TRM-915-R250 datasheet(35/39 Pages) LINX

35 / 39 page

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Production Guidelines

The module is housed in a hybrid SMD package that supports hand and

automated assembly techniques. Since the modules contain discrete

components internally, the assembly procedures are critical to ensuring

the reliable function of the modules. The following procedures should be

reviewed with and practiced by all assembly personnel.

Hand Assembly

Pads located on the bottom

of the module are the primary

mounting surface (Figure 80).

Since these pads are inaccessible

during mounting, castellations

that run up the side of the module

have been provided to facilitate

solder wicking to the module’s

underside. This allows for very

quick hand soldering for prototyping and small volume production. If the

recommended pad guidelines have been followed, the pads will protrude

slightly past the edge of the module. Use a fine soldering tip to heat the

board pad and the castellation, then introduce solder to the pad at the

module’s edge. The solder will wick underneath the module, providing

reliable attachment. Tack one module corner first and then work around the

device, taking care not to exceed the times in Figure 81.

Automated Assembly

For high-volume assembly, the modules are generally auto-placed.

The modules have been designed to maintain compatibility with reflow

processing techniques; however, due to their hybrid nature, certain aspects

of the assembly process are far more critical than for other component

types. Following are brief discussions of the three primary areas where

caution must be observed.

Castellations

PCB Pads

Soldering Iron

Tip

Solder

Figure 80: Soldering Technique

Warning: Pay attention to the absolute maximum solder times.

Figure 81: Absolute Maximum Solder Times

Absolute Maximum Solder Times

Hand Solder Temperature: +225ºC for 10 seconds

Reflow Oven: +225ºC max (see Figure 82)

Reflow Temperature Profile

The single most critical stage in the automated assembly process is the

reflow stage. The reflow profile in Figure 82 should not be exceeded

because excessive temperatures or transport times during reflow will

irreparably damage the modules. Assembly personnel need to pay careful

attention to the oven’s profile to ensure that it meets the requirements

necessary to successfully reflow all components while still remaining

within the limits mandated by the modules. The figure below shows the

recommended reflow oven profile for the modules.

Shock During Reflow Transport

Since some internal module components may reflow along with the

components placed on the board being assembled, it is imperative that

the modules not be subjected to shock or vibration during the time solder

is liquid. Should a shock be applied, some internal components could be

lifted from their pads, causing the module to not function properly.

Washability

The modules are wash-resistant, but are not hermetically sealed. Linx

recommends wash-free manufacturing; however, the modules can be

subjected to a wash cycle provided that a drying time is allowed prior

to applying electrical power to the modules. The drying time should be

sufficient to allow any moisture that may have migrated into the module

to evaporate, thus eliminating the potential for shorting damage during

power-up or testing. If the wash contains contaminants, the performance

may be adversely affected, even after drying.

125°C

185°C

217°C

255°C

235°C

120

150180

210240

270300

330360

090

100

150

200

250

300

Recommended RoHS Profile

Max RoHS Profile

Recommended Non-RoHS Profile

180°C

Time (Seconds)

Figure 82: Maximum Reflow Temperature Profile

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