IEC 61189-5-501 pdf – Test methods for electrical materials, printed boards and other interconnection structures and assemblies – Part 5-501: General test methods for materials and assemblies – Surface insulation resistance (SIR) testing of solder fluxes
6 Coupon preparation6.1General
There shall be not less than three test coupons for each liquid flux or solder paste to be tested.Patterns A through F shall be prepared and tested on each coupon.
6.2coupon cleaning
Place the test coupons in an ionic contamination tester containing 50 % propan-2-ol，50 %deionized water and process the solution until a resistivitymeasure of >20 M Q has beenachieved.A mixture of 25 % propan-2-ol,75 % deionised water may alternatively be used. See
EC 61189-5-504 for additional information on ionic contamination testing.
Alternatively, clean each of the test coupons with deionized or distilled water and scrub with asoft bristle brush for a minimum of 30 seconds.Spray-rinse thoroughly with deionized or distilledwater. Rinse cleaned area thoroughly with fresh propan-2-ol.
During the remainder of the coupon preparation, handle test coupons by the edges only, or uselint-free, non-contaminating gloves.
Dry the cleaned coupons for 2 h at 50 °C.
lf the coupons are to be stored before treatment, place them into contamination-free containersor a desiccator.
When measured as described in Clauses 4 and 5, if the control coupon readings are less than1 000 MQ at any point after the initial 24 h of SIR exposure, a new set of test coupons shall beobtained and the entire test repeated.
6.3ldentification
Positive，permanentand non-contaminating
identification of test coupons is of paramount
importance for example, a vibrating scribe.
6.4lnspection
Visually inspect the test coupons for any obvious defects. Ilf there is any doubt about the overallquality of any test coupon, the test coupon shall be discarded.
6.5Storage
lf boards are to be stored before treatment,place the boards in contamination-free bags orcontainers with a desiccant.
6.6 No clean fluxes When testing liquid fluxes that are intended to remain in the un-cleaned state, a minimum of six test coupons are required. Three uncleaned test coupons shall be wave soldered pattern side down (see Table 1, Sample group B) and three shall be wave soldered pattern side up (see Table 1, Sample group C).
After exposure to flux and solder, coupons to be tested in an un-cleaned state shall be evaluatedas described in Clauses 8 and 9.
6.7Cleanable type fluxes
After exposure to flux and solder，coupons to be tested in the cleaned state shall be cleanedusing one of the procedures listed below. The cleaning parameters shall be reported in thequalification test report.
The coupons to be cleaned shall be cleaned with an appropriate environmentally safe solventor aqueous cleaning medium.The use of a commercial batch or in-line cleaner is preferred.
lf this is not available,the following laboratory cleaning process shall be followed: Threecoupons shall be cleaned within a maximum of 30 minutes after soldering.
For solvent or aqueous detergent cleaning, three 2 000 ml beakers each containing 1 000 ml of
solvent shall be used so that one beaker serves as the primary cleaning stage and the othertwo are used for rinsing purposes.Each test coupon shall be agitated in each beaker for 1 min.
In the case of aqueous detergent, one beaker shall contain the cleaning agent and the remainingbeakers shall contain deionised water for rinsing purposes.
After the cleaning procedure is complete, coupons are dried for 2 h at 50 °℃.Following cleaning,the coupons shall be tested as outlined in Clauses 8 and 9.
6.8Solder paste coupons
6.8.1 Coupon preparation
Stencil print the solder paste on to the preferred comb patterns using a 0,150 mm thick stencil.
The stencil shall consist of a series of circular holes of a diameter of 0,4 mm for patterns A,B,
Eand F, and 0,3 mm for patterns C and D, or square openings that match the conductors ofthe comb pattern.The registration of the stencil shall be such that the solder paste is deposited
directly on the conductors and does not cause bridging between conductive patterns. Thereshall be a minimum of six openings for each conductor in the comb pattern.
The coupons shall be run through a reflow soldering process using the temperature profilerecommended by the solder paste supplier.
These shall be reflowed pattern side up and either cleaned (Table 1, Sample group D) or notcleaned(Table 1, Sample group E). In addition, there shall be at least two unprocessed controlcoupons for comparison purposes (Table 1,Sample group F).