Hi Charles! That's what I'm talking about! This is a list for discussion, right? I may be playing "Devils advocate", or just being a little pessimistic. We're really trying to get a handle on our moisture sensitive component handling, and things have changed, or matured about MS components quite a bit in the past decade. Like I said earlier, components that I thought that weren't moisture sensitive, seem to be now. Some of that could be my lack of awareness. I thought that large QFP's, PLCC's, PGBA's, some thin plastic packages, etc., were the ones that one needed concern. It really suprised me today to learn that tantalum capacitors are classified as MS componets It seems now that ALL plastic packages need scrutiny as far as MS levels are concerned. This is going to be quite a task. This means that each manufacturer will need to be contacted, for each plastic part, if we are to truely comply with MS handling requirements. For a EMS company like us, that can be thousands of part numbers.... But just like you, I see a lot of shortcuts being taken, i.e.; >>"So the vendor will often package the parts in a Moisture bag and stick a label on there instead of going by the manufacturers MSL"<< I can kind of understand that rational, better to err on the side of caution, right? How many component manufacturers in this lead free frenzy are slapping a MSL 3 label (or greater), on their parts to make sure they can survive the high reflow temperatures of lead free? But what that means for someone like us, is that we get audited by customers, just like many of us do in how we deal with MS components. During an audit, if one of our customers see an unopened bag of components that has a label of a MSL 3 rating, they will want to see evidence that we have tracked the exposure to comply with MSL 3 requirements, even if we have a standard 63/37 process and won't expose the components to the high temperatures of lead-free. This is no small task as some have already alluded to... Don't get me wrong, I just don't want to get through an audit, I want to make sure that we're doing things right as far as handling MS components. But I'm seeing a lot of inconsistencies, and have a lot of questions about actual MS levels of components. Sorry if it seems like I'm venting...I'm just thinking out loud. -Steve Gregory- In a message dated 6/20/2005 5:17:25 PM Central Daylight Time, [log in to unmask] writes: Steve, I get parts all the time that are marked MS which are not. Or the same part with different levels marked on them. In our case I found out that on the P.O. there is a note that all components will be packaged and labeled IAW J-STD 033. So the vendor will often package the parts in a Moisture bag and stick a label on there instead of going by the manufacturers MSL. I recently got the same 4148 glass melfs from two vendors. Believe it or not one of them was marked MSL 3. Same manuf. Different vendors. -----Original Message----- From: Stephen Gregory [mailto:[log in to unmask]] Sent: Monday, 20 June 2005 12:50 PM To: [log in to unmask] Subject: Re: [TN] Moisture sensitivity levels... Hi Richard! You're right, trying to wrap my arms around this whole thing is going to be fun. I'm starting to learn more and more that what I thought wasn't moisture sensitive, is...or is being labeled as such. Then I get get components from distribution that haven't been sealed in a vacuum bag or labeled as a MSL component. It was that issue that raised the question by our stockroom clerk this morning. We had one SOJ28 that came in sealed with a MSL rating of 3, and then the other unsealed SOJ28 was a MSL 1. I found that out after checking with Cypress. But what threw me this morning was the Tantalum capacitor. This is a solid tantalum, a "Tantamount" as Vishay calls it. I never knew that tantalum capacitors were moisture sensitive. But the caps I have have a MSL 2a label on them. They also have a PB Free label on them. The finish is pure Sn. After digging around Vishays web page, one thing I noticed that all the Tantalums that have a Sn/Pb finish on them are MSL 1, and the PB Free are 2a. What if we don't solder using lead free solder? Do we still have to treat them as MSL 2a components. Further still, must I reflow at the higher temperature that Vishay is recommending in their profile if I'm using Sn/Pb solder paste? Kind regards, -Steve Gregory- Senior Process Engineer LaBarge Incorporated Tulsa, Oklahoma (918) 459-2285 (918) 459-2350 FAX |---------+----------------------------> | | "Stadem, Richard"| | | <Richard.Stadem@G| | | D-AIS.COM> | | | Sent by: TechNet | | | <[log in to unmask]>| | | | | | | | | 06/20/2005 12:12 | | | PM | | | Please respond to| | | TechNet E-Mail | | | Forum; Please | | | respond to | | | "Stadem, Richard"| | | | |---------+----------------------------> >---------------------------------------------------------------------------- ----------------------------------| | | | To: [log in to unmask] | | cc: | | Subject: Re: [TN] Moisture sensitivity levels... | >---------------------------------------------------------------------------- ----------------------------------| Also, Intel has some excellent info in their website about MSD handling. Check it out. The title is Moisture Sensitivity/Desiccant Packaging/Handling of PSMCs. I have also read several papers written lately that state moisture content of plastic BGA packages is one of the main causes of warpage of PBGAs during reflow (besides other factors). So, you could fix more than one reliability issue with a good MSD program. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Leo Higgins Sent: Monday, June 20, 2005 11:00 AM To: [log in to unmask] Subject: Re: [TN] Moisture sensitivity levels... The MSL rating achieved by a specific IC package is dependent upon the BOM used in the package assembly, the assembly process used, and mechanical design aspects of the package and package elements. BOM: The die attach adhesive, mold compound, solder mask, laminate substrate materials, etc., all have water absorption and desorption characteristics that greatly affect the MSL. Rapid heating may cause the material to fail in the bulk or more commonly a separation at an interface will occur. In general, the less water absorbed by the specific material, the lower the risk of bulk failure or interfacial delamination. Of course, if the material has low bulk strength or the adhesion strength is low, failure can occur even with very low levels of water absorption. Epoxy mold compounds will adhere better to some polyimide die passivations than others due to the presence of adhesion promoters in some polyimides. Die attach epoxy adheres much better to a bare Si or GaAs die backside than it does if the backside of the die is metalized with gold, which is common with GaAs. Die attach epoxies and mold compounds adhere better to copper surfaces than the silver plated regions on leadframes. This issues can greatly affect MSL. An IC supplier may source his devices from multiple assembly subcons that use different BOMs, but meet the IC supplier's qual spec. Consequently devices from one subcon may meet MSL1 and another subcon's devices may meet MSL3, so the IC supplier will normally spec all the product at MSL3. Assembly process: Interfaces need to be clean. Often interfaces are activated with plasma processing before bonding or molding. Often adhesion promoters are applied (e.g. to a leadframe). The bulk strength and adhesion of the various polymer systems (die attach adhesives, mold compounds, solder masks, PCB substrate resin, etc.) is greatly affected by the time/temp cure profile. Molded packages typically require a post-mold cure of 4-5 hours at approximately 175-180C to effect full cross-linking and optimized adhesion at multiple IC package element interfaces (die passivation, "bare" copper leadframe, silver ring around the leadframe die attach pad perimeter, silver plated tips of leads on leadframes, etc.). The proper cure profile minimizes the free volume into which water can be adsorbed, and minimizes the presence of unreacted epoxy side-groups to which water likes to chemically attach. So process control can greatly affect the resulting MSL. Mechanical aspects: A thicker package may have more mold compound so it may provide a stronger mechanical structure (e.g. MQFP vs. TQFP). This strength may help the package resist evaporating moisture induced stress and avoid crack propagation from an sharp point, like the edge of the die or the die attach pad. But the thicker mold compound cross section may also present a greater barrier to moisture diffusion during heat up when compared to a thinner package, so it is also possible that the moisture may escape before a crack forms in the thinner package. A small die on a large die attach pad may result in lower MSL than a larger die on the same die attach pad, especially if the die attach pad is silver plated. So, all of these issues effect the package MSL rating. Another issue is often neglected. After board assembly, the MSL rating of the devices does not magically improve to MSL1. Yet is very common for assemblers to neglect baking out an assembled board before subjecting it to rework. This may destroy the unit being removed (if not already defective) and neighboring components. Best regards, Leo Director of Applications Engineering ASAT, Inc. 3755 Capital of Texas Highway, Suite 100 Austin, Texas 78704 ph 512-383-4593 fx 512-383-1590 [log in to unmask] www.asat.com The information contained in this electronic message is CUSTOMER/SUPPLIER PRIVILEGED AND CONFIDENTIAL INFORMATION intended only for the use of the individual or entity named above. If the reader of this message is not the intended recipient, you are hereby notified that any dissemination, distribution and copying of this communication is strictly prohibited. If you have received this communication in error, please immediately notify the sender by electronic mail. Thank you. -----Original Message----- From: TechNet [mailto:[log in to unmask]]On Behalf Of Stephen Gregory Sent: Monday, June 20, 2005 10:26 AM To: [log in to unmask] Subject: [TN] Moisture sensitivity levels... Good mornin' all! I hope all you Dads out there had a wonderful Fathers Day! As I posted about a week or so ago, we're getting our stockroom personnel to really focus on component moisture sensitivity levels. But now I'm starting to get a little confused about how components are generally classified with their respective MSL ratings. I've always thought that it had to do with component body size and thickness, but now I'm finding out that it doesn't necessarily. My stockroom clerk showed me an IDT SOJ28 that came in sealed with a MSL 3 rating that we now have in our dry box because the package was opened. We have some Cypress SOJ28's and SOJ24's that are on reels that are not in original packaging, so I called Cypress and asked what the MSL rating is for the two part numbers and they are a MSL 1. Cypress gave me a link to the SRAM Qualification Report that states that. Now my stockroom clerk brought me some Vishay tantalum caps that have a MSL 2a rating label on them, and they are TNTC's. This is THE FIRST time I have ever seen a MSL label on a tantalum capacitor. Are these ratings based on qualification reports? Or can one look at the size and thickness of the part to base how you will handle it? Kind regards, -Steve Gregory- Senior Process Engineer LaBarge Incorporated Tulsa, Oklahoma (918) 459-2285 (918) 459-2350 FAX --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e 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 -----------------------------------------------------