If you use an oven you have to pay more attention to storage of certain of the parts- humidity and all that rot.
As well as doing prototypes and small production they're good for reviving things like 30" monitor boards and HP printer controllers that fail due to RoHS solder. That alone will pay for the small Chinese oven, though others have reported better results from larger ones ($2K-ish, IIRC).
Best regards,
--sp
I just can't see using a toaster oven. It reeks of amateurism. (like buying a $99 workstation! "How committed to this endeavor
*are* you, really??" :> )Surely not a *single* board? Or, is that just all you needed to bake at that time?
I think if you are a business involved in manufacturing boards, you use a different set of criteria.
Similarly, if you are a hobbyist that wants to reflow *a* processor on a motherboard, game console, etc.
I'm somewhere in the middle. I don't want to save pennies at the expense of hours (or *scrap*!). OTOH, I don't want to be tied to a piece of kit that I then need to "feed, regularly" to justify the expense! Nor do I want to discover 6 mos or a year down the road that the fab was "marginal" and I've now got bits of kit failing that need AVOIDABLE rework. Or, that the *design* had a flaw that manifested after a lengthy usage period and now I have to refab those affected boards.
If my only choice was a unit like that, I'd have to redesign one of my devices -- the boards are 2x12. So, I could fit *one* (?) at a time in that oven (diagonally). That's not a deal-breaker.
No idea how old your eyes, hands, etc. are but I have found I am rapidly losing the patience and abilities for much of this fine work. I've tried to achieve a balance in my designs between using insanely fine pitched parts (to get the designs to fit in the physical space available) vs. exploiting the back sides of boards (as well as additional boards) to gain the real estate that will support "bigger parts".
It also means the current designs can probably be produced by "skilled" hobbyists -- as long as they are careful!
Let someone *else* rehash the designs later if they want to commercialize them to make them more economical/manufacturable!
Don, no personal experience but after reading this thread I did some Googling for reflow ovens, and looked at a few manufacturers products. It seems that they either offer ovens that can handle one board in the 8-10 x
10-12" range, for a few thousand $$ (under $5k even with a loading tray and a cooling tray so you can have three in process at once), or they offer the size you want but now they are $10-15k+ with lots of automation. Have you looked at general purpose programmable ovens from someone like BlueM? Maybe they have something that will work. Industrial quality, but you will have to "qualify" the uniformity and accuracy yourself.----- Regards, Carl Ijames
Hi Tim,
If my only choice was a unit like that, I'd have to redesign one of my devices -- the boards are 2x12. So, I could fit *one* (?) at a time in that oven (diagonally). That's not a deal-breaker.
No idea how old your eyes, hands, etc. are but I have found I am rapidly losing the patience and abilities for much of this fine work. I've tried to achieve a balance in my designs between using insanely fine pitched parts (to get the designs to fit in the physical space available) vs. exploiting the back sides of boards (as well as additional boards) to gain the real estate that will support "bigger parts".
It also means the current designs can probably be produced by "skilled" hobbyists -- as long as they are careful!
Let someone *else* rehash the designs later if they want to commercialize them to make them more economical/manufacturable!
No, the total series was IIRC 60, but each board needed some afterwork, troug-hole soldering, and then testing, so why not put them in one at a time while I was doing the other work. The middle area of the oven seemed to work more reliable.
I do produce boards, but in very limited quatity (10's/year rather than
100's)Wouter
Ah! Different work process than me. I would, instead, have stacked the reflowed boards and did the secondary processing a day, week, etc. later. So that I am only focused on one activity at a time (less chance of forgetting some little detail -- especially on boards that are "made once", not repeatedly).
[The last cheesecake I made I realized I had failed to mix the *sugar* (gack!) into the filling -- because I was trying to prepare dinner at the same time! :< Thankfully, caught it 10 seconds after placing it in the oven so I was able to remove the filling, mix in the sugar, reassemble and restart the process! 100's)I'll build a few hundred, total, (though different designs) and scrap the oven afterwards. Nor will they all be built at the same time. E.g., build one/couple of each design, as required (to characterize them as well as debug the software, etc.). Then, once satisfied, buy the balance of the components and fab the remainder. If a design change necessitates scrapping some *bare* PCB's... ... much preferred to scrapping a bunch of fabbed boards that "won't work" along with all the components thereon!
Yes. Of course, used kit comes with a lower price tag. As I have a very limited life planned for the equipment, I'm not sure it justifies "buying new" at those prices.
I am starting to rethink Hamilton's original suggestion. If the oven has relatively even temperature distribution (recirculating fan), then adding "controls" may be the easiest option.
[ Add a face/bypass air-handler to the mess! ;-) ]But, I've not heard a justification of Ir over other heating methods...
Essentially, you're just heating (cooling) some devices to a specific temperature at a specific time. Assuming the enclosure can sustain the temperatures and *change* them at least as fast as required (undoubtedly, speed being driven mainly by wanting to minimize the cycle time; less so for its effect on the components, etc.), then anything that could do this should be a viable option.
Having said that, I wouldn't even consider baking boards in the ("cone 10") kiln (~1300C)! Sort of like hunting grasshoppers with a cannon... (it's hard enough melting pounds of lead for the neighbor! :> )
I may look at some medical surplus equipment, as well.
Yes cleaning stencil can be time consumiong.
I have not paid $100 for a stencil or even a stencil pair, I think the MOST I have paid was about $75 for a pair of stencils 250 micron stainless steel for both sides of a board 350 x 250mm.
Often PCB houses I deal with do free stencils with prototype qty boards so no brainer on getting stencil even if it is 400 micron not so good for below 0.5mm pitch.
My largest quantity I have used stencils or even small toaster oven kit from Beta layout is 12, normal quantity is 2 (never do 1 always have a spare). That oven does 290 x 290 mm approx boards. Not wonderful but does the job had to replace elements (about $20 including shipping). The kit cost about $300 at the time and has more than paid for itself.
Looked at T-962 series an would only consider the ones on Ebay that have been OEMed to have different controller in for better control and profiles. Small outfit in UK who retrofit them or sell kit to modify them.
....
Well I do the layout and doing prototype build run on small boards in small oven saves time and hassle of getting kits for a fab shop or paying their costs for proto assembly. That way I know the right parts are used. Especially as often I am dealing with samples of chips not available in less than tray quantities. Dont get me on the huge box to air freioght 6 samples from Taiwan the chip was QFN 6mm x 6mm, the freighting box was about 750mm x 300mm x 250mm.
In some cases I have done one off systems including spares then got repeat orders because production was ramped up, so having known stencils helped.
The ones I'm citing at the moment require parts that are designed for the cell phone market and ONLY come in challenging packages, and need to fit into model airplanes, to boot.
When stuffing boards these days, my old eyeballs are glued to an assembly microscope.
Ditto. (I've been looking for an X-Y staging to mount boards in but haven't "broken into a sweat", yet, to do that! It would make placing parts *and* paste much easier -- as the "focus" of your activities would not change!)
I need to come up with a solution that hobbyists have a (reasonable) chance of assembling. Silly to design an open product (that is not producible "one off") that requires you to *buy* it from someone else!
If someone wants to enhance the manufacturability -- and, in doing so, "lock" customers into a purchase relationship -- that should be up to them (all the while knowing that someone *else* can offer similar enhancements and undercut their efforts!)
We are talking about one batch of boards in your "larger" machine that holds a square foot of boards, right? You don't have a square foot of space to hold them in while you are in process? Inside the oven is the only place you have a square foot?
I'm not following. Get your boards ready to bake. Bake each of the several batches. THEN test and rework.
I don't mean to be rude, but I'm not picturing the problem. You are talking about an oven that fits in your house or some space in the garage. Look at it this way. If your oven is large enough to hold all the boards at once, but you don't have room to hold all the boards, where will you put the oven???
Ok, if this makes sense to you fine. I don't see the problem. I see exactly the same process, but the oven requires two, three or more batches that only take you an extra few minutes each. I expect the added cost of the larger oven will be large vs. a small added time for the multiple oven runs.
If you don't have space for the boards "somewhere else", where do you find the room for the larger oven? Are you planning on buying an oven made from a TARDIS, bigger on the inside than out?
What does that have to do with controls?
Ok, enjoy.
Uh, you mean consistent no matter the result as in "oops"?
So I guess you would never use a dishwasher to clean the boards? That has to seem very amateurish too, no? Ask JL.
Can you define "pennies"?
How are you going to select an oven based on this criterion, "avoidable rework"? Do ovens come with an "avoidable rework" index?
Everything you buy will have risk. Spend too little (or more than enough, but on the wrong unit) and you have problems. Spend too much and you just spend too much with little improvement in utility.
It's not just a cost issue. You get to see if the artwork, silkscreen, mask, etc. *really* give you a manufacturable board (especially if you also want hobbyists to be able to fab them -- at their own risk). You might not realize (in layout) that the placement of a silkscreen legend makes it ambiguous whether component X or Y fits into a particular location. Or, that there is some mechanical interference that you didn't foresee.
Yeah, a fab house *can* spot these things. And, hopefully, convey ALL of them to you. Or not. If it's a local shop, perhaps you can drop in on them when you're in that part of town, etc.
IME (building prototypes for clients), it was *so* much easier to just build the first unit myself and see, first-hand, what the potential problems were likely to be. Of course, a different set of eyes, hands and tools might turn up *other* problems (I've had problems with pick-and-place in the past... hard for me to verify on my own :< )
I will be building some number of "first samples" -- true prototypes to actually verify the functionality of the design, software, etc. Easier to prototype in foil -- especially with the devices that I am using and some of the packaging constraints.
If any of the designs/layouts prove to be faulty, I can scrap the remaining boards (of that particular design); turn the crank, again; and repeat with the newly revised design/layout.
Once everything are proven "acceptable" (no rework or just minor rework required... some of which may be easier to do on *bare* boards), I will proceed to make the rest of the prototype *run* for the prototype *system* (quantity one).
[Though this will tend to be a staggered effort as the entire system won't be done at a single point in time with *just* the "first samples". Instead, I may finish producing *all* of the "design #6" boards before I build the *second* "design #2" board. E.g., the highest quantity design will be fabbed in many stages as I won't need *all* of them until the very last moment.]I.e., I *know* how many of each design/layout I will eventually be building -- *I* am the customer! If I find someone who wants to produce more (for themselves or for sale), then I could hand off to them any tools I have acquired/created in the process.
Or, not. (e.g., they might want to make changes to the design going forward)
No not yet. Many times what I am building is on a tight shipping schedule. If the oven broke I'd be back to the hot air gun and there is now way I would make the schedule. So I bought a spare.
I have some ESD stackable trays I use. My sequence is I paste maybe
8 or 10 boards and put them in the trays. I have a little "box" that keeps them about 65F to help with the paste life. I stuff one and into the oven. While it bakes I start stuffing another, etc. Or depending on the board I might stuff them all. The stack trays really help.The trick is to balance your paste life with how long it takes to stuff and bake.
Trying to do something like an oven rack is tricky and would be almost impossible with a double sided board. You have to be able to control the heat on the "other" side. Surface tension only goes so far competing with gravity.
I understand what you want to do, like baking loaves of bread. Not that easy keeping the temps right. Take a look at your paste temp profile. You need to ramp to, say 220C and then make that bump to 240C in 15-30 seconds depending on your profile. Then ideally need to bring that back down in 15-30 seconds.
Maybe. But I dont think it's worth the trouble. My stencils are normally 5mil stainless. The way I understand it (and could be wrong) you also have to post process the cut to clean it up so the release is better. I just order them and the stencil guys tell me the best choice. I have no desire to become a stencil expert.
OK. So, in your opinion, it isn't the sort of device that just falls apart when you peel the chinese cardboard (box) off of it!
So your boards tend to be small-ish?
I was planning on using the drawer from the oven to "accumulate" the stuffed boards. So, I need space for the oven and enough elbow room to stuff *one* board (at a time).
I am hoping to decouple the two -- by not caring how long the bake cycle takes as I'm "done" stuffing before it *started* (so I don't have to drop what I am working on to attend to the oven's call).
"Oven rack" meaning *toaster* oven rack? I.e., have you had problems doing double-sided in your kit? (do one side at a time -- heatsinking the inactive side?)
As I mentioned elsewhere, external air handler would be an ideal way of doing this! Change air temperature nearly *instantly*! Of course, more wasteful of power and you'd need a place to exhaust all that process air...
Ditto. I don't want to be a reflow expert, either! Rather, like every other skillset, learn just what I need to do what I want and avoid the annoying details that address "the last 2%".
(sigh) Perhaps I should start calling in some favors. After all, folks forget they owe you if you leave them "banked" too long! ;-) And, it would be really annoying to discover folks retiring out of positions where they can be of help!
I guess I will have to deal with the dreaded telephone this weekend...
Thanks for your comments!
--don
P.S. Any suggestions re: the T-962C I mentioned? "A bigger version of the A?" Or, does the design not scale well??
On Fri, 05 Sep 2014 23:05:12 -0500, Joe Chisolm Gave us:
Paste life includes all time until the reflow run itself.
I am sure lead free has longer open air time than the old stuff.
The old stuff made way better solder joint IMO though.
In article , snipped-for-privacy@is.not.me.com says... ....
Have a look at these folks and their description of differences
In their view it is underpowered has the same heater and fans as T-962A trying to heat a larger volume.
for something you're only building one of stainless seems a needless expense, polycarbonate or paper might be better priced and sufficiently durable.
Perhaps but lead-free has a very tight temperature profile. The difference in temperature between the solder melting and the parts wilting is very small and short (time). The PPoE had a lot of trouble with their lead-free solder process in a four-stage oven. LEDs, aluminum capacitors, inductors, and QFNs were the biggest problems. Balancing the profile between the needs of all of these was like balancing a pencil on its point. They bought a used multi-stage oven (eight or eleven, can't remember) in 2010, when manufacturing equipment could be had for pennies on the dollar, and the problems went away.
Far harder to get the same quality, that's certain. Harder to inspect, too.
Have something to add? Share your thoughts — no account required.
Ask the community — no account required