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Circuit Board Cleanliness Testing

CIRCUIT BOARD
CLEANLINESS TESTING


Contamination of circuit boards can bring about severe degradation of insulation resistance and dielectric strength. Cleanliness of completed circuit boards is, therefore, of vital interest.

For those companies who have established circuit board cleaning procedures, the MIL Spec P-28809 has been used as a guideline for control. Now a simple "on line" test for the relative measurement of ionic contamination has been developed.

This fast and economical method for testing circuit board cleanliness uses a Myron L ULTRAMETER™ 4P or 6P, a suitable container and a mixture of Dl (deionized) water and alcohol. Click here for specifications and pricing.

 The procedure is as follows:

1.Mix a stock quantity of solution using 25 parts by volume of Dl water and 75 parts by
volume of 99% isopropyl alcohol. The conductivity, measured with the ULTRAMETER™
4P or 6P should be a maximum of 0.166 micromhos/cm.

2.Measure out an amount of the water/alcohol mixture equal to 100 ml per 10 square
inches of circuit board surface to be tested (considering both sides of the board but not
components) and add 60 ml additional. In other words: 2(L X W) (10ml) + 60 ml = total
solution needed.

3.Fill a poly "zip-lock" bag or other suitable plastic or glass container with the measured
water/alcohol solution.

4.Using the measured water/alcohol solution in the poly bag, rinse out the ULTRAMETER's
cell cup three (3) times, discarding the rinse solution each time. Fill the instrument's cell
cup a fourth time and take a meter reading. This value should be 0.166 micromhos/cm
or less and is the very clean control (or "comparison") reading for the test.

5.Being very careful not to contaminate the PCB, totally immerse the circuit board in the
solution. Seal bag. Allow it to soak for three (3) minutes with mild agitation.

6.At the conclusion of the soaking, pour the solution directly into the instrument's cell cup
four (4) times; take the fourth reading.

7.Compare the control reading in Step 4 with the reading taken in Step 6. The higher the
difference between the two readings, the greater the ionic contamination. Record this
final extract reading for comparison with other boards tested in the same manner.

The level of cleanliness needed or desired can only be determined by each individual
company. Mil Spec P-28809 can be used as a guideline or standards can be established
based upon available data. In either event, the comparative method using the Myron L
ULTRAMETER™ will assist in the determination of that level of cleanliness.
 

Problem Solution Best Myron L models
High water, sewer use and waste treatment costs Myron L CONTROLSTIK™
Rinse Tank System will automatically monitor the quality of rinse water and reduce usage by as much as 80%. 

595 or 597

758II-XXX

Need to quickly verify DI water purity or trouble-shoot reverse osmosis equipment. Portable conductivity instruments are easy to use, yet accurate and reliable enough for field testing of ultra-pure water.  Ultrameter 4P & 6P, EP ( 5 microsiemen range: 1 resistivity range)

532 T2
(3 ranges ppm/TDS)

As DI cylinder are used, quality decreases falling below acceptable limits. This is not always noticed before cylinder can be replaced. A Myron L continuous conductivity, resistivity monitor/controller or Aquaswitch. When DI cylinders approach exhaustion, alarm solenoid valve, etc can be activated.

758II-101
753II-II

Aquaswitch I or II

Conversion Table

Specific Resistance in Ohms Specific Conductance in Micromhos Sodium Chloride Equivalent in Micro Grams/CM² Sodium Chloride Equaivalent in Micro Grams/In² PPM Sodium Chloride
10 megohms 0.10 0.31 2.00 0.021
9 megohms 0.11 0.34 2.22 0.026
8 megohms 0.12 0.39 2.50 0.033
7 megohms 0.14 0.44 2.85 0.041
6 megohms 0.16 0.52 3.33 0.052
5 megohms 0.20 0.6 4.00 0.068
4 megohms 0.25 0.78 5.00 0.091
3 megohms 0.32 1.00 6.45 0.130
2 megohms 0.50* 1.56* 10.06* 0.207*
1 megohms 1.00 3.10 20.00 0.440
775,000 1.29 4.00 25.80 0.575
620,150 1.61 5.00 32.25 0.725
517,000 1.94 6.00 38.71 0.878
443,000 2.26 7.00 45.16 1.027
388,000 2.58 8.00 51.61 1.176
345,000 2.90 9.00 58.06 1.324
310,000 3.22 10.00 64.52 1.476

*Equivalent to 0.01 milligram NaCl/In² (MIL-P- 28809 maximum contamination level)
Note Figures approximated to second decimal place.


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