Welcome to Board Talk. We are the Assembly Brothers, Phil Zarrow and Jim Hall of ITM Consulting, and we're here to answer your questions on SMT processes, equipment, materials, procedures, and anything else you have on your mind. What have we got today, Jim?
We've got a question about printed circuit board handling from Bob W. in San Diego, California.
At present, our operators and technicians do not wear gloves when handling PCBA's. Now I heard that this is not a good practice and we will get in trouble. How do you guys weigh in on this issue?
Weigh in on this issue? Where's my soapbox? Bring out the soapbox. Here we go. Weigh the issue? Oh, man. Okay, calm down. Okay, here we go.
We consider best practices, in other words something that should be employed world class, that anyone coming in contact with a board assembly, prior to final soldering, should be wearing gloves or finger cots, period, no exceptions.
That means even the quality assurance supervisor who comes over to look at a board, don't just pick it up off the rework table. Put on gloves or finger cots.
The reason for this is because your fingers have oil and dirt, what we commonly call contaminates, and these can be transferred to the board and the result will be poor wetting, weaker solder joints, voids, and a host of other fun things.
Remember they're contaminates, and fluxes in your wave soldering machines do not reliably remove contaminants. If you get contaminants on those soldering surfaces, you're asking for possible problems.
You would think this would be common sense, yet per our audits the manufacturers who are actually doing this are in the minority. Most manufacturers really can't seem to be bothered. I don't know if it's bother or what else do you think, cheapo?
Cheapo and they're not tracking their defects. The same thing we talk about all the time. That was no joke about a quality control manager coming over after the first side of double-sided reflow and picking up a board to inspect it to show us something with her fingers touching the bottom side of the board which was then going to be flipped over and stencil printed and reflowed.
We see this kind of nonsense in CEM's and OEM's, alike, but probably one of the most important pieces of industry lore comes from our good buddy, Terry Munson at Foresight.
In a previous life, when we got to know Terry way back in the days of yore, he had established himself as the contamination and cleanliness expert at a very large, metropolitan automotive electronics company.
Terry conducted a very interesting test when he was at this company. What he did was he made various cleanliness and contamination tests on circuit boards built on a line and he conducted a run of tests on the boards produced on the morning shift.
Then, using the same line, same boards, same materials, same product, and same operators, he basically tested the same cleanliness examination test on boards built after lunch.
This is something that came to be called the Lunch Hour Effect because what Terry observed was that the levels of contamination on boards built after lunch went up by several magnitudes and again, for the obvious reasons.
People don't always practice best hygiene. Probably this is the same reason you shouldn't eat peanuts in a bar, but in this case, it's something that gets transferred to your boards.
The number of people that are actually using gloves and finger cots are far and in between. This is a practice everybody should be doing and people feel, "Well, I'm getting adequate results."
But again, the question is, are you getting zero defects? We believe that over time, as Jim mentioned, if you're actually tracking your defects and you employ this practice, you will see an improvement. I can guarantee it and, of course, Terry's data backs that up, too.
Now, of course, if you are wearing gloves and finger cots, wear them properly.
We've seen some seemingly unbelievable things, particularly in rework areas, where people wearing their gloves have cut out the fingers where their fingers touch the board in order to get better feel and control over handling the boards, defeating the exact purpose that they're wearing gloves for in the first place.
This doesn't speak much to the training integrity of that kind of facility because people are wearing gloves but they obviously have no perception of why they're wearing them.
Which underscores another important facet that you should not only tell people what to do, you should tell them why they're doing it. Knowledge is wonderful and knowledge is power.