Differences

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--- carrier:start [2013/10/20 14:59] – external edit 127.0.0.1
+++ carrier:start [2013/11/16 08:00] (current) – mcmaster
@@ Line 16: / Line 16: @@
 Bare silicon chip without a package and affixed directly to the circuit board. Use in cost sensitive (ie cheap) applications. Above is probably from a commodity wrist watch.  There seem to be two types:
   * Epoxy blob (below type): die is placed on board, bonded, and then covered with a blob of epoxy.  The most common type
-  * Upside down dies (above type): I'm not sure the exact mechanism the wires are attached
+  * Upside down dies (above type): likely WLCSP with underfill.  Basically a BGA where there is no encapsulant on the die and solder balls are attached directly to bond pads (see BGA below for example of this sort of thing)
   * Flexible circuit: these are common in the line drivers on LCD screens
@@ Line 45: / Line 45: @@
 Several dies integrated into one package.  Considerable variety.
+===== Flip chip =====
+A package where the die is mounted upside down.  Usually this implies BGA or similar package.
+==== Ceramic BGA example ====
+Had thermal paste to improve conductivity:
+{{:carrier:xpc7455:package_pasted.jpg?300}}
+After cleaning:
+{{:carrier:xpc7455:package_clean.jpg?300}}
+When most solder balls are removed on the bottom looks like this:
+{{:carrier:xpc7455:package_bot.jpg?300}}
+After dissolving some of the epoxy on the top:
+{{:carrier:xpc7455:package_some_top.jpg?300}}
+{{:carrier:xpc7455:package_some_side.jpg?300}}
+As can see in above though there was still some underfill left.  Next pictures show the epoxy/underfill not completley dissolved and some gunk (solder paste?) left in the center as well as some sort of spacer:
+{{:carrier:xpc7455:package_some_nodie.jpg?300}}
+{{:carrier:xpc7455:package_some_ga.jpg?300}}
+{{:carrier:xpc7455:die_some.jpg?300}}
+{{:carrier:xpc7455:die_some_closeup.jpg?300}}