×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

OTP versus soldering process

OTP versus soldering process

OTP versus soldering process

(OP)
Hi,
I have the option to use OTP microcontrollers (an old 87C42) on a surface-mounted board. I am wondering if the OTP can lose its contents when it is subected to the heat of the surface mount reflow. Or should I use sockets all the time? Did anyone go through an issue like this?
Felixc

RE: OTP versus soldering process

Follow the datasheet's specified heat flow cycle and you'll be fine.  I'm surprised to find an OTP in surface mount config, though... didn't realize they still made those combinations.

Dan
Owner
http://www.Hi-TecDesigns.com

RE: OTP versus soldering process

You should be fine but I would highly recommend using a flash microcontroller like most of the Microchip PIC families.  You can get them in surface mount packages and include a connector on your board for reprogramming them right in the circuit (without having to take the chip off the board).

RE: OTP versus soldering process

(OP)
Surface mounted OTPs were a popular item 10 years ago, before flash started taking the place.  Unfortunately Intel does not support these products anymore, although they still make them.

leonar40, this is for a "shrink down" design, that allows no software rewriting, so I am stuck with this MCU.  Take a look at the Zilog Z8Encore chips, they're cheaper than the equivalent PICs.

RE: OTP versus soldering process

OTP's used to come in two varieties, fuse-link and EPROM.  The fuse-link variety were programmed by physical destruction of fuses, which was extremely permanent and not affected by temperature.

The EPROM variety was basically a UV-erasable EPROM without a window, hence OTP.  Slightly less robust, but a short jaunt through a reflow machine should be no big deal, since they were capable of maintaining storage at 125ÂșC junction temperatures for years.

TTFN

RE: OTP versus soldering process

isn't OTP cheaper than FLASH ?

<nbucska@pcperipherals DOT com> subj: eng-tips
read FAQ240-1032

RE: OTP versus soldering process

(OP)
It is an older technology.  Flash devices are now cheaper to produce.
I'll try to manage enough space for PLCC SMT sockets so both ways will do.

RE: OTP versus soldering process

The answer to your questions is no, unless you are applying MASSIVE amounts of heat, this is in the data sheet.

Flash devices are only now starting to be cheaper for 8 bit processors, i can still get fairly powerful 8bit OTP processors from motorola that do the job and are dirt cheap...

I actually just started a design with a 16K ROM, 1.1K ram, full LCD driver, DTMF encoder/decoder, 4 8 bit i/o ports, PLL, timers, interputs etc for US$1.60... Like to see somthing like that in flash :) not likely :) but would LOVE to be proven wrong!! (i only really need the DTMF enconder/decoder, but this is cheaper than mode DTMF encoder/decoders that i could find with a cheap micro)

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources