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Unusual board with BGA

Views: 3626

#52857

Unusual board with BGA | 11 December, 2007

We just got a contract to build a board with 1400+ SMT placements. This thing is 16" x 12" and the PCB thickness is 0.142". Dead center is a 580+ pin BGA that costs about $600. I'm a bit intimidated... I've done lots of mole profiling on BGA's but this board size and thickness is a new ball game for me. Anyone ever dealt with something similar to this that could offer some preliminary advice or problems you encountered???

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#52866

Unusual board with BGA | 12 December, 2007

Yes, you can ask for scrap boards, buy Dummy boards/parts or engineer off past runs. For this cost, I would profile, profile, profile. I would make/buy a dummy board. If you don't have one this thick, glue/ adhesive/ bolt some scrap boards together to make a thickness similar. Use a band saw to cut to size. Buy dummy BGA parts and glue to the middle of your board. You don't need copper pads - just make sure there is a hole in the middle of the board so you can measure the t-couple you put up in there. Now you're all set. It's not rocket science but it will take about 90% of your doubts away.

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#52867

Unusual board with BGA | 12 December, 2007

call meeting about this

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#52873

Unusual board with BGA | 13 December, 2007

Yes, calling meetings seems to be the way to tackle tuff problems without ever doing anything about them. Make spread sheets and "talk" a good talk so everyone thinks you are on top of your game. Yet you do absolutely mothing and wonder why the problem never goes away. We have a lot of people like this at my place of employment. They actually think holding meetings makes the problem go away! Then they amazed when it's still on their problem log 8 months later! LOL.....

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#52879

Unusual board with BGA | 13 December, 2007

What a preposterous notion. I question your desire to retain your current employment status. This clearly mandates a meeting! Harrrumph!

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#52882

Unusual board with BGA | 13 December, 2007

You're right. I do care too much. I should work on that. I guess it is better to just point out a problem ina meeting and waste resourses, rather than resolve it.

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#52884

Unusual board with BGA | 13 December, 2007

meatings essenchal part of the work.

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#52887

Unusual board with BGA | 13 December, 2007

Wow. Thanks for all the valuable input.

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#53018

Unusual board with BGA | 21 December, 2007

Hey SWAG- Not an uncommon scenario where I'm at. But the bottom line is, as others have said: Profile, profile, profile. Here, we have dedicated profile boards for each product we build and in most cases they're EXACT representations (my library is approaching 750 at this writing). Not only will it serve you in developing the initial profile, but it'll be there for you when you want to transfer to another line, diagnose a quality problem, develop a profile for your rework machine when the line installs the BGA reversed, etc.

We insist from our customers, at the quoting stage, that we need X profile boards and in most cases we get little argument for our request for both a 1st pass and a 2nd pass profile board (and wave if needed). It costs $$ in the short term but saves $$$$ in the long run. These boards also have real parts, except when price and/or availability are an issue. Then we'd use a mechanical sample, electrical defect, or a similar (and cheaper) part. Possibly, you'll have a scrapped board (built with an inadequate profile! Ah, the irony).

If they argue with us, we do the best we can- possibly using a similar-to board (which wouldn't help to profile your rework machine), but our caveat to them is: your boards will be built with our best guess. Without a robust and thorough profiling process, that's all it is: a guess. You'll make some sound assumptions and you may be ok, but we've all had boards that gave us trouble when at first, they looked like no-brainers. They way the joint 'looks' is NOT sufficient (though the bean-counters may assume so).

Make a dedicated profile board (a solder sample will work fine), and you'll nail it. Then box it up and store it away to keep it in good shape for when it's needed again, because it will be. Guaranteed. Best of luck, and Merry Christmas.

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#53025

Unusual board with BGA | 26 December, 2007

Thanks, rywman. I do have a solder sample along with dummy BGA's so we should have what we need. This BGA is actually 1152 pins (I didn't have that right in my original post). The bad part is that we are building only one board only and the actual functionality/test is a bit of a mystery as it's a proto for a complex box build. I'll leave that up to the double E's and keep my fingers crossed!

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#53027

Unusual board with BGA | 26 December, 2007

Amen to that!! Too many people lately trying to "get out" of rolling their GD sleeves, attaching thermocouples to the board (using their own preferred method), and running the board and profiler through the oven.

I'm sick of questions like "duh, pbbbbbbtttt, whut do i needs to set my oben to?" ...or "duh, are deez setpoints good?" ...or "duh, what is delta T?"

The trend seems to be.... people trying to get out of being engineers and fast-tracking their way to management.

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