add compoment clearances and SMD rulesHEADmain

1 files changed, 38 insertions, 0 deletions

diff --git a/mechanical-specifications.typ b/mechanical-specifications.typ
index 767f795..ebb8864 100644
--- a/mechanical-specifications.typ
+++ b/mechanical-specifications.typ
@@ -399,6 +399,44 @@ All PCBs shall pass the following tests before assembly:
 
 #include "tables/pcb-electrical-testing-requirements.typ"
 
+==== Component packaging and repairability
+<component-packaging-and-repairability>
+
+SAME mandates through hole components at the time of
+circuit design. All components in the Bill of Material
+(BOM) must then be readily available and in production:
+BOMs must not include surface-mount, new old stock or
+end of life components.
+
+We acknowledge that some components might become
+unavailable later on. In that case, builders should try
+to find a suitable through-hole replacement. If none is
+available, we authorize the use of surface mount
+components, provided that they are soldered on a
+daughter board, to maintain SAME repairability goals.
+
+/ DIP first policy: All integrated circuits (ICs)
+  should use Dual In-Line (DIP) packages to maximize
+  field repairability and manual assembly using
+  through-hole soldering techniques,
+
+/ DIP sockets: When ICs are socketed, designs must use
+  machine, turned-pin gold-plated sockets. Stamped
+  or leaf-spring sockets are prohibited in Industrial
+  and Metrologic tiers due to long term contact
+  resistance drift.
+
+/ SMD adapter daughterboards: When an SMD component is
+  used as replacement of a now unavailable
+  through-hole IC, it should ne mounted on a
+  standardized adapter daughterboard: SOIC-to-DIP,
+  MSOP-to-DIP, etc.
+
+/ Clearance envelope: The combined height of the DIP
+  socket, daughterboard, and eventual SMD component
+  must not exceed the $qty(30, "mm")$ component
+  keep-out clearance from the PCB surface.
+
 === Panels <panels>
 
 ==== Geometry <panels-geometry>