Hello are there any specs from ST on reflow temperatures for a TSSOP 20 chip?

[mike louaillier]

Posted on July 15, 2017 at 21:58

can't find one word on their site about temperatures for soldering.

[Tesla DeLorean · Accepted solution]

Posted on July 15, 2017 at 22:22

Definitely an area where the documentation you'd expect to find such detail has it missing.

Google AN2639 Soldering Recommendations, couldn't find a linkable copy on ST's site. Have attached

________________ Attachments : en.CD00173820.pdf : https://st--c.eu10.content.force.com/sfc/dist/version/download/?oid=00Db0000000YtG6&ids=0680X000006HyZG&d=%2Fa%2F0X0000000b9Z%2FBgvxm1e710Ve1Nedl369SD8V4mVqOZqq.YxMmDzMZV4&asPdf=false

[mike louaillier]

Posted on July 15, 2017 at 23:01

thanx Clive One, yes and they don't have any references to AN2639. and no hope searching it out around here, either. maybe if i put in a few keywords it might help.

reflow temperature profile hot air soldering specs specifications method limits heat

AN2639 Soldering recommendations and package information for Lead-free ECOPACK microcontrollers

[T J]

Posted on July 17, 2017 at 01:12

Starting out, I wasn't sure what temperature to use;

almost 10 years ago, I built a toaster oven to re-flow my PCBs.

but I wasn't sure what temperature to use.

Some datasheets suggest 160C-180C and other datasheets suggest upto 260C for reflow.

I built the unit with Fibro-insulation, it gets to 275C

I carefully put my loaded PCB and ran it up to 250C

it worked, but I had to adjust some parts. I put that board through 7 times at over 200C

it still worked at 25MHz, albeit scorched with a tinge of burnt.

the moral of the story is that the temp is not critical for prototypes.

Lead free you need over 200C

Leaded solder needs over 190C to flow well.  ( 2 minutes duration)

Capacitors don't like the high temp, the capacity will degrade with excessive temperature.

I use through-hole caps for that reason.

[mike louaillier]

Posted on July 17, 2017 at 02:37

much obliged nick that's really what i wanted to know. for lack of information i've been using a hot air gun at 250C and i hope i didn't ruin anything. as for the caps maybe i'll just have extra large pads and set em with a soldering iron. i never touch the pads for more than about 2 seconds at a time. and for the SOICs and the TSSOPs i've had good results with the tip drag method. but where i really have difficulty is the MSOPs. i just don't have the dexterity. but i'm thinking that if i make extra large pads for the corner pins, i can pre-tin those pads and then anchor the chip just by touching the pads. then i can drag the pins.

from what i've read it seems that the hot air gun may be safer than an oven. i use an electric griddle to pre-heat the board.

smd smt surface mount soldering by hand .5mm .65mm

[T J]

Posted on July 17, 2017 at 04:22

I think it is too hard with a hot air gun, it gets up to maybe 1000C in the stream.

You will have a high attrition rate. Can you mount the air gun ? maybe use a dimmer to control the heat..

I use the solder mask Stencil every time now. much easier than soldering.

I avoid all BGAs and QFNs if possible, my parts are all LQFP/TTSOP usually.

I use Kicad and Hand Soldering pads work well if you need to rework parts.

I use PCBWAY.com, stencils are $25

I use the boarder-less stencils, and tape it to the bench, paste my board in a minute.

please clean your stencils immediately after use with warm soapy water and a gentle brush if any crust has formed

I never use parts below 0603 size to make the boards easy to manufacture.

Tiny parts also suffer from being overrated and under performing.

[mike louaillier]

Posted on July 17, 2017 at 07:20

sorry i misspoke what i use is a WEP 858D hot air rework station which seems to have good temp regulation. and i ordered some low-temp paste from ChipQwik that has a melting point of 138C.

aren't they in china? how long does it take to get that stencil? i'm in los angeles. it sure would be easier but i can't wait a week to get it.

and what size caps n resistors are cheapest in manufacturing?

[T J]

Posted on July 17, 2017 at 07:40

it takes 2 working days for the stencil and delivery is about 3-4 days including weekends

the PCBs take 4 days on the discount run.

my deliveries are usually within 6-8 working days.

caps and resistors;

use digikey.com to check prices, but 0603s are so cheap, dont worry too much.

it is the cap's ESR requirements that you must be careful with.

when you resolder a joint,

you must use flux.

metho and cotton buds to remove any excess.

[mike louaillier]

Posted on July 17, 2017 at 08:27

wow that's pretty damn good i'll try it. thanx 🙂