Wick attaches to the logic board - Page 1
Forum section: electronics / beginners

author: lacek
author_rank: Regular Contributor
timestamp: July 10, 2017, 08:24:37 am
content: Hi,I am trying to clean pads off the Apple logic board (I have bought 2006 820-1889 logic board to practice soldering for $5). With hot air I manage to remove basically anything I want, then I want to clean the pads, apply new solder, put a new park back and apply heat to create a joint.My problem is that when I try to wick the pads (edit: actually a QFP row with a central heat sink) my wick attaches to the pads and is a pain to detach. I have seen videos by Louis Rossmann. When he wicks the pads I see that he puts wick and soldering iron on in and the wick immediately soaks with molten solder, but does not stick to the pad.see here:https://www.twitch.tv/videos/157884801at 23:30In my case the heat of the iron is just enough to soak the wick just a little bit, but first not all solder is absorbed by the wick, second the wick attaches to the solder on the pads (edit: of a QFP row).I see a number of possible explanations, and I would ask for a critical commentary.A) perhaps the board is too cold, and it should be simply pre-heated (it had room temperature)? I did not preheat it in any way (but I did not see Rossmann do that)B) perhaps Rossmann’s ironing station has higher power, and is sufficient to generate sufficient flow of heat that keeps the wick and the solber above melting point? With my soldering station set to 380 degrees I cannot remove that wick even if I hold it to it for 20 secons. If I set my soldering station to say 450 degrees, then it comes off after 2-3 seconds, but I feel this is wrong…C) I have been using 0.8 screwdriver tip, but I have soaked it in solder (and SMD flux) to make better thermal transfer possible. I feel I am optimal here.D) I saw Gootwick recommended both by Dave and by Rossman. I am using Weller wick. I feel this should not be an issue, but I have never had Gootwick in my hand. So perhaps is this the reason?E) One cut the wick before wicking, to detatch that 2 cm of wick from the remaining 1.6 meters of the wick? This should definitely reduce the heatsink.... but is it a standard practice?My equipment:- soldering station: Xytronic LF 1600- soldering iron tip: xytronic XY-B02 0.8mm screwdriver tip- wick: Weller 1.5mm T0051301099- flux: Amtech ARMA223TF

author: Rerouter
author_rank: Super Contributor
timestamp: July 10, 2017, 08:35:20 am
content: rossman mainly uses tips that have a wide flat surface on the end to get maximum surface area, more so than a chisel tips thin edge can doHe is using a high power iron, but for a single small pad it shouldnt need to be crazy, if you ran it over a QFP row, then i could see it grabbing, but not a single padThinner wicks are easier to work with, as the heat cannot flow away as easily,If a wick grabs, add solder to the top of the wick, you need the heat to flow through and remelt whats underneath the wick, onces its molten you then shift forward a mm or so and suck up whats left.If your heating a pad and its not melting, you may need to add flux, depending on the state of the board, and how much heat your dumping in to a wick you may have cooked off the flux on the next few mm of wick, so need some fresh flux to rip through the oxide layerIf it still doesnt want to play nice, add a dot of leaded solder to melt in before you flux the lot off, the dot of leaded will reduce the melting point to lower than even the leaded.

author: lacek
author_rank: Regular Contributor
timestamp: July 10, 2017, 08:44:07 am
content: Thank for your reply. It will allow me to refine my question.- I think I am using the same type of tip (its end is like end of a flat screwdriver, but I will order a bigger one: have 0.8, 3.2(too large) mm so I will order a 1.6 and will give it a try ).- I was indeed wicking QFP rowI have just called it pad. Shortcomings at my terminology.Maybe the stupid thing: I should have cut the wick before I use it, right? Sorry for naive questionI will edit my OP accordingly.

author: Rerouter
author_rank: Super Contributor
timestamp: July 10, 2017, 09:00:12 am
content: for wicking, the 3rd or 2nd last are the ideal ones.https://www.thelashop.com/images/P/15SST-TIP10-11-01.jpg

author: lacek
author_rank: Regular Contributor
timestamp: July 10, 2017, 09:12:40 am
content: Oh I see. My looks more like 6th..

author: tablatronix
author_rank: Regular Contributor
timestamp: July 16, 2017, 03:10:01 pm
content: I would add flux, good flux, not pen.

author: lacek
author_rank: Regular Contributor
timestamp: September 15, 2017, 02:05:25 pm
content: I am reviving this thread just to conclude. I have bought this flat end tip for wicking and it did not really help - I kept the iron for 5,10 seconds and the wick would not let go off the boards. My new soldering station (JBC with T245 iron) made this wick detach in under 2 seconds, although I used less optimal tip.This was large QFN ground pad, so it was a large heatsing (this was iPhone 4S logic multilayer defunct - no CPU - board i bought to practice microsoldering).

author: sanman
author_rank: Contributor
timestamp: September 15, 2017, 02:56:39 pm
content: When this happens to me it is because it is not hot enough.

author: suicidaleggroll
author_rank: Super Contributor
timestamp: September 15, 2017, 04:28:34 pm
content: What are you setting the temp to on your iron?