| Folk's, | | I'm just tying up some loose end's on my Master's Thesis on solderballing @ wave soldering and the effect the topography of the mask / PCB has on it. | I was wanting to do a straw poll on you guy's as to the type of resist's you are using Gloss / matte, whether your using clean or no clean flux and so on. | I'm trying to guage what the industry std is ( if there is one) and so add in some more 'real life' other than what I've seen already. | | Thanks in advance gang | | JohnW | John
If we tell you, do we get a master's degree, as well? :-)
Seriously, the finish of the solder mask should not affect solder balling. What can do is the degree of cure or the Tg of the mask. If a mask is rock hard, the ball should not normally adhere, except to the flux layer. Most masks are less than ideal and can soften slightly under the ball, sufficiently to form a little conformal 'dimple' which tends to retain it in place. However, there is usually sufficient mechanical action in cleaning to displace the ball. The real problem is with "no-clean" where cleaning is not done and the ball embeds itself into both the flux layer and the mask dimple. This can be exacerbated by insufficient preheat, causing the solder to spatter as the flux solvent evaporates on hitting the wave, particularly with so-called VOC-free "no-clean" fluxes (which are not VOC-free, at all, but that's another story).
Hope this helps.
Brian
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