Posts Tagged ‘soldering’

Parts Shortage

Written by Rush PCB Inc on . Posted in PCB, PCB Manufacturing

While assembling SMT PCBs for a customer, the line unexpectedly ran out of 01005 package size resistors during the production run. This was due to an error on the customer’s part; they simply did not provide us with enough. But the customer still expected the finished product in-hand by the due date, and we did not want to disappoint him.

This, of course, created a dilemma. Should we halt production while additional parts were ordered, or simply continue? We placed a replenishment order immediately, and learned that we could not get them until the next day. We asked, “Is it possible to assemble these boards now, and add the part later when they arrive?” We also had to quickly assess the feasibility adding the part later on. How accessible is the site for this tiny part? Can it be done by a skilled soldering technician? We decided that it could.

Parts_Shortage01

An 01005 parts shortage didn’t stop production.

We proceeded to build the order with the exception of that single 01005 component. The site was accessible, we decided, so that the part could indeed be added individually to each PCB. Sure, it would take some time and hand soldering, but it would not cost us nearly as much time as if we had put the entire build on hold to wait for the parts.

Parts_Shortage02

Once the needed parts arrived, they were hand soldered onto each assembly by a skilled operator using slender soldering iron tips.

When the parts arrived the next day, we were able to employ our best hand soldering people with soldering irons equipped with special slender tips. The job went quickly and easily, and we were able to minimize downtime on the SMT line due to the unexpected component shortage, and keep this job on schedule, much to the relief of our customer. We came through for them despite their mistake, and they appreciated that.

Parts_Shortage03

The 01005 parts were easily and quickly added, and the entire job shipped by the required due date since the rest of the assembly had already been finished.

Efficient use of time, getting whatever can be done while minimizing down time, pays dividends when one is living by tight delivery schedules and expected ship dates. The more that can be achieved without unnecessary delays, the better the chances that a ship date can be honored.

 

Wicked Wicking

Written by Rush PCB Inc on . Posted in PCB Assembly and component

 

This PCB assembly challenge involved attaching a solar panel to one side of a pad using solder paste with a pass through an SMT reflow soldering oven.

Solder wicking 1

Solder wicking through the unmasked vias to the back side forms unacceptable “bumps” on top of the vias

The attachment or bond itself wasn’t the issue; but after the first trial runs, it was clear that solder wicking through the unmasked vias was going to be. Solder would wick through the unmasked vias to the back side and form “bumps” on top of the vias.

These bumps made the surface nonplanar and of course were unacceptable. It wasn’t an issue of using excess solder paste. But the “wicked wicking” had to be stopped, or at least prevented.

But how? Clearly, to keep the solder where we wanted it to remain during reflow, we had to find a way to prevent it from wicking up, collecting at the opposite ends of the vias and forming bumps. We had to find a solution that was simple, temporary, and tolerant of reflow soldering temperatures. The answer was Kapton polyimide tape, a familiar product to PCB assemblers for many years, and a material that does not degrade at reflow temperatures.

Kapton tape - molten solde

Kapton tape is applied to cover the unmasked vias; it will block the molten solder from leaking through.

Kapton tape was applied to cover the unmasked vias in order to block the molten solder from leaking through the vias to the back side during reflow. After reflow and cooling, it was a simple matter to peel off the tape. This temporary masking solution worked; there were no more solder bumps on the back side of the assembly, and the cost of the fix in terms of time and material was very low.

temporary masking solution PCB

Figure 3. This temporary masking solution worked; there are no more solder bumps on the back side of the assembly.