When is it Time to Switch from Manual Assembly to Automation?

When is it Time to Switch from Manual Assembly to Automation?
We are a new start-up assembling wireless sensors. All assembly is now manual. We are experiencing large reject rates due to hand soldering of components. The Assembly Brothers, Jim Hall and Phil Zarrow, address this situation and share their suggestions.
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Board Talk is presented by Phil Zarrow and Jim Hall of ITM Consulting.
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Phil Zarrow
Phil Zarrow
With over 35 years experience in PCB assembly, Phil is one of the leading experts in SMT process failure analysis. He has vast experience in SMT equipment, materials and processes.
Jim Hall
Jim Hall
A Lean Six-Sigma Master Blackbelt, Jim has a wealth of knowledge in soldering, thermal technology, equipment and process basics. He is a pioneer in the science of reflow.


And welcome to Board Talk. You are here with Jim Hall and Phil Zarrow of ITM Consulting on this forum known as the Assembly Brothers, Pick and Place. We are here to help you solve questions, problems, challenges in your surface mount and electronics assembly process.

Jim, we have an interesting one today. This is from L.U. We are a new start-up assembling wireless sensors. All assembly is now manual. We have no automation. We are at a point where we are experiencing large reject rates due to hand soldering of components. The PCB is a two-layer board but we are not using anything smaller than an 0805 package.

We are looking at whether we should get better soldering tools or upgrade to small prototype benchtop stencil printing, placement and reflow. We now assembly ten to fifteen board per day. Should we upgrade our soldering equipment or go for automation?

This is a classic experience. Hand assembly is what you typically do when you first start out. But hand assembly is not very repeatable. As you start to do higher and higher volumes, more boards, you start to see more defects because manual operations performed by humans are just not repeatable so you make mistakes.

So yes, the idea of going to automation is in my opinion absolute. The question is how much and when. My instinct would be to go for some sort of stencil printing to get the solder paste volumes down repeatably. Manual assembly, where you are applying your solder I can only imagine how much with a syringe or something. My feeling would be that getting the right amount of paste down at all the right locations would be the best first step.

That is just my opinion. Then going on to automating the placement of components and then finally to reflow soldering. What is your feeling Phil?

Well, it is funny it brings to mind when you are using manual operations, besides accuracy repeatability is always in question. We learned that back in through-hole days, it was challenging with the variables. But man, when you start doing surface mount, I am trying to envision old L.U. and his gang sitting there with that little syringe of solder paste and trying to position the 0805.

I totally agree with you Jim. There are two paths that I think we can take here. One is start off printing because getting the right solder volume and location is certainly paramount to the process. Then using something like a rework station for positioning the components and reflowing them. My inclination would be to cut to the chase.

Don’t fight a fact, deal with it. I would look into investing a little bit more in a good manual printer, at least to start off with. Even a good semi-automatic printer or even an automatic printer. There is a lot of stuff that is out there. Printers pretty much hold their worth, in terms of ability. Probably look into a small pick and place machine and a reflow oven.

Try not to skimp too much on the reflow oven too. There are some strange contraptions out there, where any propeller is passed off as convection. It is really not. I would seriously consider looking at used equipment.

A big thing that isn’t indicated here is that they said in terms of components we aren’t using anything smaller than an 0805 package. The very important questions is what kind of ICs are you having to assemble? Are you having to assembly area arrays? If you are, BGAs, CSPs, BTCs, how are you doing that?

I think you have to use some sort of hot air system. If that is true, that would drive my feeling, if you have to use area arrays, to getting to a reasonable convection reflow oven to give yourself some control over those. You don’t want to have a high defect rate on your area arrays because repairing them is so hard.

Even looking at putting components down, having some accuracy, even what L.U. is doing here 10 -15 boards a day. Obviously, they are small boards. I don’t know if he is talking about panels or total boards.

Right, there are a whole lot of details that we don’t know so we are just making some generalizations.

Like I said, I would lean towards biting the bullet and getting yourself a rudimentary line put in. Either finding inexpensive equipment, or don’t forget to look at used equipment, there are good bargains out there. The only thing that we caveat about used equipment is make sure the company that built it is still in business and that the stuff is still supported, both in terms of tooling and software.

Any other further thoughts on that, Jim?

Another factor is what are your growth expectations? How many boards are you going to be building in a month, six months, a year? At a certain point, full automation is going to be obviously justified.

Right, and another reason not to skimp on the type of equipment you are investing in. You don’t have to get a full-blown system here, but get decent quality stuff that you can live with for a long time. Then it is just a matter of personal taste.

To my point, start with a printer. If you only have limited money, get a reasonable printer, used or whatever. Get that process down and then move on to the next piece, whether it be placement or reflow as your economics allow you to.

Jump right in.

Of course, that is the best solution but whether that is financially practical, we don’t know.

This is Phil and Jim, just reminding you that however you are putting your board and putting your solder paste down, please don’t solder like my brother.

And don’t solder like my brother.


Generally in prototype assemblies 10 cards manually there is not much complication. However, when repeatability and reproducibility are required, it is best to automate the process, not only for quality, but also for time, volume, and mixture of the assemblies.
Roger Cespedes, Camtronics
With 18yrs experience in soldering parts for prototype, and production volume PCB's (primarily using 0603 and smaller parts), with <1% rejects due to poor soldering or parts placed wrong, I would argue the cheapest solution is new personal. Not new equipment. Especially when not using anything smaller than 0805.
Brian Martel
10-15 boards/day adds up to 200-300 boards/month. I'd also recommend they look into a contract manufacturer at those volumes. (Need to know how many variants there are...are all boards identical? Are there 2, 5 or 10 variants?) It doesn't take much in the way of rework or, worse yet, field failures, to justify paying the pros to do the assembly right the first time.
Alan Ritter, MtRitter.com, LLC
I would suggest considering a contract manufacturer. That way you are not assembling a system piecemeal and going through all the pain of changing your process every time you add a new device. Later, if warranted, buy a proper system with training and personnel to run it.
Paul Chyc, BI Inc.
Phil and Jim have a good plan here! But alarms went off when it was stated that the DPU was too high using the current manual process. The question is Why? Do the operators understand the requirements? Are there other issues such as part solderability or pad design issues leading to solder defects? If the defects that are being seen are wrong polarity, shifted parts from hand placement/soldering, etc, then, yes, you should definitely automate. But if you are seeing excessive/insufficient solder defects because the operators don't have a clue as to what is acceptable, or if you have solder defects due to unsolderable components, board pad design issues, etc, then you need to get those issues fixed. If you don't and you automate, you will be swamped with a lot more rework than you have now.
Theodore Kleever, Wallace Grommet and Bushing, Inc.

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