Ask the Experts
October 30, 2018 - Updated
October 10, 2011 - Originally Posted

Contract Assembly in a Prison

I manage a small electronic contract manufacturing center located in a women's prison. All our soldering is done by hand using basic soldering irons and tools. What can you recommend for assembly of BGA components, QFN components, DFN components and MLP components? Are there techniques that allow for the assembly of any of these component types by hand using simple, inexpensive tools or machines?

M. L.

Expert Panel Responses

The best way to solder these components is using a hot air reflow station. Very difficult to use a hand soldering iron, especially for the BGA component. I would recommend that they purchase or have donated a hot air soldering system typically used for BGA repair. With modified gas tips they can enclose the QFN, DFN and the MLP with a gas cloud that will bring the proper temperature to the solder paste underneath the components. The BGA can be reflow in a similar fashion with this system. I would also recommend low residue flux solder paste due to the difficulty in cleaning the flux residue under these package types. They may want to consider using nitrogen to improve solder wetting. One concern is that these leadless packages are heart sinks and will take higher temperatures to achieve good reflow, therefore the potential for the board to delaminate and possible pad pull out. Also possible issues with rework if solder joints require repair. This type of soldering will require good process control.

Gregory Arslanian
Global Segment Manager
Air Products & Chemicals, Inc.
Mr. Arslanian has been involved in electronics packaging processing and equipment since 1981 including flipchip, TAB, wirebonding and die attach. Current responsiblities include R&D, applications, marketing and customer interaction.

Check with OK Industries, Hakko, AirVac (DRS24, DRS25or similar model). All of these companies (and others as well) have hot-gas (nitrogen or air) BGA rework machines that can be used to manually place BGAs, QFNs, LGAs, etc. very precisely, and will automatically reflow the component into place in a programmed manner. Pace also makes this type of machine with a built-in X-ray system, but that combination may be out of your price range. Then again, it may not. You would be surprised. With one of these systems to get you started, you can perform all of your other "standard" SMT print, place, and reflow or hand soldering processes, then with a small amount of tacky fluxyou can place and reflow most BGAs without having to print solder paste. With LGAs and QFNs, the parts can be pre-tinned, then placed directly onto the pads and reflowed using the same machine/method. Contact me if you do not understand the process fully. I will be glad to answer more of your questions directly. If you tell me where you are located, I can arrange for local reps to contact you directly, and they can assist you also in setting up the processes. It is not hard to learn to use these machines, and they are very versatile. I do not have a monetary interest in these companies, I am just familiar with them as I use them in my client's factories.

Richard D. Stadem
Advanced Engineer/Scientist
General Dynamics
Richard D. Stadem is an advanced engineer/scientist for General Dynamics and is also a consulting engineer for other companies. He has 38 years of engineering experience having worked for Honeywell, ADC, Pemstar (now Benchmark), Analog Technologies, and General Dynamics.

There are desktop stencil kits available that make deposition of solder on the board consistent and much faster than hand soldering. Most kits come with a stencil for printing, a hand held squeegee, and alignment brackets that create a pocket for board registration and repeatability.

Stephanie Nash
Integrated Ideas & Technologies, Inc.
Stephanie Nash is the Director of Technical Services & Marketing for Integrated Ideas & Technologies, Inc., a premier manufacturer of SMT stencils. She has been instrumental in the stencil design and technical support.

Yes, there are inexpensive techniques and machines to meet your requirements. We have a wide range of products that can take you to the next level with a manual align machine or an automated machine with vision alignment. All our systems are RoHS compliant for your assembly and rework of BGA, QFN, DFN, MLP, SMD, and Thru-Hole components. You will find everything you need at:

Scott Rushia
Sales Manager - Martin Products
Scott Rushia is a Sales Manager with Martin and is responsible for sales and service for Martin's rework and dispensing products. He has over 11 years of experience in the SMT industry and was in the semiconductor industry for 10 years.

The transition from leaded components to the packages you describe is very different then going from Thru-Hole to SMT. The BGA, QFN DFN and MLP packages typically require a split vision system for component alignment and all with the exception of the BGA, require precise solder paste application to be successful. I would recommend the one of the APR-5000 Systems (depending upon board size), these systems provide alignment, paste deposition and reflow in one simple and easy to system.

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.

There are tools that hold the parts while you hand print solder paste on the package. Then place this part on the PCB for local reflow. One such tool is QFN / BGA Repair Tool by Photo Stencil.

Bill Coleman
Vice President Technology
Photo Stencil
For over 18 years, Dr. Coleman has been the vice president of technology for Photo Stencil, working closely with customers to understand their printing requirements. His efforts have resulted in several new stencil products.

Reader Comment
Using a hot air rework station is your best bet. You'll need to have a stencil for the device, either one that fits the part or the PCB. Which one will likely depend on the PCB layout and the equipment you are using. Placing the part for larger pitch components can be done by hand with a fair amount of accuracy, but smaller pitch devices will be difficult to align without the aid of a vision system. If you can hand align the parts, then you can reflow them with a hot air gun, but this will take practice to gain the consistency needed. I'd recommend a hot air rework station, usually you can get into some basic ones for around $30K or less. Good luck!
TJ Hughes, Esterline Interface Technologies, USA.

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