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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Looks like we'll be BGAing in the near future

Views: 3824

#53457

Looks like we'll be BGAing in the near future | 30 January, 2008

We dodged it for a while but it was inevitable.

Here's the question. What do I REALLY need, and does anyone even agree on it? OK, that's *two* questions.

The first board we're likely to do has three parts that will need special consideration. One is a .5mm pitch 80 pin BGA, one is a QFN, and one is either a 256 or 304 pin BGA that may be 1.27 or 1.00 mm pitch.

Currently we have a two stage 10x to 20x scope for inspection. I don't know what the clearances are on the board yet so I don't know if I even have room for a handheld mirror or prism for inspection underneath. Do I need an $18k scope for fine pitch BGA or not? I know I'd like one but that's really immaterial.

I also figure I need a rework station that has vision alignment capability because I know I don't want to be dropping fine pitch BGA on to the pads by eye.

X-Ray? I figure I maybe can drop $$ on either X-ray or video inspection stuff but not both, and I'm leaning towards the latter, mostly just because I like good quality optical inspection, period.

reply »

#53461

Looks like we'll be BGAing in the near future | 30 January, 2008

Steve, Don't worry about it. I can put together a package of X-ray and Optical inspection for less than you think just the X-ray would cost. Give me a call and we can discuss it.

Gary 760-458-0733

reply »

#53464

Looks like we'll be BGAing in the near future | 30 January, 2008

Just my humble opinion. Every place I've worked at uses x-ray over optical inspection for BGAs. Companies that had both often let the optical inspector collect dust becuase you can only really inspect the perimeter solder balls.

Not to mention you can get a hand held BGA mirror and use your x10 x20 magnifier in conjuntion for a perimeter solder ball view. However, becuase it is rather tedious, that isnt something you would want to do on high volume unless you inspected a small random sample of the lot.

Although I am no guru so like i said just my humble opinion.

reply »

#53466

Looks like we'll be BGAing in the near future | 30 January, 2008

Process, process, process. We have been doing BGA's, uBGA's, LCC's etc for over 10 years. We have no X-ray and we don't even have a real rework station. In 2005 we placed just under 100,000 BGA's we reworked less than 100, we scrapped less than 30. We have used places like Ga Tech and other local vendors to "borrow" or rent time on their X-ray for process eval, AKA first article, and then we carefully monitor our process. Good equipment is also is VERY important. Screen printing is crucial, P&P is important and a stable reflow oven a must, nitrogen helps too! My $0.002

reply »

#53477

Looks like we'll be BGAing in the near future | 31 January, 2008

"What do I Really Need" is a subjective question.It all depends on who you ask. I have been in small mom and pop shops that were running BGA's and they were doing some scary stuff.(I wont go into details)

In order to put a correct process together you should potentially have: * The ability to look underneath the periphery of the BGA using a device designed for that purpose. *You also should have some type of access to x-ray equipment. *Access to capable rework equipment. *Capable printing equipment. *Capable placement process *Capable reflow process. There is a specific method that you should use to properly profile a BGA.

Anything less than the above and you are just guessing. IMHO.

reply »

#53487

Looks like we'll be BGAing in the near future | 31 January, 2008

I agree with Sr. and Doug. Capable equipment will run like sh^t if the process is not in control. Number one, don't be scard of BGAs. They are pretty easy if done in control and will cause you less pain than you ever thought. X-Ray is your best inspection method. Just do your homework upfront; be sure your print is spot on and no pads are skipped, verify placement with double sticky tape (moving a BGA in wet paste will cause a mess), and profile-profile-profile.

reply »

#53491

Looks like we'll be BGAing in the near future | 31 January, 2008

All points taken. I appreciate Doug's perspective although I'm not confident enough in our current situation to apply that philosophy whole heartedly. I am well aware that inspection capability and rework tools are supposed to be a last resort, but I am also aware that life jackets are required on boats for a reason. :)

The good news is I think I've got a commitment to spring for a profiler. I was not looking forward to profiling a 3 (min.) BGA board with 3 hardwired thermocouples.

reply »

#53492

Looks like we'll be BGAing in the near future | 31 January, 2008

Profiler is a MUST, along with at least one board you can scrap. Permanently attach TC's and use it to monitor your oven. You really shouldn't use it more than 5 or 6 times before getting a new one but if you can't understand your reading might be off a few degrees as time goes on. If you have marginal faith in your printer, get something to measure your paste too. If you cant do that have someone look at every board at least until you determine print quality to the best of your ability. You'll kill more boards trying to fix defects than it would have cost to go slow and do it right from the beginning.

reply »

#53495

Looks like we'll be BGAing in the near future | 31 January, 2008

You will need to develop your reflow profile which includes drilling a hole through the fab and into the ball for accurate temp measure.

During profile/process development you will probably want 3D x-ray (consider contracting that out). Once in production 2D is fine.

BGA rework station is a must. My machine of choice is Air-Vac. You can buy usaed units reasonably priced, be sure to get a newer model that can be "factory" upgraded to the Air-Vac latest pre-heater system.

Stencil cleanliness is huge. Aperture design is very important. Round holes in stencil can lead to insufficient or no solders unless snap off release is very good. (Think of bubble wands and soapy water - the bubble grows because the hole is perfectly round - odd shapes help avoid "pulling" bubbles of paste)

You are now armed and dangerous

reply »

#53572

Looks like we'll be BGAing in the near future | 6 February, 2008

Something else I forgot to bring up....can we get by using our normal water soluble process or are we going to be able to clean under these things? The BGAs have .18mm and .30mm ball heights.

reply »

#53575

Looks like we'll be BGAing in the near future | 6 February, 2008

We had a customer that had 5 BGA's top and 2 bottom and several other assemblies that had 4-7 total BGA's that required WS. Our average build quantity was 2200 boards a month. We used high end Maytag dishwashers and a little Amterge(SP?) Took them to a friends place on occation and ran them in his cleanliness tester. Never had an issue. I actually prefer the dishwaser for BGA's because the boards are run on their edge and you have a better chace of getting everything out from under the part. (my opinion)and they dont take up 40 feet of floor space either! Only issue was that even with a good dishwasher you'll eat pumps fairly quickly due to the temp and Amterge. By hey whats $350 a year!

reply »

#53576

Looks like we'll be BGAing in the near future | 6 February, 2008

Doug, do you know what the ball heights were on those BGAs? My understanding is that anything over .3mm is a cinch, but going down to .18 is dicey at best unless you have the best of all possible circumstances, which we don't.

reply »


JAX

#53577

Looks like we'll be BGAing in the near future | 6 February, 2008

We have place CSP devices with 0.105mm standoff hights without any issue. The ability to Water Wash all depends on the specifications of your wash...

Spray pressure and qty of jets Dwell time, pre-wash/wash/rinse Available detergents or saponifiers / machine compatible

You should be able to run a "solder sample" with the part in question... cut out the area with the part in question... "ROSE" till your hearts content!

reply »

#53578

Looks like we'll be BGAing in the near future | 6 February, 2008

At one point in time we were putting TI NanoStar parts on these particular boards. You don't want to attempt this at home! Thank God they took them off. Part was 1.45 X 1mm with 6 .1mm balls. They were a pain in the A$$. We had about a 90% success rate. the next larger BGA had a .27mm ball. We had very high yields. So I would say yes you better have good everything for .18mm parts.

reply »

PCB Soldering Tools

Reflow Ovens thermal process improvement