Incorporating BR technology is considerably more expensive than 
     standard MLB PCB fab costs. (Considering the special material copper
     foil purchasing, additional image, etch, conformance ohm value 
     verification)
        One of the main PCB attributes that require BR technology is 
     available component real estate. Some (tight) designs cannot allow
     for discrete resistors. Then the design would warrant technique to 
     allow for resistors. (They're considerably small and if buried, could
     allow for surface mounts or surface circuitry to pass over.
     (Pull up and pull down resistor terminations are also commonly being
     used for this. i.e. ECL, TTL...etc.)
            
        Tolerances....Hmmmm. The sheet resistances are available in like
     25, 50, 100, 250, and 1000 Ohm/SQ. 25 Ohm material is thicker than the
     1000 and is easier to achieve an anticipated +/- 10% process.

        You can direct your questions to Ohmega Technologies at 
     (310) 559-4400. They're the Ni/P manufacturer and can assist you on
     any technical design related questions you may have.
     Person to talk to is Bruce Mahler.


        DHoover
   
______________________________ Reply Separator _________________________________
Subject: Buried Resistors and their tolere
Author:  [log in to unmask] at SMTPLINK-HADCO
Date:    8/16/95 10:11 AM


Thank you for the replies on buried resistors. Is it an expensive techniqe ? I
assume it is, or everyone would be using it. Aslo, what kind of tolereanceance
do the buried resistors have ?