I must be missing something here. I was astonished to see written: "Yes, you are missing that you are not allowed to = solder perpendicular surfaces. A piece of wire = could be bent to make a surfaces parallel to PCB; = component leads can't (at least on the component's side)." I've been giving this significant thought and = have spent some time searching for relevant information via Google. And I just don't get it. There has to be billions of circuit boards that = have been manufactured that consist of wire leads = pushed through holes and soldered. Many of those = are double-sided boards with plated-through-holes = but I'd bet that the majority of those boards are = single-sided with NO plated-through-holes. Now I'm being told by somebody (one person - = Marechiare) that practice is all wrong. I can't find any relevant information anywhere that supports this claim. So: I have to repeat what Vitaly asked: "Can you = reference any reputable source that supports your claim?" dwayne PS - I suppose that some of the modern LED = lighting assemblies that I am now seeing are = manufactured all wrong as well. Those consist of = 4 small PCBs assembled into a square shape, with = another PCB soldered across the end of the box = thus formed by the 4 PCBs. All connections are = solder bridges from one PCB to another. I'd be happy to look at some relevant standards = if anyone can point me in that = direction. Otherwise, I'm just going to have to = assume that Marechiare is making stuff up for the fun of it. dwayne At 03:29 PM 3/5/2010, Marechiare wrote: > > - Can you reference any reputable source that > > supports your claim? > >Elementary, my dear Watson, - any schoolbook on Physics, I almost >sure. But, please, take it easy, "claim" is not the best word to >describe my humble statement that the highest quality you company is >well known for "does not allow" you to implement sub-standard >technologies :-) > >Imagine a connector's pin is soldered to the PCB's other side single >copper layer without the pin being bent. > >You know that every material in the world expands or contracts as its >temperature changes. The expansion is expressed in ppm/=B0C or parts per >million per =B0C - coefficient of thermal expansion (CTE) . This >expansion has a second property, called Young's Modulus, defined as >how hard a material pushes when it expands. > >The connector's pin material may have CTE different to that of SnPb. >When temperature excursions occur, due to changes in either ambient >conditions or the power dissipated by the circuit, these materials >will expand differently, leading to the creation of stresses. > >The mismatch in thermal expansion will cause shear stress between the >solder and the connector's pin. After a sufficient number of thermal >cycles, the stress will eventually lead to work hardening of the >solder, which results in cracking of the solder joint itself. The >resulting intermittent electrical conductivity is unacceptable in >today's high reliability electronics applications. > >The shear stress between the solder and the connector's pin is roughly >proportional to the thickness of the solder cone and the thickness of >connector's pin. In case of perpendicular surfaces the SnPb thickness >can be a few millimetres, in case of parallel surfaces it can be a few >microns, that is hundreds times less. > >Of course, bent connector's pin (if the bending permitted) may not be >flat, but still the "effective thickness" of SnPb in this case is much >less compared to that in the case of non-bent pin. > >Best Regards. > >-- >http://www.piclist.com PIC/SX FAQ & list archive >View/change your membership options at >http://mailman.mit.edu/mailman/listinfo/piclist -- = Dwayne Reid Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax www.trinity-electronics.com Custom Electronics Design and Manufacturing -- = http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist