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| decap:epoxy_acid [2019/05/12 18:21] – [Table] mcmaster | decap:epoxy_acid [2023/11/18 11:49] (current) – [References] philpem | ||
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| Above: HSS endmills are relatively inexpensive (above were about $3 each) and work reasonably well. They may be a better option than more expensive endmills that last slightly longer | Above: HSS endmills are relatively inexpensive (above were about $3 each) and work reasonably well. They may be a better option than more expensive endmills that last slightly longer | ||
| + | |||
| + | 2021-12-29: McMaster has recently been using RFNA (instead of WFNA) which seems to be much faster on epoxy. Fast enough that I'm no longer pre-milling chips. This tends to be faster overall and removes risks of milling (damaging bond wires, etc) | ||
| General recommendation for pre-milling packages | General recommendation for pre-milling packages | ||
| - | ^ Package | + | ^ Package |
| - | | PDIP8 | | + | | PDIP8 |
| - | | PDIP18 | + | | PDIP18 |
| - | | PDIP28 | + | | PDIP28 |
| - | | PDIP40 | + | | PDIP28 |
| - | | TO-99 | Ceramic: 0.11\\ Epoxy: 0.07 peak | 0.31" | + | | PDIP40 |
| + | | TO-99 | ||
| Don't cool the bit. Heat weakens epoxy. You will go through bits relatively quickly. Carbide bits do last longer, haven' | Don't cool the bit. Heat weakens epoxy. You will go through bits relatively quickly. Carbide bits do last longer, haven' | ||
| Line 28: | Line 31: | ||
| * A few chips have higher bond wires than typical | * A few chips have higher bond wires than typical | ||
| + | Suppliers: | ||
| + | * 1/8 / 3 mm | ||
| + | * https:// | ||
| + | * 1PCs 1/ | ||
| + | * 2019-12-26: qty 10 for $20.93 shipped ($2.09 each) | ||
| + | * 5Pcs/Pack Carbide Flat End Mill 4-Flute Mentalworking CNC Tool 3mm Cutting Dia | ||
| + | * 2019-12-26: qty 5 for $15.25 ($3.05 each) | ||
| + | * https:// | ||
| + | * 3mm Carbide End Mill 4-F CNC Milling Cutter Bit 3*4*50L 55° VHM coating *5pcs | ||
| + | * 2020-09-06: qty 15 for $43.24 ($2.88 each) | ||
| ====== Copper bond wires ====== | ====== Copper bond wires ====== | ||
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| - Optional: mill out a cavity about the size of the die | - Optional: mill out a cavity about the size of the die | ||
| - Place IC in petri dish on hot plate | - Place IC in petri dish on hot plate | ||
| - | - Heat to 150C | + | - Heat hot plate to 100C |
| - Place one drop of FNA (possibly mixed with concentrated sulfuric) on center of chip | - Place one drop of FNA (possibly mixed with concentrated sulfuric) on center of chip | ||
| - Wait a few seconds | - Wait a few seconds | ||
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| Low cost technique using readily available materials. | Low cost technique using readily available materials. | ||
| - | Procedure | + | Sample procedure |
| - Heat bath to desired temperature | - Heat bath to desired temperature | ||
| - | * The solution will start forming black whisps when it reaches minimum temperature. | + | * TLDR: 200C is a good starting point |
| - | - Cook until done. | + | - Cook until done |
| + | * TLDR: check every 15 minutes at 200C | ||
| + | * Time varies greatly with temperature, epoxy type, and thickness | ||
| + | * Solution opaque => difficult to monitor. You might need to pour to another container to check | ||
| + | * That said, probably on the order of 10s of minutes for 200C | ||
| + | * 350C will take seconds even for a thick chip | ||
| + | - Pour off as much acid as possible and then rinse chip in acetone | ||
| Notes | Notes | ||
| * Temperature | * Temperature | ||
| + | * The solution will start forming black whisps in solution when it reaches minimum temperature. | ||
| * Higher temperatures make it go faster. | * Higher temperatures make it go faster. | ||
| * At about 300C fumes are a huge problem but I did decap a large plastic chip in about 10 seconds | * At about 300C fumes are a huge problem but I did decap a large plastic chip in about 10 seconds | ||
| * It may work best to reflux the acid as it will boil off rapid above about 275. I use a watch glass to cover the beaker which helps considerably and is easy | * It may work best to reflux the acid as it will boil off rapid above about 275. I use a watch glass to cover the beaker which helps considerably and is easy | ||
| - | * Water severely reduces effectiveness. | + | * Water severely reduces effectiveness |
| + | * Use acetone instead of water if possible | ||
| + | * If a chip is inspected and washed | ||
| * I put chips into a PTFE basket (drilled out smaller beaker) so that they can be quickly removed and inspected without cooling down the acid bath | * I put chips into a PTFE basket (drilled out smaller beaker) so that they can be quickly removed and inspected without cooling down the acid bath | ||
| - | * As the acid concentration drops it begins to boil up. This is extremely dangerous and can lead to boiling over. Mitigation: | + | * As the acid concentration drops it begins to boil up. This is extremely dangerous and can lead to boiling over |
| + | * Ideally | ||
| + | * Using big beakers | ||
| {{: | {{: | ||
| * Sulphuric eats most metals, although slowly. Expect pins and such to still be in tact, but the bond wires will likely break without any support | * Sulphuric eats most metals, although slowly. Expect pins and such to still be in tact, but the bond wires will likely break without any support | ||
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| ====== References ====== | ====== References ====== | ||
| * http:// | * http:// | ||
| - | * CDCA: http:// | + | * CDCA: 403 errors (as of Nov 2023), archived in Wayback Machine: http:// |
| + | * Original URL: http:// | ||