How to rework when I placed a chip at an angle?

Hello, I’m hand-assembling these boards I designed, and I must have bumped the board when placing it in the oven. The 2 chips I circled are rotated such that their leads are bridging the adjacent pads. Hopefully the image keeps its resolution; I can retake/repost cropped for more resolution if the defect isn’t clear.

How should I go about reworking these? I have a soldering iron, a T962A reflow oven, a crappy sparkfun hot air gun, and lots of flux.

Should I remove the chips and just redo them by hand (the pitch is plenty big)? Or could I just toss on a ton of flux & give it another cycle in the oven? Or should I use a heat gun, flux, and realign with tweezers once the solder melts?

This is 60/40 Sn/Pb solder.

I’d remove them, clean/clear the pads, and solder down by hand. Highly doubt a reflow would re-align it and I wouldn’t want to stress the parts, especially if you followed moisture guidelines at all.

Add this to your supplies to make your life easy:

Edit: May be worth trying the hot air gun too, but put kapton tape around the perimeter. What temperature do you set it to? Preheat the bottom of the board gently beforehand, it helps.

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There are several ways I might approach this.

  1. I have a mini hot plate (MHP30) which has been very popular recently. If the board is a 2L board, I would probably just heat it up from underneath and then nudge the part to the right place.

  2. With the MHP30, or with a board heater (a repurposed 3D printer heat bed), I might raise the overall board temp and then come from above with the hot air and nudge the part to the right place.

  3. If I want to really lower the risk of thermal damage to the part or the board, use ChipQuik low-temp solder to remove the part. I then thoroughly clean the pads with flux, wick, alcohol, wipe, and repeat.

  4. If the parts are low-cost wide-pitch parts, I have also trimmed leads off with a super-fine-tipped cutter and then knocked the leads off one by one.

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I second the use of chipquick. If it were me, my preferences are in order:

  1. gob chipquick on to all the leads by hand with a soldering iron. Pick the part up, clean off the leads and pads each with solder wick, place back down and manually solder (tack one pin, make sure it’s lined up right, solder all other pins.

  2. if chipquick is NOT an option, you can heat it up with hot air to pull it off, then do the same pad/pin cleanup and manual re-solder. Heating up with hot air alone is probably going to be too much work and thermal stress on the board, so this might not be an option without a hot plate to pre-heat it. Hence my preference for chipquick.

I guess I’ll add - if you get the area hot with air and melt the solder with the iron, you might be able to get the chip off without making a hash of things, keeping the solder molten long enough with the air to get in with tweezers. But that’s quite a bit of tool juggling. Chipquick would be better.

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I used to be a lot more sparing of the ChipQuik because it’s pricey. But I’ve found that I can reuse the blobs a few times and still get good results.

For drivers with thermal pads under the part, it’s much more difficult to use CQ. The MHP30 has been really convenient - well worth the $100 (even less if you can supply the USB-C PD power supply).

I don’t rework nearly enough stuff for the cost of chipquick to outweigh the sanity it saves me. But yeah, fully blind pads make it sort of a non-starter.

I do have chipquik, and this part doesn’t have an exposed pad, so that seems like it’ll go well.

Should I first use flux and wick then pads, then CQ, and then wick the CQ off of everything & replace? Or can I just go straight to getting CQ all over the pads and it’ll mix with the existing solder?

As Alex pointed out, just glob CQ on the leads and pads all at once. I usually leave my iron at usual temperature and just add the CQ and work my way around the chip quickly. The residual heat will usually be enough for the chip to come right up.

I then pick up the excess glob with the tip and wipe it on a dedicated sponge for doing CQ work. Then flux/mop/alcohol/wipe to clean the pads for reuse.

Less pricey if you buy a generic knockoff.

If it happens again despite being careful not to bump, look at anchoring or pre-heating. The board shape will let the narrow sections heat more rapidly than the remainder.

What I do there is just heat it up with the hot air gun, apply some flux, then realign it with a pair of tweezers while still heating, and using as little movement as possible. If the pads are still bridged and you applied enough flux then try tapping the top of the chip a few times, as a small disturbance can cause the surface tension of the solder to pull the solder back onto the pads. Sometimes that will even pull the whole chip straight. If there are still bridges I just glob solder over that area with my soldering iron and then suck it off with solder wick. Since the stuff I deal with is usually 0.6mm pitch TQFPs or connectors I avoid removing the thing at all costs as it’s much harder to just start again.
TLDR: Just try whatever you can think of on a practice board, the more experience you get the more intuitive it becomes. It’s more of an art than a science anyway :slight_smile:

Do you also use kapton to protect the parts around where you’re using hot air? And do you think it’s fine to use something like this ( vs a rework station?

Lots of flux, heat gun, 90% chance they just whip into place. If not, give them a gentle nudge. Don’t take them off the board.

Whatever method you use, test and practice it on a scrap assembly first.

The flip answer is get a better tool. It’s also the serious answer. If you are doing much SMT work, you need a hot air tool. Some heat guns and removal solder work for many situations, but a good hot air tool is the right answer for most - but not all cases.

For these SO8 parts, I’d reheat with whatever tool you have and nudge them under a light coating of flux. It’ll probably be the easiest on the board. If you restrict and focus the heat output of your heat gun without burning it up, I’d try and neck it down to 1/4" (~6mm) or so and see if you can get ti to reflow solder. Again, use a test board first.


I use one of the 858D clones, which are not much more from AliExpress. You need to have control over both temperature and airflow, as too much air through a small nozzle will blow small passives away and not enough air will take too long to melt the solder. I’ve never bothered with Kapton tape, as I can get away with a bit of discolouration on connectors, and everything else can handle the heat.

I’m going to order a hot air station, because I have 10 of these boards to get working, and they have many ways they could go wrong. Is this the kind of station you mean, and do you think this would be a reasonable one to get? If I order on aliexpress, I have to wait until September, which is why I looked if ebay resellers had ones that shipped sooner.

I’m looking at buying some kapton tape on McMaster. They have Kapton Masking Tape, Kapton Heat Transfer Tape, and Kapton ESD Safe Tape. I feel like all 3 of those are qualities I’d want–can I buy the cheapest, or should I go for the Heat Xfer or ESD tape for shielding?

The hot air tool you linked to has the blower in the handle. I think it has a lower top airflow rate than the ones with the blower or pump in the base. It’s probably fine, though.

As for kapton – the main use case in this situation is to form a barrier against the flow of hot air – I’d just get like a 1" or 2" wide strip from Amazon and save money unless you have a specific need for the nicer stuff from McMaster.

BTW, kapton is great for creating temporary solder mask when you want to solder in tight spaces and want to avoid bridging to nearby pins.

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Yep, very similar to mine. Plenty of airflow.