Approach To Contamination Testing Of PCBs

We understand that testing for ionic contamination and surface insulation resistance measure different properties. We assemble printed circuit boards for other companies. We will not get combs on 90% of the boards that we assemble. We have no customer complaints about board cleanliness. We want to begin a cleanliness process control approach focused on monitoring the cleanliness of boards: 1 Provided by fabricators. 2 At post aqueous washing in our processing I think we should be testing ionic contamination. What are your thoughts? Dave

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Dave, Ionic contamination testers are considered to be a valuable tool to determine the cleanliness of both bare boards and post solder boards. There are some instances when SIR testing is more suitable for determining cleanliness than ionic contamination testers. Due to the speed, ease of use, and low cost of ionic contamination testers, many manufacturers choose to perform SIR tests sparingly (if at all) and only to validate the results of an ionic contamination tester. There are basically two technologies available in ionic contamination testers, dynamic and static. The EMPF study entitled "An in Depth Look at Ionic Contamination Testing" (RR0013) seems to indicate a preference towards dynamic-based systems. Ionic Contamination Tester Brands Include: Zero-Ion (Manufactured by Aqueous Technologies) Ionograph (Manufactured by Alpha Metals) Omegameter (Manufactured by Alpha Metals) Icom 5000 (Manufactured by Westek) If you need specific information on ionic contamination testers (too commercial in this public forum), please contact Mike Konrad (Aqueous Technologies) at (800) 218-8128.

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| We understand that testing for ionic contamination and surface insulation resistance measure different properties. We assemble printed circuit boards for other companies. We will not get combs on 90% of the boards that we assemble. | We have no customer complaints about board cleanliness. We want to begin a cleanliness process control approach focused on monitoring the cleanliness of boards: | 1 Provided by fabricators. | 2 At post aqueous washing in our processing | I think we should be testing ionic contamination. What are your thoughts? | Dave Dave, Yes. Do the ionic contamination testing. How do you know if your oven is functioning properly. Testing your suppliers raw fabs is pretty labor intensive for not much information. I wouldn't recommend it. If you start seeing solderability problems, check it out. If you are qualifying a new board vendor, check it out. As part of a routine process control, no. That's like testing paste viscosity. It's only needed when there is a problem. That's just my opinion. The tighter you run the ship, the better it runs, the more it costs. Find the find the relationship between cost of prevention and costs incurred by actual defects from this source. That's where your answer will lie. Regards, Justin

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| | We understand that testing for ionic contamination and surface insulation resistance measure different properties. We assemble printed circuit boards for other companies. We will not get combs on 90% of the boards that we assemble. | | We have no customer complaints about board cleanliness. We want to begin a cleanliness process control approach focused on monitoring the cleanliness of boards: | | 1 Provided by fabricators. | | 2 At post aqueous washing in our processing | | I think we should be testing ionic contamination. What are your thoughts? | | Dave | Dave, | Yes. Do the ionic contamination testing. How do you know if your oven is functioning properly. Testing your suppliers raw fabs is pretty labor intensive for not much information. I wouldn't recommend it. If you start seeing solderability problems, check it out. If you are qualifying a new board vendor, check it out. As part of a routine process control, no. That's like testing paste viscosity. It's only needed when there is a problem. That's just my opinion. The tighter you run the ship, the better it runs, the more it costs. Find the find the relationship between cost of prevention and costs incurred by actual defects from this source. That's where your answer will lie. | Regards, | Justin Dave, forget what I just wrote. I just reread it and confused myself. it's been a long week!! Use the ionic contamination test to verify that your cleaner is working properly. I don't think it should be used on every lot of boards. That would just consume too many resources for redundant information. Use it to qualify new vendors and to trouble shoot if need be but primarily as a control for your cleaner. sorry about the confusion, justin

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| | | We understand that testing for ionic contamination and surface insulation resistance measure different properties. We assemble printed circuit boards for other companies. We will not get combs on 90% of the boards that we assemble. | | | We have no customer complaints about board cleanliness. We want to begin a cleanliness process control approach focused on monitoring the cleanliness of boards: | | | 1 Provided by fabricators. | | | 2 At post aqueous washing in our processing | | | I think we should be testing ionic contamination. What are your thoughts? | | | Dave | | Dave, | | Yes. Do the ionic contamination testing. How do you know if your oven is functioning properly. Testing your suppliers raw fabs is pretty labor intensive for not much information. I wouldn't recommend it. If you start seeing solderability problems, check it out. If you are qualifying a new board vendor, check it out. As part of a routine process control, no. That's like testing paste viscosity. It's only needed when there is a problem. That's just my opinion. The tighter you run the ship, the better it runs, the more it costs. Find the find the relationship between cost of prevention and costs incurred by actual defects from this source. That's where your answer will lie. | | Regards, | | Justin | Dave, | forget what I just wrote. I just reread it and confused myself. it's been a long week!! Use the ionic contamination test to verify that your cleaner is working properly. I don't think it should be used on every lot of boards. That would just consume too many resources for redundant information. Use it to qualify new vendors and to trouble shoot if need be but primarily as a control for your cleaner. | sorry about the confusion, | justin Dave and Justin, Just a few additional thoughts and methods. First, if you want clean fabs, include specifications as part of your contract for qualified board suppliers to meet the old MIL-P-28809, IPC-TM-650, or? then audit cleanliness on a sample level basis at the specified requirement (2 megohms/cm, as an example). Second, ensure your internal DI water capability is operating as specified, meter instead of light preferred at about 4 megohms/cm. This ensures your assemblies are ionic contamination free in accordance with specified requirements. Then, do sample level testing with an Omega meter or other analytical devices indicated previously. Sincerely Earl

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Gentlemen, Please consider that ionic testing is designed only for detecting ionic contaminants. Yes there are instances of non-ionic contaminants that cause premature circuit failure. However, more importantly the prevailing specs are less than adequate primarily because they (eg ANSI-J-STD-001A and B, MIL-P-28809, MIL-STD 2000 etc..) state that you should clean to LESS THAN 10.07 microgrammes per square inch. This also means that it is perfectly OK to leave UP TO 10 microgrammes of salt on every square inch of your assembly. Fine line, fine pitch, BGA, COB etc.? The this level will almost certainly be too high. That is why many now apply an empirical value at less than 2 microgrammes. Also, this is why SIR testing is becoming far more relevant for process validation. Check out your process at each manufacturing stage and you can easily determine where bad synergy exists between different process materials. If you want more, let me know Regards, Graham Naisbitt | We understand that testing for ionic contamination and surface insulation resistance measure different properties. We assemble printed circuit boards for other companies. We will not get combs on 90% of the boards that we assemble. | We have no customer complaints about board cleanliness. We want to begin a cleanliness process control approach focused on monitoring the cleanliness of boards: | 1 Provided by fabricators. | 2 At post aqueous washing in our processing | I think we should be testing ionic contamination. What are your thoughts? | Dave

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| | | | We understand that testing for ionic contamination and surface insulation resistance measure different properties. We assemble printed circuit boards for other companies. We will not get combs on 90% of the boards that we assemble. | | | | We have no customer complaints about board cleanliness. We want to begin a cleanliness process control approach focused on monitoring the cleanliness of boards: | | | | 1 Provided by fabricators. | | | | 2 At post aqueous washing in our processing | | | | I think we should be testing ionic contamination. What are your thoughts? | | | | Dave | | | Dave, | | | Yes. Do the ionic contamination testing. How do you know if your oven is functioning properly. Testing your suppliers raw fabs is pretty labor intensive for not much information. I wouldn't recommend it. If you start seeing solderability problems, check it out. If you are qualifying a new board vendor, check it out. As part of a routine process control, no. That's like testing paste viscosity. It's only needed when there is a problem. That's just my opinion. The tighter you run the ship, the better it runs, the more it costs. Find the find the relationship between cost of prevention and costs incurred by actual defects from this source. That's where your answer will lie. | | | Regards, | | | Justin | | Dave, | | forget what I just wrote. I just reread it and confused myself. it's been a long week!! Use the ionic contamination test to verify that your cleaner is working properly. I don't think it should be used on every lot of boards. That would just consume too many resources for redundant information. Use it to qualify new vendors and to trouble shoot if need be but primarily as a control for your cleaner. | | sorry about the confusion, | | justin | Dave and Justin, | Just a few additional thoughts and methods. First, if you want clean fabs, include specifications | as part of your contract for qualified board suppliers to meet the old MIL-P-28809, IPC-TM-650, or? then | audit cleanliness on a sample level basis at the specified requirement (2 megohms/cm, as an example). | Second, ensure your internal DI water capability is operating as specified, meter instead of light preferred | at about 4 megohms/cm. This ensures your assemblies are ionic contamination free in accordance with specified | requirements. Then, do sample level testing with an Omega meter or other analytical devices indicated previously. | Sincerely | Earl

Earl: What do you mean by: "meter instead of light preferred?" Dave F

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| | | | | We understand that testing for ionic contamination and surface insulation resistance measure different properties. We assemble printed circuit boards for other companies. We will not get combs on 90% of the boards that we assemble. | | | | | We have no customer complaints about board cleanliness. We want to begin a cleanliness process control approach focused on monitoring the cleanliness of boards: | | | | | 1 Provided by fabricators. | | | | | 2 At post aqueous washing in our processing | | | | | I think we should be testing ionic contamination. What are your thoughts? | | | | | Dave | | | | Dave, | | | | Yes. Do the ionic contamination testing. How do you know if your oven is functioning properly. Testing your suppliers raw fabs is pretty labor intensive for not much information. I wouldn't recommend it. If you start seeing solderability problems, check it out. If you are qualifying a new board vendor, check it out. As part of a routine process control, no. That's like testing paste viscosity. It's only needed when there is a problem. That's just my opinion. The tighter you run the ship, the better it runs, the more it costs. Find the find the relationship between cost of prevention and costs incurred by actual defects from this source. That's where your answer will lie. | | | | Regards, | | | | Justin | | | Dave, | | | forget what I just wrote. I just reread it and confused myself. it's been a long week!! Use the ionic contamination test to verify that your cleaner is working properly. I don't think it should be used on every lot of boards. That would just consume too many resources for redundant information. Use it to qualify new vendors and to trouble shoot if need be but primarily as a control for your cleaner. | | | sorry about the confusion, | | | justin | | Dave and Justin, | | Just a few additional thoughts and methods. First, if you want clean fabs, include specifications | | as part of your contract for qualified board suppliers to meet the old MIL-P-28809, IPC-TM-650, or? then | | audit cleanliness on a sample level basis at the specified requirement (2 megohms/cm, as an example). | | Second, ensure your internal DI water capability is operating as specified, meter instead of light preferred | | at about 4 megohms/cm. This ensures your assemblies are ionic contamination free in accordance with specified | | requirements. Then, do sample level testing with an Omega meter or other analytical devices indicated previously. | | Sincerely | | Earl | | Earl: What do you mean by: "meter instead of light preferred?" Dave F Dave, As you know, many DI water systems are installed with a low level light indicating when the water goes below 2 megohms, or whatever. I simply meant I prefer a calibrated meter indicating exactly where the level is with respect to what is acceptable and specified. This allows ionic "tracking" over time - or the tool and method needed to ensure process variability and control. Earl

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