AVR-Chat

Hate to disagree but we always solder the case down to the board. (That is why the pad is on the board.)  I've never seen an aluminum case; might be RoHS which makes is a bit harder to solder even with Pb/Sn solder, just use more flux.

We've also moved away from this case since our pick and place machine doesn't like them.  There are lots of other case styles that are easier to use.

Regards,

Tim Gilbert
JEM Innovation Inc.
303-926-9053 (office)
303-437-4342 (cell)
720-890-8582 (fax)
www.jeminnovation.com
www.pdksolutions.com


  ----- Original Message ----- 
  From: George 
  To: AVR-Chat@yahoogroups.com 
  Sent: Wednesday, December 31, 2008 2:25 AM
  Subject: [AVR-Chat] Re: crystal mounting


  --- In AVR-Chat@yahoogroups.com, "Steven Hodge" <stevehodge@...> wrote:
  > am I supposed to solder the can to the big pad under it also?

  I dont know the particulay crystal but most 32k watch xtals are in a 
  tiny cylindrical metal case. If it is one like that then do not 
  attempt to solder it. It may be aluminium anyway which will be next to 
  impossible to solder. The heat will likely damage the crystal. The big 
  pad is probably to stop you putting any other pcb tracks under the can 
  which would short circuit them.
  My suggestion is to use a blob of light glue (e.g. somthing out of a 
  tube for general purpose office/home use) to hold the body to the pad 
  to prevent mechanical vibration. Don't use anything like bathroom 
  sealant which is nice and rubbery but contains an acid which could 
  cause damage.
  USe something you can peel off with a knife when you want to re-use 
  the crystal for the Mk II pcb...

  luck,



   

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