Ask the Experts
November 5, 2018
Depaneling circuit board that contain BGA components
Are there any special requirements for depaneling or V-scoring to separate paneled circuit board if they contain BGA components. What are the best/safest methods for depaneling circuit boards that have BGA components?
Expert Panel Responses
Depending on the proximity of the BGA devices to the edge of the PWB, it is normally prudent to minimize any external stresses to the devices. Proper support of the array is paramount in order to prevent pad cratering type defects or fracturing the solder joints. Routing is the preferred method.
S T and S Testing and Analysis
Gerald O'Brien is Chairman of ANSI J-STD 003, and Co Chairman of IPC 4-14 Surface Finish Plating Committee. He is a key member of ANSI J-STD 002 and 311 G Committees Expert in Surface finish, Solderability issues and Failure analysis in the PWA, PWB and component fields.
All components and their interconnects should be protected from the stress that can be created by depaneling processes that flex or shear the PCB substrate. Small ceramic capacitors, BGA's, LGA's, QFN's, or any other components with minimal interconnects are particularly susceptible to damage. If the components are near the PCB edge, then de-panelizing with a router would be preferred. If you must use a shearing process, then tooling should be used to isolate the stress and prevent PCB flex.
Principal Product Engineer
Benchmark Electronics, Inc.
27 years experience working with electronic and electro-mechanical manufacturing and design (medical, automotive, military, computer, and industrial controls). Military veteran - served as a Combat Engineer with the United States Marine Corps.
Rotary-wheel (pizza-cutter) type depaneling can be effective. If this is used strain-gaging is commonly employed to ensure that any forces generated during the operation are not sufficiently large to cause damage to area array (BGA, CGA, etc.) package solder joints. In general, I prefer this type of depaneling. Of course, the board must be designed to accommodate pizza-cutter depanelization.
A thirty year veteran of electronics assembly with major OEMs including Digital Equipment Corp., Compaq and Hewlett-Packard. President of Colab Engineering, LLC; a consulting agency specializing in electronics manufacturing, root-cause analysis and manufacturing improvement. Holder of six U.S. process patents. Authored several sections and chapters on circuit assembly for industry handbooks. Wrote a treatise on laser soldering for Laser Institute of America's LIA Handbook of Laser Materials Processing. Diverse background includes significant stints and contributions in electrochemistry, photovoltaics, silicon crystal growth and laser processing prior to entering the world of PCAs. Member of SMTA. Member of the Technical Journal Committee of the Surface Mount Technology Association.
The best method is UV Laser depanelization.
Director of Quality / CLSSMBB
Mr. Bock has worked in the Electronics Manufacturing Industry since 1996. He has extensive experience in the PCB manufacturing industry along with PCB Assembly. He has spent 6 years working in Southeast Asia.
The component density on pcbs continues to increase with 2000, 3000 or more placements becoming the norm. Depaneling pcbs becomes more critical with complex boards, which have tighter pitches, more layers and increasing thickness. Depaneling introduces mechanical stress on a pcb that can cause premature electrical failure, or worse cause intermittent operation. The primary pcb problem manifested from the external forces of depaneling is edge delamination. PCB layer delamination can expose the board to moisture, fluids and surface variations.
Of the potential problems caused by delamination - surface variations present the most problems for BGAs. Surface variations change the coplanarity of the BGA putting undue tensile strain on the ball to pad solder joint. This coupled with the "normal condition parameters" can have adverse effects on product performance and life. Delaminations are irreversible under normal circumstances, IPC 7711 and 7721 does offer a repair procedure but this is costly and adds considerable time to the build cycle.
The key is to minimize stress during depanleing. Laser cutting and routing are the least traumatic for depaneling pcbs with BGAs, and it reduces/eliminates delaminations.
Mr. Harman is an SMT Engineer at ACDi and worked at Oven Industries as a Manufacturing Engineer. H's worked at Philips manufacturing ultrasound probes/circuitry. He holds three patents, one for an ultrasound probe design, and two for innovative rat/mouse zapper circuits. He attended Pennsylvania State University for Electrical Engineering.
It always helps if the BGAs are kept away from the areas where the depanel is taking place. We use a "pizza cutter" type of blade to depanel v-score, and a router for route tabs. Both of those impart very low stress to the PCB.
Kelly Atay, Sunstone Circuits
Random or intermittent opens can occur within BGA or micro-BGA components during the de-paneling process if the devices are located in close proximity to the edge of an individual circuit. Board flexure during the de-paneling process exposes the outer edges of the BGA device, and especially the perimeter balls and corner balls, to the highest levels of stress since an uneven fracture distribution is indicative of localized mechanical stress.
V-scoring typically leaves 1/3 of the board intact which in most cases is manually broken over a sharp edge resulting in stress within the board and the board-BGA device interface. De-paneling fixtures should be designed to fully support the board on both sides of the score line to minimize these stresses. A 'pizza cutter' type de-paneling wheel can also induce stress on a BGA device if they are too close to the edge of the circuit board. The safest de-paneling method is to use a router to separate individual circuit which is typically slower than breaking or cutting, but is the best option to ensure integrity of the board-BGA interface.
A similar intermittent BGA fracture failure can occur during in-circuit test if the board does not seat properly in the test fixture causing an operator to repeatedly reactive the test procedure resulting in unnecessary fixture recycling putting additional mechanical stress on the board. In both cases it is recommended to implement strain gage testing to provide real-time monitoring of unidirectional strain levels exerted during the de-paneling and in-circuit test processes.
Carlos Bouras is the General Manager of Nordson SELECT and has over 30 years of experience in the electronics manufacturing industry. Carlos's expertise is in process engineering, product development and manufacturing operations. For the past 15 years Carlos has focused specifically on automated assembly issues and is the holder of several US patents for non-contact dispensing and precision dispensing of adhesives for the packaging of microprocessor devices.
Using an automated router with a saw blade does not create much stress on these components however a test can be performed on the board itself during sawing to make sure no stress is causing any failure to the components. If the components are very close to the edge special fixture can be created as well to help avoid any damage.
Tom Herndon, SCHUNK Electronic Solutions