Hey Doug:
     
     What the hell are FlyBack voltages?
     
     -John


______________________________ Reply Separator _________________________________
Subject: Re: Auto-insertion spacing
Author:  [log in to unmask] at internet-mail
Date:    05/02/96 15:02


REPLY:    Kitty,
     
          Book on clearances for Agencies.....
     
          We have had significant interface with the agencies listed 
          below, so I will attempt to outline for you.  If you need 
          more specific info please send, or call to 
          [log in to unmask], or 303-790-4445 x5216.
     
          VDE/CE requires tighter clearance specifications based upon 
          Voltages.  All Primary to Primary clearances between traces 
          s/b 3mm (.120")[i.e. neutral to common to hot]. This 
          clearance holds up until you go thru a xformer, or bridge 
          type device, and cut your voltages to DC voltage. Keep in 
          mind all parts of the component body when planning 
          clearances-NOT just the traces/pads. We have been killed 
          several times by heatsink hardware-to-chassis violations
          of < 6mm even when we took so much time with the PCB 
          clearances.
          Also... If you have FlyBack voltages that increase in an 
          Xformer, there may even be greater spacing requirments for 
          those higher voltage traces.
     
          Primary to secondary seperation requires 6mm 
          (.240")[i.e.neutral to digital signal trace in secondary]. 
          Plan on compressing all AC into one area that you can 
          surround with a 6mm keep-out area, This would also include 
          internal planes, better to completely clear out any internal 
          copper if your design is M/Layer.
     
          UL/CSA clearances are less rigid, but we have always planned 
          on following 3mm wherever possible just to be safe.
     
     
          RADIAL COMPONENTS
          =================
          Added note....
               When we have come across problems getting A.I. rules
          from our overseas factories (common freakin' problem!), we 
          have requested the machinery brands, and actually called the 
          machinery reps to get copies of the A.I. rules that should 
          be followed.
          There are very specific tooling requirements for all A.I. 
          machines as well as comp-to-comp spacing.
          We actually incorporated these clearances into our libraries 
          to speed up future designs, and it has been well worth the 
          time to edit the lib files.
          Keep in mind also that you have Clinched leads underneath 
          the components that can cause shorts with opposing clinched 
          leads on the bottom side of the PWA.  Machines can be set-up 
          for different types of clinching options.
     
                     /
                    O
                             top view of typical 5mm radial device
                    O        with 30deg. lead clinch angle.
                 / /....problem
                O        area-will gather solder, and short!
     
                O
               /
     
          hope this helps.
          Les.
     
     
Hi to all!
     
This is a great place to get excellent information.  I need some 
info ASAP.  I'm working on a board that is going to be manufactured 
over-seas and can't get this information from that manufacturer.  I 
have some good guidelines for auto-inserting axial components and 
DIPs, but I need to know the spacing requirements for radial 
components (caps, transistors, 1/4W & 2W resistors that are stood 
up).  Can anyone help me out?
     
This board also has to meet UL approval per UL/CSA/CE/VDE for 
250VAC.  I am using 100mil trace widths with 100mil air gaps 
minimum, sound good to you?
     
Hope you don't mind all my questions.  More than that, I hope you 
don't mind answering all my questions because I'm sure I'll be 
asking alot more.  That's what we're here for, right? 
     
    Thank You again!
    Kitty