|Ask the Experts|
January 15, 2019
Regarding lead free, can I use the reflow ovens I currently have in production?
We are a very small US based EMS company doing work for small customers and none are specifically asking for lead free. If we are asked to build assemblies to this new standard, can I use my reflow ovens which I currently have in production, a Heller about 5 years old and a Vitronics about 7 years old?
|Expert Panel Responses|
As with any equipment related conversation there is selling and there is engineering and sometimes the line between the two can get blurry. At the end of the day, the proof is in the profile. In other words, there are certainly advantages to having more zones—with the greatest advantage being the ability to "Sculpt" the profile to address the tighter process window requirements of the lead free process. Basically, with more zones you can divide the 3.5 - 4 minute reflow profile into smaller segments and control those segments with greater precision. This can lead to tighter control over liquid time for example or faster ramp up or tighter Delta T across the product. But for a large majority of the applications out there a 5 zone oven is more than adequate for the task. See This Link At SMTNet Check out the link to the User Forum above and you will see real customers talking about their experiences with 5 zone ovens and having no problem running lead free on them—and this dialog is over a year old. You'll have to weed through it a bit but the initial thread and the threads from Jan 20 – Feb 5 are particularly appropriate. Bottom line is that the answer to most applications questions is typically application specific. So what works for one application may or may not work for another. So the best advice is to try it and see. Companies like Soldering Technology International offer Lead Free Training kits with boards and parts and can recommend pastes for testing. Kits can be chosen to mirror your customers' products so you can show the customers that you are "ready" by testing an equivalent assembly. Attach some thermocouples to the board and run some test profiles. Your oven vendor can work with you to optimize the profiles or get you set up with some good starting points for zone temperatures and belt speed. If the current oven can satisfy the profile, you're done! If not, you may want to send the board to your oven vendor to have it run on a machine with more zones and see how that performs. Bottom line: DATA RULES! Avoid rhetoric or debates on number of zones or nitrogen vs. air and use what works best for the application. You don't have to live with the Sales Person—you have to live with the oven. Let it do the talking!
Heller Industries Inc.
Much will depend on the physical characteristics of the assemblies and the condition/configuration of your ovens. Most likely, your Heller and Vitronics ovens will handle lead-free. But the only way to tell for sure is to run some profiles. Ask your solder paste rep for some tech data sheets on their lead-free pastes and see if your ovens can stand the heat. The use of a thermal profiler will be essential when setting up for lead-free assemblies. Products like the Datapaq Rapid Oven Setup will automatically convert your standard profiles to lead-free profiles base on the characteristics of the oven and the assembly.
National Sales Manager
You will have to ask Heller and Vitronics. One of the problems with older ovens is that they can reach Pb-free temperatures for small to medium loading, but the ramp rates are too high and large boards with large components have problems reaching sufficient temperatures.
CEO & Managing Partner
Typical ovens of this vintage have 5 heating zones, most newer ovens have a minimum of 7 zones. While it is possible to use the existing ovens, you can expect a reduction in throughput and an increase in the time spent perfecting the reflow profile.
Regional Sales Manager
OK International Inc.
To handle both the higher temperature of a lead-free solder, and in order to avoid contamination of the solder pot, modifications to the machines are needed for a "RoHS-Compliant" manufacturing process. Talk to the machine manufacturer, and find out whether your machine type can be upgraded, and whether it may require additional equipment to produce RoHS-Compliant products. Please note that lead also works as a "lubricant" in the solder pot, and that a tin-only solder mixture will also lead to higher levels of abrasion and even possible corrosion.
Industry Standard Manager
Almost any reflow oven MAY be capable of soldering lead free materials depending on the mass of the product, cycle time requirements, profile requirements, etc. You should evaluate the profile and cycle time requirements for the lead free products that you are building and determine if your existing ovens are capable of achieving them.
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