Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Chiakl

#15566

Ionic chromotography test on PCBA | 4 June, 1998

I have just been assigned to look into the ionic chromotograhy test on our PCBA but I have zero knowledge. Could anyone help to explain what is this test about? Is it a) a destructive test? b) What is the measurement unit of this test? c) What is the standard? chiakl

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Earl Moon

#15570

Re: Ionic chromotography test on PCBA | 5 June, 1998

| I have just been assigned to look into the ionic chromotograhy test on our PCBA but I have zero knowledge. Could anyone help to explain what is this test about? Is it | a) a destructive test? | b) What is the measurement unit of this test? | c) What is the standard? | chiakl | As I recall, Ion chromatography is used to measure the total current carried in a solution by the ions present. This is similar to solvent resistivity extract testing wherein a contaminate sample, in solution (75% isopropyl alcohol and 25% dionized water) is derived from a specimen's surface (PCB or PCBA) by pouring the solution over the specimen's surface and collecting it in a container. The solution is then measured, via electrical current, against a specified requirement. For electronic equipment (again as PCB's and PCBA's) the specified limit is usually 2 megohms/cm. This type testing may fill your needs better and more cheaply than ion chromatography. It also is readily available. To achieve similar results, concerning possible electrical conductivity (shorting) on the surface of PCB's or PCBA's between conductors, may be done using surface insulation resistance (SIR) wherein solid residues, as conductive salts retained after processing, are determined by quantitative analysis. The allowable quantity of conductive material is specified in documents such as MIL-P-28809 (and it's IPC crossover documentation), IPC-TM-650, and the ANSI/IPC-STDS derived from MIL or Dod-STD-2000. Happy board cleaning and cleanliness, Earl Moon

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Dave F

#15569

Re: Ionic chromotography test on PCBA/My Sympathies | 5 June, 1998

| I have just been assigned to look into the ionic chromotograhy test on our PCBA but I have zero knowledge. Could anyone help to explain what is this test about? Is it | a) a destructive test? | b) What is the measurement unit of this test? | c) What is the standard? | chiakl | Chiakl: My sympathies. Dave F

Ionic chromotography is a J-STD-001B type requirement for level 3 process control, which (paraphrased) goes something like this: The first step should be a benchmarking of the residues present on your bare boards, using a rigorous chemical analytical technique. Standard Omegameter testing would not fit in this category. For bare board analysis, ion chromatography (TM-650, method 2.3.28) is recommended. Ion chromatography allows us to identify not only what ionic species are present, but also the amounts. Different assemblies will have different sensitivities to various ionic species, but with a sufficient experience base, a skilled analyst can usually give a good indication of whether the fabrication residues will cause problems in SIR testing. The substrate used for the analysis should be actual bare boards that approximates your most difficult or demanding situation. Try IPC Technet for more ...

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Graham Naisbitt

#15567

Re: Ionic chromotography test on PCBA | 7 June, 1998

Chiakl Ion Chromatography has been perfectly described by Dave, but here are a couple of extra considerations: Ion Chromatography will tell you precisely what is present on the surface of your board/assembly but it will not tell you whether it will be reliable. SIR testing will tell you if your assembly will be reliable but not what is present on the surface. Chicken and Egg? Yes! SIR first and IC after if you have a problem with the reliability (SIR) testing. Refer to IPC-TM-650 2.6.3.3. and IPC 9201 plus the Process Characterisation test from J-STD-001 There are labs that will do both testing methods for you such as Robisan and CSL or you may be able to rent the system - at least SIR testing you can. Hope this helps and if you want more, let me know. Regards, Graham Naisbitt | I have just been assigned to look into the ionic chromotograhy test on our PCBA but I have zero knowledge. Could anyone help to explain what is this test about? Is it | a) a destructive test? | b) What is the measurement unit of this test? | c) What is the standard? | chiakl |

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Dave F

#15568

Re: Ionic chromotography test on PCBA | 8 June, 1998

| Chiakl | Ion Chromatography has been perfectly described by Dave, but here are a couple of extra considerations: | Ion Chromatography will tell you precisely what is present on the surface of your board/assembly but it will not tell you whether it will be reliable. | SIR testing will tell you if your assembly will be reliable but not what is present on the surface. | Chicken and Egg? Yes! SIR first and IC after if you have a problem with the reliability (SIR) testing. | Refer to IPC-TM-650 2.6.3.3. and IPC 9201 plus the Process Characterisation test from J-STD-001 | There are labs that will do both testing methods for you such as Robisan and CSL or you may be able to rent the system - at least SIR testing you can. | Hope this helps and if you want more, let me know. | Regards, Graham Naisbitt | | I have just been assigned to look into the ionic chromotograhy test on our PCBA but I have zero knowledge. Could anyone help to explain what is this test about? Is it | | a) a destructive test? | | b) What is the measurement unit of this test? | | c) What is the standard? | | chiakl | | Much of what I wrote was first "penned" by Douglas Pauls. Dave F

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