For more information, please contact Perry Eimers, Sales Manager, at (507) 345-5786 or at peimers@eimicro.com.

Getting Up and Running with Lead-Free Manufacturing

By Todd King, Manufacturing Engineering Manager, EI Microcircuits

Lead-free. Wonderful hyphenated word. Ranks right up there with: second-best, red-eye, and you’ve-got-to-be-kidding.

There are many “experts” in this field of study, many others who are well-educated in metallurgical theories, or inventory restructuring. It would be nice however, if all of these real experts would get together in one room, at one time, and hammer out a complete road map to lead-free conversion.

Unfortunately, our industry just isn’t there yet; here it is 2005, and 2006 is just around the corner. With the European mandate of July 2006 looming, the whole electronics industry is still in a state of disarray. As of this writing the powers that be have yet to recommend a metal standard, component manufacturers continue to go off in different directions, our customer’s customers want product now for validation, and we contract manufacturers are smack in the middle trying to work both ends.

We can’t wait any longer. Our customers want to see the real thing well in advance of the 2006 deadline. It’s time to get off the fence and start working the issues.

Having a plan for conversion is a must. We follow the Design Of Experiments format (DOE) when we test any new material or process. This helps meet the layout requirements of materials, testing the identical processes each material will endure, and the finished product criteria — printing, wet tack, wetting, visual inspection, price, availability, etc. Making the proper selection is extremely important.

Communication, documentation and identification.

Without those three words burned into your brain, you don’t stand a chance. All departments must communicate, every step must be documented and all parts must be identified. It is virtually impossible to go overboard on any of these three. Once the plan is in place, follow it. Keep good records and take pictures. Your customers will feel a lot more comfortable with your experience and technical know-how.

Lead-Free Parts

For years now, we have attended seminars on what makes a good lead-free solder joint. Everything was process-related. What we are finding though, is that the process is just the tip of this massive iceberg. It’s everything leading up to putting parts on the board that is proving to be the battleground.

As it turns out, component manufacturers have been making lead-free parts for years; some have just decided not to tell us. Many part numbers have stayed the same. Most chip components for example are lead-free. ICs and other components are a mixed bag at this time. The bigger issue is that some manufacturers are changing over completely to lead-free and some are changing part numbers while others are not changing part numbers. And there are others who are running dual lead and lead-free parts with different part numbers. If you are a contract manufacturer with multiple customers, some lead-free, some not, and each uses many of the same parts, you see where this is going. How do you stock dual inventories and keep track of everything on the floor and still ensure that your customer receives the product they order?

One way to track this monster is to identify all components coming into your facility as either lead or lead-free, and then mark each reel, tube or tray with a lead-free marking. We have found that keeping all things visually “out there” goes a long way toward maintaining control.

As you bring in lead-free parts, having some documentation from the vendor tucked away stating as such will possibly save you some legwork and headaches later on. A well-structured inventory room makes identification and location easier and less mistake-prone. At some point you will have to bite the bullet and purge your inventory of the majority of components not qualifying for lead- free. That cost is insignificant compared to even one production run of the wrong metallurgy. There will be certain components that call for dual inventory, based upon customer needs. This will probably happen for a while. Hopefully the majority of our industry will change over before this becomes too much of a burden.

BOM Conversion

If you think the screaming and gnashing of teeth was bad in the inventory room, try telling an engineer that he or she must convert a few hundred BOMs to lead-free. You can begin to feel their pain. Not only is it a cross-reference issue, but a lot of research will go into designing out a lead product and designing in a suitable lead-free replacement. We’re talking about some serious labor to do all this in a relatively short period of time. There are ways to make your engineering life a lot easier. We have purchased software and developed a close relationship with our suppliers to make this task come close to just needing our pushing a few buttons. It’s pricey, but that’s part of being a good provider. There will be those components which will still require additional attention, but a good contract manufacturer should be able to provide this service to its customer with minimal pain.

Documentation and communication with purchasing will be key here. We have customers — some with lead, some lead-free — requiring the same IC, but in their respective versions. If you don’t have your ducks in a row, you’ll never survive.

Here we go. You’ve got the right parts (on-time of course) and you’re ready to fire up the lines. Make sure it’s the lead-free line. Those of us running dual processes know that one misread routing, one interchange of letters or code could spell disaster. Again, communication, documentation and identification are your greatest allies. Having two solder pastes on the floor, two wave processes, two types of wire solder, etc. equals ten times the headaches.

Choosing a solder paste is the first challenge. The industry experts have narrowed the selections to SAC305 and SAC307. There are many other brand specific chemistries available too. As of this writing, IPC has not stated their preference yet, but are expected to do so some time during the first quarter 2005. So we are on our own to select pastes, bar and wire. Use the DOE (Design Of Experiments) format!

Moisture Sensitivity

The biggest change in the process, machine-wise, will be the higher temperatures required to melt the new solder. This introduces a new factor into the equation: moisture sensitivity. In the past, only the larger IC-type components were subject to delamination when excess moisture is trapped and then heated during the reflow process. Now that the process temperatures have been raised significantly, moisture sensitivity becomes an issue for even the small ICs. Careful attention to storage and possible baking will be necessary. This high heat also requires a narrower process window at the solder melting point. Standard components cannot withstand the high heat required for an extended period of time. More oven zones in our new ovens and good profiling techniques have helped us through this challenge.

Bar solder for the wave has its temperature issues, but more than that, and costlier, is the fact that the proposed SAC series solders cause stainless steel solder pots to deteriorate in a matter of months.
There are remedies for this, but they are not cheap. There is one type of solder which does not degrade stainless steel, and has evinced a lot of interest from some very big names. Wire solder will require some new hand soldering techniques in both time and temperature, but the changes will not be too bothersome once your employees get used to them.

When the new IPC 610 revision comes out, we are hoping some lead- free solder inspection criteria will be included. We’re not going to hold our breath for anything extensive. Experience in working with lead-free solder will be more valuable given the time frame in which we are working.

While this has just been an overview, it does give you an idea of how complex a conversion this is going to be. If you haven’t started yet, start polling your customers now to find out what they are going to require from you. This is not an overnight project. It will take months of research, design and testing for your procedures to work the way they should. We do hope our industry will set standards just as it did for Pb materials. But in the meantime, get your feet wet and gain that valuable experience.

First published in US Tech online.