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Modems reflow mistake

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Modems reflow mistake | 12 October, 2015

My greetings to all.

Time to time I receive the next results of modems soldering:



There is no any system (any sequence) in the placement of this unsoldered pins. Stencil was made from 0.12 mm stainless steel foil, apertures and pads are made 1:1. Solder paste is fresh EP256HAK (high activity no-clean solder paste by Kester, Sn63Pb37). Can someone explain it (why sometimes some pins are unsoldered) and, second, is this are flaw or not? I haven't X-Ray inspection to check solder joint inside.

Thank you for your opinions.

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Modems reflow mistake | 12 October, 2015

Hello Eniac, 1/- Insufficient solder paste, check your print (Printer/Stencil). 2/- If you've got good paste deposit, that could be contaminated pads causing poor solderability. Good luck.

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Modems reflow mistake | 12 October, 2015

IPC-A-610E-2010, Acceptability of Electronic Assemblies, 8.3.4 Castellated Terminations talks to the acceptability of solder connections on components like yours.

It’s tough to say from the pictures, but I’d say your issues are: Missing solder: Plate 1: Pin 6; Plate 3, Pin 1 & 3 Nonwetting: Plate: Plate 1: Pin 6; Plate 2: Pin 5 Dewetting: Plate 2: Pin 1,2, 6-8; Plate 3, Pin 2, 5, 6 & 9 Poor toe fillet: Plate 1: Pin 5; Plate 3, Pin 2, 4-6 & 9

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Modems reflow mistake | 16 October, 2015

Do you have a solderable surface (walls)? It looks like most walls have a silver arc at the top but some do not (especially the last link) which I interpret that it has been plated (in most cases). Is it possible that the component does not have sufficient plating in all the walls? I can't tell if the walls are bare copper or ENIG. Solder won't flow onto an unsolderable surface. If volume of solder is low you may try increasing the pad size if possible.

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Modems reflow mistake | 21 October, 2015

Dear DeanM, I have the same thoughts about quantity of solder paste. Also I think about poor wetability of some pads (walls) on modems. I'm glad that my ideas are the same like yours and other members of forum. I will try to increase pads dimensions.

Thank you one more time.

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