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Urgent!! ... AI process after SMD Reflow Soldering

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LeeHoMa

#36643

Urgent!! ... AI process after SMD Reflow Soldering | 15 September, 2005

hi All,

I am new to this forum and got a technical problem as below. Please see if anybody can help to solve it:

I am currently producing one PCB board with 2 side SMD parts and all AI component in 1 side. I try to have both side SMD part soldered(via Reflow Soldering) first and then go for Automatic Insertion(AI).

Now my problem exists as customer queries whether the AI process will induce micro-crack to those SMD part's soldering point.

Do any of you has successful experinece in this? If so, will there be any document or article can elaborate under what condition(eg. Stress to the PCB) the SMD soldering will still be fine?

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#36646

Urgent!! ... AI process after SMD Reflow Soldering | 15 September, 2005

Is not a problem, I've done it. Be sure the insertion tooling and cut&clinch tooling are set to proper distances from the board. If proper, no deflection of PCBA should be observered during AI. Obviously, your AI Operator must be more careful with PCBA handling. I had mine wear clean white gloves and have extra ESD protection.

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#36648

Urgent!! ... AI process after SMD Reflow Soldering | 15 September, 2005

I'm curious about one thing. What kind of components are on the bottom, how many are there, and how are you processing (in particular how do you get glue and paste on) them?

Edited to add: You shouldn't have any problems (assuming your tooling heights are set up correctly, as Pete C alluded to) UNLESS you've got large, heavy, or warped boards.

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#36650

Urgent!! ... AI process after SMD Reflow Soldering | 15 September, 2005

Thanks Steve, good point about warped boards, which are common with doube-sided reflow. Centerboard support helps minimize on reflow. We did do modification to the workboard holders to ensure boards are secured. The boards where small enough that warping was not an issue. Also, running through a low temp, 100C, to flatten helps.

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LeeHoMa

#36651

Urgent!! ... AI process after SMD Reflow Soldering | 15 September, 2005

hi Steve/Pete,

Thank for your email to affirming our current mounting and soldering flow! In fact, I also don't see any problem for the pilot run(though in small volume - 500pcs).

However, the problem is - I am challenged by my customer that the AI process will induce stress on the PCB. Accroding to their experience, there is a chance to have micro-crack in the soldering point of those SMD parts. The worst case they encountered is the SMD component will be "bumped out" during Auto-insertion!

I am asked to provide some document or data to prove them why we can guarantee the micro-crack won't exist. Now, my engineers is working hard to measure the stress on the PCB during AI. However, we have no data showing the correlation between the vertical stress against horizontal pulling force or dislocation to the component! Do any one of you have this kind of data/articles?

Remark: There are around 80 SMD parts(most of them are 0805 or 0603 chip Resistor/Capacitors and few SOT23) and 20~30 AI parts (including E Caps and TO-220).

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LeeHoMa

#36652

Urgent!! ... AI process after SMD Reflow Soldering | 15 September, 2005

hi Pete,

By the way, in your successful example, what kind of soldering method is being used after the Auto-Insertion?

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#36653

Urgent!! ... AI process after SMD Reflow Soldering | 15 September, 2005

Wave solder.

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#36654

Urgent!! ... AI process after SMD Reflow Soldering | 15 September, 2005

Your not going to find the document for "guarantee" becuase none exist as far as I know.

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#36655

Urgent!! ... AI process after SMD Reflow Soldering | 15 September, 2005

Talk to the sales reps for your equipment. They might be able to put you in touch with someone who can convince your customers that what you are doing had been done for over a decade now on probably millions of boards and is a proven technology. Proven by, it working, not by theory or math. I'm thinking maybe you can find a big name company that uses the same process and will say that they make quality products.

Your problem is not one of engineering, it is one of perception.

I've done a little of AI with SMT already on boards, but have seen more problems caused by bad part info, and bad pin placement.

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#36662

Urgent!! ... AI process after SMD Reflow Soldering | 15 September, 2005

I just wanted to add I'm not saying there is no egineering aspect to this, just that it sounds like it is more to do with your customers perceptions. Ask why they think it could be a problem. Maybe they have had previous experience with it before. If so then can show why you are not having that problem.

And I want to repeat; talk to your equipment sales people. Especially the ones who sold you the AI equipment. In this industry good sales people work harder after you buy the equipment. They want you to use the equipment as much as possible. That way you buy more consumables and maybe more machines later.

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#36663

Urgent!! ... AI process after SMD Reflow Soldering | 15 September, 2005

Are they worried about the top side SMDs too, or just the bottom side? If it's just the bottom, maybe you can just glue them without reflowing. That way they won't be at risk of cracked solder fillets after AI.

Granted, you'll probably be glueing parts on as a touchup step, but it might get you past the bigger issue.

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LeeHoMa

#36669

Urgent!! ... AI process after SMD Reflow Soldering | 15 September, 2005

hi Stephen,

Thank for your comment!

Yes! My people also share the same view that customer is asking something which is in more theoretical side. They want us to collect a lot of statistical data to prove our process.

Anyway, customer is not only the King, ... but the GOD!

Since we are doing Power Products, the safety requirement is so critical. As what customer mentioned, they have experienced this kind of "component bumped out" or "micro-crack" in other OEM/ODM manufacturer. So, the only thing we can do is either provide them the existing document which contains the correlation data/Risk assessment or we have to measure it by ourselves(it will be a big headache to me).

I did contacted the AI machine supplier "Panaxxxx", however, they have no such information on hand. Anyway, will keep on to try in different channel....

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LeeHoMa

#36670

Urgent!! ... AI process after SMD Reflow Soldering | 15 September, 2005

hi Steve,

In fact, I am not so sure which side will have bigger chance to get problem(from my current pilot run, the defect is nearly zero). Top(componet side) or Bottom(Soldering side)? And what is the reason?

Customer do not mentioned clearly what problem they have seen in other OEM plant.

You are correct - if we cannot convince customer with this "AI after SMD Reflow process", one of the solution is just glue them before AI.

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Ken

#36672

Urgent!! ... AI process after SMD Reflow Soldering | 15 September, 2005

1. How did your customers preious supplier deal with this problem? 2. Why did they not alert you these sepcial needs during the quoting process? If they have special needs then relegate the parts to hand-stuff. Don't forget to adjust your price (increase) accordingly.

3. Burn-in test screen the assemblies. Even this will not guarantee long, fail-free operation in the field.

How the hell does your customer think their Computers, color printers, cell phones, dvd players, automotive PCM's, airline avionics systems, iPODS, handy-cam's, digital camera's, network systems etc. get assembled? Hand assembly? (clue: NOT!)

This shows how "plugged in" your customer is to the manufacturing world.

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Reflow Oven