CA2062415C

CA2062415C - Molded optical package utilizing leadframe technology

Info

Publication number: CA2062415C
Application number: CA002062415A
Authority: CA
Inventors: Muvaffak Sabri Acarlar
Original assignee: American Telephone and Telegraph Co Inc
Current assignee: AT&T Corp
Priority date: 1991-04-25
Filing date: 1992-03-06
Publication date: 1997-08-12
Anticipated expiration: 2012-03-06
Also published as: US5123066A; EP0510859A3; JPH06252424A; EP0510859A2; KR920020699A; DE69228445T2; DE69228445D1; EP0510859B1; CA2062415A1

Abstract

An optical communication arrangement and method is disclosed which utilizes a combination of leadframe and package molding technology to reduce thecomplexity of the arrangement. In general, a leadframe is utilized for the placement and connection of the required electronic circuitry. An optical device is also coupled to the leadframe, where a subassembly may be used to house the optical device.
The electronics and optics are then simultaneously encapsulated in a molded outer package to form the final arrangement. In one embodiment, an optical subassemblyincorporating a fiber optic connector receptacle may be utilized, wherein the molded outer package is configured such that the connector receptacle remains exposed.
Alternatively, the molded outer package may be configured to include the connector receptacle.

Description

206241~
-MOLDED OPTICAL PACKAGE UTILIZING LEADFRAME TECHNOLO&Y

Back~round of the Invention Technical Field The present invention relates to ih~ vGd p~r~aging techniques for S optical co~ rætions ~ecms and, more particularly, to optical p~r~ng techniques ~ltili7ing molded l~ lf~n~. arran~e Description of the Prior Art There exist many dirrc.~l~t arr~n~,e...enl~ for p~cl~ging optical cc~...".lnir~tion ~ ng~ nl~ For example, the optical device (e.g., laser, LED or10 photorli~.) may be attached to a mount which is subse~luelltly aligned with and att~rh~l to a base nLlll~r, the base nl~lll~r utilized to f~rilit~te coupling of an optical fiber to the optical device. In most cases, the base ...- ..bcr will include a lensing element to maximiæ the optical coupling. The arr~ng~ nt of the nlvunled optical device, base .ll~mber and lens is often referred to in the art as an "optical 15 sub~ hly", or OSA. The electronics l~uil~d for OpCIa~lg the optical device (adriver circuit for a lli~n~..-;~h,- or an amplification and decision circuit for a l~ceivel, for eY~n~pl~) may then he sel)~dlely assembled (on a printed wiring board, for G~ Jlc) and co.~ d to the optical sllb~sc.--hly by con~e.-l;on~l el~trir~l leads.
Al~lllalively, the electronics may be fully enclosed in a s~ale housing, with only 20 the leads exposed for connection to the optical suba~sen~bly. An advantage of using sepalalG housings for the electronics and optics relates to the ability to inlGl~;hallge the colll~nenls as required for dirr~ app1ir~tion~ For example, a data link application may operate with TTL electronic signals, and another application (with the same optics) may utiliæ EC~ clf~ll.~nic signals. ~d-lition~11y, if either the 25 e~ ;r~l or optical portion of an arr~n~ment were to e"~l;ellce a failure, theworhng por~on could be rii~connec~d and re-used with another arr~ngem~nt A
major disadvantage of sel)alale p~e~z. ing is the overall siæ of the resultant arrangement With two separate p~k~ges, the arr~ngem~nt requires a rather large space. Further, such an arr~ngement is susceptible to electrical noise introduced by 30 the nf~eS~ ;ly long lead lengths bel~n the electronics and the optical device. The e1ectrica1 noise factor ~co---~s a signifir~nt concelll at bit rates excee~ing a2~l~x;.. ~lr,1y l0 Mb/s. Also, long leads may limit the m~xi.. -~ bit rate of either a ll~n ~- -;1 h,r or receiver, due to parasitic lead inductance (limits tr~n~mi~er) or parasitic c~c;l;1n-~es (limits lr~cei~

~ o G~ S~/~

These and other concerns have led to the development of package designs which provide for the electronics and optical device to be housed in the same unit. Many of these unitary packages are relatively expensive, as a result of using a hybrid integrated circuit (HIC) arrangement for the electronics, with an5 optical subassembly attached to the HIC. Additionally, the piece parts used in the optical subassemblies associated with these packages are often formed of machined metallic components, adding to the cost of the system. Fabrication problems may also exist with respect to mating the various piece parts (i.e., outer housing, optical subassembly and HIC). Lastly, in many instances, the packaging processes for a 10 transmitter and receiver are often very distinct, leading to manufacturing problems and increasing the overall expense of the packaged system.
An improved package designed is disclosed in U.S. Patent 4,911,519 issued to W.H. Burton et al. on March 27, 1990. In the disclosed arrangement, the HIC of a conventional package is replaced by a conventional 16-pin dual-in-line 15 package (DIP) which includes a specialized pair of end prong leads for attachment to the optical subassembly (OSA). The DIP and optical subassembly are subsequently assembled within a plastic molded package frame. The plastic molded frame is configured to include a molded optical connector receptacle for subsequent attachment of a connectorized optical fiber. The arrangement is subsequently 20 covered with a metallic lid which is grounded to the package floor. A significant savings is realized by the utilization of the DIP, as well as utilizing a molded plastic piece part for the frame/connector assembly.
Although the Burton et al. arrangement is considered to be a significant advance over the prior art, the need remains to further simplify optical 25 packaging techniques, with respect to limiting the number of separate assembly operations, in light of rapidly growing markets which will require many thousands of such devices in as a cost competitive arrangement as possible.
Summary of the Invention The need remaining in the prior art is addressed by the present 30 invention which relates to optical packaging techniques and, more particularly to the utilization of transfer molded leadframe-based packages.

~ ~ o~ ~/s --2a-In accordance with one aspect of the invention there is provided an optical communication arrangement comprising: at least one active semiconductor optical device; electronic circuitry for operating said at least one optical device; a leadframe section to which both the optical device and the electronic circuitry are 5 affixed; and molded outer packaging disposed so as to encapsulate both said electronic circuitry and said at least one optical device.
In an exemplary embodiment of the present invention, a leadframe section is utilized for placement and attachment of electronic circuitry required for the operation of an associated optical device (e.g., a driver circuit for an optical 10 transmitter and/or amplifier-decision circuit for an optical receiver). The semiconductor optical device is coupled to the leadframe and the associated ~, ,~,,,t, - ~ 2062~1S

el~hunics. The optics and cl~lluilics are subse~luenlly enca~ ted by a suitable m~t~ri~l (e.g., plastic) using mol-lin~ techniques.
An exemplary arrangom. nt of the present invendon may utiliæ an optical device (and lensing ele~ .l(s), if l~uilcd) inserted within a con~el-lion~l S opdcal subasse~bly (OSA), where the OSA is conl-r~lr~l by electric~l leads to the leadframe. The cle~hunics and OSA are subs~u~nll~ en~ al~ul~te~l using mnl-ling t~hniques to form the final ~ ag~ The m~l1ing operation is ~lrû~ ed so as to create a conn~ lcc~cle as a unitary ..~ ker of the outer ~ fage housing.
In an alt ..~ embo liment of the present invention, the above-10 ~les~ l OSA is replaced by the direct att~ilm~nt of an optical device (forexample, a lensed LED) to the leadframe. In particular, the lea~lrlalllc is configured to include a paddle-like lead for attachment of a first major surface of the optical device. Dc~l--li--g upon the type and plarement of the optical device, the paddle may be ~lesi~e~ to include an a~.lulc aligned with the active region of the optical 15 device so as to allow for the passage of an optical signal ~ .~lllluugh. A second lead is coupled to the o~pOSillg major surface of the optdcal device to provide the g ele~ 1 col-l-e~;l;on A base nlclllber is attached to the le~lrl~ in ali~mP.nt with the leadframe a~llUlc and utilized to facilitate the coupling of an optical fiber to the optical device. The base ...~ ..~r may include a coupling lens and 20 be confi~lred to provide a connectnr l~,c~cle, utilized to provide the physical Al l ~Cl~lr~ t of a cQnnectc riye~l optical fiber to the p~clrage. .Altern~tively, a con~ ;on~l optical base .. her may be utilized and the outer package molded to include the CO~ CCI~Il lccep~cle, as described above.
In yet another embol1imtont of the present invention, a convenfis)n~l OSA
25 base .. ~r is replaced by a piece part which comprises both a base .. e .. ~. and C~?l-l~eCt~l l~p~cle. For this emboflim~nt, the moldin~ of the outer p~c~ge is simr1ifie~ since there is no need to mold a receptacle feature.
Brief De~cription of the Drawin~
l~ef~nn~ now to the drawings, where like numerals l~ple~llt like parts 30 in several views:
FIG. 1 illu~ tes an exemplary leadframe arran~,m~.nt suitable f~r use in ~oci~tion with the t~ ^hing~ of the present invention;
FIG. 2 illustrates a portion of the leadframe of FIG. 1 illu,.ll~ling in particular the att~hment thereto of the requisite electronic c~uill ~ and associated 35 optical suk~sc...hly;

- ~ 206241~

F~G. 3 illu~ at~s a portion of an alternative lea,lll~ulle arrangem~nt particularly suited for an elllw~ 1 of the present invention ~vhc~lll the optical device is dil~lly attached to the leadframe and a scpalate base member (which may cQmrri~ç a co~ ,~pl~lG) is aligned to the attr-hed optical device;
S FIG. 4 illui~t~ates a cut-away side view of an eYemrl-q-ry molded pq~ltq.
in~1u-1in~ the electronics and optics as illui,halt;d in FIG. 3;
FIG. S illu~ at~s a partial cut-away view in ~li-,~live of the pac~-of FIG. 4;
FIG. 6 illuslla~s a cut-away side view of an q1ternq~ive molded pac~q-~
10 utili7ing a single piece part base lll~lll~r-c~ nlle~ c~cle; and FIG. 7 illu~ ates a partial cut-away view in ~li-,~;live of a molded ,l p ^~qge for use with a pair of opto-electronic assemblies, the qlT.qn~m.ont of FIG. 7 utili7ing a pair of base ~r,~bcl col-l-~lQr-receptacle piece parts as illusllated in FIG. 6.
15 Detailed Description Referring to FIG. 1, an eYempl-q-ry lc~Ç.~ e 10 is illustrated which cludes a large nu ll~r of severable leadframe sectiQnc for use with a nw~r of ~p~ ,te opto cl~;llonic p~g~s It is an advantage of the present invention that the use of a leadframe structure allows for the cimllltptlpous f~bric~tion of a large 20 num~l of opto-electronic pac~g~s, such as tr~n~-n;ll~ " receivers or ~ ,nSCei~ 7.
Similar to con~,ntional elccllonic integrated circuit ploces~;--g, a plurality of intc~alt;d circuits may be simlllt~ne~usly ~tt~ ~h~A. and wirebonded along locations 12 of le~lllallle 10. In accol~lce with the te~chings of the present invention, an associatedplurality of optical devices are coupled to lP~.lr.i..,-e 10 at locations 12 25 and the combina~ion of electronics and optics en~rsul~t~ using a mol-ling process (e.g., I ~Isrer molling) as described in det~il below, to form the final p~e~ag~A
--bly (as ind~ ted by the dotted p~rL-z~,~ outline M). When the mnlding operation is comrl~t~l, leadframe 10 may be severed along dotted lines 14 to form a plurality of final p~ ~ assemblies. The l~ ining figures illustrate a single 30 leadframe section and the various items associated therewith. It is to be understood that the illustration of a single leadrlallle section is only for the sake of 11;ccl~s~ n and in general a larger nulll~r of opto-el~11~nic assemblies are cim~ neously formed in l~lv~-l;on.
A single leadframe section 20 is particularly illustrated in FIG. 2.
35 Secdon 20 includes a central ground plane paddle 22 to which an integrated circuit 24 is ~ h~A Int~ ~aled circuit 24 is ~ubse~luelllly coupled, using wirebonds, for - 1_ 2062415 eY" 1~ to sçlec~ leads 26 of leadframe section 20. A s~ala~ cap~cilive elelllellt 28, which may be l~uired for certain l~i~er configurations, is att h~ to leadframe section 20 as shown in FIG. 2. An optical sub~sçmhly (OSA) 30 (shown in an cxr~ ed view in FIG. 2), ii~rludes an optical device 32 suppulLcd on a mount 5 33 inclu-ling clec1~;c~l leads 31 and, possibly, a lensing elen~nt 34 which ise.~-b~ded within a base ,.. he.r 36, where base ."f .~her 36 may compri~e a m~t~.ri~l co-np~;hle with the molded housing of the outer package (e.g., liquid crystal polyn~l." molded plastic, .~ hine~ plastic, or .r.~rhined metal). FlPctric~ql leads 31 of OSA 30 are then attached to leadframe section 20, using, for example, a 10 pair of end prong leads 37,38 located at one end 39 of leadframe section 20. As shown in FIG. 2, end prong leads 37,38 may be bent upn a,~ls at an angle of al)pl~,~llal~ly 90 with respect to the plane of leadframe 20 so as to acco~ o~l~t~
the 5~ l;on of the desired optical con~ ;on (not shown). ~ltçrn~tively, leads 31of OSA 30 may be bent d~wllw~l, with end prong leads 37,38 ~ in the 15 plane of leadframe 20. As will be desçribed in detail below, the combination as illu~hated in PIG. 2 is subs~u~,nlly encapsulated using a mol-ling operation to form the final ~ ?cl~a~ assembly.
PIG. 3 i~ llale,S an ~ltrrn~tive aIr~ngemPnt which may also be e~r~r~ t~d to form an opto-electronic p~c~ge in acc~ ce with the te~ching~ of 20 the present invention. The electronic integrated circuit portion 24 is identical to that described above in ~soci~tion with FIG. 2. In contrast, however, optical device 32 is directly IllOUnt~l on a le~f~m~ section 21, without any se~ e optical s~b~çmhly housing In particular, optical device 32 is mounted on a leadllàllle paddle 40 formed as a portion of leadframe section 21. As shown, paddle 40 may be 25 formed to include an apc,lul~, 42 to allow the passage of an optical signal lhluugh (~ ,ly, device 32 may be ..ounleA on the opposite side of paddle 40 such that the emithng (or ~eceiving) surface of device 32 is unobstructed).
The l~ ini,~g co,-n~.~l;on to optical device 32 is supplied by a lead 44 formed ent to paddle 40. An advantage of this embodiment is the ability to simplify the30 assembly process related to the place.~ l and attachment of the electronics and optics. In particular, the pl ~semf nt of integrated circuit 24 and optical device 32 along the same physical plane (i.e., the plane of leadframe 21) allows for the ~llo..-~ &l~cl~l~nt operations to be pe,rulllled sim~lltanf~ously for both the electronics and optics. Subs~uenl to the optical device ~tt~k.l.el-t, base ...f n~ l 46 35 may be ~ttnchfl1 to the back side of leads 40 and 44, as shown in FIG. 3, to form the coupling optics. The portion of the leadframe holding optical device 32 with the ~tt~hed base Illt,.~ 46 may then be bent up~ ds 90 to take the form shown in FIG. 4.
A final p.~AL'S'g~d version of the arr~ngf~n~nt of FIG. 3 is illu~ ttd, in a cut-away side view, in FIG. 4. A similar ~ a^L'~ge would be formed for the S arrang~ of FIG. 2. As shown, a molded outer par~ e 50 is formed so as to completely en~ulate both electronics 24 and optics 32 (inclu-ling base ..~.-.1~,.
46, or OSA 30 of the FIG. 2 e~ lt ~l). Rear portion R of p~ gt~ 50 coTnrri~es a body which may al)p~ , for e~a~ ,le, the size and shape of a con~ ;Qn~l 16-pin dual-in-line p~ ge (DIP). Other confi~rations may be 10 utili7Yl However, conrolmillg to the standardized p. AL-51gf' design has been found to simplify the design of the nu-kling tool, as well as trim-and-form tools, since rear por~on R conrol.lls to i.-~. ..~I;on~ in~ standards. More i~ ly, the useof a co~ -l;on~ ge design allows for ~u~o...~l~d machinery (e.g., pick-and-place) to be used in the subs~uenl assembly of the ~ g~. on a printed circuit 15 board or the like. rOI~. ald portion F of p~ ge 50 is shown to flare upward to ~Aco------n~te the ~ nsion~ of base --c---hel 46. As will be di~ ' se~l in detail h~ lart~ p ^~a~ 50 may be molded to include a connectQr receptacle 52 as part of the final P~AL 1,~.
As m. ntion~ above, an e~e.ll~ mol-ling ~chni~lue which may be 20 used to form paA~ 50 is "~.~r~. mol 1ing, as used in con~enlional integrated circuit p~ ~ing In ~ r~. m~l-ling, a pl~hc~ed charge of thermoset molding colll~ound is moved from a dielectric pl~,hcat~ . into the mold cavity through a single inlet port. Transfer mol-ling, as is well-known, is best suited for the type of insert mnl1ing l~uih~d in this embodiment of the present invention, where it is desired to 25 precisely form a connector receptacle which is aligned with an intern~l optical base .--e...~,. . During the mnlflin~ process, lcadrlallle 21 (i.e., leads 26) is cl~mped in place tO hold the colll~n~nls as stationary as possible. Base .~.. hf ~ 46 is further held in place by a retractable pin 54 which pl~t;n~ motion of base lllC ~hCI 46 towards circuit 24. A mandrel 56 is utilized to create inner bore 58 of receptacle 52.
30 Mandrel 56 also holds base --~ 46 st~tion~ry and css~ ially p~ ts the Il..,...~OSCI m~ l from entering base ,..~ 46 during the mnlding operation. Pin 54 may retract once the mold cavity is filled so that r1~1ition~l m~teri~l will be able to flow into the void.
FIG. S illustrates a partial cut-away view in perspective of an exemplary 35 package formed in accor~ ce with the description of FIG. 4. Illu~ ed clearly in this view is connt~;lol receptacle 52, formed as part of pa~ 51~ 50 during the ~ 2062415 .

D!cling process. For the particular arrqngpmpnt of FIG. 5, p~qge 50 is formed soas to allow leads 26 to exit through sidewalls 62,63 of package 50.
As n~nti~nPA above, acon~ ;Qnsl optical sub~se-nbly such as OSA
30 of FIG. 2 may be rep1~ - e ~ by a combination OSA and co~ ol receptacle.
5 ,~lte~qtively, a con~ ;ol~l base ..~ ...~- such as ..~ ...~r 46 of FIG. 3 may be replaced by a c(smbilldlion base l~l-lber and co~ P~Io- l~c~k~cle. The use of such a colllbill~d piece part, in either arr.qn$ement, allows for a simpler mold to be utili7~d FIG. 6 c~nl~ a cut-away side view of an e~e.~ qge 70 illu~lldlillg in particular a combination OSA-l~cel,~cle 72 (or ql~..~;vt;ly, a combination base 10 ..~,...~I-receptacle, if using the FIG. 3 e.llbodi~ t). As with the arrqng~
Ged above, package 70 also cnmrri~es a lP ~frqme 20 with integrated circuit 24. During the mol~ing operation, leadframe 20 and OSA~ ~cle 72 may be cl~ ~ in place to remain motionlPss. The clamping of receptacle 72 thus limits lllo.~,.l~nt of the OSA portion during moltling and may eli...;n~r, the need for a 15 separate retractable pin. As m~nti~n~d, the mold for this particular embodiment is simpler that that associated with the above-described e.llbodi llelll of FIG. 4, since there is no longer the need to mold a conl~ o, receptacle. Th~cÇol~" various other mo'1ing ~,çhnologies~ inclu(ling but not limited to, c(jlll~ ssiol mnl-lin~ or injection mr'1ing (as well as Ll~ls~r mrl1in~) may be used to form the outer pac~. A
20 ~ l 74 may be inserted through OSA-receptacle 72 and used to further reduce the lL~elihood of motion of the co..lp~,llents during the mol~ing operation.
FIG. 7 ill~ .t~s an al~ alivc arr~ngement 80 of the present invention where a pair of optical devices and associated electronics are housed within a single outer pa~ e 82. The pair of optical devices may comprice an optical trans~..ill;ng 25 device and optical l~,ce;villg device, thus forming an optical transceiver.
~ltl . --hli~ly, the pair of devices may comprise a pair of optical lla..~...illin~ dcvices (for use in a sparing arrang~ment or as a dual-wavelength tr~nsmitttor, for eY~mrle) or a pair of optical l~,ccivillg devices. For the embo 1im~nt of FIG. 7, an arr~ngem~nt such as ~ cscd above in association with FIG. 3 is utilizcd where the optical 30 devices are directly att~r-h~l to the leadframe. Further, arrangement 80 comprises a piece part 84 inclll-ling a co..lhil-~lion of a base me.llber and conneclv~ lece~cle, as ~es~ibed hereinabove in ~sociation with FIG. 6. The co. ..bin~t;- n of the base .n~....~el and col-l-~ . receptacle thus simplifies the mol-ling design of p~c~ge 82 as rliscu~ced above. A plurality of leads 86, suitable for surface-mount a~ h...e 35 is illu~ ated as exiting through sidewall 85 of arr~n~m~nt 80. ~ lition~lly~
arr~ng~m~nt 80 is illustrated as in~ lding a met~llic coating 88 which is disposed - .- 2062~1~

over outer p~ g~ 82. Metallic coating 88 is utiliæd to provide, where nee~le~
EMI shielding for the co..~l onell~ con~in~ within par~ 82.

Claims

1. An optical communication arrangement comprising:
at least one active semiconductor optical device;
electronic circuitry for operating said at least one optical device;
a leadframe section to which both the optical device and the electronic circuitry are affixed;
and molded outer packaging disposed so as to encapsulate both said electronic circuitry and said at least one optical device.

2. An optical communication arrangement as defined in claim 1 wherein the arrangement further comprises receptacle means for facilitating attachment of an optical fiber to said arrangement.

3. An optical communication arrangement as defined in claim 2 wherein the outer packaging is molded to include the receptacle means.

4. An optical communication arrangement as defined in claim 3 wherein the arrangement further comprises a base member embedded within the package and aligned with the optical device for providing coupling of an opticalfiber to said optical device.

5. An optical communication arrangement as defined in claim 4 wherein the base member includes a lensing element aligned with the optical device.

6. An optical communication arrangement as defined in claim 3 wherein the optical device is directly attached and electrically coupled to the leadframe section.

7. An optical communication arrangement as defined in claim 2 wherein the arrangement further comprises a base member aligned with the optical device and formed to include the receptacle means, the outer packaging molded so as to allow the receptacle portion of the base member to remain exposed.

8. An optical communication arrangement as defined in claim 7 wherein the base member further includes a lensing element aligned with the optical device.

9. An optical communication arrangement as defined in claim 2 wherein the arrangement further comprises mounting means for supporting the optical device wherein the optical device is electrically coupled to the leadframe section.

10. An optical communication arrangement as defined in claim 1 wherein the arrangement further comprises a metallic coating disposed over the molded outer packaging.

11. An optical communication arrangement as defined in claim 1 wherein the at least one active semiconductor optical device comprises an optical transmitting device; and the electronic circuitry comprises a transmitting driver circuit, the arrangement forming an optical transmitter.

12. An optical communication arrangement as defined in claim 1 wherein the at least one active semiconductor optical device comprises an optical receiving device; and the electronic circuitry comprises an amplifier-decision circuit, the arrangement forming an optical receiver.

13. An optical communication arrangement as defined in claim 1 wherein the at least one active semiconductor optical device comprises a pair ofoptical devices.

14. An optical communication arrangement as defined in claim 13 wherein the pair of optical devices comprises a transmitting device and a receiving device so as to form an optical transceiver arrangement.

15. An optical communication arrangement as defined in claim 11 wherein the pair of optical devices comprises a pair of optical transmitting devices.

16. An optical communication arrangement as defined in claim 11 wherein the pair of optical devices comprises a pair of optical receiving devices.

17. An optical communication arrangement as defined in claim 1 wherein the outer molded outer packaging comprises a molded plastic material.

18. An optical communication arrangement as defined in claim 17 wherein the molded plastic material comprises a thermoset transfer molded plastic material.

19. An optical communication arrangement as defined in claim 1 wherein the portion of the leadframe to which the optical device is affixed is bent at an angle of approximately 90 degrees with respect to the plane of the leadframe.