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decap:epoxy [2018/02/28 02:43] – [CLC ControlLaser FALIT] mcmaster | decap:epoxy [2020/02/27 20:57] – mcmaster | ||
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One problem from this lack of circulation is that it may create pockets of low concentration acid, leading to corrosion. | One problem from this lack of circulation is that it may create pockets of low concentration acid, leading to corrosion. | ||
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+ | ===== McMaster live 2019-11-10 ===== | ||
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+ | {{: | ||
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+ | Experiments trying to decap COB while keeping PCB intact | ||
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+ | TLDR best result | ||
+ | - Cut a polypropylene tube (ie from a microfuge tube) roughly the size you want to expose to acid | ||
+ | - Heat tube up to soften it | ||
+ | - Warm PCB | ||
+ | - Attach hot tube to PCB, letting plastic deform into place | ||
+ | - Let cool a little | ||
+ | - Seal outside of tube with silicone | ||
+ | - Let silicone cure | ||
+ | - Decap with gentle heat on hotplate (maybe 160F max) using 2 WFNA : 1 H2SO4 | ||
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+ | Above is a compromise between PP providing the best chemical resistance and silicone providing the best seal | ||
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+ | Silicone only experiment | ||
+ | * Made silicon dam by layering up | ||
+ | * Silicone surface cured, but internally didn't always | ||
+ | * Uncured silicone dissolved in WFNA and floated to top. This then cured and blocked the surface | ||
+ | * Interesting, | ||
+ | * Acid may eventually undermine the PCB, but eating the silicone itself came first | ||
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+ | Someone also suggested I should try PTFE gasket. In the past I had tried kapton which didn't work well (acid tended to wick into kapton). Maybe PTFE would repel acid better | ||
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* Practice on samples before trying something you care about | * Practice on samples before trying something you care about | ||
* Puts off nasty fumes. Make sure to have good ventilation | * Puts off nasty fumes. Make sure to have good ventilation | ||
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+ | From Sam Wagner: | ||
+ | * "We use a yterrbium fiberlaser. What you are doing is trying to cause the plastic compound to explosively eject the silicon beads. So a pulsed laser is critical. | ||
+ | * " | ||
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===== jamiecraig ===== | ===== jamiecraig ===== | ||
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* They do the whole chip but avoid die area | * They do the whole chip but avoid die area | ||
* Light Ray - IC Decapsulation | * Light Ray - IC Decapsulation | ||
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+ | ===== mcmaster ezlaze ===== | ||
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+ | TODO: add pictures, estimate material removal rate | ||
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+ | Basically this was too slow to be practical except for very small samples. That said, it did work very well. A quicklase or other higher throughput Nd:YAG system would likely work well | ||
====== Sandblast ====== | ====== Sandblast ====== | ||
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- | ====== A. Zonenberg etch rate measurement ====== | ||
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- | FIXME: move this somewhere better | ||
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- | Copper etch - 70 ml 3% H2O2 + 10 ml conc. HCl. Heat to 70C, agitate with magnetic stirrer. | ||
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- | Test sample was Altera Stratix IV. Silver or tin plated copper. Plating was gone after <1 min in etchant, metallurgy of the plating was not studied. 20 minutes of etching = 0.13mm removal so 6.5 um/min. This number is likely +/- 30% or so because the temperature of the solution slowly increased over the etch period. | ||
====== References ====== | ====== References ====== |