Subject: Measurement of Dupont XC Kapton Resistive Film with Applied Voltage Gradient, Part Three.

From: Ernie Neuheimer <[email-masked]>
Date: Mon, 15 Sep 2003 13:37:48 -0400 (EDT)

Madhu,
	   The foil resistance of the two types of Dupont Kapton
	carbon-loaded type XC resistive foil which we received
	on about 14 August were measured vs voltage gradient.
	   The two types were described by James Ochsner of Dupont
	USA (281-474-8672 or <[email-masked]> as
	follows:
	
	Sheet #1: 1 x 10E6 Ohms/square at .1V/cm.
		  3 x 10E5 Ohms/square at 1V/cm. 
		  There is no stock of this type at Dupont USA.

	Sheet #2: 2.8 x 10E6 Ohms/square at 1V/cm.
		  There is about 100 sq. meters of this film
		  type at Dupont USA.

	Preparation:

	    Again, 2cm wide strips were accurately sheared
	from the long edge of the 8 1/2" x 11" sheets supplied.
	These were mounted on clean paper surfaces. Copper tape
	contacts (effective area 2cm x 1.2cm) were applied to
	the foil ends so that 24 cm length of foil strip was
	exposed between each contact. The copper tape was the
	conductive through adhesive 3M type 1181. Thus the strips
	were 12 squares in length. Short (~1"), flexible stranded
	24AWG wire was soldered  to each copper contact so as not 
	to stress the copper tape contact when electrical connections
	were made. The area of the contact over the foil was
	'burnished' or rubbed with a rounded metal point to
	improve contact. This method of sample preparation is
	the same as that used in Part 2 of this series of reports.
	
	Measurements:

	  Voltage and current was measured by the technique
	described in the Part 2 report. Results are tabled below:

	Sheet #1, nominal resistance 3 x 10E5 Ohms/square  @1V/cm.

        Applied	   Voltage	 Meas.	      Calc.	  Calc.	  	.
        Voltage	   Gradient	Current	     Resist.      Resist.
       (mV or V)   (mV/cm)	 (nA)      MegOhms/cm   MegOhms/sq.

(HP PS)	 23.51mV         1         9	      0.111	   0.222
	 47.90		 2        19          0.105	   0.210
        119.8            5        49          0.102        0.204
	240.0		10	  99          0.101        0.202
	480.1           20       198          0.101        0.202
	  1.20V         50       497          0.101	   0.202
	  2.401	       100       994	      0.101	   0.202
	  4.800	       200      1988          0.101        0.202
	 12.00	       500      4975	      0.101	   0.202
	 24.00        1000      9949	      0.101        0.202
(HR PS)  48.00        2000     19890          0.101        0.202
	120.0	      5000     49800          0.100	   0.200
	240.0        10000     99910	      0.100	   0.200
	480.0        20000    201300	      0.099        0.198
        1200	     50000    516000	      0.097	   0.194
	2400	    100000   1068600          0.094	   0.188
	------------------------------------------------------------

	Sheet #2, nominal resistance 2.8 x 10E6 Ohms/square @1v/cm.

	Applied	    Voltage	 Meas.	      Calc.	  Calc.
	Voltage     Gradient	Current	      Resist.    Resist.
	(mV or V)   (mV/cm)	 (nA)      (MegOhm/cm) (MegOhm/sq.)
	
(HP PS)   --	       -	  --	       ---	   ---
	  47.75mV      2	   2.	      1.0	   2.0
	  120.3        5	   6.          .833	   1.66
	  240.9       10          12	       .833        1.66
	  480.0       20          25           .800        1.60
	    1.199V    50          63	       .794        1.59
	    2.400    100	 128	       .781	   1.56
	    4.801    200         256           .781        1.56
	   11.999    500         643           .778        1.56
	   24.00    1000	1289	       .776	   1.55
(HR PS)	   48.10    2000	2596	       .770	   1.54
	  120.0     5000        6576	       .760	   1.52
	  240.0	   10000       13470	       .742	   1.48
	  479.9    20000       28140	       .710        1.42
         1200.     50000       77910	       .642	   1.28
	 2400.	  100000      177000	       .565	   1.13 	    	
	------------------------------------------------------------

	Conclusions:
	
	   Both sample strips measure about 50% lower in resistance
	per square at the same voltage gradient of 1V/cm from the
	nominal value quoted by Dupont. The type of film in stock
	at Dupont measures about 1.66 MOhm per square for low
	gradients (a few mV/cm) encountered in the experimental
	situation.

	   If this resistance is thought satisfactory, I will
	ask James Ochsner for more (we have only a single 7.7" x
	11" sheet left). If the lower resistance film is desired,
	a search will be made to see if any Dupont distributor 
	has the lower resistive film in stock.

	   Low gradient measurements will be made with the new
	four-point probe of the same films for comparison of the
	two techniques.
			    Ernie.