Improve determination of residual anions and organic acids for printed circuit board cleanliness

[GaryHe]

If you’re using ion chromatography to determine specific anionic contamination on the surface of printed circuit boards (PCBs), you want high resolution to ensure cleanliness.

Thermo Fisher Scientific teams recently demonstrated two techniques to improve resolution per the IPC-TM-650 Method. The team used a 2 mm i.d. Thermo Scientific™ Dionex™ IonPac™ AS11-HC column with 9 μm resin in two different techniques to modify the column selectivity to improve resolution.

Here’s a snapshot of the methods:

Method A

Columns	Dionex IonPac AG11-HC guard, Dionex IonPac AG11-HC analytical, 2mm i.d.
KOH gradient, eluent pump	1 mM KOH (-5 to 9 min), 1-14 mM (9 to 16 min), 14 mM (16 to 23 min), 14-85 mM (23 to 30 min), 85 mM (30 to 32 min), 1 mM (32 min)
Eluent source	Dionex EGC-500 KOH eluent generator cartridge, Dionex CR-ATC 600 trap column, Dionex high pressure degasser module
Methanol gradient	None
Injection volume	5 μL
Flow rate	0.38 mL/min
Column temp.	20 ˚C
Detection temp.	20 ˚C
Detection	Suppressed conductivity, ADRS 600 suppressor, external water mode by pump 2 @ 0.38 mL/min, 57 mA
Conductance background	<0.5 μS/cm
System backpressure	~2,600 psi (100 psi = 689.5 kPa) with 800 psi backpressure tubing
Run time	38 min

Method B

Columns	Dionex IonPac AG11-HC guard, Dionex IonPac AG11-HC analytical, 2mm i.d.
Proportioning pump 1	A: DI water for eluent generation B: Methanol for methanol gradient
KOH gradient, pump 1	1 mM KOH (-5 to 17 min), 1-15 mM (17 to 24 min), 15 mM (24 to 35.3 min), 15-60 mM (35.3 to 54.6 min), 1 mM (54.61 -55 min)
Eluent source	Dionex EGC-500 KOH eluent generator cartridge, Dionex CR-ATC 600 trap column, Dionex high pressure degasser module
Methanol gradient, pump 1	2% (-5 to 24 min), 2-10% (24 to 29 min), 10-15% (29-51 min), 15-2% (51 to 54.6 min), 2% (54.6 to 55 min)
Injection volume	5 μL
Flow rate	0.38 mL/min
Column temp.	30 ˚C
Detection temp.	20 ˚C
Detection	Suppressed conductivity, ADRS 600 suppressor, external water mode (DI) by pump 2 @ 0.38 mL/min, 57 mA
Conductance background	~0.5 μS/cm
System backpressure	2,400-3,000 psi
Run time	60 min

These two methods are alternatives to the method presented in Application Note 1163: Determination of anions on the surface of printed circuit boards by IPC-TM-650 Method 2.3.28 using HPIC.  Compared to that method, both methods had reduced system pressure but some loss of resolution. The resolution of these two methods may be sufficient for the analytical goals of the PCB industry laboratory.

Learn more: To see the full method details and review the list of equipment, reagents, software and consumables, read this application brief.