In any company engaged in the development of electronics in Russia, two questions are regularly raised that lead to hot holivars: how to solder prototypes and where to start mass production. The answer to each question, in fact, boils down to a choice between outsourcing or in-house production. The article describes the personal experience of setting up a laboratory for prototyping single copies and small-scale production of electronics of our own design. Perhaps someone will find it useful when building their own candle factory.
To make the article as practical as possible, it will contain links to suppliers of equipment that we use. Don’t think of it as an advertisement.
Prototyping unit boards during development
We started with a typical kit: a soldering iron plus a hair dryer. The paste was applied to the board with a manual dispenser, electronic components were placed with tweezers, after which the entire board was warmed up with a hairdryer. The result was extremely unstable: every 2nd – 3rd board turned out to be inoperative due to: sticky, non-soldered and overheated microcircuits. This was caused by two problems:
manual dispensing of solder paste had an extremely low repeatability (due to human factors). The stencil could not be used due to the frequent use of microcircuits with a pitch of 0.4-0.5 mm and smd components in cases 0402 and 0201.
heating the board with a hairdryer led to the fact that before the pads of the microcircuits were heated to the desired temperature (the temperature of reflow of the solder), the microcircuit itself was heated several tens of degrees above this very temperature of reflow.
As a result, the problem was solved by purchasing the following equipment:
After that, the assembly of prototypes was reduced to the following sequence:
the compressor supplies 2 atm to the dispenser;
the dispenser applies solder paste to the contact pads;
tweezers (manually) place SMD-small things, and vacuum tweezers as part of the dispenser place microcircuits (QFN and BGA including). The microscope is used during the placement.
after that, the board with the applied solder paste and placed components is transferred to the board heater;
a temperature sensor is installed on the board;
on the PC to which the temperature controller is connected, the graphical utility for editing the thermal profile is launched from which the heating and cooling process of the board heater is started according to the specified thermal profile;
As a result, the number of cases of non-drip / sticky / overheating was reduced by orders of magnitude. Accordingly, the repeatability has increased. We no longer wonder, holding our breath, whether the soldered board will work or not.
Achieved technological standards for installation:
SMD small things up to 0201;
QFN / LQFP microcircuits with pitch up to 0.4 mm;
BGA chips with pitch up to 0.8 mm;
An example of applying paste on 0201 footprints and a QFN-microcircuit with a pitch of 0.5mm (bottom in the photo):
Accounting and storage of electronic components
In addition to the installation itself, in the development of electronics and its prototyping, the issue of accounting and storage of electronic components is quite puzzling. For prototyping, as a rule, components are purchased in quantities of 2-10-100 pieces, which come in tape cuttings and in bags. If you are working on the development of several devices, then the nomenclature of components required for installation can reach hundreds of items. And if you have not organized accounting and storage of components, then the installation of a prototype device boils down to the following unsightly picture: the installer is lined with boxes containing dozens of bags with various components, and when placing the components on the board, the installer goes through the bags over and over again in search of the desired component … You shouldn’t even stutter about labor productivity with this approach.
It is necessary to introduce accounting and storage of components so that at any given time you know whether you have such and such a component, in what quantity (at least approximately) and where to get it. The less time it takes to find a component, the better.
We started accounting with an excel file. After that, we wrote down a simple server application. Its web interface looks like this:
In fact, a simple plate with the ability to simultaneously search for each field. There are two advantages over an excel file:
search simultaneously in several fields. For example, you need to find some 0.1uf capacitor in the 0402 package with a temperature of -40;
accessibility from any PC / smartphone; It can be useful when it becomes necessary to find out the presence of a component, and you are not in the office;
On the back of the usual Postgresql with two or three tables. It is written on the knee in a couple of days. If anyone is interested, I’ll post our part on github.
How to store components? The first thing that comes to mind is cassette recorders:
But they are not very convenient for SMD-loose. Much higher storage density is achieved if the SMD bulk is scattered into empty SMD books:
With due discipline, if all parcels with components are immediately put into books and cassette holders, and immediately entered into the database, then wake you up at night you can tell if you have stm32f103cbt6 in stock and how many are left.
Feel free to experiment with your placement. For example like this:
And the last thing: when developing, do not skimp on the hood. Breathing in formaldehyde is not good for your health. The cheapest local hood costs in the range of 1-2 wages of an installer.
Small batch production
The most common opinion about where to make electronics cheaper is in China. But to be more precise, mass production is cheap there: thousands and tens of thousands of products. If we are talking about tens to hundreds of devices, then the costs associated with logistics and customs clearance (importing finished devices is more expensive than components) become noticeable and the obviousness of the answer to the question decreases. For example, the popular low-fire jlcpcb.com proposes such rates… At first glance, everything is very beautiful, $ 0.0015 per soldering point, but if you dig deeper, it turns out that all their components are divided into two groups: “ordinary” and “not ordinary”. The conventional ones are already loaded into the feeders on the assembly lines and their installation really costs those very fractions of a cent. But if your board has “non-conventional” components that need to be manually charged into the feeder, then each such operation will cost you $ 3 per component. When placing an order, you may also notice that the prices for components are noticeably higher than if you purchased them from “their” warehouse – lcsc.com… You can look for another manufacturing company, but you are unlikely to find something cheaper, especially if you need to solder 10-100 boards.
As a result, we ordered part-wired boards in China for a long time. The missing components were soldered by themselves. And then a dilemma arose: either to solder and spend time on this, or to order a small-scale installation on outsourcing, which was either expensive (SMD installation companies), or there were questions about quality (a blind-eyed grandfather with a hairdryer).
As a result, for many years this problem was hanging as an open gestalt. I was constantly looking at budget (read Chinese) SMD installers. The choice was very limited, since we needed at least 0402 accuracy and an integrated automatic paste dispenser was highly desirable. At one time, almost decided to buy VP2800HP… But at the very last moment they stumbled upon hard-hitting review… In addition to this, I constantly came across reviews on the forums that the Chinese, having received money for the machine, sharply lost interest in you and people had questions from those. support.
As a result, we acquired a machine only when a domestic machine appeared. Saturn-Atlas, plugged in the belt in terms of price / quality ratio and China, and many western expensive machines, such as Mechatronika M10V…
The characteristics declared by Saturn (up to 0201 and QFN-0.4mm) seemed unrealistic at such a cost (990 rubles with a built-in solder paste dispenser). But the need for a machine tool was already so ripe that they nevertheless made an advance (at their own peril and risk) for the machine and began to wait for delivery. After 4 months, it was delivered packed:
Two weeks later, a commissioning engineer arrived, 4 days of assembling the machine and learning how to work on it got such a handsome man at work:
Much to the relief, the machine meets all the declared characteristics: 0201 and QFN-0.4mm (including the application of solder paste!):
Another feature is the cost of the feeder – 4.5k rubles. Many other manufacturers of SMD component installers have a much higher cost of feeders. As a result, a complete set of feeders sometimes costs as much as the machine itself. As a result, a machine with a metering unit, VAT included, with commissioning, with 16 feeders cost 1.1 million. It remains to buy the remaining ~ 40 feeders.