This shows you the differences between two versions of the page.
Both sides previous revisionPrevious revisionNext revision | Previous revision | ||
decap:epoxy_acid [2019/05/12 18:01] – [Table] mcmaster | decap:epoxy_acid [2023/11/18 11:49] (current) – [References] philpem | ||
---|---|---|---|
Line 6: | Line 6: | ||
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 | 0.3" |
- | | PDIP18 | + | | PDIP18 |
- | | PDIP28 | + | | PDIP28 |
- | | PDIP40 | + | | PDIP28 |
- | | (UL914) | + | | PDIP40 |
+ | | TO-99 | | Ceramic: 0.11\\ Epoxy: 0.07 peak | ||
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 ====== | ||
Line 260: | Line 272: | ||
- 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 | ||
Line 358: | Line 370: | ||
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 | ||
Line 423: | Line 446: | ||
====== References ====== | ====== References ====== | ||
* http:// | * http:// | ||
- | * CDCA: http:// | + | * CDCA: 403 errors (as of Nov 2023), archived in Wayback Machine: http:// |
+ | * Original URL: http:// | ||