate, a plurality of cores spaced and electrically isolated from one another and mounted on the substrate, and a plurality of beds on the substrate for receiving the boards and registering the planar magnetic circuits with respect to the plurality of cores. 
   A further aspect may be a method for inductance testing a board having a planar magnetic circuit and a pair of contacts, including the steps of: providing a substrate having an electrically isolated core and bed; loading the board on the bed to register the planar magnetic circuit the said core; providing a pair of leads and a plate; contacting the pair of leads with the pair of contacts and the plate with the core using a controller; delivering an electrical current through the planar magnetic circuit while the plate and the core enhance inductance in the planar magnetic circuit; measuring inductance in the planar magnetic circuit; and determining whether the inductance is in a predetermined range. The method may further include ablating at least a portion of the board if the inductance is not in the predetermined range. A board may be approved by this method. 
   The method may still further include analyzing the board to identify a defect if the inductance is not in the predetermined range and improving a design of the board to overcome the defect. A board also may be improved by this method. 
   Yet another aspect may be a method of high potential testing a board having a planar magnetic circuit with a pair of contacts, including the steps of: providing a substrate having an electrically isolated bed; loading the board on the bed; providing a pair of leads; contacting the pair of leads with the pair of contacts using a controller; delivering an electric current having a predetermined voltage between about 1,000 and about 30,000 volts through the planar magnetic circuit; and determining whether the board withstands the predetermined voltage. Alternatively, the predetermined voltage may be between about 2,000 and about 3,000 volts. The method may further include ablating at least a portion of the board if the inductance is not in the predetermined range. Furthermore, a board may be approved by this method. 
   The method may still further include analyzing the board to identify a defect if the board does not withstand the predetermined voltage and improving a design of the board to overcome the defect. A board also may be improved by this method. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a testing machine in accordance with the invention. 
       FIG. 2  is a cross-section view of a tester and a jig in accordance with the invention. 
       FIG. 3  is an exploded view of a jig, core, and circuit board. 
       FIG. 4  is a view of a testing jig. 
       FIG. 5  is a view of an alternative testing jig. 
       FIG. 6  is a bottom view of a tester. 
       FIG. 7  is a bottom view of a high potential tester. 
       FIG. 8  is a side view of an inductance tester and a jig. 
       FIG. 9A  is a circuit schematic of a relay and fault test interface board. 
       FIG. 9B  is a circuit schematic of a speed check and test faulty interface board. 
       FIG. 9C  is a circuit schematic of a trigger interface board. 
       FIG. 10  is a block diagram of a method of testing in accordance with the invention. 
       FIG. 11  is a block diagram of a testing system in accordance with the invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   1. Overview 
   A circuit board may be tested through one or more electrical tests by an automated machine. Approved, non-defective, circuit boards may be subsequently identified from defective circuit boards, so that approved circuit boards may be processed, used, or sold. In another aspect, defective circuit boards may be destroyed or otherwise rendered unserviceable. 
   A system or means for testing circuits boards may meet one or more of the following criteria: it may be more cost effective than current means and systems; it may allow one more tests to be conducted including high potential, inductance, capacitance, conductance, and resistance; it may test every circuit board manufactured or processed; passed circuit boards may be clearly distinguished or identified from defective circuit boards, e.g., by making defective circuit boards unserviceable, e.g., by destroying defective circuit boards; it may be safety interlocked; if adapted to or used to upgrade existing equipment, it may not seriously affect the existing equipments ability to perform its original function, e.g., adding testing functionality to a PCB drilling machine should not disable the drilling function; it should may be automated and require minimal human intervention; and it may increase testing accuracy and yield over semi-automated methods or human performed tests. 
   In one embodiment, a controller or computer controlled tester head and drill on a movable carriage, e.g., using the apparatus shown in  FIG. 1 , a testing machine  10 , may implement testing. Testing machine  10  may perform one or more electrical tests including but not limited to high potential, resistance, inductance, capacitance, and conductance. 
   Testing machine  10 ,  FIG. 1 , may include a carriage  50  movable on one or more axes with respect to a circuit board  100 . For example, carriage  50  may be movable, i.e., translated, on an x-, y-, and z-axis. Testing machine  10  may include one or more testers  60  for performing electrical tests of circuit boards  100 , e.g., an inductance tester or a high potential or dielectric withstand tester. Testers  60  may be mounted to carriage  50  and be movable in one or more axes with respect to circuit board  100 . 
   Fore example, tester  60  may include a test block  66  which is an inductance tester,  FIG. 6 . Inductance test block  66  may include a secondary core  210  on a compressible mount  220 . Inductance test block  6  may include two or more test pins  230 . In another example, tester  60  may include a test block  66  which is a high potential test block,  FIG. 7 . High potential test block  66  may include two or more test pins  302 . 
   Alternatively, tester  60  may include both inductance test block and high potential test block. As yet another alternative, test block  66  may function as a high potential test block, an inductance test block, or both, i.e., tester  60  may be able to test both inductance and high potential. 
   Tester  60 ,  FIG. 1 , may test circuit boards  100  and determine if a circuit board  100  passes electrical tests and is passed or approved for further manufacturing, use, processing, or sale. The testing machine may include a means of distinguishing between defective and approved circuit boards. For example, the testing machine may mark or code circuit boards so as to distinguish them as approved or defective, or the testing machine may store in computer memory or other computer readable media whether circuit boards passed or failed tests, e.g., software which records to a computer accessible media the which circuits are defective or software which records which circuits are approved. 
   Defective circuit boards  100  may be distinguished or identified by destroying them, e.g., using a drill  400  mounted to carriage  50 . In another aspect of the invention, circuit boards  100  may be bar coded or marked with ink, paint, or a sticker which indicates or allows a computer to determine whether the circuit board passed or failed tests. In still another aspect of the invention, circuit boards  100  may be engraved, stamped, scratched, scored, or marked with an electrical arc or laser. 
   Testing machine  10  may include one or more controllers  600 ,  FIG. 1 , to coordinate the actions of carriage  50 , drill  400 , and testers  60 . Controllers  600  may include dedicated controllers, industrial controllers, personal computers, industrial computers, interfacing hardware, control software, and operator interfaces. 
   The method may include the steps of moving carriage  50 ,  FIG. 1 , so that tester  60  is over circuit board  100  mounted or lying on a substrate which may be a table  52  or a jig  150 . Carriage  50  then may move along an axis, e.g., the z-axis which may be generally perpendicular to the plane in which the circuit board and jig lie, so that tester  60  is in a predefined range for testing circuit board  100 . This may involve a surface of tester  60  touching a surface of circuit board  100  or circuit  110  on circuit board  100 . Tester  60  may electrically test circuit board  100 . If tester  60  determines circuit board  100  passes electrical tests, circuit board  100  may be processed, used, or sold. 
   If testers  60 ,  FIG. 1 , determine that circuit board  100  is defective, controller  600  may direct carriage to move so that drill  400  is over circuit board  100 . Drill  400  may then destroy circuit board  100 . 
   After testing circuit board  100 ,  FIG. 1 , and determining if it passes electrical tests, carriage  50  may move so that tester  60  is positioned over another circuit board  102  so that testing may continue. This process may be repeated for additional circuit boards  102 . 
   Testing machine  10  may be implemented as an upgrade to existing equipment, e.g., to provide or enhance testing capabilities. Alternatively, testing machine  10  may be implemented as a stand-alone machine. 
   2. Carriage 
   Carriage  50 ,  FIG. 1 , may be a movable with respect to circuit board  100  in one or more axes. Carriage  50  may allow one or more testers  60  to be mounted and moved with respect to a circuit board  100 . Alternatively, carriage  50  may include integral testers. Carriage  50  may include a drill  400 . Drill  400  may be able to rotate bits, e.g., drilling or routing bits, which may be able to destroy circuit boards which fail one or more tests implemented by testers. 
   For example, carriage  50 ,  FIG. 1 , may be a head from a CNC machine. The CNC machine may be able to translate, i.e., move, the carriage horizontally and vertically with respect to a substrate, which may be a table  52  or jig  150 , on which circuit board  100  may be mounted. The CNC machine may have one or more axes and rails (not shown) along which carriage  50  may be translated. Carriage  50  may be translated along the rails by actuators (not shown). The actuators may drive lead screws (not shown) with may engage with threads (not shown) on carriage  50 . When the lead screws are rotationally translated by the actuators, they may cause carriage  50  to be linearly translated. The actuators may be motors, e.g., DC servo motors, stepper motors, pneumatic motors, or pneumatic rams. 
   Alternatively, circuit board  100 ,  FIG. 1 , may be translated with respect to carriage  50  and testers  60 . As yet another alternative, testing machine  10  may employ a combination of a movable carriage and a movable jig to translate circuit board  100  with respect to carriage  50  and testers  60 . 
   For example, circuit boards  100 ,  FIG. 1 , may be mounted or lying on a jig  150  which may be mounted or lying on table  52 . Table  52  may be movable in one or more axes, e.g., in the y-axis. Carriage  50  may be movable in the x-axis. So, circuit boards  100  on jig  150  may be accessible to a tester by a combination of movement of carriage  10  along the x-axis and jig  150  or table  52  along one the y-axis. 
   As another example, circuit board  100 ,  FIG. 1 , may be mounted and registered on jig  150 , and may be translated in one or more axes, e.g., jig  150  may be moved on a conveyer belt so that circuit board  100  passes under tester  60  and drill  400 . A controller  600  or computer  610  may translate tester  60  so that tester  60  is within testing range of circuit board  100  when circuit board  100  passes underneath tester  60 . Tester  60  may perform one or more electrical tests. If tester  60  determines circuit board  100  has passed electrical tests, it may be further processed, sold, or used. If tester  60  determines circuit board  100  has failed one or more tests, controller  600 ,  FIG. 1 , or computer  610  may translate drill  400 ,  FIG. 1 , when circuit board  100  passes underneath drill  400  so that drill  400  destroys circuit board  100 . Drill  400  may destroy circuit board by ablating sufficient material from circuit board  100  so that it is generally unserviceable, e.g., by using a router or drilling bit to make a hole or break in circuit board  100  or a circuit  110  on circuit board  100 . 
   Testing machine  10 ,  FIG. 1 , may use one or more positional feedback systems  70  to determine the position of carriage  50  and tester  60  with respect to circuit board  100 . Circuit board  100  or jig  150  may include location markers that may allow positional feedback system  54  to calibrate position with respect to circuit board  100  or jig  150 . For example, position feedback system  54  may include one or more position sensors, e.g., optical encoders, or optical switches, or rotary encoders, to determine the position of carriage  50  as it is translated. Position feedback system  54  may include sensors, e.g., video cameras, optical scanners, bar code readers, electronic signature readers, or mechanical sensors, to coordinate the position of testers  60 , carriage  50 , and drill  400  with circuit boards  100  and jig  150 . 
   Sensors also may detect circuit board or jig configuration and layout so that different types of jigs and circuit boards can be tested by the testing machine with little or no manual configuration by the operation. For example, an operator may load circuit boards onto jig  150  and a sensor may determine the type of circuit board or circuit board orientation on jig  150 . Controller  600 ,  FIG. 11 , or computer  610  may automatically determine how to position tester  60  in order to test each circuit board  100 . Tester controllers  620  may automatically determine how to best test circuit boards  100  based on predefined parameters which may be dependent on customer specifications, e.g., MIL-PRF-31032, MIL-PRF-5510, ISO 9001–2000, and other industry, consumer, and military specifications; circuit board material; and intended use. Alternatively, controller  600  or computer  610  may configure tester controller  620  to test circuit boards  100 . 
   In one embodiment, the testing machine includes a CNC machine for carriage control and drive, e.g., a DYNAMOTION CNC machine. The CNC machine may include carriage with a drill, e.g., a single spindle SMART DRILL with an air bearing spindle. The CNC machine may include a magazine tool-change with 100 or more tools and a laser block to measure drill bit size, run out and length. 
   3. Substrate or Jig 
   Circuit boards  100 ,  FIGS. 4 and 5 , may be mounted to substrate, fixture, or jig  150 . Jig  150  may have indentations, recesses, or beds, e.g., core beds  152  and circuit beds  154 , sized to securely mount circuit board  100  in a fixed position. Jig  150  may be manufactured from a generally non-conductive material or insulator, e.g., a dielectric substrate. 
   Jig  150  may electrically isolate each core  160  from one another on jig  150 . For example, the dielectric material of jig  150  may resist the transferring of electrical currents or magnetic fields from one core  160  to another core  160  on jig  150 , i.e., the dielectric material of jig  150  may have a high dielectric constant sufficient to isolate circuits  110  and circuit boards  100  under tests herein. 
   Alternatively, each core bed  152  may be individually electrically isolated. For example, a sleeve of dielectric material may electrically isolate each core bed  152 , or core beds  152  may form a sleeve, in which case sleeves or core beds  152  may be mounted to either a dielectric or non-dielectric substrate. 
   Example materials may include ceramics, porcelains, glasses, fiberglasses, plastics, and resin materials having high fiberglass content. For example, jig  150  may be manufactured from G 10 , a fiberglass resin with high fiberglass content. 
   Jig  150 ,  FIGS. 3 and 4 , may include one or more beds  152  for mounting cores  160 . Jig  150  may include bridging beds  156  between each core bed  152  for receiving a bridging section  112  between each circuit board  100 . Core beds  152  may be arranged in rows and columns on jig  150 . Core beds  152  may be fabricated so as to receive an array of cores  160  and corresponding circuit boards  100  which are bridged,  FIG. 4 , or individual circuit boards,  FIG. 5 . 
   4. Cores 
   For example, cores may be press-fitted into jig  150  or cores  160  may be glued into jig  150 . Cores  160  may be mounted to jig  150  using a compressible substrate, e.g., silicon adhesive or adhesive gaskets, which also may function as a compressible mount to level core  160  and absorb shocks during tester operation. 
   Core  160  may be mounted on table  52 , jig  150 , or integrated with circuit board  100 ,  FIG. 4 . For example core  160  maybe attached to jig  150  in core beds  152  so that the top surface of core  160  is level or above a top surface of jig  150 . Core  160  may protrude between approximately  5  thousandths and approximately  50  thousandths of an inch above top surface  151  of jig  150 , more specifically between approximately 10 thousandths and 30 thousandths on an inch, and still more specifically between approximately 15 thousandths and approximately 20 thousandths of an inch. 
   In another aspect of the invention, jig  150 ,  FIG. 4 , may support at least a portion of circuit board  100  so that circuit board  100  is in a position with respect to core  160  so as to maximally enhance an inductive field. For example, jig  150  may support circuit board  100  so that it is generally centered with respect to the height of a post  164  which may extent from the core  160  generally normal to jig  150 . Circuit board beds  152  may be a raised, recessed, or otherwise designated portion of jig  150  supporting a portion or all each circuit board  100 . 
   Core  160  may be a single piece core or may have multiple parts. For example, core  160  may include, but is not limited to, an E core, EC, ER, ETC, EER, PQ, EP, D, RM, post, plate, or pot core. Preferably, core  160  may be an E-type core, and specifically an RM core as shown in  FIG. 3  (part  160 ), preferably with a matching plate  210 . Alternatively, core  160  may be a post core. 
   Core  160  may be manufactured from ferrite or other suitable material with high magnetic permeability and low electrical conductivity which may enhance inductance in circuit  110  in the presence of an electrical current. 
   Core  160  may have a generally circular or oval shape with a major diameter between approximately 10 thousandths of an inch and approximately 6 inches, more specifically between approximately 20 thousandths of an inch and 2 inches, and still more specifically between approximately ½ inch and approximately 1 inch. Alternatively, core  160  may have a generally rectangular shape with a length between approximately 10 thousandths of an inch and approximately 6 inches, more specifically between approximately 20 thousandths of an inch and approximately 2 inches, and still more specifically between approximately ½ inch and approximately 1 inch. Cores may have a height between approximately 10 thousandths of an inch and approximately 4 inches, and more specifically between approximately 20 thousandths of an inch and approximately 2 inches, and still more specifically between approximately 3/16 inch and approximately ½ inch. 
   In one aspect, core  160  may have post  164  which is of a smaller diameter than circuit  110  so that post  164  may be received centrally by circuit board  100 . Post  164  may have a height greater than the thickness of circuit board  100 . Core  160  may partially surround circuit  110  and circuit board  100 . In addition, circuit board  100  may have slots or holes (not shown) for receiving portions of core  160  not located within circuit  110 . 
   5. Tester 
   One or more testers  60 ,  FIG. 1 , may be used to perform electrical tests on circuit boards  100 . Tester  60  may be integrated into carriage  50 , or tester  60  may be mounted to carriage  50 . Alternatively, testing machine  10  may use multiple carriages and multiple testers to test circuit boards  100 . Tester  60  may include a testing block  66 , cables, contacts, leads, a measuring tool, interface boards, and controllers. 
   Tester  60  may be able to perform a single electrical test, e.g., inductance or high potential, or tester  60  may be able to perform multiple tests including inductance, high potential, capacitance, resistance, and conductance. For example, the measuring tool may be an inductance meter or a high potential or dielectric withstand meter. 
   Tester  60  may include a carriage adapter  62 ,  FIG. 1 . Carriage adapter  62  may be a plate that is attached to carriage  50 . Carriage adapter  62  may be attached to carriage  50  using a secure means such as welds, rivets, bolts, or screws. For example, carriage adapter  62  may be attached to a front surface  64  of carriage  50  using one or more bolts. 
   Carriage adapter  62 ,  FIG. 1 , may be of such width to allow vertical clearance between a tester block  66  and carriage  50  so that the operation of one will not physically interfere with the operation of the other. For example, carriage  50  may include a drill  400 ; carriage adapter  62  may provide a vertical clearance between drill  400  and tester  60 . For example, carriage adapter  62  may have a width between approximately 1 inch and approximately 6 inches, more specifically between approximately 2 inches and approximately 4 inches, and still more specifically approximately 3 inches. 
   Carriage adapter  62 ,  FIG. 1 , may be shaped and modified with mounting set points, mounting holes, and mounting adapters so as to securely attach to carriage  50 . For example, tester  60  may be adapted to an existing PCB drilling machine or CNC machine. Carriage adapter  62  may be manufactured so that it will securely attach to an existing or new drilling machine, CNC machine, or other PCB manufacturing equipment. This may allow the CNC machines, e.g., PCB drilling machines, CNC tables, and CNC testers, to be upgraded with tester  60  by attachment of a carriage adapter  62  machined to securely attach to the manufacturing equipment. Carriage adapter  62  may allow manufacturing equipment to perform the original function with minimum impediment from tester  60  when tester  60  is deselected, not in use, or removed. 
   Carriage adapter  62  may be attached to a rail adapter  68 ,  FIG. 1 . Rail adapter  68  may be a planar plate that attaches to carriage adapter  62  on one planar surface and to a tester rail  70  on another planar surface. Carriage adapter  62  and rail adapter  68  may be attached using a secure means such as welds, rivets, bolts, or screws. Alternatively, rail adapter  68  may be directly attached to carriage  50 . Tester rail  70  may be mounted to rail adapter  68  or, alternatively, to carriage adapter  62 . 
   Tester rail  70 ,  FIG. 1 , may consist of two or more rails which move independently of one another in along a single axis. For example, tester rail  70  may be formed from a first rail  72  which may attach to tester rail adapter  68 . A second rail  74  may attach to first rail  72 . First  72  and second  74  rails may be joined at a rail track  76 . Rail track  76  may be a grove in first rail  72  or second rail  74  which allows a portion of one rail to engage with the other rail by seating partially inside the other rail within rail track  76 . First rail  72  and second rail  74  may move independently of one another along an axis parallel to rail track  76 . Rail track  76  may have one or more rail stops which limit the range of movement of one rail with respect to the other rail. Rail track  76  may include ball bearings, linear bearings, or low friction surfaces which enhance the ability of one rail to move independently of the other rail within rail track  76 . 
   Tester rail  70 ,  FIG. 1 , may be attached to a tester head mounting plate  78 . Tester head mounting plate  78  may have a first section  80  and a second section  82 . First section  80  of tester head mounting plate  78  may be generally planar and lie in a plane parallel to the z-axis of carriage  50 . For example, second rail  74  of tester rail  70  may be attached to first section  80  of tester head mounting plate  78 . Tester rail  70  and tester head mounting plate  78  may be orientated such that tester head mounting plate  78  may move in an axis generally parallel to the z-axis of carriage  50 . First section  80  of tester mounting plate  78  may be mounted to tester rail  70  using a secure means such as rivets, welds, bolts, or screws. 
   Second section  82  of tester head mounting plate  78 ,  FIG. 1 , may be generally planar in geometry and may lie in a plane generally perpendicular to and below first section  80  of tester head mounting plate  78 . First section  80  and second section  82  of tester head mounting plate  78  may be attached together using a secure means such as welds, rivets, bolts, or screws. Alternatively, tester head mounting plate  78  may be manufactured from a single piece of material so that first section  80  and second section  82  are of an uninterrupted piece of material. For example, tester head mounting plate  78  may be molded or cast from a single block of material. 
   An actuator  84  may engage with tester head mounting plate  78 ,  FIG. 1 . Actuator  84  may mount to an actuator mounting plate  86  which may be a generally planar plate lying in a plane generally perpendicular to the z-axis and above carriage  50 . Actuator  84  may engage tester head mounting plate  78  with a tester ram  88 . Tester ram  88  may extend from the bottom of actuator  84  generally along the z-axis so that tester ram  88  may engage with the top of tester head mounting plate  78 . The extension of tester ram  88  may translate tester head mounting plate  78  along the z-axis so as to select tester  60 . Tester ram  88  also may contract. Contraction of tester ram  88  may deselect tester  60  by translating along the z-axis away from circuit board  100 . Actuator  84  may extend and contract tester ram  88  using a pneumatic cylinder, servo motor, linear drive, or a stepper motor. Tester ram  88  may extend, and thus translate tester block  66  from the deselected position to the selected position, a predetermined distance, e.g., a tester ran stroke length. Tester ram stroke length may be between approximately ½ inch and approximately 10 inches, more specifically between approximately 2 inches and approximately 8 inches, and still more specifically between approximately 3 inches and approximately 5 inches. 
   In one embodiment, a CNC machine carriage, e.g., a DYNAMOTION machine with a single spindle SMART DRILL, is modified so that the existing spindle is removed and replaced with a LENZ z-axis assembly which may allow clearance to mount testers to the carriage and allows translation along the z-axis. Adapting a replacement z-axis assembly which has sufficient clearance may require mechanical and electrical modifications to the existing CNC machine. For example, the replacement z-axis assembly may require setting up and wiring the z-axis assembly into the existing CNC machine position feedback system. A DC servo amplifier may have to be setup and calibrated. In addition, the CNC control system, including control software, frequency converters, and drive hardware, may require calibration, tuning, and testing. 
   The replacement z-axis assembly may require mechanical modifications to allow fitting of the tester. In one embodiment, the z-axis assembly, e.g., a LENZ z-axis assembly, is disassembled and one or more holes are drilled so a tester may be mounted. 
   For example, the tester may be a tool holder magazine, e.g., a DYNAMOTION tool holder magazine, which may include mechanical guide rails and a tester ram that can be used to lift and lower the tester, selecting and deselecting the tester, respectively. The mechanical guide rails may include bearings, e.g., linear bearings. In addition to raising and lowering the assembly, the tester ram may provide the shock absorption when the tester block engages with the circuit board, thus functioning as a compressible air bladder to cushion engagement and account for slight undulations in the jig. 
   Control of the tester ram  88  may be integrated into controller  600 , i.e., the CNC controller. For example, air lines may be connected to tester ram  88  and an air solenoid and regulator (not shown) may be electrically connected to outputs of controller  600  so that controller  600  may activate the air solenoid. 
   6. Tester Block 
   Tester block  66 ,  FIGS. 6 and 7 , may be of a generally rectangular geometry. Tester block  66  may be of non-rectangular geometries also. The geometry and size of tester block  66  may be in part determined by the geometry of circuit board  100  and the geometry of circuits  110  on circuit board  100 . For example, circuit board  100  may include mounted components. In this case, tester block  66  may have geometry which may not disturb or contact circuits, components, or other circuit boards which are not being tested by testers  60  when tester block  66  translates over circuit boards  100  or engages circuits  110  or circuit boards  100 . 
   Tester block  66  may attach to tester head mounting plate  78 ,  FIG. 1 , either directly or through a block adapter plate  90 . For example, tester block  66  may have an upper surface which may attach to block adapter plate  90  which may have a generally planar geometry and may lie in a plane generally perpendicular to the z-axis. In turn, block adapter plate  90  may attach to second section  82  of tester head mounting plate  78 , so that tester block  66  lies below tester head mounting plate  78 . 
   Tester block  66  may be manufactured from a generally non-conductive material or insulator. Such material may have a high dielectric constant. Example materials may include ceramics, porcelains, glasses, fiberglasses, plastics, and resin materials having high fiberglass content. For example, tester block  66  may be manufactured from G 10 , a fiberglass resin with high fiberglass content. 
   Tester block  66 ,  FIG. 8 , may be translated along the z-axis so that it engages circuit board  100 . The extension of tester ram  88  may cause tester block  66  to translate along the z-axis so that it is in testing range or proximity of circuit board  100 . Translation of tester block  66  may involve translation of both carriage  50  and extension of tester ram  88 . Also, the translation of carriage  50  along the z-axis may cause carriage adapter  50 , rail adapter  68 , tester rail  70 , tester head mounting plate  72 , block adapter plate  90 , and thus tester block  66  to translate in along the z-axis. 
   For example, tester ram  88 ,  FIG. 1 , may select tester block  66  by extending and translating tester block  66  toward circuit board  100 . Carriage  50  may translate toward circuit board  100  along the z-axis. When tester block  66  contacts circuit board  100 , circuit board  100  may resist further translation and continued translation by carriage  50  along the z-axis may cause tester ram  88  to be compressed. Compression of tester ram  88  may signal controllers  600  or computer  610  that tester block  66  has engaged circuit board  100 . Signaling of controller  600  may be through an engagement switch  92  mounted independently of tester head mounting plate  78  such that movement of tester head mounting plate  78  with respect to first rail  72  of tester rail  70  may cause engagement switch  92  to signal controller  600 . Engagement switch  92  may be a mechanical switch or an optoelectrical switch. 
   Alternatively, tester block  66  may be attached to carriage  50  directly or through a mounting adaptor and z-translation of carriage  50  may be used to select and deselect tester block  66 . A switch may be use to determine when tester block  66  has engaged with circuit board  100  For example, an optical or mechanical sensor may detect when tester block  66  has made contact with circuit board  100 . Alternatively, feedback positioning system  54  may detect when tester block  66  has been translated to a position which engage tester block  66  with circuit board  110 . 
   In one embodiment, the tester may be mounted on a linear rail assembly, e.g., a DYNAMOTION tool holder magazine. The tool holder magazine may include one or more optoelectrical switches, e.g., a primary optoelectrical switch and a backup optoelectrical switch. The optoelectrical switches may be calibrated and positioned on the tool holder magazine so that engagement of the tester block with the circuit board may trigger the one or more of the optoelectrical switches, creating a engagement signal, i.e., a test trigger pulse, which may be sent to a controller, e.g., the CNC controller, to start, i.e., trigger, a testing cycle. 
   Tester block  66 ,  FIG. 1 , may include or more electrical testers. For example, a tester block  66  may include an inductance tester or a high potential tester. In another aspect of the invention, tester block  66  may include a resistance tester and a capacitance tester. 
   In one aspect of the invention, tester block  66  may include a shoe (not shown). The shoe may engage circuit board  100  during testing to hold it securely in place and help prevent damage to circuit board due to misalignment. For example, the shoes may be one or more strips of compressible material, e.g., rubber or spring mounted bars, which engage with a circuit board  100  and jig  150  as tester block  66  translates toward circuit board  100  in the z-axis. The shoes may partially flatten, or level, circuit board  100  to the surface of jig  150 . 
   In another aspect of the invention, tester block  66  may include one or more cleaner nozzles (not shown). The cleaner nozzles may blow air or spay a cleaning fluid across the surface of a circuit board or tester block. The air or cleaning fluid may clean the surface and dislodge foreign matter which may interfere in testing. For example, the cleaner nozzles may blow air having a pressure at the nozzle tip between approximately 5 psig and approximately 20 psig. In another aspect of the invention, testing machine  10  may include a cleaning brush (not shown) to remove foreign material from circuit boards  100 , tester block  66 , jig  150 , or cores on tester block  66 . 
   6.1 Inductance Tester 
   Tester block  66  may include an inductance tester. In one aspect of the invention, tester block  66  may be an inductance tester block,  FIG. 1 . In another aspect on the invention, the inductance tester may be included in tester block  66  along with one or more other testers. 
   Inductance tester may include a plate  210  which may be mounted to raised area  224  of tester block  66 ,  FIG. 6 . The plate may be manufactured from ferrite or other suitable material with high magnetic permeability and low electrical conductivity which may enhance an inductive field about circuit board  100  or circuit  110  in the presence of an electrical current. Plate  210  may engage with core  160  when tester block  66  is translated along the z-axis, and plate  210  and core  160  may together form a core assembly with circuit board  100  as shown in exploded view in  FIG. 3 . 
   Alternatively, plate  210  and core  160  may be interchanged. For example, plate  210  may be mounted to the substrate, e.g., jig  150 , and core  160  may be mounted to tester block  66 . 
   In still another aspect, testing machine  10  may not include plate  210 . For example, core  160  may be a post core and may be mounted to tester block  66 . Core  160  may be received by circuit board  110  so core  160  is translated so as to be positioned generally centrally within circuit  110  in circuit board  100 . 
   Core  160 ,  FIG. 3 , and plate  210 ,  FIG. 6 , may be mounted on a compressible mount  220 . For example, plate  210  may be mounted to compressible mount  220  which in turn may be mounted to a bottom face  222  of tester block  66 . Bottom face  222  of tester block  66  may include a raised area  224  on which plate  210  or compressible mount  220  may be mounted. Raised area  224  may be generally planar, and raised area may be generally rectangular or follow, at a scale, the perimeter of secondary core  210 . Raised area  224  may extend beyond bottom face  222  of tester block  66  between approximately 1/16 inch and 1 inch, more specifically between approximately ⅛ inch and approximately ½ inch, and preferably approximately 3/16 inch. 
   Compressible mount  220 ,  FIG. 6 , may be compressible so that when tester block  66  engages circuit board  100  or plate  210  engages or contacts core  160 , compressible mount  220  may compress along the z-axis. Compressible mount  220  also may allow plate  210  to level so that it lies in the same plane as circuit board  100 . For example, if core  160  is present, the contact of plate  210  and core  160  may compress compressible mount  220  so that plate  210  and core  160  lie in the same plane and make level contact with each other which may increase testing accuracy. 
   Circuit board  100  and jig  150  may be on table  52 ,  FIG. 1 , which may be level. However, undulations in table  52  may cause circuit board  100  or core  160  to not align properly with tester block  66 . Misalignment may result in small air gaps between core  160 , plate  210 , and circuit board  100 . Such air gaps may cause error in testing circuit board  100 . This may lead to some circuits being falsely determined as defective or being falsely determined as passing. The compression of compressible mount  220 ,  FIG. 2 , during engagement of tester block  66  with circuit board  100  and core  160  with plate  210 , may level and align core  160 , tester block  66 , circuit board  100 , and plate  210  so that small air gaps may be removed or reduced. 
   Alternatively, compressible mount  220  may be placed between tester block  66  and tester head mounting plate  78  or tester block adapter plate  70 , and plate  210  may be attached directly to bottom face  222  of tester block  66 . So, engagement of tester block  66  with circuit board  100  or core  160  with plate  210  may cause tester block  66  to compress compressible mount  220  against tester block adapter plate  90  or tester head mounting plate  78 . The compression of compressible mount  220  may allow tester block  66  to align, level, and properly engage with circuit board  100 . 
   Compressible mount  220 ,  FIG. 2 , may be manufactured of a compressible material that is generally non-conductive and non-magnetic. If compressible mount  220  is too thick, it may allow translation in axes other than the z-axis when compressible mount  220  is compressed. If it is too thin, it may not compress sufficiently and may allow tester block  66  to over-translate in the z-axis before engagement switch  92  signals controller  600  or computer  610  to stop z-translation. In addition, if compressible mount  220  is too thin, it may not allow tester block  66  or secondary core  210  to properly level and align with respect to circuit board  100  and core  160 . Also, a too thin compressible mount  220  may not proper absorb mechanical shocks when tester block  66  engages circuit board  100  or core  160  engages secondary core  210 ; excessive mechanical shocks may damage circuit board  100  or testers  60 . Over-translation along the z-axis also may damage circuit board  100 , tester  60 , tester block  66 , core  160 , secondary core  210 , and test pins  230 . 
   In one embodiment, compressible mount  220 ,  FIG. 2 , is manufactured from a compressible material having an uncompressed thickness between approximately 1/32 and approximately ¼ inch, more specifically between approximately 3/64 and approximately ⅛ inch, and still more specifically approximately 1/16 inch thick. Materials that compressible mount  220  may be manufactured from include but are not limited to neoprene rubber, silicone rubber, urethane nitrile, butyl rubber, and non-conductive foams. 
   Alternatively, compressible mount  220 ,  FIG. 2 , consists of springs mounted to the primary core and the tester block. The springs may be metallic, e.g., spring steel, or of a polymeric material with sufficient springiness to absorb contract shock from core engagement and promote level core engagement. 
   Tester block  66  may include two or more test leads or test pins  230 ,  FIG. 2 . Engagement of tester block  66  with circuit board  100  may cause test pins  230  to make contact with contact pads  162  on circuit board  100 . Test pins  230  may be spring loaded  238  so that if compressible mount  220  is compressed along the z-axis, test pins  230  may compress so as to not over-translate along the z-axis. Over-translation of test pins  230  against circuit board  100  may damage circuit board  100 , test pins  230 , or tester block  66 . Tester block  66  may have pin wells  232 ,  FIG. 6 . Pin wells  232  may be of a larger diameter than pins  232  so test pins  230  may recess into tester block  66 . 
   Test pins  230 ,  FIG. 2 , may form a conductive path between contact pads  162  on circuit board  100  and two or more test cables  234 ,  FIG. 1 . A test connector  239 ,  FIG. 2 , e.g., a banana plug, may receive test cables  234  and complete an electrical connection to test pins  232 . Test cables  234  may form a conductive path to a tester controller  620 ,  FIG. 11 , e.g., inductance tester controller  622 . Test pins  230 ,  FIG. 8 , may have conical tips  236  which make contact with circuit board contact pads  162 . Conical tips  236  may localize engagement pressure of tester block  66  or the expansion force of test pin springs  238  in a small area so that test pins  230  make an electrical connection with contact pads  162  which has a very low electrical resistance. Test pins  230  may have other geometries which may make good electrical contact with contact pads  162 , e.g., spherical test pins. 
   Inductance tester controller  622 ,  FIG. 11 , may pass an electrical current through circuit board  100  and circuit  110  via test pins  230  and contact pads  162  on circuit board  100 . Inductance tester controller  622  may perform electrical tests on circuit board  100  when tester block  66  engages circuit board  100  and inductance tester controller  622  may determine whether circuit board  100  is defective or approved, i.e., fails or passes inductance tests. 
   The inductance tester may be a combination inductance, capacitance, and resistance tester, e.g., a HEWLETT PACKARD PRECISION LCR unit. The inductance tester may perform one or more electrical tests. For example, the inductance tester may test inductance, conductivity, resistance, or capacitance. 
   The inductance tester may require one or more interfaces to the CNC controller or computer. For example, the inductance tester may be designed for component sorting and may produce a part measured low, or PML, and part measured high, or PMH, signal after testing each circuit board. Inductance tests for circuit boards may allow a minimum and maximum inductance specification. If circuit board inductance falls with in the minimum and maximum specification, the circuit board may pass the test. Otherwise, the circuit board may fail the inductance test and not be approved. The PML and PMH levels for the inductance tester may be set to the circuit board passing inductance specifications; so that a PMH or PML signal will indicate that the circuit board under test falls outside the passing inductance range. The PMH and PML signals may be combined as a single signal to the CNC controller or computer to indicate that the circuit passed or failed the inductance test. 
   The PMH and PML signals may be combined using a relay and fault test board. The relay and fault test board may combine the PMH and PML signals using an AND gate, NAND gate, or equivalent logic. In one embodiment, the PMH and PML signals are combined using a NAND gate. The NAND gate may interface to the controller or computer, or may drive a transistor, relay, and inverters or buffer logic to provide compatible drive levels, e.g., 24 volts, and electrical isolation with the controller  600  or computer  610 ,  FIG. 6 . The relay and fault test board may deliver a bad part test signal to the controller or computer when the circuit board fails the inductance test. The relay and fault test board may signal an operator when a board fails a test, e.g., a buzzer or light. A circuit is shown in  FIG. 9A  for interfacing the PML and PMH signals to a controller or computer. 
   The inductance tester may produce a measurement or test result signal, i.e., a pass or fail signal, for the circuit board under test which may be delayed from the test. A trigger control board may condition and synchronize the test signal with the CNC controller or computer so that test signals are sent neither prematurely nor too late. 
   For example, the trigger control board may include an AND gate, inverter, and positive edge triggered D-type flip flop. The AND gate may combine the engagement or test trigger pulse from optoelectrical switches  94 , an end of measurement signal from the controller  600 ,  FIG. 11 , or computer  610 , and the bad part test signal from the relay and fault test board. The trigger control board may include inverts, buffers, transistors, and relays to provide compatible drive levels, e.g., 24 volts, and electrical isolation with the CNC controller or computer. The controller  600  or computer  610  may produce a clear test signal which may clear, or reset, a bad part test signal from the trigger control board. A circuit is shown in  FIG. 9B  for interfacing optoelectrical switches  94 , end of measurement signal, and bad part test signal with the controller or computer. 
   Inductance tester  200  may include a speed check and test faulty interface board. The speed check and test faulty interface board may synchronize the controller or computer and tester to prevent the controller or compute from running too fast or becoming unsynchronized and starting to test a second circuit board before tests on a first circuit board are complete. 
   For example, under normal conditions, the machine may be designed so that a new trigger, or engagement pulse, should not be produced by optoelectrical switches  94 ,  FIG. 1 , before an end of measurement signal is produced for the circuit board currently under test by the inductance tester. If this were to occur, controller  600 ,  FIG. 11 , may be running the machine too fast and the inductance tester may still be testing the circuit board under test. 
   The speed check and test faulty board may include a positive edge triggered flip flop and one or more inverters, buffer logic, transistors, diodes, and relays to provide compatible drive levels, e.g., 24 volts, and electrical isolation with the controller  600  or computer  610 ,  FIG. 11 . The flip flop may trigger a fault or test too fast condition if a trigger pulse is received while end of measurement signal is still at a logic level which indicates testing is under way. The interface board may cause a signal, e.g., an audible alarm or visual indicator, to be sent to an operator should a fault occur. A circuit is shown in  FIG. 9C  detecting testing faults or testing too fast conditions. 
   6.2 High Potential Tester 
   Tester block  66  may include a high potential tester. In one aspect of the invention, tester block  66  may be a high potential tester block,  FIG. 7 . In another aspect of the invention, tester block  66  may include the high potential tester and one or more other testers. 
   The high potential tester may include test leads or test pins  302 ,  FIG. 7 . When tester block  66  translates along the z-axis, test pins  302  may contact circuit board  100 , e.g., at contact pads  162  on circuit board  100 ,  FIG. 8 . Continued translation of carriage  50 ,  FIG. 2 , may cause tester ram  88  to compress which may cause engagement switch  92  to signal controller  600  or computer  610  that test pins  302  have contacted circuit board  100 , thus engaging tester block  66  with circuit board  100 . Controller  600 ,  FIG. 11 , may stop translation of tester block  66 ,  FIG. 2 , toward circuit board  100  or reverse the direction of translation. As with inductance tester  200 , test pins  302  may be spring loaded and may recess into pin wells  232  to prevent damage to circuit board  100  or high potential tester  300  if tester block  66  is over translated along the z-axis toward circuit board  100 . 
   Test pins  302 ,  FIG. 7 , may have a conductive path to test cables  234 ,  FIG. 1 , which may form a conductive path to high potential tester controller  624 ,  FIG. 11 . Referring to  FIGS. 1 , and  7 , high potential tester controller  624  may pass a high potential electrical current through circuit board  100  via test pins  230  and contact pads  162  on circuit board  100 . High potential tester controller  624  may pass a high potential electrical current through circuit board  100  via test pins  302  at other areas of circuit board  100  other than contact pads  162 , e.g., to test substrate dielectric withstand. High potential tester controller  624  may perform electrical tests, e.g., dielectric withstand, on circuit board  100  when tester block  66  engages circuit board  100 , and high potential tester controller  624  may determine whether circuit board  100  is defective or approved, i.e., fails or passes high potential tests. 
   The voltage potential of the electrical current used by high potential tester controller  624 ,  FIG. 11 , may be between approximately 1,000 volts and approximately 30,000 volts, more specifically between approximately 1,200 volts and approximately 10,000 volts, still more specifically between approximately 1,500 volts and approximately 6,000 volts. In one embodiment, voltage potential is between approximately 2,000 volts and approximately 3,000 volts, and preferably approximately 2,200 volts. In one embodiment, high potential tester  300  may ramp voltage between one or more predetermined voltages. 
   High potential tester controller  624 , high potential tester  300 , tester block  66 , and test cables  310 ,  FIGS. 1 and 7 , may include insulation, safety interlocks, and insulated wire guides. For example, test cables  310  may be capable of withstanding high voltages, e.g., 30,000 volts. One or more test cables  310  may be able potential source lines, and one or more test leads  310  may be return lines. Test cables  310  may pass through wire guides  320  between tester block  66  and high potential tester controller  624 . Wire guides  320  may protect test cables  310  and also may prevent outside electrical or magnetic interference with tester signals. Wire guides  320  may include wire conduits. Wire conduits may be manufactured from a protective material which may be non-conductive. For example, wire conduits may be manufactured from plastic pipe such as PVC, ABS, polyurethane, or TEFLON pipe. 
   The high potential tester controller  624 ,  FIG. 11 , may be a HYPOT III AC/DC withstand voltage tester, manufactured by ASSOCIATED RESEARCH, model 3665. The high potential tester controller  624  may test between approximately 2,000 and approximately 3,000 volts. The high potential tester controller  624  may be able to measure residual current flow in a circuit board under test. Residual current flow measurement may be used to determine if test pins  302  have engaged with test contacts  162  properly. The high potential tester controller  624  may be able to measure residual current flow in AC more or in DC mode. The high potential tester controller  624  may allow setting of the test voltage, ramp time, and current flow. The high potential tester controller  624  may include multiple tester inputs so that one high potential tester controller may test multiple circuit boards and tester blocks, e.g., a machine with multiple tester heads may test multiple circuit boards at the same time or one tester may operate multiple tester machines. 
   The high potential tester  300  may include an interface board  630 ,  FIG. 11 . Interface board  630  may interface pass and fail signals for tests to controller  600  or computer  610 . In addition, interface board  630  may synchronize high potential tester controller  624  and the controller  600  or computer  610 . Furthermore, interface board  630  may include safety interlocks or may interface safety interlock signals between high potential tester  300  and controller  600  or computer  610 . 
   Interface board  630  may include one or more relays to provide compatible drive levels, e.g., 24 volts, and electrical isolation with the CNC controller or computer. For example, the high potential tester interface board may interface reset, test, fail, safety interlock, and tester head select functions from controller  600  or computer  610  to high potential tester controller  624  and testing machine  10 . 
   7. Drill 
   Drill  400 ,  FIG. 1 , may be mounted to carriage  50  or may be integrated into carriage  50 . Drill may include a spindle  410  and one or more air supply lines  420 . Drill  400  may be translated over circuit board  100  by carriage  50 . Carriage  50  may be translated along the z-axis toward circuit board  100 , so that drill  400  may be translated toward circuit board  100 . In one embodiment, drill  400  is a DYNAMOTION single spindle SMART DRILL with an air bearing spindle. 
   Carriage  50 ,  FIG. 1 , may include a pressure foot  430  mounted in a plane generally parallel to circuit board  100  and between circuit board  100  and carriage  50 . A pressure foot cylinder may extent a pressure foot ram attached to pressure foot  430  which may translate pressure foot  430  along the z-axis toward circuit board  100 . 
   In order to drill circuit board  100 ,  FIG. 1 , carriage  50  may extend drill  400  toward circuit board  100  along the z-axis. The pressure foot ram may extend pressure foot  430  toward circuit board  100  so that pressure foot  430  may be in close proximity to circuit board  100  along the z-axis. Drill  400  may include a bit, e.g., a drill bit or router bit, which may destroy at least a portion of circuit board  100  which may include a portion of circuit  110 . Preferably, drill  400  may destroy circuit  110  by ablating sufficient material from circuit board  100  to open circuit  110 . Pressure foot  400  may include a debris removal system  58  which may remove material ablated from circuit board  100  by drill  400 . Drill  400  may use a spindle  410  to rotate a bit in order to destroy circuit board  100 . 
   8. Controllers 
   The invention may use one or more controllers to coordination and control the movement and actions of components of the testing machine, i.e., automate the machine and testing. The controllers  600  may be a CNC controller,  FIG. 11 , a personal or industrial computer  610 , or a combination. Components under the control of controllers may include a CNC machine  640 , carriage  50 , tester block  66 , inductance tester controller  622 , high potential tester controller  624 , drill  400 , and tester ram  88 . One controller may control multiple components, e.g., a single controller may control carriage  50  and drill  400 . Alternatively, one or more controllers may be slaved to another controller or a computer. 
   For example, a personal computer  610 ,  FIG. 11 , may control a controller  600  or may directly control machine  640 . Personal computer  610  or CNC controller  600  may control carriage  50  and drill  400 . Furthermore, personal computer  610  or CNC controller  600  may control one or more tester controllers. 
   Tester controllers may include inductance tester controller  200 ,  FIG. 11 , and high potential tester controller  300 . Interface boards  630  may interface tester controllers and one or more other controllers. 
   Controller  600  may be a SIEB and MEYER CNC controller. CNC controller  600  may control drill  400 , CNC machine  640 , drill  400 , and carriage  50 . Interface boards  630  may allow testers  60  to be interfaced with controller  600  or personal computer  610 . 
   Software on computer  610  or controller  600  may direct and synchronize the actions of the testing machine  10  and tester controllers in response to operation choices, testing results, and jig or circuit layout, and circuit board type and specifications. 
   9. Test Operation 
   An example operation sequence of testing machine  10  is shown in block form in  FIG. 10 . An operator may set up a test machine  10  with jig  150 , tester  60 , circuit boards  100 ,  FIG. 1 , and load a program on controller  600  or computer  610 ,  FIG. 11  (step  700 ,  FIG. 10 ). Tester  60 , e.g., inductance tester  200  or high potential tester  300 , may be loaded with testing parameters which may define testing limits for determining whether a circuit board is approved or defective (step  704 ,  FIG. 10 ). The program may be started (step  708 ,  FIG. 10 ), referring to  FIG. 8 , carriage  50  may be translated by CNC machine  640  so that tester block  66  is over a circuit board  100  on jig  150  (step  712 ,  FIG. 10 ). Controller  600  may cause tester ram  88  to extend so that tester block  66  is translated along z-axis toward circuit board  100 , selecting tester block  66 ,  FIG. 1 . Carriage  50  also may be translated along the z-axis so the tester block  66  engages circuit board  100  (step  716 ,  FIG. 10 ). 
   Carriage  50  may continue extending after tester block  66  engages circuit board  100 ,  FIG. 1 . Compressible mount  220 ,  FIG. 6 , may be compressed, which, if plate  210  is present, may level plate  210  with respect to core  160  or circuit board  100 ,  FIG. 8 . Since tester block  66  may be unable to translate any further because of circuit board  100 , it may force tester ram  88  to compress,  FIG. 1 . This may cause opto-switch  94  to sense that first rail  72  has moved with respect to second rail  74  of tester rail  70 . This may cause an engagement signal, or trigger pulse, to be sent to controller  600  or computer  610 , e.g., via interface board  630 ,  FIG. 11  (step  720 ,  FIG. 10 ). 
   Controller  600 , computer  610 , or interface boards  630 ,  FIG. 1 , may cause inductance tester controller  622  or high potential tester  624  to conduct electrical tests (step  724 ,  FIG. 10 ). If circuit board  100  passes electrical tests, (step  726 ,  FIG. 10 ), tester ram  88  may contract, deselecting tester block  66 , and carriage  50  may translate tester block  66  away from circuit board  100  along the z-axis (step  730 ,  FIG. 10 ), disengaging from circuit board  100 . Carriage  50  then may be translated so that tester block  66  is over another circuit board  100 ,  FIG. 1  (step  712 ,  FIG. 10 ) and may continue to conduct electrical tests on other circuit boards  100 . 
   If circuit board  100  does not pass electrical tests, controller  600  or computer  610  may cause circuit board  100  to be tested one or more additional times (step  734 ,  FIG. 10 ). If circuit board  100 ,  FIG. 1 , passes additional electrical tests, circuit board  100  may be approved (step  726 ,  FIG. 10 ) and testing of other circuit boards may continue. 
   If circuit board  100 ,  FIG. 1 , fails the additional tests, controller  600  or computer  610  may cause circuit board  100  to be destroyed. Alternatively, controller  600  or computer  610  may cause circuit board  100  to be destroyed after failing electrical tests the first time without additional testing. 
   Alternatively, if circuit board  100  fails electrical tests, controller  600  or computer  610  may notify an operator and deselect and park tester (step  772 ,  FIG. 10 ). Controller  600  or  610  may have a settable flag or option determining whether to allow operator interaction (step  770 ,  FIG. 10 ). The operator may inspect circuit board  100  for dirt and clean circuit board  100  (step  774 ,  FIG. 10 ). The operator may direct controller  600  or computer  610  to destroy circuit board  100  (step  742 – 746 ,  FIG. 10 ) or retest circuit board  100  (step  734 ,  FIG. 10 ). The operator may make this selection using an input device, e.g., a keyboard or one or more buttons or switches. 
   If circuit board  100  fails electrical tests and controller  600  or computer  610  or the operator determines to destroy circuit board  100 , controller  600  or computer  610 ,  FIG. 11 , may deselect tester  60  (step  738 ,  FIG. 10 ) and translate carriage  50  so that drill  400  is over defective circuit board  100  (step  742 ,  FIG. 10 ). Drill  400  then may destroy circuit board  100  or render it generally unserviceable by ablating material from defective circuit board  100  (step  746 ,  FIG. 10 ). 
   Destroying defective circuit board  100  may increase a consecutive defective circuit board counter. If the consecutive defective circuit board counter exceeds a preset limit (step  750 ,  FIG. 10 ), controller  600  or computer  610  may signal the operator as to a possible machine malfunction (step  754 ,  FIG. 10 ). Controller  600  or computer  610  then may deselect and park tester  60  (step  758 ,  FIG. 10 ). The preset consecutive defective circuit board limit may be entered by an operator or determined according to the circuit board type being testing. For example, the preset consecutive defective circuit board limit may be between 1 and 4, and preferably 3. Otherwise, if the consecutive defective circuit board counter does not exceed the preset consecutive defective circuit board limit, testing machine  10  may continue testing other circuit boards. 
   Testing machine  10  may test every circuit board  100  on jig  150  or a sampling of circuit boards  100 . For example, high potential testing may be harmful to circuit board  100  or may alter the electrical or physical characteristics of circuit board  100 , whereas inducatance testing generally may not. So, testing machine  10  may inductance test most circuit boards  100  but high potential test a smaller proportion of circuit boards  100 . 
   For example, during the development of a circuit board from a prototype stage to full production, most or all prototype boards may be high potential tested in order to determine design criteria important for proper board operation, e.g., dielectric withstand of substrate and possible arcing points. However, once the design criteria are determined, e.g., boards manufactured according to the design criteria generally pass high potential testing, only samples or a small proportion of the circuit boards manufactured may be high potential tested. 
   In one aspect of the invention, a defective circuit board  100  may be examined or analyzed to determine if a design flaw is responsible for the failure of circuit board  100  to pass the electrical tests. For example, if circuit board  100  fails high potential testing or inductance testing, examination of circuit board  100  may reveal a flaw in board design or choice of board materials. The design may be revised and the flaw eliminated, removed, or a work-around for the flaw may be determined. Circuit boards may be produced which do not have the design flaw. Circuit boards produced from the modified design, or subsequent designs which do not include the flaw, may not require individual testing. 
   10. Conclusion 
   While the foregoing written description of the invention enables one of ordinary skill to make and use what is considered presently to be the best mode thereof, those of ordinary skill will understand and appreciate the existence of variations, combinations, and equivalents of the specific exemplary embodiments and methods herein. The invention should therefore not be limited by the above described embodiments and methods, but by all embodiments and methods within the scope and spirit of the invention as claimed.