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The Soldering Corner: Eliminating Non-Wetting and De-Wetting
By Shantanu Joshi, Regional Sales Manager, Koki Solder America, Inc.
parts of the pad or lead without sol- der. Non-wetting means that there is no solder on either the lead or the pad. The end result is either a se- verely weakened or failed electrical and mechanical connection. There are many causes of wetting issues, including inferior plating, damaged plating, contaminated plating, for- eign objects, improper reflow, and in- ferior component fabrication.
D
Reliable Solder Connections The reality on the manufactur-
ing floor, however, is that the process engineer may be locked into his or her BOM — at least for awhile. In that case, focus on what can be changed, namely the assembly process.
Common causes of non-wetting
or de-wetting are that the flux has not had enough time to clean the sur- face or that the flux evaporated early and allowed the surfaces to re-oxi- dize prior to reflow. If the option to change PCB or solder paste is not available, at least make sure not to use expired products. They should have a listed date, which makes this check simple enough. Reflow can profoundly impact
Trapped foreign object (left) and de-wetting on SOT lead (right).
to “push” the process window. The published process specifica-
tions will provide good results in the vast majority of soldering applica- tions. However, it might take target- ing a narrower soak range within the overall process window. Because it may not be apparent whether the soak is too long or too short, experi- ment with changing the soak toward the lower end and then toward the higher end of the process window range to identify the profile with the
ter the process window and a target within the process window range. This eliminates trial-and-error pro- filing when looking for the extreme corners of the solder paste process specifications. Contact: Koki Solder America,
Inc., 18510 Pasadena Avenue, Suite E, Lake Elsinore, CA 92530 % 951-245-8755 fax: 951-245-8655 E-mail:
roberto@kokiamerica.com Web:
www.kokiamerica.com r
See at IPC APEX, Booth 2738
e-wetting occurs when the pad or component lead wets fully, but retracts and leaves large
wetting, so verify that the soak time is within the process window provid- ed by the solder paste vendor. If the problem persists, it may be necessary
best results. KIC offers a profiler that has
something called “sweet spot opti- mization.” This allows the user to en-
March, 2018
EVS Improves Wave Solder Recovery Systems
Isle of Wight, UK — EVS Interna- tional is showcasing its EVS 8KLFHS with Sono-Tek at IPC APEX 2018. The EVS 8KLFHS sol- der recovery system offers a capacity of 12 lb (5.4 kg). Its integrated hop- per makes rapid transfer of dross simple and safe, and can speed de- drossing times by up to 75 percent. This provides a cleaner wave with less maintenance, less downtime and a re- duction in shorts and bridging. EVS’ new and refurbished equip-
ment offers: ROI in months (not years); improvements to the wave solder process; and ISO14001 gain or retain.
EVS solder recovery systems. Contact: EVS International,
Porchfield Business Park, Unit 2, Porchfield, Newport, Isle of Wight PO30 4QB, UK % +44-0-8451-30-47-33 E-mail:
sales@evsinternational.com Web:
www.solderrecovery.com
See at IPC APEX, Booth 3433
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