Hi Cor & All - In my experience, filling vias with solder can turn into a problem. When the material reflows, it often forms a bead below the surface of the board (aided by gravity). This bead may well turn into a short or an obstacle to placement of second side parts. The second part of the problem occurs when a cavity forms allowing process residues to fill the partially vacant via. My own preference is to either plug the vias with one of the via fill compounds or to tent them with solder mask. Most of the circuit board shops I am accustomed to dealing with have the ability to fill or tent. Regards - Kelly -----Original Message----- From: Cor Coolen <[log in to unmask]> To: [log in to unmask] <[log in to unmask]> Date: Friday, April 20, 2001 1:06 AM Subject: [DC] Paste screening of Through Hole Test Vias Hello to all of you, Currently,we are designing a double sided reflow board. All our assembled boards have to pass electrical test, preferably on a bed of nails. Is it good practice to close all through hole testvias by paste screening in order to create good vacuum conditions when testing ? So, I want to include these vias in the paste screen artwork. What is a good diameter in the paste screen for closing vias with a finished hole diameter of 8 mil ? Is there not a risk that the solder paste will flow through the via holes and causing shorts at the other side during the second step of reflowing ? The board has a thickness of 95 mil. Anyone has some experience in this matter ? Thanks in advance. Cor Coolen Board Designer ---------------------------------------------------------------------------- ----- DesignerCouncil Mail List provided as a free service by IPC using LISTSERV 1.8d To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF DesignerCouncil. To set a vacation stop for delivery of DesignerCouncil send: SET DesignerCouncil NOMAIL Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------- ----- --------------------------------------------------------------------------------- DesignerCouncil Mail List provided as a free service by IPC using LISTSERV 1.8d To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF DesignerCouncil. To set a vacation stop for delivery of DesignerCouncil send: SET DesignerCouncil NOMAIL Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------