Through-Hole to SMT

Hi Gerwoman,

Try Digi-Key. I've been getting SMT components from them for several years. Quite often, the base part number is the same, with different suffixes for SMT and TH. For example, a 1N4148 diode can be obtained in both. 1N4148WSFSTR-ND is SMT and 1N4148FSTR-ND is TH.

They have many, many components of both types.

Mike

A GA

Like to add:

I think by entering the basic No will bring all the varients

For Components: or http://tr.im/GUxK

For Data Sheets

Hi Haajee,

Thanks for the GA and thanks for the links to the hard-to-find components!

For that, you also get a GA.

Mike

Sorry, it's really a matter of doing it one component at a time and checking manufacturers data sheets for the foot prints etc. You have to be V careful with some ICs, as the SM package may have a different pin out to the DIL version despite having the same number of pins (I found this on an ST microcontroller)
It is a pain in the ar$e.
I would make sure it is worth doing, as unless your volumes are high it may not work out cheaper. I did the exercise on 2 of our most common products and we didn't go SM in the end on either.
Del

I can fix the pin out issue in Orcad I have to enter new footprint info also.

Digikey is great - they have the best search engine, in my opinion. Just enter the base number, LM317 for example, and then you'll get a page worth of variants, some of them will be your SMTs. If you board is very old, the parts may be obsolete. In that case, go to the manufacturer's website and look up the part number - often they will have recommended replacements, if not - just get the description of the part and go back to Digikey and search by function.

One has to be very careful to the power dissipation. SMT components are usually much smaller than through holes ones. Your warm 1K resistor might burn in the SMT package. I often have to use many SMT resistors in series and parallel to meet the power and voltage requirements.

Same applies to diodes and capacitors exposed to high frequency.

Finally, maintenance, test, and assembly of SMT boards is harder as everything is smaller.

If you are careful, it will work.

Power dissipation & re-work are the problems of SMD Boards & components. So special consideratin is needed in the design as in addition this design is for more population on the same size of PCB which further worsens the conditions.

Cost on special tools for assembly & re-work and the skill is another aspect.

I think that SMT is for mass production and not for hobby.

Thanks everybody for the input. This is going to be a mass produced PCB so cost, tools etc. are not an issue.

Some of the parts are obsolete that is the main reason we are re-designing the PCB.

OK

Then I suggest have a detailed study of SMT & if possibly employ experienced in SMT Engineers & Technicians. Lot of time & money will be saved.

Another caveat is the voltage rating. A standard 1/4 watt resistor may have a maximum voltage of a few hundred volts, basically only limited by the power dissipation. But SMT resistors have a thin film that's rated typically at 100V. And they pop very easily, even from transients.

If there is a lot of logic on the board: consider "mopping" it all up in an FPGA.

Due to the high volume you are better off dealing with a large distributor like allied or Future electronics. Explain your needs and yearly quanities, send them your list of thru-hole components and let them do the work. If there are any required vendors etc. be sure to include the specs. The will also provide you with the component specs which will help with the new board layout.

Good idea, thanks!

www.mouser.com

Hi,

the I am almost done with the task of converting from through hole to SMT it was not as bad as I thought it would be. We'll see what kind of job I did later.

I just want to say that www.vishay.com were great, not only did they come back with a quick response to my inquiry for equivalents for a couple of diodes but also recommended a component that would be easily available through distribution.

Thanks for all the inputs.