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  • Material Selection for High-Speed PCBs

    Material Selection for High-Speed PCBs

    Consider return loss and insertion loss – but don’t stop there.  READ MORE...

  • Characterizing Etchback and Dielectric Loss Tangent

    Characterizing Etchback and Dielectric Loss Tangent

    Fabrication-aware simulations to aid PCB design success.  READ MORE...

  • Sequential Lamination in PCB Manufacturing

    Sequential Lamination in PCB Manufacturing

    Manufacturing high-layer count boards.  READ MORE...

  • Implementing Flash Memory in PCB Design

    Implementing Flash Memory in PCB Design

    Routing flash has EMI implications.   READ MORE...

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Current Issue

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Category: Defect of the Month

Bob Willis

Soldering in nitrogen or vapor phase environments can increase the likelihood.

Subtle component lifting can be an issue to find during inspection. Most modern AOI systems should be able to detect drawbridging on small passive and active parts. Old systems may struggle with defects like the two shown in FIGURE 1.

 

 

 

 

Read more: Root Causes of Component Lifting

Details
Category: Defect of the Month

Bob Willis

Get the right stencil for the job.

This month we illustrate an example of what appears at first glance to be poor lead solderability. When examined, however, it is a combination of component and pad design.

FIGURE 1 shows the lead to be floating in the solder joint, suggesting poor wetting. When we examine the component lead and plastic body, however, the lead is not parallel, so it always sits off the pad surface, even if perfectly soldered. The lead sits in a cavity in the component body to maintain its position. But with the size of the pad used in the design and a full solder paste print, the component body will always lift.

 

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Read more: Component Body Lifting

Details
Category: Defect of the Month

Bob Willis

Is poor stencil design the culprit?

This month we illustrate solder balling and incomplete reflow when reflowing through-hole components with pin-in-paste.

Solder balling pin-in-hole reflow (PIHR) close to the body of the connector suggests poor design of the stencil for this application (FIGURE 1). There is no standoff on the corner of this part, which may have permitted the paste to be displaced when the component was attached. There should always be free space around the paste deposit to permit placement and reflow, without contacting the paste.

 

 

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Details
Category: Defect of the Month

Bob Willis

A simple in-process test for determining component wettability.

This month we illustrate solderability testing using simulation. This is basically conducting simple on-the-shop-floor solderability testing to decide whether to use old components. I use paste printed onto glass slides using the paste and stencil from production. I use the same reflow profile for the board design and components in question.

These J-leaded component terminations wet successfully with the solder paste deposits on the glass plate. The paste has reflowed up, wetting the termination on the front face of the lead (FIGURE 1). However, look at the edge and the corners of the leads. If the solder paste has not added to the original tin plating, it calls into question the coating and component age. We have recently used this test to look at the compatibility of low-temperature solders on different terminations as well.

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The Route 76

ROI 147

Board Talk 2