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Solder ball crack

Charly

#28508

Solder ball crack | 10 May, 2004

Encounter solder ball crack after reflow, found the solder ball is out of shape after reflow, cross section view found that the solder mask opening is not good ( when we do comparason with diff. supplier substrate.) Does the solder mask shape will affect the solder ball strength and what is he desire solder mask shape for goo solder ball attach?

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#28515

Solder ball crack | 10 May, 2004

First some definitions, the two main types for solder masking near BGA pads are: 1 Pad, Non-Solder Mask Defined. In circuit board design, pads with spacing that does not allow solder (usually bumps) on the pads to contact the adjacent solder mask. [After reflow, this ends-up being a potato shaped ball, when looking at a section.] 2 Pad, Solder Mask Defined. In circuit board design, pads with spacing that allows solder (usually bumps) on the pads to contact the adjacent solder mask. [After reflow, this ends-up being kind of a mushroom shaped ball, when looking at a section.]

We like to use the solder mask definition on the board as is used by the BGA fabricator. As you imply, that doesn�t always workout well, when you have two suppliers. So, when we have to choose between the two, we choose non-solder mask defined.

When you say * �found the solder ball is out of shape after reflow�; we assume that you mean something other than the fairly standard ball collapse. Correct? Please tell us more. *�cross section view found that the solder mask opening is not good�; what do you mean? Solder mask defined?

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