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June 25, 2026 - Updated September 23, 2013 - Originally Posted Selective Printing for BGA Components
We use common BGA packages on many of our low-end products. To save cost, could we print paste only on the pads that have functional requirements?
For example, could we print all the perimeter pads on a 120 pin BGA, but skip printing on 50 or more of the interior pads since they serve no function?
A.J.
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I absolutely think you should go ahead and do that, and save about 3 cents per BGA in paste. What most engineers do not understand about BGA balls is that they undergo huge lateral pressures during operation in the field, even inside a simple PC. The CTE mismatch between the standard FR-4 and most BGAs is significant, and for those with soldermask-defined pads, the extrusion forces that the soldermask puts directly onto the solder balls is even more so. The more solder balls you have, and the taller those solder balls are in height, the more modulus of elasticity and number of supports you have to collectively absorb these changes, the higher cycles to failure that component has. So yes, by all means, eliminate those "unnecessary" solder balls so you have even flatter loaves of cheese under there, and fewer of them, with a lot less modulus of elasticity, so they fail faster. Because you may be my competitor! 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.
At first sight this looks like a good approach - however I do not see the savings being significant. This is not an electrical connection question but a mechanical approach of the process. BGA balls go through a reflow process so you will expect a consistent collapse at the end of this process. Missing lands and also paste deposits can cause that collapse not to happen in which case you are going to experience mechanical stress of the component. You can try to experiment and perform some cross sections to have a better understanding of the effects taking inconsideration, of course the final application of your product is important too(excessive heat, vibration and other mechanical challenges can accelerate a potential failure in the field). Again, I really do not see savings to justify this approach.
Engineering and Operations Management, Independent Consultant
Georgian Simion is an independent consultant with 20+ years in electronics manufacturing engineering and operations Contact me at georgiansimion@yahoo.com.
Interesting question. I don't see where this would be an issue. I would check whether or not an underfill would be necessary to enhance the strength of the attachment, but other than that, I see no reason why it would be an issue.
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.
If the BGA is depopulated but PWB lands are present, sure, you can simply not print the lands where no balls are present. If, however, a BGA ball is present at a given location, the land must be printed. The reasons for this are three-fold:
Process Engineer, Astronautics
Fritz's career in electronics manufacturing has included diverse engineering roles including PWB fabrication, thick film print & fire, SMT and wave/selective solder process engineering, and electronics materials development and marketing. Fritz's educational background is in mechanical engineering with an emphasis on materials science. Design of Experiments (DoE) techniques have been an area of independent study. Fritz has published over a dozen papers at various industry conferences.
We should stick to rule to maintain equal or better quality, reliability and keep working to reduce cost. The uneven space between non-print BGA balls and paste deposited balls will create reliability risk and is not recommended for partial print at all. Even unused pads should be present in PCB rather eliminating or masking and should get soldered. Standardization,alternate BGA can be worked out for cost perspective.
Supplier Quality Leader, Ge Healthcare
Subrat has 10 year of extensive experience in PCB assembly process optimizing for quality, process includes screen printing, wave, reflow. He has a copyright in stencil design published in Apex Expo2010 at Las Vegas US.
In my opinion it is fine if some of the non functional points are not soldered. It should be understood that solder joints apart from electrical continuity provides mechanical strength. The usual thumb rule for PTH is 7 gms per solder joint is minimum required and similar rule can be extended to BGA also. Secondly in case of BGAs it should be ensured that all four sides have sufficient soldered joints to support the device.
Head-Quality, Astra Microwave Products, Hyderabad, AP India
Holds Degree in Engineering, started off as Scientist/Engineer in ISRO (Indian Space Research Organization) in Quality Assurance of Space hardware Electronics Production. Worked in the area of Parts, Material and Process; DPA, FA and Process Qualification for space and ground hardware. Later moved into Private sector and worked in the area of Quality Management Systems & ISO 9001 certification. Currently hold a position as Head-Quality in RF/Microwave Product manufacturing for Defense and Aerospace segment.
At what cost to the integrity , structural, of the component. Could you do it... sure. Should you do it ... no.Lets think of this as a bldg. I've got 12 vertical columns that support the structure. In actuality only 6 support the weight of the bldg. So I will leave 6 inches below those remaining six columns to save the cost of rebar & concrete. Bldg is supported but not to its maximum capability. I would say that not soldering all the contacts, functional or not could present several problems. You are now relying onthe perimeter pads to support the entire BGA. The lack of physical contact to the board by the unsoldered 50 pads would, I think, create the enhanced possibility of cracking on the soldered joints. Flex of the component in all probability would be greatly increased by the lack of the stability of the solder connection. When considering the minute cost of using solder paste to secure the component properly by soldering all the contacts you are stepping over the dollars to save the pennies ... Weighing the cost differential of the solder versus product failure & customer bad will... I go with soldering... Oh, major point would be.... are you a CM? If so is your customer going to allow this. One mans opinion!
President, JSK Associates
Based in. Northern California since 1971. Founded JSK Associates in 1979. Actively involved in soldering, cleaning, chemistries. 30 years experience in EOS/ESD control.
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