SURFACE MOUNT SOLDERING

[Kusojiji]

I bought some boards that have an NPN IC circuit and resistor to change logic to power outputs from a DCC decoder. I'm going to need AUX 3 changed to power for one of my upcoming projects and didn't want to wire directly to an IC chip.

Unfortunately, I have to solder the microscoping IC chip and no-see-um resistors. I decided to give heatpad soldering a try, so I bought some low melt solder paste and used a cookie kit cast iron pan.

First step was to ensure the boards were cleaned with IPA. Then it was adding some solder paste to the solder pads. I didn't put too much on it and it turned out that a lot of the paste was flux. Then place the components on the board.

I used an IH stove and set it to 170C. Let it all heat up and waited. After a little while, some smoke started coming from the flux, so I cranked the temp up to 180C and watched the solder melt and congeal. Once it had done that, I turned the heat off and took the pan of the stove.

When all had cooled, I ran my meter over the leads to ensure I didn't have any shorts/bridges between the leads. All checked out good. I also checked to ensure that the resistors had soldered correctly.

The kit came with 805 sized 1K resistors, but they proved to be too small as they needed a bridge to make the pads. I bought 1206 size SMRs and they fit perfectly.

That small board in the pic is an LED resistor board. I bought about 20 of them to help make installs a bit cleaner instead of having resistors just hanging out.

 

[ctclibby]

I bought some boards that have an NPN IC circuit and resistor to change logic to power outputs from a DCC decoder. I'm going to need AUX 3 changed to power for one of my upcoming projects and didn't want to wire directly to an IC chip.
View attachment 246839

Unfortunately, I have to solder the microscoping IC chip and no-see-um resistors. I decided to give heatpad soldering a try, so I bought some low melt solder paste and used a cookie kit cast iron pan.
View attachment 246847
View attachment 246848

First step was to ensure the boards were cleaned with IPA. Then it was adding some solder paste to the solder pads. I didn't put too much on it and it turned out that a lot of the paste was flux. Then place the components on the board.
View attachment 246849

I used an IH stove and set it to 170C. Let it all heat up and waited. After a little while, some smoke started coming from the flux, so I cranked the temp up to 180C and watched the solder melt and congeal. Once it had done that, I turned the heat off and took the pan of the stove.
View attachment 246850

When all had cooled, I ran my meter over the leads to ensure I didn't have any shorts/bridges between the leads. All checked out good. I also checked to ensure that the resistors had soldered correctly.

The kit came with 805 sized 1K resistors, but they proved to be too small as they needed a bridge to make the pads. I bought 1206 size SMRs and they fit perfectly.

That small board in the pic is an LED resistor board. I bought about 20 of them to help make installs a bit cleaner instead of having resistors just hanging out.

Good Job!

I would almost hazard a guess that your temp was low. Next time try 200C as that should allow the parts to move and lock into the pads when hot enough. Once you see the parts ... move ... you are done. I have found that if you squeeze a little of the solder mix across the pads, it all goes under the part tab and does not short between the pads when heated. In the 4th pix, looks like the 102 resistor is not on the pad.

Have fun!

L8r

 

[diesel]

I do it with a normal iron and solder by hand - with a few tricks. But I had 35 years in the industry.

 

[Kusojiji]

looks like the 102 resistor is not on the pad

Thanks! Yeah, that one came with the kit and is too small. It needs to be bridged, which is why I went with the 1206 size. The board was made for CRDs but they don't package them anymore.

Will be playing with the temperatures. The IH heater has big arrows for me to hit to crank up/down the temp, so easy to use.

and solder by hand

I've been soldering for a while myself, but not getting better at it now. As I get older, I'm starting to work with smaller, surface mount stuff of all things! Going the wrong way!

Adding lights, DCC, etc can be messy with wiring and components and I'd like to be able to clean up the runs. I'd like to make PCBs, but don't want the chemicals around for that process. I also need to find a good, easy program to use for the design. Then I'd use larger components.

 

[RhB Michael]

My short adventure with SMD size devices didn't go well earlier this week.

 

[Kusojiji]

Yeah, those tiny rf connectors would need somebody else's eyes to see.

 

[diesel]

For 2 lead components, I first make a small dab of solder on one PCB pad. Then I position the part in place with tweezers and heat the dabbed side. I try to make the part meet the pad but it might not always go down all the way. Then I go and solder the other side, with normal iron tip and solder application. Once that's done, I go back and re-solder the other side.

IC's are similar, I tack one pin and then another one on the opposite side. Then I solder the rest of the pins, coming back and fully soldering the tacked pads. Mistakes like blobs between pins can be fixed by "pulling" whereby you clean the tip and coax the solder away from the join and on to the tip.

I use a Weller temperature controlled iron with a small flat tip (I don't like the pointy ones), and 63/47 0.025" solder with RA flux. For repairs and adjustments, I use a tiny amount of paste flux (packaged in a hypodermic applicator) which I apply with a toothpick.