Solder wicking is dependent upon a number of variables.
At the time of soldering the temperature of the lead, the temp of the pad, the hole diameter relative to the lead diameter and the cleanliness of the parts involved to be soldered and the type of solder and flux can all affect the solder wicking and quality of the solder weld or joint...
The board parameters you describe lead me to believe board temperature is not completely reaching the melting point of the solder... but there could be other factors to consider.
If your assembly folks are preheating the boards before the wave, they might not be letting it soak in the heat long enough... that's a lot of copper to heat, especially to get the inner layers up to temp... just a thought. The dwell time over the solder fountain also may be a factor...You might want to check the hole diameter relative to the pin geometry too... IPC-7251 http://www.pcblibraries.com/forum/ipc7251-pth-padstack-calculator_topic596.html The number of thermal spokes relative to the number of layers tied to the heatsinking copper will definitely affect the time required to heat up the lead and plated thru hole... That needs to be balanced with the required current carrying capacity of the spokes too... Lots of things to consider.
Good luck. Hope you find the issue and get the boards to solder correctly.
William Brooks, CID+
Senior MTS (Contract)
2747 Loker Ave West
Carlsbad, CA 92010-6603
760-930-7212
Fax: 760.918.8332
Mobile: 760.216.0170
E-mail: [log in to unmask]
-----Original Message-----
From: DesignerCouncil [mailto:[log in to unmask]] On Behalf Of Fred Dark
Sent: Friday, March 22, 2013 9:11 AM
To: [log in to unmask]
Subject: Re: [DC] Heavy copper planes and thru-hole soldering
Thanks Bob... Will consiter 8mil therm's(3per pad) and increasing the anti-pad as well to in theory keep heat in the hole longer..? Thanks again for the input...
Regard's, Frederick Dark Jr.
Manager Senior PCB Designer
Crestron Electronics, Inc.
22 Link Drive Rockleigh N.J. 07647
P:201.750.7004 ext.11320
F:210.767.5772
[log in to unmask]
-----Original Message-----
From: Robert Wolfe [mailto:[log in to unmask]]
Sent: Friday, March 22, 2013 11:13 AM
To: (Designers Council Forum); Fred Dark
Subject: RE: Heavy copper planes and thru-hole soldering
Fred,
Well a simple general rule of thumb is to try and make the all the connection thicknesses across all the plane layers required to add up to what you would want as the MAX copper connection as if it were only one plane layer.
Now on this power design with 2oz and 5 layers of gnd that might be a little tough.
But with 2 layers of gnd and spokes of say 8 mil with 4 spokes per pad if my memory serves me, seemed to work out?
So possibly trying 8-10 mil spokes with only 2 spokes per pad?
Thermal relief calculations are total thermal width should be 60% of the pad (land) size Which if course is based on one plane layer connecting so one cold extrapolate That if I need more layers I still need to roughly keep that relationship For solder-ability. I haven't seen any real numbers anywhere as to how much you can really get away with when trying to connect numerous planes to same net and have all connect to thru hole pins with thermal on many layers.
Haven't had to deal with this in quite some time but I seem to remember them being able to solder boards with roughly those numbers with no problem?
Bob
-----Original Message-----
From: DesignerCouncil [mailto:[log in to unmask]] On Behalf Of Fred Dark
Sent: Friday, March 22, 2013 10:28 AM
To: [log in to unmask]
Subject: [DC] Heavy copper planes and thru-hole soldering
Hi Designer council - I have a design where we have a power board that's 8 layers... the technology is surface mount and thru-hole... we are having soldering issues with the thru-hole parts getting the solder to wick up in to the barrel for IPC class 2... the most we have achieved is 30% of the barrel... the stack-up has 5 GND planes that these part connect to as a design requirement from the Ee... the planes are 2oz copper each and the thermals are 15mils that connect the thru-hole pin... component stack-up reference : .065dia pad, .085dia anti-pad and 4 - .015 spokes(45 degree angle), drill .035dia(FHS) component pin dia = .020dia... any suggestions..?
Regard's, Frederick Dark Jr.
Manager Senior PCB Designer
Crestron Electronics, Inc.
22 Link Drive Rockleigh N.J. 07647
P:201.750.7004 ext.11320
F:210.767.5772
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