Differences

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--- decap:ceramic_glass [2012/02/11 19:37] – mcmaster
+++ decap:ceramic_glass [2016/12/03 20:49] – mcmaster
@@ Line 1: / Line 1: @@
-====== Introduction ======
+JM 2016-11 advice:
+  * Use "Top Heat (gentle)" for safest result
+  * Use "Top Heat (quick)" for less safe but cleaner result
-I (JM) would recommend thermal fracture if you are comfortable with a torch.
+===== Top heat =====
-====== Thermal fracture ======
+Gentle procedure:
+  - Place chip into heat spreader block
+  - Place chip + spreader into vice
+  - Torch heat spreader
+    * DIP28: ~10 seconds
+    * DIP40: ~20 seconds
+  - Begin torching top of chip
+    * Use the side of the flame, not the tip, for gentler and more even heating
+  - Every 5-10 seconds try to pry lid up.  If it is starting to budge, immediately do the next few steps
+  - Stop torching
+  - Gently pull lid up and over chip, hinging on the far side
+  - Separate lid from package
+{{:mcmaster:decap:glass_frit:quick_before.jpg?300|}}
+{{:mcmaster:decap:glass_frit:quick_after.jpg?300|}}
+Above: sample quick result
+Quick procedure:
+  - Place chip into heat spreader block
+  - Place chip + spreader into vice
+  - Begin torching top of chip
+    * Side or tip of flame better?
+  - Every 5-10 seconds try to pry lid up.  If it is starting to budge, immediately do the next few steps
+    * Listen for a small popping noise.  This usually indicates the lid has sheared from the frit and can be easily removed, possibly with slightly more heat
+    * If its not the lid, the package has probably cracked
+  - Stop torching
+  - Gently pull lid up and over chip, hinging on the far side
+  - Separate lid from package
+General notes:
+  * Wave torch back and forth to keep heat even
+  * FIXME: torch model I use
+  * DO NOT torch while lid is lifting.  Will quickly destroy bond wires
+  * Heat spreader can be aluminum or steel
+    * Steel won't be melted by propane torch
+    * Aluminum can melt if abused, but will conduct heat better
+  * If the package cracks, finish procedure and then assess damage.  The spreader should keep package integrity until assessment is done.  If the die cracks, the chip is probably a loss
+===== Thermal fracture (old) =====
 Procedure
@@ Line 27: / Line 70: @@
   * The die is exposed but still in the package
+==== Media ====
-===== Media =====
 Chip before (both identical):
@@ Line 43: / Line 85: @@
-====== Thermal  ======
+===== Lift-off =====
-Advantages
+Requires some form of torch. Heat up and pry up. Be careful not to let molten glass land on the IC. The best way to avoid this is to lift straight up and let it cool a bit before moving off to the side.
-  * Can completely remove a die
-Disadvantages
-  * Removed dies still may have an uneven bottom.  This can be solved by very carefully heating them on a surface that glass won't stick to until the glass melts
-====== Shearing ======
+===== Shearing =====
 The glass tends to be much weaker than the ceramic.  Therefore, its possible to shear a chip open by moving the top and bottom half in different directions.
@@ Line 73: / Line 112: @@
   * Unpredictable how it will shear
-====== Grinding ======
+===== Grinding =====
 I see no reason why you couldn't grind one open (eg with a Dremel) but it would probably take a long time and would require extensive cleanup after.
-====== Manufacturing ======
-Might provide some hints if we knew how these were produced
+====== Die ======
+This has been a problem area and so the best advice I have is simply don't try to remove the die unless there is a good reason.  If someone knows of a good way to remove glass affixed dies I'd be interested.  All of these assume the package has already been opened.
+===== Hot pull =====
+Procedure
+  * Heat lower package
+  * Gently pickup the die up with metal tweezers or lift up with a sharp knife (which can get between die and substrate easier)
+Surface tension makes simply plucking the die up difficult and so a knife tends to work better.  Unfortunately, metal tweezers / knives chip dies and plastic tweezers melt.  PTFE does a little better but puts off toxic gas (HF) when heated so its not a good idea.
+===== Crack-n-push =====
+Procedure:
+  * Score one side of the ceramic package well
+  * Heat package strongly
+  * Submerge scored side of package in water.  This should cause it to crack roughly along score marks
+  * Re-heat package
+  * Slide die out of open side of well with die
+===== Dissolve =====
+% HNO3 is known to dissolve the frit.  However, it would probably dissolve other things (ie the pins) as well
+It should be possible to use HF to dissolve the ceramic.  Maybe NaOH could work as well?
+===== References =====
+http://www.freepatentsonline.com/4992628.html
+http://www.ti.com/lit/an/snoa280/snoa280.pdf