Hi Reuven - while I whole heartedly agree that it would be much easier to do, how are we going to list a component specific function in the JSTD-001? That list of components would be a mile long and ten feet deep. The JSTD-001/IPC-610 contain requirements and criteria that are applicable to classes or groups of component technologies. The 40% maximum void criteria does not apply to all QFN style components so its inclusion would benefit some users but not all users which is a condition that the committee avoids. It would be great if the JSTD-001/IPC-610 specifications would take care of all of the component issues but there are some requirements/criteria which are design/component specific which are what drawing notes are intended for. Dave From: Reuven Rokah <[log in to unmask]> To: [log in to unmask] Cc: TechNet E-Mail Forum <[log in to unmask]> Date: 12/20/2013 01:51 PM Subject: Re: [TN] IPC-A-610E, Voids in Thermal exposed pad of QFNs Agree, It will be easier to define in the SOW (Statement of Work) the required percentages in accordance with IPC class 1,2 or 3. On Fri, Dec 20, 2013 at 9:37 PM, <[log in to unmask]> wrote: HI Reuven - If the QFN component has specific thermal dissipation or electrical grounding requirements, then the customer is leveling the 25% maximum void requirement for a data driven reason which is how we want such requirements to be determined. Not all QFN or BTC components have those specific physical requirements. Dave From: Reuven Rokah <[log in to unmask]> To: [log in to unmask] Cc: TechNet E-Mail Forum <[log in to unmask]> Date: 12/20/2013 12:35 PM Subject: Re: [TN] IPC-A-610E, Voids in Thermal exposed pad of QFNs Hi Dave, Its high power QFN and there are 8 QFNs on each PCBA. Heat sink is connected to the bottom side of the PCB. 40%-50% voids will not transfer the heat generated correctly. On Fri, Dec 20, 2013 at 6:38 PM, <[log in to unmask]> wrote: Hi Reuven - I would ask the customer where/how they arrived at the 25% max void value as it sure sounds to me like they are using the current BGA 25% max void criteria. I have to routinely explain to some of our customer base that just because the JSTD-001 specification doesn't contain a specific requirement, such as voids on a QFN thermal pad, it doesn't mean they forgot to include it the document. If fact, the opposite is very much true, the lack of a requirement or criteria for a specific topic item is typically proof that there is no industry consensus on what the requirement should be or that a requirement is not necessary. Now if a customer has established a QFN voiding requirement, then you need to directly work with them to discuss why they feel the requirement is necessary - and note that workmanship requirements drive product costs through process controls, inspection protocols and documentation. No free lunch (unless I can get Doug to buy). Dave From: Reuven Rokah <[log in to unmask]> To: TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask] Date: 12/20/2013 10:18 AM Subject: Re: [TN] IPC-A-610E, Voids in Thermal exposed pad of QFNs Hi All, I started with this issue because of my customer needs (max 25% voids) and argue with the EMS (one one the biggest) that its guide lines require 40% maximum of voids. In my opinion it should be included in the IPC-A-610 such as class 1, 2, 3 and above class 3 such as 10% voids (using vapor phase), should be agreed between the two sides. On Fri, Dec 20, 2013 at 3:04 PM, David D. Hillman < [log in to unmask]> wrote: Hi Joyce - sometimes we can get too technical and over think a component. As you detailed, there can be a number of inputs to the equation but not necessarily. We have been using the 50% maximum void rule for 5 years on QFNs and I have only 2 cases where we had either a thermal or grounding issue that required us to maintain a smaller voiding percentage of the thermal pad. Dave From: Joyce Koo <[log in to unmask]> To: 'TechNet E-Mail Forum' <[log in to unmask]>, "[log in to unmask]" <[log in to unmask]> Date: 12/20/2013 06:45 AM Subject: RE: [TN] IPC-A-610E, Voids in Thermal exposed pad of QFNs Correct me if I am wrong, as for the thermal goes, there are many factors just the voiding. For example, the requirements of heat transfer path - vertical vs side, MCM possibly will have multiple grounds that may required isolation of heat path. If you allow 50% voids, depend upon the thermal via path, you might missing one sector of the MCM heat conduction path all together (if it is vertically channeled). It is not as easy as a single number. It is a bit of scary when the design is so far above the supply chain. Joyce Koo Researcher Materials Interconnect Lab Office: (519) 888-7465 79945 BlackBerry: (226) 220-4760 -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of David D. Hillman Sent: Friday, December 20, 2013 7:36 AM To: [log in to unmask] Subject: Re: [TN] IPC-A-610E, Voids in Thermal exposed pad of QFNs Hi Reuven - I think that is a possible idea, however, what void percentage do you suggest and what technical data/investigative studies do you have to support the recommended void percentage? One thing to consider is that if a workmanship topic is missing from the JSTD-001/IPC-610 documents, it doesn't mean that the topic hasn't been reviewed. The IPC committees work hard to only put workmanship criteria in the specifications that is necessary and is supported by data. An example - the IPC-7093 BTC committee completed extensive efforts looking at the voiding of QFN thermal pads and found no industry consensus on a void percentage requirement. The JSTD-001 committee therefore has not included a maximum void percentage requirement in the 001 specification and the IPC-610 specification shows no examples of voiding requirements of QFN thermal pads. The workmanship criteria show in the JSTD-001/IPC-610 specifications results in added costs to products and processes so the committees are very careful to not add requirements unless there is technical data/justification. I know a number of OEMs/CEMS who have a 50% maximum void requirement on the QFN thermal pad unless the component has specific thermal or electrical functional requirements. The IPC-7093 specification has some good information on the topic of BTC thermal pads and voids. The committees would welcome any investigative data on the topic too. Happy Holidays! Dave Hillman Rockwell Collins [log in to unmask] From: Reuven Rokah <[log in to unmask]> To: <[log in to unmask]> Date: 12/20/2013 12:48 AM Subject: [TN] IPC-A-610E, Voids in Thermal exposed pad of QFNs Sent by: TechNet <[log in to unmask]> Hi TechNets, I didn't see in the IPC-A-610E any acceptability reference in regards with the percentage of voids in solder joints of exposed thermal pads of QFNs or other components with exposed thermal pads. I recommend to add it in the next revision. -- Best Regards, *Reuven Rokah* Mobile: 972-52-6012018 Tel: 972-3-9360688 Fax: 076-5100674 <http://www.rokah-technologies.com/>[log in to unmask] [log in to unmask] www.rokah-technologies.com This e-mail message is intended for the recipient only and contains information which is CONFIDENTIAL and which may be proprietary of RokahTechnologies. If you have received this transmission in error, please inform me by e-mail, phone or fax, and then please delete all of the original files and all other copies exist. ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________ ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. 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For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________ -- Best Regards, Reuven Rokah Mobile: 972-52-6012018 Tel: 972-3-9360688 Fax: 076-5100674 [log in to unmask] [log in to unmask] www.rokah-technologies.com This e-mail message is intended for the recipient only and contains information which is CONFIDENTIAL and which may be proprietary of Rokah Technologies. If you have received this transmission in error, please inform me by e-mail, phone or fax, and then please delete all of the original files and all other copies exist. -- Best Regards, Reuven Rokah Mobile: 972-52-6012018 Tel: 972-3-9360688 Fax: 076-5100674 [log in to unmask] [log in to unmask] www.rokah-technologies.com This e-mail message is intended for the recipient only and contains information which is CONFIDENTIAL and which may be proprietary of Rokah Technologies. If you have received this transmission in error, please inform me by e-mail, phone or fax, and then please delete all of the original files and all other copies exist. -- Best Regards, Reuven Rokah Mobile: 972-52-6012018 Tel: 972-3-9360688 Fax: 076-5100674 [log in to unmask] [log in to unmask] www.rokah-technologies.com This e-mail message is intended for the recipient only and contains information which is CONFIDENTIAL and which may be proprietary of Rokah Technologies. If you have received this transmission in error, please inform me by e-mail, phone or fax, and then please delete all of the original files and all other copies exist. ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________