June 1, 2020
Baking After Cleaning Hand Placed Parts
Is baking required after in-line cleaning an assembly with moisture sensitive parts that were hand placed instead of through an SMT machine?
May 29, 2020
Conformal Coating Recommendation
We are developing an outdoor LED module. This module will needconformal coating to prevent humidity issues and protect the circuit. The product needs a 5 year service life.
What general type of conformal coating do you suggest that offer low cost, and will meet the 5 year minimum target.
May 28, 2020
Burned Chip Repair
I have a circuit board with a burned chip. The manufacturer wants to charge an arm and a leg for a new board. Can this type or repair be done reliably? Where can I turn for guidance? Do you know anyone I can send this board to and have it done professionally?
May 27, 2020
BGA Component Grounding Problem
We have an ongoing concern regarding reliability BGA components. Over the last year, we had boards returned due to a BGA issue. The boards use leaded balls, and leaded solder. All the boards show a resistance to ground at a data point of 3K ohms. A look at "good cards" shows a resistance of 3M ohms. X-rayed extensively and no issue found.
We remove the BGA from the card, and now both the BGA as well as the board show the proper 3M ohms. Each time, after the removal of the BGA, the data point path to ground problem goes away. Essentially we somehow lost the failure signature. Can you offer guidance?
May 26, 2020
What is the IPC Definition of Uncommonly Harsh?
IPC-A-610 and other documents define class 3 to include products where "the end use environment may be uncommonly harsh."
Does anyone have guidelines for how "uncommonly harsh" may be defined?
- What temperature ranges or ramp rates are uncommonly harsh?
- What moisture/humidity/chemical types may be considered uncommonly harsh?
- Is sunlight exposure uncommonly harsh?
- Are particular levels of vibration uncommonly harsh?
May 22, 2020
EMI Shield Reflow Soldering Techniques
When reflow soldering a RF shield frame to a PCB, what techniques can be used to keep the frame perfectly aligned on its footprint?
Through hole pins can cause signal leakage, could a tooling pallet be used without significantly affecting the reflow profile?
After reflow, what effective techniques can be used to ensure consistent solder coverage around the entire perimeter of the RF shield frame?
May 21, 2020
Can a Few Contaminated Joints Cause an Assembly to Fail RoHS Compliance?
Can a few contaminated solder joints cause an entire assembly to fail RoHS compliance? Let's say I have 400 lead-free components on a board. All were processed with lead-free paste, but some of the joints were cross-contaminated with leaded solder during touch-up.
All of the reworked component joints were tested with an XRF gun. Five joint locations failed. A few were in the yellow zone (around 950ppm), the remaining were in the acceptable range. If I could calculate that the combined solder weight that I added to this assembly was below 1000ppm of lead, would it pass?
May 20, 2020
Copper Dissolution Rate
Does anyone have data on the rate of copper dissolution in solder? Have any studies been done on time/temperature and amount of copper. It's easy to claim that SnPb dissolves Cu but everybody has a different opinion on the rate and amount.
May 19, 2020
Excess Flux Residue After Hand Soldering
We observe an excessive amount of flux after hand soldering terminals using flux cored wire solder. See the image.
Is this amount of excess flux normal?
Is there something wrong with our manual soldering operation?