The aspect ratio between stencil aperture width and stencil thickness is the most important factor in stencil production. A factor of 1.5 times the thickness of the stencil is applied for aperture width. i.e. On a 6 thou (150 micron) stencil the minimum aperture recommended would be 9 thou (225 microns). The release of the paste from the aperture can also be dependent on seperation speed of PCB from the stencil and also the paste type (particle size being used). If you wish to discuss your particular application in more detail please feel free to contact me off line. Doug Black Technical Manager Dek Precision Screens Division Weymouth, England Tel: +44 (0)1305 760909 [log in to unmask] ---------- From: Taheri, Kamran To: [log in to unmask] Subject: Re: [TN] Need to know Date: 22 September 1999 18:37 I don't know what kind of printer you are using. But, usually the board pulls away "snaps-off" from the stencil. What type of stencil are you using? Do you have a slow snap-off option in your printer? > -----Original Message----- > From: Steffen, Don E [SMTP:[log in to unmask]] > Sent: Wednesday, September 22, 1999 12:24 PM > To: [log in to unmask] > Subject: [TN] Need to know > > Technetters > > I have a situation where I need the advice from the Technetters. I have an > assembly with HASL. In order to stay within the aspect ratio guidelines, I > must use a stencil that has a .0085 aperature opening, a 20 mil spacing, > and > I must use a 6 mil stencil. I tried this and when the stencil pulled away, > the surface tension pulled away the solder paste from the pad area. If I > were to go to a 5 mil stencil (which is outside the Aspect Ratio > guidelines), would this help me with keeping the solder paste on the pad > and > not on the stencil? Or is there another approach that I should consider > instead of going to another stencil thickness? Any help you can give me > would be appreciated > > Donn E Steffen > Senior Quality Engineer > VDO Control Systems > Auburn, IN 46706 > Phone (219)925-8887 > Fax (219)925-8710 > Email: [log in to unmask] > > ############################################################## > TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c > ############################################################## > To subscribe/unsubscribe, send a message to [log in to unmask] with > following text in > the body: > To subscribe: SUBSCRIBE TECHNET <your full name> > To unsubscribe: SIGNOFF TECHNET > ############################################################## > Please visit IPC web site (http://www.ipc.org/html/forum.htm) for > additional > information. > If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or > 847-509-9700 ext.5365 > ############################################################## ############################################################## TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c ############################################################## To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TECHNET <your full name> To unsubscribe: SIGNOFF TECHNET ############################################################## Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information. If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or 847-509-9700 ext.5365 ############################################################## ############################################################## TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c ############################################################## To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TECHNET <your full name> To unsubscribe: SIGNOFF TECHNET ############################################################## Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information. If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or 847-509-9700 ext.5365 ##############################################################