Questions tagged [pcb-assembly]

The process of mounting electronic components onto a printed circuit board. This can be done manually with a soldering iron, or automatically using a "Pick and Place" machine.

Sometimes an assembled board will be referred to as a PCA, a Printed Circuit Assembly.

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Securing electrical cables to holes in enclosures?

Suppose I would like to insert data-cables of varying diameters -- e.g., a cable of 5 mm diameter -- into the 6 mm diameter hole of a plastic enclosure. The wires within the cable are terminated via soldering to a PCB inside the enclosure. What…
OrCa
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Why did Axial Capacitors Fall Out of Use in the Industry?

When inspecting the boards from electronics made in 1980s and earlier, one distinct feature is the extensive use of axial, electrolytic capacitors as power supply filter. Axial ceramic decoupling capacitors were used as well, to a lesser extent. For…
比尔盖子
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Do dead weight 'components' exist?

After making a prototype circuit board, I usually glue four rubber pads/bumpers to the bottom, to keep it stable on my desk: Unfortunately, my boards are usually too light . When connected to a few cables, they float around to wherever they're…
K.Mulier
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Why does a commercial PCB need this much rework?

I found a PCB that has had some rework done. When I saw it, I thought that someone had actually repaired it after purchase:- It's got additional wiring (white & brown) and under the hot glue are two ceramic capacitors. The capacitors have been…
Paul Uszak
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Why do resistors still use color coding?

I always wondered why color coding is still used on resistors in 2014. Here is Wikipedia's word on the original reason why : Colorbands were commonly used (especially on resistors) because they were easily printed on tiny components, decreasing…
DylanM
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SMD soldering: tiny components stick to tweezer point

When soldering SMD components, the 2-pinned ones (like resistors, capacitors, ...) are the hardest in my opinion. I started long time ago with the 1206 format. Then scaled down to 0804, 0603 and finally I'm working with the 0402 ones. I'm facing a…
K.Mulier
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Should I worry about the risk of tombstoning?

A colleague has (apparently unsuccessfully :-)) tried to convince me of the risk of tombstoning in the following situation: He claims pad 1 for R55 and R59 will lose heat faster during soldering because they have two traces leaving, while pad 2 only…
stevenvh
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Which of these marks signifies Pin 1 on the STM32F (LQFP64)?

I'm using the STM32F105, in a LQFP64 package. It has two circular markings, on opposing corners of the IC. This picture is for a different ST ARM, but the markings and silkscreen are similar: The larger mark in the upper-right of the picture has a…
bitsmack
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How do I solder headers so that they always stand straight up?

When soldering headers, usually single and double pins, I flip the board over so the pin rests on the surface and then solder them. They never come out straight. It would be great if someone has figured out how to do this correctly?
Bill
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How do you attack a new board?

You get your PCB back from the manufacturer. It is a new design, you have of course bread-boarded all the major parts, but you know there are going to be problems. There are just too many things that can cause problems, e.g.: Errors in the schematic…
morten
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Why use kapton tape?

I have noticed a lot of electronics use kapton tape in places where a heat resistant tape isn't necessary. Why is that so? Is it just because it's a good adhesive?
Artichoke
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Why are there no BGA chips with triangular tessellation of circular pads (a "hexagonal grid")?

Ball grid arrays are advantageous integrated circuit packages when a high interconnect density and/or low parasitic inductance is paramount. However, they all use a rectangular grid. A triangular tiling would allow π⁄√12 or 90.69% of the footprint…
jms
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How to secure cables to a PCB

What is a good way to secure cables to a PCB? There are some good advice in the following post, but the application is slightly different: Securing electrical cables to holes in enclosures? In this case, the strain-relief/securing of the cables will…
K0ICHI
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What initial orientation do pick&place machines use when applying the "rotation angle"?

PCB assemblers require a file describing the component identifiers, the X and Y coordinates of the centre, and the rotation angle. I generate that file automatically from my CAD package (DesignSpark PCB). However the rotation angle that is generated…
Mister Mystère
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What are the 'knuckles' on through-hole LEDs and photodiodes for?

I am using an IR LED and a photo diode, and I have designed the PCB according to the specifications that I found on the datasheet - i.e. hole sizes for the pins being 0.6 mm. However, on these components there are 'knuckles' (see below image) and…
MrPhooky
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