|Ask the Experts|
October 30, 2018
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?
|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.
Global Segment Manager
Air Products & Chemicals, Inc.
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.
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.
Integrated Ideas & Technologies, Inc.
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: http://www.bgarework.com/
Sales Manager - Martin Products
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.
Regional Sales Manager
OK International Inc.
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.
Vice President Technology
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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