Wave soldering LCDs

We are currently hand soldering a 25 pin 51x29x2.75mm standard LCD onto a double sided board. The bottom surface of the display is positioned 7mm above the board. We would like to wave solder this display for two reasons; improve solder quality and to increase throughput. Our main concern is thermal damage. What is the best way to wave solder this LCD without causing thermal damage?

Alan Robertson

Expert Panel Responses

Assuming the LCD is not going face down into the wave, wave soldering should not be a problem for this type of component. Make sure the wave system provides the correct preheat to the assembly prior to soldering and that you profile the assembly so that it meets the thermal characteristics of the component without exceeding them.

Edward Zamborsky
Regional Sales Manager
OK International Inc.

Ed Zamborsky is a Regional Sales & Technical Support Manager for Thermaltronics, located in New York. His position requires frequent customer visits throughout North America and the Caribbean and his position encompasses not only sales but the role of trainer and master applications engineer for all of Thermaltronics products. His expertise includes such specialties as hand soldering, convection and conduction reflow techniques, array rework, fluid dispensing equipment, and fume extraction. Ed has authored many articles and has presented many papers on topics such as; Low Volume SMT Assembly, Solder Fume Extraction, SMT Rework, BGA Rework, Lead-Free Hand Soldering, High Thermal Demand Hand Soldering, Lead Free Visual Inspection and Lead Free Array Rework.

Have you considered using a selective soldering machine for this process? You can consistently control the process, and the heat.

Todd O'Neil
National Sales and Marketing Manager, North America
Business Development Manager, DAGE | X-Ray component counting

Mr. O'Neil has been in the electronics manufacturing industry for over 20 years.

Many of our customers wave solder LCD displays on their circuit boards without any problems of thermal damage. All of the devices I have seen are rated for wave soldering but the biggest concern I would have is over preheating. Typical topside board temperature as the board leaves the preheat is 210-220 F and I would avoid using topside preheat. Depending on flux type, lead layout, orientation and lead length bridging could be a issue. If the leads are all inline keep them parallel to the conveyor. If you keep the preheat temperature in spec and dwell time in the wave to the minimum needed for good hole fill you should not have any issues with thermal damage to the LCD display.

Greg Hueste
Senior Applications Engineer
Speedline Technologies

Greg joined Electrovert in February 1984. Based out of the Electrovert applications laboratory in Camdenton Missouri, Greg has been in the process applications support role since 2000. His primary responsibilities include providing process and machine applications support for the wave soldering lines as well as process, machine and operations training. He also provides applications support for the reflow and cleaner lines. Greg is a PBET certified trainer and holds two patents on wave solder nozzle design.

There is another option other than wave solder. EFD developed a system that dispenses solder then uses a laser to heat the solder at the joint for reflow. This is much slower than wave solder, but should improve your quality and have even less thermal impact than hand soldering.

Alan Lewis
Director of Application Engineering
Asymtek

Mr. Lewis worked for The Aerospace Corporation for 6 years before joining Asymtek in 1993. He holds multiple patents in dispensing technology for electronics assembly and packaging. He has a Master's Degree in Mechanical Engineering from University of Missouri-Rolla.
NOTE: Mr. Lewis is no longer working at Asymtek.

I would think selective wave soldering systems or selective soldering stations would be able to handle this application quite well. Spacers could be used to keep the LCD off the board and the board could be process through the equipment. Since this is a double sided board, I would not believe you would need too much top side preheat to get the solder to flow to the top side of the board, so this would be helpful in preventing the component from overheating during the soldering operation. If you are currently manually soldering these components, you are applying more heat to each lead than they will see going over any wave solder system. Hence the heat from the wave or mass soldering system will be less than the heat from the solder iron, which should also help in improving the quality of the product. I say this because soldering irons are typically set at 650 to 750 F while soldering systems are typically set at 500F, quite a different. If more information is needed please ask more questions

Leo Lambert
Vice President, Technical Director
EPTAC Corporation

At EPTAC Corporation, Mr. Lambert oversees content of course offerings, IPC Certification programs and provides customers with expert consultation in electronics manufacturing, including RoHS/WEEE and lead free issues. Leo is also the IPC General Chairman for the Assembly/Joining Process Committee.

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