Item Subject: Baking of Plastic Components

Hi Jim

The need for baking of these parts can be linked to the type of materials (and 
combination of) used in the assembly of these parts. Some types of mold compound
are particularly sensitive to moisture absorption (eg on TQFPs) and thus need 
tighter controls. Mfg's control and environment are also important. Thus the 
need to bake or not as I see it depends on,

a.   who makes it, 
b.   what they use 
c.   how they control it.
d.   how the users use it

The IPC specs has specifications on the packing requirements and limits for the 
moisture content of the platic packages. Typically, we have seen that devices 
that are 'dry-packed with dessicants' are able to last more than 1 year storage 
with no increase in the humidity level within the mositure barrier bag. (Again 
this depends on the type of mositure barrier material and dessicant type and 
amount)


Jeff Tan
HP-Singapore
(65) 662-4457




______________________________ Reply Separator _________________________________
Subject: Baking of Plastic Components
Author:  Non-HP-JWEISS ([log in to unmask]) at HP-Singapore,shargw19
Date:    3/22/96 10:34 PM






          Our company is looking at the use of plastic components  on 
          a variety of hardware, primarily military and commercial 
          avionics types of products.  We have setup a special project 
          team that has studied the moisture
          sensitivity/baking/handling issues that arise when the use 
          of PEM devices are incorporated on a design.  The team has 
          written in detail, all the steps associated with the 
          implementation of an "ideal/should be" ( zero percent risk) 
          process.  This process addresses the identification of the 
          moisture sensitivity level of the parts during the hardware 
          design phase; identification/tracking labels and special 
          pacakging notes on purchase orders during procurement; 
          handling and re-packaging instructions for the Receiving 
          Inspection and Stockrooms personnel; baking, usage, storage, 
          tracking and equipment procedures for the Manufacturing 
          Floor.  In short, the "ideal no risk approach".

          The implementation of a process with this type of 
          complexity, dependent upon many inputs from various 
          functional groups and component suppliers seems very 
          difficult, if not impossible to control.  Additionally, the 
          cost of implementatiion seems to out weigh the benifits 
          associated with using cheaper parts in the first place. 
          Also my limited contacts in the industry indicate that 
          baking and controlling to this degree is not necessarily
          an accepted practice.  Some manufactures bake all parts 
          (PEM's), some bake selectively and some (seems like a 
          majority) do not bake at all. The only common thread, is 
          that no one has experienced (or is willing to admit) the 
          hardware failures associated with entrapped moisture.

          So my question is: Are the manufactures who bake, incurring 
          unnecessary costs and are being overly conservative in their 
          manufacturing process controls and addressing a non-problem? 
          Or are those who don't bake, ignoring a real problem that 
          will eventually catch up with them?

          Any opinions, statements of facts or fleeting thoughts on 
          this topic would be greatly appreciated.

          Jim Weiss
          Harris Corp.
          407-727-6872