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September 4, 2018

Package-on-Package Rework

We need to perform some Package-on-Package (PoP) rework. The only package we need to rework is the top package. Can we rework the top package only, or should we remove both packages and then replace them both?

K.S.

Expert Panel Responses

Yesyou can rework only the top package. It can easily be removed with acombination vacuum cup (for removal) and hot gas solder nozzle (for reflow). Infact, if you have more than one layer, you can remove the layers one at a time. Our Martin Expert 10.6 Rework System can do it hands free. Please visit www.bgarework.com for more information onour Rework Equipment or call me at 603-627-8989 to discuss our solution in moredetail.

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Scott Rushia
Sales Manager - Martin Products
Martin
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.

Yes the top package (memory) for a PoP device can be removedseparately from the bottom. To be successful with this process, precise controlover the thermal profile is critical and the use of nitrogen is veryhelpful. Once removed, the site is prepared and a new top package issoldered on. Keep in mind you are putting the bottom device through 4thermal cycles. As long as it can handle this, it is very possible to besuccessful in this type of rework. Finetech has workedwith several companies, like Texas Instruments to help develop their PoP reworkprocess. For more information please visit www.finetechusa.comor give us a call at 480-893-1630.

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Neil O'Brien
Sales Director
Finetech
Neil O'Brien has worked in the field of electronic manufacturing equipment for over fifteen years and is currently Sales Director for Finetech, a manufacturer of precision rework systems and die bonders.

It is possible to rework the top component of a PoP stack. Care must be taken to prevent damage to the solder joints in the lowercomponent(s). During removal of the top component it is extremely important toavoid putting any downward or lateral force on the stack. Some peoplewill apply corner glue to the lower component to help prevent displacementduring the removal process. An automated rework system with a Zero Forceremoval capability will eliminate this extra step. After removal of the top component the intermediate pads must becleaned to prepare for the subsequent replacement step. A non-contactsolder removal is required. The small pitch used with PoP devices, andthe common tight perimeter pattern will likely require automation to achieveconsistent results. Solder paste isgeneral not used during the upper component re-attach. We recommend aflux dip using a simple flux well and no clean flux. Placement of theupper component is done prior to heating, so displacement of the lowercomponent is not an issue.

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Don Naugler
General Manager
VJ Technologies, Inc.
Don is the General Manager of VJ Technologies, Inc., a leading manufacturer of X-ray Inspection and Rework equipment for the electronics manufacturing industry. He has more than 20 years experience in development, manufacturing, and support of a wide range of capital equipment.

This would all depend upon the skills of thetechnician doing the work. The other element I would consider is the testing ofthat particular component due to the rework performed. Product Engineeringshould decide if the POP needs to be tested separately or can it be testedwithin the circuit of the product. Once this decision is made then theappropriate rework can place of rework can be defined.

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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.

The rework of POP devices with our micro oven tweezersnozzles has been very successful for many companies for many years. These nozzlescan be fitted onto the APR-XLS system or the Scorpion rework system whichfeatures auto profiling. Either system can be programmed to remove either thetop or the entire POP or a particular layer in multi-POP devices or stackeddevices. Keep in mind you will subject the bottom component to multiple reworkcycles and operator skill is required for site dressing the section thatremains on the PCB.

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Edward Zamborsky
Regional Sales Manager
OK International Inc.
Mr. Zamborsky serves as one of OK's technology advisers to the Product Development group. Ed has authored articles and papers on topics such as; Low Volume SMT Assembly, Solder Fume Extraction, SMT Rework, BGA Rework, Lead Free Hand Soldering, Lead Free Visual Inspection and Lead Free Array Rework.

This is a very delicate process. Precise control of the temperature profile is needed to allow the removal of the top package without disturbing the bottom package. The use of shims and or staking the bottom BGA package could help to prevent shifting or creating soldering defects such as shorts or opens during the rework process.

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Andy Price
Sales Engineer
Circuit Technology Center
Mr. Price has been a key member of the team at Circuit Technology Center since 1985. He has vast expertise, experience and understanding of complex circuit board rework, repair and modification operations. He is one of the most knowledgeable experts in this area across the globe.