Steps to test and assemble PCB

Question

I have a project that required for me to assemble and test a PCB. I need some help for how I start and the steps to do everything. Now I do have a multimeter and I have the parts with the PCB.

This should be a long list of what I will test before I assemble the boards, what I will test during assembly, and what I will test after assembly. For example resistors, capacitors, amplifiers, open and short circuits...

Three examples are:

Resistance between +15V and -15 V prior to assembly (expected value is infinity)

Dc voltage at output of input stage when the inputs are grounded. (what is the expected value)

Current draw of the circuit (what is the expected value)

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Thank you for your answers. I need something like easy steps to do that. I have to like start with look at the PCB and double check it, and then see if there’s a short circuit, and then try to double check the source etc. After that start soldering. And check the board after I finish to see if I got the results that I need. I want steps like this, but I need someone who can make it clear for me. With some sort of chart, with steps that I need to check. Thank you.

For example:

Answer 1

Generally speaking:

Typically there isn't any testing required before you start the assembly. Unless you have used the lowest cost back alley PCB manufacturer the manufactured board has been tested to match the Gerber files.
Same with the components. Components out of the box (from a reputed distributor) will work every time. Faulty components are extremely rare.

There are peripheral test though, like calibrating the solder equipment. IPC standards goes into much detail here.

After the board is assembled you should have a specification. What is the minimum and maximum input voltage? How much current should it consume? what voltages should be at various test-points. What I/O should be generated? That list is extremely specific for your board. It is impossible for us to know.

Answer 2

This question is a bit too wide.

Personally, when I perform the first power-up of a design, I start by a visual check of the board, check everything is soldered, check for cold solder joints or joints without enough solder, components at the correct location, component polarity, check for solder bridge and I also check for defects in the PCB, especially via, traces. A microscope is really helpful.

I will especially check the soldering quality on connectors that are on large boards.

Bad soldering can induce tricky faults that come and goes, it is especially annoying in a new design, so need to make sure it's properly reflowed using a microscope.

Then check for potential shorts between the voltage rails and the grounds using a multimeter.

Then I take an adjustable power supply and I slowly increase the voltage while monitoring the current. At the same time, I sometimes use an IR camera to check any potential heat spot that would be a fault. I also check for potential smoke :p.

If everything goes fine, I go up to the nominal voltage while checking the different rails if there are regulators. I also check that there is no IC heating up, which sometimes happens if there is a mistake in the connections.

Once this is done, I go on and check the different parts of the circuit, analogic, digital, etc...

Of course, it depends a lot on what is the circuit, you won't go about the same way for a 5V USB-powered device as a 230VAC high power board.

It also depends on the board complexity and cost, for a simple cheap board I'd just connect it and check for hotspots, for a complex expensive board I'll go slower.

Also when doing SMT, I usually make more than one board, this has the advantage to have a spare if you burn one, but also helps if you have any fault to differentiate between design issue or SMT issue, if they all have the same issue then it's probably design, if they have different issues then it can be SMT mistake.

When doing low series SMT, it's more common to have issues like wrong component placement or polarity as low series of a few boards are usually done by hand. In practice, 30-50% of hand SMT will have some sort of mistake, either placement, polarity, or soldering if there are a lot of components.

If SMT is done by a machine, if the factory has a good ERP system it's usually rare, or at least it will be the same everywhere.

Answer 3

First do an optical check of unassembled PCB, look for shorts or breaked traces. Then start with assembling power supplies, measure the output voltages, at unloaded outputs the voltage can varry. Then try to load them in range you are going to use it (little more). After that start with assembling stage by stage (pasive components first). After every stage do a functional test for all possible states. Use a signal generator/power supply if current stage requires some inputs from stage not assembled yet instead. If everything is fine do a precise settings/testing, full load test in whole range it is going to be used and other tests depends on device type(temperature, humidity, etc..)

Answer 4

Using diode mode on multimeter is very decent way to check all the tracks and see if they are connected as they should and is track opened where it should be. Also it is a good way to find shorts on the board. When i was working on mobile phones it was the best way for me to test and find problems on the mobos. You can see more by googling and checking this topic here: Using diode mode on my multimeter to debug circuits. A good idea?