Karen, This is a REALLY generalized question, so I suspect you may get a wide range of answers. It depends on your situation, your equipment & processes (wave solder, selective solder, cleaning, etc), and also very much on PCB type, thickness, layout, and density. I'll try to answer with a few specific examples from my own experience. - TH soldering to very thick PCBs with metal cores on heavy copper weights can require a little more effort to heat the PCB sufficiently to get proper solder fill to meet IPC-610 requirements. Equipment selection is critical, and designs should be optimized as best as possible to allow soldering. - Wave soldering vertically mounted TH parts can be sometimes problematic to keep parts "vertical" through the wave. This is best overcome with fixturing. - TH soldering in general of parts without standoffs can also be problematic. It is generally a bad idea to flush mount, as you need to leave spacing not only for your solder fillets, but also cleaning. I've also TH soldered a multitude of connectors where the spacing of the panel-mount flange must be tightly controlled with relation to the PCB surface - also best controlled with fixturing. - TH soldering of connectors with high pin densities and/or low-standoffs can make inspection of inner pin solder fillets difficult. With some sort of solder bath or rework equipment, removing multiple leaded components can also be an issue. - Another component that can be difficult is the hybrid connector, with some SMT pads and some TH leads on the same part. You will see a multitude of past TN emails on the best methods to handle these as well. I hope these examples help, but again, the question is pretty generalized. Kevin -----Original Message----- From: Karen Tellefsen [mailto:[log in to unmask]] Sent: Monday, September 28, 2009 11:34 AM To: [log in to unmask] Subject: [TN] What through-hole components cause the most process issues? This is for all you process engineers. What though-hole components cause the most trouble: those with many high density pins components with a lot of heat capaticty, such as heat sinks, transformers, etc.? Anything else? Do you wave solder glued SMT components, are any of these problematic? Thanks for your help. Karen Tellefsen - Electrical Testing [log in to unmask] 908-791-3069 --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 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 Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 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 Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------