21.10.99
                                          A.Komar
         
              REMARKS TO THE PROBLEMS OF FUTURE
                    EST BOARD PRODUCTION
                    (LPI group, Moscow)                            
    
1. LPI received in mid-September a large party of DuPont kapton
                   from CERN (about 6500 m)
      sufficient to produce (anew) all EST boards for HEC.

2. LPI produced (up to 10.10.99) 114 EST boards from DuPont kapton
   with the OLD sizes of the holes. 
   After 10.10.99 production process was stopped.
   Examination of the produced boards showed that the dielectric
   properties of DuPont kapton is very good. 
   During HV testing the observed leakage currents were 
                 on the level 3-4 nA.
   
3. The most acute problem now is certainly determination of
   the relative shrinkage EST boards with respect to Cu plate:
        a) for EST boards produced from DuPont kapton 
     (to realize this task LPI has brought to this meeting
           2 boards for TRIUMF and 2 boards for MPI) 
        b) for EST boards produced from GTS kapton at TRIUMF

4. Preliminary estimate of the relative shrinkage can be done using 
           table values of thermal expansion coefficients
         for Cu and polyimide (PI) at room temperature(!):
          K(Cu)=1.67*10-5 mm/mm/K;  K(PI)=3.5*10-5 mm/mm/K; 
                               then   
                    RELATIVE SHRINKAGE = 6 mm   
     
   If one takes into account that thermal expansion coefficient
   for Cu decreases, when temperatures become lower (~100K), whereas
   it is not the case (to our knowledge) for PI, 
                               then 
               relative shrinkage becomes even larger:
                    RELATIVE SHRINKAGE = ~8 mm  

   But all these estimates are valid for pure kapton, not sandwich
                      CLK-glue-PI-glue-CLK

5. In view of the new facts (appearance of tears in the guard zones
   of holes in cold) the opinion was expressed that LPI should change
            its technique of making holes in EST boards
                    FROM CUTTING TO PUNCHING

   From LPI point of view enlarging sizes of the oval holes completely
   solves the problem. Different quality of hole borders (if any) in
   various technique in this case is NOT critical issue.
        HOLE BORDERS SIMPLY WOULD NOT TOUCH SPACERS IN COLD. 

6. Changing from cutting to punching at LPI is not an easy procedure.
                               a)
   Existing templates are not adjusted for punching and should be rebuilt.
   To rebuild templates one should know exact sizes and construction of
   punches. All this costly and time consuming procedure.
                               b)
   Punching should be done against some plastic material (Plexiglas
   or similar).In case of using at LPI semi-dry (and slightly STICKY) 
   glue punching could be the source of serious danger to the quality  
   EST boards. Tiny particles of plastic material arising at punching
         CAN STICK TO THE GLUE AND THEN GO UNDER CLK FOIL.
                      (remark of A.Snesarev)
                               c)
   Possible displacement in punch positions used with LPI tooling can 
   lead to inaccuracy in the size of the holes even larger than during
   cutting procedure.

7. Any discussion of changing technique of the hole manufacturing at LPI
   should carefully account for all mentioned difficulties.