Moving to SMT components

Projects General Guidance
1

I have done a prototype of a project using through hole components, so that I could solder them myself while making revisions of the prototype.

I would now like to take my project to the next step and order a PCB with SMT components already soldered on from JCLPCB in order to reduce the size of it.

But I do not know which SMT components that match the ones I use today. Preferably they would have the same pin-out and other properties as the ones I use today in order to avoid major redesign.

I use:
TSOP38238 as IR receivers (https://www.digikey.se/product-detail/sv/vishay-semiconductor-opto-division/TSOP38238/751-1227-ND/1681362)

BIR-NM13C1 as IR transmitters (https://www.digikey.se/products/sv?keywords=BIR-NM13C1-ND)

How would I go about finding corresponding SMT alternatives for these?

2

You look in the data sheet, normally towards the end, where you will find a list of what packages the components come in.

It is unlikely that it will have the same pinout as the through hole part, but that will be shown in the data sheet.

3

Determine the critical specifications and use those to locate suitable parts. For instance, for your IR transmitter, it's likely that the emitted wavelength, power rating and beam angle are important. So you'd look for an SMD part that can pass up to 100mA, has a peak wavelength of around 940nm and a beam angle of something like 65 degrees.
For the receiver, a similar story - you're looking for a 38kHz receiver (pretty common/standard I think) with a supply voltage that matches whatever you're using (likely 3.3V or 5V).

One thing you need to think about is the physical aspect - your through-hole components will transmit/receive light in line with the PCB plane (unless you bent the pins of the components at an angle), whereas a typical SMD component will transmit/receive light perpendicular to the PCB, unless it's an angled part.

4

Consider also to buy and manufacture the SMT components yourself. That way you do not depend on JLCPCB stocklist.

5

Please do keep us posted on your project's progress. I would also like to start using SMT devices, and like you have no clue where to begin for selecting the correct parts.

I use JLCPCB for all of my PCB boards, and I seem to recall that if you need a part not in their catalog, they will get it for you. (Where in their site is the parts catalog, anyway?)

6

Agree. Most smt stuff isn't very difficult to solder at home either. Just use a hot plate and/or choose capacitors and resistors starting at 0603 upwards and stay away from 0402.

7

For those few of us who have never worked with SMT, why?

8

Because they are stupidly small, they are hard to see let alone solder.

9

That. Moreover, with resistors, 0603 is the smallest size where the value is still printed on the package. AFAIK on 0402 this is not or at least not always the case.

10

To give an update and answer questions:

I managed to find similar SMD components by going to Digikey and searching in the same category as the through hole ones. Then I used their very good filter to filter for surface mount components with the same properties.

Here is the JLCPCP part catalouge: JLCPCB Parts Library & Component Sourcing
Of course the part I found was not found in their standard parts. I asked support and they said that you login to your account, then go to "Parts Manager" -> "New Parts Request" to requests other parts. I'll have to try that.

Also if someone else I trying to find SMD parts for the same components I did, this is the parts I found for SMD:

TSOP38238 -> TSOP75338TT
BIR-NM13C1-ND -> IN-S63FTHIR(0603) or IN-S63DTHIR(0603) or BIR-HM235A-TRB(0805)

11

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