Have you micro-sectioned a board to ensure that it complies with spec? Is the plating in the through-holes of the correct thickness and quality? i.e. there are no 'smears' left after the board drilling, as these would cause plating defects. a. Insufficient wetting in PTH's can be caused by poor plating, boards are too cool, wrong flux (what are you using?), contamination of hole walls, to name but some. Poor plating - talk to your supplier. Boards too cool - heat soak the boards at about 100 deg C for about an hour (or two hours if you an afford the time). You may find, if the boards aren't kept heated durig the soldering operation, that you will have to return the boards to the oven every half hour or so to re-heat them. This should not be done more than twice, or the board will suffer too much thermal stress. Wrong flux - I don't know what you're using, but presume it is an RMA flux whose residues will have to be washed off after soldering. Contamination - depends on what it is. Either clean the boards thoroughly before soldering and then bake to dry them out, or talk again to your PCB supplier about supplying cleaner boards. If there are no other problems with the boards, heating them will probably be the answer, as it would prevent the solder from solidifying too soon. If soldering to a cold board, the solder will freeze on the surface of the hole walls, while the hotter core will travel a bit further before it, too, solidifies. This will give the appearance of non-wetting. See above. Flux, of course has an effect on the wetting action, but try heating the boards first. Hole size won't affect wetting. If it is too large, though, it may not hold the solder. This will be noticeable either because the solder has fallen out completely, or there will be a 'bump' or stalagtite at the solder side of the hole and a well at the component side. If you have been following board design guidelines, though, for the types of components you are using, you shouldn't be having this problem. Hope this helps a bit. Pete Duncan "S. Miller" <CircuitekAsi To: [log in to unmask] [log in to unmask]> cc: (bcc: DUNCAN Peter/Asst Prin Engr/ST Aero/ST Group) Sent by: Subject: [TN] Insufficient Solder Fillet in a PTH TechNet <[log in to unmask] ORG> 05/30/01 07:39 PM Please respond to "TechNet E-Mail Forum."; Please respond to CircuitekAsia Dear Technetters, My company has been conducting studies on implementing the use of robotic soldering in our assembly process. Whilst experimenting with such equipment, we found our product from our PCB source to have problems; namely insufficient wetting in the PTH or (insufficient solder fillet in the PTH). As we have never seen this problem before, we are no evaluating the root cause to rule out whether or not it is equipment related. Your advise on the following matters would be truly appreciated: a. What causes insufficient wetting/solder fillet in a PTH? b. What are the corrective actions for insufficient wetting/solder fillet in a PTH? c. Would preheating the PCB's eliminate this problem? d. Does the selection of flux have an influence on proper wetting/solder fillet of a PTH? e. Does the size of a hole influence whether or not proper wetting/solder fillet in a PTH is achieved? Any and all responses would be truly appreciated. --------------------------------------------------------------------------------- Technet 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 Technet To temporarily halt delivery of Technet send the following message: SET Technet 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 --------------------------------------------------------------------------------- --------------------------------------------------------------------------------- Technet 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 Technet To temporarily halt delivery of Technet send the following message: SET Technet 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 ---------------------------------------------------------------------------------