Often one is with the self-'s building of an electronic device before the selection into which housing the new project to be inserted is. Different manufacturers offer finished casings from plastic, aluminum and steel sheet in catalogs. One can manufacture self-'s building from these materials also, but in particular the RF technically interesting sheet metal casings requires an elevated workshop equipment.

A modern composite material is the base material for printed circuit board production. By the copper lamination one obtains a good screen, which have to do for devices with RF are always needed. The fabric from glass and epoxy resin is mechanically stably, electrical isolating and can easily be processed.

For the author of these lines the production of casings from base material was long time almost the only way with the self-'s building of radios. The fig. (1) shows a set of devices from base material, which developed by DL2LUX. On the experiences gained thereby is to be reported in the following.

Hack-saw, leaves-saw, drill press or electric scew driver, files, under it a set of keyfiles, drill 0.5 mm to 10 mm, step drills, soldering irons, ruler, right angle and pencil are the basic equipment for the self-'s building of a casing from base material. These implements find in a brief case workstation. Thus it was to be too structured me also during my time as Y26AG in the student hostel possible some devices. With this equipment I built most casings. The work relieved by a small circular saw, a column-type drilling machine the milling tools to surely take up can, an adjustable pitch diameter saw or a dekupier-saw.

With the base material one can differentiate always between two sorts: Laminated paper and glass laminated fabric. There are the types FR-2 to FR-4 of different manufacturers. Materials with high order (teflon substrates (PTFE), ceramic(s)-filled, glass fabric-reinforced polymer base material) are for casings too unfortunate and separate generally also from cost reasons.

FR-2 &# copper-shielded laminated paper on phenolic resin base

FR-3 &# copper-shielded laminated paper on epoxy resin base

FR-4 &# copper-shielded glass laminated fabric on epoxy resin base

CEM-1 &# copper-shielded, epoxy resin-impregnated soda cellulose paper

CEM-3 copper-shielded, epoxy resin-impregnated fiber glass

For the building of casings FR-4 is best suitable. It is the printed circuit board material, which applies to most in the building of computers, in the communicationses, in the industry -, aircraft and motorcar electronics as well as in the measuring and automatic control. It has very good electrical and mechanical values, dimensional stability and surface quality. In addition, the laminated papers are suitable well.

All these materials are bilaterally coated manufactured in different thicknesses, on one side and, whereby also the thickness of the copper varies. Default values are here 35 m m and 70 mm.

For the building of casings the substrate should be at least 1.5 mm thick, better is 2 mm.

Always one can use on one side or bilaterally coated material. One should know that on one side coated material is inclined always somewhat to it, itself too forgiven. By the different coefficients of expansion of the copper and the substrate that is practically pre-programmed. Qualitatively high-quality material adjusts this effect well. Cheap material, from which the industry separates and which emerges as special offer with the dealer, one should under this criterion critically regard.

With the building of casings with a dimension more largely than 20 cm this begins to play a role.

In addition, bilaterally shielded material adjusts this effect automatically, is somewhat more expensive.

The seams should be coated cleaned and with fluxing agent (rosin, soldering honey). For cleaning the printed circuit board are suitable an eraser, a quite fine sandpaper or a combination of both: the so-called "Polyblock" (Conrad stock NR. 52 94 19-66). A glass fiber brush carries out here also a good factory. It must be guaranteed that the seam is bright and grease-free.

When soldering one must be over it in the clear one that the large Cu surfaces take up much warmth, passes itself on and to the environment to deliver, even if the layer is thick 35mm. With soldering irons under 30 Watts one should not begin better.

I always operate with two soldering irons. One with 40 Watts and 100 Watts. With the smaller I manufacture 2 solder tacks with relatively few tin per edge. In this status I have to correct the possibility the angle between both disks still relatively easily. With the large soldering iron I pull then the " seam ". In the standard case two printed circuit boards are to be interconnected right-angled. As support I use large elbow of smallcross-hatched paper. So I can exactly align the angle of 90 degrees. Stop! I must to it-give a few degree, because the seam pulls the disks together with solidifying the tin solder. In the fig. (2) the problems is represented, which also each welder knows. The liquid tin solder moistens both copper surfaces and solidifies, in order to connect the two boards (desired effect). With solidifying the tin pulls together. Thus it comes to a traction power between the boards, which is largest at the edge of the seam and which angle between both disks reduces (unwanted effect).

As rectangular framework a planned casing from base material can become so fast a concave thing. See for this Fig. (3). Target of our activity should be a orthogonale casing and no "Hundertwasser" - casings!

One can also evade to the unwanted effect, by interconnecting the boards only at two points. Strength the affecting the boards is smaller in this case than 10 to 20 cm long a soldering seam. Then the seam is closed from the inside with adhesive on epoxy resin base. That is then also waterproof, but not 100 % RF.

Even if the most diverse geometrical forms are possible: The simplest solution is some casings from two u profiles to form Fig. (4). The lower u section consists of the baseplate, the front plate and the rear wall. At the pages two strips are attached, which serve the stabilization and which serve the attachment of the cover. The upper u section serves as cover and consists of cover plate and two side parts. With larger casings a bracing is recommended here.

A module casing with chassis is more complicated after Fig. (5)-those control elements, which become sockets and the printed circuit board in the chassis installed. The Leiterplatte(n) in the chassis is accessible from both sides, which for the alignment of advantage is.

Small casings for a test pin, a probe, a dipper, a quartz tester and such a thing are not topic. Also casings for small QRP Transceiver are relatively unproblematic. They can be soldered together in the simplest case from six boards to a right parallelepiped. Casings, whose surface area is larger than the paper format A5, become more difficult and/or if they must carry modules of large mass (transformers). Concretely: If I access and raise the casing at a page, then it may not become bent, even if e.g. the trafo at the other end is. Here the mechanical stability out individual boards of a soldered together casing their boundaries and one achieve must of other aids avail itself, which are there:

(1) base material doubly take

(2) bracings from base material or other material (metal, wood, plastic)

(3) casting resin

(4) combinations of point (1) to (3)

If two boards are stuck one on the other and/or bolts, then stability improves against bending substantially. The areal moment of inertia, a measure for the resistance against buckling and torsion multiplies thereby opposite a twice as thick board. To arrive for the basic or mounting plate a simple means at higher stability.

Fig. (6) interior view of a casing for a power supply with heavy trafo. The base plate is approx. 1 cm thickly.

Fig. (7) view power supply from the inside. A casing from printed circuit board material without strengthened base plate could not carry such trafo. One detects also the iron wire wound around the turning reeling instruments.

A diagonal bracing out double shielded base material increases likewise the firmness against buckling and twist.

The firmness is increased by the use of casting resin likewise. Several layers must be laminated, i.e. a wadding (glass fiber mats) is presented and laid on then to casting resin in several layers. The more layers to be laminated the more stably the crate! A layer of 1 mm stabilizes a normally equipped casing substantially, a 5 mm thick layer can already a trafo carry.

The largest casing built by me from base material (Fig. 9) was in Console casing for a home computer of the type Z1013 (GDR 1986) and had the dimensions of 40 cm broad, 35 cm depth and height of 5 cm (in front) 15 cm (in the back). It contained the printed circuit board for the computer, the power supply including trafo and the keyboard. Over necessary mechanical stability to obtain was glued on to about 1 cm strong plywood disk on the baseplate from base material one and embedded in casting resin (Epilox). The baseplate was thereby approx. 1.5 cm thickly. If I should come once into the embarrassment a tube output stage build, then I would access on these experiences constructing also again to the base material, if no suitable finished casing is.

Fig. (9) a computer casing from base material. The soil became by a plywood disk, which was cast in in casting resin strengthened.

Surely one can bore a hole for an LED into a casing already finished subsequently. Always the most drillings and in particular recesses should be implemented in the front or rear side, before the base material is soldered together.

Already with the selection of the switches, tracers, sockets, light emitter diodes, displays, potentiometers and loudspeakers one should consider: Approximately makes itself ever easier than three-angularly, rectangular or polygonally. A drilling for a switch with e.g. 10 mm schaftdurchmesser is manufactured in fewer than one minute. For a rectangular recess for another switch of 8 mm x 12 mm one needs oneself with the leaves saw already somewhat longer and one can more easily thereby verhauen. The drilling looks always approximately, whether a rectangle looks rectangular in each case also, dares I in this connection to doubt. Over 4 holes of 1 mm in diameter will saw a rectangle out bored, contrived into the leaves saw and then a cut from hole made hole. In addition, one can bore many holes in small distance, in order to have when operating the leaves saw a better orientation. The use of a universal printed circuit board as drilling template is here very helpful.

One manufactures the break-throughs or the hole sample for a loudspeaker at the best one with your drilling template. In addition a ventilation cover has itself, like it to Ventilation of holzwaenden used is worked. After one bored two holes, one screws the template provisionally on the base material and can now in all peace to the remaining ninety-six make itself.

With the purchase of such an instrument usually a drilling template is attached to the packing, which one should use for marking out. With the installation by measuring instruments it is to be paid attention to the fact whether these are intended for the assembly in iron or Nichteisenfrontplatten. The linearity of the display is influenced of it.

If one has available turning reeling instruments, which is intended for the installation in 2mm Fe, then one can manage with it a strong iron wire behind the front plate around the casing of the instrument winds themselves and from the rear against the front plate sticks. See Fig. (7). An attempt showed that iron wire of 1mm diameter the linearity of the display improved two turns substantially.

If one has the ambition to operate science then one should naturally select the instrument suitably the front plate material. With simple indicator instruments one does not need to think over this problem.

If a part of a case soldered together from base material is to be dismantled without destruction, then first tin solder must being removed as much as possible. In addition one can itself a Entloetpumpe, Entloetlitze or also serve of the force of gravity of the earth. In the latter case one can warm up the surfaces carefully from down with a hotair gun and let then the tin under easy knocking drip off. One well soldered seam will always keep something tin however by the adhesion. Here is suitable a razor-blade, which is shifted into the gap and with the one separation of the two copper surfaces be obtained can. So one can replace an old front plate by a new.

The yellow-brown colour of the base material does not address reliably everyone, but always a base material casing does not need colour. A larger device should be arranged also coloured. In addition one uses the practical color spray doses, which are meant for the autorepair and find also much resemblance with the Graffiti - artists.

One achieves professional appearance by the use of abrasion letters. After the inscription was applied, it must be sealed with colorless lacquer. One must pay attention to the compatibility of the two used lacquers. Colorless lacquer with cellulose nitrate diluent attacks also the abrasion letters and resolves it. One can use it nevertheless, if he is up-sprayed carefully in thin layers. Employ attempts best beforehand on a test specimen. If colorless cellulose nitrate lacquer with the brush is laid on, one wipes equal inscription also down!

A further possibility of the inscription is the use of an inscription device. These devices produce self adhesive, transparent or colored label strips of different character fonts and sizes. For the hobby workshop the acquisition of such a device is quite expensive, is situated the price nevertheless in the order of magnitude of a QRP Transceiverbausatzes. But some a OM can use such a device on loan.

Also self adhesive foils, e.g. file label leave themselves with a laser printer to mark. In addition one uses a character program or in the simplest case a text processing. Then this label on the front plate or the rear side can be stuck.

Outside at the device appropriate sections can be fastened with cheese head screws (M2, M3, M4). The appropriate nuts/mothers are because of the inside. With closing cover one does not have a possibility these nuts/mothers to hold. Here nuts/mothers from brass worked, that are soldered from the inside to the drilling. In addition the drilling is tinned to the inside, fastened and soldered then the nut/mother with a screw. One removes the screw immediately after soldering, if the material is still warm. With the fact one avoids that the fluxing agent sticks rigidly and the threads together.

Sheet metal casings could serve the advantage also as cooling radiator for semiconductors. With one from base material one can make do to screw an aluminum plate from the outside to the rear wall. If one uses the entire rear wall, then a relatively large surface is at the disposal on that the semiconductors (depending upon design) by a recess to be from the outside or from the inside attached can and to an aluminum casing in nothing is inferior. See Fig. (8).

Fig. (8) shows different possibilities warmth over the rear wall to exhaust. With the device down became on the module (chassis) over the entire spread a 3 mm strong aluminum plate screwed, which carries the transistors. Used with the device over it a prefabricated cooling section, above is sufficient a smaller piece of aluminum sheet metal.

Tip: During filings processing of aluminum with drill press, milling cutter or hack-saw a few drop white spirits (C₂H₅OH) to the interface or the drilling helps to avoid around lubricating the material.

It was pointed out, how one can manufacture casings for various devices of a radio amateur with a minimal gear at tool using of the base material. Economically regarded this version does not cut off also at all so badly, if one considers that one receives a custom-made casing in this way. If one finds a suitable case in the trade at a reasonable price, it is to be fallen back surely more easily to it. If then however the self's building in the foreground is (with the members of the DL-QRP-AG one should assume that) is the printed circuit board casing the solution for amateur projects.