Paul: Does the extra surface tension create more tomb stoning? And the concentration of stress results in potential for cracks? Regards, Ramon -----Original Message----- From: TechNet [mailto:[log in to unmask]]On Behalf Of Paul Edwards Sent: Monday, September 27, 2004 10:09 PM To: [log in to unmask] Subject: Re: [TN] ENIG vs. HASL plating with 0.5 mm pitch QFN components Paul, I've been building, first prototype then production PCAs, with 0.5mm HASL pads since 1991 with success... The HASL thickness variations are typically around 0.0007" and are in fact many times less than the variations in the QFP lead planarity. The problem I see with Ag is two fold in nature: 1) Ag adds no volume to the solder joint and increases the surface tension of the joint interface 2) Exposed Ag leaves low activation energy surface which can lead to tarnishing. This then serves as a chemical reaction repository and surface stress concentrator Paul Edwards Process Engineering [log in to unmask] Tel: 408-433-4700 FAX: 408-433-9988 Surface Art Engineering 81Bonaventura Dr. San Jose, CA 95134 DUNS: 944740570 CAGE/NCAGE: 1XZ48 -----Original Message----- From: Black, Paul [mailto:[log in to unmask]] Sent: Monday, September 27, 2004 5:25 PM To: [log in to unmask] Subject: Re: [TN] ENIG vs. HASL plating with 0.5 mm pitch QFN components I wouldn't feel comfortable using HASL for fine pitch parts. A past fabricator I used for HASL of through-hole boards would only guarantee thickness within +/- .001" and I can get a much flatter finish using Silver for the same cost. Regarding the HASL process and Lead, it is true that the current process will no longer be viable in the EU when the directives take effect, but it is my understanding that the manufacturers of HASL equipment are trying to adapt the process to the new SAC alloys. Thank you, Paul Black Manufacturing Engineer Kronos E-mail: [log in to unmask] Voice: (978) 947-1520 Fax: (978) 244-0568 www.kronos.com Improving the Performance of People and Business(tm) -----Original Message----- From: TechNet [mailto:[log in to unmask]]On Behalf Of Wenger, George M. Sent: Monday, September 27, 2004 4:57 PM To: [log in to unmask] Subject: Re: [TN] ENIG vs. HASL plating with 0.5 mm pitch QFN components Paul, I didn't make any comment about planarity or indicate that HASL couldn't be controlled and used for 0.5mm pitch because there are lots of companies using HASL for 0.5mm pitch. The reason I wouldn't recommend HASL is because of the pending RoHS/WEEE directives. Regards, George George M. Wenger (908)-546-4531 Reliability / FMA Engineer Base Station and Subsystems Group Andrew Corporation, 40 Technology Drive, Warren, NJ 07059 [log in to unmask] -----Original Message----- From: TechNet [mailto:[log in to unmask]]On Behalf Of Paul Edwards Sent: Monday, September 27, 2004 4:34 PM To: [log in to unmask] Subject: Re: [TN] ENIG vs. HASL plating with 0.5 mm pitch QFN components Joe, I disagree with Paul and George... The planarity issue with HASL on .5mm pitch parts is over blown. A good PCB fabricator can control HASL variations. HASL increases the volume of solder in the lap joint and increases and lowers the joint's bulk interface intermetallics. Paul Paul Edwards Process Engineering [log in to unmask] Tel: 408-433-4700 FAX: 408-433-9988 Surface Art Engineering 81Bonaventura Dr. San Jose, CA 95134 DUNS: 944740570 CAGE/NCAGE: 1XZ48 -----Original Message----- From: Black, Paul [mailto:[log in to unmask]] Sent: Monday, September 27, 2004 11:40 AM To: [log in to unmask] Subject: Re: [TN] ENIG vs. HASL plating with 0.5 mm pitch QFN components Joe, I would agree with George on both counts. In any case, I wouldn't choose HASL. It doesn't deposit evenly. In the case of your fine pitch and small components, you could end up with reliability issues. Thank you, Paul Black Manufacturing Engineer Kronos E-mail: [log in to unmask] Voice: (978) 947-1520 Fax: (978) 244-0568 www.kronos.com Improving the Performance of People and Business(tm) -----Original Message----- From: TechNet [mailto:[log in to unmask]]On Behalf Of Wenger, George M. Sent: Monday, September 27, 2004 1:21 PM To: [log in to unmask] Subject: Re: [TN] ENIG vs. HASL plating with 0.5 mm pitch QFN components Joe, Were you asked to recommend the type of pwb plating that is best for your simple board or were you only given two choices to pick from? If I had to pick from the two choices I'd pick ENIG. If I had to make a recommendation I wouldn't recommend either. My preference would be immersion silver. Regards, George George M. Wenger (908)-546-4531 Reliability / FMA Engineer Base Station and Subsystems Group Andrew Corporation, 40 Technology Drive, Warren, NJ 07059 [log in to unmask] -----Original Message----- From: TechNet [mailto:[log in to unmask]]On Behalf Of Macko, Joe @ IEC Sent: Monday, September 27, 2004 1:08 PM To: [log in to unmask] Subject: [TN] ENIG vs. HASL plating with 0.5 mm pitch QFN components Fellow techs, I have been asked to recommend the type of pwb plating that is best for a simple board with only a few components. The finest pitch component is a QFN, 64 pads, 0.5 mm pitch. There are some 0402 resistors and capacitors as well. My 2 choices are HASL or ENIG. Would someone please comment on which is best for 0402 and 0.5 mm QFN type components. 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