target for good result with quality solder joint. Fine is not good enough. Agreed those mentioned form part of the process controls. With placement force, it will bring one to another level of process/assembly control. QFN is only a smaller issue when compared to LGA during SMT assembly. ________________________________ From: TechNet on behalf of Guy Ramsey Sent: Thu 10/13/2011 11:40 PM To: [log in to unmask] Subject: Re: [TN] [DC] QFN layout The QFN package provides only one important interconnect material; the terminal. It, and the board must be solderable. Design of the land pattern Design of the stencil pattern Selection and control of the solder paste These provide the material component of the interconnect, they are critical. If you have no control over these, you are at the mercy of these who do. Solder performance of the package Solder performance of the boards Performance of the reflow oven (given oven settings to achieve an appropriate time temperature profile). In my experience placement is not a big problem. Guy From: Robert Kondner [mailto:[log in to unmask]] Sent: Thursday, October 13, 2011 9:58 AM To: 'TechNet E-Mail Forum'; 'Guy Ramsey' Subject: RE: [TN] [DC] QFN layout Guy, We have 3 MY9s and a MY15. QFN placement is something that must be constantly monitored. Not perfect but good machine. Anyone who say anything more about a pick and place machine is a fool, liar or both. We get PCBs from customers and we have zero chance to control land pattern designs. It is not a QFN Placement problem we have here is a "Salesman Occupational Hazard" we are dealing with. Example: Go into a Ford Dealership and ask a salesman if Fords are reliable cars. You get: "Absolutely, No Problems!" Go into a Toyota Dealership and ask a salesman if Toyotas are reliable cars. You get: "Absolutely, No Problems!" Go into a GM Dealership and ask a salesman if GMs are reliable cars. You get: "Absolutely, No Problems!". So when you go into an assembly house and ask if QFNs are easy to place and you get " Absolutely, No Problems" guess what kind of person you are talking to? Answer, a salesman. Nothing wrong with sales folks but they are susceptible to a specific occupational hazards. As sales folks are constantly dealing with "Smoke and Mirrors" (just part of the trade) they tend to lose sight of truth. Placing "Spin" truth is just part of their game. Bob K. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Guy Ramsey Sent: Thursday, October 13, 2011 8:18 AM To: [log in to unmask] Subject: Re: [TN] [DC] QFN layout We have an MY15. We do a lot of QFN placement. We achieve fine results. -----Original Message----- From: TechNet <mailto:[mailto:[log in to unmask]]> [mailto:[log in to unmask]] On Behalf Of Paul Edwards Sent: Tuesday, October 11, 2011 12:46 PM To: <mailto:[log in to unmask]> [log in to unmask] Subject: Re: [TN] [DC] QFN layout Bob, We measure the part and PCB warp and vary the part vacuum release point based on that to insure we are not deforming the printed solder paste structure more than about 30%... Because the MyData can't do that we don't typically use the MyData for QFNs... Paul Paul Edwards Process/Quality Engineering Surface Art Engineering -----Original Message----- From: Robert Kondner <mailto:[mailto:[log in to unmask]]> [mailto:[log in to unmask]] Sent: Tuesday, October 11, 2011 9:49 AM To: 'TechNet E-Mail Forum'; Paul Edwards Subject: RE: [TN] [DC] QFN layout Paul, I don't think we are on the same wavelength. Are you telling me you can drop a part 50mil onto a board to avoid pressing it down into the paste? I cannot imagine doing that and getting any placement accuracy. That would be nonsense. It is in the force sensor where the machine detects board contact. Also, watch the board deflection as a part is placed, you would be surprised. The MyData's allowed me to slow down placement to where you can actually see this deflection. Bob K. -----Original Message----- From: TechNet <mailto:[mailto:[log in to unmask]]> [mailto:[log in to unmask]] On Behalf Of Paul Edwards Sent: Tuesday, October 11, 2011 12:09 PM To: <mailto:[log in to unmask]> [log in to unmask] Subject: Re: [TN] [DC] QFN layout Normally we set the machines to a height placement point for QFNs to fix the problem BUT you can do that on all machines and in ALL cases but when you can it eliminates most of the problems... Paul Paul Edwards Process/Quality Engineering Surface Art Engineering ----------------------------------------- ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________ --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 16.0 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 For additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________ --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 16.0 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 For additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------