Raspberry Pi Cuts Product Returns By 50% By Changing Up Its Pin Soldering (arstechnica.com) 36
An anonymous reader quotes a report from Ars Technica: Raspberry Pi boards have a combination of surface-mount devices (SMDs) and through-hole bits. SMDs allow for far more tiny chips, resistors, and other bits to be attached to boards by their tiny pins, flat contacts, solder balls, or other connections. For those things that are bigger, or subject to rough forces like clumsy human hands, through-hole soldering is still required, with leads poked through a connective hole and solder applied to connect and join them securely. The Raspberry Pi board has a 40-pin GPIO header on it that needs through-hole soldering, along with bits like the Ethernet and USB ports. These require robust solder joints, which can't be done the same way as with SMT (surface-mount technology) tools. "In the early days of Raspberry Pi, these parts were inserted by hand, and later by robotic placement," writes Roger Thornton, director of applications for Raspberry Pi, in a blog post. The boards then had to go through a follow-up wave soldering step.
Now Pi boards have their tiny bits and bigger pieces soldered at the same time through an intrusive reflow soldering process undertaken with Raspberry Pi's UK manufacturing partner, Sony. After adjusting component placement, the solder stencil, and the connectors, the board makers could then place and secure all their components in the same stage. Intrusive reflow soldering this way involves putting solder paste on both the pads for SMD bits and into the through-hole pins. The through-hole parts are pushed onto the paste, and the whole board then goes into a reflow oven, where the solder paste melts, the connectors fall in more fully, and joints are formed for all the SMD and through-hole parts at once. You can watch the process up close in this mesmerizing video from Surface Mount Process.
Intrusive reflow soldering is not a brand-new process, but what it did for the Raspberry Pi is notable, according to Thornton. The company saw "a massive 50% reduction in product returns," and it sped up production by 15 percent by eliminating the break between the two soldering stages. By removing the distinct soldering bath from its production line, the company also reduced its carbon dioxide output by 43 tonnes per year (or 47.4 US tons).
Now Pi boards have their tiny bits and bigger pieces soldered at the same time through an intrusive reflow soldering process undertaken with Raspberry Pi's UK manufacturing partner, Sony. After adjusting component placement, the solder stencil, and the connectors, the board makers could then place and secure all their components in the same stage. Intrusive reflow soldering this way involves putting solder paste on both the pads for SMD bits and into the through-hole pins. The through-hole parts are pushed onto the paste, and the whole board then goes into a reflow oven, where the solder paste melts, the connectors fall in more fully, and joints are formed for all the SMD and through-hole parts at once. You can watch the process up close in this mesmerizing video from Surface Mount Process.
Intrusive reflow soldering is not a brand-new process, but what it did for the Raspberry Pi is notable, according to Thornton. The company saw "a massive 50% reduction in product returns," and it sped up production by 15 percent by eliminating the break between the two soldering stages. By removing the distinct soldering bath from its production line, the company also reduced its carbon dioxide output by 43 tonnes per year (or 47.4 US tons).
I assume the writer has never soldered anything. (Score:4, Insightful)
For those things that are bigger, or subject to rough forces like clumsy human hands, through-hole soldering is still required, with leads poked through a connective hole and solder applied to connect and join them securely.
It doesn't matter how big the joint is, you never use solder for structural reasons, especially for connectors. Solder is exceptionally poor when it comes to metal fatigue; hell, sometimes joints fail just from thermal cycling.
Re:I assume the writer has never soldered anything (Score:5, Informative)
Re:I assume the writer has never soldered anything (Score:5, Informative)
you never use solder for structural reasons
The billions of connectors and components in the world that have solder tabs mounted to PCB pads purely for structural purposes may very well disagree with you. Ever seen a PCB mount USB socket and wondered what those little wings were for? and why their data sheets state they have no electrical connection? Solder fundamentally has a structural purpose to go with its electrical one.
Re:I assume the writer has never soldered anything (Score:4, Interesting)
For those things that are bigger, or subject to rough forces like clumsy human hands, through-hole soldering is still required, with leads poked through a connective hole and solder applied to connect and join them securely.
It doesn't matter how big the joint is, you never use solder for structural reasons, especially for connectors. Solder is exceptionally poor when it comes to metal fatigue; hell, sometimes joints fail just from thermal cycling.
Your comment about thermal cycling is valid - but that applies primarily to connections which carry significant current.
Your mention of metal fatigue is true under certain circumstances. It concerns me specifically in this quote: "... the whole board then goes into a reflow oven, where the solder paste melts, the connectors fall in more fully, and joints are formed for all the SMD and through-hole parts at once".
The problem there is the "connectors fall in" bit. That means that there's a bigger-than-normal gap between the connector pin and the edges of the hole. In that case, there might be enough solder flex to fatigue the solder and cause the connections to fail eventually, through vibration and/or many connector mating cycles.
That said, using Raspberry Pi boards in high-vibration scenarios is probably fairly rare. It wouldn't surprise me to find some limitations on vibration somewhere deep in their specs.
Keep in mind that it's VERY common for through-hole connectors to be held ONLY by the pins, and has been common for a few decades. When it's done properly and the assemblies are used within spec, there's very rarely a problem. And even when extra mechanical stress is a consideration, one common solution is to add metal tabs, (sometimes with 'gripper' claws), which are - you guessed it - soldered into through-plated holes.
Now if you're talking about boards without through-plated holes, then you're absolutely correct - bolting the connector in place is a requirement for any reasonable level of reliability. But single-sided boards are pretty rare these days.
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That seems like some poetic license by the author. There's no reason you'd put the connector in part way and then hope it doesn't tip over or something while you're moving it to the oven.
I've never done pin in paste, but IIRC the recommendation is actually to decrease the size of the holes a bit because it's difficult to get enough paste on the board to fill large voids.
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In my experience, pads for NC-placed through-hole components have just enough clearance to prevent an interference fit at the tolerance limits. And I can envision the 'falling into the holes' scenario. I'm guessing that the pick-and-place machine stops short of pushing the component all the way down - it probably floats on the paste, and full insertion would squeeze too much of it out of the joint. So they need bigger holes to allow the part to settle properly, without the pins hanging up on the edges of th
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How do you think connectors are being attached to boards? Screws? Tape?
Pretty much every modern device uses solder to attach connectors to a board
Re: I assume the writer has never soldered anythi (Score:3)
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It doesn't matter how big the joint is, you never use solder for structural reasons,
Almost every single component is mechanically attached by solder as well as electrically attached. Some of the big ones sometimes get glue dots but mostly people rely on solder to mechanically attach.
So the answer is of course "it depends".
Re: I assume the writer has never soldered anythin (Score:2)
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All those connectors are typically held on by solder now. Something like a USB socket or barrel jack will usually have through hole pins and some through-board structural connectors too, but it's rare to see something that actually goes through and gets bent around anymore. And lots of connectors, including USB and barrel jacks, are purely surface mount.
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That's one of the reasons for using through hole components. You can absolutely get surface mount connectors, but the stress is all directly on the solder in that case. For through hole the pins in the holes take everything except straight up off the board.
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The stress being on the solder isn't the problem.
The issue with SMT is the stress is on the copper pad/trace, and these can just peel off without a real lot of effort.
With PTH the component is pinned in the hole by solder on either side of the board so it can't move.
Missing video (Score:5, Informative)
"You can watch the process up close in this mesmerizing video from Surface Mount Process." has no video link. It's https://www.youtube.com/watch?... [youtube.com]
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No, they just know their audience is made up of Slashdot ACs and use accordingly complex words.
Re:Amateurs figure out basic manufacturing ... (Score:5, Insightful)
What the fuck are you talking about? The Pis work just fine and have for over a decade. Making a small change to manufacturing to improve robustness using a relatively newly developed technique in the electronics world (intrusive reflow soldering has really only been a thing the past 5 years) doesn't make someone incompetent, it makes them precisely the opposite.
There is a fuck here though, an ignorant one, a worthless one whose only contribution to society is to ignorantly shit on the works of others. I'm talking about you.
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There's a few people who absolutely love to shit on the Raspberry pi because they think it makes them sonud smart, having this special piece of knowledge that the hoi polloi lack.
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Indeed. These are also universally people that have no clue what competent hardware design looks like. Pathetic.
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Beware of statistics. I could release 100000 widgets and have to do a warranty replacement on 2. If I do something that reduces that to 1 that's a 50% reduction. We have no idea if the number is actually impressive or not. We don't have enough information to judge as to whether the issue was any significant problem in the first place.
The story we can latch onto here is the reduction in time to assembly (usually means reduction in cost as well).
Wave soldering, Texas Instruments 1980 (Score:2)
The amazing part to me (Score:3)
Re: The amazing part to me (Score:2)
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Re: The amazing part to me (Score:3)
One minor point, the manufacturing entity is Raspberry Pi Ltd (a for-profit entity) and not the foundation which as far as Iâ(TM)m aware still focuses on the education side
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There's a big difference between a bare board like a Rasberry Pi, which is made entirely by machines, and something like a smartphone, which usually requires some hand assembly.
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There is surprisingly little hand operation in assembling a phone.
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Sure. And the little bit that there is is expensive, and done in cheap labour countries so that it's not super expensive.
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Consider something like a $1000 iPhone. How many actual hours of human labor do you suppose go in assembling each phone?
I'd say not even one. Pay that one at $40 and you are talking about 4%. Of course, a more common U.S. hourly for that is more like $20.
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It has always been possible, it's just that western investors and CXOs expect yacht money just for getting out of bed.