Graham, I never meant to even imply that acoustic methods would be in-line or even off-line for inspection of ALL circuit packs. Acoustic microscopy requires immersion of the circuit pack in a fluid capable of transferring the acoustic energy efficiently to the component in question - hardly suited for manufacturing, real time inspection purposes. Please find the next version below, with an introductory section that I believe speaks to your concern. I also added the comment from Bob Wettermann about thinking about other things besides heat sinks. People, It has been suggested that I add underfill of flips chips, non-flow underfills and corner bonds. Joe Fjelstad kindly provided a reference for flip chips. However, I have never used a flip chip and I ain't doin' it! If someone wants/needs a section on that, then YOU are going to have to write it, because I won't. I am considering the others. Bev Workmanship Standards for BGA and CSP Underfills For general inspection of all circuit packs coming down a production line, apply only the portions of this document that can be performed visually to underfilled, uncovered CSPs and BGAs or those same types of components under fence and lid RF shields. The visual inspection rules do not apply to CSPs and BGAs for general production under single piece RF cans. This would require destruction of all product. However, all the rules apply for process development/product qualification where one is willing to sacrifice finished circuit packs to gain knowledge of the acceptability of the overall quality. Target - Class 1,2,3 * Component requiring underfill completely underfilled with a good fillet all the way around, the fillet just approaching the maximum component body height, completely cured, no encroachment onto other components and no voiding whatsoever Acceptable - Class 3 * At least 50% fillet height up the side of the component body * Small pin holes and voids are permissible provided they do not exceed 95% of fillet surface area and have a maximum diameter of 0.5 mm (0.020 inches). Acceptable - Class 1,2 * Component requiring underfill underfilled such that all balls are covered, but no evidence of an exterior fillet, no encroachment onto other components and no voiding whatsoever * Component requiring underfill underfilled such that all balls are covered, with or without an exterior fillet, no encroachment onto other components and only small voids, not touching any solder joints * Component requiring underfill underfilled such that all balls are covered, with or without an exterior fillet, no encroachment onto other components and even large voiding, but not touching any solder joints * A void or voids less than or equal to 50% around the perimeter of one or more solder joints Defect - Class 1,2,3 * Underfill completely missing from components where it is required * Underfill not completely covering all the peripheral solder joints * Voiding such that a void traverses the distance between two or more solder joints under the array device requiring underfill * A void or voids more than 50% around the perimeter of one or more solder joints * Material extending on to the top of the BGA or CSP * Uncured material * Underfill interfering with proper placement of a heatsink or other mounted or mechanical devices or would interfere with the assembly * There should be no evidence of underfill flowing out through holes under the device. * After curing there should be no visual evidence of cracks between the device surface, underfill or board. * There should be no evidence of damage to the board or device caused by contact with the dispensing needle or height sensor. * Underfill filler shows evidence of separation Special Conditions - Class 1,2 * Encroachment onto other components, but meeting all other criteria above for target or acceptable conditions will be dealt with as a pass/fail on a case-by-case basis -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Graham Collins Sent: Monday, June 08, 2009 7:17 AM To: [log in to unmask] Subject: Re: [TN] Underfill Workmanship Pass/fail Criteria Proposal 'morning Bev OK, here is a question for you. You've commented recently that you have an underfill requirement where the design means you can't use acoustic microscopy to inspect the part. Therefore, how can you expect a contract manufacturer to assemble that product to your specification? You've handed them an impossible task... And the way this is worded it sounds like an inline inspection step. How many manufacturers have this type of capability? It may be a reasonable requirement for very high rel equipment, but volume production??? For a smaller manufacturer who doesn't have a C-SAM machine on site this will either involve spending $$ on equipment and training, or they will have to contract it out ($$ and lead-time). Could the section on voids have some wording allowing a qualified process to be used without verification of voiding on each part? Similar to the BGA section in A-610? -------------------- From IPC-A-610 D: A BGA criterion defined herein assumes an inspection process is established to determine compliance for both X-Ray and normal visual inspection processes. To a limited extent, this may involve visual assessment, but more commonly requires evaluation of X-Ray images to allow assessment of characteristics that cannot be accomplished by normal visual means. Process development and control is essential for continued success of assembly methods and implementation of materials. Nonconformance to the requirements of Table 8-12 is a defect when visual inspection or X-Ray inspection is performed to verify product acceptance. Process validation can be used in lieu of X-ray/visual inspection provided objective evidence of compliance is available. --------------------- regards, - Graham -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Bev Christian Sent: Friday, June 05, 2009 3:04 PM To: [log in to unmask] Subject: Re: [TN] Underfill Workmanship Pass/fail Criteria Proposal Joe, Perhaps you have not been following the thread. Voids are included. So, here is the WHOLE THING plus with Bob's contribution added in. I'm getting requests to add in flip chip underfill, no flow underfill and corner bond adhesives. Groan. :) So there isn't anything already for flips chips? I've never used one, so I don't know. Anyone want to write a section of two? :) Bev Workmanship Standards for BGA and CSP Underfills Target - Class 1,2,3 * Component requiring underfill completely underfilled with a good fillet all the way around, the fillet just approaching the maximum component body height, completely cured, no encroachment onto other components and no voiding whatsoever Acceptable - Class 3 * At least 50% fillet height up the side of the component body * Small pin holes and voids are permissible provided they do not exceed 95% of fillet surface area and have a maximum diameter of 0.5 mm (0.020 inches). Acceptable - Class 1,2 * Component requiring underfill underfilled such that all balls are covered, but no evidence of an exterior fillet, no encroachment onto other components and no voiding whatsoever * Component requiring underfill underfilled such that all balls are covered, with or without an exterior fillet, no encroachment onto other components and only small voids, not touching any solder joints * Component requiring underfill underfilled such that all balls are covered, with or without an exterior fillet, no encroachment onto other components and even large voiding, but not touching any solder joints * A void or voids less than or equal to 50% around the perimeter of one or more solder joints Defect - Class 1,2,3 * Underfill completely missing from components where it is required * Underfill not completely covering all the peripheral solder joints * Voiding such that a void traverses the distance between two or more solder joints under the array device requiring underfill * A void or voids more than 50% around the perimeter of one or more solder joints * Material extending on to the top of the BGA or CSP * Uncured material * Underfill interfering with proper placement of heatsink * There should be no evidence of underfill flowing out through holes under the device. * After curing there should be no visual evidence of cracks between the device surface, underfill or board. * There should be no evidence of damage to the board or device caused by contact with the dispensing needle or height sensor. * Underfill filler shows evidence of separation Special Conditions - Class 1,2 * Encroachment onto other components, but meeting all other criteria above for target or acceptable conditions will be dealt with as a pass/fail on a case-by-case basis --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------------------------- This transmission (including any attachments) may contain confidential information, privileged material (including material protected by the solicitor-client or other applicable privileges), or constitute non-public information. 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