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BGA & QFP post reflow inspection

Dr . Klein


BGA & QFP post reflow inspection | 4 May, 2005

Hello all. I need some advice for first article inspection process. I will explain my problem with this process: In our site we are doing a manually FAI before reflow for every assembly. One of the steps is to check the writing on each QFP or BGA (every component that come in trays) against the writing in the BOM of the same assembly. This step is necessary for our production from the rezone that we are not open the tray bags until the assembly beginning, (moister problems). Sometimes, we had a situation that a tray came from the supplier with different component that it supposed to come with. Another problem, we can get the same component from different supplier (with different writing on the component) , we just have to check it against the BOM , and we doing this check just after the SMT assembly.

Our products are very complex and with a lot of BGA & QFP, this process takes 15 min per assembly, it will be great to take this process offline!

If you know a process for checking the component in the tray before the assembly (offline), with taking the concern of moister problem, please explain me the process. It will be very helpful. Thanks.

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BGA & QFP post reflow inspection | 4 May, 2005

What is the MS-level and floor life of the critical components (should be written on the MSD-bag)? What is Your climate condition in the production area (%RH, temp.)? Are you doing this inspection on every board or is it enough to do it on the first board and then only on the board assemblied after each feeder refill? How about to open the sealed MSD bag, just before the feeder runs out of components and then read the component text prior to load the feeder?

It all depends on the remaining floor life of the components and Your room climate condition. Check the IPC/JEDEC J-STD-033A and IPC/JEDEC J-STD-020C I Hope I did not overlooked anything.

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Dr. Klein


BGA & QFP post reflow inspection | 4 May, 2005

Thanks siverts,

The problem with open the sealed MSD bags before the production, is from the rezone that we don�t know exactly when the production start. If we will open the bags before production there is a possibility that the component will be outside for too long.

About the climate, we are working with the universal smt standards.

Maybe there is a box that saves the components after I open the bags...

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BGA & QFP post reflow inspection | 4 May, 2005

I worked at a place where they homemade a parts humidoor. What they did was take some plexiglass get it cut to the measurments they needed. Than they assembled it and added air control to it to keep the humidity set. Damn if I can remember exactly what they did but it seemed to help them alot.

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BGA & QFP post reflow inspection | 4 May, 2005

Hey Dr . Klein, I think You do it all right... But here it comes: MSD; what does it really means? MS-level; what does it really means? Floor life what does it really means? I'm sorry but I can't answer all these questions right now. It is a complex matter...

First of all: Floor life; the clock starts ticking when you first open the sealed MBB (Moisture Barrier Bag), which is your ESD (Electrical Sensitive Discharge) proven MBB that holds your MSD:s (Moisture Sensitive Devices)

Second: You should/must/will keep track of the open time that the components have been exposured to the open environment. Let say that you have a component with a MS-level = 3. That means according to IPC-033A and also to the label you will be able to find on the MBB, that the floor life is 168 h. Now, here comes the tricky part; how to determine if the MSD-component has been exposured to the outside (MBB) environment to long?

Third: You must find a way for your people that handles the MSD-components; either to use some kind of a marking stick/label/barcode label to follow each MSD-component that have been opened in the production area. On this label you must also fill in the opened time and if you decide to put some of the components back, write the closing time. Every time from now on, the operator must fill in the open time and the closing time. If the the total exposure time ecceeds the time written on the label, in this case 168hours, Then You must bake the componet. Don't forget to put in a fresh deccicator (Dry Bag) and a new HIC (Humiditor Indicator Card) before you reseal the MBB. By the way, don't seal the MBB with "high" vacuum; the MBB will transfer moisture through the bag over time and the deccicator will not be fully effective. (Sorry for my poor english).

I hope this will clearify some things...

The answer to your original question; I can't see any problems for your production, unless you are dealing with extremly high MS-level components; like 5, 5a or 6.

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BGA & QFP post reflow inspection | 4 May, 2005

Can you not just check the part when it is on line and being loaded into the machine? You should only need to check this once. Verify your setup to the bom and not your assembled boards to the BOM. Correct setup and program = correct boards.

More importantly I would go after the root cause of this problem. Your receiving inspection needs to catch these wrong parts prior to them being put into stock. Your purchasing people need to beat up these suppliers that put the wrong part into the package. Inspecting every part before the oven for value is definitely a poor utilization of resource.

If the bag needs to be opened before production just reseal it with the desicant bag and the humidity indicator that it came with. When you re-open the bag check the indicator card to verify the level of humidity exposure and take actions as necessary.

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BGA & QFP post reflow inspection | 7 May, 2005

If you do 100% incomming inspection the operator will not have to worry about the part being right or wrong. we do 100% at our facility and create a custom barcode label for lot code and date code traceability. that way we know if the part does not have that label it has not gone through IQC.

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Dr . Klein


BGA & QFP post reflow inspection | 8 May, 2005

Hello mrmaint You say that you do 100% incoming inspection at your site, Do you open every tray and look on the writing on every type of component? If you open the bag, how do you close it again (vacuum machine)? What is the inspection process? (Only for component that come in trays) How do you keep the temperature and humidity level of the components?


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BGA & QFP post reflow inspection | 9 May, 2005

We use a "McDry" cabinet for humidity control of opened, moisture sensitive parts. Relatively cheap and works good. This cabinet is installed right on the SMT line. Check out:

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BGA & QFP post reflow inspection | 9 May, 2005

If followed, would the following strategy meet the requirements of IPC/JEDEC J-STD-033A; All MSD components are either exposed for less than 1/2 an hour or final reflowed within 12 hours of opening.

What I mean by exposed is any time the parts are not in a properly sealed MBB with desicant or a dry cabinent at 5% or less RH.

If the MBB is open less than an hour you can still use the same desicant if the indicator card is still good. I think with a vaccuum sealer, sealed active desicants, sealed RH cards, and suffecient dry cabinents this is achievable.

Well at small run places anyways, where the run of bottom sides can be put in the dry cabinent.

If I understand J-STD-033A properly, then this even covers class 5 components with high ambient temp and RH. If you only have class 3 then you can change the 12 hours to 168. And the 1/2 hour can be one hour but I think 1/2 an hour is enough to open the bag check the parts and reseal it or put it in a dry cabinent. And if you say 1/2 an hour, they might take 45 mins and still be ok, but if you say 1 hour they might take longer.

If the exposure is less than an hour the clock goes backwards if put in a properly sealed MBB or a dry cabinent less than 5% RH.

If anyones bogusity detector goes off, please jump all over me and point out in detail the errors of my ways.

And I realize my strategy doesn't cover class 6 components but I dont' think any strategy other than a case by case one will.

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Dr . Klein


BGA & QFP post reflow inspection | 10 May, 2005

Hello (pwh) I would like to know more about your process. What is the rezone you open the bags? Do you put any stamp on the opened trays before you enter them to the mcdry? What kind of inspection do you make before you enter the trays to the mcdry? Any other information about your process will be absolutely great. Thanks.

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