SMD Soldering what am I doing wrong - Page 1
Forum section: electronics / beginners

author: djd_oz
author_rank: Contributor
timestamp: January 03, 2021, 08:42:05 pm
content: I've attempted to SMD solder using a hot air gun at 265C and by using applying solder paste using a syringe.As you can see, sometimes I'm getting a big glob of solder on the joints (too much solder?) and sometimes not enough. How can I improve on this?

author: Johnny10
author_rank: Frequent Contributor
timestamp: January 03, 2021, 09:02:33 pm
content: Everything you need to know about SMD soldering.https://www.youtube.com/user/jkgamm041/videos

author: S. Petrukhin
author_rank: Super Contributor
timestamp: January 03, 2021, 09:34:41 pm
content: A few words from me.1. It is best to apply the paste using a stencil.2. Uneven paste drops on both sides pull differently and do not align the components, even turning them crookedly.3. It seems to me that you do not have a very good paste or you have not warmed up the board enough - some melted areas look like clay.4. If you do not have the ability to dose the paste and warm up the board, apply an additional drop of flux to each component.5. Do not wipe with cotton pads or cotton swabs, use lint-free wipes.6. It will be time-consuming, but this board can be fixed: apply flux to each component, use K-tip to melt the two pins of the component at once - it will take away the excess solder, center, press with tweezers and remove the tip. Clean the tip of the solder every time.Do this - it will be useful for you to practice.

author: S. Petrukhin
author_rank: Super Contributor
timestamp: January 03, 2021, 10:01:05 pm
content: Quote from: Johnny10 on January 03, 2021, 09:02:33 pmI have my doubts about this. For example, here he just rips off the CHIP with tweezers, instead of melting the solder and removing it with a suction cup.His hands are shaking violently - apparently he is holding them to the canopy, not giving support to the palm.

author: djd_oz
author_rank: Contributor
timestamp: January 04, 2021, 05:43:06 am
content: Quote from: S. Petrukhin on January 03, 2021, 09:34:41 pmI'm currently using this paste ...https://www.jaycar.com.au/solder-paste-smd-syringe-15g/p/NS3046It does look like clay when it melts .... could it be the paste or is the temperature setting of the hot air gun too low? I'm currenlty using 265 C.

author: S. Petrukhin
author_rank: Super Contributor
timestamp: January 04, 2021, 06:23:42 am
content: Quote from: djd_oz on January 04, 2021, 05:43:06 amI think for manual soldering with a heat gun without heating the board, this is not enough even for the best paste. I usually set 280°C.

author: tautech
author_rank: Super Contributor
timestamp: January 04, 2021, 06:58:14 am
content: Everyone develops their own style which is dependent of the complexity of their PCB's and the investment in gear they're prepared to make.For repeatable results use stensils. Period.However SMD can be simple and Hakko K tips like S. Petrukhin mentioned can be a great help especially for rework.This thread has some good tips after you've watched the video by the OP in this post:https://www.eevblog.com/forum/beginners/so-surface-mount-it-is/msg1442590/#msg1442590

author: djd_oz
author_rank: Contributor
timestamp: January 05, 2021, 12:29:05 am
content: Quote from: S. Petrukhin on January 04, 2021, 06:23:42 amThank you ... increasing the temperature has made the solder look less dull and more shinny.

author: TheDane
author_rank: Regular Contributor
timestamp: January 05, 2021, 10:45:12 am
content: Looking at the board, I see quite a few components which aren't alligned with the pads (they sit at an off-angle) - suggesting to me that you're not using enough flux.A 'rather large amount' of flux ensures good heat contact, it will remove dirt and oxidation - and cause the component to move into proper alignment.Using a heat gun with all of the through hole components mounted so close (lots of plastic) is not a good idea imho. The plastic will most likely melt. Covering it with capton tape is a lot of work, so if this is a one-off board, it might be easier and faster to remove all of the through-hole components before reflowing the board/components.If this is a small production, it might be a lot easier to do all the SMD, cleaning and quality checking before moving onto mounting the through-hole components.